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Conveyor Tracking
Art.nr 3HAC 5750-1
CONTENTS Page 1 Introduction ......................................................................................................................5 2 Overview of Conveyor Tracking.....................................................................................5 2.1 Physical Components ............................................................................................. 6 2.2 Features................................................................................................................... 6 2.3 Limitations.............................................................................................................. 8 3 Principles of Conveyor Tracking in S4C........................................................................9 3.1 Start Window and Queue Tracking Distance.......................................................... 10 3.2 Coordinate Systems ................................................................................................ 12 4 Programming Conveyor Tracking..................................................................................13 4.1 Working with the Object Queue ............................................................................. 13 4.2 Activating the Conveyor......................................................................................... 14 4.3 Defining a Conveyor Coordinated Work Object .................................................... 14 4.4 Waiting for a Work Object...................................................................................... 15 4.5 Programming the Conveyor Coordinated Motion .................................................. 15 4.6 Dropping a Work Object......................................................................................... 16 4.7 Entering and Exiting Conveyor Tracking Motion in Corner Zones ....................... 16 4.8 Information on Teach Pendant................................................................................ 17 4.9 Programming Considerations ................................................................................. 17 4.10 Finepoint Programming........................................................................................ 18 4.11 Modes of Operation .............................................................................................. 18 5 RAPID Instructions .........................................................................................................20 5 WaitWObj - Wait for Work Object on Conveyor .........................................................20 5 5 5 5
Example ..................................................................................................................... 20 Arguments ................................................................................................................. 20 Program execution..................................................................................................... 20 Examples ................................................................................................................... 20
5 Limitations................................................................................................................. 21 5 Error handling............................................................................................................ 21 5 Syntax ........................................................................................................................ 21 5 DropWObj - Drop Work Object on Conveyor..............................................................22 5 5 5 5 5
Example ..................................................................................................................... 22 Arguments ................................................................................................................. 22 Program execution..................................................................................................... 22 Limitations................................................................................................................. 22 Syntax ........................................................................................................................ 22
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6 Additional Features for the DSQC 354 Revision 2 ....................................................... 23 7 Hardware Configuration and Connections ................................................................... 23 7.1 7.2 7.3 7.4 7.5
Encoder Type Selection.......................................................................................... Encoder Location ................................................................................................... Encoder Connection to DSQC 354 ........................................................................ Synchronization Switch.......................................................................................... Connecting the DSQC 354 to the S4C Cabinet......................................................
24 25 25 25 26
8 Software Installation........................................................................................................ 27 8.1 Installation of 2 Conveyors .................................................................................... 28 9 Conveyor Setup and Calibration .................................................................................... 28 9.1 Direction of Positive Motion from Encoder........................................................... 28 9.2 Calibration of Counts per Meter............................................................................. 29 9.3 Defining the Queue Tracking Distance .................................................................. 30 9.4 Conveyor Base Frame Calibration ......................................................................... 9.5 Conveyor Start Window and Sync Separation ....................................................... 9.6 Conveyor Maximum and Minimum Distances ...................................................... 9.7 Robot Adjustment Speed........................................................................................ 9.8 Motion System Parameters..................................................................................... 9.9 Motion Mechanical Unit Parameters...................................................................... 9.10 Configuration for Track Motion following Conveyor..........................................
30 34 35 35 36 37 37
10 Circular Conveyor Tracking......................................................................................... 39 10.1 Encoder Type Selection and Location.................................................................. 10.2 Software Installation............................................................................................. 10.3 Direction of Positive Motion from Encoder......................................................... 10.4 Calibration of Counts per Meter........................................................................... 10.5 Defining the Queue Tracking Distance ................................................................ 10.6 Circular Conveyor Base Frame Calibration - Manual Method ............................ 10.7 Circular Conveyor Base Frame Calibration - TCP Measurement Method .......... 10.8 Conveyor Start Window and Sync Separation ..................................................... 10.9 Conveyor Maximum and Minimum Distances .................................................... 10.10 Conveyor Adjustment Speed.............................................................................. 10.11 Motion System Parameters................................................................................. 10.12 Motion Mechanical Unit Parameters.................................................................. 10.13 Motion Transmission and Single Type...............................................................
39 40 40 40 40 41 42 44 45 45 45 45 45
11 Conveyor Tracking System Parameters....................................................................... 46 11.1 Topic: I/O Signals Topic....................................................................................... 46
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11.2 Topic: Process ....................................................................................................... 47 11.3 Topic: Manipulator ............................................................................................... 48
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Conveyor Tracking
Introduction
1 Introduction This document contains a description of the Conveyor Tracking functionality for S4C. Conveyor Tracking, or Line Tracking, is the function whereby the robot follows a work object which is mounted on a moving conveyor. This document describes how a conveyor tracking application is installed, programmed, and operated. The document is organised as follows: Section 2 presents an overview of the conveyor tracking features and necessary physical components. Section 3 describes the principles of conveyor tracking in S4C, the coordinate systems, and object queues. Section 4 provides information on how conveyor tracking is to be programmed. Section 5 presents the new RAPID instructions. Section 6 describes the features available with the Revision 2 of the DSQC 354. Sections 7 and 8 present information on the hardware requirements and software installation. Section 9 goes through the configuration and calibration of a linear conveyor. Section 10 marks the differences for configuration and calibration of a circular conveyor. Finally, a complete listing of all conveyor system parameters is provided in Section 11 . Follow Section 9 Conveyor Setup and Calibration for the steps in configuring a standard linear conveyor.
2 Overview of Conveyor Tracking In conveyor tracking, the robot’s Tool Centre Point (TCP) will automatically follow a work object that is defined on the moving conveyor. While tracking the conveyor the S4C will maintain the programmed TCP speed relative to the work object even if the conveyor runs at different speeds.
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2.1 Physical Components Sync Switch Conveyor Encoder
Encoder Unit DSQC 354
IRB robot S4C Controller Figure 1 Physical Components in Conveyor Tracking
The S4C solution for conveyor tracking consists of the following components: S4C Controller and IRB robot 24V Encoder Option 285, DSQC 354 Encoder Interface Unit, Original or Revision 2. Synchronization Switch, indicating object presence on conveyor Conveyor The encoder and synchronization switch are connected to the DSQC 354. One encoder can be connected to several Encoder Interface Units but each S4C controller must have a DSQC 354 if more than one robot is to track the conveyor.
2.2 Features The S4C conveyor tracking option provides the following features: Accuracy: In Auto operation, at 150 mm/s constant conveyor speed, the Tool Centre Point (TCP) of the robot will stay within +/- 2 mm of the path as seen with no conveyor motion. This is valid as long as the robot is within its dynamic limits with the added conveyor motion. This figure depends upon the calibration of the robot and conveyor and is applicable for linear conveyor tracking only. Object Queue: The DSQC 354 Encoder Interface Unit will maintain a queue of up to 254 objects that have passed the synchronization switch.
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Overview of Conveyor Tracking
Start Window: A program can choose to wait for an object that is within a window past the normal starting point, or wait for an object to pass a specific distance, or immediately take the first object in the object tracking queue. Objects that go beyond the start window are automatically skipped. RAPID Access to Queue and Conveyor Data: A RAPID program has access to the number of objects in the object queue, and the current position and speed of the conveyor. A RAPID program may also remove the first object in the tracking queue or all objects in the queue. Maximum Distance: A maximum tracking distance may be specified to stop the robot from tracking outside of the working or safety area. Track follows Conveyor If the robot is mounted on a linear track, then the system can be configured such that the track will follow the conveyor and maintain the relative position to the conveyor. The TCP speed relative the work object on the conveyor will still be the programmed speed. Enter and Exit Conveyor Tracking in Corner Zones It is possible to enter and exit conveyor tracking via corner zones as well as via fine points. Using corner zones allows a minimum cycle time to be achieved. Exit and Re-enter Conveyor Tracking to Same Object It is possible to exit and re-enter to the same object on the conveyor unlimited times until the object moves outside the working area, reaches the maximum distance, or is explicitly dropped by the RAPID program. Multiple Conveyors Up to 2 conveyors are supported via the standard option. Each conveyor must have a DSQC 354. Coordinated Finepoint A finepoint may be programmed while making motions relative to the conveyor. This conveyor coordinated finepoint will ensure that the robot stops moving relative to the conveyor and will follow the conveyor while the RAPID program continues execution. The robot will hold the position within +/- 0.7 mm depending upon calibration of the robot and conveyor. Calibration of Linear Conveyors A calibration method is provided for easy calibration of the position and direction of the conveyor motion in the robot’s workspace. The linear conveyor may take any position and orientation. Conveyor Tracking
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Conveyor Tracking
2.3 Limitations Small Orientation Error with SingArea\Wrist There can be a small orientation error of the TCP while following the conveyor and make long motions with SingArea\Wrist. This error can be eliminated by making several short motions with SingArea\Wrist. Track Parallel to Conveyor If the robot is mounted on a track and the track is to be used to follow the conveyor motions, then the track and conveyor must be parallel. The motion on the track and the motion on the conveyor must have the same direction of positive motion. See Section 9.10 Configuration for Track Motion following Conveyor. Calibration of Circular Conveyors There are no built-in methods for the calibration of circular conveyors. This limitation can be relaxed if the user is willing to calculate a quaternion orientation manually or with other tools during base frame calibration. Limitation on External Axes Each conveyor is considered an external axis. Thus the system limitation of 6 active external axes must be reduced by the number of active and installed conveyors. The first installed conveyor will use measurement node 6 and the second conveyor will use measurement node 5. These measurement nodes are not available for external axes and no resolvers should be connected to these nodes on any external axes measurement boards. Object Queue Lost on Warm Start or Power Failure The object queue is kept on the DSQC 354. If the system is restarted with a Warm Start or if the power supply to either the S4C controller or the DSQC 354 fails, then the object queue will be lost. Minimum and Maximum Speed There is a minimum conveyor speed in order to maintain smooth and accurate motions. This speed is dependent upon the encoder selection and can vary from 4 mm/s to 8 mm/ s. See Minimum and Maximum Counts per Second under 7.1 Encoder Type Selection. There is no explicit maximum speed for the conveyor. Accuracy will degrade at speeds above the specification and with high speed robot motions or with very high conveyor speeds (> 500 mm/s) and the robot will no longer be able to follow the conveyor. WaitWObj after DropWObj If a WaitWObj instruction is used immediately after a DropWObj instruction, it may be necessary to add a WaitTime 0.1; after the DropWObj instruction.
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Principles of Conveyor Tracking in S4C
3 Principles of Conveyor Tracking in S4C Conveyor Tracking is built upon the coordinated work object concept taken from coordinated motion with external axes. See User’s Guide, Chapter 10 Calibration, Section 2 Coordinated Axes for additional information. Conveyor as a Mechanical Unit Primary to this concept is the treatment of the conveyor as a mechanical unit. For the S4C, the conveyor is a mechanical unit with all features of a mechanical unit except that it is not under control of the S4C controller. As a mechanical unit it may be activated, deactivated, the position of the conveyor appears in the Teach Pendant Jogging Window and in the robtarget when a MODPOS operation is performed. Conveyor Coordinated Work Object For conveyor tracking, the robot movements are coordinated to the movements of a user frame connected to the conveyor mechanical unit. E.g. a user frame is placed on the conveyor and connected to its movements. An work object is used for this purpose and it is marked with the name of the conveyor mechanical unit, and that the work object is moveable. The conveyor tracking coordination will be active if the mechanical unit is active, and the conveyor coordinated work object is active. When the conveyor coordinated work object is used, in jogging or in a move instruction, the data in the “uframe” component will be ignored and the location of the user coordinate system will only depend on the movements of the conveyor mechanical unit. However the “oframe” component will still work giving an object frame related to the user frame and also the displacement frame may be used. Waiting for a Work Object on the Conveyor The difference between a conveyor coordinated work object and a work object that is coordinated to another type of mechanical unit is that there is no work object for coordination until an object appears on the conveyor. Before the robot can coordinate the TCP positions to a conveyor, there must be a work object present on the conveyor. Work objects on the conveyor are detected by means of the synchronization switch that is connected to the DSQC 354 Encoder Interface Unit. This unit will track all objects that have gone past the synchronization switch and are within specified distances in the work area. Before starting coordinated motion with the conveyor, the RAPID program must first check with the Encoder Interface Unit whether or not there is a work object available on the conveyor. If an object is available then execution continues and the motions may use the coordinated work object. If there is no object, then the RAPID program waits until a work object is available. Connecting to a Work Object The RAPID instruction WaitWObj, see Section 5 RAPID Instructions below for more details, is used to wait for a work object on the conveyor before starting conveyor coordinated motion. When the WaitWObj instruction is successful then the conveyor work object is said to be “connected” to the RAPID program.
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Conveyor Tracking
Once a RAPID program has connected to a work object on the conveyor then robot motion instructions and jogging commands may use this work object just as any other work object. When using the conveyor connected coordinated work object then all motions are relative to the work object on the conveyor. The user may change work objects several times and thus coordinate the robot to other work objects in the system and still return to the conveyor coordinated work object. Disconnecting from a Work Object The S4C controller and Encoder Interface Unit will maintain the connection to the work object until one of the following events occurs: A DropWObj instruction is issued, the Maximum Distance, as defined for the conveyor, is reached, restart of the controller, power supply failure to either the Encoder Interface Unit or controller. The connection to the work object will not be lost with deactivation of the conveyor mechanical unit and will return upon re-activation. The DropWObj instruction is used to end the connection before the Maximum Distance is reached. After a DropWObj instruction is issued it is possible to immediately wait for and connect to the next work object in the conveyor object queue. If a DropWObj instruction is not issued, then the object will be automatically disconnected and dropped when the Maximum Distance is reached.
3.1 Start Window and Queue Tracking Distance The S4C controller and DSQC 354 will maintain the object queue based upon a set of distances relative to the conveyor and synchronization switch. The following figure shows these relationships:
Work Object User Frame
Synchronization Switch 7
6
5
Minimum Dist.
4 Start Window Width
0.0 m
y
3
2
1
x
Conveyor Direction
Working Area Maximum Distance
Queue Track. Dist.
-
z
+
Figure 2 Relationships between Distances along the Conveyor
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Principles of Conveyor Tracking in S4C
Queue Tracking Distance
This distance defines the placement of the 0.0 meter point relative to the synchronisation switch on the conveyor. The Encoder Interface Unit tracks all objects in this distance. The position returned from the Encoder unit for the object will be negative, relative to the 0.0 m point.
Start Window Width
This distance defines the start window. The start window defines the area that if a program starts using an object within the window, then all program coordination can end before the Maximum Distance or work area is reached. All objects within this window are tracked and are eligible for use in a coordinated work object. A WaitWObj instruction will connect to the first object in the window.
Maximum Distance
This distance is the maximum distance that a connected object may have before being automatically dropped. If an object is dropped, then any coordinated motions are terminated with an error message.
Minimum Distance
This is the minimum distance that a connected object may have before being automatically dropped. If the conveyor stops and runs backwards, then there will be an automatic drop when the connected object goes past the minimum distance. This may be greater than or less than the Queue Tracking Distance.
Using the above distance definitions the conditions and states of objects 1...7 in Figure 2 may be described: Object 1
This object is connected as indicated by the coordinate frame attached to the object’s position on the conveyor.
Object 2
Object 2 is outside the start window and is no longer tracked by the Encoder unit. This object will be skipped and cannot be connected by a WaitWObj instruction. It is skipped because the conveyor speed is such that coordination with the object could not be completed before the object moved outside the maximum distance or work area of the robot.
Objects 3 and 4
These objects are within the start window and are tracked by the Encoder unit. If Object 1 was dropped via a DropWObj instruction then Object 3 would be the next object to be connected when a WaitWObj instruction was issued. Because Objects 3 and 4 were in the start window, the WaitWObj instruction will not wait but return immediately with object 3.
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Principles of Conveyor Tracking in S4C
Conveyor Tracking
Objects 5 and 6
These objects lie within the queue tracking distance and are tracked by the Encoder unit. If objects 3 and 4 were not present, then a WaitWObj instruction would stop program execution until object 5 entered the start window.
Object 7
This object has not yet passed the synchronization switch and has not yet been registered by the Encoder Interface Unit.
3.2 Coordinate Systems
Synchronization Switch
z
z
User Frame
Object Frame x
y
x Base Frame (conveyor) Minimum Dist.
y
z
y
Conveyor Direction
x
Start Window Width Maximum Distance
Queue Track. Dist.
0.0 m
z
z y x World Frame
x y Base Frame (Robot)
Figure 3 Conveyor Tracking Coordinate Systems
The above figure shows the principle coordinate frames used in conveyor tracking. The table below provides an overview of these coordinate frames
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Coordinate System
Defined Where
Base Frame of robot
Service/View: BaseFrame.
Relative to
Base frame definition of robot gives relation between world and base frame.
World Frame
World Frame
No definition needed
Nothing
Base Frame of conveyor
Defined from measurements using robot. See Installation and Calibration below.
World Frame
Conveyor Tracking
Conveyor Tracking
Principles of Conveyor Tracking in S4c
Coordinate System
Defined Where
Relative to
User Frame, coordinated to conveyor
Program/View: Data Types - wobjdata Select conveyor mechanical unit
World Frame via Base Frame of conveyor.
Program/View: Data Types - wobjdata
User Frame
Object Frame (not shown)
The two key frames in conveyor tracking are the Base Frame of the conveyor and the User Frame in the conveyor coordinated work object. The position of User Frame in the conveyor coordinated work object is determined from the position of the conveyor Base Frame and the linear position of the conveyor in meters. The DSQC 354 Encoder Interface Unit provides the position of the conveyor relative the synchronization switch and the Queue Tracking Distance. When the encoder unit sends a value of 0.0 meters to the S4C controller, then the User Frame for the conveyor coordinated work object is coincident with the Base Frame of the conveyor. As the conveyor moves, then the User Frame in the conveyor coordinated work object moves along the X-axis of the conveyor Base Frame.
4 Programming Conveyor Tracking In order to make a program that uses conveyor tracking and a conveyor coordinated work object, one must first make sure that a work object is present within the start window of the Encoder Interface Unit. To accomplish this an object must be moved past the synchronization switch and into the start window. If there are several objects already on the conveyor, then it may be necessary to first clear the object queue and then move the conveyor.
4.1 Working with the Object Queue The S4C conveyor option provides several I/O signals which allow a user or RAPID program to monitor and control the Object Queue on the encoder unit. The following table shows the I/O signals which impact the Object Queue.
I/O Signal
Description
c1ObjectsInQ
Group input showing the number of objects in the Object Queue. These objects have passed the synchronization switch but have not gone outside the startwindow.
c1Rem1PObj
Remove First Pending Object from the Object Queue. Setting this signal will cause the first pending object to be dropped from the Object Queue. Pending objects are objects that are in the queue but are not connected to a work object.
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c1RemAllPObj
Remove All Pending Objects. Setting this signal will cause the Encoder Interface Unit to empty all objects from the Object Queue. If an object is connected, then it is not removed.
c1DropWObj
Setting this signal will cause the encoder unit to drop the tracked object and disconnect that object. The object is removed from the queue.
4.2 Activating the Conveyor As an external axis and mechanical unit the conveyor must be activated before it may be used for work object coordination. The usual ActUnit instruction is used to activate the conveyor and DeactUnit may be used to deactivate the conveyor. By default, the conveyor is installed non-active on start. If desired, the conveyor may be configured to be always active upon start. See Section 9.9 Motion Mechanical Unit Parameters below. Automatic Connection upon Activation: When a conveyor mechanical unit is activated, it first checks the state of the encoder unit to see whether the object was previously connected. If the encoder unit, via the I/ O signal c1Connected, indicates connection, then the object on the conveyor will automatically be connected upon activation. The purpose of this feature is to automatically reconnect in case of a power failure with power backup on the Encoder Interface Unit.
4.3 Defining a Conveyor Coordinated Work Object From the programming window, view the wobjdata and create a new work object, wobjcnv1. Set the ufprog and ufmec as follows: ufprog
(user frame programmed)Data type: bool
Defines whether or not a fixed user coordinate system is used: - FALSE-> Movable user coordinate system, i.e. coordinated to conveyor. ufmec
(user frame mechanical unit)Data type: string
The conveyor mechanical unit with which the robot movements are coordinated. Specified with the name that is defined in the system parameters, e.g. “CNV1”.
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Programming Conveyor Tracking
4.4 Waiting for a Work Object Motions that are to be coordinated to the conveyor can not be programmed until an object on the conveyor has been connected via a WaitWObj instruction. If the object on the conveyor is already connected from a previous WaitWObj or if connection was established during activation, then execution of a 2nd WaitWObj instruction will cause an error. This error can be handled in an error handler if desired. The details of the WaitWObj are given in Section 5 RAPID Instructions.
4.5 Programming the Conveyor Coordinated Motion 1.
Create a program with the following instructions: ActUnit CNV1; ConfL/Off; MoveL waitp, v1000, fine, tool; WaitWObj wobjcnv1;
2.
Single-step the program past the WaitWObj instruction. If there is an object already in the start window on the conveyor then the instruction will return, else execution will stop while waiting for an object on the conveyor.
3.
Run the conveyor until an object passes the sync signal. The program should exit the WaitWObj and is now ‘connected’ to the object. Stop the conveyor with the object in an accessible portion of the workspace.
4.
Teach the MoveL, MoveC, PaintL, or PaintC instructions using the wobjcnv1 conveyor coordinated work object.
5.
End the coordinated motion with a fixed-frame work object (not coordinated to the conveyor). Note that this is the only way to end the use of the work object.
6.
Program a DropWObj wobjcnv1; instruction
7.
If this is the end of the program, or the conveyor is no longer needed, then program a DeactUnit CNV1; instruction.
Example: The following program shows an example for a conveyor tracking program. ConfL\Off; MoveJ p0, vmax, fine, tool1; ActUnit CNV1; WaitWObj wobjcnv1; MoveL p10, v1000, z1, tool1\Wobj:=wobjcnv1; MoveL p20, v1000, z1, tool1\Wobj:=wobjcnv1; MoveL p30, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p40, v500, fine, tool1; DropWObj wobjcnv1; MoveL p0, v500, fine; DeactUnit CNV1; Conveyor Tracking
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4.6 Dropping a Work Object A connected work object may be dropped once conveyor coordinated motion has ended. It is important to make sure that the robot motion is no longer using the conveyor positions when the work object is dropped. If motion still requires the positions then a Stop will occur when the object is dropped. Conveyor coordinated motion does not end in a finepoint. As long as the work object is coordinated to the conveyor, the robot motion will be coupled to the conveyor even in a finepoint. A fixed-frame or non-conveyor work object must be used in a motion instruction before dropping the conveyor work object. Care must be taken when ending coordination in a corner zone and executing the DropWObj instruction as the work object will be dropped before the robot has left the corner zone and the motion still requires the conveyor coordinated work object. It is not necessary to be connected in order to execute a DropWObj instruction. No error will be returned if there was no connected object.
4.7 Entering and Exiting Conveyor Tracking Motion in Corner Zones Once a WaitWObj instruction has connected to a work object on the conveyor then it is possible to enter and exit coordinated motion with the conveyor via corner zones. The following is an example: MoveL p10, v1000, fine, tool1; WaitWObj wobjcnv1; MoveL p20, v1000, z50, tool1; - enter coordination in zone MoveL p30, v500, z1, tool1\Wobj:=wobjcnv1; MoveL p40, v500, z1, tool1\Wobj:=wobjcnv1; MoveL p50, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p60, v1000, z50, tool1; - exit coordination in zone MoveL p70, v500, fine, tool1; DropWObj wobjcnv1; MoveL p10, v500, fine, tool1; The move instruction ending coordination must be a ‘fixed’ work object. e.g. ufprog is TRUE. As noted above, care must be taken when exiting coordination in a corner zone and executing a DropWObj instruction. The following example shows an incorrect method for ending coordination in corner zones: ... MoveL p50, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p60, v1000, z50, tool1; - exit coordination in zone DropWObj wobjcnv1; - ERROR, work object is dropped while robot is still in corner zone.
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Programming Conveyor Tracking
4.8 Information on Teach Pendant The user has access to the conveyor position and speed via the Teach Pendant. Jog Window: The position in millimeters of the conveyor object is shown in the jog window. This value will be negative if a Queue Tracking Distance is defined. When an object passes the synchronization switch then the position will be automatically updated in the jog window. I/O Window: From the I/O Window the user has access to all the signals that are defined on the Encoder Interface Unit. From this window it is possible to view the conveyor position in meters, and the conveyor speed in meters/s. The speed will be 0 m/s until an object has passed the synchronization switch.
4.9 Programming Considerations Performance Limits Conveyor tracking will be lost if joint speed limits are reached, particularly in singularities. It is the responsibility of the programmer to ensure that the path during tracking does not exceed the robots speed and motion capabilities. Motion Commands Only Linear and Circular motion commands are allowed for conveyor tracking. Change of Tool Changing the tool is not allowed during conveyor tracking as the motion during a tool change is a joint motion. Finepoints Finepoints are allowed during conveyor tracking. The robot will hold the TCP still relative to the conveyor and RAPID execution will continue, see Section 4.10 Finepoint Programming below. ConfL The RAPID instruction ConfL\Off must be executed before coordination with the conveyor. The purpose is to avoid configuration errors that would otherwise occur as the robot changes configuration during conveyor tracking.
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Conveyor Tracking
Other RAPID Limitations The commands, StorePath, RestoPath do not function during conveyor tracking. No Search commands function during conveyor tracking. EoffsSet, EoffsOn, EoffsOff have no effect for the conveyor external axis.
4.10 Finepoint Programming While tracking the conveyor it is possible to use a finepoint. The following program example shows how motion may be stopped with respect to the conveyor so that an I/O signal may be set: WaitWObj wobjcnv1 MoveL p1, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p2, v500, fine, tool1\Wobj:=wobjcnv1; SetDO release_gripper; WaitTime 0.1; MoveL p3, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p4, v500, fine, tool1; DropWObj wobjcnv1; In the above example the SetDO will be executed after the robot arrives at p2. The robot will then track the conveyor for 0.1 seconds while the WaitTime instruction is executed. It will then move to p3 and on to p4 via a corner zone before ending coordination with a fixed work object (wobj0 in this case).
4.11 Modes of Operation Operation under Manual Reduced Speed Mode (< 250 mm/s) When the conveyor is not moving, then the FWD, BWD buttons may be used to step through the program. New instructions may be added and MODPOS may be used to modify programmed positions. In order to facilitate programming, the conveyor may be moved to new positions between instructions. The robot will return to the correct position when FWD or BWD is pressed. The robot will recover as normal if the Enable switch is released during motion. The robot cannot perform coordinated motions to the conveyor while in Manual Reduced Speed mode and the conveyor is moving. Operation under AUTO Once a WaitWObj instruction has been executed, then it is no longer possible to step through the program with FWD and BWD while the conveyor is moving.
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Programming Conveyor Tracking
Start/Stop The robot will stop and no longer track the conveyor if the STOP button is pressed or Stop, StopMove RAPID instructions are executed between the WaitWObj and DropWObj instructions. The conveyor coordinated work object will not be lost but if the conveyor is moving then the object will quickly move out of the working area. RESTART from the current instruction is not possible and the program must be restarted from either from MAIN or a WaitWObj instruction.
Emergency Stop/Restart When the Emergency Stop is pressed the robot will stop immediately. If the program was stopped after a WaitWObj then the coordinated work object will not be lost but if the conveyor is moving then the object will quickly move out of the working area. RESTART from the current instruction is not possible and the program must be restarted either from MAIN or a WaitWObj instruction. Operation under Manual Full Speed Mode (100%) Operation under Manual (100%) is similar to operation under AUTO. The program may be run by holding the START button, but once a WaitWObj instruction has been executed then it is no longer possible to step through the program with the FWD and BWD buttons while the conveyor is moving.
Stop/Restart When the START button is released, or Emergency Stop is pressed, the robot will stop immediately. If the program was stopped after a WaitWObj then the coordinated work object will not be lost but if the conveyor is moving then the object will quickly move out of the working area. RESTART from the current instruction is not possible and the program must be restarted either from MAIN or a WaitWObj instruction.
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RAPID Instructions
Conveyor Tracking
5 RAPID Instructions WaitWObj
Wait for Work Object on Conveyor
WaitWObj (Wait Work Object) connects to a work object in the start window on the conveyor mechanical unit.
Example WaitWObj wobj_on_cnv1; The program connects to the first object in the object queue that is within the start window on the conveyor. If there is no object in the start window then execution stops and waits for an object.
Arguments WaitWObj WObj
WObj [ \RelDist ] (Work Object)
Data type: wobjdata
The moving work object (coordinate system) to which the robot position in the instruction is related. The mechanical unit conveyor is to be specified by the ufmec in the work object. [ \RelDist ]
(Relative Distance)
Data type: num
Waits for an object to enter the start window and go beyond the distance specified by the argument. If the work object is already connected, then execution stops until the object passes the given distance. If the object has already gone past the Relative Distance then execution continues.
Program execution If there is no object in the start window then program execution stops. If an object is present, then the work object is connected to the conveyor and execution continues. If a second WaitWObj instruction is issued while connected then an error is returned unless the \RelDist optional argument is used.
Examples WaitWObj wobj_on_cnv1\RelDist:=500.0; If not connected, then wait for the object to enter the start window and then wait for the object to pass the 500 mm point on the conveyor. If already connected to the object, then wait for the object to pass 500 mm.
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Conveyor Tracking
RAPID Instructions
WaitWObj wobj_on_cnv1\RelDist:=0.0; If not connected, then wait for an object in the start window. If already connected, then continue execution as the object has already gone past 0.0 mm.
WaitWObj wobj_on_cnv1; WaitWObj wobj_on_cnv1\RelDist:=0.0; The first WaitWObj connects to the object in the start window. The second WaitWObj will return immediately if the object is still connected, but will wait for the next object if the previous object had moved past the Maximum Distance or was dropped.
Limitations It requires 100 ms to connect to the first object in the start window. Once connected, a second WaitWObj with \RelDist optional argument will take only normal RAPID instruction execution time.
Error handling If following errors occurs during execution of the WaitWobj instruction, the system variable ERRNO will be set. These errors can then be handled in the error handler. ERR_CNV_NOT_ACTThe conveyor is not activated. ERR_CNV_CONNECTThe WaitWobj instruction is already connected. ERR_CNV_DROPPEDThe object that the instruction WaitWobj was waiting for has been dropped by another task. (DSQC 354Revision 2: an object had passed the start window)
Syntax WaitWObj [ WObj ’:=’]< persistent (PERS) of wobjdata> ‘;’ [ ’\’ RelDist ’:=’ < expression (IN) of num > ]
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21
RAPID Instructions
DropWObj
Conveyor Tracking
Drop Work Object on Conveyor
DropWObj (Drop Work Object) is used to disconnect from the current object and the program is ready for the next.
Example MoveL *, v1000, z10, tool, \WObj:=wobj_on_cnv1; MoveL *, v1000, fine, tool, \WObj:=wobj0; DropWObj wobj_on_cnv1; MoveL *, v1000, z10, tool, \WObj:=wobj0;
Arguments DropWObj WObj
WObj (Work Object)
Data type: wobjdata
The moving work object (coordinate system) to which the robot position in the instruction is related. The mechanical unit conveyor is to be specified by the ufmec in the work object.
Program execution Dropping the work object means that the encoder unit not longer tracks the object. The object is removed from the object queue and cannot be recovered.
Limitations If the instruction is issued while the robot is actively using the conveyor coordinated work object then the motion stops. The instruction may be issued only after a fixed work object has been used in the preceding motion instructions with either a fine point or several (>1) corner zones.
Syntax DropWObj [ WObj ’:=’] < persistent (PERS) of wobjdata> ‘;’
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Additional Features
6 Additional Features for the DSQC 354 Revision 2 The S4C software supports the additional feature that is available in the DSQC 354 Revision 2: Notification of Passed Start Window: In certain applications it is important to know whether an object has gone through the start window without being connected. The DSQC 354 Revision 2 Encoder interface unit supports an additional feature which allows the S4C software to detect when an object has passed the start window without being connected and is thus lost. The detection of the lost object is done on the next WaitWObj instruction. The next WaitWObj instruction, following after an object has moved outside the start window, will return with the error ERR_CNV_DROPPED. This error can be handled in the RAPID Error handler. The DSQC 354 Revision 2 unit returns a new I/O signal, c1PassStw, on physical signal 12 from the Encoder interface unit. This signal will go high when the next connect is attempted and one or more objects have left the start window without being connected. It may be desirable to disable the automatic use of the c1PassStw signal and use this signal directly in the user’s RAPID application. Disabling the Passed Start Window Feature in WaitWObj: This feature of the DSQC 354 Revision 2 unit may not be desirable in all applications as it may limit backwards compatibility or may complicate the application. The feature can be disabled via removing a Conveyor I/O signal: Under System Parameters, Process, Types: Conveyor Systems. Remove the signal name used for PassStartW signal. This will stop the ERR_CNV_DROPPED from occurring on the next WaitWObj instruction. The c1PassStw signal from the DSQC 354 will still go high but the conveyor tracking function will no longer be looking for the signal.
7 Hardware Configuration and Connections The conveyor interface to the S4C controller is via the DSQC 354 Encoder Interface unit. Two versions of the DSQC 354 exist, namely the original unit and a Revision 2 unit. The Revision 2 unit is clearly marked and is electrically compatible with the original.
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Hardware Configuration and Connections
Conveyor Tracking
7.1 Encoder Type Selection The encoder provides a series of pulses indicating the motion of the conveyor. This is used to synchronize the motions of the robot to the motion of the conveyor. The encoder has two pulse channels, A and B which differ in phase by 90°. Each channel will send a fixed number of pulses per revolution depending upon the construction of the encoder. The number of pulses per revolution for the encoder must be selected in relation to the gearing between the conveyor and the encoder. The pulse ratio from the encoder should be in the range of 1250 - 2000 pulses per meter of conveyor motion. The pulses from channels A and B are used in quadrature to multiply the pulse ratio by 4 to get counts. This means that the control software will measure 5000 - 10000 counts per meter for an encoder with the pulse ratio given above. Reducing the number of measured counts below 5000 will reduce the accuracy of the robot tracking. Increasing the number of measured counts beyond 10000 will have no significant effect as inaccuracies in robot and cell calibration will be the dominating factors for accuracy. The encoder must be of 2 phase type for quadrature pulses, to enable registration of reverse conveyor motion, and to avoid false counts due to vibration etc. when the conveyor is not moving. Output signal: Voltage: Current Phase: Duty cycle:
Open collector PNP output 10 - 30 V (normally supplied by 24 VDC from DSQC 354) 50 - 100 mA 2 phase with 90 degree phase shift 50%
An example encoder is the Lenord & Bauer GEL 262. Minimum and Maximum Counts per Second Minimum Speed There is a lower limit on the number of counts per second before the encoder unit signals zero speed. This limit is 40 counts per second. If the speed of the conveyor is lower than this value, zero speed will be indicated. At 10,000 counts per meter, the minimum conveyor speed is 4 mm/s. Maximum Speed There is a upper limit on the number of counts per second before the encoder unit can no longer keep track of the counts along the conveyor. This limit is 20,000 counts per second. At 10,000 counts per meter, the maximum conveyor speed is 2,000 mm/s.
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Conveyor Tracking
Hardware Configuration and Connections
7.2 Encoder Location The encoder is normally installed on the conveyor drive unit. The encoder may be connected to an output shaft on the drive unit, directly or via a gear belt arrangement. If the encoder is connected directly to a drive unit shaft, it is important to install a specially designed flexible coupling to prevent applying mechanical forces to the encoder rotor. A coupling using a plastic/rubber hose should be avoided. If the drive unit includes a clutch arrangement, the encoder must be connected on the conveyor side of the clutch. If the conveyor drive unit is located a long distance away from the robot then the conveyor itself may be a source of inaccuracy as the conveyor will stretch or flex over the distance from the drive unit to the robot cell. In such a case it may be better to mount the encoder closer to the robot cell with a different coupling arrangement.
7.3 Encoder Connection to DSQC 354 One encoder may be connected to one or more Encoder Interface Units. The Encoder Interface Units may be connected to the same S4C cabinet as in the case for 2 conveyors, or to different S4C cabinets when two different robots shall follow the same conveyor. If the encoder is connected to Encoder Interface Units that are connected to different S4C cabinets, a diode should be installed on each of the 24 V DC connections to the encoder to prevent parallel wiring of the power supplies. The encoder should be connected to the robot by a screened cable to reduce noise. If this cable is long, the inductance in the cable will produce spike pulses on the encoder signal which may, over a period of time, damage the opto couplers in the Encoder Interface Unit. The spike pulses can be removed by installing a capacitor between the signal wire and ground for each of the 2 phases. The capacitors should be connected on the terminal board where the encoder is connected and not on the DSQC 354. Typical capacitor values are 100 nF - 1 µ F, depending on the length of the cable. The longer the cable, the larger the capacitor. The correct capacitance value can be determined by viewing the encoder signal on an oscilloscope. See the Product Manual, Installation and Commissioning, for details on connecting the encoder to the Encoder Interface Unit.
7.4 Synchronization Switch The synchronization switch indicates the presence of objects on the conveyor. This switch should be chosen so that it provides a reliable and repeatable signal for objects on the conveyor regardless of conveyor speed. If the conveyor can run backwards, then the switch should be constructed not to give a signal if an object runs backwards past the switch. If the synchronization switch can give multiple signals when an object passes then the parameter SyncSeparation can be set to so that only one signal is accepted as an object before a given distance is covered on the conveyor. See Section 9.5 Conveyor Start Window and Sync Separation. Conveyor Tracking
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Conveyor Tracking
7.5 Connecting the DSQC 354 to the S4C Cabinet See the documentation on the CAN bus distributed I/O and DSQC 354 for information on physically connecting to the CAN bus in the S4C.
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Software Installation
8 Software Installation The conveyor tracking feature and the RAPID instructions WaitWObj, DropWObj, are specified in the key disk for the S4C disk pack. Normally the Conveyor software is preloaded at the factory and does not need to be re-installed unless access to the Motion System parameters is necessary. The following instructions are intended for use when the Conveyor option is to be added to an existing system. The conveyor option will install three additional configurations: I/O for the DSQC 354, Conveyor process description, and a Motion mechanical unit description. Choose ‘Query’ during boot and select ‘Service’ for motion parameters in order to gain full access to the Motion system parameters that must be modified for conveyor tracking installation. The DSQC 354 should be connected to the CAN bus before installing the conveyor tracking software. The conveyor tracking software will automatically install an External I/O configuration for the encoder unit on address 15 on the CAN bus. If the encoder unit is not at this address, I/O errors will occur at startup. The recommended installation sequence can be described as follows: 1.
Connect the DSQC 354 to the CAN bus. Note the CAN address on the unit.
2.
Install the Conveyor Tracking software. If the DSQC 354 is not on address 15 then I/O errors can be expected.
3.
If necessary, correct the address for the encoder unit specified in the System Parameters: I/O System.
4.
Reload the manipulator calibration parameters. Use Add or Replace Parameters from the File menu under System Parameters window. Load the original calibration parameters from the Manipulator Parameters disk. Note: if you must reload the old MOC saved parameters then see Reloading MOC Saved Parameters below.
5.
Restart the system. There should be no errors and the CNV1 mechanical unit should be available under the Jog Window of the Teach Pendant.
Reloading MOC Saved Parameters During installation, the conveyor option will load a specific conveyor external axis configuration file into the motion system parameters. If during Step 4 above, you loaded saved motion system parameters that were defined before the installation of conveyor software then the CNV1 mechanical unit will not appear on the Teach Pendant in Step 5.
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Conveyor Tracking
In order to recover the CNV1 mechanical unit the motion configuration file must be loaded manually off of disk 8 of the System Pack. 1.
Insert disk 8 into the floppy drive
2.
Under the System Parameters window, File: Add new parameters, load the file cnv1_moc from the OPTCNV directory.
3.
Restart the system.
The CNV1 mechanical unit should now be available under the Jog Window of the Teach Pendant.
8.1 Installation of 2 Conveyors The conveyor option from the key disk automatically installs one conveyor into the S4C system parameters. If two conveyors are to be used with the same S4C cabinet then the system parameters for the 2nd conveyor must be loaded manually. The 2nd conveyor I/O configuration for the 2nd DSQC 354 will use address 16 by default. 1.
Connect the 2nd DSQC 354 to the CAN bus. Note the address on the CAN bus.
2.
Insert disk 8 into the floppy drive
3.
Under the System Parameters window, File: Add new parameters, load the files: cnv2_eio, cnv2_prc, and cnv2_moc from the OPTCNV directory.
4.
Restart the system.
5.
If necessary, correct the address for the Encoder2 unit specified in the System Parameters: I/O System.
The CNV1 and CNV2 mechanical units should now be available under the Jog Window of the Teach Pendant.
9 Conveyor Setup and Calibration This section describes how the conveyor and encoder are to be calibrated with respect to the robot and the robot world frame.
9.1 Direction of Positive Motion from Encoder The encoder direction of positive motion may be checked after the correct installation of the conveyor tracking software. Run an object past the synchronization switch while viewing the conveyor position from either the Jog Window or the I/O Window. If the value is negative, reverse the A and B inputs from the encoder to the Encoder Interface Unit.
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Conveyor Setup and Calibration
9.2 Calibration of Counts per Meter If the exact gear ratio between the encoder and the conveyor is unknown (typically the case) then the user must make a manual calibration of the counts per meter using either a tape-measure or the robot TCP as a measuring device. If the robot TCP is to be used as the measuring device then an accurately defined tool should be used. First configure the Encoder Interface Unit for 10000 counts per meter (default) and a Queue Tracking Distance of 0.0 m. The encoder unit I/O parameters are accessible via the System Parameters windows under the I/O Signals topic. • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select CountsPerMeter and change its value to 10000 • Press OK to confirm. • Select QueueTrckDist and change its value to 0.0 • Press OK to confirm. Parameter Description CountsPerMeter
Gives the number of counts per meter of motion of the conveyor. Should be in the range of 5000-10000 for linear conveyors.
QueueTrckDist
Queue Tracking Distance, this distance defines the placement of the synchronization switch relative to the 0.0 meter point on the conveyor. The encoder unit tracks all the objects in this distance but does not allow connection until object has passed 0.0 meters.
Move an object past the sync switch and stop the conveyor. Read the conveyor position from the Jog Window, position_1. Move the conveyor at least 1 meter and read the Jog Window, position_2. The accuracy will be best if this distance is large as possible within the workspace. Use a tape-measure (or differences in robot tool position) to find the exact number of meters from position_1 to position_2, call this value measured_meters. The counts per meter are calculated: ( position_2 - position_1 ) × 10000 counts per meter = --------------------------------------------------------------------------------measured_meters
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Conveyor Tracking
Enter the correctly calculated counts per meter into the I/O configuration for the Encoder Interface Unit CountsPerMeter.
9.3 Defining the Queue Tracking Distance Before proceeding with conveyor setup and calibration it is necessary to define the desired Queue Tracking Distance. As presented earlier, the Queue Tracking Distance establishes the distance between the synchronization switch and the 0.0 m point on the conveyor. The encoder unit will keep track of all objects that have passed the synchronization switch but have not yet passed the 0.0 m point. It is not possible to connect to these objects. Under the System Parameters window: • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select QueueTrckDist and change its value. • Press OK to confirm. Parameter Description QueueTrckDistQueue Tracking Distance (meters), this distance defines the placement of the synchronization switch relative to the 0.0 meter point on the conveyor. The encoder unit tracks all the objects in this distance but does not allow connection until the object has passed 0.0 meters.
9.4 Conveyor Base Frame Calibration The accuracy of the conveyor tracking is highly dependent upon the accuracy in calibrating the conveyor base frame. For linear conveyors a method is provided which uses the robot TCP in order to measure the position and orientation of the conveyor in the workspace. Before calibrating the base frame of the conveyor the values for the CountsPerMeter and QueueTrkDist must have been entered into the S4C controller and verified to be correct. The conveyor base frame calibration method will use the measurement of 3 positions of the same object on the conveyor to determine the conveyor base frame, as shown in Figure 4.
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Conveyor Tracking
Conveyor Setup and Calibration
Synchronization Switch
Base Frame z y
Conveyor Direction
QueueTrckDist
x
p_1
p_2
p_3
0.0 m
Conveyor distance Figure 4 Definition points for a Linear Conveyor
Prior to defining the 3 positions, an object must be defined on the conveyor: 1.
Step FWD through a RAPID program containing the two commands: ActUnit CNV1; WaitWObj wobjcnv1; Define the conveyor coordinated work object as described in Section 4.3 Defining a Conveyor Coordinated Work Object.
2.
Run the conveyor until an object passes through the sync switch and beyond the 0.0 m point. The WaitWObj instruction will end execution. Stop the conveyor.
Once a object is on the conveyor and beyond the 0.0 m point, it is possible to use the base frame calibration method to define the conveyor position and orientation in the workspace: • Press the Miscellaneous key
and select the Service window.
• Choose View:BaseFrame. A dialog containing all synchronized mechanical units is shown. • Select the conveyor mechanical unit and press Enter
or Def.
A dialog like the one in Figure 5 will appear.
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Conveyor Setup and Calibration
Conveyor Tracking
Lin Single User Frame Definition : CNV1 Unit : n points (n=3)... Status
Method Point
1(3)
Point 1 Point 2 Point 3
Modified ModPos
Cancel
(OK)
Figure 5 Dialog for definition of user frame for a rotational axis.
To choose a definition method Before you start modifying any positions, make sure the desired method is displayed. • Select the field Method and press Enter
.
• Choose number of points to use for definition and press OK. (Currently only the three point method is implemented.)
To record reference points • Select the first point Point 1. This point will be the origin for the user frame in the conveyor coordinated work object. • Point out Point 1 on the object on the conveyor with the robot’s TCP. • Modify the position by pressing the function key ModPos. • Move the conveyor in the positive direction and repeat the above for the points Point 2 and Point 3.
To calculate the base frame • Press OK to calculate the base frame for the selected conveyor mechanical unit. When the calculation is finished a dialog like the one in Figure 6 will appear.
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Conveyor Tracking
Conveyor Setup and Calibration
Lin Single User Frame Calc Result Unit : CNV1 Calculation Log Method Mean error Max error Cartesian X
1(10) n points (n=3) 1.12 2.31 7.08
File...
Cancel
OK
Figure 6 The result of a base frame calculation for a linear conveyor.
The calculation log shows the conveyor base frame expressed in the world coordinate system. Field
Description
Unit
The name of the mechanical unit for which the definition of base frame has be done.
List contents
Description
Method
Displays the selected calibration method.
Mean error
The accuracy of the robot positioning against the reference point.
Max error
The maximum error for one positioning.
Cartesian X
The x coordinate for the base frame.
Cartesian Y
The y coordinate for the base frame.
Cartesian Z
The z coordinate for the base frame.
Quaternion 1-4
Orientation components for the base frame.
The calculation result can be saved in a separate file for later use in a PC: - Press the function key File. - Specify a name and a location where to save the result. - Choose OK to confirm the save. If the estimated error is - acceptable, press OK to confirm the new user frame. - not acceptable, redefine by pressing Cancel. • Choose File: Restart in the Service window to activate the user frame.
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Conveyor Setup and Calibration
Conveyor Tracking
Verify the Results of the Calibration After restarting the controller, verify the conveyor base frame calibration as follows: 1.
Step FWD through a RAPID program containing the two commands: ActUnit CNV1; WaitWObj wobjcnv1;
2.
Run the conveyor until another object passes through the sync switch and beyond the 0.0 m point. The WaitWObj instruction will end execution. Stop the conveyor.
3.
Move the robot Tool Centre Point back to the previously chosen Point 1 on the work object.
4.
From the Jogging Window, read the X, Y, Z position of the Tool Centre Point. Use the accurate tool and use wobjcnv1.
5.
The robot’s TCP x, y, and z position in the work object coordinates should be 0.0 mm (or very close to that).
6.
Select WObj: wobjcnv1 together with Coord: WObj in the Jogging Window and jog the robot in the conveyor’s x, y, and z directions. Verify that the x-direction is in the direction of positive motion of the conveyor.
9.5 Conveyor Start Window and Sync Separation The Start Window is the length along the conveyor in which objects are tracked by the encoder unit and are ready for connection. When a WaitWObj instruction is issued the system will connect to the first object inside the start window or wait otherwise. If an object goes beyond the start window then it is no longer tracked and it is not available for connection. Such objects are automatically skipped. The purpose of the start window is to provide a buffer of objects for speed variations of the conveyor. If an object is connected within the start window then it should be certain that the motion coordinated to the object can be completed before the working area limit or maximum distance is reached. The Sync Separation parameter is used to filter out unwanted sync signals from a synchronization switch. This parameter establishes a minimum distance that the conveyor must move after one sync signal before a new sync signal is accepted as a valid object. Under the System Parameters window: • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select the parameters and change values. • Press OK to confirm.
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Conveyor Setup and Calibration
Parameter
Description
StartWinWidth
Start Window Width (meters), this distance defines the size of the start window. All objects within this window are tracked and are eligible for use in a coordinated work object. A WaitWObj instruction will connect to the first object in the window.
SyncSeparation
Sync Signal Separation (meters), this distance defines the minimum distance that the conveyor must move after a sync signal before a new sync signal is accepted as a valid object.
9.6 Conveyor Maximum and Minimum Distances It is possible to monitor the position of the conveyor and automatically drop any connected objects which move outside the maximum or minimum specified distance. The purpose is to prevent coordination of motion beyond the work area of the robot for both forward and backward operation of the conveyor. Under the System Parameters window, • Choose Topics: Process. • Choose Types: Conveyor Systems. • Select CONVEYOR1 and press Enter
.
• Select the parameters Maximum distance and Minimum distance and change the values. • Press OK to confirm. Parameter
Description
Maximum distance The maximum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is produced. Minimum distance The minimum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is produced.
9.7 Robot Adjustment Speed When entering conveyor tracking, the robot must adjust its speed up to the speed of the conveyor. The rate at which the robot ‘catches up’ to the conveyor for the first motion is controlled by the Adjustment Speed parameter. If the conveyor has a speed above 200 mm/s then this parameter may have to be increased in order for the robot to quickly move to the first point on the conveyor.
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Conveyor Setup and Calibration
Conveyor Tracking
Under the System Parameters window, • Choose Topics: Process. • Choose Types: Conveyor Systems. • Select CONVEYOR1 and press Enter
.
• Select the parameter Adjustment Speed and change the values. • Press OK to confirm. Parameter
Description
Adjustment Speed The speed (in mm/s) at which the robot should catch up to the conveyor for the first point coordinated to the conveyor position. It must be higher than the conveyor speed or the robot may never catch up to the conveyor.
9.8 Motion System Parameters There are two parameters that should be adjusted under the motion system. These parameters regulate the cpu load and the accuracy of the conveyor tracking under extreme conditions. The first parameter is Path resolution. This parameter specifies the period of the path planner in planning steps along the path (no units). Step calculations require lots of cpu time and if steps cannot be calculated in time to keep the robot on the path then error 50082 Deceleration Limit may occur. As conveyor tracking increases the general cpu load then the Path resolution parameter must be increased in order to prevent this error. The second parameter is Process update time. This parameter specifies the period (in seconds) at which the conveyor process should update the robot kinematics for path planning purposes. This parameter will affect conveyor accuracy only when the robot must make large reductions of programmed TCP speed due to dynamic considerations (singularities, large reorientations, and slow external axes). If the Process update time is set too large then errors in tracking will be small in the beginning of tracking but get larger after reductions of TCP speed. Decreasing Process update time will increase the cpu load and an increase of the Path resolution will be necessary.
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Conveyor Tracking
Conveyor Setup and Calibration
Under the System Parameters window, • Choose Topics: Manipulator. • Choose Types: Motion system. • Select system_1 and press Enter
.
• Select the parameters Path resolution, and Process update time and change the values. • Press OK to confirm. Parameter
Description
Path resolution The period at which steps along the path are calculated. Increase by 20% for conveyor tracking. Process update time The time (in seconds) at which the conveyor process updates the robot kinematics on the conveyor position. Set to 0.09677
9.9 Motion Mechanical Unit Parameters The mechanical unit parameters define the name used by the conveyor for RAPID and the Teach Pendant as well as the conditions for activation and deactivation. These parameters may be changed to give a customer defined name to the conveyor and to ensure activation of the conveyor. Under the System Parameters window, • Choose Topics: Manipulator. • Choose Types: Mechanical Unit • Select CNV1 and press Enter
.
• Select the parameters and change the values: Parameter
Description
Name The name of the unit (max. 7 characters). This name will subsequently be used in the Jogging window and from the program, e.g. when an unit is to be activated. Activate at start up
The conveyor is to be activated automatically at start up.
Do not allow deact.
The conveyor cannot be deactivated.
9.10 Configuration for Track Motion following Conveyor If the robot is mounted on a track, and the track is parallel to the conveyor, then the motion can be configured such that the track follows the conveyor. The IRB robot manipulator and track must be configured for Coordinated Track Motion. See the User’s Guide for information on configuring the robot and track for coordinated motion.
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Conveyor Setup and Calibration
Conveyor Tracking
Once the robot and track are configured for coordinated motion, then conveyor tracking will automatically use the track to follow the conveyor. The track will maintain the same position relative to the object as the object moves on the conveyor as it was during programming. The track and robot base frame must be defined such that positive motion of the track is in the same direction as the conveyor. In some installations this may require a redefinition of the track’s direction of positive motion and calibration position. See Figure 7 below. Yconveyor
Conveyor Direction
X conveyor
YWorld, Track
X
X robot Yrobot
World, Track
- + Direction of Track 0.0 m Conveyor Quaternion: 1, 0, 0, 0 Robot Base Quaternion: 0.7071, 0, 0, 0.7071 Track Base Quaternion: 1, 0, 0, 0 Figure 7 Example Configuration of Track and Conveyor Directions
Performance Considerations: Avoid moving the track when making the conveyor coordinated portion of the RAPID program. All motions of the track relative to the conveyor are saved and played back during conveyor tracking. Tracks typically have an acceleration ability that is far below that of the robot joints. If the track must move relative to the object then this will require an acceleration that will cause a reduction of the robot’s TCP speed along the path in order to maintain coordination.
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Conveyor Tracking
Circular Conveyor Tracking
10 Circular Conveyor Tracking The conveyor tracking software provides the capability of tracking circular conveyors. The fundamental principle for configuration of circular conveyor tracking is to replace all references to ‘meters’ by ‘radians’ and proceed with the configuration as given in the Section 9 Conveyor Setup and Calibration. This section will review the steps in setup and configuration and note those places where the configuration must be changed to accommodate a circular conveyor. The following figure shows an example of circular conveyor tracking with example units and distances:
CountsPerMeter = 40000 counts per radian At 6 m radius, one count = 0.15 mm Direction of Rotation
Minimum Distance = -100 milliradians At 6 m radius, = -600 mm
2.44 rad
radius = 6 meter Y
X
Synch Switch SyncSeparation = 0.005 rad At 6 m radius, = 30 mm QueueTrkDist = 0.017 rad At 6 m radius, = 100 mm
0.0 rad
Xworld
Conveyor Base Frame: Base frame x = 8.0 m Base frame y = 0.0 m Base frame z = 0.0 m The X axis is rotated 2.44 rad from the World X, Base frame q1 = 0.3420 Base frame q2 = 0.0000 Base frame q3 = 0.0000 Base frame q4 = 0.9397
Maximum Distance = 420 milliradians At 6 m radius, = 2520 mm
StartWinWidth = 0.017 rad At 6 m radius, = 100 mm
Yworld Figure 8 Example Configuration of Circular Conveyor Tracking
10.1 Encoder Type Selection and Location The goal in selecting an encoder for circular conveyor tracking is to have 0.1 mm to 0.2 mm resolution per count at the maximum radius of conveyor tracking. Example: Following Figure 8 , at a 6 meter radius in order to have 0.15 mm per count, we must have 40,000 counts per radian at the centre of the table. The counts are quadrature encoded (four counts per pulse), thus the encoder must give 10,000 pulses per radian of circular conveyor movement. For a full revolution there are 2π radians per revolution, giving a requirement for 10000 × 2π = 62831,85 pulses per revolution of the circular conveyor.
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39
Circular Conveyor Tracking
Conveyor Tracking
Gear Ratio Selection: If an encoder with 1000 pulses per revolution is selected, then we require a gear ratio of 1 to 62.83185 between the circular conveyor and the encoder shaft. Note: The maximum value for configuration of CountsPerMeter in the encoder software is 50000. This limitation should be taken into consideration when selecting gearing and encoder.
10.2 Software Installation The DSQC 354 Encoder Interface Unit and conveyor tracking software are connected and installed in the same manner as for linear conveyors.
10.3 Direction of Positive Motion from Encoder See the description for linear conveyors, Section 9.1.
10.4 Calibration of Counts per Meter For a circular conveyor, the setting of the CountsPerMeter parameter should be known from the selection of the encoder and the gear ratio between the circular conveyor and the encoder shaft. If the value is not known, then it is possible to measure the value following the same steps as outlined for a linear conveyor with extra equipment for measuring the change in angle of the conveyor between position_1, and position_2.
10.5 Defining the Queue Tracking Distance Before proceeding with conveyor setup and calibration it is necessary to define the desired Queue Tracking Distance. The Queue Tracking Distance establishes the distance between the synchronization switch and the 0.0 rad point on the circular conveyor. The encoder unit will keep track of all objects that have passed the synchronization switch but have not yet passed the 0.0 rad point. Under the System Parameters window: • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select QueueTrckDist and change its value. • Press OK to confirm.
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Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
Parameter
Description
QueueTrckDist
Queue Tracking Distance (radians for circular conveyor). This distance defines the placement of the synchronization switch relative to the 0.0 rad point on the conveyor. The encoder unit tracks all objects in this distance but does not allow connection until an object has passed 0.0 rad.
10.6 Circular Conveyor Base Frame Calibration - Manual Method The accuracy of the circular conveyor tracking is highly dependent upon the accuracy in specifying the conveyor base frame. In this software release, there are two choices available for base frame calibration of a circular conveyor: 1) Enter the orientation and position of the base frame based on drawings of the robot installation and simple TCP measurements. 2) Use the robot TCP as a measuring tool and measure several points along the conveyor with some trigonometric calculations to calculate the conveyor base frame position and quaternion. In this section, the first choice using a manually calculated quaternion is described. However, the second choice is the recommended approach and is discussed in Section 10.7 Circular Conveyor Base Frame Calibration - TCP Measurement Method. Orientation - Manual Method Definition of the quaternion for conveyor orientation will also define the location of the 0.0 rad point on the circular conveyor. The direction of the X axis will define the 0.0 rad point while the direction of the Z axis will define the direction of positive rotation using the right-hand-rule. The following figure shows two installations, one with clockwise rotation and the other with counterclockwise rotation and the corresponding quaternions. In cases where the 0.0 rad point is not an even multiple of 90 ° from the World frame, calculation of the conveyor orientation quaternion must be done using manual calculations of the quaternion. The TCP can be used to help make measurements, see Section 10.7.
Conveyor Tracking
41
Circular Conveyor Tracking
Direction of Rotation
Conveyor Tracking
QueueTrckDist Direction of Rotation
0.0 rad
X
X
0.0 rad
Y
Y
Xworld
Xworld Yworld
Yworld Quaternion: 0.7071, 0, 0, 0.7071
Quaternion: 0, 0.7071, -0.7071, 0
Figure 9 Circular Conveyor Orientation Quaternions
Base Frame Position and Start Window Start Calibration - Manual Method The conveyor base frame x, y, and z position must be specified relative to the world frame. This position must be calculated from the installation drawings or by using the robot as a measuring tool. Using the robot, one point may be marked on the edge of the circular conveyor and the TCP position is recorded for several points and the centre point of the circle can be found. This is described in detail in the following section.
10.7 Circular Conveyor Base Frame Calibration - TCP Measurement Method It is possible to use TCP measurements and RAPID programs to assist in the calculation of the conveyor base frame position and quaternion. This section outlines the necessary steps for a circular conveyor. Base Frame X, Y, Z Position The following method uses 3 measured points on the circular conveyor to calculate the centre of rotation. The 3 points should be spaced as far apart as possible around the periphery.
42
1.
Use Wobj0 on the Teach Pendant. Pick out a reference point on the circular conveyor, jog the TCP to this point and record p_0.
2.
Run the conveyor to another position. Jog the TCP back to the reference point and record p_1.
3.
Run the conveyor to a third position, jog the TCP back to the reference point and record p_2.
Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
4.
Use the utility function, UTL_cirCntr, with the points p_0, p1, and p_2, to calculate the centre of the circle, p_centre.
5.
Take the X and Y values from p_centre and enter them into the Base Frame values for the Conveyor, converting to meters, see Section 11.3. These are shown in Figure 9. The Z value will be entered later, once the work object zero position has been chosen.
Base Frame Orientation and Start Window Start Calibration The purpose of this section is to define the base frame quaternion and the Z value of the base frame. The base frame quaternion will define where the 0.0 rad point is for the robot motion. The following figure shows an example of the angles that are to be used in defining the base frame orientation for the circular conveyor:
Counter-Clockwise Rotation p_centre X, Y
Base θ Pθ
Synch Switch
p_0 X_0, Y_0
Xworld
TPθ
Qθ 0.0 rad
Qθ = TP θ = Pθ = Base θ =
Queue Tracking Distance angle Angle shown on Teach Pendant Angle calculated from p_0 position. Base frame angle to be converted into a quaternion.
Yworld Figure 10 Example Measurement Points for Base Frame Calculation on a Circular Conveyor
The following procedure can be used to calculate the quaternion for the base frame orientation. 1.
Define a temporary conveyor base frame quaternion as 1, 0, 0, 0
2.
Define a conveyor coordinated work object wobjcnv1
Conveyor Tracking
43
Circular Conveyor Tracking 3.
Conveyor Tracking
Step FWD through a RAPID program containing the two commands: ActUnit CNV1; WaitWObj wobjcnv1;
4.
Run the conveyor until an object passes through the sync switch and beyond the Queue Tracking Distance. The WaitWObj instruction will end execution. Stop the conveyor.
5.
Using wobjcnv1, move the robot Tool Centre Point to the desired zero position on the work object, record this point, p_0. Write down the X_0, Y_0, and Z_0 coordinates of the point p_0 as shown on the Teach Pendant when using the wobjcnv1 work object.
6.
Write down the angle shown in the Jogging Window for the CNV1 conveyor. This is angle TP θ , see Figure 10
7.
Calculate P θ from the X_0 and Y_0 coordinates of p_0 and the atan function. X_0 and Y_0 should both be positive when using the atan function. Check the value, it may be necessary to add 90 degrees: Y_0 P θ = atan ------------- X_0
8.
Calculate the value of
Base θ : Base θ = P θ – TP θ
9.
Calculate the quaternion for the Base frame taking into account the direction of rotation: Counter clockwise rotation: q1 = cos ( Baseθ ⁄ 2 ) q2 = 0.0 q3 = 0.0 q4 = sin ( Base θ ⁄ 2 ) Clockwise rotation: q1 = 0.0 q2 = cos ( Baseθ ⁄ 2 ) q3 = – sin ( Baseθ ⁄ 2 ) q4 = 0.0
10. Enter the value for Z (in meters) from p_0, and the values for the quaternions, q1,
q2, q3, and q4, into the base frame for the Conveyor, see System Parameters, Section 11.3 Topic: Manipulator.
10.8 Conveyor Start Window and Sync Separation For circular conveyor tracking these distances are to be specified in radians.
44
Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
10.9 Conveyor Maximum and Minimum Distances For circular conveyor tracking these distances are to be specified in milliradians.
10.10 Conveyor Adjustment Speed The same as for linear conveyors.
10.11 Motion System Parameters The same as for linear conveyors.
10.12 Motion Mechanical Unit Parameters The same as for linear conveyors.
10.13 Motion Transmission and Single Type The motion configuration of the conveyor must be adjusted to account for a circular motion of the conveyor. There are two parameters that must be adjusted. Under the System Parameters window, • Choose Topics: Manipulator. • Choose Types: Transmission. • Select CNV1 and press Enter
.
• Select the parameter Rotating move and change the value. Parameter Description Rotating move
Specifies if the conveyor is rotating (Yes) or linear (No).
• Press OK to confirm. • Choose Types: Single type. • Select CNV1 and press Enter
.
• Select the parameter Mechanics and change the value. Parameter Mechanics
Conveyor Tracking
Description Specifies the mechanical structure of the conveyor. Choose EXT_ROT
45
Conveyor Tracking System Parameters
Conveyor Tracking
11 Conveyor Tracking System Parameters This section presents a summary of all system parameters that affect conveyor tracking. They are organised by topic as found under the System Parameters window on the Teach Pendant.
11.1 Topic: I/O Signals Topic • Choose Types: Units • Select Encoder and press Enter
46
.
Parameter
Description
CountsPerMeter
Gives the number of quadrature pulses per meter of motion of the conveyor. Should be in the range of 500010000 for linear conveyors.
SyncSeparation
Sync Signal Separation (meters), this distance defines the minimum distance that the conveyor must move after a sync signal before a new sync signal is accepted as a valid object.
QueueTrckDist
Queue Tracking Distance (meters), this distance defines the placement of the synchronization switch relative to the 0.0 meter point on the conveyor. The encoder unit tracks all objects in this distance but does not allow connection until an object has passed 0.0 meters.
StartWinWidth
Start Window Width (meters), this distance defines the size of the start window. All objects within this window are tracked and are eligible for use in a coordinated work object. A WaitWObj instruction will connect to the first object in the window.
IIRFPeriod
Internal Use: Specifies the period of the speed filter on the encoder unit, must be the same as the PollRate.
IIRFNoOfPoles
Internal Use: Specifies the number of poles in the Infinite Impulse Response (IIR) speed filter.
IIRFNoOfZeros
Internal Use: Specifies the number of zeros in the speed filter.
IIRFXfrmMetPol
Internal Use: Specifies the transform method for discreting the speed filter coefficients for the filter poles.
IIRFXfrmMetZero
Internal Use: Specifies the transform method for discreting the speed filter coefficients for the filter zeros.
IIRFFZ
Internal Use: Specifies the location of the real part of the zeros in the left-half plane (in Hz) when zeros have been given. Conveyor Tracking
Conveyor Tracking
Conveyor Tracking System Parameters
IIRFDZ
Internal Use: Specifies the damping of the zeros and thus the imaginary portion of the zero location in the left-half plane.
IIRFFP
Specifies the location of the real part of the poles in the left-half plane (in Hz). This is the break frequency for the speed filters in the encoder unit and regulates how hard the speed is filtered in the encoder unit.
IIRFDP
Internal Use: Specifies the damping of the poles and thus the imaginary portion of the zero location in the left-half plane.
IIRFGain
Internal Use: Specifies gain of the speed filter. Must be 1.0
FIRLengh
Internal Use: Specifies the length of the Finite Impulse Response (FIR) filter on the position.
FIRB0
Internal Use: Specifies the weight on the first coefficient in the FIR position filter.
FIRB1
Internal Use: Specifies the weight on the second coefficient in the FIR position filter.
11.2 Topic: Process • Choose Types: Conveyor Systems. • Select CONVEYOR1 and press Enter Parameter
.
Description
Adjustment Speed
The speed (in mm/s) at which the robot should catch up to the conveyor for the first point coordinated to the conveyor position. It must be higher than the conveyor speed or the robot may never catch up to the conveyor.
Minimum distance
The minimum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is produced.
Maximum distance
The maximum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is generated.
Conveyor Tracking
47
Conveyor Tracking System Parameters
Conveyor Tracking
• Choose Types: CAN Sensors. • Select CAN1 and press Enter Parameter
.
Description
Signal delay
Internal Use: The delay (in milliseconds) for adjusting the prediction time of the conveyor position using the conveyor speed.
Connected signal
Name of the digital input signal for connection.
Position signal
Name of the analog input signal for conveyor position.
Velocity signal
Name of the analog input signal for conveyor speed.
Null speed signal
Name of the digital input signal indicating zero speed on the conveyor.
Data ready signal
Name of the digital input signal indicating a poll of the encoder unit.
WaitWObj signal
Name of the digital output signal to indicate that a connection is desired to an object in the queue.
DropWObj signal
Name of the digital output signal to drop a connected object on the encoder unit.
PassStartW signal
Name of the digital input signal to indicate that an object has gone past the start window without being connected.
11.3 Topic: Manipulator • Choose Types: Motion system. • Select system_1and press Enter
.
Parameter Description Path resolution
The period at which steps along the path are calculated.
Process update time The time (in seconds) at which the conveyor process updates the robot kinematics on the conveyor position. • Choose Types: Mechanical Unit • Select CNV1 and press Enter Parameter
.
Description
Name The name of the unit (max. 7 characters). This name will subsequently be used in the Jogging window and from the program, e.g. when an unit is to be activated.
48
Activate at start up
The conveyor is to be activated automatically at start up.
Do not allow deact.
The conveyor cannot be deactivated.
Conveyor Tracking
Conveyor Tracking
Conveyor Tracking System Parameters
• Choose Types: Single. • Select CNV1 and press Enter Parameter
.
Description
Base frame x The X-coordinate of the conveyor’s base coordinate system’s position in relation to the world coordinate system (in metres). Base frame y metres).
The Y-coordinate of the conveyor’s base coordinate system (in
Base frame z metres).
The Z-coordinate of the conveyor’s base coordinate system (in
Base frame q1-q4 The orientation of the conveyor base coordinate system in relation to the world coordinate system (expressed in quaternions q1-q4).
• Choose Types: Single type. • Select CNV1 and press Enter
.
Parameter Description Mechanics Specifies the mechanical structure of the conveyor.
• Choose Types: Transmission. • Select CNV1 and press Enter Parameter Rotating move
Conveyor Tracking
.
Description Specifies if the conveyor is rotating (Yes) or linear (No).
49
Conveyor Tracking System Parameters
50
Conveyor Tracking
Conveyor Tracking
Index
A Activating the Conveyor 14 Additional Features for the DSQC 354 Revision 2 23 B BaseFrame 31 C Calibration of Counts per Meter 29, 40 Circular Conveyor Base Frame Calibration Manual Method 41 common drive unit 20, 22 Configuration for Track Motion following Conveyor 37 Connecting the DSQC 354 to S4C Cabinet 26 Conveyor Adjustment Speed 45 Conveyor Base Frame Calibration 30 Conveyor Maximum and Minimum Distances 35, 45 Conveyor Setup and Calibration 28 Conveyor Start Window and Sync Separation 34, 44 Coordinate Systems 12 D DeactUnit 20, 22 Defining a Conveyor Coordinated Work Object 14 Defining the Queue Tracking Distance 30, 40 Direction of Positive Motion from Encoder 28, 40 Drop Work Object on Conveyor 22 Dropping a Work Object 16 DropWObj 22 E Encoder Connection to DSQC 354 25 Encoder Location 25 Encoder Type Selection 24 Encoder Type Selection and Location 39 Entering and Exiting Conveyor Tracking
Conveyor Tracking
Motion in Corner Zones 16 external axes deactivate 20, 22 F Features 6 Finepoint Programming 18 H Hardware Configuration and Connections 23 I Information on Teach Pendant 17 Installation of 2 Conveyors 28 Introduction 5 L Limitations 8 M mechanical unit deactivate 20, 22 Modes of Operation 18 Motion Mechanical Unit Parameter 37 Motion Mechanical Unit Parameters 45 Motion System Parameters 36, 45 Motion Transmission and Single Type 45 Motor parameters 35, 36, 37, 45, 47, 48, 49 O Operation under AUTO 18 Operation under Manual Full Speed Mode (100%) 19 Operation under Manual Reduced Speed Mode ( 18 Overview of Conveyor Tracking 5 P Physical Components 6 Principles of Conveyor Tracking in S4C 9 Programming Considerations 17 Programming Conveyor Tracking 13 51
Index
Programming the Conveyor Coordinated Motion 15 R Robot Adjustment Speed 35 S Software Installation 27, 40 Start Window and Queue Tracking Distance 10 Synchronization Switch 25 T TCP Measurement Method 42 Topic I/O Signals Topic 46 Manipulator 48 Process 47 W Wait for Work Object on Conveyor 20 Waiting for a Work Object 15 WaitWObj 20 Working with the Object Queue 13
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Conveyor Tracking
Notes:
ABB Robotics AB DPT / MT S-721 68 VÄSTERÅS SWEDEN Telephone: +46 (0) 21 34 40 00 Telefax: +46 (0) 21 13 25 92
Art.nr 3HAC 5750-1
CONTENTS Page 1 Introduction ......................................................................................................................5 2 Overview of Conveyor Tracking.....................................................................................5 2.1 Physical Components ............................................................................................. 6 2.2 Features................................................................................................................... 6 2.3 Limitations.............................................................................................................. 8 3 Principles of Conveyor Tracking in S4C........................................................................9 3.1 Start Window and Queue Tracking Distance.......................................................... 10 3.2 Coordinate Systems ................................................................................................ 12 4 Programming Conveyor Tracking..................................................................................13 4.1 Working with the Object Queue ............................................................................. 13 4.2 Activating the Conveyor......................................................................................... 14 4.3 Defining a Conveyor Coordinated Work Object .................................................... 14 4.4 Waiting for a Work Object...................................................................................... 15 4.5 Programming the Conveyor Coordinated Motion .................................................. 15 4.6 Dropping a Work Object......................................................................................... 16 4.7 Entering and Exiting Conveyor Tracking Motion in Corner Zones ....................... 16 4.8 Information on Teach Pendant................................................................................ 17 4.9 Programming Considerations ................................................................................. 17 4.10 Finepoint Programming........................................................................................ 18 4.11 Modes of Operation .............................................................................................. 18 5 RAPID Instructions .........................................................................................................20 5 WaitWObj - Wait for Work Object on Conveyor .........................................................20 5 5 5 5
Example ..................................................................................................................... 20 Arguments ................................................................................................................. 20 Program execution..................................................................................................... 20 Examples ................................................................................................................... 20
5 Limitations................................................................................................................. 21 5 Error handling............................................................................................................ 21 5 Syntax ........................................................................................................................ 21 5 DropWObj - Drop Work Object on Conveyor..............................................................22 5 5 5 5 5
Example ..................................................................................................................... 22 Arguments ................................................................................................................. 22 Program execution..................................................................................................... 22 Limitations................................................................................................................. 22 Syntax ........................................................................................................................ 22
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6 Additional Features for the DSQC 354 Revision 2 ....................................................... 23 7 Hardware Configuration and Connections ................................................................... 23 7.1 7.2 7.3 7.4 7.5
Encoder Type Selection.......................................................................................... Encoder Location ................................................................................................... Encoder Connection to DSQC 354 ........................................................................ Synchronization Switch.......................................................................................... Connecting the DSQC 354 to the S4C Cabinet......................................................
24 25 25 25 26
8 Software Installation........................................................................................................ 27 8.1 Installation of 2 Conveyors .................................................................................... 28 9 Conveyor Setup and Calibration .................................................................................... 28 9.1 Direction of Positive Motion from Encoder........................................................... 28 9.2 Calibration of Counts per Meter............................................................................. 29 9.3 Defining the Queue Tracking Distance .................................................................. 30 9.4 Conveyor Base Frame Calibration ......................................................................... 9.5 Conveyor Start Window and Sync Separation ....................................................... 9.6 Conveyor Maximum and Minimum Distances ...................................................... 9.7 Robot Adjustment Speed........................................................................................ 9.8 Motion System Parameters..................................................................................... 9.9 Motion Mechanical Unit Parameters...................................................................... 9.10 Configuration for Track Motion following Conveyor..........................................
30 34 35 35 36 37 37
10 Circular Conveyor Tracking......................................................................................... 39 10.1 Encoder Type Selection and Location.................................................................. 10.2 Software Installation............................................................................................. 10.3 Direction of Positive Motion from Encoder......................................................... 10.4 Calibration of Counts per Meter........................................................................... 10.5 Defining the Queue Tracking Distance ................................................................ 10.6 Circular Conveyor Base Frame Calibration - Manual Method ............................ 10.7 Circular Conveyor Base Frame Calibration - TCP Measurement Method .......... 10.8 Conveyor Start Window and Sync Separation ..................................................... 10.9 Conveyor Maximum and Minimum Distances .................................................... 10.10 Conveyor Adjustment Speed.............................................................................. 10.11 Motion System Parameters................................................................................. 10.12 Motion Mechanical Unit Parameters.................................................................. 10.13 Motion Transmission and Single Type...............................................................
39 40 40 40 40 41 42 44 45 45 45 45 45
11 Conveyor Tracking System Parameters....................................................................... 46 11.1 Topic: I/O Signals Topic....................................................................................... 46
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Coveyor Tracking Page
11.2 Topic: Process ....................................................................................................... 47 11.3 Topic: Manipulator ............................................................................................... 48
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Conveyor Tracking
Conveyor Tracking
Introduction
1 Introduction This document contains a description of the Conveyor Tracking functionality for S4C. Conveyor Tracking, or Line Tracking, is the function whereby the robot follows a work object which is mounted on a moving conveyor. This document describes how a conveyor tracking application is installed, programmed, and operated. The document is organised as follows: Section 2 presents an overview of the conveyor tracking features and necessary physical components. Section 3 describes the principles of conveyor tracking in S4C, the coordinate systems, and object queues. Section 4 provides information on how conveyor tracking is to be programmed. Section 5 presents the new RAPID instructions. Section 6 describes the features available with the Revision 2 of the DSQC 354. Sections 7 and 8 present information on the hardware requirements and software installation. Section 9 goes through the configuration and calibration of a linear conveyor. Section 10 marks the differences for configuration and calibration of a circular conveyor. Finally, a complete listing of all conveyor system parameters is provided in Section 11 . Follow Section 9 Conveyor Setup and Calibration for the steps in configuring a standard linear conveyor.
2 Overview of Conveyor Tracking In conveyor tracking, the robot’s Tool Centre Point (TCP) will automatically follow a work object that is defined on the moving conveyor. While tracking the conveyor the S4C will maintain the programmed TCP speed relative to the work object even if the conveyor runs at different speeds.
Conveyor Tracking
5
Overview of Conveyor Tracking
Conveyor Tracking
2.1 Physical Components Sync Switch Conveyor Encoder
Encoder Unit DSQC 354
IRB robot S4C Controller Figure 1 Physical Components in Conveyor Tracking
The S4C solution for conveyor tracking consists of the following components: S4C Controller and IRB robot 24V Encoder Option 285, DSQC 354 Encoder Interface Unit, Original or Revision 2. Synchronization Switch, indicating object presence on conveyor Conveyor The encoder and synchronization switch are connected to the DSQC 354. One encoder can be connected to several Encoder Interface Units but each S4C controller must have a DSQC 354 if more than one robot is to track the conveyor.
2.2 Features The S4C conveyor tracking option provides the following features: Accuracy: In Auto operation, at 150 mm/s constant conveyor speed, the Tool Centre Point (TCP) of the robot will stay within +/- 2 mm of the path as seen with no conveyor motion. This is valid as long as the robot is within its dynamic limits with the added conveyor motion. This figure depends upon the calibration of the robot and conveyor and is applicable for linear conveyor tracking only. Object Queue: The DSQC 354 Encoder Interface Unit will maintain a queue of up to 254 objects that have passed the synchronization switch.
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Conveyor Tracking
Conveyor Tracking
Overview of Conveyor Tracking
Start Window: A program can choose to wait for an object that is within a window past the normal starting point, or wait for an object to pass a specific distance, or immediately take the first object in the object tracking queue. Objects that go beyond the start window are automatically skipped. RAPID Access to Queue and Conveyor Data: A RAPID program has access to the number of objects in the object queue, and the current position and speed of the conveyor. A RAPID program may also remove the first object in the tracking queue or all objects in the queue. Maximum Distance: A maximum tracking distance may be specified to stop the robot from tracking outside of the working or safety area. Track follows Conveyor If the robot is mounted on a linear track, then the system can be configured such that the track will follow the conveyor and maintain the relative position to the conveyor. The TCP speed relative the work object on the conveyor will still be the programmed speed. Enter and Exit Conveyor Tracking in Corner Zones It is possible to enter and exit conveyor tracking via corner zones as well as via fine points. Using corner zones allows a minimum cycle time to be achieved. Exit and Re-enter Conveyor Tracking to Same Object It is possible to exit and re-enter to the same object on the conveyor unlimited times until the object moves outside the working area, reaches the maximum distance, or is explicitly dropped by the RAPID program. Multiple Conveyors Up to 2 conveyors are supported via the standard option. Each conveyor must have a DSQC 354. Coordinated Finepoint A finepoint may be programmed while making motions relative to the conveyor. This conveyor coordinated finepoint will ensure that the robot stops moving relative to the conveyor and will follow the conveyor while the RAPID program continues execution. The robot will hold the position within +/- 0.7 mm depending upon calibration of the robot and conveyor. Calibration of Linear Conveyors A calibration method is provided for easy calibration of the position and direction of the conveyor motion in the robot’s workspace. The linear conveyor may take any position and orientation. Conveyor Tracking
7
Overview of Conveyor Tracking
Conveyor Tracking
2.3 Limitations Small Orientation Error with SingArea\Wrist There can be a small orientation error of the TCP while following the conveyor and make long motions with SingArea\Wrist. This error can be eliminated by making several short motions with SingArea\Wrist. Track Parallel to Conveyor If the robot is mounted on a track and the track is to be used to follow the conveyor motions, then the track and conveyor must be parallel. The motion on the track and the motion on the conveyor must have the same direction of positive motion. See Section 9.10 Configuration for Track Motion following Conveyor. Calibration of Circular Conveyors There are no built-in methods for the calibration of circular conveyors. This limitation can be relaxed if the user is willing to calculate a quaternion orientation manually or with other tools during base frame calibration. Limitation on External Axes Each conveyor is considered an external axis. Thus the system limitation of 6 active external axes must be reduced by the number of active and installed conveyors. The first installed conveyor will use measurement node 6 and the second conveyor will use measurement node 5. These measurement nodes are not available for external axes and no resolvers should be connected to these nodes on any external axes measurement boards. Object Queue Lost on Warm Start or Power Failure The object queue is kept on the DSQC 354. If the system is restarted with a Warm Start or if the power supply to either the S4C controller or the DSQC 354 fails, then the object queue will be lost. Minimum and Maximum Speed There is a minimum conveyor speed in order to maintain smooth and accurate motions. This speed is dependent upon the encoder selection and can vary from 4 mm/s to 8 mm/ s. See Minimum and Maximum Counts per Second under 7.1 Encoder Type Selection. There is no explicit maximum speed for the conveyor. Accuracy will degrade at speeds above the specification and with high speed robot motions or with very high conveyor speeds (> 500 mm/s) and the robot will no longer be able to follow the conveyor. WaitWObj after DropWObj If a WaitWObj instruction is used immediately after a DropWObj instruction, it may be necessary to add a WaitTime 0.1; after the DropWObj instruction.
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Conveyor Tracking
Conveyor Tracking
Principles of Conveyor Tracking in S4C
3 Principles of Conveyor Tracking in S4C Conveyor Tracking is built upon the coordinated work object concept taken from coordinated motion with external axes. See User’s Guide, Chapter 10 Calibration, Section 2 Coordinated Axes for additional information. Conveyor as a Mechanical Unit Primary to this concept is the treatment of the conveyor as a mechanical unit. For the S4C, the conveyor is a mechanical unit with all features of a mechanical unit except that it is not under control of the S4C controller. As a mechanical unit it may be activated, deactivated, the position of the conveyor appears in the Teach Pendant Jogging Window and in the robtarget when a MODPOS operation is performed. Conveyor Coordinated Work Object For conveyor tracking, the robot movements are coordinated to the movements of a user frame connected to the conveyor mechanical unit. E.g. a user frame is placed on the conveyor and connected to its movements. An work object is used for this purpose and it is marked with the name of the conveyor mechanical unit, and that the work object is moveable. The conveyor tracking coordination will be active if the mechanical unit is active, and the conveyor coordinated work object is active. When the conveyor coordinated work object is used, in jogging or in a move instruction, the data in the “uframe” component will be ignored and the location of the user coordinate system will only depend on the movements of the conveyor mechanical unit. However the “oframe” component will still work giving an object frame related to the user frame and also the displacement frame may be used. Waiting for a Work Object on the Conveyor The difference between a conveyor coordinated work object and a work object that is coordinated to another type of mechanical unit is that there is no work object for coordination until an object appears on the conveyor. Before the robot can coordinate the TCP positions to a conveyor, there must be a work object present on the conveyor. Work objects on the conveyor are detected by means of the synchronization switch that is connected to the DSQC 354 Encoder Interface Unit. This unit will track all objects that have gone past the synchronization switch and are within specified distances in the work area. Before starting coordinated motion with the conveyor, the RAPID program must first check with the Encoder Interface Unit whether or not there is a work object available on the conveyor. If an object is available then execution continues and the motions may use the coordinated work object. If there is no object, then the RAPID program waits until a work object is available. Connecting to a Work Object The RAPID instruction WaitWObj, see Section 5 RAPID Instructions below for more details, is used to wait for a work object on the conveyor before starting conveyor coordinated motion. When the WaitWObj instruction is successful then the conveyor work object is said to be “connected” to the RAPID program.
Conveyor Tracking
9
Principles of Conveyor Tracking in S4C
Conveyor Tracking
Once a RAPID program has connected to a work object on the conveyor then robot motion instructions and jogging commands may use this work object just as any other work object. When using the conveyor connected coordinated work object then all motions are relative to the work object on the conveyor. The user may change work objects several times and thus coordinate the robot to other work objects in the system and still return to the conveyor coordinated work object. Disconnecting from a Work Object The S4C controller and Encoder Interface Unit will maintain the connection to the work object until one of the following events occurs: A DropWObj instruction is issued, the Maximum Distance, as defined for the conveyor, is reached, restart of the controller, power supply failure to either the Encoder Interface Unit or controller. The connection to the work object will not be lost with deactivation of the conveyor mechanical unit and will return upon re-activation. The DropWObj instruction is used to end the connection before the Maximum Distance is reached. After a DropWObj instruction is issued it is possible to immediately wait for and connect to the next work object in the conveyor object queue. If a DropWObj instruction is not issued, then the object will be automatically disconnected and dropped when the Maximum Distance is reached.
3.1 Start Window and Queue Tracking Distance The S4C controller and DSQC 354 will maintain the object queue based upon a set of distances relative to the conveyor and synchronization switch. The following figure shows these relationships:
Work Object User Frame
Synchronization Switch 7
6
5
Minimum Dist.
4 Start Window Width
0.0 m
y
3
2
1
x
Conveyor Direction
Working Area Maximum Distance
Queue Track. Dist.
-
z
+
Figure 2 Relationships between Distances along the Conveyor
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Conveyor Tracking
Conveyor Tracking
Principles of Conveyor Tracking in S4C
Queue Tracking Distance
This distance defines the placement of the 0.0 meter point relative to the synchronisation switch on the conveyor. The Encoder Interface Unit tracks all objects in this distance. The position returned from the Encoder unit for the object will be negative, relative to the 0.0 m point.
Start Window Width
This distance defines the start window. The start window defines the area that if a program starts using an object within the window, then all program coordination can end before the Maximum Distance or work area is reached. All objects within this window are tracked and are eligible for use in a coordinated work object. A WaitWObj instruction will connect to the first object in the window.
Maximum Distance
This distance is the maximum distance that a connected object may have before being automatically dropped. If an object is dropped, then any coordinated motions are terminated with an error message.
Minimum Distance
This is the minimum distance that a connected object may have before being automatically dropped. If the conveyor stops and runs backwards, then there will be an automatic drop when the connected object goes past the minimum distance. This may be greater than or less than the Queue Tracking Distance.
Using the above distance definitions the conditions and states of objects 1...7 in Figure 2 may be described: Object 1
This object is connected as indicated by the coordinate frame attached to the object’s position on the conveyor.
Object 2
Object 2 is outside the start window and is no longer tracked by the Encoder unit. This object will be skipped and cannot be connected by a WaitWObj instruction. It is skipped because the conveyor speed is such that coordination with the object could not be completed before the object moved outside the maximum distance or work area of the robot.
Objects 3 and 4
These objects are within the start window and are tracked by the Encoder unit. If Object 1 was dropped via a DropWObj instruction then Object 3 would be the next object to be connected when a WaitWObj instruction was issued. Because Objects 3 and 4 were in the start window, the WaitWObj instruction will not wait but return immediately with object 3.
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Principles of Conveyor Tracking in S4C
Conveyor Tracking
Objects 5 and 6
These objects lie within the queue tracking distance and are tracked by the Encoder unit. If objects 3 and 4 were not present, then a WaitWObj instruction would stop program execution until object 5 entered the start window.
Object 7
This object has not yet passed the synchronization switch and has not yet been registered by the Encoder Interface Unit.
3.2 Coordinate Systems
Synchronization Switch
z
z
User Frame
Object Frame x
y
x Base Frame (conveyor) Minimum Dist.
y
z
y
Conveyor Direction
x
Start Window Width Maximum Distance
Queue Track. Dist.
0.0 m
z
z y x World Frame
x y Base Frame (Robot)
Figure 3 Conveyor Tracking Coordinate Systems
The above figure shows the principle coordinate frames used in conveyor tracking. The table below provides an overview of these coordinate frames
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Coordinate System
Defined Where
Base Frame of robot
Service/View: BaseFrame.
Relative to
Base frame definition of robot gives relation between world and base frame.
World Frame
World Frame
No definition needed
Nothing
Base Frame of conveyor
Defined from measurements using robot. See Installation and Calibration below.
World Frame
Conveyor Tracking
Conveyor Tracking
Principles of Conveyor Tracking in S4c
Coordinate System
Defined Where
Relative to
User Frame, coordinated to conveyor
Program/View: Data Types - wobjdata Select conveyor mechanical unit
World Frame via Base Frame of conveyor.
Program/View: Data Types - wobjdata
User Frame
Object Frame (not shown)
The two key frames in conveyor tracking are the Base Frame of the conveyor and the User Frame in the conveyor coordinated work object. The position of User Frame in the conveyor coordinated work object is determined from the position of the conveyor Base Frame and the linear position of the conveyor in meters. The DSQC 354 Encoder Interface Unit provides the position of the conveyor relative the synchronization switch and the Queue Tracking Distance. When the encoder unit sends a value of 0.0 meters to the S4C controller, then the User Frame for the conveyor coordinated work object is coincident with the Base Frame of the conveyor. As the conveyor moves, then the User Frame in the conveyor coordinated work object moves along the X-axis of the conveyor Base Frame.
4 Programming Conveyor Tracking In order to make a program that uses conveyor tracking and a conveyor coordinated work object, one must first make sure that a work object is present within the start window of the Encoder Interface Unit. To accomplish this an object must be moved past the synchronization switch and into the start window. If there are several objects already on the conveyor, then it may be necessary to first clear the object queue and then move the conveyor.
4.1 Working with the Object Queue The S4C conveyor option provides several I/O signals which allow a user or RAPID program to monitor and control the Object Queue on the encoder unit. The following table shows the I/O signals which impact the Object Queue.
I/O Signal
Description
c1ObjectsInQ
Group input showing the number of objects in the Object Queue. These objects have passed the synchronization switch but have not gone outside the startwindow.
c1Rem1PObj
Remove First Pending Object from the Object Queue. Setting this signal will cause the first pending object to be dropped from the Object Queue. Pending objects are objects that are in the queue but are not connected to a work object.
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Programming Conveyor Tracking
Conveyor Tracking
c1RemAllPObj
Remove All Pending Objects. Setting this signal will cause the Encoder Interface Unit to empty all objects from the Object Queue. If an object is connected, then it is not removed.
c1DropWObj
Setting this signal will cause the encoder unit to drop the tracked object and disconnect that object. The object is removed from the queue.
4.2 Activating the Conveyor As an external axis and mechanical unit the conveyor must be activated before it may be used for work object coordination. The usual ActUnit instruction is used to activate the conveyor and DeactUnit may be used to deactivate the conveyor. By default, the conveyor is installed non-active on start. If desired, the conveyor may be configured to be always active upon start. See Section 9.9 Motion Mechanical Unit Parameters below. Automatic Connection upon Activation: When a conveyor mechanical unit is activated, it first checks the state of the encoder unit to see whether the object was previously connected. If the encoder unit, via the I/ O signal c1Connected, indicates connection, then the object on the conveyor will automatically be connected upon activation. The purpose of this feature is to automatically reconnect in case of a power failure with power backup on the Encoder Interface Unit.
4.3 Defining a Conveyor Coordinated Work Object From the programming window, view the wobjdata and create a new work object, wobjcnv1. Set the ufprog and ufmec as follows: ufprog
(user frame programmed)Data type: bool
Defines whether or not a fixed user coordinate system is used: - FALSE-> Movable user coordinate system, i.e. coordinated to conveyor. ufmec
(user frame mechanical unit)Data type: string
The conveyor mechanical unit with which the robot movements are coordinated. Specified with the name that is defined in the system parameters, e.g. “CNV1”.
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Programming Conveyor Tracking
4.4 Waiting for a Work Object Motions that are to be coordinated to the conveyor can not be programmed until an object on the conveyor has been connected via a WaitWObj instruction. If the object on the conveyor is already connected from a previous WaitWObj or if connection was established during activation, then execution of a 2nd WaitWObj instruction will cause an error. This error can be handled in an error handler if desired. The details of the WaitWObj are given in Section 5 RAPID Instructions.
4.5 Programming the Conveyor Coordinated Motion 1.
Create a program with the following instructions: ActUnit CNV1; ConfL/Off; MoveL waitp, v1000, fine, tool; WaitWObj wobjcnv1;
2.
Single-step the program past the WaitWObj instruction. If there is an object already in the start window on the conveyor then the instruction will return, else execution will stop while waiting for an object on the conveyor.
3.
Run the conveyor until an object passes the sync signal. The program should exit the WaitWObj and is now ‘connected’ to the object. Stop the conveyor with the object in an accessible portion of the workspace.
4.
Teach the MoveL, MoveC, PaintL, or PaintC instructions using the wobjcnv1 conveyor coordinated work object.
5.
End the coordinated motion with a fixed-frame work object (not coordinated to the conveyor). Note that this is the only way to end the use of the work object.
6.
Program a DropWObj wobjcnv1; instruction
7.
If this is the end of the program, or the conveyor is no longer needed, then program a DeactUnit CNV1; instruction.
Example: The following program shows an example for a conveyor tracking program. ConfL\Off; MoveJ p0, vmax, fine, tool1; ActUnit CNV1; WaitWObj wobjcnv1; MoveL p10, v1000, z1, tool1\Wobj:=wobjcnv1; MoveL p20, v1000, z1, tool1\Wobj:=wobjcnv1; MoveL p30, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p40, v500, fine, tool1; DropWObj wobjcnv1; MoveL p0, v500, fine; DeactUnit CNV1; Conveyor Tracking
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Programming Conveyor Tracking
Conveyor Tracking
4.6 Dropping a Work Object A connected work object may be dropped once conveyor coordinated motion has ended. It is important to make sure that the robot motion is no longer using the conveyor positions when the work object is dropped. If motion still requires the positions then a Stop will occur when the object is dropped. Conveyor coordinated motion does not end in a finepoint. As long as the work object is coordinated to the conveyor, the robot motion will be coupled to the conveyor even in a finepoint. A fixed-frame or non-conveyor work object must be used in a motion instruction before dropping the conveyor work object. Care must be taken when ending coordination in a corner zone and executing the DropWObj instruction as the work object will be dropped before the robot has left the corner zone and the motion still requires the conveyor coordinated work object. It is not necessary to be connected in order to execute a DropWObj instruction. No error will be returned if there was no connected object.
4.7 Entering and Exiting Conveyor Tracking Motion in Corner Zones Once a WaitWObj instruction has connected to a work object on the conveyor then it is possible to enter and exit coordinated motion with the conveyor via corner zones. The following is an example: MoveL p10, v1000, fine, tool1; WaitWObj wobjcnv1; MoveL p20, v1000, z50, tool1; - enter coordination in zone MoveL p30, v500, z1, tool1\Wobj:=wobjcnv1; MoveL p40, v500, z1, tool1\Wobj:=wobjcnv1; MoveL p50, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p60, v1000, z50, tool1; - exit coordination in zone MoveL p70, v500, fine, tool1; DropWObj wobjcnv1; MoveL p10, v500, fine, tool1; The move instruction ending coordination must be a ‘fixed’ work object. e.g. ufprog is TRUE. As noted above, care must be taken when exiting coordination in a corner zone and executing a DropWObj instruction. The following example shows an incorrect method for ending coordination in corner zones: ... MoveL p50, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p60, v1000, z50, tool1; - exit coordination in zone DropWObj wobjcnv1; - ERROR, work object is dropped while robot is still in corner zone.
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Conveyor Tracking
Conveyor Tracking
Programming Conveyor Tracking
4.8 Information on Teach Pendant The user has access to the conveyor position and speed via the Teach Pendant. Jog Window: The position in millimeters of the conveyor object is shown in the jog window. This value will be negative if a Queue Tracking Distance is defined. When an object passes the synchronization switch then the position will be automatically updated in the jog window. I/O Window: From the I/O Window the user has access to all the signals that are defined on the Encoder Interface Unit. From this window it is possible to view the conveyor position in meters, and the conveyor speed in meters/s. The speed will be 0 m/s until an object has passed the synchronization switch.
4.9 Programming Considerations Performance Limits Conveyor tracking will be lost if joint speed limits are reached, particularly in singularities. It is the responsibility of the programmer to ensure that the path during tracking does not exceed the robots speed and motion capabilities. Motion Commands Only Linear and Circular motion commands are allowed for conveyor tracking. Change of Tool Changing the tool is not allowed during conveyor tracking as the motion during a tool change is a joint motion. Finepoints Finepoints are allowed during conveyor tracking. The robot will hold the TCP still relative to the conveyor and RAPID execution will continue, see Section 4.10 Finepoint Programming below. ConfL The RAPID instruction ConfL\Off must be executed before coordination with the conveyor. The purpose is to avoid configuration errors that would otherwise occur as the robot changes configuration during conveyor tracking.
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Programming Conveyor Tracking
Conveyor Tracking
Other RAPID Limitations The commands, StorePath, RestoPath do not function during conveyor tracking. No Search commands function during conveyor tracking. EoffsSet, EoffsOn, EoffsOff have no effect for the conveyor external axis.
4.10 Finepoint Programming While tracking the conveyor it is possible to use a finepoint. The following program example shows how motion may be stopped with respect to the conveyor so that an I/O signal may be set: WaitWObj wobjcnv1 MoveL p1, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p2, v500, fine, tool1\Wobj:=wobjcnv1; SetDO release_gripper; WaitTime 0.1; MoveL p3, v500, z20, tool1\Wobj:=wobjcnv1; MoveL p4, v500, fine, tool1; DropWObj wobjcnv1; In the above example the SetDO will be executed after the robot arrives at p2. The robot will then track the conveyor for 0.1 seconds while the WaitTime instruction is executed. It will then move to p3 and on to p4 via a corner zone before ending coordination with a fixed work object (wobj0 in this case).
4.11 Modes of Operation Operation under Manual Reduced Speed Mode (< 250 mm/s) When the conveyor is not moving, then the FWD, BWD buttons may be used to step through the program. New instructions may be added and MODPOS may be used to modify programmed positions. In order to facilitate programming, the conveyor may be moved to new positions between instructions. The robot will return to the correct position when FWD or BWD is pressed. The robot will recover as normal if the Enable switch is released during motion. The robot cannot perform coordinated motions to the conveyor while in Manual Reduced Speed mode and the conveyor is moving. Operation under AUTO Once a WaitWObj instruction has been executed, then it is no longer possible to step through the program with FWD and BWD while the conveyor is moving.
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Conveyor Tracking
Conveyor Tracking
Programming Conveyor Tracking
Start/Stop The robot will stop and no longer track the conveyor if the STOP button is pressed or Stop, StopMove RAPID instructions are executed between the WaitWObj and DropWObj instructions. The conveyor coordinated work object will not be lost but if the conveyor is moving then the object will quickly move out of the working area. RESTART from the current instruction is not possible and the program must be restarted from either from MAIN or a WaitWObj instruction.
Emergency Stop/Restart When the Emergency Stop is pressed the robot will stop immediately. If the program was stopped after a WaitWObj then the coordinated work object will not be lost but if the conveyor is moving then the object will quickly move out of the working area. RESTART from the current instruction is not possible and the program must be restarted either from MAIN or a WaitWObj instruction. Operation under Manual Full Speed Mode (100%) Operation under Manual (100%) is similar to operation under AUTO. The program may be run by holding the START button, but once a WaitWObj instruction has been executed then it is no longer possible to step through the program with the FWD and BWD buttons while the conveyor is moving.
Stop/Restart When the START button is released, or Emergency Stop is pressed, the robot will stop immediately. If the program was stopped after a WaitWObj then the coordinated work object will not be lost but if the conveyor is moving then the object will quickly move out of the working area. RESTART from the current instruction is not possible and the program must be restarted either from MAIN or a WaitWObj instruction.
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RAPID Instructions
Conveyor Tracking
5 RAPID Instructions WaitWObj
Wait for Work Object on Conveyor
WaitWObj (Wait Work Object) connects to a work object in the start window on the conveyor mechanical unit.
Example WaitWObj wobj_on_cnv1; The program connects to the first object in the object queue that is within the start window on the conveyor. If there is no object in the start window then execution stops and waits for an object.
Arguments WaitWObj WObj
WObj [ \RelDist ] (Work Object)
Data type: wobjdata
The moving work object (coordinate system) to which the robot position in the instruction is related. The mechanical unit conveyor is to be specified by the ufmec in the work object. [ \RelDist ]
(Relative Distance)
Data type: num
Waits for an object to enter the start window and go beyond the distance specified by the argument. If the work object is already connected, then execution stops until the object passes the given distance. If the object has already gone past the Relative Distance then execution continues.
Program execution If there is no object in the start window then program execution stops. If an object is present, then the work object is connected to the conveyor and execution continues. If a second WaitWObj instruction is issued while connected then an error is returned unless the \RelDist optional argument is used.
Examples WaitWObj wobj_on_cnv1\RelDist:=500.0; If not connected, then wait for the object to enter the start window and then wait for the object to pass the 500 mm point on the conveyor. If already connected to the object, then wait for the object to pass 500 mm.
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Conveyor Tracking
Conveyor Tracking
RAPID Instructions
WaitWObj wobj_on_cnv1\RelDist:=0.0; If not connected, then wait for an object in the start window. If already connected, then continue execution as the object has already gone past 0.0 mm.
WaitWObj wobj_on_cnv1; WaitWObj wobj_on_cnv1\RelDist:=0.0; The first WaitWObj connects to the object in the start window. The second WaitWObj will return immediately if the object is still connected, but will wait for the next object if the previous object had moved past the Maximum Distance or was dropped.
Limitations It requires 100 ms to connect to the first object in the start window. Once connected, a second WaitWObj with \RelDist optional argument will take only normal RAPID instruction execution time.
Error handling If following errors occurs during execution of the WaitWobj instruction, the system variable ERRNO will be set. These errors can then be handled in the error handler. ERR_CNV_NOT_ACTThe conveyor is not activated. ERR_CNV_CONNECTThe WaitWobj instruction is already connected. ERR_CNV_DROPPEDThe object that the instruction WaitWobj was waiting for has been dropped by another task. (DSQC 354Revision 2: an object had passed the start window)
Syntax WaitWObj [ WObj ’:=’]< persistent (PERS) of wobjdata> ‘;’ [ ’\’ RelDist ’:=’ < expression (IN) of num > ]
Conveyor Tracking
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RAPID Instructions
DropWObj
Conveyor Tracking
Drop Work Object on Conveyor
DropWObj (Drop Work Object) is used to disconnect from the current object and the program is ready for the next.
Example MoveL *, v1000, z10, tool, \WObj:=wobj_on_cnv1; MoveL *, v1000, fine, tool, \WObj:=wobj0; DropWObj wobj_on_cnv1; MoveL *, v1000, z10, tool, \WObj:=wobj0;
Arguments DropWObj WObj
WObj (Work Object)
Data type: wobjdata
The moving work object (coordinate system) to which the robot position in the instruction is related. The mechanical unit conveyor is to be specified by the ufmec in the work object.
Program execution Dropping the work object means that the encoder unit not longer tracks the object. The object is removed from the object queue and cannot be recovered.
Limitations If the instruction is issued while the robot is actively using the conveyor coordinated work object then the motion stops. The instruction may be issued only after a fixed work object has been used in the preceding motion instructions with either a fine point or several (>1) corner zones.
Syntax DropWObj [ WObj ’:=’] < persistent (PERS) of wobjdata> ‘;’
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Conveyor Tracking
Conveyor Tracking
Additional Features
6 Additional Features for the DSQC 354 Revision 2 The S4C software supports the additional feature that is available in the DSQC 354 Revision 2: Notification of Passed Start Window: In certain applications it is important to know whether an object has gone through the start window without being connected. The DSQC 354 Revision 2 Encoder interface unit supports an additional feature which allows the S4C software to detect when an object has passed the start window without being connected and is thus lost. The detection of the lost object is done on the next WaitWObj instruction. The next WaitWObj instruction, following after an object has moved outside the start window, will return with the error ERR_CNV_DROPPED. This error can be handled in the RAPID Error handler. The DSQC 354 Revision 2 unit returns a new I/O signal, c1PassStw, on physical signal 12 from the Encoder interface unit. This signal will go high when the next connect is attempted and one or more objects have left the start window without being connected. It may be desirable to disable the automatic use of the c1PassStw signal and use this signal directly in the user’s RAPID application. Disabling the Passed Start Window Feature in WaitWObj: This feature of the DSQC 354 Revision 2 unit may not be desirable in all applications as it may limit backwards compatibility or may complicate the application. The feature can be disabled via removing a Conveyor I/O signal: Under System Parameters, Process, Types: Conveyor Systems. Remove the signal name used for PassStartW signal. This will stop the ERR_CNV_DROPPED from occurring on the next WaitWObj instruction. The c1PassStw signal from the DSQC 354 will still go high but the conveyor tracking function will no longer be looking for the signal.
7 Hardware Configuration and Connections The conveyor interface to the S4C controller is via the DSQC 354 Encoder Interface unit. Two versions of the DSQC 354 exist, namely the original unit and a Revision 2 unit. The Revision 2 unit is clearly marked and is electrically compatible with the original.
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Hardware Configuration and Connections
Conveyor Tracking
7.1 Encoder Type Selection The encoder provides a series of pulses indicating the motion of the conveyor. This is used to synchronize the motions of the robot to the motion of the conveyor. The encoder has two pulse channels, A and B which differ in phase by 90°. Each channel will send a fixed number of pulses per revolution depending upon the construction of the encoder. The number of pulses per revolution for the encoder must be selected in relation to the gearing between the conveyor and the encoder. The pulse ratio from the encoder should be in the range of 1250 - 2000 pulses per meter of conveyor motion. The pulses from channels A and B are used in quadrature to multiply the pulse ratio by 4 to get counts. This means that the control software will measure 5000 - 10000 counts per meter for an encoder with the pulse ratio given above. Reducing the number of measured counts below 5000 will reduce the accuracy of the robot tracking. Increasing the number of measured counts beyond 10000 will have no significant effect as inaccuracies in robot and cell calibration will be the dominating factors for accuracy. The encoder must be of 2 phase type for quadrature pulses, to enable registration of reverse conveyor motion, and to avoid false counts due to vibration etc. when the conveyor is not moving. Output signal: Voltage: Current Phase: Duty cycle:
Open collector PNP output 10 - 30 V (normally supplied by 24 VDC from DSQC 354) 50 - 100 mA 2 phase with 90 degree phase shift 50%
An example encoder is the Lenord & Bauer GEL 262. Minimum and Maximum Counts per Second Minimum Speed There is a lower limit on the number of counts per second before the encoder unit signals zero speed. This limit is 40 counts per second. If the speed of the conveyor is lower than this value, zero speed will be indicated. At 10,000 counts per meter, the minimum conveyor speed is 4 mm/s. Maximum Speed There is a upper limit on the number of counts per second before the encoder unit can no longer keep track of the counts along the conveyor. This limit is 20,000 counts per second. At 10,000 counts per meter, the maximum conveyor speed is 2,000 mm/s.
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Conveyor Tracking
Conveyor Tracking
Hardware Configuration and Connections
7.2 Encoder Location The encoder is normally installed on the conveyor drive unit. The encoder may be connected to an output shaft on the drive unit, directly or via a gear belt arrangement. If the encoder is connected directly to a drive unit shaft, it is important to install a specially designed flexible coupling to prevent applying mechanical forces to the encoder rotor. A coupling using a plastic/rubber hose should be avoided. If the drive unit includes a clutch arrangement, the encoder must be connected on the conveyor side of the clutch. If the conveyor drive unit is located a long distance away from the robot then the conveyor itself may be a source of inaccuracy as the conveyor will stretch or flex over the distance from the drive unit to the robot cell. In such a case it may be better to mount the encoder closer to the robot cell with a different coupling arrangement.
7.3 Encoder Connection to DSQC 354 One encoder may be connected to one or more Encoder Interface Units. The Encoder Interface Units may be connected to the same S4C cabinet as in the case for 2 conveyors, or to different S4C cabinets when two different robots shall follow the same conveyor. If the encoder is connected to Encoder Interface Units that are connected to different S4C cabinets, a diode should be installed on each of the 24 V DC connections to the encoder to prevent parallel wiring of the power supplies. The encoder should be connected to the robot by a screened cable to reduce noise. If this cable is long, the inductance in the cable will produce spike pulses on the encoder signal which may, over a period of time, damage the opto couplers in the Encoder Interface Unit. The spike pulses can be removed by installing a capacitor between the signal wire and ground for each of the 2 phases. The capacitors should be connected on the terminal board where the encoder is connected and not on the DSQC 354. Typical capacitor values are 100 nF - 1 µ F, depending on the length of the cable. The longer the cable, the larger the capacitor. The correct capacitance value can be determined by viewing the encoder signal on an oscilloscope. See the Product Manual, Installation and Commissioning, for details on connecting the encoder to the Encoder Interface Unit.
7.4 Synchronization Switch The synchronization switch indicates the presence of objects on the conveyor. This switch should be chosen so that it provides a reliable and repeatable signal for objects on the conveyor regardless of conveyor speed. If the conveyor can run backwards, then the switch should be constructed not to give a signal if an object runs backwards past the switch. If the synchronization switch can give multiple signals when an object passes then the parameter SyncSeparation can be set to so that only one signal is accepted as an object before a given distance is covered on the conveyor. See Section 9.5 Conveyor Start Window and Sync Separation. Conveyor Tracking
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Hardware Configuration and Connections
Conveyor Tracking
7.5 Connecting the DSQC 354 to the S4C Cabinet See the documentation on the CAN bus distributed I/O and DSQC 354 for information on physically connecting to the CAN bus in the S4C.
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Conveyor Tracking
Software Installation
8 Software Installation The conveyor tracking feature and the RAPID instructions WaitWObj, DropWObj, are specified in the key disk for the S4C disk pack. Normally the Conveyor software is preloaded at the factory and does not need to be re-installed unless access to the Motion System parameters is necessary. The following instructions are intended for use when the Conveyor option is to be added to an existing system. The conveyor option will install three additional configurations: I/O for the DSQC 354, Conveyor process description, and a Motion mechanical unit description. Choose ‘Query’ during boot and select ‘Service’ for motion parameters in order to gain full access to the Motion system parameters that must be modified for conveyor tracking installation. The DSQC 354 should be connected to the CAN bus before installing the conveyor tracking software. The conveyor tracking software will automatically install an External I/O configuration for the encoder unit on address 15 on the CAN bus. If the encoder unit is not at this address, I/O errors will occur at startup. The recommended installation sequence can be described as follows: 1.
Connect the DSQC 354 to the CAN bus. Note the CAN address on the unit.
2.
Install the Conveyor Tracking software. If the DSQC 354 is not on address 15 then I/O errors can be expected.
3.
If necessary, correct the address for the encoder unit specified in the System Parameters: I/O System.
4.
Reload the manipulator calibration parameters. Use Add or Replace Parameters from the File menu under System Parameters window. Load the original calibration parameters from the Manipulator Parameters disk. Note: if you must reload the old MOC saved parameters then see Reloading MOC Saved Parameters below.
5.
Restart the system. There should be no errors and the CNV1 mechanical unit should be available under the Jog Window of the Teach Pendant.
Reloading MOC Saved Parameters During installation, the conveyor option will load a specific conveyor external axis configuration file into the motion system parameters. If during Step 4 above, you loaded saved motion system parameters that were defined before the installation of conveyor software then the CNV1 mechanical unit will not appear on the Teach Pendant in Step 5.
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Conveyor Setup and Calibration
Conveyor Tracking
In order to recover the CNV1 mechanical unit the motion configuration file must be loaded manually off of disk 8 of the System Pack. 1.
Insert disk 8 into the floppy drive
2.
Under the System Parameters window, File: Add new parameters, load the file cnv1_moc from the OPTCNV directory.
3.
Restart the system.
The CNV1 mechanical unit should now be available under the Jog Window of the Teach Pendant.
8.1 Installation of 2 Conveyors The conveyor option from the key disk automatically installs one conveyor into the S4C system parameters. If two conveyors are to be used with the same S4C cabinet then the system parameters for the 2nd conveyor must be loaded manually. The 2nd conveyor I/O configuration for the 2nd DSQC 354 will use address 16 by default. 1.
Connect the 2nd DSQC 354 to the CAN bus. Note the address on the CAN bus.
2.
Insert disk 8 into the floppy drive
3.
Under the System Parameters window, File: Add new parameters, load the files: cnv2_eio, cnv2_prc, and cnv2_moc from the OPTCNV directory.
4.
Restart the system.
5.
If necessary, correct the address for the Encoder2 unit specified in the System Parameters: I/O System.
The CNV1 and CNV2 mechanical units should now be available under the Jog Window of the Teach Pendant.
9 Conveyor Setup and Calibration This section describes how the conveyor and encoder are to be calibrated with respect to the robot and the robot world frame.
9.1 Direction of Positive Motion from Encoder The encoder direction of positive motion may be checked after the correct installation of the conveyor tracking software. Run an object past the synchronization switch while viewing the conveyor position from either the Jog Window or the I/O Window. If the value is negative, reverse the A and B inputs from the encoder to the Encoder Interface Unit.
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Conveyor Tracking
Conveyor Setup and Calibration
9.2 Calibration of Counts per Meter If the exact gear ratio between the encoder and the conveyor is unknown (typically the case) then the user must make a manual calibration of the counts per meter using either a tape-measure or the robot TCP as a measuring device. If the robot TCP is to be used as the measuring device then an accurately defined tool should be used. First configure the Encoder Interface Unit for 10000 counts per meter (default) and a Queue Tracking Distance of 0.0 m. The encoder unit I/O parameters are accessible via the System Parameters windows under the I/O Signals topic. • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select CountsPerMeter and change its value to 10000 • Press OK to confirm. • Select QueueTrckDist and change its value to 0.0 • Press OK to confirm. Parameter Description CountsPerMeter
Gives the number of counts per meter of motion of the conveyor. Should be in the range of 5000-10000 for linear conveyors.
QueueTrckDist
Queue Tracking Distance, this distance defines the placement of the synchronization switch relative to the 0.0 meter point on the conveyor. The encoder unit tracks all the objects in this distance but does not allow connection until object has passed 0.0 meters.
Move an object past the sync switch and stop the conveyor. Read the conveyor position from the Jog Window, position_1. Move the conveyor at least 1 meter and read the Jog Window, position_2. The accuracy will be best if this distance is large as possible within the workspace. Use a tape-measure (or differences in robot tool position) to find the exact number of meters from position_1 to position_2, call this value measured_meters. The counts per meter are calculated: ( position_2 - position_1 ) × 10000 counts per meter = --------------------------------------------------------------------------------measured_meters
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29
Conveyor Setup and Calibration
Conveyor Tracking
Enter the correctly calculated counts per meter into the I/O configuration for the Encoder Interface Unit CountsPerMeter.
9.3 Defining the Queue Tracking Distance Before proceeding with conveyor setup and calibration it is necessary to define the desired Queue Tracking Distance. As presented earlier, the Queue Tracking Distance establishes the distance between the synchronization switch and the 0.0 m point on the conveyor. The encoder unit will keep track of all objects that have passed the synchronization switch but have not yet passed the 0.0 m point. It is not possible to connect to these objects. Under the System Parameters window: • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select QueueTrckDist and change its value. • Press OK to confirm. Parameter Description QueueTrckDistQueue Tracking Distance (meters), this distance defines the placement of the synchronization switch relative to the 0.0 meter point on the conveyor. The encoder unit tracks all the objects in this distance but does not allow connection until the object has passed 0.0 meters.
9.4 Conveyor Base Frame Calibration The accuracy of the conveyor tracking is highly dependent upon the accuracy in calibrating the conveyor base frame. For linear conveyors a method is provided which uses the robot TCP in order to measure the position and orientation of the conveyor in the workspace. Before calibrating the base frame of the conveyor the values for the CountsPerMeter and QueueTrkDist must have been entered into the S4C controller and verified to be correct. The conveyor base frame calibration method will use the measurement of 3 positions of the same object on the conveyor to determine the conveyor base frame, as shown in Figure 4.
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Conveyor Tracking
Conveyor Tracking
Conveyor Setup and Calibration
Synchronization Switch
Base Frame z y
Conveyor Direction
QueueTrckDist
x
p_1
p_2
p_3
0.0 m
Conveyor distance Figure 4 Definition points for a Linear Conveyor
Prior to defining the 3 positions, an object must be defined on the conveyor: 1.
Step FWD through a RAPID program containing the two commands: ActUnit CNV1; WaitWObj wobjcnv1; Define the conveyor coordinated work object as described in Section 4.3 Defining a Conveyor Coordinated Work Object.
2.
Run the conveyor until an object passes through the sync switch and beyond the 0.0 m point. The WaitWObj instruction will end execution. Stop the conveyor.
Once a object is on the conveyor and beyond the 0.0 m point, it is possible to use the base frame calibration method to define the conveyor position and orientation in the workspace: • Press the Miscellaneous key
and select the Service window.
• Choose View:BaseFrame. A dialog containing all synchronized mechanical units is shown. • Select the conveyor mechanical unit and press Enter
or Def.
A dialog like the one in Figure 5 will appear.
Conveyor Tracking
31
Conveyor Setup and Calibration
Conveyor Tracking
Lin Single User Frame Definition : CNV1 Unit : n points (n=3)... Status
Method Point
1(3)
Point 1 Point 2 Point 3
Modified ModPos
Cancel
(OK)
Figure 5 Dialog for definition of user frame for a rotational axis.
To choose a definition method Before you start modifying any positions, make sure the desired method is displayed. • Select the field Method and press Enter
.
• Choose number of points to use for definition and press OK. (Currently only the three point method is implemented.)
To record reference points • Select the first point Point 1. This point will be the origin for the user frame in the conveyor coordinated work object. • Point out Point 1 on the object on the conveyor with the robot’s TCP. • Modify the position by pressing the function key ModPos. • Move the conveyor in the positive direction and repeat the above for the points Point 2 and Point 3.
To calculate the base frame • Press OK to calculate the base frame for the selected conveyor mechanical unit. When the calculation is finished a dialog like the one in Figure 6 will appear.
32
Conveyor Tracking
Conveyor Tracking
Conveyor Setup and Calibration
Lin Single User Frame Calc Result Unit : CNV1 Calculation Log Method Mean error Max error Cartesian X
1(10) n points (n=3) 1.12 2.31 7.08
File...
Cancel
OK
Figure 6 The result of a base frame calculation for a linear conveyor.
The calculation log shows the conveyor base frame expressed in the world coordinate system. Field
Description
Unit
The name of the mechanical unit for which the definition of base frame has be done.
List contents
Description
Method
Displays the selected calibration method.
Mean error
The accuracy of the robot positioning against the reference point.
Max error
The maximum error for one positioning.
Cartesian X
The x coordinate for the base frame.
Cartesian Y
The y coordinate for the base frame.
Cartesian Z
The z coordinate for the base frame.
Quaternion 1-4
Orientation components for the base frame.
The calculation result can be saved in a separate file for later use in a PC: - Press the function key File. - Specify a name and a location where to save the result. - Choose OK to confirm the save. If the estimated error is - acceptable, press OK to confirm the new user frame. - not acceptable, redefine by pressing Cancel. • Choose File: Restart in the Service window to activate the user frame.
Conveyor Tracking
33
Conveyor Setup and Calibration
Conveyor Tracking
Verify the Results of the Calibration After restarting the controller, verify the conveyor base frame calibration as follows: 1.
Step FWD through a RAPID program containing the two commands: ActUnit CNV1; WaitWObj wobjcnv1;
2.
Run the conveyor until another object passes through the sync switch and beyond the 0.0 m point. The WaitWObj instruction will end execution. Stop the conveyor.
3.
Move the robot Tool Centre Point back to the previously chosen Point 1 on the work object.
4.
From the Jogging Window, read the X, Y, Z position of the Tool Centre Point. Use the accurate tool and use wobjcnv1.
5.
The robot’s TCP x, y, and z position in the work object coordinates should be 0.0 mm (or very close to that).
6.
Select WObj: wobjcnv1 together with Coord: WObj in the Jogging Window and jog the robot in the conveyor’s x, y, and z directions. Verify that the x-direction is in the direction of positive motion of the conveyor.
9.5 Conveyor Start Window and Sync Separation The Start Window is the length along the conveyor in which objects are tracked by the encoder unit and are ready for connection. When a WaitWObj instruction is issued the system will connect to the first object inside the start window or wait otherwise. If an object goes beyond the start window then it is no longer tracked and it is not available for connection. Such objects are automatically skipped. The purpose of the start window is to provide a buffer of objects for speed variations of the conveyor. If an object is connected within the start window then it should be certain that the motion coordinated to the object can be completed before the working area limit or maximum distance is reached. The Sync Separation parameter is used to filter out unwanted sync signals from a synchronization switch. This parameter establishes a minimum distance that the conveyor must move after one sync signal before a new sync signal is accepted as a valid object. Under the System Parameters window: • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select the parameters and change values. • Press OK to confirm.
34
Conveyor Tracking
Conveyor Tracking
Conveyor Setup and Calibration
Parameter
Description
StartWinWidth
Start Window Width (meters), this distance defines the size of the start window. All objects within this window are tracked and are eligible for use in a coordinated work object. A WaitWObj instruction will connect to the first object in the window.
SyncSeparation
Sync Signal Separation (meters), this distance defines the minimum distance that the conveyor must move after a sync signal before a new sync signal is accepted as a valid object.
9.6 Conveyor Maximum and Minimum Distances It is possible to monitor the position of the conveyor and automatically drop any connected objects which move outside the maximum or minimum specified distance. The purpose is to prevent coordination of motion beyond the work area of the robot for both forward and backward operation of the conveyor. Under the System Parameters window, • Choose Topics: Process. • Choose Types: Conveyor Systems. • Select CONVEYOR1 and press Enter
.
• Select the parameters Maximum distance and Minimum distance and change the values. • Press OK to confirm. Parameter
Description
Maximum distance The maximum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is produced. Minimum distance The minimum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is produced.
9.7 Robot Adjustment Speed When entering conveyor tracking, the robot must adjust its speed up to the speed of the conveyor. The rate at which the robot ‘catches up’ to the conveyor for the first motion is controlled by the Adjustment Speed parameter. If the conveyor has a speed above 200 mm/s then this parameter may have to be increased in order for the robot to quickly move to the first point on the conveyor.
Conveyor Tracking
35
Conveyor Setup and Calibration
Conveyor Tracking
Under the System Parameters window, • Choose Topics: Process. • Choose Types: Conveyor Systems. • Select CONVEYOR1 and press Enter
.
• Select the parameter Adjustment Speed and change the values. • Press OK to confirm. Parameter
Description
Adjustment Speed The speed (in mm/s) at which the robot should catch up to the conveyor for the first point coordinated to the conveyor position. It must be higher than the conveyor speed or the robot may never catch up to the conveyor.
9.8 Motion System Parameters There are two parameters that should be adjusted under the motion system. These parameters regulate the cpu load and the accuracy of the conveyor tracking under extreme conditions. The first parameter is Path resolution. This parameter specifies the period of the path planner in planning steps along the path (no units). Step calculations require lots of cpu time and if steps cannot be calculated in time to keep the robot on the path then error 50082 Deceleration Limit may occur. As conveyor tracking increases the general cpu load then the Path resolution parameter must be increased in order to prevent this error. The second parameter is Process update time. This parameter specifies the period (in seconds) at which the conveyor process should update the robot kinematics for path planning purposes. This parameter will affect conveyor accuracy only when the robot must make large reductions of programmed TCP speed due to dynamic considerations (singularities, large reorientations, and slow external axes). If the Process update time is set too large then errors in tracking will be small in the beginning of tracking but get larger after reductions of TCP speed. Decreasing Process update time will increase the cpu load and an increase of the Path resolution will be necessary.
36
Conveyor Tracking
Conveyor Tracking
Conveyor Setup and Calibration
Under the System Parameters window, • Choose Topics: Manipulator. • Choose Types: Motion system. • Select system_1 and press Enter
.
• Select the parameters Path resolution, and Process update time and change the values. • Press OK to confirm. Parameter
Description
Path resolution The period at which steps along the path are calculated. Increase by 20% for conveyor tracking. Process update time The time (in seconds) at which the conveyor process updates the robot kinematics on the conveyor position. Set to 0.09677
9.9 Motion Mechanical Unit Parameters The mechanical unit parameters define the name used by the conveyor for RAPID and the Teach Pendant as well as the conditions for activation and deactivation. These parameters may be changed to give a customer defined name to the conveyor and to ensure activation of the conveyor. Under the System Parameters window, • Choose Topics: Manipulator. • Choose Types: Mechanical Unit • Select CNV1 and press Enter
.
• Select the parameters and change the values: Parameter
Description
Name The name of the unit (max. 7 characters). This name will subsequently be used in the Jogging window and from the program, e.g. when an unit is to be activated. Activate at start up
The conveyor is to be activated automatically at start up.
Do not allow deact.
The conveyor cannot be deactivated.
9.10 Configuration for Track Motion following Conveyor If the robot is mounted on a track, and the track is parallel to the conveyor, then the motion can be configured such that the track follows the conveyor. The IRB robot manipulator and track must be configured for Coordinated Track Motion. See the User’s Guide for information on configuring the robot and track for coordinated motion.
Conveyor Tracking
37
Conveyor Setup and Calibration
Conveyor Tracking
Once the robot and track are configured for coordinated motion, then conveyor tracking will automatically use the track to follow the conveyor. The track will maintain the same position relative to the object as the object moves on the conveyor as it was during programming. The track and robot base frame must be defined such that positive motion of the track is in the same direction as the conveyor. In some installations this may require a redefinition of the track’s direction of positive motion and calibration position. See Figure 7 below. Yconveyor
Conveyor Direction
X conveyor
YWorld, Track
X
X robot Yrobot
World, Track
- + Direction of Track 0.0 m Conveyor Quaternion: 1, 0, 0, 0 Robot Base Quaternion: 0.7071, 0, 0, 0.7071 Track Base Quaternion: 1, 0, 0, 0 Figure 7 Example Configuration of Track and Conveyor Directions
Performance Considerations: Avoid moving the track when making the conveyor coordinated portion of the RAPID program. All motions of the track relative to the conveyor are saved and played back during conveyor tracking. Tracks typically have an acceleration ability that is far below that of the robot joints. If the track must move relative to the object then this will require an acceleration that will cause a reduction of the robot’s TCP speed along the path in order to maintain coordination.
38
Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
10 Circular Conveyor Tracking The conveyor tracking software provides the capability of tracking circular conveyors. The fundamental principle for configuration of circular conveyor tracking is to replace all references to ‘meters’ by ‘radians’ and proceed with the configuration as given in the Section 9 Conveyor Setup and Calibration. This section will review the steps in setup and configuration and note those places where the configuration must be changed to accommodate a circular conveyor. The following figure shows an example of circular conveyor tracking with example units and distances:
CountsPerMeter = 40000 counts per radian At 6 m radius, one count = 0.15 mm Direction of Rotation
Minimum Distance = -100 milliradians At 6 m radius, = -600 mm
2.44 rad
radius = 6 meter Y
X
Synch Switch SyncSeparation = 0.005 rad At 6 m radius, = 30 mm QueueTrkDist = 0.017 rad At 6 m radius, = 100 mm
0.0 rad
Xworld
Conveyor Base Frame: Base frame x = 8.0 m Base frame y = 0.0 m Base frame z = 0.0 m The X axis is rotated 2.44 rad from the World X, Base frame q1 = 0.3420 Base frame q2 = 0.0000 Base frame q3 = 0.0000 Base frame q4 = 0.9397
Maximum Distance = 420 milliradians At 6 m radius, = 2520 mm
StartWinWidth = 0.017 rad At 6 m radius, = 100 mm
Yworld Figure 8 Example Configuration of Circular Conveyor Tracking
10.1 Encoder Type Selection and Location The goal in selecting an encoder for circular conveyor tracking is to have 0.1 mm to 0.2 mm resolution per count at the maximum radius of conveyor tracking. Example: Following Figure 8 , at a 6 meter radius in order to have 0.15 mm per count, we must have 40,000 counts per radian at the centre of the table. The counts are quadrature encoded (four counts per pulse), thus the encoder must give 10,000 pulses per radian of circular conveyor movement. For a full revolution there are 2π radians per revolution, giving a requirement for 10000 × 2π = 62831,85 pulses per revolution of the circular conveyor.
Conveyor Tracking
39
Circular Conveyor Tracking
Conveyor Tracking
Gear Ratio Selection: If an encoder with 1000 pulses per revolution is selected, then we require a gear ratio of 1 to 62.83185 between the circular conveyor and the encoder shaft. Note: The maximum value for configuration of CountsPerMeter in the encoder software is 50000. This limitation should be taken into consideration when selecting gearing and encoder.
10.2 Software Installation The DSQC 354 Encoder Interface Unit and conveyor tracking software are connected and installed in the same manner as for linear conveyors.
10.3 Direction of Positive Motion from Encoder See the description for linear conveyors, Section 9.1.
10.4 Calibration of Counts per Meter For a circular conveyor, the setting of the CountsPerMeter parameter should be known from the selection of the encoder and the gear ratio between the circular conveyor and the encoder shaft. If the value is not known, then it is possible to measure the value following the same steps as outlined for a linear conveyor with extra equipment for measuring the change in angle of the conveyor between position_1, and position_2.
10.5 Defining the Queue Tracking Distance Before proceeding with conveyor setup and calibration it is necessary to define the desired Queue Tracking Distance. The Queue Tracking Distance establishes the distance between the synchronization switch and the 0.0 rad point on the circular conveyor. The encoder unit will keep track of all objects that have passed the synchronization switch but have not yet passed the 0.0 rad point. Under the System Parameters window: • Choose Topics: I/O Signals • Choose Types: Units • Select Encoder and press Enter
.
• Select QueueTrckDist and change its value. • Press OK to confirm.
40
Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
Parameter
Description
QueueTrckDist
Queue Tracking Distance (radians for circular conveyor). This distance defines the placement of the synchronization switch relative to the 0.0 rad point on the conveyor. The encoder unit tracks all objects in this distance but does not allow connection until an object has passed 0.0 rad.
10.6 Circular Conveyor Base Frame Calibration - Manual Method The accuracy of the circular conveyor tracking is highly dependent upon the accuracy in specifying the conveyor base frame. In this software release, there are two choices available for base frame calibration of a circular conveyor: 1) Enter the orientation and position of the base frame based on drawings of the robot installation and simple TCP measurements. 2) Use the robot TCP as a measuring tool and measure several points along the conveyor with some trigonometric calculations to calculate the conveyor base frame position and quaternion. In this section, the first choice using a manually calculated quaternion is described. However, the second choice is the recommended approach and is discussed in Section 10.7 Circular Conveyor Base Frame Calibration - TCP Measurement Method. Orientation - Manual Method Definition of the quaternion for conveyor orientation will also define the location of the 0.0 rad point on the circular conveyor. The direction of the X axis will define the 0.0 rad point while the direction of the Z axis will define the direction of positive rotation using the right-hand-rule. The following figure shows two installations, one with clockwise rotation and the other with counterclockwise rotation and the corresponding quaternions. In cases where the 0.0 rad point is not an even multiple of 90 ° from the World frame, calculation of the conveyor orientation quaternion must be done using manual calculations of the quaternion. The TCP can be used to help make measurements, see Section 10.7.
Conveyor Tracking
41
Circular Conveyor Tracking
Direction of Rotation
Conveyor Tracking
QueueTrckDist Direction of Rotation
0.0 rad
X
X
0.0 rad
Y
Y
Xworld
Xworld Yworld
Yworld Quaternion: 0.7071, 0, 0, 0.7071
Quaternion: 0, 0.7071, -0.7071, 0
Figure 9 Circular Conveyor Orientation Quaternions
Base Frame Position and Start Window Start Calibration - Manual Method The conveyor base frame x, y, and z position must be specified relative to the world frame. This position must be calculated from the installation drawings or by using the robot as a measuring tool. Using the robot, one point may be marked on the edge of the circular conveyor and the TCP position is recorded for several points and the centre point of the circle can be found. This is described in detail in the following section.
10.7 Circular Conveyor Base Frame Calibration - TCP Measurement Method It is possible to use TCP measurements and RAPID programs to assist in the calculation of the conveyor base frame position and quaternion. This section outlines the necessary steps for a circular conveyor. Base Frame X, Y, Z Position The following method uses 3 measured points on the circular conveyor to calculate the centre of rotation. The 3 points should be spaced as far apart as possible around the periphery.
42
1.
Use Wobj0 on the Teach Pendant. Pick out a reference point on the circular conveyor, jog the TCP to this point and record p_0.
2.
Run the conveyor to another position. Jog the TCP back to the reference point and record p_1.
3.
Run the conveyor to a third position, jog the TCP back to the reference point and record p_2.
Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
4.
Use the utility function, UTL_cirCntr, with the points p_0, p1, and p_2, to calculate the centre of the circle, p_centre.
5.
Take the X and Y values from p_centre and enter them into the Base Frame values for the Conveyor, converting to meters, see Section 11.3. These are shown in Figure 9. The Z value will be entered later, once the work object zero position has been chosen.
Base Frame Orientation and Start Window Start Calibration The purpose of this section is to define the base frame quaternion and the Z value of the base frame. The base frame quaternion will define where the 0.0 rad point is for the robot motion. The following figure shows an example of the angles that are to be used in defining the base frame orientation for the circular conveyor:
Counter-Clockwise Rotation p_centre X, Y
Base θ Pθ
Synch Switch
p_0 X_0, Y_0
Xworld
TPθ
Qθ 0.0 rad
Qθ = TP θ = Pθ = Base θ =
Queue Tracking Distance angle Angle shown on Teach Pendant Angle calculated from p_0 position. Base frame angle to be converted into a quaternion.
Yworld Figure 10 Example Measurement Points for Base Frame Calculation on a Circular Conveyor
The following procedure can be used to calculate the quaternion for the base frame orientation. 1.
Define a temporary conveyor base frame quaternion as 1, 0, 0, 0
2.
Define a conveyor coordinated work object wobjcnv1
Conveyor Tracking
43
Circular Conveyor Tracking 3.
Conveyor Tracking
Step FWD through a RAPID program containing the two commands: ActUnit CNV1; WaitWObj wobjcnv1;
4.
Run the conveyor until an object passes through the sync switch and beyond the Queue Tracking Distance. The WaitWObj instruction will end execution. Stop the conveyor.
5.
Using wobjcnv1, move the robot Tool Centre Point to the desired zero position on the work object, record this point, p_0. Write down the X_0, Y_0, and Z_0 coordinates of the point p_0 as shown on the Teach Pendant when using the wobjcnv1 work object.
6.
Write down the angle shown in the Jogging Window for the CNV1 conveyor. This is angle TP θ , see Figure 10
7.
Calculate P θ from the X_0 and Y_0 coordinates of p_0 and the atan function. X_0 and Y_0 should both be positive when using the atan function. Check the value, it may be necessary to add 90 degrees: Y_0 P θ = atan ------------- X_0
8.
Calculate the value of
Base θ : Base θ = P θ – TP θ
9.
Calculate the quaternion for the Base frame taking into account the direction of rotation: Counter clockwise rotation: q1 = cos ( Baseθ ⁄ 2 ) q2 = 0.0 q3 = 0.0 q4 = sin ( Base θ ⁄ 2 ) Clockwise rotation: q1 = 0.0 q2 = cos ( Baseθ ⁄ 2 ) q3 = – sin ( Baseθ ⁄ 2 ) q4 = 0.0
10. Enter the value for Z (in meters) from p_0, and the values for the quaternions, q1,
q2, q3, and q4, into the base frame for the Conveyor, see System Parameters, Section 11.3 Topic: Manipulator.
10.8 Conveyor Start Window and Sync Separation For circular conveyor tracking these distances are to be specified in radians.
44
Conveyor Tracking
Conveyor Tracking
Circular Conveyor Tracking
10.9 Conveyor Maximum and Minimum Distances For circular conveyor tracking these distances are to be specified in milliradians.
10.10 Conveyor Adjustment Speed The same as for linear conveyors.
10.11 Motion System Parameters The same as for linear conveyors.
10.12 Motion Mechanical Unit Parameters The same as for linear conveyors.
10.13 Motion Transmission and Single Type The motion configuration of the conveyor must be adjusted to account for a circular motion of the conveyor. There are two parameters that must be adjusted. Under the System Parameters window, • Choose Topics: Manipulator. • Choose Types: Transmission. • Select CNV1 and press Enter
.
• Select the parameter Rotating move and change the value. Parameter Description Rotating move
Specifies if the conveyor is rotating (Yes) or linear (No).
• Press OK to confirm. • Choose Types: Single type. • Select CNV1 and press Enter
.
• Select the parameter Mechanics and change the value. Parameter Mechanics
Conveyor Tracking
Description Specifies the mechanical structure of the conveyor. Choose EXT_ROT
45
Conveyor Tracking System Parameters
Conveyor Tracking
11 Conveyor Tracking System Parameters This section presents a summary of all system parameters that affect conveyor tracking. They are organised by topic as found under the System Parameters window on the Teach Pendant.
11.1 Topic: I/O Signals Topic • Choose Types: Units • Select Encoder and press Enter
46
.
Parameter
Description
CountsPerMeter
Gives the number of quadrature pulses per meter of motion of the conveyor. Should be in the range of 500010000 for linear conveyors.
SyncSeparation
Sync Signal Separation (meters), this distance defines the minimum distance that the conveyor must move after a sync signal before a new sync signal is accepted as a valid object.
QueueTrckDist
Queue Tracking Distance (meters), this distance defines the placement of the synchronization switch relative to the 0.0 meter point on the conveyor. The encoder unit tracks all objects in this distance but does not allow connection until an object has passed 0.0 meters.
StartWinWidth
Start Window Width (meters), this distance defines the size of the start window. All objects within this window are tracked and are eligible for use in a coordinated work object. A WaitWObj instruction will connect to the first object in the window.
IIRFPeriod
Internal Use: Specifies the period of the speed filter on the encoder unit, must be the same as the PollRate.
IIRFNoOfPoles
Internal Use: Specifies the number of poles in the Infinite Impulse Response (IIR) speed filter.
IIRFNoOfZeros
Internal Use: Specifies the number of zeros in the speed filter.
IIRFXfrmMetPol
Internal Use: Specifies the transform method for discreting the speed filter coefficients for the filter poles.
IIRFXfrmMetZero
Internal Use: Specifies the transform method for discreting the speed filter coefficients for the filter zeros.
IIRFFZ
Internal Use: Specifies the location of the real part of the zeros in the left-half plane (in Hz) when zeros have been given. Conveyor Tracking
Conveyor Tracking
Conveyor Tracking System Parameters
IIRFDZ
Internal Use: Specifies the damping of the zeros and thus the imaginary portion of the zero location in the left-half plane.
IIRFFP
Specifies the location of the real part of the poles in the left-half plane (in Hz). This is the break frequency for the speed filters in the encoder unit and regulates how hard the speed is filtered in the encoder unit.
IIRFDP
Internal Use: Specifies the damping of the poles and thus the imaginary portion of the zero location in the left-half plane.
IIRFGain
Internal Use: Specifies gain of the speed filter. Must be 1.0
FIRLengh
Internal Use: Specifies the length of the Finite Impulse Response (FIR) filter on the position.
FIRB0
Internal Use: Specifies the weight on the first coefficient in the FIR position filter.
FIRB1
Internal Use: Specifies the weight on the second coefficient in the FIR position filter.
11.2 Topic: Process • Choose Types: Conveyor Systems. • Select CONVEYOR1 and press Enter Parameter
.
Description
Adjustment Speed
The speed (in mm/s) at which the robot should catch up to the conveyor for the first point coordinated to the conveyor position. It must be higher than the conveyor speed or the robot may never catch up to the conveyor.
Minimum distance
The minimum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is produced.
Maximum distance
The maximum distance (in millimeters) that a connected object may have before being automatically dropped. If an object is dropped during coordinated motion, then the motion is stopped and an error is generated.
Conveyor Tracking
47
Conveyor Tracking System Parameters
Conveyor Tracking
• Choose Types: CAN Sensors. • Select CAN1 and press Enter Parameter
.
Description
Signal delay
Internal Use: The delay (in milliseconds) for adjusting the prediction time of the conveyor position using the conveyor speed.
Connected signal
Name of the digital input signal for connection.
Position signal
Name of the analog input signal for conveyor position.
Velocity signal
Name of the analog input signal for conveyor speed.
Null speed signal
Name of the digital input signal indicating zero speed on the conveyor.
Data ready signal
Name of the digital input signal indicating a poll of the encoder unit.
WaitWObj signal
Name of the digital output signal to indicate that a connection is desired to an object in the queue.
DropWObj signal
Name of the digital output signal to drop a connected object on the encoder unit.
PassStartW signal
Name of the digital input signal to indicate that an object has gone past the start window without being connected.
11.3 Topic: Manipulator • Choose Types: Motion system. • Select system_1and press Enter
.
Parameter Description Path resolution
The period at which steps along the path are calculated.
Process update time The time (in seconds) at which the conveyor process updates the robot kinematics on the conveyor position. • Choose Types: Mechanical Unit • Select CNV1 and press Enter Parameter
.
Description
Name The name of the unit (max. 7 characters). This name will subsequently be used in the Jogging window and from the program, e.g. when an unit is to be activated.
48
Activate at start up
The conveyor is to be activated automatically at start up.
Do not allow deact.
The conveyor cannot be deactivated.
Conveyor Tracking
Conveyor Tracking
Conveyor Tracking System Parameters
• Choose Types: Single. • Select CNV1 and press Enter Parameter
.
Description
Base frame x The X-coordinate of the conveyor’s base coordinate system’s position in relation to the world coordinate system (in metres). Base frame y metres).
The Y-coordinate of the conveyor’s base coordinate system (in
Base frame z metres).
The Z-coordinate of the conveyor’s base coordinate system (in
Base frame q1-q4 The orientation of the conveyor base coordinate system in relation to the world coordinate system (expressed in quaternions q1-q4).
• Choose Types: Single type. • Select CNV1 and press Enter
.
Parameter Description Mechanics Specifies the mechanical structure of the conveyor.
• Choose Types: Transmission. • Select CNV1 and press Enter Parameter Rotating move
Conveyor Tracking
.
Description Specifies if the conveyor is rotating (Yes) or linear (No).
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Conveyor Tracking System Parameters
50
Conveyor Tracking
Conveyor Tracking
Index
A Activating the Conveyor 14 Additional Features for the DSQC 354 Revision 2 23 B BaseFrame 31 C Calibration of Counts per Meter 29, 40 Circular Conveyor Base Frame Calibration Manual Method 41 common drive unit 20, 22 Configuration for Track Motion following Conveyor 37 Connecting the DSQC 354 to S4C Cabinet 26 Conveyor Adjustment Speed 45 Conveyor Base Frame Calibration 30 Conveyor Maximum and Minimum Distances 35, 45 Conveyor Setup and Calibration 28 Conveyor Start Window and Sync Separation 34, 44 Coordinate Systems 12 D DeactUnit 20, 22 Defining a Conveyor Coordinated Work Object 14 Defining the Queue Tracking Distance 30, 40 Direction of Positive Motion from Encoder 28, 40 Drop Work Object on Conveyor 22 Dropping a Work Object 16 DropWObj 22 E Encoder Connection to DSQC 354 25 Encoder Location 25 Encoder Type Selection 24 Encoder Type Selection and Location 39 Entering and Exiting Conveyor Tracking
Conveyor Tracking
Motion in Corner Zones 16 external axes deactivate 20, 22 F Features 6 Finepoint Programming 18 H Hardware Configuration and Connections 23 I Information on Teach Pendant 17 Installation of 2 Conveyors 28 Introduction 5 L Limitations 8 M mechanical unit deactivate 20, 22 Modes of Operation 18 Motion Mechanical Unit Parameter 37 Motion Mechanical Unit Parameters 45 Motion System Parameters 36, 45 Motion Transmission and Single Type 45 Motor parameters 35, 36, 37, 45, 47, 48, 49 O Operation under AUTO 18 Operation under Manual Full Speed Mode (100%) 19 Operation under Manual Reduced Speed Mode ( 18 Overview of Conveyor Tracking 5 P Physical Components 6 Principles of Conveyor Tracking in S4C 9 Programming Considerations 17 Programming Conveyor Tracking 13 51
Index
Programming the Conveyor Coordinated Motion 15 R Robot Adjustment Speed 35 S Software Installation 27, 40 Start Window and Queue Tracking Distance 10 Synchronization Switch 25 T TCP Measurement Method 42 Topic I/O Signals Topic 46 Manipulator 48 Process 47 W Wait for Work Object on Conveyor 20 Waiting for a Work Object 15 WaitWObj 20 Working with the Object Queue 13
52
Conveyor Tracking
Notes:
ABB Robotics AB DPT / MT S-721 68 VÄSTERÅS SWEDEN Telephone: +46 (0) 21 34 40 00 Telefax: +46 (0) 21 13 25 92
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