About Project

College of Sciences Bachelor of Engineering Technology 216.323 Final Year Project

Introduction

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Table of Contents 1.0

PROJECT DETAILS........................................................................................3

2.0

TECHNICAL DETAILS.....................................................................................5

2.1 2.2 2.3 2.4 3.0

GPS.................................................................................................. .........................5 PITCH/ROLL SENSOR................................................................................................. .6 WEATHER STATION.................................................................................................... .6 MISCELLANIOUS........................................................................................................ .7 SUMARY OF DELIVERABLES...........................................................................8

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1.0

PROJECT DETAILS

This project is being completed on behalf of NIWA (National Institute of Water and Atmospheric Research). Dejan Dejkic (PhD, Massey University) and Gavin Macaulay (PhD, NIWA) are the supervisors for the project. NIWA collects acoustic data from echo-sounders on fishing industry vessels. The most common echo-sounder used is PC-based. The system records acoustic data along with positional data from a GPS unit. Below is a simple diagram of how an echo sounder operates (figure 1).

Figure 1 – Echo sounder (www.whoi.edu)

NIWA would like to have the ability to integrate the echo sounder system with data they read from various other sensors on vessels. In particular, pitch/roll data, and weather readings.

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The pitch and roll data is used to correct the acoustical data for vessel motion (figure 2). The weather station sensor is an optional extra that NIWA indicated they would like to have (figure 3).

Figure 2 – Pitch/Roll sensor

Figure 3 – Weather station

The only auxiliary input on the echo-sounder software is the one used for the GPS data, hence the only way to get the echo-sounder to record additional data, such as pitch/roll, is to combine the pitch/roll measurements with the data coming from the GPS device (figure 4).

Figure 4 – GPS device

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2.0

TECHNICAL DETAILS

This section will outline some of the technical details associated with the project. The software used to manage the echo sounder is customisable, so extra signals from other devices can be added without having to change the program’s code. All messages received by the PC must be in ASCII format. 2.1

GPS

The GPS messages are typically sent to the echo-sounder in the NMEA format. This means that the design will need to adhere to an RS232/4800 baud 8/N/1 standard to receive data from the GPS unit. (this is the closest serial transmission match to the systems currently implemented). The signals are picked up in the software in the form of “

..<end>” so the transmission to the PC software will need to be in this format.

Below is a

screenshot of a typical output from the GPS device (figure 5), the output will have to look similar to this.

Figure 5 – GPS output

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2.2

PITCH/ROLL SENSOR

The pitch/roll sensor that NIWA uses is the MicroStrain 3DM-GX1. These sensors produce binary data via the RS232 port at 38400 baud. My device will need to convert these signals into an ASCII message. The device should output a status message every 10 seconds or so. This should include the pitch/roll sensor’s serial number, and 3DM-GX1 version. This message will need to be relayed to the PC. This is so the vessels that use the device can determine the make and model of the sensor quickly when troubleshooting.

2.3

WEATHER STATION

The addition of the third RS232 device (the weather station) was given to me as an optional extra task. This is simply a third input stream, but will make the device harder to design, because there will be more processing taking place in the microcontroller.

2.4

MISCELLANIOUS

The data transfer from the device should be constant, so that when analyzing the acoustic data a constant time offset can be applied to the pitch/roll measurements to yield the actual time at which they were taken. Measurements of the delay have to be measured and provided to NIWA at the end of the project. Sometimes the data coming from the GPS device (at 4800 baud) can take up most of the capacity of the link. To resolve this problem it has been requested that the device should output data to the echo-sounder at a higher baud rate (i.e. 9600 baud).

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Most of the echo-sounder installations receive data at 4800 baud, but some receive it at 9600 baud. The device should have the ability to change the baud rate (a switch). The type of vessels the device would be installed on all have 230V main power supplies. They can be noisy though, and suffer from brown-outs. The device would need to include a suitable main adapter to power itself and to recover correctly power fluctuations (i.e. a reliable power supply). Status indicators are a preference so that problems within the device can be quickly identified. The device, once installed, will run continuously for 6-8 weeks. The choice of components and the internal logic need to be produced with a high level of reliability and resilience in mind. A simple way to reset the device needs to be added.

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3.0

SUMARY OF DELIVERABLES

The project should produce a device that can: -

Multiplex 2-3 serial RS232 signals together;

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Output the signal in an identifiable format (ASCII, 8/N/1);

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Send status messages to a PC approximately every 10 seconds;

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Allow full duplex communication;

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Change port baud rates via switches;

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Operate in electronically noisy environments;

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Identify and/or recover from errors.

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