Major Project Report.docx

RAJIV GANDHI PROUDYOGIKI VISHWAVIDYALAYA, BHOPAL

Lakshmi Narain collage of Technology and Science, Indore

Submitted by Bhupesh kushwaha Bharat kumar Sikendar kumar Jetender kumar

Department of Mechanical engineering

TABEL OF CONTAINTS

1. INTRODUCTION. 2. PROJECT PLANNING. 3. MACHINE COMPONENT. 4. DIGRAME OF ROCKER BOGIE. 5. WORKING PROCEDURE. 6. PARTS OF ROCKER BOGIE. 8. CALCULATION. 9. COCLUSION.

INTRODUCTION In this chapter, a simple design is prepared by using design software named CATIA for the Stair climbing robot to show the overall structure in different view and different planes, and then length of the links with the exact dimensions as used in project is shown by 2D model by using AUTOCAD software. Analysis and further calculations can also be observed in this report.

BASIC OF ROCKER BOGIE MECHANISM The term “bogie” refers to the links that have a drive wheel at each end. Bogies were commonly used as load wheels in the tracks of army tanks as idlers distributing the load over the terrain. Bogies were also quite commonly used on the trailers of semi-trailer trucks. Both applications now prefer trailing arm suspensions. The rocker-bogie design has no springs or stub axles for each wheel, allowing the rover to climb over obstacles, such as rocks, that are up to twice the wheel's diameter in size while keeping all six wheels on the ground. As with any suspension system, the tilt stability is limited by the height of the centre of gravity.

The term “rocker” describes the rocking aspect of the larger links present each side of the suspension system and balance the bogie as these rockers are connected to each other and the vehicle chassis through a modified differential. In the system, “bogie” refers to the conjoining links that have a drive wheel attached at each end. Bogies were commonly used to bare loading as tracks of army tanks as idlers distributing the load over the terrain. Bogies were also quite commonly used on the trailers of semitrailer trucks as that very time the trucks will have to carry much heavier load. As accordance with the motion to maintain centre of gravity of entire vehicle, when one rocker moves up-ward, the other goes down. The chassis plays vital role to maintain the average pitch angle of both rockers by allowing both rockers to move as per the situation. The physics of these rovers is quite complex. To design and control these analytical models of how the rover interacts with its environment are essential. Models are also needed for rover action planning. Simple mobility analysis of rocker-bogie vehicles have been developed and used for design evaluation in the available published works. Below figure 1.6 shows the line diagram of rocker bogie mechanism.

Figure 1.6 Line Diagram of Rocker Bogie Mechanism

ADVANTAGES OF ROCKER BOGIE MECHANISM

1. The design incorporates independent motors for each wheel. There are no springs or axles, making the design simpler and more reliable.

2. Rocker Bogie Suspension can withstand a tilt of at least 500 in any direction without overturning, which is the biggest advantage of heavy loaded vehicle. 3. It can move in harsh environment. 4. It can work in place which are beyond human reach. 5. Rocker Bogie consisting of no spring and stub axle in each wheel which allows the chassis to climb over any obstacle such as rocks, ditches, sands etc. that are upto double the wheels diameter in size while keeping all the wheels on ground for maximum time.

OBEJECTIVE OF PROJECT Our main goal is to design, develop, a robot to serve as a mobility platform, suitable for testing planetary surface exploration technologies in harsh earth environments. The design will focus on incorporating features that are believed to be essential for most planetary exploration missions based on research of past and current rovers. Given what we have learned about

existing rovers and the types of missions they aim to accomplish, our design goals for our robothave been made into these categories: 1. Mobility and navigation 2. Size and weight restrictions While our robot won't travel space, it is our objective to make a hearty and ruggedized stage that will be reasonable for testing in brutal earth conditions, on landscape like that of our moon and Mars. Given adequate versatility in planetary conditions, the robot should likewise have the capacity to suit payloads, if conceivable. Transporting delicate logical instruments crosswise over harsh landscape is the primary objective for about all investigation wanderers, and in this manner one of our focal necessities. Also, to be helpful for different clients in both scholarly world and industry, the robot needs to effectively coordinate new equipment and programming as a major aspect of its payloads. By giving a vigorous portability stage that ought to suit an extensive variety of payloads, the robot to demonstrate valuable to anybody intrigued by testing meandered related advances or directing examination in the field of room investigation. In conclusion, the wanderer will plan to perceive the size and weight imperatives that all space bound vehicles confront. While there are numerous asset requirements that forbid us from outlining a space-prepared wanderer, the plan will endeavour to oblige space contemplations when conceivable. In planning the outline determinations identifying with portability we needed to guarantee that the meandered could cross a wide assortment of brutal Earth situations. Such landscape incorporates deserts, rock fields, rock pits, sand hills, and sloping territories in a wide range of atmospheres. In analysing these landscapes we will make outline criteria

identifying with the span of snags, slopes, and speeds that the wanderer must accomplish, keeping in mind the end goal to guarantee that it could move in a wide range of conditions. in many situations the capacity to go over bigger hindrances dependably builds portability potential. For our wanderer we set the goal of having the capacity to navigate impediments, both positive and negative to the ground plane. Following factor must be kept in mind during the design of robot 1. Traction and slip 2. Lateral stability 3. Longitudinal stability 4. Static stability factor

Longitudinal stability According to, longitudinal stability of the vehicle is given when all wheels have ground contact and the condition Ni > 0 is satisfied, where Ni is the normal force at wheel i. It should be noted that even though this condition is compulsory for the static model to work, a physical rover does not necessarily tip if a wheel loses contact to the ground. However, it is less steerable.

Design of the frame of the robot First of all the main objective is to design a frame for the robot which can withstand against various climbing condition.

Figure 3.1 Basic frame for the robot

OVERALL DESIGN Various view of the stair climbing robot are as following. The figure 4.1 shown below shows the 3D view of overall structure.

Figure 4.1 Basic design of the robot Whole design is symmetric from the centre axis which can be shown from top view in figure 4.2

Figure 4.2 Top view of robot

Figure 4.3 Side view of robot link

LINK 2D VIEW Individual links dimension and their joints angle shown below by using AUTOCAD software. 1 Bogie link dimension

Figure 4.4 Bogie link dimension 2 Rocker link dimension

Figure 4.5 Rocker link dimension

The ACP plate connecting the above two links is of length 10 cm and width is 30 mm. 3 Body link dimension Figure shows the top view of body which is attached to both left and right side links of robot. It carries power supplier, motor driver and Arduino Uno.

DESIGN AND ANALYSIS 1 Selection of material Selection of material is an important step in designing of any component, the main advantages of material selection are: • It increases the reliability of product

• It reduces the cost of product • It can also optimize the weight of product. According to our requirement we have selected PVC pipe to build the structure. PVC pipe has following advantages1 Lightweight: PVC Pipes offer a tremendous weight advantage. 2 Flexibility: PVC Pipe's resistance to fracture is an extremely important performance advantage. 3 Safe Material:PVC pipe is a non-toxic and safe material that has been used for more than half a century. It is also the world's most researched and tested plastic. 4 Design Versatility: The physical properties of PVC Pipes allow designers and specifies a high degree of freedom when designing new products and developing solutions where PVC acts as a replacement or refurbishment material.

ANALYSIS Under this section we will discuss our complete rover design and discuss how our key design decisions were made in order to meet the requirements and goals presented in the previous sections. Each one of these is related to meeting fundamental requirements.

1 Mobility Mobility relates to the rover’s capacity to traverse varying terrains, slopes, andObstacles. In beginning the process of formulating the drive architecture we reviewed current and past rovers in consideration of chassis design, suspension methods, wheel design, and power requirements. Since nearly all rover hardware is related to mobility, this section will review most of the mechanical design including the chassis, suspension, and wheel components. These rovers move slowly and climb over the obstacles by having wheels lift each piece of the suspension over the obstacle one portion at a time. In order to go over an obstacle, the front wheels are forced against the obstacle by the rear wheels. The rotation of the front wheel then lifts the front of the vehicle up and over the obstacle. The middle wheel is the pressed against the obstacle by the rear wheel and pulled against the obstacle by the front, until it is lifted up and over. Finally, the rear wheel is pulled over the obstacle by the front two wheels. During each wheel’s traversal of the obstacle, forward progress of the vehicle is slowed or completely halted

2 Design & Selection of Wheel The wheels are needed to be wider for increasing the traction to traverse upon the obstacles. And their diameter depend upon the availability and amount of speed required. Design of wheel is required at velocity up to .30 m/s.Assume required speed of robot is up to 0.30 m/s.As we can control the rpm of motor using microcontroller programming. Let rpm range of motor is 30 -60rpm. Using velocity relation velocity is calculated for assumed speed. V=πDN/60 FORN=60rpm & V=0.30 m/s we get the diameter of wheel using above equation, D= 0.095 m or 95mm Require diameter of the wheel is 95 mm. Hence for the light weight and cost effectiveness of the rover we will choose plastic wheels with rubber treads available in the market depending upon the calculations. Selection of rubber thread bonded to the wheel makes it light weight and durable, provides excellent traction, friction. These plastic wheels (as shown in Fig.4.6) offer a low cost solution that is durable enough for a combat robot yet still light enough to be practical. For robot used six wheels. Wheel Diameter: 100 mm Wheel Width: 20 mm Shaft Diameter: 6mm

Figure 4.7 Image of selected wheel

LINK DESIGN CALCULATION The objective of the project work is to achieve proper stair climbing so the dimensions of linkages should be proper. Assume the stair height and length 150 mm and 370 mm respectively. To climb stairs with higher stability, it is required that only one pair of wheel should be in rising position at a time. Hence to find dimension of bogie linkages, first pair of wheels should be placed at horizontal position means at the end of the rising as shown in Fig. And second pair should be placed just before the start of rising. There should be some distance between vertical edge of stair and second pair of wheel tostriking of wheels.

Figure 4.8 analysis diagram Now, need to obtain the distance between first and second wheel through CAD software (240 mm). Considering the right angled triangle ABC, Using Pythagoras in ΔABC (Figure 4.7) assume lengths AB and BC is x. AC² = AB² + BC² 240² = x² + x² 240² = 2x² x = 170 mm Hence, AB = BC =170 mm

Figure 4.9 Cad drawing for first triangle

Figure 4.10 Cad drawing for second triangle rising position Similarly, to find dimensions for rocker linkages first two wheel pairs should be placed at horizontal position. Third wheel pair should nearly complete its rising before starting of rising of first pair of wheel. By placing wheel in such manner we obtained dimension of link BC (170mm). Now consider ΔBDE (Fig. 4.9), BE² = BD² + DE² 312² = 2y² y = 221 mm Hence, BD = DE = 221 mm

Figure 4.11 Final dimension of all link

Rocker Bogie After Completion

CONCLUSION This is a wide field of study and is very less explored. So this gave us the motivation for the development of this rocker bogie suspension system in a cost effective manner. Our concern during the development of the rover will be to optimize the speed such that the effective with maximum possible rigidity and ruggedness. With certain development the bogie system can be used for defense related operation and also in wheelchairs for climbing stairs.