advanced dynamics report

8/2/2019 Advanced Dynamics Report

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ADVANCED DYNAMICS

ME 502

PRO/MECHANISM REPORT

FOR

DYNAMIC SIMULATION OF A FOUR- BAR MECHANISM

NAME: GANAPATHY RAAMAN BALAJI

BUID: 221532


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ABSTRACT:

The main objective of this assignment is to get familiar with the basics of dynamic simulation of

a simple Multi-Body System (MBS) using Pro/Mechanism. We use the obtained simulation

results as a tool to carry out open ended MBS designs. We have broken down the entire process

into three basic modules: creating rigid body (links) in the PRO/E-Part Mode, assembling the

created bodies using Pro/assembly mode by defining constraints between the links, and finishing

the model by defining drivers, measures, defining and running Dynamic analysis, displaying and

discussing the results.

INTRODUCTION:

(a) Introduction To The Given Mechanism:The given mechanism is a simple four-bar mechanism which is driven by a servo motor

in one of the links, and kinematic analysis is carried out to find the position of a link at a

particular time or angle of the rotating link. The below diagram (Fig. 1) shows an

example of a four-bar mechanism.

Fig 1: A simple four bar mechanism

The model that was given as assignment is a Crank-Rocker Mechanism, where the motoris fixed on a pin joint located at the longest side. Fig. 2 shows the model of the four bar

mechanism created in Pro/E. The frame, crank, coupler and the follower are connected to

one another by pin joints.


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Fig 2: Model created in Pro/E

(b)Assumptions done to create the model in Pro/E and analyze the model in Pro/Mechanism:1) Dimensional Assumptions:

Length of link 1: 15 in Length of links 2,3: 8 in Length of link 4: 9 in Width of Links 1,2,3,4: 1.0 in Thickness of Links 1,2,3,4: 0.5 in Diameter of the pin joints: 0.5 in Thickness of the pin joints: 0.5 in

2) Constraints of the links: Link 1: Default Links 2,3,4: Pins

3) Velocity Magnitude: Servo motors velocity: 72deg/s

4) Time for analysis of motion of the links Time: 10secs


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The lengths of the links are assumed to be in inches to create consistency in dimensions. The

figures for each of the link are shown in Appendix A.

RESULTS:

The analysis was done for two cases, one with the coupler, on the same plane as the frame (Fig.2) and the other in which the frame was in a lower plane wrt the coupler (Fig. 3).

Fig. 3: Four bar with the coupler and the frame in different planes

Though we expect the model in Fig 2 not to work, owing to the fact that the coupler and frame

might intersect, being on the same plane, we do not see any changes while analyzing the results

of both the models. This is due to the fact that we do not specify solids; Pro/E just analyzes the

model and gives us the result assuming that it does not intersect. However, if we give incorrect

constraints, we find that the analysis aborts.

Appendix B shows the figures for assembly and the constraints imposed in the problem.

PLOTS:

The plot of the position (degrees) vs time for the rotating link is shown in Fig.4. This is the

driving conditions specified by the user for the analysis part. In Fig.5, we see the position of the

link-2 at various time of the analysis. Comparison of these two graphs can help us clearly

understand that at any particular angle of the rotating link what position the link-2 will be.


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Fig 4: Plot of the position (degrees) vs time for the rotating link

Fig 5: Plot of position of the link-2 at various time of the analysis


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Figure 5 shows a plot of position of the link-2 at various time of the analysis. A vertex was

assigned in the second link, which is the crank, and the analysis of the position of the y-

component gives us the graph by plotting against time. The analysis is carried out for the motion

of the links for 10 seconds.

The trace of points on the different links of the mechanism helps us understand better the figure5. Two points were chosen and the trace for the points was drawn for the analysis. Figure 6

shows the trace curves for two points.

Fig 6: Trace curves for points on crank and follower of the 4 bar mechanism

CONCLUSIONS:

Thus, the results are as shown above for the models that are created as described in Pro-E. The

position analysis for a four bar mechanism is carried out by a simple analysis is done in

Pro/Mechanism. The trace curves and the graphs show the position analysis of the mechanism.

The motion of the mechanism was captured in a playback file and as images. Some of thesequence of images is shown in Appendix C.


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APPENDIX A

The following figures show representations for each link in the order of Link1, Link 2, Link 4.

Link 1:

Link 2: (Link 3)


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Link 4:


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APPENDIX B

Assembly of the mechanism shown step by step with the constraints for each joint.


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APPENDIX C

The following sequence of images show playback of the motion of mechanism captured in

successive frames.

Fig : Sequence of images showing motion of the mechanism at: (a) t= 0s, (b) t=10s, (c) t=30s

and (d) t=50s

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