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Project 2 Initial Conditions

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f14-jwhendricks2

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Unread post Fri Dec 12, 2014 8:53 pm

Project 2 Initial Conditions

For the initial conditions of the position should we use the equilibrium positions stated in Table 8.2.4? Also for the initial velocities Figure 8.2.5 shows an initial angular velocity of body 1 as 30 rad/sec. Should we use this initial velocity to solve for the other initial velocities?

Thanks,
Jake Hendrickson
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f14-jbhoward

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Unread post Fri Dec 12, 2014 11:13 pm

Re: Project 2 Initial Conditions

Jake-
To answer your question, I believe that the angular velocity of body1 at t0 is 30rad/s. Also it is stated in the Project statement that the initial angle of body1 is pi, meaning that the model is not in the equilibrium position.

I have a question of my own, though. There seem to be only 8 Kinematic constraints in this problem created by 1 absX, 2 absy, 2 rev, 1 absAngle. With that being said, how do we correctly solve the system? It seems like we may need more information to gather correct results

-James
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f14-tslininger

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Unread post Sat Dec 13, 2014 12:33 am

Re: Project 2 Initial Conditions

James,

It's dynamic analysis so it doesn't need to have DOF = 0 as Kinematics does (however, it needs qd0 values to make up for this). Also, in the project description it says "8 values for lambda", so I believe you have the constraints setup correctly.

~Tim
Tim Slininger
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Dan Negrut

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Unread post Sun Dec 14, 2014 4:51 pm

Re: Project 2 Initial Conditions

You have to decide how the mechanism is at the beginning of the simulation based on information provided in the problem.
Example: you have a pendulum with 1 DOF. It can start horizontally, vertically up, vertically down, etc. Your call. The same for velocities, you decide what velocities will be there (they must satisfy though \Phi_q qdot = nu).
this will give you q0 and qd0.
For the qdd0 and lambda0 you solve the linear system in the box in the NW corner of slide 21 of 12/09.
I hope this helps.
Dan

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