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Initial setup for force (Project 2)

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f14-aahmed22

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Unread post Tue Dec 16, 2014 2:37 am

Initial setup for force (Project 2)

Hello,
My results for q double dot and lamda diverge, and after trying everyting I'm beginning to think the problem is in how I define the initial configuration and forces. The weird thing is that it converges in the beginning and only starts to diverge when N=9.

So I want to make sure of the system setup:
1) when we say that the gravity acts in the x direction, doesn't it only mean that there is no -9.81 y directed component of the force? or is there an additonal force component we need to add in addition to the Fc function?
2) The Fc funciton gives only one force equation depending on the increase in x3 and if x3dot is greater than zero, right? so why is it said in the project pdf that the my_force file should output a 2 dimentional force? this is what makes me feel i'm missing something.

Can anyone help me?

Thank you
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Dan Negrut

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Unread post Tue Dec 16, 2014 11:46 am

Re: Initial setup for force (Project 2)

1) the force has two components, of which one is 9.81 and the other one zero
2) same as before. Fc gives you one nonzero component, the other one is zero. Based on this 2D force you compute the generalized force associated with this applied force.

The divergence issue. Do you mean that it diverges after 9 steps?
Can you plot the results you get for the first 9 steps to see if other colleagues get the same thing?
Dan
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f14-aahmed22

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Unread post Tue Dec 16, 2014 11:56 am

Re: Initial setup for force (Project 2)

Professor, Can you explain this further? we have one force and one torque in the forces section of the adm file right? the force is the Fc, in which the x component is the equation of Fc and the y component is zero, where is the 9.81? in another PointForce element you mean?
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f14-aahmed22

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Unread post Tue Dec 16, 2014 11:59 am

Re: Initial setup for force (Project 2)

Or does the gravity acting in x mean that the whole system coordinates are shifted making Fc act downwards with the gravity?
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f14-mewalczak

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Unread post Tue Dec 16, 2014 12:21 pm

Re: Initial setup for force (Project 2)

I was under the impression that F_c acted in the opposite direction as gravity so the Qa for x3 would be mg - Fc. But then again my code also diverges so Im not sure.

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