Does BushingForce have bug?

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Sina Porsa
Posts: 99
Joined: Thu Feb 03, 2011 7:21 pm

Does BushingForce have bug?

Post by Sina Porsa » Thu May 26, 2011 12:37 am

Hi,
I am not sure if this is a bug or not.
This is my OSIM file to define a BushingForce in Arm26.osim
.
.
<BushingForce name = "DirectionY">
<isDisabled> False </isDisabled>
<body_1> ground </body_1>
<body_2> r_ulna_radius_hand </body_2>
<location_body_1> (0 0 0) </location_body_1>
<orientation_body_1> (0 0 0) </orientation_body_1>
<location_body_2>(-0.00110000 -0.23559000 0.09430000)</location_body_2>
<orientation_body_2>(0 0 0)</orientation_body_2>
<rotational_stiffness>(0 0 0)</rotational_stiffness>
<translational_stiffness>(0 100 0)</translational_stiffness>
<rotational_damping>(0 0 0)</rotational_damping> <translational_damping>(0 0 0)</translational_damping>
</BushingForce>
.
.
so it has only transitional stiffness in Y direction. But When I use "property viewer"in GUI it shows this as transitional stiffness (100 0 0). in puts 100 in X direction in stead of Y. It also changes the location on body 2.
I am not sure if it is a bug, or I do not know how to use bushing force.
Regards,
Sina

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Ayman Habib
Posts: 2248
Joined: Fri Apr 01, 2005 12:24 pm

RE: Does BushingForce have bug?

Post by Ayman Habib » Thu May 26, 2011 9:47 am

Hi Sina,

I would take out the extra "()" around various quantities, and just to be extra safe, use decimal points where needed. Please try that and let me know how it goes.

Best,
-Ayman

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Sina Porsa
Posts: 99
Joined: Thu Feb 03, 2011 7:21 pm

RE: Does BushingForce have bug?

Post by Sina Porsa » Thu May 26, 2011 11:06 pm

Hi Ayman,
Thanks, your suggestions solved the issue,
I used "()" as it was mentioned in ( help --> available objects ) in GUI.
Thanks for your help
Regards,
Sina

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Gregory Philips
Posts: 33
Joined: Thu Aug 07, 2008 12:49 am

RE: Does BushingForce have bug?

Post by Gregory Philips » Fri May 27, 2011 2:39 am

Hi Sina.

I am trying to create a new force the upper extremity model and I am using your BushingForce as the template. I wanted to confirm a couple of things with you about it.

1) When you enter the line name=DirectionY are you specifying the axis on which the force acts?
2) Are the location and orientation parameters you have used the same as the joint in the model?
3) You specified the stiffness and the damping parameters for the force but not the magnitude. Do you have the magnitude at everytime instant stored in a .mot file?

Thanks.

Regards,
Gregory Philips.

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Sina Porsa
Posts: 99
Joined: Thu Feb 03, 2011 7:21 pm

RE: Does BushingForce have bug?

Post by Sina Porsa » Fri May 27, 2011 6:48 pm

Hi Gregory,
1- no, directionY is the name of the bushing force which appears in the GUI. this linespecifies the stiffness of spring in each direction: <translational_stiffness> 0 100 0 </translational_stiffness>

2- No, I used a random location. I just wanted to check how "BushingForce" works.

3- I cannot understand your question, The bushing force acts like spring force. So the magnitude of force would be (stiffness*distance between frames)

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Gregory Philips
Posts: 33
Joined: Thu Aug 07, 2008 12:49 am

RE: Does BushingForce have bug?

Post by Gregory Philips » Sat May 28, 2011 10:43 am

I see. I wanted to create parameters for the force and wanted to know what kind of parameters can be added.

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