<t>Hi Ayman,<br/> <br/> I am just applying a muscle force. No external loads. The joint constraints are satisfied. I think the model is falling under gravity. However, I don't want this to happen. I'm done another simpler model: pelvis, femur, tibia, no muscles. If I do a forward simulation with no ...

I'm trying to turn on one muscle with an activation that I make up, and run a forward dynamics simulation. However, the whole body falls under gravity and breaks apart, even when I try to lock the joints. Any suggestions?

Hello,

In response to segment origins. I too am working with a coordinate system different than the one used in OpenSim. I am using local frames from Sheehan's dynamic MRI papers on bone tracking. The only way I found to do this was to modify the .vtp file.

Anne

I can't get PointKinematics to work. It always crashes.

I am trying to run CMC on a simple knee flexion/extension task with every gen coord locked at 0 (except for flexion extension). I have a motion file that just prescribes knee angle. When I try to run CMC, it translates the whole model. How can I fix this? The pelvis-ground lock isn't working.

Is there a working ligament model released yet with OpenSim?

<t>Hello, <br/> <br/> I'm am trying to flex/extend the knee and leave the patella to do whatever it wants while contacting the femur. I have a muscle attached from femur to patella, patella to tibia, and between the femur and tibia. Is there anyway I can just specify the knee flexion and measure wha...

I added it to my .osim file at the end as an 'actuator'. However, it doesn't show up in the GUI in the forces tab. How do I know I have added this torsional spring?

I think I figured out how to add SpringGeneralizedForce. However, I'm not sure how to find in the documentation how this actuator computes the forces to apply. Since it's a spring, is it F = stiffness*(coord-restlength)?

Torque Actuator is in the examples as a default but it doesn't show how to call it. I think I need the generalized spring force, but I'm not sure how to put it in the .xml or .osim. Any examples I can look at on how to 'call' it in my model file?