Search found 99 matches

by Sina Porsa
Wed Apr 03, 2013 6:17 pm
Forum: OpenSim
Topic: Why does HuntCrossleyForce apply torques?
Replies: 3
Views: 455

Why does HuntCrossleyForce apply torques?

Hi, I just understood that the HuntCrossleyForce contact model applies both forces and torques to the contact sphere, While according to this paper, it should only be a spring and damper force actuator (not a torque actuator). http://www.stanford.edu/group/nmbl/publications/pdf/Sherm2011.pdf When I ...
by Sina Porsa
Sun Mar 24, 2013 4:13 pm
Forum: OpenSim
Topic: FD returns "Unknown exception" when using wrapping cylinder
Replies: 4
Views: 530

Re: FD returns "Unknown exception" when using wrapping cylin

Hi Ayman,
the Osim files are attached
Tnx
by Sina Porsa
Thu Mar 21, 2013 7:34 pm
Forum: OpenSim
Topic: FD returns "Unknown exception" when using wrapping cylinder
Replies: 4
Views: 530

Re: FD returns "Unknown exception" when using wrapping cylin

Hi Ayman and Thank you, Here is the simple version. If DefaultModel (line 8) contains wapping cylinders, this code will generate an error, but it will work if the loaded model on line 8 does not have wraping objects. thanks Sina P.S: How can I send you the osim files that I am using? I cannot upload...
by Sina Porsa
Mon Mar 18, 2013 4:31 pm
Forum: OpenSim
Topic: FD returns "Unknown exception" when using wrapping cylinder
Replies: 4
Views: 530

FD returns "Unknown exception" when using wrapping cylinder

Hi all. I am using a model which uses wrapping cylinders for some of the muscles. I am using this model to solve a dynamic optimization problem and I have two problems. First, let's have a look at my algorithem: - Load the Osim File - for i=1:1000 --- create a random muscle excitation pattern for ea...
by Sina Porsa
Mon Feb 25, 2013 10:14 pm
Forum: OpenSim
Topic: CoordinateLimitForce - nonLinear region
Replies: 2
Views: 342

Re: CoordinateLimitForce - nonLinear region

Thank you Sherm
by Sina Porsa
Mon Feb 25, 2013 9:00 pm
Forum: OpenSim
Topic: CoordinateLimitForce - nonLinear region
Replies: 2
Views: 342

CoordinateLimitForce - nonLinear region

Hi everyone. I am using CoordinateLimitForce to represent ligaments in my model. I know that this force has a constant stiffness except through the transition region which uses a non-linear function to change the stiffness smoothly from zero to the specified stiffness. I was wondering if I can know ...
by Sina Porsa
Wed Feb 13, 2013 9:07 pm
Forum: OpenSim
Topic: Does OpenSim report state equations?
Replies: 33
Views: 6490

Re: Does OpenSim report state equations?

Thankyou Ajay.
by Sina Porsa
Mon Feb 11, 2013 9:30 pm
Forum: OpenSim
Topic: Does OpenSim report state equations?
Replies: 33
Views: 6490

Re: Does OpenSim report state equations?

Hi again, I reckon it shouldn't be that tricky, because the forward dynamic tool needs the same ydot vector in order to integrate the state equations forward in time. Something like y(t+h) = y(t) + h*ydot( t, y(t), u(t) ) which is a first order Euler method. Of course the FD tool uses more accurate ...
by Sina Porsa
Mon Feb 11, 2013 6:01 pm
Forum: OpenSim
Topic: Does OpenSim report state equations?
Replies: 33
Views: 6490

Re: Does OpenSim report state equations?

Hi Sherm. In General, an optimal control problem is to find the optimum control u* which causes the system: ydot(t) = f (y(t), u(t), t) (eq.1) To follow the optimum trajectory y* that minimizes/maximizes a cost function. In (eq. 1) y is the state vector, u is the control vector and t is the independ...
by Sina Porsa
Sun Feb 10, 2013 10:23 pm
Forum: OpenSim
Topic: Does OpenSim report state equations?
Replies: 33
Views: 6490

Re: Does OpenSim report state equations?

Hi Sherm and thank you for the reply. I am using the OpenSim API to solve an optimal control problem and I am using an open source optimizer which is written in C++. (Everything is happening in C++). I will try my best to avoid a super technical question! I am trying to solve a constraint problem wh...