Search found 99 matches

by Sina Porsa
Tue Feb 02, 2016 11:11 pm
Forum: OpenSim
Topic: Does OpenSim report state equations?
Replies: 33
Views: 5608

Re: Does OpenSim report state equations?

If the control causes the muscle to generate forces those will in general affect many or all of the accelerations in x_dot. Those are coupled so can't be calculated individually. Or were you referring only to the Jacobian of the muscle force w.r.t. the control? It's because of the way that Thelen20...
by Sina Porsa
Mon Feb 01, 2016 4:56 pm
Forum: OpenSim
Topic: Does OpenSim report state equations?
Replies: 33
Views: 5608

Re: Does OpenSim report state equations?

Hi All, It’s exactly three years since when I started this thread and now it is converted to a very interesting discussion. I think we all do believe providing implicit formulation can highly help us to implement optimal control techniques. Here I want to ask for a feature which can highly improve c...
by Sina Porsa
Wed Oct 22, 2014 11:57 pm
Forum: OpenSim
Topic: any function to calc position of a point rel to ground?
Replies: 4
Views: 600

Re: any function to calc position of a point rel to ground?

Hi dear James I tried this method both in MATLAB and C++. IT works in MATLAB but not in c++, which is annoying! in my matlab script, after defining the joint angles in my defaultstate, I do this: for marker=0:11// I have 12 markers markerSet.get(marker).changeBodyPreserveLocation(defaultstate,model....
by Sina Porsa
Sun Oct 19, 2014 8:42 pm
Forum: OpenSim
Topic: any function to calc position of a point rel to ground?
Replies: 4
Views: 600

Re: any function to calc position of a point rel to ground?

Thanks James, that was a nice trick and in solved the problem!
Sina
by Sina Porsa
Tue Sep 30, 2014 7:17 pm
Forum: OpenSim
Topic: any function to calc position of a point rel to ground?
Replies: 4
Views: 600

any function to calc position of a point rel to ground?

Hi, I was wondering if there is any function to calculate position of a point relative to the ground assuming a known set of joint angles? I am an API user and I am using HuntCrossley contact forces. I need to calculate the position of the spheres respect to the ground(half space) within my script. ...
by Sina Porsa
Mon May 19, 2014 12:42 am
Forum: OpenSim
Topic: reporting Fiber force using Matlab API
Replies: 4
Views: 456

reporting Fiber force using Matlab API

Hi all I am trying to report fiber active and passive forces using matlab API. Here is my code: % load model osimModel = Model('test.osim'); % initiate states and set proper values defaultStates = osimModel.initSystem(); ... % geting the fiber force fiberForce = muscle.getFiberForce(defaultStates) B...
by Sina Porsa
Thu Jan 30, 2014 4:00 pm
Forum: OpenSim
Topic: Acceleration computation in BodyKinematic
Replies: 6
Views: 1134

Re: Acceleration computation in BodyKinematic

if you only need pos, vel and acc of COM then I would say it's easier and much faster to calculate them analytically. You have a simple linkage and you can easily drive the analytic equations for pos,vel and acc of COM using syms toolbox in MATLAB. You can find the method in any basic robotics book.
by Sina Porsa
Thu Jan 23, 2014 11:03 pm
Forum: OpenSim
Topic: Acceleration computation in BodyKinematic
Replies: 6
Views: 1134

Re: Acceleration computation in BodyKinematic

Hi everyone I am facing the same problem and it's interesting that this old post does not have any replies! I was wondering how does BodyKinematic calculates the position, velocity and acceleration of the COM. I ran BodyKinematic analysis on two different models, one with a proper foot-ground contac...
by Sina Porsa
Wed Aug 28, 2013 12:27 am
Forum: OpenSim
Topic: how can I define a PiecewiseConstantFunctio using Matlab API
Replies: 2
Views: 293

how can I define a PiecewiseConstantFunctio using Matlab API

Hi every one I am trying to create a PiecewiseConstantFunction within a Matlab script: PiecewiseConstantFunction(nNodes, tVec, U) where nNodes is an integer and tVec&U are two vectors (size = 1xnNodes) When I run my script, it returns this error: ??? No constructor 'org.opensim.modeling.PiecewiseCon...