Trouble with Inverse Dynamics with exoskeletons
Posted: Fri Jun 18, 2021 8:49 am
Hello everyone. My name is Guillermo, and I started to work with OpenSim and Moco some months ago. I would like to ask for some piece of help for a project I'm involved in. I am working with the 3D model, subject_walk_armless.osim, and I've built an exoskeleton on it, as it can be seen in the picture.
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The exoskeleton is composed of two bodies in each leg, the upper bodies are connected to the hip through CustomJoints with 3 DOF each, all of them rotations, while the lower bodies are connected to the tibia through PointConstraints so as to close the loop.
First of all, I performed a Inverse Kinematic analysis in OpenSim by loading marker_trajectories.trc, obtaining the evolution of generalized coordinates in time. Then, I tried to perform a dynamical analysis in Moco so as to obtain generalized forces and torques. For that purpose, I built a Matlab script based in exampleMocoInverse.m, adapted to my problem, using my .osim model, and the .mot file I obtained by doing the Inverse Kinematics. The file can be seen in this picture.
Here the problems arrive. When I make the optimization problem begin, it never reaches a solution, the problem takes so many iterations until reaching the maximum number of iterations allowed, and I don't know what could be happening. I tried to reduce the time interval in the Moco script, and increase the mesh interval, but none of these worked to obtain a solution. Please, could someone give me an idea to solve this problem? Thank you very much.
. The exoskeleton is composed of two bodies in each leg, the upper bodies are connected to the hip through CustomJoints with 3 DOF each, all of them rotations, while the lower bodies are connected to the tibia through PointConstraints so as to close the loop.
First of all, I performed a Inverse Kinematic analysis in OpenSim by loading marker_trajectories.trc, obtaining the evolution of generalized coordinates in time. Then, I tried to perform a dynamical analysis in Moco so as to obtain generalized forces and torques. For that purpose, I built a Matlab script based in exampleMocoInverse.m, adapted to my problem, using my .osim model, and the .mot file I obtained by doing the Inverse Kinematics. The file can be seen in this picture.
Here the problems arrive. When I make the optimization problem begin, it never reaches a solution, the problem takes so many iterations until reaching the maximum number of iterations allowed, and I don't know what could be happening. I tried to reduce the time interval in the Moco script, and increase the mesh interval, but none of these worked to obtain a solution. Please, could someone give me an idea to solve this problem? Thank you very much.