forward kinematics (jacobian) calculation and muscle jacobian (muscle moment arm) calculation
Posted: Mon May 27, 2024 10:55 pm
Hello,
I am new to OpenSim and SimTK and I am trying to use upper extremity dynamic model to simulate human movements and get two matrixes ( Jacobian J and muscle Jacobian Jm).
The Jacobian is a matrix of partial derivates that relates small end-effector (hand) velocity V with small joint angle changes dq. (V = J*dq). The entire model contains 15 degrees of freedom (DOF), but I am only interested in 7 of them: 3 DOFs at the shoulder, 1 DOF at the elbow, 1 DOF for forearm pronation/supination, and 2 DOFs at the wrist. Is there a way to obtain the Jacobian matrix from the shoulder to the elbow, J=6*7 (instead of the full Jacobian)? If there is no built-in function for this, how can I extract the Denavit-Hartenberg (DH) parameters corresponding to these 7 DOFs from the scaled .osim file to perform forward kinematics calculations?
Jm is similar to the muscle moment arm and is a matrix of partial derivatives that relates small muscle length changes with small joint angle changes, partial(L_muscle_i)/partial(q_j). Here, I am also only interested in the 7 degrees of freedom mentioned in the previous paragraph and certain muscles in the upper arm. Could the experts please advise me on how to calculate this?
Many thanks!
I am new to OpenSim and SimTK and I am trying to use upper extremity dynamic model to simulate human movements and get two matrixes ( Jacobian J and muscle Jacobian Jm).
The Jacobian is a matrix of partial derivates that relates small end-effector (hand) velocity V with small joint angle changes dq. (V = J*dq). The entire model contains 15 degrees of freedom (DOF), but I am only interested in 7 of them: 3 DOFs at the shoulder, 1 DOF at the elbow, 1 DOF for forearm pronation/supination, and 2 DOFs at the wrist. Is there a way to obtain the Jacobian matrix from the shoulder to the elbow, J=6*7 (instead of the full Jacobian)? If there is no built-in function for this, how can I extract the Denavit-Hartenberg (DH) parameters corresponding to these 7 DOFs from the scaled .osim file to perform forward kinematics calculations?
Jm is similar to the muscle moment arm and is a matrix of partial derivatives that relates small muscle length changes with small joint angle changes, partial(L_muscle_i)/partial(q_j). Here, I am also only interested in the 7 degrees of freedom mentioned in the previous paragraph and certain muscles in the upper arm. Could the experts please advise me on how to calculate this?
Many thanks!