Disclaimer: This is a duplicate of this, as I figured it was more appropriate to post directly on the OpenSim website. Feel free to ask me to delete it if you think I should. https://simtk.org/plugins/phpBB/view...p?f=91&t=15230

Dear all,

I am currently reading this article, and I am quite puzzled with the amount of solutions there are to the kinematic problem. I am wondering which one of these OpenSim uses.

- It is definitely a numerical approach, rather than analytical
- There is no learning, so it is not a data-driven approach
- I don't think there is any heuristics involved
- Gauss-Newton optimization converges faster, only if they do. OpenSim is robust enough that I would think it uses a Jacobian approach instead.

However, nowhere in the OpenSim papers nor in the documentation, can I see any mention of the Jacobian. I think I gathered that it is a non-linear least-square problem, solved with global optimization with the Levenberg-Marquard algorithm. How does that imply that this uses a Jacobian method?

Subsidiary question: are forward and direct kinematics really synonym? The 6DoF way of solving joint angles (which is analytical, rather than numerical) seems to be sometimes called direct kinematics.
If so, then I suppose it is wrong to say that inverse kinematics solve joint angles from point coordinates, while forward/direct kinematics solves point coordinates from joint angles?