Forward Dynamic Controller in CMC

[Robert Förster]

Hi guys,

I am doing research on a lower limb model and I am interested in the achilles tendon force.

At the moment I am trying to understand how CMC works and the user's guide helps me a lot.
But one thing I do not understand is how the "standart forward dynamic simulation" in CMC works.(https://simtk-confluence.stanford.edu/d ... +CMC+Works)
It is the third step of the CMC algorithm Is it the same procedure as in the forward dynamics tool? (https://simtk-confluence.stanford.edu/d ... mics+Works)
In my opinion this part of the documentation of CMC is a bit too short.

Best,
Robert

[Dimitar Stanev]

CMC is a closed-loop forward dynamics method. There are two controllers, name the tracking controller that compares the simulated and desired trajectories of the markers and the static optimization controller that computes the muscle excitation required to achieve the desired acceleration of the tracking controller. The muscle excitation are fed to the model which is then simulated in a forward dynamics manner.

[Robert Förster]

Thanks for your reply. I am struggling with this expression "forward dynamics manner". How do you get the coordinates and velocitys from the muscle excitations?
Thanks!

[Dimitar Stanev]

You activate the muscles, they produce force. This force accelerates the body segments. For given initial conditions you can integrate the acceleration and solve for the positions and velocities. Think of the Newton's second law m * a = f. Given f, a = f / m.