How are excitations calculated in CMC?

[Michał Wołek]

As in thread title, how exactly are excitation levels calculated during CMC? I don't entirely understand.

In "how cmc works" it is said that they are calculated using static optimisation for all model actuators. But static optimisation calculates muscle activations (with known max isometric forces, current lengths and contraction velocities of muscles) by optimising cost function which includes muscle activation levels, not excitations. So does SO in CMC do the same, and then, as described in article from which the control schematic figure is taken, uses the relation between activations and excitations (https://simtk-confluence.stanford.edu/d ... n+Dynamics) to calculate excitations? Or is it done differently in OpenSim?

[Thomas Uchida]

This document provides some additional information: https://simtk-confluence.stanford.edu/d ... Theory.pdf

[Michał Wołek]

I was already reading this and still don't understand. What is exactly the function a(x)? Is is derived from those relations?
http://prntscr.com/q66eot
http://prntscr.com/q66ehz

[Thomas Uchida]

In the equation on the last line of page 2, "a(x)" is muscle activation (which is a function of excitation "x"). Activation is a state variable; its derivative is calculated as described on the "First-Order Activation Dynamics" page in the documentation (https://simtk-confluence.stanford.edu/d ... n+Dynamics) which is then integrated forward in time by a numerical integrator.