Static Optimization Solves, but CMC does not

[Jonathan Mortensen]

Hi everyone,

I am creating a dynamic head and neck model. When I run static optimization, it solves with no problems. However, when I run CMC I get this error:

CMC.computeControls: ERROR- Optimizer could not find a solution.
Unable to find a feasible solution at time = 1.88833.
Model cannot generate the forces necessary to achieve the target acceleration.
Possible issues: 1. not all model degrees-of-freedom are actuated,
2. there are tracking tasks for locked coordinates, and/or
3. there are unnecessary control constraints on reserve/residual actuators.

I have reserve actuators on each degree of freedom, each with max activation levels set to infinity and -infinity. No coordinates are locked, and I don't have any control constraints.

To make things weirder, when I disable all muscles, CMC solves quickly. I have tried running it with Thelen and Millard muscles models. Does anyone have any idea what I am doing wrong?

[Dimitar Stanev]

Hi,

It is possible that the muscle parameters of your model are not correct. For example there may be muscles that develop large passive forces. You can also test with the slow target option in CMC.

http://simtk-confluence.stanford.edu:80 ... +CMC+Works

Best

[Jonathan Mortensen]

Thanks for the reply! I figured it out just a few minutes ago, and you were correct. Two of my muscles had incorrect parameters and had very large passive forces.