SimTK Exception thrown at InteriorPointOptimizer.cpp:264: when running CMC tool

[Willem Ruseno]

So, I've been trying to run CMC tool for my gait analysis.

However, this error message appears at the same time of the CMC analysis if I set the analysis time from 0 to 1.03333 s (legible recorded motion). "Unable to find a feasible solution at time = 0.7."

However, the analysis would've completed if I were to set the time 0.6 to 1.03333 s (quite odd, considering that it passed the same period at which the OPTIMIZATION FAILED error occurs)

I thought it was because I didn't put in the ground torque/moment values, but with or without the error still appeared. Any idea what triggers this?


SimTK Exception thrown at InteriorPointOptimizer.cpp:264:
Optimizer failed: Ipopt: Restoration failed (status -2)
OPTIMIZATION FAILED...
CMC::computeControls: Optimizer could not find a solution.
Unable to find a feasible solution at time = 0.7.
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.

[Thomas Uchida]

One possible reason is that too much error is accumulating in the tracked trajectory. You could try comparing the target and tracked kinematics to see whether one of the coordinates is diverging substantially just before 0.7; if so, you could increase the weight of the corresponding tracking task.

[Willem Ruseno]

Thomas,

Thank you for your insight. Apparently, the error was solved by putting any other value except 0 s for the starting time. The CMC ran without any error interruption.

However, regarding the tracking task weight, will increasing the value be able to help increase the accuracy of the muscle activation recorded? Provided that the external force data is accurate, but with IK results that have underwent quite a magnitude of corrections.