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Hello,

I am performing Static optimization for a running motion. My optimization fails and I get this errors. Locking the pelvis_tild coordinate I get the errors. What can the mistake of my model could be? The muscles might be too weak and need additional joint toques?

time = 5.29 Performance = 4.02393e+07 Constraint violation = 8.43582
SimTK Exception thrown at InteriorPointOptimizer.cpp:264:
Optimizer failed: Ipopt: Maximum iterations exceeded (status -1)
OPTIMIZATION FAILED...

StaticOptimization.record: WARN- The optimizer could not find a solution at time = 5.3

The model appears unsuitable for static optimization.
Try appending the model with additional force(s) or locking joint(s) to reduce the following acceleration constraint violation(s):
pelvis_tilt: constraint violation = -0.00161129
pelvis_tilt: constraint violation = -0.00402324
pelvis_tilt: constraint violation = -0.00173374
pelvis_tilt: constraint violation = -0.0476457
pelvis_tilt: constraint violation = 0.00312214
pelvis_tilt: constraint violation = -0.00392425
pelvis_tilt: constraint violation = 0.159363
pelvis_tilt: constraint violation = -2.17386

Perhaps you have locked the pelvis_tilt coordinate yet are asking Static to find a solution where the acceleration of pelvis_tilt is nonzero? There is no solution to that problem.

I checked and I do not have the coordinate locked, and the the pelvis_tilt angles are within the range of the coordinate as well. I am increasing the muscle forces and max_control but still does not work. could it be this the problem? in case, Which criteria should I use to scaling the muscle forces?

In the first post you said "Locking the pelvis_tild coordinate I get the errors." Did you mean to say that you do not get the errors when the coordinate is locked? Regardless, you might check to ensure the reserve actuators are being added (assuming there is a FreeJoint between the pelvis and Ground).