Static Optimization conditions

[Mohammadhossein Akhavanfar]

Hi,

Based on the explanation in this documentation:
https://simtk-confluence.stanford.edu/d ... tion+Works

OpenSim minimizes an objective function for muscles' activation subject to that active muscle forces balance the external moment (i.e. τj which is the generalized force acting about the jth joint axis).

While we know in each time step
[muscle moment arm] * [Fpassive+Factive] = [External moment]

Why OpenSim only considers active muscle forces in the above equilibrium equations?

Thank you in advance for your help,

Mohammad

[Thomas Uchida]

I think Static was originally just part of CMC's internal calculations and only later was created into a separate Tool. Presumably, the design of the algorithm was influenced by its original design and included corresponding assumptions (perhaps, e.g., passive forces are not dominant). You might look at some papers that use Static, as they might include rationale for why Static is appropriate for their application. Depending on what you're trying to simulate, you might want to run tests to compare Static and CMC.

[Mohammadhossein Akhavanfar]

Hi Tom,

Thank you for your response. I see your point.