Simple Question: Non-linear torsional spring with CoordinateLimitForce?

[Levi Schilder]

Hi everyone,

Currently, I am trying to create a model of a body with a prosthetic leg that has actuators in the knee and a spring in the ankle.

The issue is: I need to implement a torsional spring in the prosthetic ankle. I used one of the basic tutorials of opensim to implement a CoordinateLimitForce in the ankle. This has a 'upper stiffness' and a 'lower stiffness'.

However, I need to implement a torsional spring that has non-linear characteristics. I already have a data sheet with all the torques of the ankle spring related to the ankle angle.

So my question: How can I best implement a torsional spring with non-linear stiffness?

Thank you in advance.

[Carmichael Ong]

Depending on your exact needs, you might want to look at ExpressionBasedBushingForce first and see if that works for you:
https://simtk.org/api_docs/opensim/api_ ... Force.html