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Hello,

I am designing a benchtop robotic spine with a stiffness calibrated lumbar spine and pneumatic muscles. I divided the control system into two parts - high level and low level. Low level consists of individual muscle control and the high level is the logic behind the control signals given to individual muscles. The robot has to achieve multiple poses such as flexion-extension, lateral bending and axial rotation and the muscle placements mimic the major muscle groups in the human body responsible for these motions.

I am currently designing the high level control scheme and could use some help planning this out from you folks. Can open sim be used to model muscles with custom force-length curves, like in my case? Can I have an open sim model with these custom muscles and muscle placements? Such a model should take force on a vertebra as the input and generate spinal pose and muscle force. This muscle force and length data can be fed into the robot to achieve the required pose.

I would highly appreciate your inputs.

OpenSim is very flexible and can support these things, with varying levels of difficulty. A few notes and resources below:

- One place to start to see some of the flexibility is in the examples and tutorials. One of which is the Pulling Out The Stops: Designing a Muscle for a Tug-of-War Competition tutorial.
- The OpenSim Models documentation page
- Check out the documentation page for current muscle models, like the Millard model to see if they fit your need.
- If you still need a custom muscle model, this may require some work in C++. The GitHub page has instructions on how to build the project.