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Hi

I want to simulate pneumatic actuator in opensim. In my experiment the pneumatic actuator is attached from waist to knee and it helps in knee extension supporting upper limb muscle in during gait cycle. How can I simulate the behavior of pneumatic muscle in opensim.

My goal is to use opensim to study effects of actuator on muscle activation and force generation. I used pathspring with model and data provided in working with static optimization tutorial, but with the pathspring acts like actuated all the time. I want to control the actuation by e.g. when the knee flexion is completed or toe off position.

I looked at customized actuator example but did not get any clue.

Thanks
Chetan

Hi,

You will have to implement the force characteristics on your own, by extending the appropriate class.

https://simtk.org/api_docs/opensim/api_ ... ml#details

I want to control the actuation by e.g. when the knee flexion is completed or toe off position.

You will need a controller, that will detect these events and provide the appropriate input to your custom muscle.

Best

Dimitar is correct. However, it may be simpler to use your custom Controller with the pre-existing PathActuator instead of your own custom actuator.

Thanks for the comment and suggestion.

At first I am thinking to use ClutchedPathspring with custom controller to decide when to enable the clutch flag. In my case I need to activate the spring when toe off(initial swing). But I have a one question here, how to run static optimization with custom controller or actuator ? I could not find any examples or hint in the documentation.

Thanks in advance
Chetan

But I have a one question here, how to run static optimization with custom controller or actuator ? I could not find any examples or hint in the documentation.

You need to initialize the AnalysisTool and add StaticOptimization.

Thanks I was able add controller to the model and then run static optimization. I could see better results after using clutchedpathspring over pathspring.

Thanks for all the help. I will now try custom actuator.

-Chetan

How to add controller to cluthchedPathSpring ? Can any one guide me to example script?

Thanks & Regards,
Karthick.