simtk.org

Hi All,
I have some questions regarding building a controller using opensim. I am very sorry that my knowledge in opensim is very limited. Any information will be highly appreciated.

I am a very beginner SIMM user, in SIMM I have built a body model that stands on treadmill. I have created a motion file that moves the treadmill to one direction. Since the model feet have been fixed on the treadmill, the movement of the treadmill generates a response in the body model that I have calculated by the inverse/forward dynamics.
Since such a resulted motion in the body has a no exact control system (just a response to spring rule, as far as I understand), my plan is to test some strategies (program a controller) that change the body response based on the body center of mass (COM). For example, if the COM reaches to a range of value, run strategy one (move both arms in specific direction, for example), if COM goes far the above range, then run a strategy 2 (step with one leg in to a point X, for example).

My questions are:
Does opensim capable to program such a controller? where exactly to change or build such controller? Any guide?

Thank you very much for your help in advance.

Hi Fady,

Well, no relation between SIMM and OpenSim other than that we can import models built in SIMM. Proceeding with OpenSim, you can write a controller and use it in a forward simulation indeed. Two options are available, and both will require some C++ programming:
1. Write a main program, following the example included with the distribution under \sdk\APIExamples\ControllerExample

2. Write a plugin Controller class and specify it in the setup file for forward simulation.

Option 1. above requires less work as you don't need to worry about serialization to/from files etc. at the expense of a few more lines of code to setup and run a forward simulation.

Please consult the developer's guide and the example above in the distribution and let us know if you have any questions.

Best regards,
-Ayman

Thank you Dr. Ayman.
I will go ahead for your 1 option, and let you know the process.
thanks