Interactive Operational-Space Controller for OpenSim

Project Overview

The purpose of this project is the implementation of operational-space control in OpenSim. This kind of controller has a number of advantages over commonly used generalized coordinate (torque) controllers:

• Generates more "natural human motion"
• Generalized coordinate (GC) torques are computed implicitly
• Dimension m = #task_coordinates << n = #joint_DOF
• No inverse kinematics required

It is particularly suitable for many biomechanical applications, such as

• Reaching
• Manipulation
• Athletics
• Marker tracking

The implemented framework includes an operational-space position task controller and a posture controller that operates in the task's null-space. For a more detailed mathematical background please refer to the attached presentation or the References section.

Plan for Success

1. Set up Simbody and OpenSim on Ubuntu -- DONE (I will make a tutorial on confluence)
2. Generate simple articulated body system as a test platform -- DONE
3. Set up control inputs to generalized coordinates (GC) -- DONE
4. Set up GC controller (nonlinear dynamic decoupling) -- DONE
5. Un-hardcode to make GC controller applicable to arbitrary systems -- DONE
6. Set up operational-space controller -- DONE
7. Implement null-space damping -- DONE
8. Implement posture controller -- DONE
9. Set up keyboard input to make the simulation interactive -- DONE
10. Set up more complex models (arm, whole body) -- DONE
11. Clean up code and improve performance --DONE

Final Presentation

Tutorials

• Operational-Space Controller API Tutorial

Acknowledgements

I would like to thank the BIOE485 teaching team for their support throughout this project, in particular Michael Sherman, Tim Dorn, and Tom Uchida (randomly arranged).

References