Design of MATLAB/OpenSim elbow flexion angular setpoint controller

Abstract

Movement simulation is an important tool for better understanding human biomechanics. Associated with appropriate control techniques, mathematical models can simulate physiological responses, such as the closed-loop positioning of a limb. This work aims to design an optimized proportional-integral-derivative (PID), as well as a state feedback controller, using MATLAB to obtain a physiologically plausible elbow position setpoint response. The plant to be controlled is an OpenSim model appropriate for the forward dynamics analysis. Activation and muscle contraction coupled with arm rigid body dynamics were identified by linear models with an accuracy of 74.77% and 93.07% respectively. A MATLAB/OpenSim interface was adapted to run the forward dynamics simulations. PID controller has shown a good robustness, better rise time and zero steady-state error. State feedback controller yielded a smaller overshoot, with good responses for the other design criteria and, conceptually, is a more meaningful representation of the biological controllers than the PID.