Optimization Parameters of PID Controller for Powered Ankle-foot Prosthesis Based on CMA Evolution Strategy

Optimization parameters of PID controller based on Covariance Matrix Adaptation Evolution Strategy (CMA-ES) is presented in this paper. It is used to solve the problem of torque control for powered ankle-foot prosthesis. Original optimization parameters method of PID controller for powered ankle-foot is time-consuming and cannot get satisfied control effect. The parameters of PID control are used as an individual of CMA-ES in this paper. Appropriate fitness function is selected to adjust the PID parameters online. Step signal and torque approximation are used as the system input to verify the controller performance. In unit-step response, the overshoot of original PID is 15 times as much as it of CMA-ES PID, the setting time of original PID is 6 times as much as it of CMA-ES PID. In device torque response, the output of CMA-ES PID is stabilized throughout the control process. These indicates that CMA-ES PID is an effective control strategy for torque control of powered ankle-foot prosthesis.