Towards Universal Control System for Powered Ankle-Foot Prosthesis: A Simulation Study

In powered ankle-foot prostheses, multilevel hierarchical control systems are usually used with predetermined parameters (tuned during the prosthesis trial). Therefore, control systems cannot adaptively interact with terrains variation where control systems is most effective for ground level walking and less effective for ascending or descending stair/slop. In order to address the control system performance in ever-changing terrains, an adaptive mechanism should be included the control system structure. Here, we present a pilot study to illustrate the applicability of a genetic algorithm-based adaptive fuzzy logic control system. The design method could be divided into two stages: initial knowledge base and membership functions for the genetic pool on the basis of the analysis of biological ankle-foot behaviour. Additionally, the construction of genetic optimization mechanism rules and constraints (fitness function, mutation rats, replacement rate, etc.). Takagi-Sugeno-Kang fuzzy (TSK-fuzzy) inference system is selected because the system structure could depict the character of simple impedance control system. The control system and dynamic model were developed using C code and evaluated using MATLAB/Simulink (2019a).