A Particle Swarm Optimal Control Method for a Direct-Drive Electro-Hydraulic Ankle-Foot Prosthesis

Existing powered ankle-foot prostheses (PAFP)have relatively low power density ratios and poor performance in practical applications. Direct-drive electro-hydraulic technology features high power density, a closed structure, and small volume. This paper presents a PAFP system based on direct-drive electro-hydraulic technology. Instead of the common practice of oil replenishment through replenishment valves, the system installs accumulators on both sides of the hydraulic circuit. This design enables the recovery of energy and amplification of power, while reducing the complexity of the hydraulic system and manufacturing costs of the PAFP system. Based on the establishment of a simulation model for the position control system of a PAFP, control parameters were adjusted and optimized through a PID controller and a Particle Swarm Optimization algorithm, thus achieving precise reproduction of the input angle control commands. Simulation analysis of the prosthetic power verified that the designed PAFP exhibits enhanced performance in terms of energy output.