Optimized Proportional-Integral-Derivative Control Strategies and Simulation for Lower Limb Functional Electrical Stimulation

The aim of this paper was to propose a new control method of lower limb functional electrical stimulation (FES). Most traditional FES systems are controlled by open-loop pattern or feed for word pattern, here we presented a proportional-integral-derivative (PID) controller which was a closed-loop feedback controller and the parameters were optimized by back-propagation (BP) artificial neural network. Due to the nonlinear and time-varying characteristics of muscle and joint in FES, a novel musculoskeletal model was employed and the control algorithm was tested via simulation experiments. The control effect was evaluated by the position deviation between the target angle and real-time measured angle of knee joint. The results validated that the BP-PID controller performed fast and accurate in simulation tests.