FES controller design based on threshold control theory for single joint movement

The threshold control theory is applied to build a physiology-based FES controller. The proposed control strategy is tested in simulation study with an integrated musculoskeletal model. The results suggest that the controller based on the threshold control theory alone can realize the task with small feedback delays. However, it is not capable to produce the movement fast enough to match the desired trajectory. Thus two extensions to improve the performance are proposed. Firstly, the feedback on actual movement velocity is replaced by the differences between the actual and desired velocities. Secondly, the feedback of joint angular acceleration is introduced to calculate the dynamic threshold. Simulation results suggest that such extensions can 1) improve the movement speed; 2) reduce the response time; and 3) reduce influence of external perturbation and feedback delays.