Combining functional electrical stimulation and a powered exoskeleton to control elbow flexion

Functional electrical stimulation (FES) and robotic exoskeletons have each demonstrated promise in restoring functional reaching abilities to individuals with upper-limb paralysis. However, FES is difficult to control due to the constantly changing arm dynamics, and robotic exoskeletons have large power requirements. To achieve the benefits of each method, we have combined FES and a robotic exoskeleton as a hybrid system for controlling the elbow through a flexion and extension trajectory for seven healthy subjects. Compared to an FES-only strategy, our hybrid system resulted in a significant improvement in accuracy (94% reduction in rms tracking error). Compared to a robotic-exoskeleton-only strategy, our hybrid system reduced the required exoskeleton torque commanded by an average of 74%. These results are encouraging for the development of a hybrid FES and robotic exoskeleton system for full-arm control.