Increasing elbow torque output of stroke patients by EMG-controlled external torque

A control algorithm for using homogenic EMG to control external assisting torque is developed for improving the elbow capability of stroke patients. The control signal to the manipulator is the difference between the weighted biceps and triceps EMG, so that the system moves with the forearm and provides assisting torque proportional to the voluntary effort. A nonlinear damping structure, mimicking physiological damping and incorporating the effects of cocontraction, was also included in the command for improving joint stability. The control algorithm has the advantage that the control is natural to the patient so that the learning process is simple. We tested the control algorithm in 5 normal subjects and 2 stroke patients. The results showed that the system could assist the subjects in completing work (tracking under loads) with less effort and without sacrificing performance.