Electromyography-based Adaptive Cooperative Control for a Wrist Orthosis

This paper proposes an adaptive cooperative control method for a wrist orthosis, consisting of a trajectory tracking controller, an admittance controller integrated with an electromyography (EMG)-driven musculoskeletal model-based approach. The admittance controller adaptively alters the reference trajectory based on the estimated joint torque by the EMG-driven musculoskeletal model. The admittance parameters are regulated by accessing the wrist joint condition in real-time. Three experiments are conducted including, trajectory tracking control (TTC), fixed cooperative control (FCC), adaptive cooperative control (ACC) with two cooperative ratios of 0.3 and 0.6 respectively. Preliminary results demonstrate that the cooperative control strategies have smaller root-mean-square-errors compared with the TTC when the subject's intention is detected. The proposed method can modify the wrist orthosis's compliance in real-time in response to the wrist joint stiffness changes, which shows its potential to improve the efficiency and safety in rehabilitation.