A Prosthetic Wrist Proprioceptive Feedback Closed Loop System based on Electrotactile Substitution For Transradial Amputees

The lack of sensory feedback in conventional commercial prosthetics fundamentally limits its fine motor control. To address this issue, this paper proposes a closed-loop proprioceptive feedback system of prosthetic wrist based on electrotactile alternative feedback. The system realizes the amputee’s EMG control of the prosthetic limb, and applies electro tactile stimulation to the residual limb to transmit the motion information of the prosthetic wrist to the amputee, including the acquisition and processing of EMG signal, EMG control strategy, PID speed closed-loop control of the motor, electro tactile stimulation strategy, and electro tactile stimulation module. The elimination of electrical stimulation artifacts is to control the EMG acquisition switch by timesharing multiplexing. After the performance and electrical safety tests of the system, six healthy volunteers and two amputees of the forearm were recruited to carry out the amputee’s control experiments on the prosthetic wrist under the conditions of providing visual feedback only and integrating visual and electrotactile feedback. The results show that the system can operate safely and effectively. Moreover, compared with only providing visual feedback, the system improved the action completion rate of the subjects by 22.22% without sacrificing the path efficiency and increasing the action completion time, and reduced the absolute angle deviation by about 2.37°. This study confirmed that the electromyographic prosthetic control system fused with electrotactile alternative feedback improved the control effect of the amputee’s prosthetic wrist flexion and extension movement.