Using EMG Biofeedback to Restore Closed-Loop Neural Control on a Powered Prosthetic Ankle

This paper aims to present that biofeedback based on electromyography (EMG) can help transtibial amputees to improve their capability to manipulate powered prosthetic ankles using Direct Electromyography (dEMG) control. First, we constructed a novel haptic based EMG biofeedback system composed of a HD haptic vest and an encoder that mapped EMG magnitude of residual shank muscles to tactile vibration patterns. Then we recruited six transtibial amputees and six non-disabled participants to conduct a position matching task, in which they conducted dEMG control on a powered prosthetic ankle with/without the biofeedback system after a brief acclimation. Impact of the EMG biofeedback system was evaluated based on their accuracy in matching specific targets in the position matching task. Our results demonstrated that 1) the EMG biofeedback can improve participants' target matching accuracy; 2) the biofeedback led to more separable EMG signals among amputee participants when they tried to reach different targets; 3) for amputees, the improvement is more clearly observed when matching towards dorsiflexion targets; and 4) high performance variation among amputees is observed. Our work also demonstrated the feasibility of providing effective proprioceptive feedback based on muscle contraction level without involving any surgical procedure on lower limb amputees.