Phase-Based Haptic Feedback for Improved Neural Control of a Robotic Prosthetic Ankle: A Preliminary Study.

While neural control of robotic prosthetic legs through direct electromyographic (dEMG) control has shown promise for restoring human-prosthesis coordination, many persons with amputations struggle to generate the appropriate electromyographic (EMG) control signals for locomotion. The objective of this study was to develop a novel, phase-based haptic feedback system to train persons with transtibial amputations (PWTA) to produce appropriate muscle activation patterns for dEMG control of a robotic ankle while walking. The system provided (1) instructional feedback to guide the timing of residual muscle activation and (2) corrective feedback indicating whether the target activation pattern was achieved. The feedback system was preliminarily evaluated with three PWTAs. Biomechanics and EMG activation patterns were assessed before, during, and after feedback was provided. All participants altered their EMG activation patterns and stance duration was increased on both limbs. These changes led to all three participants increasing the step-to-step transition work done by the robotic prosthesis and two of the three increasing the peak robotic ankle power. Notably, all these changes persisted even after feedback was removed. These results demonstrate the feasibility of phase-based haptic feedback as a training tool for dEMG control of robotic prosthetic legs, improving human-prosthesis coordination.