Abstract
Objective We aimed to develop a system for people with amputation that non-invasively restores missing control and sensory information for an ankle-foot prosthesis. Methods: In our approach, a wrist exoskeleton allows people with amputation to control and receive feedback from their prosthetic ankle via teleoperation. We implemented a position control scheme and torque control scheme, both of which provide haptic feedback at the wrist. We also investigated two low-level position controllers, and measured tracking error and frequency response for each system component. To demonstrate feasibility and evaluate system performance, we conducted an experiment in which one participant with a transtibial amputation tracked desired wrist trajectories during walking, while we measured wrist and ankle response. Results: Benchtop testing demonstrated that for relevant walking frequencies, system error was below human perception error. During the walking experiment, the participant was able to voluntarily follow different wrist trajectories with an average RMS error of 1.55° after training. A position control scheme using feedforward control with iterative learning and haptic feedback at the wrist resulted in the most accurate ankle tracking (RMS error = 0.8°). The torque control scheme achieved an ankle torque RMS error of 8.3 N m. Conclusion: We present a system that allows a user with amputation to control an ankle-foot prosthesis and receive feedback about its state using a wrist exoskeleton with accuracy comparable to biological neuromotor control. Significance: This bilateral teleoperation system enables novel prosthesis control and feedback strategies that could result in improved prosthesis control and aid motor learning.
Competing Interest Statement
The authors have declared no competing interest.
