An experimental robotic testbed for accelerated development of ankle prostheses

Biomechatronic devices show promise for restoring human performance, but development has been made inefficient by the need for specialized autonomous devices prior to testing benefits of proposed functionalities. This has severely limited exploration within and across intervention strategies. We have developed a laboratory testbed suitable for emulating and rapidly assessing wearable robot designs. The testbed is comprised of powerful off-board motor and control hardware, a flexible tether, and lightweight instrumented end-effectors worn by a person. We performed a series of benchtop tests to gauge mechatronic performance, and found significant improvements over prior candidate testbed platforms. In particular, this system has an unusual combination of low worn mass (less than 1 kg), high closed-loop torque bandwidth (17 Hz), and high peak torque (175 N·m), key to emulating specialized devices. We also performed walking trials to gauge dynamic torque control and versatility. Walking trials with a prosthesis end-effector demonstrated precise torque tracking (4 N·m RMS error), both in time and joint-angle space, and versatile mechanical behavior through systematic changes in high-level control law parameters. For example, we widely varied net ankle work (from -3 J to 9 J per step) using an impedance law relating joint angle and velocity to desired torque. These results suggest such testbeds could be used to emulate and evaluate novel assistive robot concepts prior to laborious product design.