Maximum Mechanical Energy and Mechanical-to-Electrical Energy Conversion Efficiency between Robotic Prostheses and Humans

Wearable robots involve human-robot interactions, and capturing the electrical energy from human dynamics during interactions is gaining increasing interest. However, previous studies have not thoroughly investigated the maximum mechanical energy and the efficiency of mechanical-to-electrical energy conversion between robotic prostheses and humans. In this study, the effects of motor rotation speed ωmo, pulsewidth modulation (PWM) duty cycle D, replacing mosfet and replacing a motor on efficiency η were investigated through theoretical analysis, a bench test, and walking experiments (N = 5). The theoretical analysis involved studying the energy flowchart during the mechanical-to-electrical energy conversion using a bench test. Then, walking experiments were conducted and the results showed that replacing a motor led to a 6% and 10% increase in energy regeneration at 1.3 and 1.1 m/s (self-selected), respectively. Based on the efficiency obtained from a bench test and walking experiments, the maximum mechanical power for a robotic prosthesis was obtained and ranged from 4.35 to 8.23 W, which showed the possibility of a 100% self-charged-powered robotic prosthesis. This study presents a feasible approach to analyze and improve the efficiency of mechanical-to-electrical energy conversion between robots and humans.