Development of pneumatic control system for walking assist using dual On/Off valves

In recent years, the population that requires assistance with walking has increased owing to a decrease in leg muscular power with age. To address this need, we develop a walking assist orthosis using a pneumatic artificial muscle to assist leg muscular power. Air pressure must be controlled and maintained at a stable level because the human walk is performed in a very short time interval, and becomes unstable with age. The objective of this study is to propose a new pneumatic control system with pulse-width modulation (PWM). In this system, two On/Off valves receive different PWM signals to control air pressure. We build theoretical equations and conduct experiments with actual walk data, and verify the proposed approach through theoretical and experimental studies.