Optimal design of a linear actuator module considering the energy expenditure of powered exoskeletons for walking assistance

Abstract

Powered exoskeletons for walking assistance have recently shown rapid improvements in their actuating power and assisting algorithm, yielding them to help with daily tasks for people with gait disabilities. However, the exoskeletons are still not commonly used as daily walking aids. The energy expenditure of the exoskeletons during walking assistance should be reduced because it limits the user’s range of action. For enhancing the energy efficiency of the exoskeletons, the ankle joint, which contributes the most to walking energetics should be studied. In this paper, a linear actuator module for the ankle of WalkON Suit IV is analyzed in depth and its energy flow is systematically modeled. The optimal transmission ratio of the module was determined based on the proposed model to minimize the total energy loss. The actual efficiency, work, loss, and energy expenditure of the linear actuator module were measured to verify the result. The reduced energy expenditure during walking assistance is demonstrated by a walking experiment of the pilot with paraplegia while wearing WalkON Suit IV.