Study of human-machine physical interface for wearable mobility assist devices

Abstract

A decrease in mobility, related to illness, trauma or ageing, negatively affects the quality of life of the rapidly growing elderly population. A promising solution to maintain this standard of living is powered wearable mobility assist devices. Although they have achieved technological breakthroughs in the last decade, their overall success is still hindered by their induced physical discomfort, which limits their effective and prolonged usage. The aim of this study is to achieve a comprehensive characterization of human-machine physical interface to further advance the performance of wearable mobility assist devices, specifically for the knee joint. This led the research group to design, fabricate, and instrument a low-cost modular knee orthosis testing apparatus with extension moment assist that allows multiple physical interface adjustment parameters. This device was conceived with the objective to conduct human testing while introducing design variables and operating parameters to evaluate device's performance. Using a force mapping apparatus and a motion capture system, the kinetic and the kinematic behaviour of the developed orthosis' physical interfaces were acquired. The results demonstrated varied impact on performance when introducing key design variables namely interface position, interface geometry, interface compliancy, interface hard-shell position, interface degree of freedom, and knee extension moment. This study provides an in-depth understanding of distinct user-device interface mechanisms and permitted an evaluation of optimum orthosis parameters to help further advance the state of wearable mobility assist devices.