Powered Human Gait Assistance

Abstract

Adaptation of powered actuated devices to assist elderly or weak individuals implies special design requirements. These actuators must be powerful enough to perform the tasks required of them yet remain efficient, lightweight and safe to its wearer. A spring-based actuator can contribute to all of these things. Springs are inherently powerful and lightweight. For the examples actuators developed above, the springs have `power to weight' ratios of approximately 300,000 W/kg. Springs are an efficient form of energy storage. For unstressed spring steel, its efficiency is reported to be 99.9% (Carlson, 1980). Springs are by nature compliant and back drivable, thus providing a natural measure of safety. Additionally, the other mechanical actuator elements, like a lead screw, can be designed to promote these design requirements as well (Hollander and Sugar, 2006a). Methods that include the implementation of springs into wearable system designs are necessary to meet these special design requirements. The development presented here offers a robust approach to the design of actuators that fit a variety of powered assistance situations. The creation of lightweight and practical, powered assistance actuators is possible with today's technology. The era of robots serving a role in everyday life is close at hand and will likely be in the form of powered wearable assistance.