DESIGN AND TESTING OF A HIGH-POWER PNEUMATIC ANKLE EXOSKELETON

Abstract

A pneumatic ankle exoskeleton is designed, constructed, and tested to study the use of pneumatic artificial muscles (PAMs) and force sensitive resistors (FSRs) for increased running and jumping performance. PAMs are selected for their low weight, high power density, and natural compliance, all advantageous for exoskeleton applications. FSRs are selected as they can be packaged between the sole of the wearer’s foot and a ground plate, enabling toe push-off force to be measured. Toe force measurement is an uncommon parameter to be measured on most lower extremity exoskeletons. A closed loop force controller is implemented using the FSRs as an input force and a strain sensor embedded in the PAM as the feedback sensor. This architecture is shown to achieve a high bandwidth, capable of following trajectories similar to that of a running gait or jumping force profile. The FSRs are shown to exhibit low hysteresis and high dynamic response, and moderate linearity compared to traditional strain gauge based transducers (SGBTs). Special attention is given to keep the structure realistically lightweight, as well as select and characterize sensors that could be realistically packaged in an end-use application.