Feasibility study on echo control of a prosthetic knee: sensors and wireless communication

Abstract

This paper outlines sensory system specifications and requirements to measure lower limb inclination angles, and addresses a novel method of human gait phase recognition necessary for cadence control. The implementation of a wireless system to transfer data between the active prosthetic knee and a healthy leg is discussed. A control mechanism is developed that takes advantage of an adaptive-network-based fuzzy inference system (FIS) to determine knee torque as a function of the echoing angular state of the able leg. The FIS membership function parameters and rules define the knowledge-base of the system. This knowledge is based on existing experience and known facts about the walking cycle. The RMS error of the testing data for the body-mass-normalized knee torque and the knee angle were calculated as 0.1269 (N m/kg) and 3.2784 (degree), respectively, i.e., 14.16% with respect to the required range of 0.896 (N m/kg), and 5.10% with respect to the travelling range of 73.01 (degree). The introduced post processing block plays a significant role in reducing the magnitude of the aforementioned errors.