Myoelectric Control of Exoskeleton Knee

Abstract

Exoskeleton is primarily designed to increase the physical performance of the wearer. Exoskeleton system are utilized for power-assist device, human-amplifier and rehabilitative device etc. Last three decades have witnessed significant development in the field of myoelectric control of rehabilitative and assistive devices. The major focus of the myoelectric prediction has been on predicting the motion modes for different locomotion terrain, gesture control and prediction of kinetic parameters like joint torque/force. The present research work is focused in the direction of myoelectric control of exoskeleton knee. The research work is divided in four parts namely, development of multichannel SEMG acquisition system to acquire SEMG signal from lower limb muscle while carrying out daily life activities, selection of optimal group of muscles to control the exoskeleton, predicting the knee angle information from SEMG signal of selected muscles and development of a simple prototype of knee exoskeleton. An eight-channel bioinstrumentation system based on ADS1298 was developed to record the SEMG signals from the selected lower limb muscles. Human lower limb consist of numerous muscles. One of the main considerations of the myoelectric controlled exoskeleton is the selection of muscles, which can control the exoskeleton system. Biological musculoskeletal model of human is highly redundant in nature. Apart from few exceptions, there exits more muscles than necessary to produce desired joint movement. The human lower limb has more than fifty muscles, but the human motion intent can be predicted by considering only some of these muscles. The research work proposes a principal variable based method for muscle selection. The selected group of muscles are sufficient to describe the knee movements. The force developed in the eighteen lower limb muscles while performing a sit to stand movement was considered as a base for muscle selection.