An admittance controller based on assistive torque estimation for a rehabilitation leg exoskeleton

Abstract

A rehabilitation exoskeleton leg was constructed for gait training, and a method for exoskeleton leg swing control based on admittance model was studied. The man–machine interaction torque, the inertia compensator torque, and the exoskeleton’s assistive torque act as the inputs to the admittance control system for realizing the effective assistance to the wearer. The exoskeleton’s assistive torque is generated by estimating net torque exerted by the muscle based on adaptive frequency oscillator. A variable swing frequency experiment for simulating physical rehabilitation exercise was implemented. The results show that the inertia compensator adjusting the compensation varies with the swing frequency. The control system provides effective assistance to the wearer. The coordinated control experiment of hip and knee joints was also implemented. The results show that the interaction forces are all controlled in a reasonable and small range, and there is a good coordination between the hip joint and knee joint during swing motion.