The Swing Control of Knee Exoskeleton Based on Admittance Model and Nonlinear Oscillator

Abstract

It is important to control exoskeleton to act synchronously with the user for movement assistance. A knee exoskeleton was constructed for gait rehabilitation training, and a control method based on adaptive frequency oscillator (AFO) was presented for swing motion of knee exoskeleton. Firstly, during the learning mode, the user flexed and extended with the exoskeleton leg together, and the exoskeleton leg was not actuated. The phase of the exoskeleton angle extracted, and the envelope curve of the user’s EMG is generated based on AFO. Then, during power-assisted mode, the assistive torque is generated according to the angle phase on-line and the restructuring muscle torque. At last, the assistive torque as a feedback signal was input to the admittance model for the swing control of the knee exoskeleton. The experiments of swing control showed that knee exoskeleton can follow the user’s motion well.