Design Of The Control System For The Compliance Of The Lower Extremity Exoskeleton

The lower limb rehabilitation exoskeleton is a medical device used for rehabilitation training of patients with movement disorders.It is mainly composed of a mechanical structure body and a control system.In this study,the lower limb rehabilitation exoskeleton was the research object.The research goal was to provide comfortable and safe rehabilitation training.By comprehensively considering the mechanical structure of lower limb rehabilitation exoskeleton and the physiological structure of human lower limbs,the human-machine coupling dynamics model was constructed.The intelligent control strategy with human-machine collaboration was established to realize the active compliance rehabilitation training.The main contents of this study include:1.Firstly,the mechanical structure and electrical composition of the lower limb rehabilitation exoskeleton were systematically described.The lower limb exoskeleton human-machine coupling model based on the spring model was constructed.Combined with the Lagrange method,the dynamic equation of the human-machine coupling model was derived,and the motion simulation was carried out on Adams software.The correctness of the human-machine coupling model was verified.And an accurate controlled object model was provided for the construction of the subsequent control system.2.Due to the real-time change of the interaction force between the human body and the lower limb exoskeleton,in this study,the advantage that impedance control can realize the dynamic adjustment of human-machine interaction force and motion position was fully used.A torque feedback compliance control method based on impedance control was proposed to realize dynamic adaptive adjustment of human-machine interaction force and improve the compliance of human-machine system.In order to verify the effectiveness of the control system,a lower limb exoskeleton single-joint model was built.The effects of inertial parameters,damping parameters and stiffness parameters on impedance control performance were analyzed through simulation experiments.And a set of optimal impedance parameters with good human-machine coupling was obtained as the basic parameters for real-time parameter adjustment of subsequent intelligent control algorithms.3.Aiming at the problems of low tracking accuracy and long adjustment time in the lower limb exoskeleton torque feedback system based on impedance control,a lower limb exoskeleton torque feedback control method based on RBF-fuzzy variable impedance was proposed.The impedance parameters were dynamically adjusted by fuzzy control,and the uncertainties in the control system model were compensated by RBF neural network.By constructing a lower limb exoskeleton single-joint model simulation experiment,the effectiveness of fuzzy control and RBF neural network in reducing tracking error and shortening adjustment time were verified.Finally,the Lyapunov equation was used to verify the stability of the control system.4.In order to verify whether the lower limb exoskeleton torque feedback control method based on RBF-fuzzy variable impedance could realize the compliance control of the human-machine coupling model,a united simulation platform of Adams and Matlab/Simulink was built.Compared with torque feedback compliance control and torque feedback control based on impedance control,the simulation results show that the tracking performance of the system and the consistency of human-machine motion were significantly improved.