Model-Based Active Impedance Controller Development of the Exoskeleton Rehabilitation Robot (ERRobot) for Lower-Extremity

Abstract

This paper presents a hierarchy and hybrid control architecture for a wearable exoskeleton lower-limb rehabilitation robot. The highest level is to calculate muscle-tendon net moment around joint based on muscle-model and skeleton rigid mechanical system, do a lower-limb recovery assessment, and finally select a proper rehabilitation exercise (passive, active-assistive, active or resistive exercise). By using the information of exercise type, the middle-level controller makes a decision to implement which type of controller (impedance or torque controller) that creates the torque command to feed low-level controller. The low-level controller is the realization of torque controller for PMSM (Permanent Magnet Synchronous Motor). The paper focuses on the design of active impedance control belonging to the middle-level control module. Active impedance control regulates the transfer of energy between the exoskeleton and the user, and its goal is to improve the dynamic response of the human limbs without sacrificing the user's control authority. The performance of the controller is demonstrated through simulation.