title: Double closed-loop cascade control for lower limb exoskeleton with elastic actuation.
abstract: Unlike traditional rigid actuators, the significant features of Series Elastic Actuator (SEA) are stable torque control, lower output impedance, impact resistance and energy storage. Recently, SEA has been applied in many exoskeletons. In such applications, a key issue is how to realize the human-exoskeleton movement coordination. In this paper, double closed-loop cascade control for lower limb exoskeleton with SEA is proposed. This control method consists of inner SEA torque loop and outer contact force loop. Utilizing the SEA torque control with a motor velocity loop, actuation performances of SEA are analyzed. An integrated exoskeleton control system is designed, in which joint angles are calculated by internal encoders and resolvers and contact forces are gathered by external pressure sensors. The double closed-loop cascade control model is established based on the feedback signals of internal and external sensor. Movement experiments are accomplished in our prototype of lower limb exoskeleton. Preliminary results indicate the exoskeleton movements with pilot can be realized stably by utilizing this double closed-loop cascade control method. Feasibility of the SEA in our exoskeleton robot and effectiveness of the control method are verified.
authors.forename: Yanhe
authors.initials: Y
authors.lastname: Zhu
authors.forename: Tianjiao
authors.initials: T
authors.lastname: Zheng
authors.forename: Hongzhe
authors.initials: H
authors.lastname: Jin
authors.forename: Jixing
authors.initials: J
authors.lastname: Yang
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
mesh_terms: D004867:Equipment Design; D006801:Humans; D035002:Lower Extremity / Q000293:injuries* / Q000502:physiology*; D008962:Models, Theoretical; D009068:Movement / Q000502:physiology*; D009989:Orthotic Devices; D012046:Rehabilitation / Q000295:instrumentation*; D012371:Robotics / Q000295:instrumentation*; D019415:Torque; D014947:Wounds and Injuries / Q000534:rehabilitation*
keywords: Exoskeleton; Series Elastic Actuator (SEA); cascade control; torque control