Design, control, and experimental verification of a soft knee exoskeleton for rehabilitation during walking

Abstract

Since the rigid constructions of the traditional exoskeletons are liable to increase inertia of the joint and limit wearer flexibility, the soft-type exoskeletons have been developed in recent years, which can reduce system inertia, increase interaction compliance, and ensure operation safety. In this article, we present the detailed design and preliminary control of a soft body-worn and tendon-sheath-driven exoskeleton that can apply appropriate torques to the biological knee joints during rehabilitation training. This article focuses on the design of compliance tendon-sheath actuation system based on Hill muscle model, which utilizes multi-wrap pulleys and Hill-based series elastic actuator to transmit effective forces. Besides, the overall control system and strategy architectures of knee soft exoskeleton are also proposed. A fuzzy proportional–integral–derivative controller is developed for the passive rehabilitation training. On this basis, a back-propagation-neural-network-based adaptive impedance control scheme is presented to provide adaptive force based on the disease condition of the patient. Finally, preliminary experiments are conducted to demonstrate the effectiveness of proposed exoskeleton and control strategies.