Low Cost Lower Limb Exoskeleton for Assisting Gait Rehabilitation: Design and Evaluation

This paper presents the design and implementation of a low cost, yet robust, three degrees of freedom (DoF) lower limb exoskeleton intended to assist patients in gait rehabilitation. The majority of patients with incomplete spinal cord injuries (SCI) are able to walk after a rehabilitation process. Among the broad options of physical rehabilitation therapies, there is a relatively recent interest in those assisted by robotic exoskeletons, due to features as high precision movements and automated repetitions. In this context, the subsystems of the exoskeleton prototype described throughout this paper are the following: i) a controlled area network (CAN) communications bus with SDO protocol; and, ii) a hierarchical control system consisting of two levels: a trajectory generator of the walk biomechanics implemented in a centralized controller (CC), and distributed controllers (DC) installed at each joint of the exoskeleton. The multiplication mechanical system uses reduction speed boxes based on cycloidal and planetary gears. Experimental results of the prototype operating, with and without carrying weight, show effectiveness of the whole control system for tracking a non-pathological gait biomechanics trajectory.