Design of a Compliant Upper-Limb Rehabilitation Exoskeleton based on Novel Series Elastic Actuators

This paper proposes an Upper-Limb Exoskeleton actuated by a novel Series Elastic Actuator (SEA) for the purpose of rehabilitation training. In design, the exoskeleton features 7 Degrees of Freedom (DOFs), 4 of which are actuated by SEAs, so as to cover most of the human motion trajectories at the time of rehabilitation training. The elastic component of SEA includes the tension springs intended for circumferential arrangement. Showing a linear torque-deformation characteristic within its working range, the elastic component retains consistent rotary stiffness in both directions. In order to evaluate the dynamic performance of the exoskeleton, the experiment of a single joint force and position control is conducted in this exoskeleton. The result of the compliant joint's bandwidth reaches 6.1 Hz in force control and the tracking error is 0.3 Nm with a sinusoidal input torque with an amplitude of 3 Nm and a frequency of 1.5 Hz. Our result demonstrates an accurate force control and position regulation behavior that meets the requirement placed on rehabilitation training.