Design and Control of an Elbow Rehabilitation Robot Driven by a Variable Stiffness Actuator

Adjustable joint compliance is essential for ensuring safe and natural human-robot interaction in rehabilitation scenarios. This paper presents an elbow rehabilitation robot driven by a dual-motor load sharing variable stiffness actuator and coordinated via a hierarchical control framework. The mechanical design integrates a power transmission mechanism with a variable stiffness mechanism, enabling task-adaptive compliance without increasing sensor complexity. At the control level, a highlevel control layer generates assistive joint torques based on taskspace impedance, while a low-level control layer translates torque commands into precise deflection angle for robust execution. Experimental evaluations, including bench tests and human-robot interaction trials, validate the system's capabilities in accurate torque rendering, high transparency under low stiffness, strong assistance under high stiffness, and safe, comfortable interaction across diverse rehabilitation tasks.