Fluid-Driven Wearable Robots for Knee Rehabilitation

The knee joint is essential for activities of daily living, but age-related degeneration and diseases can impair its function and limit mobility. Conventional rigid exoskeletons can assist lower-limb motion, yet their poor compliance, limited comfort, and large mechanical burden reduce their suitability for wearable knee assistance, particularly for elderly users. This chapter presents SOROK, a soft robotic knee brace that integrates distributed soft origami actuators, a portable direct-drive hydraulic actuation system, and a multi-sensor feedback system. The proposed brace embeds series and parallel soft actuators into stretchable fabric to provide a compliant and practical human–robot interface. By using incompressible hydraulic actuation instead of pneumatic actuation, the system achieves improved response speed, enhanced control accuracy, and a compact portable design. The sensing system combines hydraulic pressure sensors, IMUs, and surface electromyography (sEMG) sensors to capture robot states, lower-limb kinematics, and user motion intention. A three-layer closed-loop control framework is further developed, consisting of an inner pressure loop, a kinematics-based motion loop, and an intention recognition loop based on sEMG signals. Experimental results demonstrate a response time of 422 ms for the hydraulic actuation system, and a sit-to-stand user study verifies the feasibility of the proposed system. These results indicate that SOROK provides a novel and portable soft robotic solution for knee assistance.