Pneumatic Soft Actuation in Elbow Rehabilitation Devices: Actuator Architectures, Sensing Modalities, and Control Strategies—Scoping Review

Abstract

Soft and compliant rehabilitation devices may provide improved anatomical adaptability, reduced distal mass, and more flexible human–robot interaction compared with conventional rigid exoskeletons. This scoping review examines elbow rehabilitation technologies across three interconnected domains: (1) the broader landscape of soft and compliant actuation, (2) the structural, material, and operating architectures of pneumatic soft actuators, and (3) the sensing, intention-detection, and closed-loop control methods used in pneumatic systems. The review included 109 peer-reviewed reports. Four main actuation families were identified: pneumatic soft actuators, motor-driven cable and tendon systems, series-elastic or variable-stiffness actuators, and shape-memory-alloy-based devices. Pneumatic architectures were primarily organized around linear artificial muscles and chamber-based bending or rotary actuators, complemented by rigid–soft integrated, cable-transmitted, modular, antagonistic, self-sensing, and variable-stiffness configurations. Feedback most relied on pressure, kinematic, force, and electromyographic signals. Control architectures combined position, force, torque, impedance, and pressure regulation, while nonlinearities and uncertainties were addressed using model-based, adaptive, sliding-mode, fuzzy, neural, and hybrid methods.