Design, Development, and Control of a Novel Upper-Limb Power-Assist Exoskeleton System Driven by Pneumatic Muscle Actuators

An innovative wearable upper-limb power-assist exoskeleton system (UPES) was designed for laborers to improve work efficiency and reduce the risk of musculoskeletal disorders. This novel UPES consists four joints, each comprising a single actuated pneumatic muscle actuator (PMA) torsion spring module driven via steel cable. Unlike most single-joint applications, where dual-PMAs are by antagonism, this design aims combine with single-PMA cable 1-degree freedom (1-DOF) joint controlled proportional-pressure regulator. The proposed driving degrees is suitable power assistance in characterizes simple structure, safety, compliance motion an upper limb. However, due hysteresis, time-varying characteristics PMA, non-linear movement between flexion extension, model parameters difficult identify accurately, resulting unmeasurable uncertainties disturbances UPES. To address issue, we propose improved proxy-based sliding mode controller integrated linear extended state observer (IPSMC-LESO) achieve accurate power-assisted control limb ensure safe interaction wearer. method can slow underdamped dynamic recovery tend target trajectory without overshoots from large tracking errors that result saturation, deteriorating assist effect during regular operation. experimental results show IPSMC-LESO effectively 4-DOF UPES, observe unknown states total disturbance online system, adapt external environment load changes performance. prove combining number PMAs regulators half obtain response similar dual-PMA structure.