Upper-limb Power-Assisted Exoskeleton
An innovative wearable upper-limb power-assist exoskeleton system (UPES) was designed for la-borers to improve work efficiency and reduce the risk of musculoskeletal disorders. This novel wearable UPES consists of four joints, each comprising a single actuated pneumatic muscle actu-ator (PMA) and a torsion spring module driven via a steel cable. Unlike most single-joint applica-tions, where dual-PMAs are driven by antagonism, this design aims to combine a torsion spring module with a single-PMA via a steel cable for a 1-degree of freedom (1-DOF) joint controlled by a proportional-pressure regulator. The proposed four driving degrees of freedom wearable UPES is suitable for power assistance in work and characterizes a simple structure, safety, and compliance with the motion of an upper limb. However, due to the hysteresis, time-varying characteristics of the PMA, and non-linear movement between joint flexion and extension, the model parameters are difficult to identify accurately, resulting in unmeasurable uncertainties and disturbances of the wearable UPES. To address this issue, we propose an improved proxy-based sliding mode con-troller integrated with a linear extended state observer (IPSMC-LESO) to achieve accurate pow-er-assisted control for the upper limb and ensure safe interaction between the UPES and the wearer. This control method can slow the underdamped dynamic recovery motion to tend the target trajectory without overshoots from large tracking errors that result in actuator saturation, and without deteriorating the power assist effect during regular operation. The experimental re-sults show that IPSMC-LESO can effectively control a 4-DOF wearable UPES, observe the un-known states and total disturbance online of the system, and adapt to the external environment and load changes to improve system control performance. The results prove that the joint torsion spring module combining the single-PMA can reduce the number of PMAs and proportion-al-pressure regulators by half and obtain a control response similar to that of the dual-PMA structure.
美國發明專利: US 10,420,695 B2
中國發明專利: ZL 2017 1 0240416.4
Wearable Waist-Assistive Exoskeleton
To improve the high rigidity, heaviness, and lack of flexibility of electric motors. This study aims to combine pneumatic muscle actuators with the waist-assistive exoskeleton and propose an overall design scheme of the flexible waist-assistive exoskeleton system with the variable-assist modes. And carry out the system safety controller design to reduce the burden of loin caused by repeated and frequent lifting. This study proposes a Novel Proxy-Based Sliding Mode Controller (NPSMC) based on the Linear Extended State Observer (LESO) and analyzes the system's stability by the Lyapunov theory. To ensure that when a significant error occurs in an unexpected situation, the system can use an over-damped compliant dynamic recovery method to reduce the impact force experienced by the wearer. In the design part of the variable-assist mode, this study provides four different assist modes through the surface EMG signals of different gestures according to the wearer’s needs. In the part of system production and experiment, this research not only completes the system development based on the overall design scheme proposed but also conducts related investigations from the perspective of system safety and the evaluation of the auxiliary effect of the surface EMG signal. The experimental results show that the flexible waist-assistive exoskeleton system can effectively reduce the burden of the loin. Under the compensation of NPSMC, the system can simultaneously meet tracking accuracy and safety control requirements.