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Active Disturbance Rejection Control for a Fluid-Driven Hand Rehabilitation Device

This article proposes a new hand rehabilitation device to help therapists repetitively perform hand group stretching training for poststroke patients. The actuator of the proposed device is made of elastomeric materials, driven by fluid pressure, and put onto the surface of a glove. Compared to the traditional rigid exoskeletons for hand rehabilitation, the proposed device is soft, lightweight, and low cost. Because the exact and explicit model is hard to be built for the proposed device and the unconscious tremors occurred during hand rehabilitation, the active disturbance rejection control (ADRC) algorithm, based on the extended state observer (ESO), is adopted to achieve the control purpose. This article analyzes the transient and steady-state performances of the controller based on some reasonable assumptions, and shows its better disturbance rejection ability compared to the widely used proportional-integral-differential control method. In addition, the ADRC algorithm with the reduced-order extended state observer (RESO) has been studied as well. The parameters of the RESO can be obtained by the parameters of the previously determined ESO instead of the trial and error approach, which can ensure the control performance of the ADRC with the RESO does not degrade. Finally, clinical tests have been conducted to verify the functional correctness of the proposed device, and these theoretical results have also been verified by experiments and comparisons.