Angle tracking control for double-joint dexterous hand systems based on a piecewise extended state observer

In this paper, an angle tracking control method is introduced for a double-joint dexterous hand system. The double-joint dexterous hand system is driven by pneumatic artificial muscles. A piecewise extended state observer is proposed to estimate disturbance and uncertainty. In addition, a proportional–derivative controller by incorporating the disturbance estimates is proposed to improve angle tracking precision and disturbance rejection abilities. The convergence of the piecewise extended state observer is analyzed and the stability conditions are presented. Finally, simulation and experimental results show that better estimation performances are obtained by the piecewise extended state observer than a linear extended state observer or a nonlinear extended state observer, and the angle tracking precision and disturbance rejection abilities are improved by applying the proposed method.