Synchronized Angle Control for the Thumb and the Index Finger in an Anthropomorphic Hand Actuated by Pneumatic Muscles

To enhance tracking accuracy and robustness of an anthropomorphic hand actuated by pneumatic muscles, an synchronized angle control strategy for the thumb and the index finger is proposed in this article. The research addresses inverse kinematics problem and tackles challenge of joint coupling, which significantly improves control performance of the multijoint robotic fingers. A simulated annealing Newton–Raphson (SANR) method is employed to efficiently solve the inverse kinematics of the index finger. A nonlinear extended state observer (ESO) is designed to estimate the joint coupling in the thumb and the index finger. A global terminal sliding mode controller is developed to achieve precise synchronized angle control and improve overall control performance. Stability of the nonlinear ESO and the global terminal sliding mode controller is analyzed using Lyapunov methods. Experimental results demonstrate effectiveness of the synchronized angle control strategy in enhancing tracking precision and robustness of the anthropomorphic hand under joint coupling.