Simulation study on the design and control of humanoid shoulder joint based on pneumatic artificial muscle drive.

This paper presents a simulation study of a three-degree-of-freedom (3-DoF) humanoid shoulder joint system driven by pneumatic artificial muscles (PAMs). A 6-PAM-based joint mechanism is designed to achieve compound motions, including flexion–extension, internal–external rotation, and abduction–adduction via a rotary antagonistic structure. The mechanical characteristics of the PAMs are identified using a particle swarm optimization (PSO) algorithm, and a nonlinear model incorporating hysteresis and coupling effects is established. To enhance control performance, a sliding mode controller (ASTSMC) based on a saturated sliding surface and adaptive super-twisting disturbance compensation is proposed. The global asymptotic stability of the closed-loop system is rigorously proven using Lyapunov theory. Simulation experiments are conducted in MATLAB under three scenarios: step response, sinusoidal tracking, and disturbance rejection. Results show that the proposed controller reduces the average steady-state error (SSE) to 0.00027 rad with a maximum overshoot of only 0.22% in the step response test. For sinusoidal tracking, the average root-mean-square error (RMSE) is 0.00020 rad. In the disturbance rejection test, the average SSE is suppressed to 0.00155 rad. These results verify the proposed controller's superior response speed, accuracy, and robustness under dynamic loading conditions. [ABSTRACT FROM AUTHOR]