Nonsingular terminal sliding mode control with sliding perturbation observer for a permanent-magnet spherical actuator

In order to deal with the modeling of uncertainty and external environment disturbance in the trajectory tracking system of 3 degrees of freedom permanent-magnet spherical actuator, a nonsingular terminal sliding mode control method with sliding perturbation observer is proposed in this article. First, a sliding perturbation observer, which can estimate compound disturbance only by feedback position signals, is proposed to reduce the uncertainty caused by angular velocity observation. Then, based on the sliding perturbation observer, a nonsingular terminal sliding mode control method is designed to satisfy the requirements of system nonsingularity, robustness, and control accuracy. The stability of the controller is proved by the Lyapunov theory. Finally, simulation and experimental results show that the proposed control method has excellent anti-disturbance performance, which provides an important reference for the future applications of permanent-magnet spherical actuators in aerospace and other industrial fields.