Fixed-time sliding mode trajectory tracking control for uncertain robotic manipulators using high-order extended state observer

This paper investigates the fixed-time trajectory tracking problem for uncertain robotic manipulators with internal uncertainties, external disturbances, and actuator faults. A high-order fixed-time extended state observer is designed to observe lumped uncertainties, its convergence time is only determined by the designed parameters. In addition, a fixed-time stable system is established to speed the convergence of system states underlying the existing fixed-time theory, and a non-singular fast terminal sliding mode surface is developed by depending on this system. Based on the designed observer and sliding mode surface, a fast fixed-time sliding mode controller is designed to guarantee global fixed-time convergence of the tracking error. Finally, the effectiveness and superiority of the proposed method are demonstrated by two-link robotic manipulator.