An improved fixed-time fault-tolerant tracking control with disturbances and actuator faults: application to 3-DOF robotic manipulator

This paper proposes an improved fixed-time fault-tolerant tracking control scheme for uncertain systems subject to disturbances and actuator effectiveness faults. An adaptive mechanism is employed to compensate parameter uncertainties and external disturbances, whereas an equivalent reformulation of the system dynamics is developed to mitigate actuator effectiveness faults. The closed-loop stability is analysed with a Lyapunov approach, and fixed-time convergence of the tracking error is guaranteed. Compared with existing methods, the proposed scheme avoids overestimated control gains and does not rely on prior knowledge of system parameters. The general design is first established for an n-degree-of-freedom system, and then applied to a 3-DOF robotic manipulator as an illustrative example. Simulation results verify that the controller achieves accurate trajectory tracking, strong robustness, and reliable fault tolerance under disturbances and actuator faults.