Predefined-Time Tracking Control for Robotic Manipulators With Input Saturation Based on Disturbance Observer

This paper investigates predefined-time tracking control with prescribed performance function for robotic manipulators subject to lumped disturbances and actuator saturation. A prescribed performance error transformation is first employed to enforce prescribed performance tracking error bounds through time-varying performance functions. To rapidly compensate uncertainties, a disturbance observer is constructed to estimate an unknown lumped term within a user-assigned time. Based on the transformed error, a predefined-time sliding-mode controller is then developed to drive the transformed tracking error to the origin within a predefined time, while an auxiliary dynamic compensator is introduced to address the input saturation problem. Lyapunov stability analysis establishes boundedness of all closed-loop signals and predefined-time convergence. Simulations on a robotic manipulator demonstrate that tracking errors remain inside the prescribed performance bounds and that the lumped disturbance term is accurately estimated and effectively compensated in the closed-loop system.