Sliding mode control using the disturbance observer for uncertain robot manipulators with prescribed performance

Robot manipulators play a critical role in manufacturing and the most existing studies cannot ensure the precise trajectory tracking with less error, overshoot and convergence time. In this regard, this paper proposes a sliding mode control method for robot manipulators with model uncertainties and external disturbances, guaranteeing transient performance and predefined time stability. Firstly, a new Lyapunov criterion is derived to analyze predefined time stability of nonlinear systems. Secondly, a predefined time function is introduced to determine the convergence time, convergence accuracy and maximum overshoot. Then in order to accurately estimate lumped disturbance without prior knowledge, a predefined time disturbance observer (PTDO) is designed for predefined time trajectory tracking control of robot manipulators. Subsequently, a sliding mode controller is developed, incorporating the PTDO’s estimation. Compared with existing finite time and fixed time controllers, the novelty of the proposed control scheme is that all system components achieve predefined time stability, with convergence time adjustable through a design parameter, regardless of initial conditions. Finally, simulation results are presented to demonstrate the effectiveness and improved performance of the proposed method.