Robust Fixed‐Time Sliding Mode With Prescribed Performance Control for Heavy‐Haul Freight Trains Under Actuator Saturation and Input Time Delay

This paper proposes a robust fixed‐time sliding mode controller with a prescribed performance function (RFTSM‐PPC) for heavy haul freight trains (HhFT) employing multiple electric locomotives. First, a fixed‐time extended state observer (FxTESO) is designed to estimate the velocities of the locomotives and the lumped disturbance component, which represents model uncertainties, external disturbances, as well as malfunctions in the actuators, including actuator faults, input saturation, and input time delay. Then, a prescribed performance function (PPF) is constructed to ensure that the tracking error is confined within predefined bounds. Based on the outputs of the FxTESO and PPF, a fixed‐time sliding mode controller is developed, incorporating a transition function to eliminate singularities and an auxiliary control component to compensate for the estimation error from the FxTESO. Finally, the particle swarm optimization algorithm (PSO) is employed to optimize the system parameters to enhance control performance. The theoretical analyses demonstrate that, with the proposed control system, the tracking errors of the HhFT are confined within a defined range and will converge to a bounded region within a fixed time. The simulation results show the effectiveness and superior performance of the proposed control method in ensuring accurate tracking and strong robustness under various operating conditions.