Nonlinear composite observer-based predefined-time nonsingular terminal sliding mode fault tolerant control for distributed drive electric vehicles with unknown disturbances

Abstract This paper proposes a novel predefined-time nonsingular terminal sliding mode control scheme based on a nonlinear composite observer for distributed drive electric vehicles subject to in-wheel motor fault and unknown disturbances. Firstly, a composite observer is designed using linear matrix inequalities and Lyapunov functions to achieve simultaneous estimation of the system states, disturbances and fault factors. Then, utilizing the estimation information, a novel nonsingular terminal sliding mode controller is developed, which guarantees convergence of system states within a predefined time, and theoretical stability proof is provided. In contrast to the complex and restrictive sliding surface design that relies on the predefined-time lemmas and the piecewise control laws, the proposed fault tolerant controller adopts a unique construction form to enhance control signal smoothness, reduce chattering-induced damage, and ensure rapid post-fault response. Finally, simulations are conducted using MATLAB/Simulink and CarSim under representative loss of effectiveness scenarios involving one in-wheel motor and two in-wheel motors on the same side, thereby providing a progressive evaluation of the proposed method under different levels of driving force asymmetry.