Force Tracking Control of an Integrated Wheel-End Module Under In-Wheel Motor Air-Gap Eccentricity: An Interval Type-II Fuzzy Logic Approach

The integrated wheel-end module incorporates both driving and steering functions at the wheel end, enabling independent control of each wheel and significantly enhancing the vehicle's agility and stability. However, during steering maneuvers, road excitations and variations in wheel motion may lead to air-gap eccentricity (AGE) in the in-wheel motor, resulting in the unbalanced radial force and torque (URF/URT). These disturbances degrade the tracking accuracy of the wheel-end module and subsequently impair the vehicle's steering performance. To address this issue, a control-oriented model of the integrated wheel-end module is developed, incorporating the coupled characteristics of longitudinal slip and lateral slip angle of the tire. Furthermore, an interval type-II fuzzy logic driven self-tuning tube model predictive control (IT2FL-STMPC) strategy is proposed. First, the generation mechanism of URF/URT under AGE is analyzed in depth. To mitigate the adverse effects of these uncertain disturbances on the wheel-end dynamics, an online observation method based on interval type-II fuzzy logic systems is designed to enable real-time estimation of URF/URT and its perturbation bounds. On this basis, a self-tuning tube model predictive controller is developed to dynamically adjust the Tube boundaries according to the real-time observed disturbance range, effectively reducing control conservatism and improving tracking accuracy. Hardware-in-the-loop simulations and real-vehicle experiments validate that the proposed method can effectively suppress the adverse effects caused by AGE and significantly enhance the tracking control performance of the integrated wheel-end system.