Integrated Control Strategy of Active Front-Wheel Steering and Active Suspension Based on 3-D Piecewise Affine Tire Model

In order to realize the multiobjective cooperative optimization control of vehicle lateral stability, roll safety, and ride comfort, this article proposes an integrated control strategy of active front-wheel steering (AFS) system and active suspension system (ASS) based on a 3-D piecewise affine (PWA) tire model for distributed hub motor-driven electric vehicles. First, a 14 degrees of freedom (14-DOF) vehicle dynamics simulation model, accounting for the unbalanced electromagnetic force (EMF) of the hub motor, is established. Then, in order to improve the modeling accuracy of the lateral controller, the PWA method is used to establish a 3-D PWA tire model based on the lateral force, tire slip angle, and vertical load, and a mixed-logic dynamic (MLD) model is established to design an AFS controller based on hybrid model predictive control (hMPC). Additionally, an ASS controller based on dual-model predictive control (DMPC) is designed to address the influence of the EMF generated by the hub motor on the suspension system and tires. The coordination strategy of the AFS and the ASS based on the front wheel angle, beta - beta phase plane, and lateral load transfer rate (LTR) is established. The test results of the driver-in-the-loop simulation have verified the superiority of the control strategy proposed, which significantly improves the vehicle's active safety under high speed with low adhesion and high speed with large steering conditions.