Four-Wheel Independent Steering Stability Control Based on VSR-ANMPC

Abstract

To address the problems of poor steering smoothness and handling stability for four-wheel independent steering (4WIS) vehicles, this paper presents an adaptive nonlinear model predictive control (ANMPC) strategy based on variable steering ratio (VSR). First, a two-degree-of-freedom (2-DOF) vehicle and reference model are established to provide a theoretical basis for controller design. Second, the Hermite interpolation polynomial is used to achieve a smooth transition design of the four-stage VSR. By optimizing the steering ratio curve, the steering smoothness and flexibility across the entire speed range are significantly improved. Furthermore, innovatively, the hyperbolic tangent function (tanh) is employed in combination with the μ-V adaptive weight optimization method to construct an adaptive weight adjustment mechanism for the ANMPC controller. To assess the efficacy of the control strategy, co-simulation experiments are performed using CarSim/Simulink. Simulation results demonstrate that versus conventional MPC, the developed algorithm achieves a 37.75% reduction in yaw rate dynamic response RMSE and a 4.61% decrease in lateral velocity RMSE during low-adhesion double lane-change maneuvers, significantly boosting handling stability and steering smoothness in 4WIS vehicles. The VSR-ANMPC control strategy enhances steering performance substantially while demonstrating exceptional handling stability control across diverse speed and adhesion conditions.