Design of Lateral and Longitudinal Controller for Four Wheel Steering Vehicles Considering Lateral Stability

To improve the tracking accuracy and lateral stability of vehicles, a longitudinal and lateral integrated tracking controller considering lateral stability was designed based on the maneuverability characteristics of four-wheel steering vehicles. The reference speed provided by the upper layer was used to impose safety speed constraints considering road curvature and lateral acceleration constraints, resulting in a smooth safety speed curve. Combining lateral tracking with speed tracking, a comprehensive control module for longitudinal and lateral integrated tracking based on a model predictive control algorithm was built. With the reference path and safety speed as targets, the front and rear wheel steering angles and longitudinal desired acceleration were solved under simultaneous longitudinal and lateral constraints. A longitudinal lower control module was designed based on the inverse longitudinal dynamics model of the vehicle, while considering the load transfer effect of the vehicle, and the motor torque and wheel braking torque based on the longitudinal desired acceleration were calculated. CarSim and MATLAB/Simulink platforms were used for joint simulation experiments of dual line shifting conditions, and comparing real-time performance with independent controllers in both horizontal and vertical directions, to verify the tracking accuracy and lateral stability of the designed controller. The results show that the tracking effect of the designed controller is optimal, with a peak lateral tracking error of 0.038 4 m, a peak yaw angle error of 0.27°, a peak velocity tracking error of 0.097 3 km/h, a lateral acceleration of the vehicle not exceeding 0.4g, and a combined acceleration within the attached ellipse, meeting the requirements of accuracy and stability.Meanwhile, the iteration time of the integrated controller is reduced by 29.1% compared to the independent controllers, which can improve the real-time performance of vehicle control.