Research on automobile four-wheel steering control system based on yaw angular velocity and centroid cornering angle

Yifeng Zhang,Biao Zhao,Canlong Zhang,Zhiwen Wang,Yuhang Wang

doi:10.1177/00202940211035404

Abstract

In order to improve the handling stability of four-wheel steering (4WS) cars, a two-degree-of-freedom 4WS vehicle dynamics model is constructed here, and the motion differential equation of the system model is established. Based on the quadratic optimal control theory, the optimal control of 4WS system is proposed in this paper. When running at low speed and high speed, through yaw rate feedback control, state feedback control, and optimal control, the 4WS cars are controlled based on yaw rate and centroid cornering angle with MATLAB/Simulink simulation. The result indicates that 4WS control based on the optimal control can improve the displacement of the cars. And, the optimal control of 4WS proposed in this paper can eliminate centroid cornering angle completely compared with other two traditional optimal control methods. Besides, the optimal control enjoys faster response speed and no overshoot happens. In conclusion, the optimal control method proposed in the paper represents better stability, moving track and stability, thereby further enhancing the handling property of cars.

Highlights

The steering of four-wheel steering (4WS, four-wheel steering) cars is completed by both front wheels and rear wheels
The function of 4WS can make the front and rear wheel turn in the opposite directions when driving at low speed and can make the front and rear wheel turn in the same directions when driving at high speed to reduce sideslip and tail slide
Control technology is applied to low-speed steering, the front and rear wheels are turned in different phases, which can reduce the minimum radius of the car when turning, supplying higher maneuverability for vehicle; when turning at high speeds, the front and rear wheels work in the same phrase, which can reduce the car’s center of mass side slip angle, reduce the difference between the car’s yaw rate and lateral acceleration, and increase the tire lateral force allowance, avoiding saturation and improving the car’s antiskid ability significantly

Summary

Introduction

The steering of four-wheel steering (4WS, four-wheel steering) cars is completed by both front wheels and rear wheels. The steering stability of the vehicle at high speed and the maneuver flexibility at low speed state can be improved effectively by adjusting the front and rear wheel rotation angle to control the vehicle centroid side deflection and yaw velocity. Formula (9), in simple form, contains the most important parameters, such as the complete vehicle quality M, the cornering stiffness Cr of the tire, the yaw moment of inertia around the center of mass, and the centroid positions Lf and Lr, which can reflect the most basic characteristic parameters of the steering effect of the 4WS car. Let the state space of the original system be represented by expressions (19) and (20)

Cf þ Cr

À Crð1 À KcÞ

Conclusion