Rear-Wheel Steering Control for Enhanced Steady-State and Transient Vehicle Handling Characteristics

Kwanwoo Park,Kyongsu Yi,Eunhyek Joa,Youngsik Yoon

doi:10.1109/access.2020.3014719

Abstract

This paper presents a rear-wheel steering (RWS) control algorithm to enhance the vehicle handling performance without prior knowledge of tire characteristics. A RWS system is a chassis control module that can effectively improve vehicle maneuverability and stability. Since the tire-road friction coefficient is difficult to obtain in real world application, the proposed RWS control algorithm is designed so that it can be implemented without any tire-road information. The proposed RWS control algorithm consists of steady-state and transient control inputs. The steady-state control input is proportional to the driver's steering input for achieving the desired yaw rate gain. The desired yaw rate gain is obtained through an offline optimization that is aimed to minimize the vehicle lateral velocity. The transient control input consists of feedforward and feedback control inputs. The feedforward input is designed to improve transient responses of the yaw rate. Computer simulation studies have shown that a trade-off relationship between overshoot and response time exists when the RWS control input is a sum of the steady-state and feedforward inputs. To compromise this conflict, a feedback input has been designed. The overshoot can be significantly reduced while the response time is slightly changed via the feedback input. The proposed algorithm has been investigated via computer simulations. The simulation has been conducted for step steer and sine with dwell scenarios under various road friction conditions. The performance of a RWS vehicle was evaluated using objective indices. Simulation results show that the proposed algorithm enhances vehicle handling performance.

Highlights

Rear-wheel steering (RWS) control has been developed for decades with the aim of improving vehicle handling performance and stability
The purposes of rear-wheel steering (RWS) control broadly fall into two categories: 1) minimize vehicle side slip angle, and 2) track the desired yaw rate
4) This paper proposes a transient control input without any tire and road friction information based on the proposed lateral dynamic model

Summary

INTRODUCTION

Rear-wheel steering (RWS) control has been developed for decades with the aim of improving vehicle handling performance and stability. The main contributions of the proposed RWS control design framework are as follows: 1) The proposed control algorithm improves vehicle handling performance using measurable sensor signals (such as yaw rate, lateral acceleration, and steering wheel angle) without any information on tire and road surface. Since this difference denotes the first-time derivative of the side slip angle, we conclude that this term is the cause of this unnatural lateral jerk To improve this issue, previous studies [14]–[16] added a 1st-order delay term to the rear wheel steering control algorithm. The proposed RWS control algorithm consists of the steady-state input, the feedforward of transient input (w.r.t. delay of the yaw rate) and the feedback of transient input (w.r.t. the first-time derivative of the side slip angle). The most notable point is that the proposed control algorithm only uses vehicle specifications and measurable vehicle signals instead of the tire cornering stiffness in the vehicle dynamics

REAR-WHEEL STEERING CONTROL FOR ENHANCED STEADY-STATE HANDLING

SIMULATION RESULTS

Findings

CONCLUSION