Integrated Chassis Control With Four-Wheel Independent Steering Under Constraint on Front Slip Angles

Seongjin Yim

doi:10.1109/access.2021.3050722

Abstract

This paper presents a method to design an integrated chassis controller with four-wheel independent steering (4WIS) under the constraint on front slip angles for electric vehicles (EVs) adopting in-wheel motor (IWM) driving system. To improve lateral stability and maneuverability of a vehicle, direct yaw moment control strategy is adopted. A control allocation method is adopted to distribute control yaw moment into tire forces, generated by 4WIS. If corrective steering angles of 4WIS are added to front steering angles generated by a driver, it can deteriorate control performance because the lateral tire force of front wheels easily saturated and it causes loss of required yaw moment needed to stabilize a vehicle. To cope with the problem, it is necessary to impose constraints on front slip angles. To compensate the loss of control yaw moment caused by the constraint on front slip angles, a constrained control allocation method is presented. Simulation on driving simulation tool, CarSim <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> , shows that the proposed integrated chassis controller is capable of maintaining lateral stability and maneuverability without performance deterioration under the constraint on the front slip angles.

Highlights

INTRODUCTIONIn-wheel motors (IWMs) have been developed by researchers and automotive industry [1]
Over the last decade, in-wheel motors (IWMs) have been developed by researchers and automotive industry [1]
In view of vehicle stability control, IWM has a function of 4-wheel independent drive (4WID) and braking (4WIB), which consist of traction motor with reduction gear and electro-mechanical brake (EMB) or electronic wedge brake (EWB), respectively [4]

Summary

INTRODUCTION

In-wheel motors (IWMs) have been developed by researchers and automotive industry [1]. The slip angles generated by FWIS should be restricted to a certain value which gives the maximum lateral tire forces This causes the loss of the desired yaw moment, which results in the deterioration of control performance. The control yaw moment, calculated by the upper one, is realized by tire forces, generated by several single actuators or actuator combinations such as 4WIB, 4WID and 4WIS. To cope with the saturation of front lateral tire forces or physical constraint on front slip angles, CWPCA is applied [16], [22] This is the contribution of this paper, which is to propose the control allocation method with the multiple actuators, 4WIS, 4WIB and 4WID, under the constraint on front slip angles. A sliding mode observer, as given in [32], is adopted to estimate Fyf and Fyr because it is quite simple and can give good estimation results. β or vy is estimated by a signal-based extended Kalman filter (EKF), which does not need any models for state estimation, as proposed in the previous research [33]

DESIGN OF LOWER-LEVEL CONTROLLER

CONCLUSION