Title: Integrated control of active front steering and electric power steering system with EKF estimation of lateral force

Authors: Bing Zhou; Meng Xu; Lu Fan; Xiwen Yuan

Addresses: State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Faculty of Mechanical and Vehicle Engineering, Hunan University, Changsha, China ' State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Faculty of Mechanical and Vehicle Engineering, Hunan University, Changsha, China ' State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Faculty of Mechanical and Vehicle Engineering, Hunan University, Changsha, China ' State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Faculty of Mechanical and Vehicle Engineering, Hunan University, Changsha, China

Abstract: Good vehicle handling characteristics are essential to ensure traffic safety. In the integrated system of electric power steering (EPS) and active front steering (AFS), the steering wheel torque may change abruptly with the interference of active steering. The additional front road wheel angle generated by AFS gives rise to the change of tyre lateral force, which results in the change of steering wheel torque finally. Although the tyre forces are difficult to measure, the extended Kalman filter (EKF) algorithm can be used to estimate it. The problem of steering wheel torque change can be resolved by tyre forces estimate based on the EKF observer in nonlinear system. The vehicle nonlinear mathematical model is presented and a nonlinear tyre lateral force estimator is also established basing on EKF. The estimated tyre lateral forces can be applied to compensate the abrupt change of steering wheel torque, which realises the combination of vehicle states estimation and vehicle control. The simulation results in MATLAB/Simulink show the effectiveness of proposed control strategy.

Keywords: active front steering; AFS; electric power steering; EPS; integrated control; EKF observer; vehicle modelling; nonlinear models; mathematical modelling; tyre lateral force; vehicle handling; steering wheel torque; extended Kalman filter; vehicle state estimation; vehicle control; simulation.

DOI: 10.1504/IJVSMT.2015.070156

International Journal of Vehicle Systems Modelling and Testing, 2015 Vol.10 No.3, pp.224 - 238

Received: 17 May 2014
Accepted: 12 Dec 2014
Published online: 28 Jun 2015 *

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