Title: Analysis and control for ideal variable transmission ratio characteristics of active front wheel steering

Authors: Xiaojun He; Kun Yang; Yile Chang; Chao Ma; Wei Wang; Jie Wang

Addresses: School of Transportation and Vehicle Engineering, Shandong University of Technology, Zibo, 255000, China ' School of Transportation and Vehicle Engineering, Shandong University of Technology, Zibo, 255000, China ' SAIC Motor R&D Innovation Headquarters, Shanghai, 201800, China ' School of Transportation and Vehicle Engineering, Shandong University of Technology, Zibo, 255000, China ' CATARC Automotive Test Center (Tianjin) Co., Ltd., Tianjin, 300300, China ' School of Transportation and Vehicle Engineering, Shandong University of Technology, Zibo, 255000, China

Abstract: The change law of ideal transmission ratio with vehicle speed and hand-wheel angle is studied based on constant gain of steady-state vehicle system. It is used to resolve the conflict between steering sensitivity at the low-speed segment and steering stability at the high-speed segment for the traditional vehicle. For preventing the sudden change of hand-wheel torque caused by the transmission ratio change, the ideal variable transmission ratio (VTR) law is fitted by the improved S-type function and optimised by particle swarm optimisation (PSO) algorithm. For improving driving stability of vehicle, the stability control strategy based on linear quadratic regulator (LQR) is studied based on the optimised ideal variable transmission ratio control law. The front wheel angle is decided by the vehicle stability control strategy, and then the active front wheel steering (AFS) motor angle is obtained by the AFS calculation module to realise the AFS control. The closed-loop driver-vehicle system is established. This system includes driver model, the vehicle dynamic model, AFS model and so on. The results indicate that the performance of the proposed controller is good in the front wheel steering angle control for the better tracking to desired vehicle state.

Keywords: ideal variable transmission ratio; improved S-type function; particle swarm optimisation algorithm; linear quadratic regulator; LQR; active front wheel steering; AFS.

DOI: 10.1504/IJMIC.2024.141679

International Journal of Modelling, Identification and Control, 2024 Vol.45 No.1, pp.40 - 57

Received: 22 Aug 2023
Accepted: 09 Feb 2024
Published online: 30 Sep 2024 *