A New Way of Controlling a Four Wheel Steering Vehicle

Ito, Ken; Fujishiro, Takeshi; Kawabe, Taketoshi; Kanai, Kimio; Ochi, Yoshimasa · 1987 · OpenAlex-citations

DOI: 10.9746/sicetr1965.23.828

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Summary

This paper addresses the challenge of improving vehicle maneuverability and stability through a new feedforward control method for four-wheel steering (4WS) vehicles. Motivated by the increasing demand for handling performance that exceeds the limits of conventional mechanical design, the authors propose a control system that ensures desired responses in yaw rate and lateral acceleration. The approach focuses on feedforward compensation to avoid interference with human driver inputs, particularly in nonlinear or limit regions where feedback control might cause instability. The study presents three distinct design methods for controlling rear wheel steering angles: model matching control for yaw rate, model following control for lateral acceleration, and a novel "D*" control method, which treats a linear combination of yaw rate and lateral acceleration as the output. The authors derived state equations for the vehicle's planar motion and designed feedforward compensators to make the vehicle's response match a predefined reference model. For the lateral acceleration and D* methods, optimal control gains were determined by minimizing a quadratic performance index, solving the associated Riccati equation. The effectiveness of these methods was verified through computer simulations using specific vehicle parameters (mass 1,225 kg, wheelbase 2.5 m) at speeds of 33.3 m/s and 50 m/s. Additionally, experimental validation was conducted on a modified 1.8-liter vehicle equipped with an electronically controlled rear steering mechanism. The results demonstrated that the proposed control systems significantly improved vehicle dynamics compared to conventional two-wheel steering (2WS). In simulations, the 4WS systems provided superior transient characteristics, with the D* method offering a balanced response between yaw rate and lateral acceleration. Proving ground tests confirmed these findings. In step response and lane change tests at 120 km/h, the controlled vehicle exhibited minimal overshoot and closely matched the reference model, whereas the uncontrolled vehicle showed significant oscillatory behavior. Furthermore, in free response tests (hands-off stability), the settling time of the yaw rate for the controlled vehicle was reduced by more than 50% (from 2.6 seconds to 1.1 seconds at 120 km/h), demonstrating enhanced high-speed stability. The significance of this work lies in confirming that feedforward model following control is a practical and effective strategy for 4WS systems. It allows for the independent tuning of transient and steady-state characteristics without altering mechanical components like steering gear ratios. The study concludes that this method successfully improves both maneuverability and stability, providing a robust framework for active vehicle control systems that can be integrated into future automotive designs.

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

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• steering pattern