Rear Steer Actuator-Less Four-Wheel Steering System for Four-Wheel Driving Electric Vehicles

摘要

Four-wheel steering (4WS) vehicles have superior charactristics in motion performance to two wheel ones by controlling the yaw motion and the sideslip angle. Previous research revealed that electric vehicles (EVs) driven by in-wheel motors (IWMs) can steer without steering actuators (electric power steering, EPS) by utilizing their appropriate alignment, the difference of right and left driving forces and self-aligning torques. In this paper, the system to apply the rear EPS-less steering method to 4WS EVs is proposed and 2 ways to realize it are discussed. The one uses the estimation of lateral force, and the other uses a lateral force sensor to measure the precise value and enhance the robustness against the modeling error of the vehicle mass. The effectiveness of the methods are demonstrated by simulations and experiments in the situations of avoiding collisions and changing lanes with a 4WS and four-wheel driving IWMs-EV without a rear EPS.