A Fuzzy Control Method to Improve Vehicle Yaw Stability Based on Integrated Yaw Moment Control and Active Front Steering

Abstract

In this paper, a fuzzy control method is proposed to improve vehicle yaw stability by integrated yaw moment control and active front steering. This control system is designed by actively controlling the front steering angle and the distribution of braking forces, using feed-forward regulation and feedback revision control strategy, and a fuzzy controller is designed to suppress the output error of yaw rate and side slip angle, which can keep the vehicle to follow the desired trajectories. A simulation based on this control method is performed with a vehicle at two different running conditions, and the simulation results by other different control methods are compared also. The results showed that the presented method can effectively control the yaw rate and side slip angle synchronously, the transient and steady response of vehicle is good, the vehicle yaw stability is improved.Index Terms -Vehicle, Yaw moment, Active front steering, Yaw Stability, Fuzzy control ʳ ĉ. INTRODUCTIONThe handling and stability of vehicle is an important performance, which influencing the safety of the vehicle at high speed. The vehicle yaw stability control system is a complex non-linear problem, which is influenced by such as vehicle's initial running state, road adhesion coefficients, and front wheel steering angle and at el in [1]. At present, there are many kinds of control strategy for improving vehicle yaw stability, for example, the logic threshold control, PID control, sliding-mode theory, and fuzzy control. However, vehicle yaw stability counts a large number of uncertain nonlinear characteristics; it is very difficult to derive a relative simple controller based on traditional methods for such a complex system. The fuzzy system has the potential to concertedly incorporate different concepts of yaw control referred above in a relative simple manner. Direct yaw moment control (DYC) is regarded as one of promising chassis technologies, has been studied by controlling brakes independently and adjusting yaw moment on vehicles directly in [2] and [3]. But DYC decreases steady-state value of yaw rate at a high speed and adds the burden of the driver in cornering in [4], and the active front steering (AFS) can counterbalance this trend in [5]. So DYC combined with AFS control can further improve vehicle handling and stability in [6].A fuzzy control method is proposed to improve vehicle yaw stability by the integrated yaw moment control and AFS.This control system is designed to take the steering angle and vehicle's speed as input variable, yaw rate and side slip angle as the feedback input variable, using feed-forward regulation and fuzzy feedback correction control strategy. Computer simulations are performed with cornering maneuver and double lane change maneuver separately at the high speed, and the results showed that, the presented method can effectively controls side slip angle and yaw rate of vehicle simultaneously and achieves multi-objective control of side slip angle and yaw rate of vehicle, and the vehicle yaw stability I...

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