The Research On Stability Control Of High Speed Vehicle Under Crosswind Based On Active4WS System

With the rapid development of vehicle industry and building highways on a large scale, along with these growth is the speed of vehicles. The adverse effects of crosswind on handling stability of the high speed vehicle arouse people’s concern and attention. Existing vehicles’correction mainly depend on the drivers’manipulation of the steering wheel, when the vehicle steering motion and attitude is influenced under crosswind. This may brought drivers with enormous psychological pressure, workload and even traffic accidents due to the uncertainty of crosswind which caused serious threat to the safety of vehicle driving. Thus, this paper abandons traditional ideas that optimize boby shape and structure parameters, and it bases on the research of crosswind response characteristics of high speed vehicle, applying the active control technology of active Four Wheel Steering (4WS), and cooperating with the preview-follow optimal curvature driver model to improve the crosswind stability of the vehicle.Establishing a dynamic model of high speed vehicle under the effect of crosswind is the basis research on crosswind stability of vehicle. Therefore, this research established the nonlinear tire model based on the "magic formula", and on the basis of the established model, nonlinear three freedom whole vehicle model is established which may able to reflect the moving attitude of the vehicle with the influence of crosswind and take this model as the platform for the controlling research on high speed vehicle’s crosswind stability.This paper put forward a novel control strategy of high speed vehicle’s crosswind stability based on active4WS system, the whole sliding mode control theory is applied to design active4WS system controller, and through the control of front and back tires’ angle at the same time, moving states of4WS vehicle under the effect of crosswind motion is guaranteed to follow the ideal vehicle model, the well robustness of the crosswind’s uncertain interference is realized; the numerical simulation analysis is carried on as well, the simulation results showed that the active4WS vehicle running on a wide variety of typical working conditions and suffering disturbance of all kinds of crosswinds, the dynamic response characteristics of crosswind can well follow the ideal motion state, the crosswind stability of vehicle is improved, verifying the correctness and effectiveness of the whole sliding mode controller of active4WS system designed in this research.Finally, this research established the optimal curvature driver model which aimed at keeping travel route, and vehicle’s crosswind stability under the closed-loop system of "driver-active4WS vehicle" is researched; Numerical simulation analyses indicated that active4WS vehicle can well control side slip angle and yaw rate under both the open-loop control and closed-loop control, but the closed-loop control has a better keeping ability of the travel route, and fundamentally improved the maneuverability and stability of the vehicle, also verified the effectiveness of the closed-loop control system.