Coupled Analysis Of The Stability Of The Car In Crosswind Condition By The Combination Of Vehicle Aerodynamics And System Dynamics

By the end of 2015,the total mileage of china’s highway ranks world first,up to123000 Km. Because of the vast territory, the topographic features in china are very different, the nature wind environment of many places may be very poor. As the development of highway,the frequency for people to encounter dangerous crosswind is becoming more and more high. There are many traffic accidents caused by crosswind, which often exert influence on the stability of the car. So,the research aimed at the stability of car in crosswind is meaningful.Many traditional researches about the stability of the car in crosswind are off-line research: When discussing the aerodynamics of a car, we set it as a geometry model,then load these forces and moments as the inputs of the system dynamic model to compute the stability of the car(one way couple). But the aerodynamics and motion state of a car in crosswind are often closely related,time depended and react on each other:the real car has both performance of geometry and dynamics. The change of the aerodynamic force of a car often cause the change of its motion state, and vice the verse. So coupled analysis of the aerodynamics and system dynamics of a car has some significant mean.Driving safety is the result of combination of driver,car,road,environment,and traffic management. America has completed some investigation concerned about traffic accidents, they found that: When car running under some complicate and dangerous conditions, 88% of all these accidents are caused by unsafe actions,12%are caused by unsafe conditions, such as gust,rainy and snowy climate. Driver plays an significant role in driving safety. When confront with gust, whether the driver can react appropriately directly affect the safety of the car. But because of the physiological factors, the reactions of the driver are usually limited at some level.When confront with gust, what can we do to help the driver to control the car has some practical mean.In order to solve the problems above, the main research contents are as follows:(1) Complete the wind tunnel test of a 1:4 scaled car model. Use different turbulence model and different crosswind simulation method to compute the aerodynamics of the scaled model to find a proper simulation method.(2) Complete the simulation of the stationary aerodynamics of the 1:1 full scale car, to discuss the influence exerted by wind velocity magnitude,deflection factors.(3) Use the distribution of the maximum wind to set down the magnitude of the wind of four gust model. Complete the research of the transient aerodynamics and stability of the car in crosswind condition by traditional one-way coupling method,which based on two freedom method.(4) Set the standards of the stability of car in crosswind condition.Build the two freedom and five freedom system dynamic model of the car, build the driver model and magic tire model.(5) Briefly introduce the coupling method of aerodynamics and system dynamics of the car.Respectively build two freedom and five freedom two-way coupling model based on the combination of Fluent and Matlab software.Compared the results of one-way and two-way coupling method based on the two freedom model with no-driver reaction.Complete the simulation of car in dangerous crosswind condition by two-way coupling method respectively based on two-freedom and five freedom model.(6) Analyze the factors which affect the safety of car in crosswind.Proposed an AFS method to control the safety of the car in crosswind.