Research On Vehicle Stability And Control Under Unsteady Crosswind

Due to the existence of natural wind,cars are inevitably affected by crosswinds when driving on actual roads,especially when the cars are driving on open roads,tunnels,etc.,they are easily affected by crosswinds,and the car speed the faster the potential safety hazards caused by crosswinds are,the greater.According to statistics,nearly 23% of traffic accidents on highways are caused by crosswinds each year.However,in the past,domestic and foreign scholars’ research on automobile aerodynamics has mainly focused on longitudinal wind.In order to reduce wind resistance and improve fuel economy,a small number of studies on crosswind also use stable wind,which is not universal.In this paper,based on the two kinds of unsteady winds that are common in real situations,the cross-wind stability of automobiles is studied,and the coordinated control strategy of AFS and DYC is used,which is of great significance to improve the safety of cars and improve the stability of cross-winds.First of all,the car surface model is simplified appropriately,and two common unstable crosswind models,sine crosswinds on open roads and gusts across tunnels,are built on the STAR-CCM+ software model.Especially in the wind gust model passing through the tunnel entrance,in order to obtain a continuous aerodynamic load curve,the method of overlapping grids is adopted to allow the body model grid to move in the calculation domain grid and cross the wind gust zone as in real road conditions.Through such an appropriate simulation method,the aerodynamic load curve of the car is obtained in two cases.Secondly,based on the knowledge of vehicle system dynamics and the actual vehicle data of a certain SUV,a body model of four degrees of freedom of body side,vertical,yaw,and roll was established on Simulink,a suspension model,and a magic tire formula Based on the nonlinear tire model,a vehicle model is formed.And Carsim simulation provides a certain reference for the accuracy of the model.Finally,according to the advantages and disadvantages of the two control methods of AFS and DYC,the coordinated control strategy is used to complement the two control methods.According to the tire’s cornering angle and lateral force area,the working area of AFS and DYC is divided.Among them,the AFS control takes the deviation of the actual center-of-mass lateral yaw angle and yaw rate as the corresponding reference value,and outputs the front wheel angle to correct the steering;the input of the DYC control is the same as the AFS,and the output yaw moment is output to resist external interference.The simulation results of the vehicle under uncontrolled,separate AFS control,separate DYC control and AFS+DYC coordinated control under two types of unstable crosswinds are compared.The results show that in both cases,the three control methods have significantly improved the crosswind stability of the car compared with no control,and coordinated control can synthesize the advantages of AFS control in stability and maneuverability and DYC’s track retention ability.Compared with the single control,it can better resist external interference.