Research On The Handling Stability Of Full Drive Three-axle Vehicle

Multi-axle commercial vehicles with the dual front axle steering structure are widelyused; therefore a methodology for the prediction of handling properties of such vehiclesis quite valuable. This paper aims to study the handling and stability of a double frontaxle steering66heavy vehicle, in order to discuss the factors that affect vehicleperformance, and research the design method to improve vehicle handling and stability.Firstly, use mathematical dynamic model have two degrees of freedom of bothsingle and dual front axle steering vehicle to study there steady-state characteristics ofsteering wheel angle step input and find the difference between them. In addition researchthe effect of mass center and tire cornering stiffness variation on the double front axlesteering vehicle’s time domain response. Secondly, a multibody dynamics model wasbuilt based on vehicle quality and structure information and the virtual simulation referthe national standard provides a comprehensive assessment of the studied handling andstability. Then the multibody dynamic model was used to verify analysis result of themathematical model, as well as the effect of tread and different driving system on vehiclehandling and stability. Put forward the optimization of vehicle parameters according tothe analysis results, the optimization results verify the improvement of vehicleperformance.The results illustrate that the equivalent wheelbase of a dual front axle steeringthree-axle vehicle is equal to the distance between the front axle and rear axle. Thesteering sensitivity is expressed in terms of vehicle geometry and cornering stiffness ofthe front and rear axle, the result of front wheel cornering stiffness multiply distancebetween middle and rear axle subtract rear wheel cornering stiffness multiply distancebetween front and middle axle is negative dual front axle steering sensitivity is higherthan the front axle steering. The shorter the distance between the center of mass relativeto the front axle the larger vehicle understeer characteristic; also the longer the wheelbasethe smaller the value of transient response of stable while lower steering sensitivity. Inaddition, a larger rear cornering stiffness can help to improve vehicle understeercharacteristic; a larger tread can improve the response speed. Vehicle handlingperformance under different driving mode shows that the front and middle axle drive canhelp improve yaw rate reaponse speed and has a smaller steady-state response of steering wheel angle step input. Vehicle handling and stability evaluation indicate that theresearched car have good understeer feature, also good at steering reversal and agility butthe response to steering wheel angle step input have large yaw rate steady-state value andslowly response. Therefore put forward an optimization proposal to improve the transientresponse of vehicle handling and stability performance based on the analysis before;more over compare vehicle performance before and after the optimization proof that thevehicle performance has been effectively improved.