Tire Blow-Out Transient Behavior And Its Effect On Vehicle Response

Tire Blow-Out on high speed is an extremely dangerous condition, often leads toserious traffic accidents. The objective of this paper is to provide technical supportsfor active safety of vehicles by studying the transient behavior of blow-out tire and itsinfluence on vehicle response.In this dissertation, a tire blow-out steady model is established basing a series oftire mechanical property tests under different loads and pressures firstly. The tireblow-out model is integrated by this model and non-steady tire model which takescarcass flexibility into account. Secondly, blow-out test is carried on and the blow-outmodel is verified which gets a good accuracy. Thirdly, the tire blow-out model isimbedded in CarSim software to study the transient response of vehicle with tiredeflated and tire pressure will calculated real-time with a theoretical model. At last,tire pressure is identified by Extended Kalman Filter(EKF) based on seven degrees offreedom vehicle model. There are six chapters in this thesis.Chapter one is the foreword, mainly introduces the research background and themeaning of this research. At the same time, the current status of research at home andabroad on blow-out tire is described briefly.Chapter two describes the method to build tire non-steady model basing carcassflexibility including concept definition and modeling approach in detail. Theflexibility of blow-out tire is stated: the vertical force will redistribute on differenttires and tire pressure will totally lose in a very short time, the change of tire pressureand load will induce the change of tire carcass flexibility. At last, the simulationprocedure of blown tire’s mechanical property is described in this chapter.In order to acquire tire cornering stiffness, aligning stiffness, camber stiffness,vertical stiffness, effective radius and rolling resistance force, some steady-state tiretests are carried on in chapter three. The step slip angle test is also carried on with thepurpose of obtaining tire carcass stiffness. The concept of equivalent pressure isintroduced so as to revise the difference of tire test data at high speed and low speed,and the concept is proved with finite element technique in Abaqus. Method of blowntire’s mechanical property test is designed and experiment is carried through theautomatic tire puncture device. Considering the change of tire pressure, blow-out tire steady model is built up based on UniTire model which constructs the blow-out tiremodel together with non-steady tire model involving carcass flexibility. Blow-out tiremodel is verified by the data from tire deflated procedure.Chapter four focuses on the vehicle response with burst tire. Firstly, a theoreticalmodel is deduced to calculate tire pressure real-time and simulation results show thatthe model gets a high accuracy with gap acreage as the only model input. Secondly,the tire blow-out model is connected to CarSim software through Matlab/Simulink inwhich some simulations are conducted. After analyzing the simulation data, thefollowing results can be achieved:1) Tire blow-out will cause huge change to vehicle in vertical direction. Tirevertical load, wheel center position, damping force will change significantly. Themass center will drop down when the front tire burst and the position will be almostunchanged when the rear tire burst.2) The lateral response is very small when the vehicle is running in a line withtire bursting. When the vehicle is running in a turn, the steering character tends toundersteer if the front outside tire bursts and it tends to oversteer when the rearoutside tire bursts.3) Regardless of whether the tire blows out in a line or in a turn, the longitudinalresponse of the vehicle is quite small.Chapter five studies the method of blow-out identification based on EKF. Inorder to observe all tires’ gap acreage and pressure at the same time, an EKF stateobserver is designed with the assumption of the lateral acceleration of the vehicle andsuspension damping forces can be measured. The result shows that seven degrees offreedom vehicle model can express the damping forces of suspension well and thestate estimation algorithm presented in this paper can observe the pressure in differenttire accurately.Chapter six is the conclusion and summary of whole paper. The prospects offuture research are also stated in chapter six.