Study On Vehicle Dynamic Response To Tire Blow-out Based On CarSim And UniTire

Tire blow-out is a very dangerous condition while vehicle running in high velocity. If drivers perform wrong controls such as various amounts of steering and breaking after tire blow-out, it will lead the vehicle out of control. The objective of this thesis is to alleviate or eliminate the dangers or accidents caused by tire blow-out.In this thesis, the fundamental theory and the structure of UniTire model are introduced. Lots of tire experiments are executed to study the blown tire's properties. Based on tire test data and UniTire Model, this thesis sets up a tire blow-out model. The tire blow-out model is applied in CarSim to make some simulations to study the vehicle dynamic response to tire blow-out. Blow-out Motoring and Break System (BMBS) is introduced and its effect in maintaining vehicle stability after tire blow-out is analyzed by simulations. There are six chapters in the thesis.In Chapter One, the background and significance of study on vehicle dynamic response to tire blow-out are introduced. The history of that study and its present status are discussed. CarSim, a well known vehicle dynamic software is briefly introduced. The contents of this thesis are put forward.In Chapter Two, the basic concepts and structure of UniTire model arepresented, including the definition of contact patch, Contact Process coordinate system and slip ratio. The input and output of UniTire model and its main formulas are also presented.In Chapter Three, Lots of tire experiments are executed to study the blown tire's dynamic properties. In the light of tire test data and UniTire Model, this thesis builds a tire blow-out model. At first, the blown tire test is designed and realized, including side slip, longitudinal slip and camber slip experiments. Radial tire stiffness and rolling resistance are also measured through tire tests. The test data reveals that tire's properties will change a lot after blow-out. The greatest effect of reduced inflation is on cornering stiffness, longitudinal stiffness, camber stiffness, radial tire stiffness and rolling resistance coefficient. Rolling resistance coefficient will increase, while radial tire stiffness, cornering stiffness, longitudinal stiffness and camber stiffness will decrease. When the test tire of this thesis is concerned, its rolling resistance coefficient increases to about 20 times of its normal value, while its radial tire stiffness drops to about 1/15 of its normal value, cornering stiffness drops to about 25 percent of its normal value, longitudinal stiffness drops to about 28 percent of its normal value, and camber stiffness drops to about 66 percent of its normal value. The bead unseating resistance will rapidly decrease after tire blow-out, so that the smaller later force will induce bead unseating. Secondly, in the light of tire test data and UniTire Model, a tire blow-out model is established. In the tire blow-out model, it's the first time to consider the effect of rim touching road directly.In Chapter Four, the tire blow-out model is applied in CarSim to make simulations to study the vehicle dynamic response to tire blow-out. With the simulations and analysis, the following results can be deduced.(1) The decrease of blown tire's cornering stiffness will lead steering characteristics to change. Font tire blow-out may potentially lead to under-steer. While rear tire blow-out may potentially lead to over-steer. As a result of the air loss at the right front or right rear tire, the blown tire's additional rolling resistance produces a clockwise moment on the vehicle. As a result, the vehicle begins to driftto the right. The K&C characteristics of Suspension may have some effect on the vehicle response after tire blow-out.(2) A tire blow-out alone does not lead to an inevitable loss of control. Drivers'correct response operation can let the vehicle whose tire blow-outs when straight-ahead or the outside front tire blow-out when turning out of dangerous situation. However there is nothing the driver can do to prevent loss of control, if the vehicle's outside rear tire blow-outs when turning. The vehicle will spin out. Therefore, it is more critical in the case outside rear tire blow-out when turning.(3) As a result of the steering characteristics change, it makes more difficult for driver to drive the vehicle. So that driver may easily make mistakes at the moment of tire blow-out, which may lead to loss of control of the vehicle and cause accidents. Under the driver's wrong reaction operation, Font tire blow-out may potentially cause rollover of the vehicle. Rear tire blow-out may potentially cause the vehicle spin out.In Chapter Five, some techniques to alleviate or eliminate the dangers or accidents caused by tire blow-out are presented. In this chapter, the strategy of Blow-out Motoring and Break System (BMBS) is introduced and its effect in maintaining vehicle stability after tire blow-out is analyzed by simulating the conditions in which the vehicle's tires blow-out during straight-ahead or turning. The simulation results reveal the following. BMBS can let the vehicle whose tire blow-outs when straight-ahead or the outside front tire blow-outs when turning out of dangerous situation. However BMBS can do nothing to prevent loss of control if the vehicle's outside rear tire blow-outs when turning. The vehicle will spin out.Chapter Six is the summary and conclusion. And the recommendations for further development of the study are put forward.The main creative works of this thesis lie in the following:(1) Based on blown tire's experiments, the blown tire's properties are discussed in detail.(2) On the basis of tire test data and UniTire Model, a tire blow-out model is established. In the tire blow-out model, it's the first time to consider the effect ofrim touching road directly.