Study On Vehicle Differential Brake Control After Tire Blowout

The tire blowout is an extremely dangerous situation for the vehicle at high speed. Dueto the psychological panic, the drivers tend to take excessive even wrong operations after tireblowout, which ultimately leads to vicious accidents. The previous researches had largelyfocused on accident prevention and loss reduction, while some of the researches were nottargeted, and some lacked the practical application conditions in the short term.Though the consequent casualties and property losses are tremendous, but the relatedissues are not thorough. On the basis of the research work at home and abroad, thedissertation takes a domestic A-Class vehicle as the object to study the active safety afterblowout. Concerning several main aspects, such as the mechanical properties tests of the tireafter blowout, the relevant tire modeling, the movement characteristics of the vehicle, alsothe driver model for trajectory following and the differential brake control after tireexplosion, the dissertation carries out the following research work:1. The establishment of the tire model after blowout. The mechanical properties of thetire change largely after blowout, so a reasonable and accurate tire model is essential forfurther research on the movement characteristics of the vehicle. Given this, the author firstlytests the mechanical characteristics for the tire under standard tire pressure and zero tirepressure and analyzes the corresponding changes of the tire characteristics when the loadchanges. Based on the UniTire model, several key parameters of the mechanicalcharacteristics, which changes greatly after tire blowout, are modified. And the UniTiremodel for the tire explosion is established when the bead unseating and the rim got stuck inthe ground cracks, so as to improve the accuracy and extend the application range ofUniTire.2. The research on the movement characteristics of the vehicle after tire blowout.Similarly, there exist remarkable changes in the movement characteristics of the vehicle aftertire blowout, which is the key factor for the vehicle’s stability control. Besides the variation of the tire’s work conditions, the dissertation analyzes the influence of the flat tire on thewheel alignment parameters. Specially, the influence of the steering front wheel on thesteering system is also considered. Then the movement characteristics of the vehicle affectedby these factors are discussed in this thesis. With the established blowout tire model and thevehicle dynamics simulation model, the author carries out the analysis of the movementcharacteristics of the vehicle when different tires punctured. Moreover, the correspondingvehicle tests are conducted initially.3. The research on the driver model for trajectory following of the vehicle. Applying thedriver model to the vehicle simulation after tire explosion, the author discusses the precisiondecrease in trajectory following faced by the driver model, and points out it is the change insteering response characteristics that leads the driver model unable to control the vehicleback to its original path when tire blowing out. In addition, having built and simulated thedriver model considering the asymmetric left, right steering characteristic, the paper indeedimproves the trajectory following accuracy. After the foregoing analysis, a state referencedevice is added to the driver model. When a deviation exists, compared with the ideal state,it would compensate the steering wheel angle of the driver model. In other words, with theestablishment of the driver model for trajectory following, the corresponding followingprecision is improved in the tire blowout simulation.4. The differential brake control of the vehicle after tire blowout. It is known to all thatthe tire blowout at high speed is extremely dangerous, and the vast majority of drivers do nothave relevant experience of handling this, which would directly lead to a serious trafficaccident. So it is necessary to do a research on the control strategy so as to assist the driversto control the vehicles’ stability and movements after tire blowout. Considering the actualsituation of the tire blowout, the dissertation analyzes its affect on the parameters of thecontrol model and modifies the optimal yaw moment. Then the control measures to preventtire from bead unseating are put forward. In addition to the selection principle of the brakewheels after tire blowout, the author also establishes the relations between the wheel cylinderbraking pressure and the yaw moment, followed by the estimation of the slip angle for the vehicle and the judgment of tire blowout. Necessarily, considering tire blowout underdifferent conditions, the simulations are carried out with the control strategy mentionedabove, which ensures the stability of the vehicle. Meanwhile, the trajectory deviation of thevehicle is decreased and the steering operation is easier for maneuvering.5. The validation for driver in the loop control. To some extent, what the drivers doafter tire blowout would directly affect the movement state and the stability of the vehicle.While the fact is that the drivers’ operations are of great uncertainty, and the accurate drivermodel is subsequently hard to build. Therefore, the dissertation turns to the dSPACE, a realtime simulation platform. After linking the UniTire model for tire blowout and the vehiclemodel to the dSPACE, the author studies the influences of drivers’ operations on themovement state of the vehicle. With the control system embedded in the simulation platform,the driver in the loop control is validated.Major innovation points of this dissertation are as follows:1、The mechanical characteristics are tested for the tire under standard tire pressure andzero tire pressure. Based on the test results and the load, the UniTire model for tire blowoutis established, and the characteristics could be accurately prescribed.2、The precision decrease in trajectory following faced by the driver model is deeplyanalyzed. In view of this, the driver model for the trajectory following after tire blowout isbuilt, which improves the precision of the model.3、Given the actual situation, the differential brake control strategy after tire blowout,which is based on electronic stability program, is proposed, whose participation in the modelensures the stability. Besides, the trajectory deviation of the vehicle is decreased and thesteering is easier for maneuvering.4、Assisted by the real time simulation platform dSPACE, the UniTire model for tireblowout and the vehicle model are linked to dSPACE. Then the drivers’ operations are takeninto consideration. With the control system embedded in the real time simulation platform,the driver in the loop control for tire blowout is verified effectively.