Resesrch On Dynamic Modeling And Active Control Algoirthm Of Tire Blow-out Vehicle

The tire is the only carrier of the vehicle and the road, and plays an important role in attenuating the impact from the road, supporting the vehicle and providing the basic condition for driving. Once a tire bursts when the vehicle runs at a high speed, the lives and property would be threaten seriously. In order to avoid serious traffic accidents caused by tire blow-out, on the one hand, tire pressure monitoring system is established to provide real-time tire pressure information and the tire pressure warning message to alert the driver, which can effectively prevent the occurrence of tire blow-out; on the other hand, an effective control system is needed after the tire blows-out to maintain the stability of the vehicle in order to avoid crashes, rollover and other accidents.For the safety issue caused by the tire blowout, the vehicle dynamic and active control after the tire blowout is focused on in this paper based on the research of domestic and foreign scholars, which is mainly composed of the following aspects:(1) After the tire blowout, the wheel rolling radius decreases, and hanging force is re-distributed, besides the interference of the vehicle roll and pitch moment, the increase of the roll resistance and the rotational arm around the kingpin and the decrease of the steering stiffness exist. Therefore, in order to study the vehicle dynamic after tire blow-out, a high-degree of freedom vehicle model based on multi-body dynamics using Matlab/Simulink is established, and compare with the simulation results of the CarSim, which proves that the vehicle model has better response to the vehicle dynamic response.(2) Because of the decrease of tire pressure after blowing-out, the characteristical parameters of the tire change corresponding, such as smaller longitudinal slip stiffness, smaller lateral stiffness, smaller inclined stiffness, smaller radial stiffness, the increase of rolling resistance moment and so on. Therefore, the theoretical model of the tire pressure changes after blowing-out is established, and the relationship between the tire's characteristical parameters and pressure is considered, and the blow-out tire model based on Unitire model proposed by Professor Guo is estabilished.(3) Based on the theoretical model of the tire pressure changes after blowing-out, the tire blow-out method based on the threshold of changing rate of the tire pressure is described. When the tire pressure sensor is invaluable, an indirect method is adopted, that is, the value of the rear wheel rotational speed product divided by the front wheel rotational speed product is calculated, and at the same time the changes of rotational accelerate speed of the blow-out tire is considered to achieve the goal of auxiliary tire blowing-out identification.(4) When the tire blows-out, greater torque is impacted on the steering wheel, and the vehicle stability is kept by the way of differential braking control after tire blows-out, and at the same time the impact of torque on the steering wheel is affected. The electric power steering system(EPS) acts as a platform in this paper, the dynamic model of EPS is established firstly, and then the impact of torque from the ground when tire blows-out is estimated. Compensation current for attenuating the impact of torque on the steering wheel is added on the basis of the original EPS boost electric current in order to prevent steering shocking by the impact of torque caused by blow-out tire and differential braking control.(5) For the issue of the vehicle stability after tire blow-out, the effects of yaw rate and slip angle on the vehicle stability are analyzed, and then the 2_degrees of freedom vehicle model is chosen as the reference model, then the deviation of the ideal value and the actual value of vehicle yaw rate and slip angle is calculated, and an optimal yaw moment based on LQR methods is obtained, and yaw angle error is introduced to correct the yaw moment, then the yaw moment among the wheels is distributed rationally by certain rule, and lastly the target wheel cylinder pressure is calculated.(6) An electronic hydraulic brake system(EHB) model is established by Matlab/Simulink in this paper, and the accuracy of the brake system model is verified by the EHB bench test. The energy device in EHB system is high-pressure accumulator which can make the wheel cylinder full of high pressure oil in a short time improving the system response. After determining the target wheel cylinder pressure of each wheel, then the solenoid valve in EHB system is controlled by adjusting the duty cycle in order to insure that the pressure of wheel cylinder can follow its target value.(7) Finally, based on the previous research, the simulation on the vehicle dynamic and active control after the tire blows-out in the conditions of lining and steering traveling in different road adhesion. On the one hand, the vehicle dynamic response is analyzed after the tire blows-out, and on the other hand the effectiveness of the proposed active control algorithm is verified.