Simulation Of The Automotive ABS/EBD Based On Fuzzy Control

With the social development and the progress of automotive technology, carrying trade and transportation shows the trend that the speed of vehicles is higher and higher, more and more drivers are non-occupational. So the number of traffic accident becomes more and more, and it has become one of the social hazards. In order to reduce traffic accidents, how to improve the vehicle's active safety has become a popular automotive research topic. Among the major features in the car, the brake is a very important factor about active safety of vehicles. Automobile anti-lock braking system (ABS) can prevent the wheels from being locked during the braking process, so that the vehicle keeps the ability to turn, and it prevent the vehicle from the dangerous situations caused by rear wheels locked, such as sideslip and swing. So ABS could improve the vehicle braking greatly. As the ABS-assisted devices, Electronic Brake force Distribution (EBD) could automatically adjust the braking force distribution scale among the wheels, so that the wheels reach the start condition of ABS at the same time, the vehicles are always in a stable state in the braking process, and braking of vehicles has become more perfect.With the hydraulic braking system as the object of study, this paper made an in-depth study on the linear braking of vehicles. And with fuzzy theory as base it put forward the control strategies about wheel cylinder pressure, ABS, EBD with front and rear braking force distribution function, and ABS+EBD. And simulation tests were conducted. Main contents are as follows:(1) Based on the automobile theory of braking, ABS and EBD structure, working principle and developments were introduced.(2) This study established a simplified 5-DOF vehicle model and a 1/4 vehicle model with only single wheel, made a estimate computing to the reference speed based on the dynamics theory of the motor vehicle, established tire models on three classic roads using the Magic Formula, established the mathematical model of the hydraulic brake-by-wire system, and lay the theory foundation for the simulation below.(3) According to the characteristics of wheel cylinder pressure control, the paper designed the fuzzy controller, and created the system simulation model in the MATLAB/Simulink. And according to the analysis of simulation results, the fuzzy controller was trying to be improved .The following simulation results proved that the improved self-adjusting fuzzy controller could control the wheel cylinder pressure more perfectly. The self-adjusting fuzzy control method was compared with the traditional PID control method, and the results showed that the self-adjusting fuzzy control method is better on the wheel cylinder pressure control.(4) The ABS fuzzy controller based on slip rate was designed. Next, the paper created a simulation model of the system in the MATLAB/Simulink. Through simulation analysis, it imported amendatory parameters for the output of the fuzzy controller, so that the fuzzy controller is self-adjusting, and the simulation results proved that the fluctuations of the wheel cylinder pressure and slip rate were amended, and the results were satisfactory. The ABS road identification method based on the characteristics of attachment coefficient was introduced, and the simulation results proved that the method could identify the best slip rates of different roads quickly and accurately, it is applicable to the single road and also the break road.(5) Two braking force distribution control strategies based on the vertical load and slip rate were introduced. Simulation results show that the both methods can be an ideal distribution the braking force. Taking the advantages and disadvantages into account, the paper makes the control method based on vertical force as the ultimate control strategy of the EBD in this article. Comparison of three types of vehicle brake simulation results indicate: ABS and ABS+EBD system can both greatly improve the braking performance of vehicles, and little difference between the two. In addition, the smaller fluctuations of curve of the factors including slip ratio, press of wheel cylinder and braking force coefficient indicate that ABS+EBD is better than ABS.In this paper, a number of new solutions for ABS and EBD research difficulties were introduced. For example: it made a estimate computing to the reference speed based on the dynamics theory of the motor vehicle, made the accurate wheel cylinder pressure control come true by the self-adjusting fuzzy controller, introduced the ABS road identification method based on the characteristics of attachment coefficient, made some changes in the ABS fuzzy controller to as the EBD controller, etc.