The Electronic Braking System Based On Fuzzy Control

Since the vehicles come into being, the braking system plays the mostimportant role in the safety of vehicles. Especially there are more and morehigh-rank roads and the speed keeps increasing recent years, people'srequirements for safety have been increasing. It's urgent that how to makethe vehicles traveling in high speed slow down and stop safely and stably inas short time and distance as possible. Although traditional braking systemsin vehicles are reliable and economic, there are disadvantages such as slowreaction, long distance to stop, low safety, brake fluid's pollution and so onbecause of long pipelines and too many components of valve.Since 20th century 70s, technologies of electronic have beendeveloping rapidly and widely used in vehicles and the electronic brakingsystem is round the corner. The electronic braking system replaces all thepipelines and components pressed by oil in traditional braking systems withelectronic circuitry and electronic components and uses motors instead ofthe conventional hydraulic disk and drum brake actuators. It has manyadvantages such as rapid response, high accuracy, less pollution, easier tofix and so on. It's the direction of braking system in vehicles. Electronicbraking system is made up of braking module and electronic control module.The braking module includes braking pedal, actuators and so on and theelectronic control module includes ECU controller, kinds of sensors,electronic control circuitry and so on. The electronic control module is mostimportant because it gains the driver's intention by sensors, transportsinformation by electronic circuitry, analyses the information gained andtakes the most rational action.The electronic braking system is a device which controls the motors tomake the vehicles slowdown according to the driver's stepping on thebraking pedal. The basic functions of electronic braking system is that while driving, driver steps on the braking pedal to decelerate and the ECUcontrols the motors to rotate forward that makes the brake dram press thebrake disc to produce brake force and makes the vehicles slowdown. Thissystem not only realizes the basic functions of electronic braking system,but also adds the function of auxiliary braking by using parking brakesystem. It works when the driver steps on the braking pedal to deceleratebut the braking system is invalid for problems of actuators. It uses theactuators of park braking system to brake.In traditional braking systems the brake force is absolutely decided bythe braking pedal with no feedback. It can't fit the changing ofenvironments and actuators and it's not accuracy. We use a new strategy ofcontrolling here. The brake force is decided by the braking pedal andacceleration which is taken as feedback to improve the system. Whilecontrolling, it has a comparison between real-time acceleration andanticipated value and takes the error of acceleration and the change of erroras inputs to generate output by querying the fuzzy control table. The usingof fuzzy control theory can not only avoid the requirements of setting upaccuracy math model of braking system, but also increase rudeness andsatiability of the system. It's not sensitivity to little change, so it makessense that the actuators can work longer. We mainly do research in hardwareand software of electronic braking system.About hardware system, we choose P80C592 of PHILIPS, which is8-bit, cheap, with high performance and widely used, as MCU; chooseVNH3SP30 of ST, which can output high power and has high security, todrive motors; choose linear displacement sensor for collecting acceleratingpedal and braking pedal, Howl sensor for collecting wheel's signal tocalculate speed; choose appropriate motors for braking system and auxiliarybraking system separately. This system has advantages of fast response,high accuracy and high power which can fit the requirements of brakingsystem. It also has circuitry for reset, power supply conversion, filteringwhich can make the system more reliable and field bus——CAN which is designed for further use.About software, there are several parts: accomplish the collection ofinputs including auxiliary switch, pulse of speed, accelerating pedal andbraking pedal; choose fuzzy control logic as strategy for controlling and setup a whole fuzzy control system which takes the error of acceleration andthe change of error as inputs and takes offset of PWM as output, includingfuzzy interface, rule base, inference machine and defuzzy interface; useToolBox of MATLAB to set up fuzzy control model to describe the relationbetween input and output and gain good performance; add auxiliary brakingsystem to electronic braking system besides basic function and make themwork well together; finally design the structure with modular and writeprograms in C language.It carries out an electronic braking system which consists of wholestructure of hardware and functions of software. Besides the basic functionof electronic braking system, it adds the function of auxiliary brakingsystem to fit the requirements of safety. The performance of whole systemproves that it fully fits the requirements by testing. But there are still manyproblems which are worth of doing further research. Such as use fuzzycontrol logic to design functions of self-fitness and self-diagnosis which cangreatly reduce effects by the faults of system; improve the intelligence ofelectronic control system which allows system to identify currentenvironments and type of drivers to take the best action and do research inHEV which makes vehicles more powerful and economic; add ABS,TCSwhich can improve the performance of braking system to the system and soon. All of these make great sense and could develop further.