1．目的及意义

1． Purpose and significance (including domestic and foreignresearch status analysis)

With the development of China'sautomobile industry, it is necessary to carry out independent research anddevelopment of key auto parts. The safety of automobile braking process hasalso become the focus of attention. The anti-lock braking system of automobileis related to the safety of automobile braking. A few days ago, many domesticautomobile companies have begun to carry out independent research anddevelopment of automobiles. In order to stand out in the commercialcompetition, to have independent intellectual property rights of the car, inorder to make our country from an automobile power to an automobile power, itis necessary to carry out independent research and development of key autoparts. The safety of automobile braking process has become the focus ofattention. anti-lock braking system ABS is one of the key parts of automobile.The improvement of automobile dynamic performance and the extension ofexpressway put forward higher and higher requirements for automobile safety.many countries have promulgated strict automobile safety laws and regulations,and the directional stability and steering control ability of automobile in thebraking process. Has become the focus of attention. Therefore, it is animportant measure to reduce traffic accidents and promote the development ofautomobile industry to explore various high-performance braking systems andimprove the performance of braking systems. The ABS can automatically andfrequently adjust the pressure of the braking system in the braking process, soas to adjust the braking force, so that the wheel slip rate can be kept nearthe ideal confusion rate, thus preventing the wheel from clinging to death. Italso makes full use of the adhesion ability between the wheel and the road,shortens the braking away, improves the direction stability and steeringoperation ability in the braking process, and achieves the best braking effect.One of the keys of ABS control is to control the slip rate in the brakingprocess, so as to improve the utilization ratio of road adhesion coefficient,shorten the braking and leave, and improve the braking stability. However, therelationship between slip ratio and road adhesion coefficient is affected bymany factors, such as the structural parameters of the vehicle itself, speed,tire inflation pressure, tire vertical load, road conditions and so on.

The theory of anti-lock braking was first putforward by the British in 1928. the braking system based on anti-lock brakingtheory was first applied to trains and aircraft. The earliest official recordof an anti-lock braking system was issued in the United Kingdom in 1932 underpatent 382241. ABS began to be used in cars in the mid-1950s. in 1954, FordMotor Company installed Air France's ABS device on Lincoln car. the controlpart of this ABS device is mechanical and has a complex structure. The functionis relatively single, only in specific vehicles and working conditions,anti-lock braking control is effective, so the braking effect is not ideal. Thecomplex mechanical structure makes the reliability of the ABS device poor, thecontrol precision low and the price on the high side. It is difficult topopularize and apply ABS technology in automobile. Until the late 1970s, due tothe rapid development of electronic technology, it provided reliable technicalsupport for the application of ABS technology in automobiles. The ABS controlpart adopts electronic control, and its reaction speed, control accuracy andreliability are significantly improved, and the braking effect is alsoobviously improved. at the same time, its volume is gradually smaller, itsquality is gradually reduced, and its control and diagnostic functions areconstantly enhanced. Prices are also gradually falling. During this period,many companies have developed a variety of ABS devices. After entering the1990s, ABS technology has been continuously developed and matured, and thecontrol accuracy and control function have been constantly improved. Now ABStechnology has been widely used in developed countries. The research work onABS in China began in the early 1980s. the research and development unitsinclude Dongfeng Automobile Company, Chongqing Highway Institute of Ministry ofCommunications, Chongqing Hongan ABS Co., Ltd., Shaanxi Xingping 514 Factoryand Xi'an Jiaotong University, etc. Dongfeng Motor Company began to study ABSin the early 1980s. the company analyzed, tested, improved and digested Wabco'sABS products. the ABS of wabco was installed on EQ-145 and tested on variousroads. Since 1998, China's self-built Audi cars, Santana cars and Fukang andother driving vehicles have been equipped with ABS system. Since 2003, the ABShas become the benchmark for small passenger cars. In terms of theoreticalresearch, The State key Laboratory of Automobile dynamic Simulation,represented by Academician Guo Konghui of Jilin University, has made a lot ofachievements in the establishment of tire model: professor Song Jian of Statekey Laboratory of Automobile Safety and Energy Saving of Tsinghua Universityand others. ABS has been studied in many aspects. In terms of pneumatic ABS,domestic enterprises, including Dongfeng Electronic Technology Co., Ltd.,Chongqing Juneng, Guangdong Comi, and so on, have formed a certain scale ofproduction: hydraulic ABS because of its technical difficulties, foreigntechnical blockade is tight, Domestic enterprises can not produce independentlyfor the time being, but they are also doing independent research anddevelopment in hydraulic ABS, trying to break through the technical barriers offoreign multinational companies, and have made some new progress andbreakthroughs.{title}

2. 研究的基本内容与方案

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2. The basic content， objectives andtechnical solutions or measures of the design

ABS is mainly composed of hydrauliccontrol unit, electronic control unit and speed sensor.

When the vehicle is in emergencybraking, the estimation module in the electronic control unit judges the stateof the vehicle according to the feedback wheel speed signal of the wheel speedsensor, And according to the estimation result, the control instruction isissued to the HCU element, To ensure that the vehicle can travel near theoptimal slip rate.

Each hydraulic control unit is composedof four booster valves, four pressure reducing valves, two accumulators, tworeturn pumps and a DC motor. Each cylinder corresponds to a booster valve and arelief valve.

The wheel cylinder pressurization modeis linear pressurization, and the four booster valves in the HCU are of thesame specification; the wheel cylinder decompression mode is steppeddecompression, in order to ensure the consistency of the braking effect, Thepressure reducing valve needs to meet different flow requirements.

AMESIM is the mainstream platform foradvanced modeling and simulation of complex systems in multidisciplinaryfields. It is mainly used in modeling, simulation and dynamic analysis ofhydraulic / mechanical system. It uses intuitive icon symbols to represent thevarious components of the system, including the basic library of variousdisciplines involved in the vehicle: mechanical, hydraulic, pneumatic andelectromagnetic components.

3. The steps of building the model are asfollows:

1. the mathematical model ofABS hydraulic system is established, which shows the composition of the modelobject and each link of the working process.