Function of ABS
ABS can automatically adjust the braking pressure of the wheel according to the movement of the wheel during braking to prevent the wheel from locking. Its essence is to change the traditional braking process into an instantaneous control process, that is, to make the wheel and the ground reach the state of "holding but not dying, dying without holding" when braking. Its purpose is to maximize the friction between the wheel and the ground, and at the same time avoid the rear wheel slipping and the front wheel losing its steering ability, so that the car can achieve the best braking efficiency. Therefore, ABS has the following advantages:
Shorten the braking distance. ABS can ensure that the car can obtain high braking efficiency after rain, snow and muddy roads, and prevent the car from slipping and swinging its tail (except for roads with loose sand and deep snow);
Maintain directional stability when braking; 32692549
Maintain steering stability when braking;
Reduce tire wear during automobile braking. ABS can prevent the tire from producing serious drag marks during braking and improve the service life of the tire.
Reduce the driver's fatigue strength (especially the tension when braking).
In view of the above advantages of anti-lock braking system (ABS), the loading rate of the system is increasing year by year.
ABS technology was developed and patented by British Horner Moore in 1920. As early as 1930s, ABS has been applied to the braking system of railway locomotives, aiming at preventing the vehicle from locking up during braking, resulting in premature damage due to local severe friction between wheels and rails. 1936 Bosch Company of Germany obtained ABS patent right. It consists of an electromagnetic speed sensor installed on the wheel and an electromagnetic valve for controlling hydraulic pressure, and the braking pressure is controlled by switching method.
At the end of the 1940s, in order to shorten the taxiing distance when the aircraft landed and prevent the wheels from running off, tail flick and serious tire wear during braking, the aircraft braking system adopted ABS, which soon became the standard equipment of the aircraft. In 1950s, anti-lock braking system began to be used in automobile industry. 195 1 year Goodyear Airlines installed on trucks; 1954 Ford Motor Company installed the ABS device of Air France on Lincoln.
1978 ABS system made a breakthrough. Bosch Company cooperated with Mercedes-Benz Company to develop a three-channel four-wheel digital controller ABS system, and installed it on Mercedes-Benz cars in batches. Due to the introduction of microprocessor, ABS system began to be intelligent, thus laying the foundation and basic mode of ABS system.
198 1 year, webeco and Mercedes-Benz in Germany installed digital ABS system on trucks. The market share of ABS has risen rapidly. Since the mid-1980s, with the progress of electronic control technology, ABS has become more sensitive, cheaper, more convenient to install and more easily accepted by small and medium-sized family cars. Typical ABS devices during this period are1BOSch2 introduced by bosch company in 1979, and1ABS/ASR 2U with anti-lock braking and anti-skid function introduced by Twiss company in Chinese mainland in 1984. With the continuous development and perfection of mechanical and electronic components, the advantages of ABS are becoming more and more obvious. With the fierce competition and mature technology, ABS has become more accurate and reliable, and the price is also falling.
1987, the EU * * issued a regulation requiring that all new models produced by all EU member States should be equipped with anti-lock braking devices from 199 1. At the same time, it is stipulated that all trucks with load 16t must be equipped with ABS, and cars without this device are prohibited from being imported. According to Japanese regulations, from 199 1 year, all tractors, trailers and buses running on expressways with total mass exceeding 13t must be equipped with ABS.
At present, ABS is widely used in automobiles internationally and has become the standard equipment for most types of automobiles. In North America and Western Europe, the equipped rate of ABS for passenger cars and light trucks is over 90%, the equipped rate of ABS for cars is about 60%, and the equipped rate of ABS for trucks transporting dangerous goods is 100%.
The present situation of asset securitization in China
The research on asset securitization in China began in the early 1980s. At present, the Chinese government has formulated a mandatory regulation on vehicle safety GB 12676- 1999 "Structure, Performance and Test Method of Automobile Brake System", which stipulates that heavy-duty vehicles and buses should be equipped with electronically controlled ABS first. GB7258-2004 "Technical Conditions for Motor Vehicle Operation Safety" also stipulates the vehicle type and time that must be installed. It is stipulated that long-distance buses and tourist buses with a total mass greater than 12000kg, trucks with trailers with a total mass greater than 16000kg and trailers with a total mass greater than 10000kg must be equipped with ABS.
There are many domestic units and enterprises engaged in ABS research, such as Dongfeng Motor Corporation, Chongqing Highway Research Institute, Beijing Institute of Technology, Tsinghua University, Shanghai Automobile Brake System Co., Ltd., Shandong Heavy Duty Truck Group, etc. Among them, Shandong Heavy Duty Truck Group has made some progress in introducing international advanced technology for research. The pneumatic braking FKX-ACI ABS device developed by Chongqing Highway Research Institute for medium-sized cars has passed the national technical appraisal, but its adaptability to various braking situations needs to be improved. Tsinghua University has developed a hydraulic ABS system suitable for light and small cars, and Beijing Institute of Technology and Shanghai Automotive Brake System Co., Ltd. have devoted themselves to the research of automotive hydraulic ABS system, and achieved initial results respectively.
The prospect of asset securitization
According to some research trends at home and abroad and the practical application of high-end cars, ABS technology will continue to develop in the following aspects:
(1)ABS and drive anti-skid control device ASR are integrated. The purpose of ABS is to prevent the wheel from locking, ASR is to prevent the wheel from slipping excessively, ABS is to relieve braking, and ASR is to apply braking. Because they are close in technology, they can fully embody their functions on low adhesion pavement, so they are organically combined.
(2) Dynamic stability control system VDC (or electronic stability control (ESP)). VDC is mainly based on ABS/ASR to solve the problem of directional stability when the car turns. ABS is organically combined with electronic full-control (or semi-control) suspension, electronic four-wheel steering, electro-hydraulic steering, electronic automatic transmission and other control systems in function and structure, so as to ensure the good dynamic stability of the automobile when driving under various harsh conditions.
(3)ABS/ASR is integrated with automatic cruise system (ACC). The purpose of automatic cruise control system (ACC) is to automatically limit the vehicle speed to a set speed when cruising, and automatically apply braking or acceleration according to driving performance, so as to keep the vehicle in front within a safe distance. When encountering obstacles, you can automatically brake and adjust the speed to a safe range. Because ABS/ASR and ACC both use the same wheel speed acquisition system, brake pressure adjusting device and engine output torque adjusting device, the integrated ABS/ASR/ACC system can not only greatly reduce the cost, but also improve the overall safety performance of the automobile.
(4) Reduce volume and weight. In order to improve the safety performance of the car, some devices are added, and the weight of the car is increased, which is not good for fuel economy. Therefore, the newly added equipment must be as light as possible under the premise of ensuring safety. In addition, whether it is a large car or a small car, the engine installation space is very compact, so the ABS controller is required to be as small as possible.
(5) With the combination of ABS and a new generation of braking systems, such as electro-hydraulic braking EHB and electromechanical braking EMB, ABS has faster response speed, better control effect and easier integration with other electronic systems. ABS will become an indispensable node in the integrated automobile chassis system.
(6) Electronic braking force distribution device (EBD) is embedded in ABS system to form ABS+EBD system. The function of EBD is to calculate the adhesion between the four tires and the road surface at high speed before ABS starts to adjust the braking pressure, and then adjust the area and adhesion between the wheels, so as to further improve the directional stability of the vehicle when braking and shorten the braking distance as much as possible.
(7) The Vehicle Speed Recorder (VSR), also known as the car black box, is an extension of the ABS system. By collecting the wheel speed signals of four wheels in real time, the device reproduces the actual running track of the car and the driver's operation of the car when the traffic accident occurs, which is convenient for the public security traffic management department to accurately judge the accident responsibility.
Mastering ABS core technology is not only very necessary but also far-reaching, which can effectively promote the modernization process of China's automobile industry.