2004 is the 25th anniversary of the birth of the first mass-produced civil ABS (anti-lock braking system, automatic anti-lock braking system). In the past quarter century, ABS system has not only made continuous progress, but also made many car owners escape from the gates of hell. In addition to introducing the ABS system that has made great contributions in the past 25 years, we also need to review the history of ABS. Principle of "automatic anti-lock braking"
It is not difficult to understand that in an emergency, there is no ABS system installed in the car when it is too late to brake. Because of the inertia of the vehicle dashboard, sliding can happen instantly, and the deviation between the driving direction and the vehicle body trajectory is uncontrolled and dangerous! When the vehicle that is about to reach the critical point with wheel lock is equipped with ABS system, the braking can be applied for 60 to 120 times as much as the second time, which is equivalent to keeping the braking and relaxing, which is similar to the mechanical automation "pumping" effect. This can avoid emergency braking, control the wheel slip direction, increase the tire friction, and make the braking efficiency exceed 90%.
Microscopically, when the tire rolls to the critical point between the tire and the maximum sliding friction. Start to give full play to the power output of the engine in the car (shorten the acceleration time), if the braking effect of deceleration is the greatest (the braking distance is the shortest). When the controller of ABS hydraulic unit control system repeatedly swings the critical point of tire slip by using braking pressure, it can leave the grip closest to the tire and maintain the maximum theoretical value during repeated contact, thus achieving the best braking effect.
operate
The ABS principle seems simple, but it has experienced many setbacks from scratch (lack of key technology)! 1908 British engineer je Francis put forward the theory of "wheel slip controller for railway vehicles", but it is not practical. In the next 30 years, attempts including Karl wessel's Brake Force Controller, Werner ·MHL's Hydraulic Brake Safety Device and Richard trapp's Wheel Lock Prevention all failed. The Automotive Technical Manual published by 194 1 wrote: "So far, any attempt to prevent the danger of wheels by mechanical devices has not been successful. In the history of success, this day is a very important milestone in installing traffic safety equipment. " Unfortunately, I'm afraid I didn't expect this day to wait for 30 years.
What is the bottleneck of anti-lock braking system technology development? First of all, it is necessary to monitor the tire transmission system in real time and adjust the size of the brake hydraulic system in real time. In the era when there is no integrated computer, there is no need for any mechanical device to achieve such a rapid response! Until the birth of ABS system, there was a glimmer of hope, and semiconductor technology had a preliminary scale in the early 1960 s.
The history of developing ABS system by Bosch Company, which specializes in automotive electronic systems, can be traced back to 1936, when Bosch Company applied for the patent of "Automotive Brake System, Anti-lock Device". 1964 (also the year when the integrated circuit was born), restarted the research and development plan of Bosch ABS company, and finally reached the conclusion that it is feasible to prevent the wheel from locking through electronic device control. This is the first time in history that the term ABS (Anti-lock Brake System) appears! The first prototype car in the world adopted ABS in 1966, so it is impossible to shorten the braking distance. Due to excessive capital investment, the application is limited to the original ABS rail vehicles or aircraft. In 1970 * *, Teldix Co., Ltd. developed the first prototype of Mercedes-Benz factory road car-ABS1. The system has a production base, but the control elements in the unit lack reliability, exceeding 1000, which is not only costly, but also prone to failure.
1973, Bosch bought 50% of the shares. 1975 ABS developed by AEG Teldix Co., Ltd. in this field reached an agreement with Bosch Teldix to entrust the ABS system scheme developed by Bosch with full authority. After three years of hard work, ABS 2 was born! Unlike ABS 1 analog electronic components, ABS 2 system is a completely digital component. Not only is the number of components to be controlled reduced from 1000 to 140, but it also has three main advantages: lower cost, greatly increased reliability and faster operation. At the end of 1978, Mercedes-Benz and BMW confirmed the high-tech S-class 2 equipment and 7 series cars of ABS.
In the first three years of life, the cost of ABS system was too high, and it did not suffer from market development. From 1978 to 1980, Bosch only sold 24,000 ABS systems. Fortunately, there were 76,000 units in the second year of growth. Through positive market response, Bosch started the research and development plan of TCS traction control system. The ABS 2S system introduced by 1983 is reduced to 5.5 kg, the weight is 4.3 kg, and the control module is also reduced to 70 kg. By the middle of 1985, the proportion of ABS systems installed for the first time in new automobile factories around the world exceeded 1%, and GM also decided to equip Chevrolet cars with its main ABS as standard.
1986 is another memorable year. In addition to celebrating Bosch's sale of 1 10,000 ABS systems, more importantly, Bosch introduced the first TCS and civil/ASR traction control systems for automobiles. The function of TCS/ASR is to prevent the wheel from slipping when the car is accelerating, especially to prevent the wheel from idling when cornering, and to control the slip within the range of 10% to 20%. Because ASR is controlled by adjusting the torque of the driving wheel, the driving force control system is also called TRC or TRAC in Japan.
There are many similarities between the working principles of ASR and ABS, and the combination of the two forms a better effect, which constitutes the wheel and wheel lock prevention and anti-skid control (ABS/ASR) system. The system consists of wheel speed sensor, ABS/ASR ECU controller, ABS driver, ASR driver, controller, auxiliary throttle position sensor and so on. In the process of automobile starting, accelerating and moving, based on the input signal of wheel speed sensor, when it is judged that the driving wheel slips beyond the upper limit, the engine ECU enters the air defense program in turn. The first engine ECU lowers the throttle to reduce the engine torque and reduce the power output. When ECU determines that it is necessary to intervene in the driving wheel, it sends a signal to the control of ASR (usually the front wheel) of the driving wheel to prevent the wheel of the driving wheel from slipping or keep it unchanged within a safe range. The first new model equipped with ASR system appeared in 1987, and Mercedes-Benz S-Class sedan once again became the creator of history.
With the price reduction of ABS system and the equipment of ABS system, the number of new cars broke out at the critical point of 1988 and began to grow rapidly. Bosch's annual sales of ABS system exceeded 3 million sets for the first time this year. The technical breakthrough enabled Bosch to launch the first ABS 2E system at 1989. At first, it was isolated from the engine compartment (hydraulic drive part) and the console (electronic control unit), so the wiring had to be changed to the design of "integrating these two parts together is one"! The ABS 2E system was also abandoned, and the history of the first integrated circuit was replaced by the speed of a microprocessor (CPU) with 8 kilobytes of calculation, which once again marked a new milestone. The automobile factory officially announced that a Porsche car has been installed with ABS. Three years later (1992), Mercedes-Benz Porsche Automobile Factory also decided to keep pace with the times.
In 1990s, half of ABS systems gradually began to be popularized in production cars. The improved version 2E of Bosch ABS was launched in 1993: ABS 5.0 system. In addition to being smaller and lighter, it is also a processor with twice the operation speed (16 K bytes). The company also celebrates the100000 ABS system sold every year.
ABS and ASR/TCS systems have been recognized as car owners in the world, but Bosch's engineering team is not satisfied, but is moving towards the next more challenging goal: ESP (Electronic Stability Plan, Driving Dynamic Stability System)! Unlike ABS and TCS, which can only increase the stability of braking and acceleration, ESP can keep the dynamic balance of the vehicle in the best route at any time. ESP system includes steering sensor (monitoring the steering wheel angle to ensure that the vehicle is traveling in the right direction), wheel sensor (monitoring each wheel to determine the speed slip of the wheel), yaw rate sensor (the surrounding vertical axis is shooting a dynamic car to determine whether the car is out of control) and lateral acceleration sensor (centrifugal acceleration measured when turning to determine whether the vehicle loses grip). At the same time, the data from these sensors can be used to judge whether the control unit is in the running state of the vehicle, so as to indicate the establishment or release of the braking pressure of one or more wheels, and at the same time adjust the torque of the engine to the most accurate, and even reach the response of 150 times per second in some cases. Integrated ABS, EBD, EDL and ASR systems, such as ESP, enable car owners to concentrate on driving and allow computers to easily deal with various emergencies.
The birth of ABS and ASR in the past
Continuing, Mercedes-Benz S-Class took the lead in using the ESP system (1995). Four years later, Mercedes-Benz officially announced that ESP will be standard in the whole car series. At the same time, Bosch introduced ABS 5.7 in 1998 and 200 1 year, and the ABS 8.0 system is still good. The total weight of the whole system is upgraded from 2.5 kg to 1.6 kg, and the running speed is upgraded from 48 kilobytes processor to 128 kilobytes. In 2006, Mercedes-Benz's main competitors were BMW and Audi. In 2003, Bosch sold more than10,000 ABS ESP systems and more than 654.38 million ABS ESP systems. According to the survey of ACEA (European Automobile Manufacturers Association), every European continent now produces new cars equipped with ABS system, and more than 60% of all new cars in the world have this equipment.
Wolfgang Driss, a member of the board of directors of robert bosch Co., Ltd. (full name Bosch), said: "ABS braking system greatly improves the stability and shortens the braking distance. Unlike airbags and seat belts (the ratio of the number of car accidents can be divided by the number of deaths), it is more difficult to get many people back from ABS system to "prevent" hell. However, according to the research of German Insurance Association, the analysis of serious injuries caused by safety cars shows that 60%, 30% and 40% of the deaths caused by side traffic accidents are caused by speeding, sudden turning or improper operation. We have reason to believe that ABS, ASR and ESP systems are due to the significant reduction in the incidence of out-of-control vehicles in emergencies. The National Highway Traffic Safety Administration (Northern Highway Traffic Safety Administration) estimates that the ABS system saved 65,438+04,563 drivers living in North America!
From ABS to ESP, it seems that the efforts of automobile engineers to improve driving stability have reached the limit (the civil ESP system established nearly 10 years ago), but even the most advanced computers still need proper driver operation to achieve the maximum effect. At the end of the article, we will tell you how to use ABS system.
Most car owners have never encountered an emergency (I hope never), but they don't know how to deal with the critical moment. During emergency braking, for the fast-moving ABS brake cylinder system, the brake pedal has obvious abnormal vibration and noise (a normal phenomenon in the operation of the ABS system). You should not hesitate to forcibly brake (unless the vehicle has EBD braking force auxiliary device and the braking force driver program is not enough). ABS prevents the emergency braking from locking the wheel, so the direction of the front wheel can still be controlled. Drivers should avoid danger urgently and apply side brakes to avoid obstacles on the left side of the road. For example, he has to step on the brake pedal hard, turn the steering wheel 90 degrees left and right, turn the wheels 180 degrees, and finally turn left 90 degrees. Finally, the ABS system relies on the accurate wheel speed sensor to judge whether there is locking. Usually, it is necessary to keep each wheel sensor clean to prevent dust, oil stains, especially magnetic materials from adhering to the surface, which may lead to sensor failure or input wrong signals and affect the normal work of ABS system. Always pay attention to the flashing or long-term discovery of ABS fault indicator light on the dashboard before driving. The ABS system may be faulty (especially the early system), so repair it before leaving the factory as soon as possible to eliminate the fault.
Finally, readers should be reminded of ABS/ASR/ESP systems, but because of these active safety systems, they should not be the high-tech crystallization of speeding traffic, but they are not omnipotent. ABS did save many drivers' lives in the past, but there is no guarantee that every driver will be saved, right?
There is some information about ABS, which is shared as follows:
At present, the latest ABS has developed to the fifth generation (some people say it is the eighth generation, I don't know whether it is true or not), and today's ABS has also derived other electronic control systems, such as:
1, electronic traction system (ETC).
2. Electronic Stability Program (ESP)
3. Brake assist system
(Note: The appellation systems of different manufacturers are different, but the principle is the same, except that most ESP systems come from Bosch)
Except ABS:
According to mechanical and electronic classification, the differences between them are as follows:
1, electronic ABS is designed according to different models, and its installation requires professional technology. If it is necessary to change its circuit design and battery capacity, it is not universal. Mechanical ABS is omnipotent. As long as you can use the hydraulic braking system of the vehicle, you can change from one car to another, and it only takes 30 minutes to install.
2, a large number of electronic ABS, and the finished product may not have enough space to install electronic ABS on the car. In contrast, mechanical ABS is small in size and takes up less space.
3. Wheel lock that can be started instantly by electronic ABS action, with the function of 6 12 times per second; When braking, the mechanical ABS starts to work. Depending on the speed, the second 60% function is-120. High-ranking, higher-ranking, more important
4. The cost of electronic ABS is more economical than that of mechanical ABS.
According to the classification of control channels, there are the following:
Four channels, function: high adhesion coefficient, which can make maximum use of the maximum adhesion of each wheel. However, if the coefficients of the two wheels attached to the left and right sides of the car are quite different (such as water or ice sections), it will affect the stability of the braking direction of the car. Guangzhou Honda adopts four-channel ABS system.
Three-channel type, features: under various conditions, the car has good directional stability when braking. Three-channel ABS is widely used in automobiles.
Dual-channel function: Dual-channel ABS is difficult to control in terms of directional stability, steering and braking performance, and is rarely used at present.
A trough is characterized by simple structure and low cost, and is widely used in light trucks and vehicles.
Basic components of anti-lock braking system;
ABS wheel speed sensor usually includes brake pressure regulator, electronic control unit and ABS warning light. The structure and working principle of brake pressure regulator in different ABS systems are usually different, and the internal structure of electronic control unit and control logic circuit can also be changed.
ABS in the following aspects
The variety is the same:
(1) When the ABS vehicle exceeds a certain speed (such as 5km/h or 8km/h), the wheel lock is often adjusted by the anti-lock braking pressure when braking.
(2) Control when braking. Only when the wheel is locked, ABS tends to adjust the anti-lock braking pressure of the locked wheel; The braking process of the system is exactly the same as that of the conventional braking process when the wheel is locked after runaway chemotaxis.
(3)ABS has self-diagnosis function and can be monitored by the working system. Once it is found that it affects the normal operation of the system, it will automatically shut down. When ABS and ABS warning lights fail to remind the driver, the braking system of the car can still brake like the conventional braking system.
Characteristics of ABS application:
1, when braking, the road friction coefficient is low, so the brake pedal should be a pedal.
2, can stop with the shortest braking distance.
3. Brake when the car has high directional stability.