ABS (automatic anti-lock braking system) can be said to be the three most important inventions in the history of driving safety (the other two are airbags and seat belts). ABS is also one of the other safety devices (such as ESP driving Dynamic stability system and EBD braking force distribution system). This year marks the 25th anniversary of the birth of the ABS system. In the past twenty-five years, the ABS system has saved the lives of nearly 15,000 North American drivers. Let us take this opportunity to review the development of the ABS system and its impact on the automotive industry
2004 This year marks the 25th anniversary of the birth of the first mass-produced civilian ABS (Antilock Braking System) in history. Over the past quarter of a century, ABS systems have not only continued to improve and improve, but have also helped many car owners escape from death. In addition to introducing the great contributions of the ABS system over the past 25 years, we also want to review the development history of ABS.
The principle of "automatic anti-lock braking" is not difficult to understand. In the event of an emergency, a vehicle that is not equipped with an ABS system has no time to brake slowly in stages and can only be trampled to death immediately. Due to the inertia of the vehicle's sprint, dangerous situations such as sideslip, driving trajectory deviation, and uncontrolled vehicle direction may occur in an instant! When the wheels of a vehicle equipped with an ABS system are about to reach the critical point of locking, the brakes can be applied 60 to 120 times in one second, which is equivalent to constantly braking and relaxing, which is similar to the "point braking" action of mechanical automation. This can avoid directional control and wheel sideslip during emergency braking, and at the same time increase tire friction, making the braking efficiency reach more than 90%.
From a microscopic analysis, the friction between the tire and the ground reaches its maximum at the critical point when the tire changes from rolling to sliding. When the car starts, the engine power output can be fully utilized (shortening the acceleration time), and when braking, the deceleration effect is greatest (the braking distance is the shortest). The controller in the ABS system uses a hydraulic device to control the brake pressure to repeatedly swing at the critical point where the tire slips, so that the brake disc continuously repeats the process of contact and separation while keeping the tire grip closest to the maximum theoretical value to achieve the best braking effect.
The operating principle of ABS seems simple, but the process from scratch has experienced many setbacks (lack of key technologies)! In 1908, British engineer J. E. Francis proposed the theory of "wheel locking and sliding controller for railway vehicles", but was unable to put it into practice. Over the next 30 years, attempts including Karl Wessel's "brake force controller", Werner Mhl's "hydraulic brake safety device" and Richard Trappe's "wheel lock preventer" all failed. In the "Automotive Technology Handbook" published in 1941, he wrote: "Up to now, any attempt to prevent the danger of wheel locking through mechanical devices has not yet been successful. The day this device succeeds will be a milestone in the history of traffic safety. "An important milestone". Unfortunately, the author of the book probably did not expect that this day would have to wait another 30 years.
What was the technical bottleneck in developing anti-lock braking devices at that time? First of all, the device requires a system to monitor tire speed changes in real time and immediately adjust the brake pressure through the hydraulic system. In that era without integrated circuits and computers, no mechanical device could achieve such a swift response! By the time the birth of the ABS system showed its glimmer of light, it was already the early 1960s when semiconductor technology had reached its initial scale.
The origin of the ABS system developed by Bosch, a German company that specializes in automotive electronic systems, can be traced back to 1936, when Bosch applied for a patent for a "motor vehicle anti-brake locking device".
In 1964 (also the year when integrated circuits were born) Bosch started the ABS research and development plan again, and finally came to the conclusion that "it is feasible to prevent wheel locking through electronic device control". This is the term ABS (Antilock Braking System) in history. Appeared for the first time! The world's first ABS prototype appeared in 1966, proving to the world that "shortening the braking distance" is not an impossible task. Because the investment was too huge, the initial application of ABS was limited to railway vehicles or aircraft. Teldix GmbH cooperated with Mercedes-Benz in 1970 to develop the first prototype for road vehicles, ABS 1. This system has the basis for mass production, but its reliability is insufficient, and there are more than 1,000 components in the control unit. Not only is the cost too high, it is also prone to failure.
In 1973, Bosch purchased 50% of the equity of Teldix GmbH and its research and development results in the ABS field. In 1975, AEG, Teldix and Bosch reached an agreement to completely entrust Bosch with the development plan of the ABS system for integration and execution. "ABS 2" was born after 3 years of hard work! Different from ABS 1, which uses analog electronic components, the ABS 2 system is completely designed with digital components. Not only does the number of components in the control unit drop sharply from 1,000 to 140, but it also reduces costs, greatly improves reliability, and significantly improves computing speed. Three major advantages of acceleration. Two German car manufacturers, Mercedes-Benz and BMW, decided to install ABS 2, a high-tech system, on their S-Class and 7 Series models at the end of 1978.
In the first three years of its existence, the ABS system suffered from the high cost and was unable to develop the market. From 1978 to the end of 1980, Bosch sold only 24,000 ABS systems. Fortunately, the number grew to 76,000 units in the second year. Receiving positive response from the market, Bosch started the research and development plan of TCS tracking control system. The weight of the ABS 2S system launched in 1983 was reduced from 5.5 kg to 4.3 kg, and the number of control components was reduced to 70. By the mid-1985s, the proportion of ABS systems installed on newly manufactured vehicles worldwide exceeded 1% for the first time, and General Motors also decided to make ABS a standard feature of its main Chevrolet models.
1986 was another memorable year. In addition to Bosch celebrating the sale of its 1 millionth ABS system, more importantly, Bosch launched the first TCS/ASR cycler for civilian vehicles. trace control system. The function of TCS/ASR is to prevent the driving wheels from slipping during starting and accelerating the car, especially to prevent the driving wheels from spinning when the vehicle is cornering, and to control the slipping within the range of 10% to 20%. Since ASR is controlled by adjusting the torque of the driving wheels, it is also called the driving force control system, and is also called TRC or TRAC in Japan.
There are many similarities in the working principles of ASR and ABS. The combined use of the two can achieve better results, forming an anti-wheel lock and drive wheel anti-skid control (ABS/ASR) system. This system mainly consists of wheel speed sensor, ABS/ASR ECU controller, ABS driver, ASR driver, auxiliary throttle controller and main and auxiliary throttle position sensors. When the car starts, accelerates and travels, the engine ECU will enter the anti-idling program based on the signal input by the wheel speed sensor. First, the engine ECU lowers the auxiliary throttle to reduce the amount of fuel intake, thereby reducing the engine power output torque. When the ECU determines that the driving wheel needs to be intervened, it will send a signal to the ASR driver to control the driving wheel (usually the front wheel) to prevent the driving wheel from slipping or keep the driving wheel from slipping within a safe range. The first new model equipped with an ASR system appeared in 1987, and the Mercedes-Benz S-Class once again became the maker of history.
As the unit price of ABS systems gradually decreased, the number of new cars equipped with ABS systems broke through the critical point of explosive growth in 1988 and began to grow rapidly. That year, Bosch's annual sales of ABS systems exceeded 3 million units for the first time. . A technological breakthrough allowed Bosch to launch the ABS 2E system in 1989. For the first time, the design that was originally separated in the engine room (hydraulic drive component) and the center console (electronic control component) and had to rely on complex wiring connections was changed to a "two-component integration" "Designed for One"! The ABS 2E system is also the first ABS system in history to abandon integrated circuits and use a microprocessor (CPU) with an 8 kbyte computing speed to be responsible for all control work, once again writing a new milestone. That year, Porsche officially announced that all car series had been equipped with ABS. Three years later (1992), Mercedes-Benz also decided to follow Porsche's footsteps.
In the first half of the 1990s, ABS systems gradually became popular in mass-produced cars. Bosch launched an improved version of ABS 2E in 1993: the ABS 5.0 system. In addition to being smaller and lighter, ABS 5.0 was equipped with a processor that doubled the computing speed (16 kbytes). The company also celebrated in the middle of the same year The 10 millionth ABS system sold.
ABS and ASR/TCS systems have been recognized by car owners around the world, but Bosch’s engineering team is not satisfied. Instead, it sets a more challenging goal: ESP (Electronic Stabilty Program, driving dynamics) Stable system) Forward! Unlike ABS and TCS which can only increase stability during braking and acceleration, ESP can maintain the vehicle's optimal dynamic balance and driving route at any time during driving. The ESP system includes a steering sensor (monitors the steering wheel rotation angle to determine whether the car is traveling in the correct direction), a wheel sensor (monitors the speed of each wheel to determine whether the wheel is slipping), and a sway speed sensor (records the car's movement around the vertical axis to determine whether the car is slipping). Loss of control) and lateral acceleration sensor (measuring the centrifugal acceleration when cornering to determine whether the car loses grip when cornering). At the same time, the control unit uses the data from these sensors to judge the vehicle's operating status, and then indicates an or The brake pressure on multiple wheels is established or released while the engine torque is adjusted with the most precise precision, in some cases even as many as 150 times per second. ESP that integrates ABS, EBD, EDL, ASR and other systems allows car owners to focus on driving while letting the computer easily cope with various emergencies.
Continuing the past practice when ABS and ASR were born, the Mercedes-Benz S-Class was the first model to use the ESP system (in 1995). Four years later, Mercedes-Benz officially announced that all car series would include ESP as standard equipment. At the same time, the ABS 5.7 and ABS 8.0 systems launched by Bosch in 1998 and 2001 are still striving for excellence. The total weight of the entire system has been reduced from 2.5 kilograms to 1.6 kilograms, and the processor's computing speed has been upgraded from 48 kbytes to 128 kbytes. Mercedes-Benz's main competitors, BMW and Audi, also announced in 2001 that all car series would include ESP as standard equipment. The Bosch car factory celebrated the sale of more than 100 million ABS systems and 10 million ESP systems in 2003. According to a survey by ACEA (European Automobile Manufacturers Association), every new car produced in continental Europe today is equipped with an ABS system. More than 60% of new cars in the world have this device.
"The ABS system greatly improves braking stability and shortens the distance required for braking," said Wolfgang Drees, member of the board of directors of Robert Bosch GmbH (the full name of the company Bosch).
Unlike airbags and seat belts (which can be analyzed by dividing the number of deaths by the number of car accidents), the ABS system, which is a "nip in the bud" system, is difficult to prove with real data. How many people will it save from death? However, according to a study by the German Insurance Association and the Automobile Safety Society that analyzed the causes of serious casualty traffic accidents, 60% of fatal traffic accidents were caused by side collisions, and 30 to 40% were caused by speeding, sudden turns or improper operation. of. We have reason to believe that ABS and its derived ASR and ESP systems can significantly reduce the chance of a vehicle losing control in an emergency. NHTSA (North American Highway Safety Administration) once estimated that the ABS system saved the lives of 14,563 North American drivers!
From ABS to ESP, automotive engineers’ efforts to improve driving stability seem to have reached their limit (it has been nearly 10 years since the civilian ESP system was born), but no matter how advanced the computer is, it still requires proper operation by the driver. in order to achieve maximum effectiveness. At the end of the article, we tell you how to make good use of the ABS system?
Most car owners have never encountered an emergency (and hope they never will), but they have to know how to deal with critical moments? When you step on the brakes in an emergency, the brake cylinder of the ABS system will activate quickly, and the brake pedal will immediately produce abnormal vibrations and significant noise (normal phenomena in the operation of the ABS system). At this time, you should not hesitate to apply the brakes hard. (Unless the car has an EBD brake force assist device, most drivers have insufficient braking force.) In addition, ABS can prevent wheel locking during emergency braking, so the front wheels can still control the direction of the vehicle body. Drivers should brake and steer for emergency avoidance. For example, to avoid obstacles on the road to the left, they should depress the brake pedal vigorously, quickly turn the steering wheel 90 degrees to the left, turn the wheel 180 degrees to the right, and finally turn the wheel again. Go back 90 degrees to the left. The last thing to mention is that the ABS system relies on sophisticated wheel speed sensors to determine whether locking has occurred? The sensors on each wheel should always be kept clean to prevent mud, oil, and especially magnetic substances from adhering to their surfaces. These may cause the sensors to fail or input erroneous signals and affect the normal operation of the ABS system. Before driving, you should always pay attention to the ABS fault indicator light on the dashboard. If it flashes or stays on, the ABS system may have failed (especially the early system), and you should go to a repair shop to troubleshoot as soon as possible.
Finally, I would like to remind readers that although the ABS/ASR/ESP system is the crystallization of high technology, it is not omnipotent, and do not drive fast just because of these active driving safety systems. ABS has indeed saved the lives of many drivers in the past, but it cannot guarantee that every driver will be saved from danger, right?
There is also some information about ABS, which is shared as follows:
At present, the latest ABS has developed to the 5th generation (some information says it is the 8th generation, I don’t know whether it is true or not). Today's ABS has also derived other electronic control systems, such as:
1. Electronic Traction System (ETC).
2. Electronic Stability Program (ESP)
3. Auxiliary Brake (BA)
(Note: Each manufacturer has different names for the above systems. But the principle is the same, and most ESP systems are from Bosch)
Let’s talk about the classification of ABS:
According to mechanical and electronic classification, the two have the following differences:
1. Electronic ABS is designed according to different car models. Its installation requires professional skills. If it is installed on another vehicle, its circuit design and battery capacity must be changed. It has no versatility; mechanical ABS is highly versatile and can be used on any vehicle with a hydraulic brake device. It can be installed from one vehicle to another, and installation only takes 30 minutes.
2. Electronic ABS is large in size, and the finished vehicle may not have enough space to install electronic ABS. In contrast, mechanical ABS is smaller in size and takes up less space.
3. Electronic ABS starts working when the wheels are locked, and works 6 to 12 times per second; mechanical ABS starts working when the brakes are applied, and works every second depending on the vehicle speed. Can be used 60-120 times.
4. The cost of electronic ABS is higher. In comparison, using mechanical ABS is more economical and practical.
According to the control channel classification, there are the following types:
Four-channel type, features: high adhesion coefficient utilization, and the maximum adhesion of each wheel can be utilized to the greatest extent during braking. Focus. However, if the adhesion coefficients of the left and right wheels of the car are greatly different (such as water or ice on the road surface), it will affect the stability of the car's braking direction. Guangzhou Honda uses a four-channel ABS device.
Three-channel type, features: The car has good directional stability when braking under various conditions. Three-channel ABS is commonly used in cars.
Two-channel type, features: It is difficult for two-channel ABS to take into account all aspects of directional stability, steering control and braking performance, and is currently rarely used.
One-channel type, Features: simple structure, low cost, etc., widely used in light trucks.
The basic components of the anti-lock braking system:
ABS usually consists of a wheel speed sensor, a brake pressure regulator, an electronic control device and an ABS warning light. In the ABS system, the structural form and working principle of the brake pressure regulating device are often different, and the internal structure and control logic of the electronic control device may also be different.
All kinds of ABS are the same in the following aspects:
(1) ABS only works after the car’s speed exceeds a certain speed (such as 5km/h or 8km/h). Anti-lock brake pressure will be adjusted for wheels that tend to lock during braking.
(2) During the braking process, only when the controlled wheel tends to lock, ABS will perform anti-lock adjustment on the braking pressure of the wheel that tends to lock; when the controlled wheel When it is not locked, the braking process is exactly the same as that of a conventional braking system
(3) ABS has a self-diagnostic function and can monitor the working conditions of the system. When there is a fault that affects the normal operation of the system, the ABS will be automatically turned off and the ABS warning light will be illuminated to send a warning signal to the driver. The car's braking system can still brake like a conventional braking system.
ABS usage characteristics:
1. When braking on a road with low adhesion coefficient, the brake pedal should be pressed with one foot
2. It can Stop within the shortest braking distance
3. The car has high directional stability when braking