During the driving process of a car, it is inevitable to encounter various driving conditions, such as driving on urban roads and often encountering intersections. At this time, the driver needs to brake or even stop according to the traffic signal lights. In addition, when encountering sudden deceleration or merging vehicles entering the front, braking is necessary. Of course, when driving on highway sections and encountering steep downhills, appropriate braking operations should also be taken. So for cars, it is very necessary to have a safe, stable, and well controlled braking system.
The braking system of a car is also known as the braking system, and its working condition directly affects the driving safety of the car. A large part of the car rear end accidents and car collisions and hitches that are often encountered on the road are closely related to the reduced efficiency of the braking system. Even serious accidents such as car rollovers are caused by the poor stability of the braking system.
In order to improve the stability of the car during braking, the anti lock braking system gradually entered the car. This system improves the stability during braking by controlling the percentage of longitudinal sliding and rolling of the wheels during the braking process, and has been widely used in various vehicles.
With the rapid development of the automotive industry and the increasing number of highways year by year, people are paying more and more attention to the driving safety of automobiles. In order to improve the stability and reasonable distribution of braking force during the braking process of automobiles, the anti lock braking system has been increasingly used in various vehicles, and in recent years, this system has also become increasingly mature. The anti lock braking system belongs to the active safety equipment of automobiles. When the automobile encounters emergency braking during normal driving, this system intervenes in the braking process. Based on changes in wheel speed, the braking force is changed to intervene in the braking state, improve braking stability, and prevent traffic accidents.
1、 Current research status of anti lock braking systems for automobiles
The anti lock braking system for automobiles, abbreviated as ABS (Anti lock Braking System), was developed earlier in foreign countries. In 1936, Bosch Corporation in Germany successfully developed ABS with electromagnetic induction wheel speed sensors. After the 1960s, the development of electronic technology led to the gradual maturity of ABS technology and mass production and installation. In 1978, Bosch successfully developed a digital electronic controlled ABS system, which greatly improved the stability of cars during braking. After entering the 1990s, ABS became increasingly mature, with continuously improved control functions and greatly improved control accuracy. Nowadays, developed countries have widely adopted ABS technology, and the ABS device has become one of the necessary equipment for cars. The ABS equipment rate on various types of cars in many European and American countries is as high as 90% or more.
The research on ABS systems in China started relatively late, but significant progress has been made so far. Especially in terms of pneumatic ABS, domestic enterprises have already achieved a certain production scale. This has epoch-making significance for revitalizing China's automotive industry, marking a solid step forward in the research level of China's ABS system. In the research of hydraulic ABS system, many technical problems have been encountered, making it difficult to tackle them. Therefore, it is not yet possible to independently produce, but it also has a certain degree of independent research and development capabilities. We look forward to achieving breakthroughs as soon as possible and forming mass production.
2、 The Structure and Function of Automotive Anti lock Braking System
The braking system of a car, as an active safety component, has received much attention for its safety performance. If a car is not equipped with an ABS system, when it encounters various braking conditions during driving, the wheels may lock up, meaning that the contact point between the wheels and the ground does not change, does not roll at all, and is in a constantly sliding state. This is very dangerous. Not only will the wear and tear of the wheels worsen, but in severe cases, it can also cause traffic accidents. Moreover, due to changes in braking efficiency, various problems may arise: firstly, the front wheels lock up and the rear wheels roll, which can cause the car to lose its steering ability; The second is that the rear wheels lock up and the front wheels roll, which can cause the car to jerk and shake its tail; The third issue is that one side of the wheel locks and the other side rolls, causing slight side slip and, in severe cases, possible rollover.
The automobile anti lock braking system is to prevent the wheels from being locked by braking during the automobile braking process, improve the braking deceleration, effectively improve the Directional stability and steering maneuverability of the automobile, and ensure the driving safety of the automobile. Its impact on car performance is mainly reflected in reducing braking distance, maintaining steering control ability during braking, improving driving direction stability, and reducing tire wear.
The anti lock braking system of automobiles mainly consists of three parts: wheel speed sensor, brake pressure regulator, and electronic control unit (ECU). The wheel speed sensor is mainly used to continuously monitor the rotational speed of the wheels during the braking process of the car. The electronic control unit is mainly used to receive signals and issue commands, and the brake pressure regulator is mainly used to adjust the current brake pressure on the wheels. Each wheel of the car has an independent wheel speed sensor that constantly monitors the current wheel speed during the braking process and continuously transmits it to the electronic control unit. When one of the wheels experiences a rapid increase in deceleration due to excessive braking force, and the wheel speed drops sharply beyond the set value, which means there is a possibility of lock up, the electronic control unit will issue a command to the brake pressure regulator to stop or reduce the braking pressure of the wheels, causing the wheels to start spinning, i.e. sliding while rolling, which will prevent wheel lock up from occurring. At the same time, in order to prevent insufficient wheel braking force, it is necessary to increase the braking pressure again. Throughout the entire braking control process, it is necessary to continuously measure whether the wheel movement is stable. By adjusting the braking pressure, the braking force should be continuously pressurized, depressurized, and maintained based on the current vehicle speed and the possibility of wheel lockup, so that the wheels can maintain maximum braking force while not being locked. The specific control process is as follows:
Pressure maintaining process: During the braking process, if a certain wheel tends to lock, the ECU in the ABS sends a command to control the brake pressure to remain constant and not increase, while the braking force of other wheels that do not tend to lock continues to increase.
Pressure reducing process: When the braking pressure of the wheel is maintained at a certain level, the ECU determines that the wheel is still tending to lock, and the ECU in ABS sends a command to control the rapid reduction of braking force.
Pressurization process: As the braking pressure of the wheel decreases, the wheel will gradually accelerate and completely eliminate the trend of lockup. When the ECU in ABS issues a command to control the rapid increase of braking force, and the wheel begins to decelerate.
3、 The Development Trend of Automotive Anti lock Braking Systems
In recent years, the development of electrical intelligence in automobiles has made significant progress. As a part of the electronic control system in cars, the development of ABS is also evident.
1. Multi channel development: From the initial single channel and two channel ABS systems, it has now evolved to three channel and four channel ABS systems. The number of channels directly determines the effectiveness of independent brake pressure regulation. Taking the four channel ABS system as an example, this arrangement can independently control the slip state of all four wheels within the optimal range, fully utilizing the adhesion of each wheel to achieve high braking efficiency. Whether the adhesion conditions on the road surface where the left and right wheels are located are similar or there is a significant deviation in adhesion conditions, independent control of each channel can enable the four wheels to undergo completely independent brake pressure regulation during braking, greatly improving driving stability.
2. Integrated development: With the advancement of automotive electrification, various electronic control systems are gradually emerging, and the ASR system related to ABS is one of them. The ASR system, also known as the drive anti slip system. ABS is to prevent wheel lockup, while ASR is to prevent excessive wheel slip. ABS is to release the brake, and ASR is to apply the brake. The two complement each other and can effectively combine and integrate the development, further improving driving safety.
3. Integrated development: The role of ABS is to prevent the wheels from locking when braking. Today, the ABS system is integrated with the electronic brake force distribution system (EBD), forming the ABS+EBD system. Before ABS starts to adjust the brake pressure, calculate the adhesion between the four wheels of the car and the road surface, and then adjust the distribution of the wheel and the adhesion, which can better improve the Directional stability when braking and shorten the braking distance.