In a four-wheel drive vehicle, all four wheels may slip, and the speed reference of ABS system cannot be measured by tire speed sensor. The acceleration and deceleration information comes from the longitudinal accelerometer, which can be an independent sensor, a PCB mounting component integrated in the ABS controller or a separate sensor group. Usually, the measuring range of accelerometer is 1g to 2g; With the change of temperature and time, the compensation stability is greater than100 mg; The frequency range is usually 50Hz. Products applicable to this system: sca320sca620sca610sca220 (module), etc.
[repost ]ABS system and working principle The braking performance is one of the main performances of a car, which is related to driving safety (a little nonsense, but how many people really paid attention to this when buying a car, especially some small-displacement cars). The most basic indexes for evaluating automobile braking performance are braking acceleration, braking distance, braking time and directional stability during braking. History of ABS(anti-ilock Brake System): The design idea of braking force adjusting device was put forward in the late 1920s, when someone obtained a patent in this field (I don't know exactly who). In 1950s, ABS, the world's first anti-lock braking system, came out at 1950, and was first applied to aircraft in aviation field. The anti-lock braking device (ABS) of Knohl Company (located in Munich, the largest company famous for producing braking systems in the world) began to be used on trains. At that time, the purely mechanical test receiving and recording device could not meet the higher requirements of automobile technology, so the effect of ABS was not very good at that time. After a lot of experimental research, it is finally concluded that "the sensor for detecting wheel speed and the controller for adjusting wheel speed are essential to achieve the goal", which is an important theoretical basis for developing ABS system for vehicles! In 1970s, Mercedes-Benz began to imagine and announced in newspapers that it would use electronically controlled ABS in cars, trucks and buses, but there were no mature mass-produced products. 1978, Mercedes-Benz installed ABS on S-class luxury cars for the first time. 1984 equipped ABS in batches on S-class cars, SL-class cars and 190E gasoline injection vehicles. From 1992 to June 10, ABS has been the basic equipment of all kinds of cars in Germany. At present, the latest ABS has developed to the fifth generation. Today's ABS has many functions, such as: 1, Electronic Traction System (ETS). 2. Drive the anti-skid adjustment device (ASR) 3. Electronic stability program 4. The classification of ABS for auxiliary braking first: according to mechanical and electronic classification, there are the following differences between them: 1. Electronic ABS is designed according to different models, and its installation requires professional technology. If you switch to another car, you must change the circuit design and battery capacity, which is not universal; Mechanical ABS is multifunctional, can be used in any vehicle with hydraulic braking device, and can be changed from one vehicle to another, and the installation only takes 30 minutes. 2. Electronic ABS is bulky, so the finished car may not have enough space to install electronic ABS. In contrast, mechanical ABS is small in size and takes up less space. 3. The electronic ABS starts to work at the moment when the wheel is locked, and it works 6~ 12 times per second; Mechanical ABS starts to work when braking, and it can move 60- 120 times per second according to different vehicle speeds. 4. The cost of electronic ABS is higher. In contrast, it is more economical and practical to use mechanical ABS. According to the classification of control channels, there are the following types: four-channel type, characterized by high utilization rate of adhesion coefficient and maximum utilization of the maximum adhesion of each wheel during braking. However, if the adhesion coefficient between the left and right wheels of a car is quite different (for example, there is water or ice on the road surface), it will affect the braking direction stability of the car. Guangzhou Honda uses a four-channel ABS device. Three-channel type, features: the car has good directional stability when braking under various working conditions. Three-channel ABS is widely used in automobiles. Dual-channel ABS, features: dual-channel ABS is difficult to give consideration to directional stability, steering controllability, braking efficiency and other aspects. At present, single-channel ABS is seldom used and has the characteristics of simple structure and low cost. , widely used in light trucks. The basic composition of anti-lock braking system: ABS usually consists of wheel speed sensor, brake pressure regulator, electronic control device and ABS warning light. In different ABS systems, the structure and working principle of the brake pressure regulator 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 will only adjust the anti-lock braking pressure of wheels that are easy to lock up when braking when the vehicle speed exceeds a certain value (such as 5km/h or 8km/h). (2) In the braking process, ABS will adjust the braking pressure of the wheel that tends to lock up only when the controlled wheel tends to lock up. When the controlled wheel is not locked, the braking process is exactly the same as that of the conventional braking system. (3) ABS has self-diagnosis function, which can monitor the working condition of the system. Once a fault affecting the normal operation of the system is found, the ABS will automatically turn off and the ABS warning light will turn on to send a warning signal to the driver. The automobile braking system can still brake like the traditional braking system. Usage characteristics of ABS: 1. When braking on the road with low adhesion coefficient, you should press the brake pedal with one foot. You can stop in the shortest braking distance. 3. The car has high directional stability when braking. In the end, no matter how good the safety equipment is, it can't compare with careful driving and superb driving skills! So don't be too superstitious about these devices, life is precious!