Foreword
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ABS is the car anti-lock brake system, which is an active safety device for cars. With the development of automotive electronics technology, the application of integrated circuits and computer technology, ABS control technology is becoming more and more mature. In foreign countries, ABS is already the standard configuration on automobiles. In recent years, ABS has also gained popularity in domestic cars. Let's talk about the control method and control principle of ABS, I hope to help you.
ABS control method
1, two-parameter control
The two-parameter controlled ABS (structure of the anti-lock braking system) consists of a vehicle speed sensor (speed radar), a wheel speed sensor, a control device (computer) and an actuator.
The working principle is the vehicle speed sensor and the wheel speed sensor. The vehicle speed and the wheel speed signal are input into the computer respectively, and the actual slip ratio is calculated by the computer, and compared with the ideal slip ratio of 15% to 20%, and then increased or decreased by the solenoid valve. Brake force of the brake.
This type of drag sensor is commonly used in Doppler speed radar. When the car is driving, the Doppler radar antenna continuously emits electromagnetic waves to the ground at a certain frequency, and at the same time receives the reflected electromagnetic waves, and measures the difference between the emission and reception of the car radar, so that the vehicle speed can be accurately calculated. The wheel speed sensor is mounted on the transmission housing and is driven by the transmission output shaft. It is a pulse motor and produces a frequency proportional to the wheel speed.
The actuator consists of a solenoid valve and a relay. The solenoid valve adjusts the braking force to maintain the desired slip ratio.
This kind of ABS can guarantee the ideal control of the slip ratio, and the anti-lock braking performance is good. However, due to the addition of a speed measuring radar, the structure is complicated and the cost is high.
2, single parameter control
It controls the wheel's angular deceleration and controls the braking force of the wheel to achieve anti-lock braking. Its structure is mainly composed of wheel speed sensor, controller (computer) and solenoid valve. In order to accurately measure the wheel speed, there should be a 1 mm gap between the sensor head and the wheel ring gear. To avoid the effects of water, mud and dust on the sensor, the sensor should be greased before installation.
Solenoid valves are used for pressure regulation of wheel brakes. For a four-channel brake system, one wheel has one solenoid valve; a three-channel brake system has one for each front wheel and one for the two rear wheels. The solenoid valve has three hydraulic holes, which are respectively connected with the brake master cylinder and the wheel brake cylinder, and can realize the pressure regulation function of pressure increase, pressure maintenance and pressure reduction. The working principle is as follows.
1) Boost When the solenoid valve is not working, the brake master cylinder interface and each brake cylinder interface are directly connected. Due to the high strength of the main spring, the inlet valve is opened and the brake pressure is increased.
2) Pressure maintenance When the pressure in the brake cylinder of the wheel increases to a certain value, the inlet valve is cut off. The bracket is kept in the middle and the three holes are sealed to each other to maintain the brake pressure.
3) Step-down When the solenoid valve is working, the bracket overcomes the spring force of the two springs, and opens the unloading meat to lower the pressure of the brake cylinder. Once the pressure is reduced, the solenoid valve switches to a pressure hold state, or a boosted ready state.
The main task of the control unit ECU is to calculate, analyze, amplify and discriminate the signals transmitted from the sensors of the respective wheels, and then output the command signals to the solenoid valves by the output stage to perform the brake pressure adjustment task. The electronic control device consists of four parts, input stage A, controller B, output stage C, voltage regulation and protection device D.
The electronic controller drives the solenoid valve at a frequency of 4 to 101 tz, which the driver cannot do. This single-parameter control mode ABS is widely used due to its simple structure and low cost.
Most of the Chrysler sedans in the United States are equipped with this single-parameter control ABS. It is equipped with wheel speed sensors on all four wheels of the car.
A 45- or 100-tooth ring gear is mounted on the wheel axle, and the sensor head of the wheel speed sensor is mounted on the top of the ring gear. When the wheel rotates, the sensor continuously generates a voltage signal, and inputs it into the computer, compares it with the ideal speed in the RoM, calculates the speed increase or deceleration of the wheel, and sends a command to boost or depressurize the solenoid valve to control the brake cylinder system. power.
Conclusion
With the rapid development of the automobile industry, the driving safety of automobiles has been paid more and more attention by people. The advent of ABS has greatly improved the performance of automobile brake systems, and ABS has gradually become the standard configuration of automobiles. Understanding the control methods of ABS is very helpful for people to drive safely.
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