Application of Automatic Detection Technology in Automobile Safety System

Automatic detection technology has been widely used in industrial and agricultural production, national defense construction, transportation, medical and health, environmental protection, scientific research and people's daily life, and plays an increasingly important role in national economic development and social progress. An essential and important basic technology. This paper describes the detection object and detection principle of automotive sensors, and introduces the specific application of the relevant sensors in the anti-lock braking system and airbag system.

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1 Application of automatic detection technology in automobile safety system

1.1 Anti-lock brake system (ABS)

With the implementation of the new law, traffic safety has received more and more attention from all parties. At the same time, the state has also promulgated a series of mandatory regulations and national standards to impose strict restrictions on vehicle safety performance. The most basic active safety device for car safety equipment - ABS anti-wheel lock mechanism has been forced to install on the prescribed car. The world's first anti-lock Brake System (ABS) was introduced in 1950 and was first used in aircraft in the aerospace sector. It has only been researched in automotive applications since 1968, one of the greatest achievements of automotive technology since the late 1980s.

ABS is an automobile safety control system with the advantages of anti-skid and anti-locking. It not only has the braking function of the ordinary braking system, but also prevents the wheel from being locked, so that the car can still turn under the braking state to ensure the car's The stability of the braking direction prevents the occurrence of side slip and deviation. It is the most advanced braking device with the best braking effect in the automotive field.

ABS consists of three parts: sensor, brake pressure regulator and electronic controller. The electronic controller is also called the Electronic Control Unit (ECU). The sensor for testing the number of revolutions of the wheel and the controller for adjusting the number of revolutions are essential components for achieving the control target, which is an important theoretical basis for the development of the ABS system for vehicles. The working principle of the anti-lock braking system of the car is shown in Figure 1.

The sensor is mainly a speed sensor mounted on the wheel. Its function is to detect the movement state of the wheel, obtain the signal of the wheel speed (speed), and send out the signal that the wheel will be locked. The main function of the ECU is to receive the wheel speed sensor. The pulse signal, the wheel speed, the reference vehicle speed, the wheel deceleration, the slip ratio, etc. are calculated, and the judgment and output control commands are sent to the actuator; the brake pressure regulator is the actuator, and the electronic control unit ECU is accepted. After the command, the solenoid valve in the regulator is actuated to adjust the pressure of the brake to increase, maintain or decrease, and the brake pressure control function is realized, so that the braking force of each wheel satisfies a small amount of sliding but close to the locking system. The state of motion is such that the vehicle does not lose its directionality and stability during emergency braking. The oil pressure of the wheel brake cylinder is reduced by the control command regulator, and the braking torque is reduced. After a certain period of time, the original oil pressure is restored, and the cycle is repeated (up to 5 to 10 times/s). The wheel is in a rotating state and has the greatest braking torque.
1.2 Airbag system
The airbag was invented by American John Hotrich. In 1952, after an accident, he developed the idea of ​​designing a crash safety device. The airbag is mainly composed of main components such as a collision sensor, an airbag control unit (SRS ECU), an airbag unit, and an airbag system indicator.
The key part of the collision sensor airbag is the collision sensor. The function of the sensor is to detect the impact or deceleration value when the vehicle collides, and then transmit the signal to the electronic control system to determine whether the airbag needs to be opened.
The function of the ECU is to receive the signals input by the collision sensor and other sensors, determine whether to ignite the airbag, and perform self-diagnosis of the system fault.
The airbag assembly is mainly composed of an air bag, a coil spring, a gas generator, an igniter, and the like. The gas generator generates an ignition action according to the signal indication, ignites the solid fuel and generates gas to inflate the airbag, so that the airbag rapidly expands.
The SRS indicator is used to indicate the working status of the airbag. When an abnormality occurs, the indicator light automatically lights up and alarms.
The basic principle of the airbag is that when the collision occurs, the controller recognizes and judges the strength of the collision according to the collision impact speed (deceleration) signal. When the collision strength reaches the set condition, the sensor that detonates the airbag quickly activates the igniter to detonate the nitrogen solid state. The particles form a rapidly expanding air pocket to cushion the impact of the driver.
Car airbags are available in both mechanical and electronic types. The airbag, air pump, sensor and other components of the all-mechanical airbag system are collectively mounted in the steering wheel, and the structure of the airbag is as shown in FIG. 2.
In the electronic airbag system, when a car collides, according to the degree of sensor-induced collision, the sensing signal is sent to the electronic control unit ECU, and the collision signal is recognized by the ECU. In the case of a mild collision, the airbag does not operate; in the case of a moderate to severe collision, the ECU will signal the ignition of the igniter to inflate the airbag in a very short time to protect the occupants. The specific working process of the electronic airbag system is shown in Figure 3.
In the electronic airbag system, the control program block diagram of the double-action double airbag and the double seatbelt pretensioner is shown in Fig. 4.
The steps of the working process are: first, the car is ignited, the airbag starts to work, the electronic circuit such as the CPU is reset, the work is ready, and then the self-test. After the collision occurs, the CPU determines the magnitude of the collision speed and issues different control commands. When a collision occurs, the controller identifies and judges the strength of the collision according to the acceleration signal sent by the sensor. When the collision strength reaches the design condition, the sensor that detonates the airbag quickly activates the igniter to detonate the nitrogen solid particles to form a rapidly expanding air bag. To cushion the impact of the front passengers, mainly to protect their heads from injury. Of course, you don't have to be nervous. The sensor will automatically calculate the intensity of the collision. It will not cause the airbag to detonate due to improper driver operation or small obstacles and light collision.
2 Conclusion
With the rapid development of cars, anti-lock braking systems and airbag systems play an important role. More manufacturers are developing and producing anti-lock braking systems and airbag systems, and their technology is becoming more and more advanced. . It should be pointed out that ABS is only an auxiliary system for braking. It can help the driver to control the state of the vehicle during braking and prevent the vehicle from losing steering ability during braking. The main control is still the driver, so speeding can still cause an accident. And it should be emphasized that fastening the seat belt is an important condition for the airbag to play a protective role.

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