Automotive Active Safety System When military experts discuss the different styles of weapon defense systems in various countries, they often involve so-called passive systems and active systems. This idea is also reflected everywhere in the design of automotive safety systems. The representative of the car's passive safety system is the traditional bumper, seat belt, airbag, etc. The main purpose is to minimize the degree of injury to people in the car when the accident occurs. In contrast, the active safety system considers how to avoid such accidents. A variety of sensing and detection systems are required to achieve active avoidance and prevention of accidents, such as front and rear vision radar, night vision system, infrared detection, ranging, CMOS / CCD image monitoring, and automatic tire pressure monitoring system (TPMS). The main working principle is that the sensor obtains the required physical analog signal value from the outside world, converts it into a digital signal and then passes it to a specific control unit for analysis, and carries out effective decision-making and preventive measures. Figure 1 The trend of automobile safety system from passive to active mode 1. Pre-collision system Automobile accidents are mostly due to collisions between objects in relatively high-speed motion, and the causes of collisions are mostly related to violations of traffic rules, obstruction of the driver's sight, and inattention. Wait. At present, many manufacturers are studying the pre-crash safety system as a response. The pre-crash safety system can be divided into two categories: protection of people in the vehicle (drivers and passengers) and protection of people outside the vehicles (passengers and vehicles), but the core of safety protection is the active preparation and protection of collision actions Measures. For the pre-crash safety system in the car, when the relevant sensor or radar detects the potential collision hazard, it will first warn the driver in the car. If the warning is invalid, the automatic braking system will be activated before 0.6 seconds, according to the driver's braking power Increase auxiliary oil pressure to fully reduce vehicle speed and avoid collision. At the same time, the pre-crash safety system will also provide support for passive protection in the car, such as closing the window, adjusting the angle of the seat or the tightness of the seat belt to reduce the collision intensity and let the airbag play a greater role. Outside the car, the pre-collision safety system can also protect the object as much as possible through a series of measures. If a collision is inevitable, the safety system will open the external airbags (such as bumpers, windshields, etc.) opposite to the pedestrian impact surface, and minimize the impact force on the fragile and fatal parts such as the head, chest, and waist. 2. ACC adaptive cruise control system The so-called pre-collision system can only make a series of active preparations before the collision occurs, rather than "prevent" the collision. The rapidly developing ACC (AdapTIve Cruise Control), that is, adaptive cruise control, can partially prevent collision accidents. ACC belongs to the speed control system for forward driving, and its main function is to control the safe distance between the vehicle and surrounding vehicles. It provides drivers with auxiliary information and suggestions for safe driving through multiple sensors arranged around the body and advanced algorithms of the in-vehicle control system, and sends timely alerts to the driver when a potential danger is detected, or even directly intervenes in the control of the vehicle System to intervene. However, in any case, ACC has only a partial degree of intervention on the brakes, and the driver is still the core of driving. The key to ACC's speed and distance control is to lock the target vehicle ahead, and then calculate the vehicle's speed, acceleration and other driving information. The owner will set a reaction time for ACC in advance. When ACC is driving, it will then calculate the safe distance based on the relative speed of the vehicle and the current distance, and judge the next speed control; and when the distance of the vehicle is too close ACC control range, the system switches to the pre-collision safety handling system. 3. Driving warning system The driving warning system mainly uses CCD / CMOS and other sensors and imaging devices as monitoring methods, and uses the built-in identification system to determine whether the vehicle status and driver's behavior are normal. If there is a problem, a warning signal is issued in time to avoid accidents. Some driving warning systems can detect the alcohol concentration of the driver's exhaled gas and give appropriate warnings. In addition, the rear and side monitors can also belong to the driving warning system, which can eliminate the driver's visual blind spot and avoid the common collision accidents when reversing. The functions of the driving warning system mainly include lane departure warning (LDW), driving danger warning, visual blind spot warning (or blind spot detection) and so on. The lane departure warning mainly warns the driver when he enters the wrong lane, or prompts him to turn on the turn signal when he changes lanes. The driving warning system can provide effective auxiliary information for the driver's safe driving, but if the auxiliary information is not comprehensive enough, it cannot play its due role. On the other hand, everything has its two sides. If the auxiliary information is too much or too complicated, it is not only not conducive to safe driving, but sometimes it will make the driver tired of handling all kinds of auxiliary information and not concentrate on it, which is easy to cause accidents. In addition, the means by which auxiliary information is sent to the driver is also one of the issues worth studying. Screen display, instrument panel, voice, etc. are traditional means. At present, there are also "sense warning" methods, that is, the car sends information to the driver through the vibration pedal, seat, steering wheel, etc., or attracts its attention. 4. Electronic stability program Driving is a combination of people and vehicles. In addition to monitoring the behavior and state of the driver, the safety control system should also be able to effectively control the behavior of the vehicle. ESP (Electronic Stability Program) is an electronic stability program that integrates ABS (AnTI-lock Braking System) and TCS (TracTIon Control System), which is an active vehicle safety system that can assist the driver to keep the vehicle normal State and behavior to prevent phenomena such as tire slippage and runaway. ABS is called an anti-deadlock brake system. When a car tire is deadlocked, ABS will quickly release the brake to prevent the vehicle from deviating. The opposite TCS is called the tracking control system. When the tire is idling, the tire can regain grip by reducing the torque or the deadlock of the tire. By integrating the two, ESP will apply a different braking force to each tire to correct the driving trajectory when the vehicle slips or understeer. Sensor type and selection Whether it is an auxiliary prompt system such as a driving warning system or a system control of an electronic stability program, the effective working basis is sufficient and reliable information and the correct and rapid judgment ability of the background. The key to obtaining reliable information is the sensor and its reasonable distribution; the correct judgment comes from the fast response and reliable algorithm of the control system. Vehicle sensors are located at different locations on the vehicle body according to their specific characteristics and uses, including radar, infrared, LIDAR (Light DetecTIng and Ranging), ultrasound, acceleration sensors, CCD / CMOS imaging systems, etc. The main sensors used in the pre-collision system are millimeter wave radar or lidar. Among them, the price of millimeter wave radar is relatively high, mainly for the high-end car market; while the cost of laser radar is relatively low, only about 1/3 of the millimeter wave radar, targeting the low-cost car market. However, in terms of performance, the short wavelength of the laser limits its application range, which is not conducive to the use in harsh environments such as rain and snow. The infrared and image sensor-based monitor technology is mainly used for obstacle recognition and auxiliary visual field when driving. Infrared imaging can be divided into far-infrared (FIR) technology for temperature detection and near-infrared (NIR) technology for night vision. FIR can detect organisms with temperature, and it can display the heat radiated by the object as an image; NIR is mainly used for night vision and other poor sight conditions, which can be detected farther than the car light, but at the same time it is also susceptible to the opposite light It is mainly used for auxiliary road condition display such as night vision. If you need to detect the specific conditions outside or even inside the car, you can use CCD or CMOS components as a visual image sensor. At present, the application of CCD / CMOS is becoming more and more extensive. With the advanced visual recognition algorithm, the moving objects in the imaging range, the road surface condition and the friction coefficient, the roadside traffic signals and signs, and the road lane separation line can be distinguished, completely Can become the driver's eyes. CCD / CMOS can also achieve greater dynamics to express image details in dim and high-contrast environments. This technology is achieved by capturing and synthesizing two high-sensitivity and low-sensitivity images. In addition, if CCD / CMOS is combined with infrared or radar as described above, it can form a hybrid sensor (Sensor Fusion). After the infrared generator illuminates the target object, the reflected infrared light is absorbed by the CCD / CMOS, so the road conditions can be recognized no matter the day or night, providing a powerful auxiliary vision for the driver. System architecture analysis The pre-collision handling, safety speed / distance control and other warnings of the automobile safety system are very similar to the principle of the strain system, that is, the ECU (Central Electronic Control Unit) receives the relevant information of the external sensors and performs real-time evaluation through the built-in algorithm And decide the best contingency measures. Therefore, the design of the automotive electronic system is not much different from the general system design, but the hard real-time and reliability are the distinguishing characteristics that distinguish it from other electronic control systems. First, take the airbag control system as an example. The system is mainly composed of an airbag in front of the driver and passengers, a collision sensor (Satellite Sensor) located outside the body, an acceleration sensor (G-Sensor) placed on the door, seat and roof, and usually 16 bits or 32 The MCU ECU is composed of several parts. When the body is collided, the impact sensor will immediately send a signal to the ECU. The ECU will collect the collision intensity, seat position, passenger weight, seat belt condition and other parameters for rapid evaluation, and pass the electric explosion driver in a very short time ( Squib Driver) Open the airbag to protect the safety of the people in the car. Figure 2 Airbag system architecture diagram As shown in Figure 3, Active Suspension is also a relatively common security system in automobiles, which can greatly improve the handling of the vehicle. The active suspension system is mainly composed of sensors, shock absorbers and computer control systems. The system can collect data such as the speed, acceleration, load, steering degree, left and right G force of the car to adjust the suspension coefficient and the height of the chassis and the ground in real time by the program. Figure 3 The composition of the active suspension system architecture More and more national laws and regulations have put forward requirements for the performance of anti-lock brake systems (Anti-lock Brake Systems, ABS), and the higher requirements for their reliability increase the complexity of ABS design and the difficulty of research and development. As shown in the system shown in Figure 4, the main purpose of ABS is to prevent the dangerous situation of vehicle stalling. When the control link finds that the emergency brake causes the speed to be too low, it will quickly release the brake, giving the tire enough rolling space and greater grip. Ground force to prevent the vehicle from deviating. The key to this system is the measurement of tire speed. Figure 4 ABS system architecture The system shown in Figure 5 is an electronic power assisted steering (EPAS) system, referred to as a power steering wheel. Compared with the traditional hydraulic steering wheel, EPAS uses an electronic motor to provide the driver with auxiliary steering control. EPAS generally obtains the position and torque of the steering wheel from sensors, and then combines the parameters of vehicle speed, engine temperature, battery power supply and other parameters to realize the auxiliary control of the electronic motor. EPAS has gradually entered the market. It can not only reduce the engine load, but also further improve the fuel efficiency. Figure 5 Power steering wheel system architecture Seat Belt Tensioner is also an advanced driving safety guarantee system, which can be used as a subsystem in the collision system. The pre-tensioned seat belts give the driver and passengers greater shoulder space when the vehicle is driving normally, so that they can enjoy the comfort of driving and riding; For the physical injury caused, the pre-tensioned seat belt can be quickly tightened, so that the person is close to the seat, reducing the risk of collision with the object in front. Figure 6 Pre-tensioned seat belt system architecture diagram in conclusion With the continuous advancement of electronic technology and control science, revolutionary changes have also occurred in automotive electronic systems. The vehicle's safety protection system is gradually upgraded from traditional passive systems such as seat belts and airbags to active safety systems such as pre-crash control. The realization of all these benefits from the support of multiple sensors and their control systems for driving, braking, engine control, vehicle speed control, safety protection and so on. Liquid Crystal Display For Clock Dongguan Yijia Optoelectronics Co., Ltd. , https://www.everbestlcdlcms.com