Technical column



Current situation and development trend of automotive electromagnetic compatibility at home and abroad

        With the extensive application of modern electronic technology in automobiles, mechanical automobiles in the traditional sense have been replaced by modern electronic automobiles. Various electronic and electrical products have accounted for 30% of the total cost of automobiles, or even more, and this trend is still increasing. in constant development.

        The application of electronic technology plays a very important role in solving the economy, safety, and comfort of automobiles. However, the development and application of many electronic products have also brought an important issue that cannot be ignored to the automobile industry- ---Research on Electromagnetic Compatibility of Automobiles.

        Electromagnetic Compatibility (EMC) is a new technology derived from electromagnetic interference. It refers to the ability of electrical devices or electrical systems to work in a specified environment without interference or environmental interference. In order to solve the problem of electromagnetic compatibility, we must first find the source of interference in the electromagnetic environment of the car. Interference sources can be divided into in-vehicle interference sources and external interference sources.

source of electromagnetic interference

Ø Interference sources in the car

        It refers to the electromagnetic interference generated by various electronic and electrical systems on the vehicle. The electromagnetic interference generated by electronic and electrical equipment is due to the fact that there are many wires, coils and electrical appliances with contacts in the electronic products used in automobiles, all of which have different capacitances and inductances, and any closed loop with inductance and capacitance will form oscillations circuit. When electrical equipment produces sparks, it will generate high-frequency oscillations and emit them into the air in the form of electromagnetic waves, which will interfere to varying degrees with the normal operation of radios, televisions and other radio devices on the car and within a range of hundreds of meters around. . The interference generated by the car will not only affect the normal operation of external electronic and electrical equipment, but also affect the normal operation of its own electronic and electrical equipment. Therefore, electronic environmental interference will have an adverse effect on the performance of electronic products, and even lead to their loss of function.

        The radio interference source of the car is mainly the ignition system of the engine, and its interference wave comes from the high-frequency oscillation of the secondary voltage of the ignition system. Secondly, electromagnetic waves will also be generated when the generator load current changes suddenly and is rectified. Starters, generators, flashers, contact-type electromagnetic vibration electric horns, wipers, instrument systems, etc. will also produce small electromagnetic waves of conducted interference and radiated interference.

        Interference electromagnetic waves generated by automotive electrical appliances have pulse characteristics and a wide frequency band, and their frequencies are generally between 0.15 and 1 000 MHz. Interference electromagnetic waves generated by automotive electrical appliances can be divided into two types: conducted interference and radiated interference. Conducted interference electromagnetic waves are directly input into radio equipment and electronic equipment through automobile wires, while radiated interference electromagnetic waves propagate in space and are input into radio equipment through antennas (such as ignition system high-voltage lines are equivalent to antennas).

ØInterference sources outside the vehicle

        External electromagnetic interference caused by natural phenomena, social environment, etc. has a serious impact on automotive electronic systems. External electromagnetic interference refers to various artificial electrical equipment, such as: high-voltage power lines, near tram tracks, radio and television equipment and radio communications The electromagnetic radiation radiated by equipment and other equipment that interferes with the car and the electromagnetic interference caused by natural phenomena such as lightning.

Research Status of Foreign Vehicle Electromagnetic Compatibility

        At present, the developed countries in the world have made some achievements in the research of automobile electromagnetic compatibility, and formed a set of automobile electromagnetic compatibility system. This is mainly manifested in: having relatively complete automotive EMC testing standards and specifications; having an effective agency for EMC testing, management and certification of complete vehicles and parts; having a high-precision automotive EMC testing system; developing Developed a large-scale automotive electromagnetic compatibility prediction, analysis and design software. Third-party testing and certification agencies, automotive research institutions, etc. have also carried out research on automotive electromagnetic compatibility, and have successively established their own electromagnetic compatibility laboratories.

1. A relatively complete automotive EMC standard specification. Organizations such as the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), the International Special Committee on Radio Interference (CISPR), the American Automobile Manufacturers Association (SAE), the German Standards (DIN), and the German Association of Electrical Engineers (VDE) are all listed in their documents. The interference type and strict level of anti-interference detection are stipulated in the standard. Almost all automobile manufacturers and manufacturers of automotive electronic products accept these standards or supplement these standards as their own enterprise standards.

2. Numerous large EMC laboratories. German Volkswagen began to establish an open-air automobile anti-radio interference test bed in 1965, and continued to improve and perfect it in the 1970s. In 1978, it introduced more advanced testing equipment. In 1985, it vigorously promoted the preparation of the automobile electromagnetic compatibility center system. In 1987, the new Automotive Electromagnetic Compatibility Center was completed. There are three darkrooms in the electromagnetic compatibility laboratory of PSA company in France: one is used for the whole vehicle, one is used for component and vehicle receiver adjustment, and the other is specially used for component testing. The size of the darkroom for testing the vehicle is 15.5 mX 10 mX 6 113, the diameter of the turntable is 8.4113, and the wheelbase adjustment range is 2 000-3 700 mm. There are hundreds of EMC laboratories in European countries. Other institutions with large automotive EMC laboratories include German BMW, Audi, French u-TAC, British Automotive Industry Research Association (MIRA), and Italian Fiat.

3. Carry out automotive EMC prediction research. Automotive EMC research was basically limited to experiments before, but with the emergence of electric vehicles and hybrid vehicles, as well as the rapid increase of automotive electrical systems and the continuous improvement of signal frequencies, automotive EMC issues have become more and more important to car manufacturers. a burden of In order to improve the efficiency of solving problems and reduce the cost, the application of digital modeling and digital simulation technology to the research of automotive electromagnetic compatibility is becoming a hot spot in the research of automotive electromagnetic compatibility.

A Survey of Domestic Automotive Electromagnetic Compatibility Research

        my country's automotive electromagnetic compatibility technology research work began with the measurement of automotive electromagnetic interference characteristics. In the early 80s of the 20th century, a thorough measurement test on the electromagnetic interference characteristics of automobiles was started. In 1994, the China Automotive Technology Research Center took the lead in the country to carry out the measurement of the radio interference characteristics of automobiles, and conducted a general survey of all types of automobiles (new cars) in the country. According to statistics from the census, the passing rate is only 24%, and a considerable number of unqualified vehicles are seriously exceeding the standard. From the 90s of the 20th century, my country began to control the radio interference of automobiles. Domestic automobile inspection agencies and manufacturers have purchased electromagnetic interference receiver systems to study and test the radio interference level of automobiles and to control them. State-level automobile testing institutions including Tianjin Automobile Testing Center and Chongqing National Bus Quality Supervision and Inspection Center all have the ability to detect electromagnetic interference. Since then, domestic research on electromagnetic compatibility technology for automobiles and their components has been carried out, and large-scale electromagnetic compatibility experimental facilities have been researched and built. In March 2001, the EMC Testing Laboratory of China Automotive Technology and Research Center passed the accreditation of the China Laboratory Accreditation Committee, marking a new development of my country's automotive EMC testing technology. The electromagnetic compatibility experimental facilities of the China Automotive Technology and Research Center include an open field field, an electromagnetic wave anechoic chamber, a conduction shielding room, an amplifier room and a measurement control system. As the main body of the electromagnetic compatibility laboratory, the anechoic chamber can realize the uniformity and attenuation of the indoor electromagnetic field, simulate the electromagnetic distribution of the outdoor open space, and complete various tests related to the electromagnetic field. The laboratory has passed the test of the SIS testing agency in the United States, and its performance indicators meet the technical requirements of relevant international standards.

        From the perspective of domestic situation, because the overall level of my country's automobile industry is backward, the importance of automobile electromagnetic compatibility is insufficiently understood, so there are few researches on electromagnetic compatibility. Automotive electromagnetic compatibility regulations are not perfect, and the enforcement is not strict enough. In 1992, my country promulgated the mandatory national standard GB14O23-92 "Testing Methods and Permissible Values ​​of Radio Interference Characteristics of Vehicles, Motor Boats and Spark Ignition Engine Drives", which restricted the electromagnetic wave interference radiated by automobiles to the environment. In 1998, GB 17619-98 "Limits and Measurement Methods of Electromagnetic Radiation Characteristics of Electronic and Electrical Components of Motor Vehicles" was promulgated. In 2001, GB/T 18387-2001 "Limits and Measurement Methods of Electromagnetic Field Radiation Intensity of Electric Vehicles Broadband 9 kHz~30 MHz" was released.

Future trends

        With the improvement of the electronic degree of automobiles, automobile electromagnetic compatibility technology is being established as an important branch of automobile technology. The degree of people's concern and attention to the electromagnetic compatibility of automobiles is increasing. The standardization process of my country's automotive electromagnetic compatibility technology will be accelerated, new national standards will be continuously formulated, and old standards will be continuously revised. The national standards to be formulated in the next 2 years are: GB "Road Vehicles - Limits and Measurement Methods of Electrical Disturbance Caused by Conduction and Coupling"; GB "Road Vehicles - Limits and Measurement Methods of Electromagnetic Disturbance Caused by Electrostatic Discharge"; in the future For a period of time, it will focus on the research and testing of electromagnetic compatibility of auto parts, so as to promote the accelerated development of domestic auto electronic and electrical components technology, improve the production level of domestic enterprises' auto electronic and electrical components, and accelerate the localization process of China's auto production. On the basis of the staged achievements in the electromagnetic compatibility technology of electronic and electrical components, we will strengthen the research and testing of electromagnetic immunity of automobiles, catch up with the development level of international automobile technology, and improve the overall level of domestic automobiles.

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