Multiple tests generated by electromagnetic compatibility testing and certification of new energy vehicle systems

The electromagnetic compatibility of basic vehicles has good professional regulations in all test systems, and the corresponding test completion standards are also relatively sound, which can better carry out the experiment of Chinese legal system standards. With the development of intelligence, networking and electrification of the entire automobile industry, the characteristics of the automobile have gradually changed from a person to a node on a huge intelligent transportation network.

The biggest change of the "three modernizations" automobile is to make the automobile and its surrounding environment, including road traffic facilities, other vehicles and various nodes contained in the environment more and more closely integrated. All kinds of new functions in cars focus on the interaction with the environment, which adds new challenges to the electromagnetic compatibility test and verification of new energy vehicle systems.

According to the basic classification, the electromagnetic compatibility performance of vehicles is generally divided into transmission characteristics and anti-interference characteristics. The transmission characteristics focus on the protection of electrical equipment other than vehicles, which is mainly regulated by laws and regulations in China (GB14023. GB/T18387 and GB34660); Anti-interference characteristics focus on the tolerance level of the vehicle itself to external influences. Existing laws and regulations (GB34660) require more attention to the safety and experience performance of vehicles in the immunity test.

01 Intelligent network vehicle electromagnetic radiation transmission detection

Challenges

Intelligent networked vehicles have introduced more intelligent security subsystems and networked communication subsystems. The biggest difference between this new system and the traditional vehicle subsystem is that they not only collect the operation information inside the vehicle through internal sensors, but also collect the operation information inside the vehicle through new external sensors such as cellular mobile communication antenna. V2X communication antenna, vehicle-mounted millimeter wave radar, video image acquisition system, etc., actively collect the road condition information and other vehicle working status information around the vehicle, even beyond the range of vision.

Some of these sensors obtain information through wireless communication. When they work, they radiate electromagnetic waves and need a peripheral device that can communicate with them to maintain normal communication working conditions. According to the basic idea of electromagnetic compatibility test, it is specified that the vehicle can cover the working conditions of large transmission state when conducting radiation transmission detection. This requires all systems and functions to be in operation, including on-board wireless communication system. However, the wireless transmission equipment conforming to the Chinese radio management standard will radiate useful signals, and it is required to be less than the vehicle radiation emission limit. This behavior may lead to a contradiction between the results of radio management and electromagnetic compatibility management, and lead to problems in policy understanding or implementation.

Therefore, the D branch of the National Federation of Radio Interference Standardization Technology discussed the excessive exemption of radiation transmission in the working frequency band caused by intentional transmission, and wrote the exemption method into the supplementary rules of GB14023 standard. In the experiment link, how to distinguish the transmission of vehicles and the transmission of peripheral equipment used to stimulate the operation of vehicle equipment. How to distinguish the signal of the working frequency of the equipment from the harmonic or spurious transmission of the non-working frequency band is the key issue to distinguish whether the radiation transmission of the vehicle to be tested meets the requirements.

The upper limit frequency of the wireless equipment commonly used in traditional cars should not exceed 6GHz. After the introduction of 5GV2X in communication and millimeter wave radar, the upper limit output power of the wireless equipment on board soared to 81GHz. There are no clear international and domestic restrictions on such high-frequency vehicle radiation transmission, and the design and construction of vehicle electromagnetic compatibility laboratories often do not have such a high frequency.

The external radiation transmission of the whole vehicle in the above frequency band of 6GHz needs to be limited by the test standards and limit specifications recognized by the public. The detection of the millimeter wave frequency band should also put forward new requirements for laboratories and detection equipment. From the perspective of test equipment, in the integrated radiation transmission test of intelligent network, it is also necessary to ensure that the test equipment will not affect the electromagnetic bottom noise of the test environment, otherwise it will be difficult to ensure the accuracy of the radiation transmission test results.

02 Problems faced by electromagnetic immunity detection of intelligent networked vehicles

First, test the change of center of gravity

The detection focus of traditional electromagnetic interference immunity test is more on the anti-interference level of the whole vehicle and parts, that is, whether the vehicle to be tested and the parts to be tested will have dysfunction under the specific electromagnetic environment. This is to consider the performance mode of the whole vehicle or parts from the perspective of function completion. However, in the intelligent networked vehicles, because the vehicle has won its own control to a certain extent, whether the system with control can be properly implemented according to its prediction function is a difficult problem that needs to be paid attention to by the intelligent networked vehicles, and this problem is the issue of functional safety. Therefore, the focus of electromagnetic interference detection of intelligent networked vehicles must be changed from simple function to safe investigation.

Secondly, the test generated by certification according to requirements

For example, many vehicle safety specifications such as ISO26262 Functional Safety of Road Vehicles have been continuously accumulated and upgraded in accordance with safety requirements. The completion process of the whole vehicle safety level is actually the design and implementation process of different safety requirements of the whole vehicle, which is actually a method of weakening control. In the aspect of safety design, it will be strict. It is not possible to deal with safety problems according to the overall method. Each piece represents a specific safety requirement, thus decomposing the safety problems; In the subsequent testing and verification process, by verifying whether the safety requirements have been completed, selecting the cumulative form, and gradually approaching the detailed safety problems, the whole evaluation process can be more easily realized, and similar optimization solution replacement can be completed. However, this test standard based on safety requirements is greatly jeopardized by the popularity of requirements. Under the low penetration rate, the accumulation level of safety demand is insufficient, and the safety factor of vehicles cannot be fully defined. So, how to find it as much as possible Another test for the electromagnetic immunity test of intelligent networked vehicles is to clarify and test the safety requirements.

The third is the test of detection quantity

Obviously, the higher the security requirements of the test, the closer the result will be to the final integrity security certification result. However, a large number of safety requirements will improve the definition of flammability ISO26262 road vehicle function safety, and the hazard that causes personal and economic losses is the combination of internal injury and external operation scenarios. Due to the combination of the same internal injury and different external operation scenarios, the safety risks and damage conclusions of the injury event may vary greatly. Therefore, in order to ensure the effectiveness and high penetration of detection, it is necessary to understand all possible vehicle states and the matching of each operation scenario.

However, problems also follow. On the one hand, the ISO26262 action detection standard focuses on the harm of system abnormal behavior, including the stop of predictive behavior and the generation of unpredictable behavior, and then studies the source of the above fault behavior, including any hardware failure and system failure. In other words, from the perspective of functional safety, there are many reasons to consider internal injuries; On the other hand, the possible road characteristics (road geometry), topological structure, ground characteristics, etc.), environmental characteristics (temperature), temperature, time periods of different humidity, etc. must be comprehensively considered Traffic characteristics (number of other traffic participants), working status, location information compared with the vehicle, etc.). The number of detection scenarios composed of internal and external complex options is huge. In addition, different frequency bands, intensities and polarization methods specified for electromagnetic immunity detection. Due to the interference signals in the modulation mode, the number of electromagnetic immunity detection scenarios of intelligent networked vehicles finally formed is staggering, and it is impossible to complete the complete scenario and electromagnetic immunity detection under the reasonable time and cost. In other words, it is difficult to realize the differential detection of electromagnetic immunity of intelligent networked vehicles in reality, and more efficient detection concepts and test standards must be found.

Finally, test the overall security risks. The safe completion of vehicle functions does not mean the safe completion of vehicle level. In addition to functional safety and functional safety, vehicle level safety also includes two aspects: expected functional safety and network safety. From the most basic function completion (that is, focus only on whether the target function can be completed normally, and pay little or no attention to the small range changes of external operation scenarios), functional safety adds risk judgment on the premise of function completion, aiming to clarify whether the predicted function can be completed accurately, and pay attention to the accuracy and quality of realization; Under the condition that the expected function is safe, and under the condition that the prediction function has been properly completed, compare the prediction function with the actual needs, and observe whether the prediction function can meet the requirements of specific scenarios; When network security has integrity prediction function, discuss whether external intentional intrusion will affect the integrity of prediction function. These aspects are closely linked and complement each other.

Therefore, when implementing the electromagnetic immunity detection of intelligent network vehicles, the function completion problem that the traditional electromagnetic immunity detection focuses on is not enough at the security level. The proper handling of security issues must be designed and implemented from four perspectives. In general, the above challenges are actually difficult problems in test case design. That is to say, for the electromagnetic immunity test to ensure the safety of intelligent network vehicles, exhaustive testing is unrealistic, so if you want to develop a set of industry-acceptable electromagnetic immunity test standards, you need to agglomerate the function test. The safety of intelligent network vehicle or driverless vehicle is particularly important. How to ensure its electromagnetic safety can reach or exceed the current level of the vehicle while cohering the function test requires the designer to have a deeper understanding of the new functions and features of intelligent network vehicle, as well as the relationship with other software (such as power, chassis, conversion), from the perspective of various fault behaviors, external scenarios and hazards, Sort out the functional test set that must be verified by the intelligent network vehicle, and pay attention to the vehicle parameter level under various functional tests, which requires relevant technical personnel to gradually improve in exploration.

The reason why the intelligent networked vehicle is called intelligent networking is that it is equipped with various sensors that can identify the surrounding environment and wireless communication equipment that can communicate with non-line-of-sight external devices, so that the vehicle has the ability to properly identify the surrounding perspective and non-line-of-sight internal environment and make corresponding response. When traditional cars are tested for electromagnetic compatibility, generally only the electromagnetic environment of the test environment is specified to be clean, and the car can reach a certain speed in the test environment; The intelligent networked vehicle needs to simulate the road environment in the experimental environment, interact with the vehicle normally, which is convenient to deceive the on-board sensors and wireless communication equipment, and mistakenly believe that the vehicle is actually running on the road, and the corresponding intelligent and networking functions can be normally stimulated. These requirements make a huge test of the test conditions.

First of all, this requires a series of auxiliary equipment. For example, the automatic cruise control system (ACC) and automatic emergency braking system (AEB) need to use radar target simulator or corner reflector when conducting electromagnetic compatibility function test Secondly, in the experimental environment, there are no obstacles and target features close to the road environment, which may lead to abnormal opening of the on-board intelligent network function or abnormal opening of additional elements, such as reflection characteristics and on-board radar system targets, or especially gray and particularly bright will affect the working lighting of the on-board camera.

This requires reasonable adjustment and calibration of the experimental environment before the experiment. In addition to using a large number of types of machines to complete the special requirements of its test environment, the electromagnetic immunity test of intelligent networked vehicles also provides a higher technical standard for the test equipment: in the radiation immunity test of intelligent networked systems, it is necessary to ensure that the test equipment will not be affected by increased electromagnetic interference, Otherwise, it is impossible to judge whether the function in the test result or the function is caused by the insufficient anti-interference characteristics of the test equipment or the vehicle itself; In extreme cases, the test equipment will also be damaged due to the high field intensity of the radiation immunity test. This also makes many common equipment for road test, bench test and simulation test of intelligent networked vehicles cannot be used for electromagnetic compatibility test, and the emc test equipment should be specially designed.