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Test methods used by automotive test dummy

Release time: 2015-05-08 10:52

Test methods used by automobile test dummy: The automobile collision detection test has various evaluation indicators, including the acceleration shock value of various organs in the dummy, the force and moment suffered, and the compression deformation displacement. It is necessary to comprehensively evaluate the signal of the body acceleration sensor, the amount of deformation of the body, the door opening condition after the collision, and the amount of fuel leakage. And a large part (especially the sensor signal data of the dummy) needs to be collected and processed by the electrical measurement data acquisition system, and finally the test results are fed back to the tester to calculate the dummy's injury value and other evaluation indicators. In some cases, the number of electrical measurement channels is up to 150, involving acceleration, force and torque, displacement, current, and switching. It can be seen that the data acquisition system is a very important measurement in automobile crash tests. Link.

I. Analysis of the characteristics of the car crash test data acquisition system The crash test data is one of the most important basis for evaluating the passive safety performance of the vehicle. The analog signals obtained from the sensors inside the body and the dummy are converted into digital signals by the data acquisition and analysis system. Various collision curves and indicators are obtained after processing by hardware circuits and software programs, and the test results are expressed in a quantified form, which makes it easier to implement regulations and evaluate vehicle passive safety performance in more detail.
At present, many data acquisition systems used in automobile crash tests are mainly MINIDAU of German KT company, DIS3000 of Japan Kyowa Electric Industry, TDAS series of American DTS, and NA33 of German Messring. These products can realize the basic functions of data collection in automobile collisions, and each has its own characteristics when used: MINIDAU's acquisition control software adopts ISO / DTR13499 standard, and uses MS-ACCESS to establish and maintain the sensor database. But the operation is a little complicated; the features of DIS3000 are concise and practical, easy to operate; TDAS is small, flexible, easy to install, and has a good interface visualization, and supports ISO / DTR13499 data format standards; NA33 is more flexible in structure and can be integrated with the traction system Control usage, sampling frequency and recording time are higher.
1. The structure of the data acquisition instrument requires anti-shock performance. In a car crash test, the vehicle under test needs to reach a certain speed, which is usually achieved by a motor traction system. In the process of being towed and accelerating, the vehicle must accelerate from tens of meters to hundreds of meters. Therefore, the current data acquisition and analysis system used in automobile crash tests is mainly vehicle-mounted, which completes the data acquisition tasks in real time. In addition, the data acquisition instrument must have a high impact resistance, which is usually required to be able to withstand 1000 times of 980m / s2 (10ms) impact in three directions. This is also an important feature of the car crash test collector that is different from ordinary collectors. In addition, the data acquisition instrument should have an integrated internal battery and memory, which can guarantee at least 30 minutes of operation time, and the sampling frequency should not be less than 10kHz.

2. Electrical performance The resolution of the AD converter is not less than 16bit, and it can collect signals from strain and piezoresistive sensors, semiconductor sensors and voltage measuring devices. Each channel has its own analog-to-digital converter, ensuring that all channels are sampled simultaneously without delay. At present, the input of the analog channel of the data acquisition instrument used for collision test is mainly to measure the voltage signal, but it is impossible to measure the amount of charge. It can perform shunt shunt inspection and automatic zero adjustment, and supports DALLAS sensor ID identification. Low-pass filtering according to the ISO standard and SAE standard CFC1000. In addition, the digital switch input has at least 12 channels, and each channel is isolated from each other.

3. Regardless of the data acquisition system used, the sampling frequency and recording time must first be set. The current record storage technology has been greatly developed. When the sampling frequency is usually 10 kHz or 20 kHz, the corresponding recording time can reach 100 seconds or 50 seconds, which can fully meet the test requirements.

4. Trigger method For conventional electrical measurement data acquisition systems, there is no problem in completing the acquisition task. But for a car crash test, not every test can collect data smoothly. Any minor mistake can cause data collection to fail. No matter at home or abroad, there have been acquisition failures. The most common reasons are that the data acquisition system is not triggered properly and the battery power is insufficient.
Whether the correct trigger signal is generated is related to the success or failure of the data acquisition. Because crash tests are not reproducible and costly, it is required to maximize the one-time success rate. For this reason, the products of various companies provide multiple insurance triggering methods. In addition to the digital triggering caused by the strip switch, some typical analog quantities (acceleration of the B-pillar and the dummy's head) are also used to generate the trigger. . According to the different trigger modes in the test, it can be divided into single trigger mode and dual trigger mode. The single trigger mode is also called the transient trigger mode, that is, the trigger signal is generated when the collision occurs, and data is recorded. At this time, the trigger can be generated by the collision squeezing the ribbon switch, or it can be automatically generated by the software because the analog value of a certain channel exceeds the set threshold. The former can get accurate zero time of collision, while the latter can only roughly estimate when it is zero time. The dual trigger mode is also called recording mode. Two trigger signals are used: the first trigger signal causes the data acquisition equipment to start recording, and the second trigger signal is used to indicate the zero time of the collision. The current recording time of the data acquisition equipment can exceed 50 seconds, and the time it takes for the vehicle to accelerate from the start to the collision wall generally does not exceed 30 seconds, so we can manually start the data acquisition system to start recording data a few seconds before the departure. This ensures that collision data is recorded even if no trigger signal is generated later. At present, some collision test institutions in the world use a single trigger mode, and some use a dual trigger mode. Comparing the two, the dual trigger mode has one more insurance than the single trigger mode, that is, it can guarantee that at least one trigger is generated. Therefore, you can be sure of the problem before the trigger signal is generated; In the trigger mode, it is impossible to know in advance whether the trigger signal is generated, and only to observe the indicator of the data acquisition instrument to determine after the collision. The double trigger mode has a long recording time and a large amount of data, but it is more comprehensive. The data including the acceleration phase is also recorded, which can be used to check whether the acceleration phase is stable.

5 channel range setting (amplitude level CAC)
The channel range CAC value is the actual selected range. It is numerically equal to the upper limit of the measurement range. It should not be too small or too large. It should be selected according to specific conditions and based on experience. Different collision speeds, different forms, and different positions, the corresponding acceleration range is also very different, may reach 5-10 times, so the channel range CAC is not constant. Too small CAC values will cut off some peaks of the test data and cause data loss, and too large CAC values will reduce the resolution. Taking the frontal impact test as an example, the Hybrid-III prosthesis in vivo sensor can be selected according to the recommended value of EuroNCAP (Table 1). The body sensors are mostly accelerometers. The CAC value of the accelerometer at the B-pillar can be 100-200g, and the CAC value of the accelerometer at the front of the A-pillar should be 500-1000g. For other parts, see Table 2. The sign of the channel signal should be determined according to the actual installation direction of the sensor in the dummy and the vehicle-mounted sensor. It should be pointed out that the positive and negative directions of the signal have an impact on the evaluation of the dummy's injury value and should be as far as possible in accordance with the norm. According to the regulations in SAEJ211, the positive directions of X, Y, and Z of the coordinate system are the front, right, and bottom of the vehicle, respectively. Therefore, in the frontal impact test, usually the acceleration measured in the X direction of the head is negative and the Z direction is positive; both the chest displacement and thigh force are negative.

6. Channel digital filtering frequency level (CFC value)
The CFC value indicates the digital filtering frequency level of the channel. It is better to set it to be greater than CFC 1000 or select unfiltered data during collection. When calculating the damage index, corresponding digital filtering is required according to requirements.

7. The sensor connector and ground acceleration sensor are generally piezoresistive (such as ENDEVCO, MEAS), and some use strain type (such as Kyowa). If the piezoelectric type is used, a charge / voltage converter needs to be separately connected to match the data acquisition instrument. Acceleration sensors are easily damaged in crash tests, which is determined by the strong impact characteristics and installation position of the test.
During the collision test, the data acquisition instrument, sensors and cables will be subjected to huge impacts. If not handled properly, light will cause interference signals, heavy will cause damage to connectors and signal loss. Therefore, the plug must be firm and easy to use. 7-pin LEMO self-locking connector is usually used. Some manufacturers use other types of plugs (such as 8-pin LEMO connectors and Tajimi connectors), which can not be used interchangeably and cause trouble. The dummy, the data collector and the battery should be grounded together. The pin definition of the LEMO plug (including the ground pin) is best unified and grounded together with the data acquisition case.

8. Battery maintenance For the needs of the vehicle, the data acquisition instrument comes with a lithium battery, and some also bring an extra set of spare batteries. In order to extend the life of the battery, it is best to completely discharge it every month, and the longest should not exceed three months. The battery can be fully charged and discharged in the built-in software.

Second, the development trend of data acquisition technology With the rapid development of electronic technology, the data collection technology of automobile crash test also shows a rapid, convenient, compact, flexible and intelligent development trend, which greatly improves the efficiency of the data acquisition process.
1. Interface technology between data acquisition instrument and computer:
At present, most of them adopt 10M BNC Ethernet interface or RS232 serial interface. With the rapid development of computer and communication technology, many notebook computers no longer support 10 Mbps Ethernet interface and no RS232 serial interface. Therefore, new interface communication methods, such as wireless network interface and USB interface, have been applied. Especially for the head-type Headform and leg-type Legform that will experience free flight pedestrian protection in the test, wireless communication technology has more advantages.
2. Advanced Sensor Information (ATI):
Combining sensor information with sensors. The latest version of DALLAS ID chip provides 4-16kB memory space to store sensor information, including sensor calibration information and related parameter settings. Therefore, not only the sensor ID information, but also more information about the sensor can be read directly from the test preparation database and transmitted to the sensor chip through the data collector, and this process is mutual. This makes the sensor and the dummy have good portability during use, that is, the same sensor can be easily shared between different laboratories and different data acquisition systems without the need for more parameter settings.
3. Better support ISO13499 data exchange format:
This will make the data more versatile and facilitate international exchanges.
4. Multi-locale support:
Especially the support of Chinese locale.
5. Data mining-integration of dummy (In-Dummy technology):
The dummy's sensor occupies many channels in the crash test, and the dummy's wiring harness has virtually increased the weight of the dummy and the troublesome wiring. The latest In-Dummy technology installs multiple data collection devices in the dummy, so that the sensors on the dummy can be collected by multiple data collection devices equipped on the dummy. These data acquisition devices are connected through the Hub and communicate with the computer through a digital interface uniformly. For example, DTS has developed the iDummy system in cooperation with FTSS, nxt system has been developed in cooperation with Denton, and M = bus has been developed by Messring in Germany. Data mining-dummy integration (In-Dummy technology) has become more and more mature after years of development and has been used more and more abroad. For example, the French PSA Group is in the market cultivation stage in China. In the long run, this technology will be widely used.


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