Industries

Vibration Measuring on the Headlight of Subway

Since Beijing subway vehicle operated in Sep., 2007, the frequent bulbs explosions were bothering the officials constantly. More strangely, the explosions of left headlight installed on exit door occurred much more often compared with the right headlight of the vehicle body. 
Based on the results of our vibration measuring test, technical engineers from Bulb Company considered that the headlights had to restart during vibration which caused breaking of voltaic arc. At last, they concluded, the valid lifespan of bulbs is largely subject to the vibration of the actual installation environment.

 
    
 
In fact, the bulb company adopted AVANT MI-7008 DAQ and Signal Analyzer (produced by Hangzhou ECON Technologies Co., Ltd.), installed relative software and several acceleration sensors to do the vibration measurement.
Installing a triaxial sensor on the headlight,
X axis: vertical direction of the vehicle; Y axis: horizontal direction of the vehicle;
Z axis: forwarding direction of the vehicle. (Details are shown above).
Installing two unidirectional sensors on its door and body,
X axis: vertical direction of the vehicle;
Y axis: horizontal direction of the vehicle;
The sensors of X axis, Y axis and Z axis on the headlight are separately connected to AVANT MI-7008 Input 1, Input 2 and Input 3; the sensors of X axis and Y axis on the door (body) are connected to Input 4 and Input 5.

 
     
Due to the limited onsite subway testing conditions, repetitive tests are not available. So firstly, we record the test data via AVANT MI-7008 on the spot, then use off-line software to do analysis and generate test reports.
Recorded signal in time domain:
Data recording of time-domain signal while the subway vehicle moving on the actual orbit;
Recording duration: 1700s
The time domain window tells us that the maximum amplitude of vibration is about 0.15g when the vehicle runs on the orbit.

 

 
Choose several segments of data, and then do spectrum analysis:
Set analysis parameters: frame time: 12.80s, frame in length: 16384 bit; Hanning window; frequency domain 10 frames exponential averaging
The amplitude is mainly about 0.035g, the maximum is 0.039g.
Choose the time domain signal.

 

 
Spectrum signal

Enlarge the part when the vehicle is vibrating heavily.


 
Spectrum above shows us that the vibration energy peaks at the frequency point 1 Hz, which indicates the obvious vibration of sensor.
During the test, AVANT MI-7008 DAQ and signal analyzer displays its unique features of high reliability and high accuracy. It simplifies the whole testing process with popular ICP sensors and built-in battery structure, which makes it unnecessary to connect with power source on the spot. Additionally, getting the corresponding reports immediately is available from the off-line software. The off-line software is capable of analyzing record data to acquire the analysis results and generate test report; the whole playback analysis is finished in a very short time.