Research on miniature three-axis vibration sensor based on FBG

Objective Vibration measurement plays an essential role in machinery fault diagnosis and structural health monitoring, and vibration sensors are the most important tool in measuring equipment. Electrical vibration sensor technology is relatively mature, with the benefits of low cost, but there are drawbacks such as poor circuit stability, poor signal noise, and easy electromagnetic interference. In contrast, fiber Bragg grating vibration sensor has numerous advantages such as anti-electromagnetic interference, high and low temperature resistance, corrosion resistance, and so on, and is widely used in aerospace, large-scale structure monitoring, industrial propulsion, etc.

Methods The high-density tantalum block serves as the mass block, the nickel-titanium alloy serves as the elastic beam, and the ultra-short fiber grating serves as the sensitive element in the vibration sensor. The mass block fixed to the shrapnel will reciprocate as the sensor vibrates due to external forces. This reciprocating motion will stretch the fiber grating and cause axial strain, which causes the center wavelength to wander. The shift in the center wavelength can be used to track the vibration. The vibration sensor's packaging is finished, and the amplitude-frequency and sensitivity characteristics of the sensor are carefully investigated by developing the necessary packaging platform and test equipment.

Results and Discussions  The sensor has a broad frequency spectrum, high sensitivity and excellent lateral anti-interference performance. The frequency range for operation is 0 to 1 200 Hz. The characteristic frequencies are 1 850 Hz, 1 770 Hz and 1 860 Hz in the X, Y and Z directions, respectively. The sensitivities in the three directions are 77.37 pm/g, 80.73 pm/g, and 75.04 pm/g respectively, and lateral anti-interference is less than 5%.

Conclusions This article successfully designs an ultra-compact three-axis vibration sensor. The packaged sensor has considerable application possibilities in the satellite micro-vibration measurement due to its advantages of light weight, a wide operating frequency band, and high sensitivity.