Study Of Micro-ultra-low Frequency Absolute Vibration Sensors

Vibration is a form of movement of the object. Absolute vibration means the vibration which has no static reference point relative to inertial space, such as ship jolt, airplane turbulence, high building,ocean plat roof,great rotating machine(such as water turbine) and bridges' vibration, seismic wave, etc.All the vibration presented above have two common characteristics. First, there is no static reference point. It is difficult to detect the absolute vibration information using relative measurement. At present, the inertial transducer is widely used in absolute vibration detection. Second, the vibration frequency is very low (about 1Hz). It is a rigor requirement for inertial transducer's low-frequency-characteristic. And the output signal from the transducer is corrupted by interferences at ultra-low frequency band (below 1Hz) since it has default of its own machine structure. As a result, the acquired vibration signals couldn't reflect the real situations. So the ultra-low frequency absolute vibration detection is a difficult problem in engineering measurement field. In this paper, the "high-frequency-suppression and low-frequency-lifting" compensation method was presented based on the analysis of the inertial sensor with " mkc " structure. Then the compensation network and amplitude-frequency characteristic were optimized. It properly overcomes the sensor's inherent defect—bad low frequency characteristic. And the miniaturization of the sensor was realized. At the meantime, the software and hardware of the vibration data acquisition and analysis were developed.Chapter one briefly introduced vibration detection and pointed out the significance and difficulty of the ultra-low absolute vibration detection. The present research status on ultra-low absolute vibration detection was also surveyed.Chapter two summarized the three types of main inertial transducer used in absolute vibration detection: piezoelectric sensor,fiber-optic sensor and magnetoelectric sensor. Base on the study of their structures ,frequency characteristics and SNR, both the advantages and disadvantages were presented. And finally the inertial magnetoelectric velocity transducer was selected which has high SNR as the basis of further research.In chapter three, the transfer function was put forward based on the mechanical model of magnet-electrical absolute vibration transducer with " mkc " structure, and then analyzed the transducer's natural defect. According to the character of second order...