A Study Of Low-frequency Standard Vibration Table Systems And Vibration Calibration Technology

Low-frequency vibration sensors have gained increasing applications in seismicobservations, civil engineering and construction, mechanical and vehicle engineering,energy and mining engineering. These sensors require calibration on a low-frequencystandard calibration system, and the low-frequency standard vibration table is anessential part of such system. The design and manufacturing of the low-frequencystandard vibration table often indicates the level of national low-frequency vibrationmeasurements. During the calibration, the vibration table is used to generate standardvibration signal, which is usually a sinusoidal signal. However, the calibrationexcitation signal tends to develop from a steady-state sinusoidal signal to a randomsignal. Currently, calibrations of low-frequency vibration sensors are usually carried outin laboratories, and there is a need for on-site calibrations using the vibration sensors.This paper focuses on the following studies:1. Author studied the control techniques of the low-frequency standard vibrationtable. Author established a mathematical model for the low-frequency standardvibration table, designed a portable low-frequency standard vibration table, and carriedout tests on the designed system. Test results show that the frequency of the accelerationsignal generated by this table can be as low as0.5Hz, and the frequency of the speedsignal can be as low as0.1Hz, which can satisfy the general measurement requirementsusing low-frequency vibration sensors. It can also satisfy the measurement requirementsof the province-level measurement institutions, vibration sensor manufactures, and otherorganizations using low-frequency vibration sensors.2. Author studied the calibration methods using seismic waves as excitationsignals, and explored the method of generating seismic waves on a low-frequencystandard vibration table. Author reproduced the seismic waves on the low-frequencystandard vibration table at the Institute of Engineering Mechanics, China EarthquakeAdministration. In most cases, the correlation between the reproduced seismic wavesand the recorded original seismic waves is above0.95. Author then used the seismicwaves as the excitation signal and performed the calibration of the sensor. Authorcompared our calibration results with those obtained using the laser absolute method,and the results are satisfactory.3. Author investigated the on-site calibrational method using vibration sensors.Although the self-calibration method has been using in the past, there was no detailedanalysis on the system. In this work, four types of internal calibration-coil sensors werecalibrated using the self-calibration method and the laser interferometry vibrationabsolute calibration method. The results show that the two methods give identicalresults in the low-frequency range (below10Hz) and there are some discrepancies in thehigh-frequency range. Author used the passive servo vibration sensors as an exampleand carried out systematic analysis on the mathematical relationship of the self-calibrated sensors. Author found that the back electromotive force and inductance(both self and mutual) are the main cause of the deviations.This paper is organized as follows: the background of this study is elaborated inChapter1. The aforementioned key study points are discussed in Chapter2-5, whichconstitute the main body of the paper. The future work is prospected in Chapter6. Inparticular, a development direction for the low-frequency standard vibration table and apractical implementation method for the on-site calibration system are proposed.