ON-SITE RECIPROCITY CALIBRATION METHOD FOR PIEZOELECTRIC ACCELEROMETER

Abstract

An on-site reciprocity calibration method for a piezoelectric accelerometer, including a vibration test and a reciprocity test. In the vibration test, a sine excitation with a corresponding frequency and amplitude is provided by a vibration exciting device to the piezoelectric accelerometer fixed on a motion plane, and output signals of a drive port and a signal port of the reciprocal piezoelectric accelerometer are collected by a data acquisition device. In the reciprocity test, a sine voltage excitation is provided by a signal generator to the drive port, and then an excitation signal and an output signal of the signal port are collected by the data acquisition device. An amplitude ratio of the two signals is obtained based on signal sine-fitting. Finally, the on-site calibration is enabled according the sensitivity amplitude ratio obtained in the vibration test and the sensitivity amplitude product obtained in the reciprocity test.

Claims

1. An on-site calibration method for a reciprocal piezoelectric accelerometer, comprising: (S1) fixing an installation base of the reciprocal piezoelectric accelerometer on a motion plane of a vibration exciting device; and outputting, by the vibration exciting device, a sinusoidal vibration excitation at a ? octave band under a condition that an output amplitude of the vibration exciting device is greater than a minimum signal-to-noise ratio of an output signal of the reciprocal piezoelectric accelerometer; (S2) under the sinusoidal vibration excitation, acquiring, by a data acquisition device, a first signal output from a drive port of the reciprocal piezoelectric accelerometer and a second signal output from a signal port of the reciprocal piezoelectric accelerometer, and sending the first signal and the second signal to an upper computer for signal processing; (S3) based on a signal sine-fitting method, acquiring an amplitude of the first signal and an amplitude of the second signal; and calculating a ratio of the amplitude of the first signal to the amplitude of the second signal, so as to acquire a sensitivity amplitude ratio of the drive port and the signal port; (S4) placing the reciprocal piezoelectric accelerometer on a stable work plane, and connecting an output port of a signal generator to the drive port of the reciprocal piezoelectric accelerometer; and outputting a sinusoidal voltage excitation at the ? octave band and an output voltage of 1-5 V; (S5) under the sinusoidal voltage excitation, acquiring, by the data acquisition device, an electric excitation signal of the drive port and a third signal output from the signal port of the reciprocal piezoelectric accelerometer, and sending the electric excitation signal and the third signal to the upper computer for signal processing; (S6) based on the signal sine-fitting method, acquiring an amplitude of the electric excitation signal and an amplitude of the third signal; and calculating a ratio of the amplitude of the electric excitation signal to the amplitude of the third signal, so as to acquire a sensitivity amplitude product of the drive port and the signal port; and (S7) according to the sensitivity amplitude ratio and the sensitivity amplitude product, calculating a sensitivity amplitude of the drive port and a sensitivity amplitude of the signal port, so as to realize on-site calibration for the reciprocal piezoelectric accelerometer, and saving and displaying sensitivity calibration results.

2. The on-site calibration method of claim 1, wherein signal U.sub.1(t.sub.j) and signal U.sub.2(t.sub.j) collected by two channels of the data acquisition device at time t.sub.j are fitted by the following sine-approximation methods, respectively: $\begin{array}{cc}\{\begin{array}{c}{U}_1\left(t_j\right)=A_1\cos \left({?}_v{t}_j\right)-B_1\sin \left({?}_v{t}_j\right)+C_1\\ U_2\left(t_j\right)=A_2\cos \left({?}_v{t}_j\right)-B_2\sin \left({?}_v{t}_j\right)+C_2\end{array};& \left(1\right)\end{array}$ wherein ?.sub.v represents a vibration angular frequency; parameters A.sub.1, B.sub.1, C.sub.1, A.sub.2, B.sub.2 and C.sub.2 are sine-fitting coefficients to be solved, and are obtained by solving corresponding N equations, respectively; and a peak value of the signal U.sub.1(t.sub.j) is obtained according to parameters A.sub.1 and B.sub.1, and a peak value of the signal U.sub.2(t.sub.j) is obtained according to parameters A.sub.2 and B.sub.2, represented by: $\begin{array}{cc}\{\begin{array}{c}\widehat{S_1}=\sqrt{A_1^2+B_1^2}\\ \widehat{S_2}=\sqrt{A_2^2+B_2^2}\end{array}.& \left(2\right)\end{array}$

3. The on-site calibration method of claim 1, wherein the sensitivity amplitude S.sub.a1 of the drive port and the sensitivity amplitude S.sub.a2 of the signal port acquired in the on-site calibration of the reciprocal piezoelectric accelerometer are determined by an amplitude ratio u.sub.1 of the first signal to the second signal and an amplitude ratio u.sub.2 of the electric excitation signal to the third signal, represented by: $\begin{array}{cc}\{\begin{array}{c}{u}_1=\frac{\widehat{S_1^{}}}{\widehat{S_2^{}}}=\frac{S_{a1}}{S_{a2}}\\ u_2=\frac{\widehat{S_1^{}}}{\widehat{S_2^{}}}=c{S}_{a1}{S}_{a2}\end{array};& \left(3\right)\end{array}$ wherein represents the amplitude of the first signal, and represents the amplitudes of the second signal; represents the amplitude of the electric excitation signal, and represents the amplitude of the third signal; c represents a self-calibration coefficient which is determined by structure parameters of the reciprocal piezoelectric accelerometer and is a known value; and the sensitivity amplitude S.sub.a1 and the sensitivity amplitude S.sub.a2 are obtained as follows: $\begin{array}{cc}\{\begin{array}{c}{S}_{a1}=\sqrt{\frac{u_1{u}_2}{c}}\\ S_{a2}=\sqrt{\frac{u_2}{c{u}_1}}\end{array}.& \left(4\right)\end{array}$

4. An on-site calibration device for a reciprocal piezoelectric accelerometer by using the on-site calibration method of claim 1, comprising: a vibration exciting device; the reciprocal piezoelectric accelerometer; a data acquisition device; a signal generator; and a signal processing and displaying unit; wherein a work table of the vibration exciting device is configured to provide a planar motion of any trajectory; the reciprocal piezoelectric accelerometer is fixed on the work table of the vibration exciting device, such that the reciprocal piezoelectric accelerometer and the work table have the same motion characteristics; in a vibration test, the vibration exciting device is configured to be driven by a first sinusoidal excitation generated by the signal generator to provide a sinusoidal vibration excitation to the reciprocal piezoelectric accelerometer; the data acquisition device is configured to acquire a first signal output from a drive port of the reciprocal piezoelectric accelerometer and a second signal output from a signal port of the reciprocal piezoelectric accelerometer; the signal processing and displaying unit is configured to process the first signal and the second signal and store measurement results; and in a reciprocity test, the signal generator is configured to output a second sinusoidal excitation to the drive port of the reciprocal piezoelectric accelerometer; the data acquisition device is configured to acquire an excitation signal and a third signal output from the signal port of the reciprocal piezoelectric accelerometer; and the signal processing and displaying unit is configured to process the excitation signal and the third signal, and save and display calibration results.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 schematically shows an on-site calibration device according to an embodiment of the present disclosure.

[0044] FIG. 2 is a flowchart of an on-site reciprocity calibration device for piezoelectric accelerometers according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0045] In order to solve the problems that the existing vibration sensors have complex system, high cost and poor flexibility, and cannot satisfy the on-site calibration, the present disclosure provides an on-site reciprocity calibration device for piezoelectric accelerometers. In the present disclosure, the sensitivity amplitude ratio and the sensitivity amplitude product of two ports of a reciprocal piezoelectric accelerometer are measured respectively in two tests, and are further applied to the on-site high-precision calibration within a frequency range of 5-4000 Hz. The present disclosure will be further described below with reference to the embodiments.

[0046] Referring to FIG. 1, an on-site calibration device is provided, which includes: a vibration exciting device 1, a reciprocal piezoelectric accelerometer 2, a data acquisition device 3, a signal generator 4 and a signal processing and displaying unit 5; in a vibration test, the vibration exciting device 1 is driven by a sinusoidal excitation of the signal generator 4, and is configured to provide the sinusoidal excitation for the reciprocal piezoelectric accelerometer 2 arranged on a work table; the data acquisition device 3 is configured to acquire a first signal output from a drive port of the reciprocal piezoelectric accelerometer 2 and a second signal output from a signal port of the reciprocal piezoelectric accelerometer 2; the signal processing and displaying unit 5 is configured to process the first signal and the second signal and save measuring results; in a reciprocity test, the signal generator 4 is configured to output a sinusoidal excitation to the drive port of the reciprocal piezoelectric accelerometer 2; the data acquisition device 3 is configured to acquire an excitation signal and a third signal output from the signal port of the reciprocal piezoelectric accelerometer 2; and the signal processing and displaying unit 5 is configured to process the third signal and the excitation signal, and save and show final calibration results.

[0047] Referring to FIG. 2, an on-site calibration method for a reciprocal piezoelectric accelerometer is performed through the following steps.

[0048] (S1) An installation base of the reciprocal piezoelectric accelerometer is fixed on a motion plane of the vibration exciting device. And a sinusoidal vibration excitation at a ? octave band, is output by the vibration exciting device under a condition that an output amplitude of the vibration exciting device is greater than a minimum signal-to-noise ratio of an output signal of the reciprocal piezoelectric accelerometer.

[0049] (S2) Under the sinusoidal vibration excitation, a first signal output from the drive port of the reciprocal piezoelectric accelerometer and a second signal output from the signal port of the reciprocal piezoelectric accelerometer are acquired by a data acquisition device, and the first signal and the second signal are sent to an upper computer for signal processing.

[0050] (S3) Based on a signal sine-fitting method, an amplitude of the first signal and an amplitude of the second signal is acquired, and a ratio of the amplitude of the first signal to the amplitude of the second signal is calculated, so as to acquire a sensitivity amplitude ratio of the signal port.

[0051] (S4) The reciprocal piezoelectric accelerometer is placed on a stable work plane, and an output port of the signal generator is connected to the drive port of the reciprocal piezoelectric accelerometer. And a sinusoidal voltage excitation is output at ? octave band and an output voltage of 1-5V.

[0052] (S5) Under the sinusoidal voltage excitation, an electric excitation signal of the drive port and a third signal output from the signal port of the reciprocal piezoelectric accelerometer are acquired by the data acquisition device, and the electric excitation signal and the third signal are sent to the upper computer for signal processing.

[0053] (S6) Based on the signal sine-fitting method, an amplitude of the electric excitation signal and an amplitude of the third signal are acquired. A ratio of the amplitude of the electric excitation signal to the amplitude of the third signal is calculated, so that a sensitivity amplitude product of the drive port and the signal port are acquired.

[0054] (S7) According to the sensitivity amplitude ratio and the sensitivity amplitude product, a sensitivity amplitude of the drive port and a sensitivity amplitude of the signal port are calculated, so that on-site calibration for the reciprocal piezoelectric accelerometer is realized, and sensitivity calibration results are saved and displayed.

[0055] Parameters of the device of the present disclosure are as follows. A high frequency vibration table has a frequency range of 5?20000 Hz and a maximum peak acceleration of 20 g. The reciprocal piezoelectric accelerometer is an accelerometer with a shear type structure and two ports, and is suitable for a low and medium frequency range. The signal generator is a waveform generator with a maximum output frequency of 60 MHz, a sampling rate of 200 MSa/s and a vertical resolution of 14 bits. And the data acquisition device is a portable acquisition equipment with 24-bit ADC and a sampling rate of 102.4 KHz.

[0056] In order to verify an accuracy of the on-site calibration method for a reciprocal piezoelectric accelerometer, the present disclosure realizes the on-site calibration with high accuracy for the reciprocal piezoelectric accelerometer within a frequency range of 5?4000 Hz. Table 1 shows calibration results for the reciprocal piezoelectric accelerometer within the frequency range of 5?4000 Hz of the present disclosure and a laser interferometry respectively. According to results of the Table 1, measuring results of the present disclosure are similar to measuring results of the laser interferometry. A maximum relative deviation of a sensitivity amplitude S.sub.a1 of the signal port is about 2%, and a maximum relative deviation of a sensitivity amplitude S.sub.a2 of the drive port is about 4%.

TABLE-US-00001 TABLE 1 Measuring results of plane motion displacement by the on-site calibration method and the laser interferometry method Frequency On-site calibration Laser interferometry (Hz) S.sub.?1(pC/g) S.sub.?2(pC/g) S.sub.?1(pC/g) S.sub.?2(pC/g) 5 24.84 44.90 25.23 45.76 10 24.71 44.69 25.10 45.35 16 24.70 44.49 24.88 45.02 25 24.46 44.07 24.85 44.84 40 24.37 43.95 24.65 44.81 80 24.37 44.07 24.72 44.65 160 24.39 43.88 24.69 44.48 250 24.46 43.99 24.72 44.66 400 24.61 44.30 24.76 45.20 630 24.57 44.23 24.52 45.48 800 24.57 44.21 24.70 45.03 1000 24.83 44.70 24.78 45.71 2000 25.92 46.52 25.73 48.29 3000 27.56 48.78 27.17 50.70 4000 28.61 50.39 28.57 51.64

[0057] Described above are only detailed description of embodiments of this application, and are not intended to limit this application in any form. A series of optimizations, improvements and modifications can be made by those skilled in the art based on this application. It should be noted that those optimizations, improvements and modifications made without departing from the spirit of this application shall fall within the scope of this application defined by the appended claims.