阅读说明：本技术 旋转加速度计重力梯度敏感器冗余测量信号离线融合方法 (Offline fusion method for redundant measurement signals of gravity gradient sensor of rotating accelerometer ) 是由 李达 杨晔 李中 高巍 李城锁 于 2020-06-18 设计创作，主要内容包括：本发明涉及一种旋转加速度计重力梯度敏感器冗余测量信号离线融合方法,该方法通过离线处理的方法计算两组测量信号的傅里叶变换,对比两种信号在同一频率的相位角度差与预先设置阈值相比较,如果小于该阈值则保留该频点上的信号,如果大于该阈值则舍弃该频点上的信号,最后通过逆傅里叶变换得到重力梯度敏感器测量信号的最终输出结果。该方法较常规的平滑滤波,可有效提高对不相关噪声的抑制比,满足了高精度重力梯度测量的要求；该方法在重力梯度测量信号原始精度较低的情况下,可通过调整阈值的方式实现融合方法与两组测量信号的噪声情况相匹配,以得到最佳的重力梯度信号。(The invention relates to a method for fusing redundant measurement signals of a gravity gradient sensor of a rotary accelerometer off line, which calculates Fourier transform of two groups of measurement signals by an off-line processing method, compares the phase angle difference of the two signals at the same frequency with a preset threshold value, retains the signals on a frequency point if the phase angle difference is less than the threshold value, discards the signals on the frequency point if the phase angle difference is more than the threshold value, and finally obtains the final output result of the measurement signals of the gravity gradient sensor by inverse Fourier transform. Compared with the conventional smoothing filtering, the method can effectively improve the suppression ratio of irrelevant noise and meet the requirement of high-precision gravity gradient measurement; under the condition that the original accuracy of the gravity gradient measurement signal is low, the method can realize the matching of the fusion method and the noise condition of two groups of measurement signals by adjusting the threshold value so as to obtain the optimal gravity gradient signal.)

1. A method for fusing redundant measurement signals of a gravity gradient sensor of a rotary accelerometer off line comprises the following steps:

defining two groups of signals output by a rotating accelerometer type gravity gradient sensor at the same time as X and Y, and respectively carrying out Fourier transform on the X and Y to obtain frequency domain information F of the two groups of signals_xAnd F_yNamely:

wherein FFT represents Fourier transform;

step two, calculating the phase difference of the two groups of signals at the same frequency point, wherein the specific calculation formula is as follows:

in the formula, θ (k) is a phase difference at a frequency point k,. is a scalar product between vectors, | | is a vector modulo; wherein the value range of θ (k) is [0 °,180 ° ]whenthe trigonometric function is inverted;

step three, defining the frequency domain signal of the final output signal as F_ZFor the phase difference theta (k) on each frequency point and a preset threshold value theta₀By comparison, if θ (k) < θ₀Averaging two groups of frequency domain signals on the frequency point; if theta (k) is greater than or equal to theta₀And then abandoning the information on the frequency point, wherein the specific calculation formula is as follows:

step four, frequency domain information F of the final output signal_ZAnd performing inverse Fourier transform to obtain time domain information Z of the final output signal, wherein the specific calculation formula is as follows:

Z＝IFFT(F_Z) (5)

in the formula, IFFT represents inverse fourier transform.

2. According to claimThe off-line fusion method for the redundant measurement signals of the gravity gradient sensor of the rotary accelerometer in claim 1 is characterized in that: theta in step three₀Is 5 deg.

Technical Field

The invention belongs to the technical field of measurement signal processing of a gravity gradient sensor of a rotary accelerometer, and particularly relates to an offline fusion method of redundant measurement signals of the gravity gradient sensor of the rotary accelerometer.

Background

The gravity gradiometer of the rotary accelerometer type is an instrument for continuously measuring the change of the micro gravity gradient on the earth surface. As shown in fig. 1, the gravity gradient measurement component as the core sensor modulates the gravity gradient tensor component to a frequency twice the system rotation frequency by means of mechanical rotation based on the accelerometer position difference measurement principle, and the relationship between the accelerometer output and the gravity gradient tensor component can be expressed as follows:

(a₁+a₃)-(a₂+a₄)＝2R(_xx-_yy)sin2ωt+4R_xycos2ωt (1)

where a1, a2, a3, a4 are the outputs of four accelerometers, R is the distance from the center of mass of the accelerometer to the center of rotation,_xx、_yy、_xyis the gravitational gradient tensor component and ω is the rotational angular velocity of the rotating device. Synchronously demodulating the accelerometer combined signal output by the system at the frequency of 2 omega to obtain a final gravity gradient tensor signal_xx-_yyAnd_xy。

because the gravity gradient signal is very weak, the gravity gradient measurement signal usually contains a lot of noise, and in order to obtain a more accurate gravity gradient signal, two groups of accelerometer components are usually arranged in the gravity gradient sensor, each group comprises 4 accelerometers, and the total number of the accelerometers is 8. Two groups of accelerometer assemblies share one rotating mechanism, the phase angle of rotation is 45 degrees, and gravity gradient signals are measured simultaneously. Through data comparison, a large amount of noise in two groups of gravity gradient measurement signals is considered to be irrelevant, and the rejection ratio of the traditional average fusion mode to the irrelevant noise is not high, so that an effective signal extraction method needs to be established, and the irrelevant noise in the two groups of signals is filtered out, so that the measurement accuracy of the gravity gradient signals is improved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an off-line fusion method for redundant measurement signals of a gravity gradient sensor of a rotary accelerometer.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a method for fusing redundant measurement signals of a gravity gradient sensor of a rotary accelerometer off line comprises the following steps:

defining two groups of signals output by a rotating accelerometer type gravity gradient sensor at the same time as X and Y, and respectively carrying out Fourier transform on the X and Y to obtain frequency domain information F of the two groups of signals_xAnd F_yNamely:

wherein FFT represents Fourier transform;

step two, calculating the phase difference of the two groups of signals at the same frequency point, wherein the specific calculation formula is as follows:

in the formula, θ (k) is a phase difference at a frequency point k,. is a scalar product between vectors, | | is a vector modulo; wherein the value range of θ (k) is [0 °,180 ° ]whenthe trigonometric function is inverted;

step three, defining the frequency domain signal of the final output signal as F_ZFor the phase difference theta (k) on each frequency point and a preset threshold value theta₀By comparison, if θ (k) < θ₀Averaging two groups of frequency domain signals on the frequency point; if theta (k) is greater than or equal to theta₀And then abandoning the information on the frequency point, wherein the specific calculation formula is as follows:

step four, frequency domain information F of the final output signal_ZAnd performing inverse Fourier transform to obtain time domain information Z of the final output signal, wherein the specific calculation formula is as follows:

Z＝IFFT(F_Z) (5)

in the formula, IFFT represents inverse fourier transform.

Further: theta in step three₀Is set at 5 °

The invention has the advantages and positive effects that:

1. compared with the conventional smoothing filtering, the method can effectively improve the suppression ratio of irrelevant noise and meet the requirement of high-precision gravity gradient measurement.

2. Under the condition that the original accuracy of the gravity gradient measurement signal is low, the invention can realize that the fusion method is matched with the noise condition of two groups of measurement signals by adjusting the threshold value so as to obtain the optimal gravity gradient signal.

Drawings

FIG. 1 is a schematic view of a measurement principle of a rotating accelerometer type gravity gradient sensor;

FIG. 2 is a flow chart of the offline fusion method of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments, which are illustrative, not restrictive, and the scope of the invention is not limited thereto.

A method for fusing redundant measurement signals of a gravity gradient sensor of a rotary accelerometer off line refers to fig. 2, the method calculates Fourier transformation of two groups of measurement signals by an off-line processing method, compares the phase angle difference of the two signals at the same frequency with a preset threshold value, if the phase angle difference is smaller than the threshold value, the signals on the frequency point are retained, if the phase angle difference is larger than the threshold value, the signals on the frequency point are discarded, and finally, the final output result of the measurement signals of the gravity gradient sensor is obtained by inverse Fourier transformation, and the method specifically comprises the following steps:

defining two groups of signals output by a rotating accelerometer type gravity gradient sensor at the same time as X and Y, and respectively carrying out Fourier transform on the X and Y to obtain frequency domain information F of the two groups of signals_xAnd F_yNamely:

wherein FFT represents Fourier transform;

step two, calculating the phase difference of the two groups of signals at the same frequency point, wherein the specific calculation formula is as follows:

in the formula, θ (k) is a phase difference at a frequency point k, and | | | is a vector modulo product between vectors. Wherein the value range of θ (k) is [0 °,180 ° ]whenthe trigonometric function is inverted;

step three, defining the frequency domain signal of the final output signal as F_ZFor the phase difference theta (k) on each frequency point and a preset threshold value theta₀By comparison, can be compared with₀Set to 5 °; if theta (k) < theta₀Averaging two groups of frequency domain signals on the frequency point; if theta (k) is greater than or equal to theta₀And then abandoning the information on the frequency point, wherein the specific calculation formula is as follows:

step four, frequency domain information F of the final output signal_ZAnd performing inverse Fourier transform to obtain time domain information Z of the final output signal, wherein the specific calculation formula is as follows:

Z＝IFFT(F_Z) (5)

in the formula, IFFT represents inverse fourier transform.

In conclusion, the method can filter out irrelevant noise of two groups of gravity gradient signals simultaneously measured by the gravity gradient sensor, thereby improving the measurement precision of the gravity gradient signals.

Although the embodiments and figures of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and figures.