CN113777671B - Magnetic field effect evaluation method, device and system of rotary gravity gradiometer - Google Patents
Magnetic field effect evaluation method, device and system of rotary gravity gradiometer Download PDFInfo
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- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
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Abstract
The invention discloses a magnetic field effect evaluation method, a device and a system of a rotary gravity gradiometer, belonging to the field of gravity gradient measurement and comprising the following steps: n pairs of magnetometers arranged on the turntable are utilized to measure the magnetic field intensity in real time, and the phase difference of the paired magnetometers is 180 degrees; for each pair of magnetometers, calculating magnetic gradients in three directions, demodulating to obtain magnetic gradient components in all directions and all channels, and advancing the phase of a demodulation signal used by the magnetometer by phi (phi is the phase angle difference between the magnetometer and the first accelerometer when the counterclockwise direction is taken as the positive time) compared with the phase of the demodulation signal of the gradiometer; for each accelerometer, on each channel, calculating gradient influence corresponding to each channel according to magnetic coefficients in three directions and magnetic gradient components in three directions; adding the gradient influences of the four accelerometers to obtain a magnetic field contribution; the average of the magnetic field contributions was taken as the magnetic field noise evaluated. The invention can accurately evaluate the magnetic field noise of the rotary gravity gradiometer in the gravity gradient measurement process.
Description
Technical Field
The invention belongs to the field of gravity gradient measurement, and particularly relates to a magnetic field effect evaluation method, device and system of a rotary gravity gradiometer.
Background
The rotary gravity gradiometer is a precision instrument for detecting gravity gradient, the structure of which is shown in figure 1, a sensitive probe of the rotary gravity gradiometer is formed by combining four high-precision accelerometers 2, a combined signal is obtained by subtracting the output of the other two accelerometers from the rotation modulation of a rotary table 1, and the output of the instrument is obtained by demodulating the demodulated signal by rotating frequency doubling.
Since the accelerometer mostly performs feedback through magnetic force or electrostatic force, it is susceptible to interference of magnetic field, further affecting the measurement accuracy of gravity gradient. At present, no relevant patent and literature in China proposes a method for eliminating the influence of a magnetic field on a gradiometer, and foreign literature reports only mention the influence of the magnetic field on the gradiometer to be considered, but do not describe how to analyze and subtract.
Therefore, in order to ensure that the signals detected by the gradiometer are gradient signals and avoid the interference of ambient magnetic field noise, a method for evaluating and deducting the influence of the magnetic field on the output of the gradiometer is urgently needed.
Disclosure of Invention
The invention provides a magnetic field effect evaluation method, a device and a system of a rotary gravity gradiometer, aiming at accurately evaluating magnetic field noise of the rotary gravity gradiometer in the gravity gradient measurement process so as to deduct the magnetic field noise and obtain accurate gravity gradient output.
To achieve the above object, according to one aspect of the present invention, there is provided a magnetic field effect evaluation method for a rotary gravity gradiometer comprising a turntable, and four accelerometers mounted on the turntable, the method comprising:
measuring the magnetic field intensity in real time by using n pairs of magnetometers arranged on a turntable; each magnetometer and the accelerometer are positioned on the same circumference and are not overlapped with each other, and the phase difference between the two magnetometers in each pair of magnetometers is 180 degrees; n is a positive integer;
respectively evaluating corresponding magnetic field contributions according to the measurement results of each pair of magnetometers to obtain n magnetic field contributions in total, and taking the average value of the n magnetic field contributions as the magnetic field noise obtained by evaluation;
the evaluation of the magnetic field contribution corresponding to each pair of magnetometers includes:
(S1) calculating the magnetic gradients in the x, y and z directions according to the measurement results of the two magnetometers, and demodulating the magnetic gradients in all directions respectively by using the magnetic field demodulation signals of the sine channel and the cosine channel to obtain the magnetic gradient components in all directions and all channels; the phase of the magnetic field demodulation signal is advanced by phi compared with the phase of the demodulation signal of the rotary gravity gradiometer, wherein phi is the phase angle difference between one magnetometer and the first accelerometer when the anticlockwise direction is taken as positive time;
(S2) for each accelerometer, on each channel, multiplying the magnetic coefficients of the accelerometer in three directions by the magnetic gradient components of the accelerometer in three directions on the channel correspondingly, and then adding the multiplication to obtain the gradient influence of the magnetic field on the accelerometer on the sine channel and the cosine channel respectively;
(S3) the gradient contributions of the four accelerometers on each channel are summed to obtain the components of the magnetic field contribution on the sine and cosine channels.
In some alternative embodiments, n ═ 1; further preferably, Φ is 45 °.
In some alternative embodiments, n-2; further preferably, the phase angle difference phi for the two pairs of magnetometers is 45 deg. and 135 deg., respectively.
Further, the method for evaluating the magnetic field effect of the rotary gravity gradiometer provided by the invention further comprises the following steps: and respectively subtracting the components of the magnetic field noise in the sine channel and the cosine channel from the sine channel output result and the cosine channel output result of the rotary gravity gradiometer so as to subtract the magnetic field noise.
According to another aspect of the present invention, there is provided a magnetic field effect evaluation apparatus for a rotary gravity gradiometer comprising a turntable, and four accelerometers mounted on the turntable, the apparatus comprising: the system comprises n pairs of magnetometers arranged on a turntable, n evaluation modules connected with the n pairs of magnetometers respectively, and an output module;
in the n pairs of magnetometers, each magnetometer and the accelerometer are positioned on the same circumference and are not overlapped with each other, and the phases of the two magnetometers in each pair of magnetometers are different by 180 degrees; n is a positive integer;
the n evaluation modules are respectively used for evaluating corresponding magnetic field contributions according to the measurement results of each pair of magnetometers to obtain n magnetic field contributions;
an output module for taking the average of the n magnetic field contributions as the magnetic field noise obtained by the evaluation;
the evaluation module comprises: a first combination unit, a phase conversion unit, a demodulation unit, a second combination unit and a third combination unit;
the first combination unit is used for calculating the average value of the magnetic field intensity measured by the two magnetometers in the x direction, the y direction and the z direction to obtain the magnetic gradient in the x direction, the y direction and the z direction;
the phase conversion unit is used for advancing the phase of the demodulation signal of the rotary gravity gradiometer by phi to obtain a magnetic field demodulation signal; phi is the phase angle difference between one magnetometer and the first accelerometer when the counterclockwise direction is taken as positive;
the demodulation unit is used for demodulating the magnetic gradients in all directions respectively by using the magnetic field demodulation signals of the sine channel and the cosine channel to obtain the magnetic gradient components in all directions and all channels;
the second combination unit is used for multiplying the magnetic coefficients of the accelerometer in the three directions on each channel by the magnetic gradient components of the accelerometer in the three directions on the channel correspondingly and then adding the multiplied magnetic coefficients to obtain the gradient influence of the magnetic field on the accelerometer on the sine channel and the cosine channel respectively;
and the third combination unit is used for adding the gradient influences of the four accelerometers on each channel to obtain the components of the magnetic field contributions on the sine channel and the cosine channel.
According to yet another aspect of the present invention, there is provided a gravity gradient measurement system comprising: the invention provides a rotary gravity gradiometer, a magnetic field effect evaluation device of the rotary gravity gradiometer and a magnetic field noise deduction device;
a rotary gravity gradiometer for measuring magnetic field gradients;
the magnetic field effect evaluation device is used for evaluating magnetic field noise in the rotary gravity gradiometer;
and the magnetic field noise deduction device is used for deducting the components of the magnetic field noise in the sine channel and the cosine channel from the sine channel output result and the cosine channel output result of the rotary gravity gradiometer respectively so as to deduct the magnetic field noise.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
according to the invention, the magnetometer is arranged on the rotary table of the rotary gravity gradiometer, the magnetic field change on the rotary table is measured in real time, the magnetic field intensity measured by the magnetometer is demodulated after the phase conversion is carried out on the demodulation signal of the gradiometer according to the position relation between the magnetometer and the accelerometer, and the magnetic field input is obtained in real time; further calculating to obtain the contribution of the magnetic field to the output of each accelerometer according to the magnetic coefficient of each accelerometer in each direction; and finally, combining the calculation results of the four accelerometers, accurately calculating the magnetic field noise of the whole rotary gravity gradiometer, and finishing the evaluation of the influence of the magnetic field on the instrument. Finally, the component of the magnetic field noise on the channel is correspondingly subtracted from the output of the two channels of the rotary gravity gradiometer, so that the magnetic field noise in the output of the gradiometer can be subtracted, and the measurement precision of the gravity gradient is effectively improved.
Drawings
FIG. 1 is a schematic structural diagram of a conventional rotary gravity gradiometer;
FIG. 2 is a schematic diagram of a magnetic field effect evaluation method for a rotary gradiometer according to an embodiment of the invention;
FIG. 3 is a schematic diagram of the response of an accelerometer to three directions of a magnetic field according to an embodiment of the invention;
the same reference numbers will be used throughout the drawings to refer to the same elements or structures, wherein:
1 is a turntable, 2 is an accelerometer, and 3 is a three-axis magnetometer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In order to solve the technical problem that the gravity gradient output of the conventional rotary gravity gradiometer is influenced by the interference of a magnetic field, the invention provides a magnetic field effect evaluation method, a device and a system of the rotary gravity gradiometer, and the overall thought of the method is as follows: one or more pairs of three-axis magnetometers are installed at a specific position of the rotary gradiometer, the magnetic field change on the turntable is measured in real time, three channel outputs of each pair of magnetometers are combined to eliminate a common-mode magnetic field, a magnetic gradient is obtained, and the plurality of pairs of magnetometers can effectively reduce the measurement error; after the magnetic gradient output is obtained, the reference demodulation signal is subjected to phase advancing or delaying processing by utilizing a specific phase relation, so that the conversion of a coordinate system is realized; considering the influence of a magnetic field on the accelerometers in three directions, establishing a magnetic field vector input model of the accelerometers, respectively calculating the contribution of the magnetic field to the outputs of the four accelerometers by combining a magnetic field test result and magnetic coefficients of the accelerometers, and performing combined calculation on the calculation results to obtain magnetic field noise of the gradiometer so as to finish the evaluation of the influence of the magnetic field on the instrument; finally, the magnetic field noise is subtracted from the instrument output.
The following are examples.
Example 1:
a magnetic field effect evaluation method of a rotary gravity gradiometer is disclosed, the rotary gravity gradiometer is shown in figure 1, and comprises a rotary table 1 and four accelerometers 2 arranged on the rotary table 1;
the magnetic field effect evaluation method of the rotary gravity gradiometer provided by the embodiment comprises the following steps:
measuring the magnetic field intensity in real time by using n pairs of magnetometers 3 arranged on the turntable 1; each magnetometer 3 and the accelerometer 2 are positioned on the same circumference and are not overlapped with each other, and the phases of the two magnetometers in each pair of magnetometers are different by 180 degrees; n is a positive integer, as shown in fig. 2, in the present embodiment, a pair of magnetometers 3 is specifically installed, that is, n is 1;
respectively evaluating corresponding magnetic field contributions according to the measurement results of each pair of magnetometers to obtain n magnetic field contributions in total, and taking the average value of the n magnetic field contributions as the magnetic field noise obtained by evaluation;
due to the volume relationship between the magnetometer and the accelerometer, the magnetic field input of the accelerometer cannot be measured at the same position in real time, so that a certain phase angle difference exists between the mounting position of the magnetometer and the mounting position of the accelerometer in the embodiment; for convenience of description, in this embodiment, the installation position of each pair of magnetometers is described by the phase angle difference between one magnetometer and the first accelerometer, and the counterclockwise direction is positive and the clockwise direction is negative; for a given rotary gradiometer, the first accelerometer is calibrated;
three input shafts of each magnetometer point to the radial direction, the tangential direction and the rotating shaft direction of the turntable respectively and correspond to the x direction, the y direction and the z direction respectively; because the two magnetometers in each pair of magnetometers are spaced by 180 degrees in phase, the two magnetometers have opposite input shaft directions along the tangential direction and the radial direction, and the elimination of a common-mode magnetic field can be realized;
taking a pair of magnetometers as an example, the evaluation of the magnetic field contribution corresponding to each pair of magnetometers includes:
(S1) calculating the magnetic gradients in the x, y and z directions according to the measurement results of the two magnetometers, and demodulating the magnetic gradients in all directions respectively by using the magnetic field demodulation signals of the sine channel and the cosine channel to obtain the magnetic gradient components in all directions and all channels;
the phase of the magnetic field demodulation signal is advanced by phi compared with the phase of the demodulation signal of the rotary gravity gradiometer, wherein phi is the phase angle difference between one magnetometer and the first accelerometer;
three of two magnetometers of a pair of magnetometersThe output in each direction is B1x，B1y，B1zAnd B2x，B2y，B2zAfter the common-mode magnetic field is eliminated in a combined mode, the magnetic gradients in the x direction, the y direction and the z direction are respectively obtained as follows:
because a phase angle difference exists between the magnetometer and the accelerometer, in order to demodulate the magnetic gradient measured by the magnetometer, the phase advance or delay is carried out on the demodulation signal of the rotary gravity gradiometer according to the phase relation between the magnetometer and the accelerometer, so as to realize the conversion of a coordinate system;
the demodulation signals of the rotary gradiometer in a sine channel and a cosine channel are sin2 theta and cos2 theta respectively; taking the first accelerometer as a reference, if the difference between the magnetometer and the phase angle of the magnetometer in the counterclockwise direction is phi, the phase of a demodulation signal of the rotary gravity gradiometer needs to be advanced by phi, and the obtained magnetic field demodulation signals of a sine channel and a cosine channel are sin2 (theta + phi) and cos2 (theta + phi) respectively;
in order to facilitate the demodulation of the magnetic gradient, as a preferred embodiment, in this embodiment, when Φ is 45 °, the magnetic field demodulation signal of the sine channel is cos2 θ, and the magnetic field demodulation signal of the cosine channel is sin2 θ;
demodulating the magnetic gradient by using a magnetic field demodulation signal obtained after phase conversion, wherein the demodulation process is shown as the following formula:
(S2) for each accelerometer, on each channel, multiplying the magnetic coefficients of the accelerometer in three directions by the magnetic gradient components of the accelerometer in three directions on the channel correspondingly, and then adding the multiplication to obtain the gradient influence of the magnetic field on the accelerometer on the sine channel and the cosine channel respectively;
with Aj(j-1, 2, 3, 4) represents fourAccelerometer, consider accelerometer AjThe three-directional responses of which are respectively K as shown in FIG. 3xj、KyjAnd KzjThe unit is g/T, the magnetic coefficient and the magnetic gradient component are substituted into the following formula, and the magnetic field on the sine channel and the cosine channel can be calculated to the accelerometer AjThe gradient influence T that resultsjsinAnd Tjcos：
(S3) adding the gradient influences corresponding to the four accelerometers on each channel to obtain components of the magnetic field contributions on a sine channel and a cosine channel;
by TsinAnd TcosRepresenting the components of the magnetic field contribution in the sine and cosine channels, respectively, the corresponding calculation is:
Tsin＝T1sin+T2sin+T3sin+T4sin
Tcos＝T2cos+T2cos+T3cos+T4cos
since only one pair of magnetometers is installed in this embodiment, the magnetic field contribution calculated based on the measurement results of the pair of magnetometers is the magnetic field noise finally evaluated.
Based on the above steps, the present embodiment achieves accurate evaluation of magnetic field noise. In order to further improve the accuracy of the gravity gradient output by the rotary gravity gradiometer, the present embodiment further comprises: deducting the estimated magnetic field noise from the gravity gradient output by the rotary gravity gradiometer; specifically, the output of the rotary gravity gradiometer is divided into two channels, namely a sine channel and a cosine channel, and the outputs of the two channels are respectively marked as UsinAnd UcosFrom the output of this channel, respectively, is subtractedRemoving magnetic field noise of corresponding channel to finally obtain instrument output U 'after magnetic field noise is subtracted'sinAnd U'cosRespectively as follows:
U'sin＝Usin-Tsin
U'cos＝Ucos-Tcos
generally speaking, the present embodiment separates the gravity gradient signal from the magnetic field noise by a method of installing the three-axis magnetometer at a specific position, so as to realize real-time magnetic field monitoring, and finally achieve the purpose of estimating and deducting the influence of the magnetic field on the gradiometer through simple calculation and coordinate conversion according to the specific position relationship between the three-axis magnetometer and the accelerometer.
Example 2:
a magnetic field effect evaluation method for a rotary gravity gradiometer, which is similar to that in embodiment 1, but is different in that, in order to further improve the evaluation accuracy of magnetic field noise, in this embodiment, 2 pairs of magnetometers are mounted on a turntable of the rotary gravity gradiometer, corresponding magnetic field contributions are evaluated for each pair of magnetometers, and an average value is taken to serve as the finally evaluated magnetic field noise; the evaluation of the magnetic field contribution of each pair of magnetometers can be performed as described in example 1 above, and will not be repeated here.
The magnetic field contributions are respectively evaluated by utilizing a plurality of pairs of magnetometers, and the average value is obtained, so that the evaluation error of the magnetic field contributions can be effectively reduced, and the evaluation accuracy of the magnetic field noise is further improved; as a preferred implementation manner, in this embodiment, the phase angle differences between the two pairs of magnetometers and the first accelerometer in the counterclockwise direction are 45 ° and 135 °, respectively, and the installation positions of the two pairs of magnetometers are set in this way, on one hand, after the phase conversion is performed on the demodulated signals, the obtained magnetic field demodulated signals are relatively simple, and on the other hand, the installation positions of the two pairs of magnetometers are centrosymmetric, and the symmetric center is the center of the turntable, so that the stability of the turntable can be ensured.
It is understood that the number of installed magnetometers can be determined according to actual evaluation requirements, and in other embodiments of the present invention, 3 or more pairs of magnetometers can be installed, and the installation positions of each pair of magnetometers can be determined according to actual evaluation requirements, and the specific evaluation manner can be referred to the description of embodiment 2, and more similar embodiments will not be listed here.
Example 3:
a magnetic field effect evaluation apparatus for a rotary gravity gradiometer comprising: the system comprises n pairs of magnetometers arranged on a turntable, n evaluation modules connected with the n pairs of magnetometers respectively, and an output module; in the present embodiment, n is 1;
in the n pairs of magnetometers, each magnetometer and the accelerometer are positioned on the same circumference and are not overlapped with each other, and the phases of the two magnetometers in each pair of magnetometers are different by 180 degrees; n is a positive integer;
the n evaluation modules are respectively used for evaluating corresponding magnetic field contributions according to the measurement results of each pair of magnetometers to obtain n magnetic field contributions;
an output module for taking the average of the n magnetic field contributions as the magnetic field noise obtained by the evaluation;
the evaluation module comprises: a first combination unit, a phase conversion unit, a demodulation unit, a second combination unit and a third combination unit;
the first combination unit is used for calculating the average value of the magnetic field intensity measured by the two magnetometers in the x direction, the y direction and the z direction to obtain the magnetic gradient in the x direction, the y direction and the z direction;
the phase conversion unit is used for advancing the phase of the demodulation signal of the rotary gravity gradiometer by phi to obtain a magnetic field demodulation signal; phi is the phase angle difference between one magnetometer and the first accelerometer when the anticlockwise direction is taken as positive;
the demodulation unit is used for demodulating the magnetic gradients in all directions respectively by using the magnetic field demodulation signals of the sine channel and the cosine channel to obtain the magnetic gradient components in all directions and all channels;
the second combination unit is used for multiplying the magnetic coefficients of the accelerometer in the three directions on each channel by the magnetic gradient components of the accelerometer in the three directions on the channel, and adding the multiplied magnetic coefficients to obtain the gradient influence of a magnetic field on the accelerometer on a sine channel and a cosine channel respectively;
the third combination unit is used for adding the gradient influences corresponding to the four accelerometers on each channel to obtain components of the magnetic field contribution on a sine channel and a cosine channel;
in this embodiment, the specific implementation of each module can refer to the description in embodiment 1, and will not be repeated here.
Example 4:
a magnetic field effect evaluation device for a rotary gravity gradiometer, which is similar to embodiment 3, except that in this embodiment, n is 2;
in this embodiment, the specific implementation of each module can refer to the description in embodiment 2, and will not be repeated here.
Example 5:
a gravity gradient measurement system comprising: a rotary gravity gradiometer, a magnetic field effect evaluation device of the rotary gravity gradiometer provided in embodiment 3 or 4 above, and a magnetic field noise subtraction device;
a rotary gravity gradiometer for measuring magnetic field gradients;
the magnetic field effect evaluation device is used for evaluating magnetic field noise in the rotary gravity gradiometer;
and the magnetic field noise deduction device is used for deducting the components of the magnetic field noise in the sine channel and the cosine channel from the sine channel output result and the cosine channel output result of the rotary gravity gradiometer respectively so as to deduct the magnetic field noise.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A method of assessing a magnetic field effect of a rotary gravity gradiometer comprising a turntable and four accelerometers mounted on the turntable, the method comprising:
measuring the magnetic field intensity in real time by using n pairs of magnetometers arranged on the rotary table; each magnetometer and the accelerometer are positioned on the same circumference and are not overlapped with each other, and the phase difference between the two magnetometers in each pair of magnetometers is 180 degrees; n is a positive integer;
respectively evaluating corresponding magnetic field contributions according to the measurement results of each pair of magnetometers to obtain n magnetic field contributions in total, and taking the average value of the n magnetic field contributions as the magnetic field noise obtained by evaluation;
the evaluation of the magnetic field contribution corresponding to each pair of magnetometers includes:
(S1) calculating the magnetic gradients in the x, y and z directions according to the measurement results of the two magnetometers, and demodulating the magnetic gradients in all directions respectively by using the magnetic field demodulation signals of the sine channel and the cosine channel to obtain the magnetic gradient components in all directions and all channels; the phase of the magnetic field demodulation signal is advanced by phi compared with the phase of the demodulation signal of the rotary gravity gradiometer, wherein phi is the phase angle difference between one magnetometer and the first accelerometer when the anticlockwise direction is taken as positive time;
(S2) for each accelerometer, on each channel, multiplying the magnetic coefficients of the accelerometer in three directions by the magnetic gradient components of the accelerometer in three directions on the channel correspondingly, and then adding the multiplication to obtain the gradient influence of the magnetic field on the accelerometer on the sine channel and the cosine channel respectively;
(S3) the gradient contributions of the four accelerometers on each channel are summed to obtain the components of the magnetic field contribution on the sine and cosine channels.
2. The method of claim 1, wherein n is 1.
3. The method of claim 2, wherein φ is 45 degrees.
4. The method of claim 1, wherein n is 2.
5. The method of claim 4, wherein the phase angle difference φ between the two pairs of magnetometers is 45 ° and 135 °, respectively.
6. The method of any of claims 1 to 5, further comprising: and respectively subtracting the components of the magnetic field noise in the sine channel and the cosine channel from the sine channel output result and the cosine channel output result of the rotary gravity gradiometer so as to subtract the magnetic field noise.
7. A magnetic field effect evaluation device for a rotary gradiometer comprising a turntable and four accelerometers mounted on the turntable, the device comprising: the system comprises n pairs of magnetometers arranged on the rotary table, n evaluation modules connected with the n pairs of magnetometers respectively, and an output module;
in the n pairs of magnetometers, each magnetometer and the accelerometer are positioned on the same circumference and are not overlapped with each other, and the phases of the two magnetometers in each pair of magnetometers are different by 180 degrees; n is a positive integer;
the n evaluation modules are respectively used for evaluating corresponding magnetic field contributions according to the measurement results of each pair of magnetometers to obtain n magnetic field contributions;
the output module is used for taking the average value of the n magnetic field contributions as the magnetic field noise obtained by evaluation;
the evaluation module comprises: a first combination unit, a phase conversion unit, a demodulation unit, a second combination unit and a third combination unit;
the first combination unit is used for calculating the average value of the magnetic field intensity measured by the two magnetometers in the x direction, the y direction and the z direction to obtain the magnetic gradient in the x direction, the y direction and the z direction;
the phase conversion unit is used for advancing the phase of the demodulation signal of the rotary gravity gradiometer by phi to obtain a magnetic field demodulation signal; phi is the phase angle difference between one magnetometer and the first accelerometer when the anticlockwise direction is taken as positive;
the demodulation unit is used for demodulating the magnetic gradients in all directions respectively by using the magnetic field demodulation signals of the sine channel and the cosine channel to obtain the magnetic gradient components in all directions and all channels;
the second combination unit is used for multiplying the magnetic coefficients of the accelerometer in the three directions on each channel by the magnetic gradient components of the accelerometer in the three directions on the channel correspondingly and then adding the multiplied magnetic coefficients to obtain the gradient influence of the magnetic field on the accelerometer on the sine channel and the cosine channel respectively;
and the third combination unit is used for adding the gradient influences of the four accelerometers on each channel to obtain the components of the magnetic field contributions on the sine channel and the cosine channel.
8. A gravity gradient measurement system, comprising: a rotary gravity gradiometer, a magnetic field effect assessment device for a rotary gravity gradiometer as claimed in claim 7, and a magnetic field noise subtraction device;
the rotary gravity gradiometer is used for measuring the magnetic field gradient;
the magnetic field effect evaluation device is used for evaluating magnetic field noise in the rotary gravity gradiometer;
and the magnetic field noise deduction device is used for respectively subtracting the components of the magnetic field noise in the sine channel and the cosine channel from the sine channel output result and the cosine channel output result of the rotary gravity gradiometer so as to deduct the magnetic field noise.
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| A High-sensitivity Optical MEMS Accelerometer based on SOI Double-side Micromachining;Ziqiang Qu etc;《 IEEE Xplore》;20201231;全文 * |
| 面向地球物理应用的高精度ＭＥＭＳ惯性传感器;王秋，刘骅锋，涂良成;《导航与控制》;20181231;第17卷(第6期);全文 * |
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