CN111679335A - Method and equipment for determining absolute gravity acceleration - Google Patents
Method and equipment for determining absolute gravity acceleration Download PDFInfo
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Abstract
The invention discloses a method and equipment for determining absolute gravitational acceleration, wherein the method comprises the steps of recording an interference fringe sampling sequence generated in the free falling process of a falling body in a laser interference absolute gravimeter, sequentially intercepting the interference fringe sampling sequence based on preset window duration and preset translation duration so as to determine a plurality of window sampling sequences, determining an analytic signal of the window sampling sequences according to the window sampling sequences and Hilbert transform results of the window sampling sequences, then determining window gravitational acceleration according to the analytic signal and falling parameters of the window sampling sequences, and determining the absolute gravitational acceleration of the falling body according to the gravitational acceleration sequence corresponding to the window gravitational acceleration, so that the measurement accuracy of the gravitational acceleration value can be further improved under the condition of vibration interference.
Description
Technical Field
The present application relates to the field of gravity measurement technologies, and more particularly, to a method and apparatus for determining an absolute gravitational acceleration.
Background
The main tool used for measuring the g value of the gravitational acceleration at present is a laser interference absolute gravimeter, and the gravitational acceleration is obtained by accurately measuring the free falling displacement and time of a falling body in a gravitational field. The existing method for measuring the gravitational acceleration is to monitor the trajectory of a free-falling object by means of laser interference. After a laser beam emitted from a laser enters a spectroscope, the laser beam is divided into two beams by the spectroscope: a measuring beam and a reference beam; wherein, the measuring beam irradiates the measured falling body (pyramid prism) to be reflected; and the measuring beam reflected by the measured falling body irradiates the reference prism for reflection. When the measured falling body falls, the measuring beam reflected by the reference prism interferes with the reference beam to generate interference fringes. The number of the interference fringes corresponds to the falling displacement of the measured falling body, and the falling time of the measured falling body is recorded. The gravity acceleration g value is usually obtained by multipoint measurement and least square fitting.
In the prior art, two common methods are used for acquiring and processing interference fringe data of a laser interference absolute gravimeter: the method comprises the steps of performing function fitting on a data segment containing a zero crossing point of interference fringe acquired data to accurately obtain the zero crossing point time of the interference fringe, and then calculating a gravity acceleration value of a sequence according to a falling body position and time data; and the second method fully utilizes interference fringe data acquired in the whole falling process, and carries out full waveform data calculation in a segmented manner, thereby obtaining a gravity acceleration value.
In the method, only zero phase data is concerned, the requirement on the computing power of a computer is not high, nonlinear least square fitting is avoided, and the method is based on uniform distribution of falling distances and non-uniform distribution of time, so that the vibration interference signal processing in a time neighborhood is quite difficult, and in addition, because only zero phase data is concerned and most other data is ignored, the problem of double triggering exists under the influence of interference.
The second method carries out full-waveform processing on the laser interference fringe signal, avoids the defect that a zero crossing point algorithm discards other data except the zero crossing point, and obtains the gravity acceleration value by fitting the falling body track by using a least square method. During the regression process, the regression correlation may not pass through all of each regression data point, reducing the accuracy of the measurement of the gravitational acceleration values.
Therefore, how to further improve the measurement accuracy of the gravitational acceleration value in the presence of vibration interference is a technical problem to be solved at present.
Disclosure of Invention
The invention provides a method and equipment for determining absolute gravitational acceleration, which are used for solving the technical problem that the measurement accuracy of a gravitational acceleration value is not high under the condition of vibration interference in the prior art, and the method comprises the following steps:
recording interference fringe sampling sequences generated in the free falling process of a falling body in a laser interference absolute gravimeter, and sequentially intercepting the interference fringe sampling sequences to determine a plurality of window sampling sequences based on preset window duration and preset translation duration;
determining an analytic signal of the window sampling sequence according to the window sampling sequence and a Hilbert transform result of the window sampling sequence;
determining the window gravity acceleration according to the analytic signal and the falling parameter of the window sampling sequence;
and determining the absolute gravity acceleration of the falling body according to the gravity acceleration sequence corresponding to the gravity acceleration of each window.
Preferably, before determining the analytic signal of the window sample sequence according to the window sample sequence and the hilbert transform result of the window sample sequence, the method further includes:
determining a first Hilbert transform result based on Hilbert transforming the window sample sequence;
determining a spectral signal based on a fast Fourier transform of the first Hilbert transform result;
determining a second Hilbert transform result based on inverse fast Fourier transforming the spectrum signal, and taking the second Hilbert transform result as the Hilbert transform result.
Preferably, the falling parameters include a preliminary phase, a falling displacement of the falling body, a falling time of the falling body, a laser wavelength, a starting position of the falling body, an initial velocity of the falling body and a gravitational acceleration of the falling body at the starting position, and the window gravitational acceleration is determined according to the analytic signal and the falling parameters of the window sampling sequence, specifically:
determining an instantaneous phase of the window sample sequence from a real part and an imaginary part of the analytic signal, the real part being determined from the window sample sequence and the imaginary part being determined from the Hilbert transform result;
determining a free falling body motion trail equation according to the falling parameters;
and determining the window gravity acceleration according to the instantaneous phase and the free-fall motion trajectory equation.
Preferably, before determining the absolute gravitational acceleration of the falling body according to the gravitational acceleration sequence corresponding to each of the window gravitational accelerations, the method further includes:
correcting the window gravity acceleration according to a preset gravity gradient constant and the effective measurement height, and determining a corrected window gravity acceleration according to the corrected result;
and determining the gravity acceleration sequence according to the gravity acceleration of each correction window.
Preferably, the window gravitational acceleration is corrected according to a preset gravitational gradient constant and an effective measurement height, and the corrected window gravitational acceleration is determined according to the corrected result, specifically:
according to the formula g ═ g0+γhefDetermining the corrected window gravitational acceleration;
wherein g is the gravity acceleration of the correction window, g0Is the window gravitational acceleration, gamma is the preset gravitational gradient constant, hefThe height is measured for the effective measurement.
Correspondingly, the invention also proposes a device for determining absolute gravitational acceleration, said device comprising:
the system comprises a first determining module, a second determining module and a control module, wherein the first determining module is used for recording interference fringe sampling sequences generated in the free falling process of a falling body in the laser interference absolute gravimeter, and sequentially intercepting the interference fringe sampling sequences to determine analytic signals of a plurality of window sampling sequences based on preset window duration and preset translation duration;
a second determining module, configured to determine an analytic signal of the window sampling sequence according to the window sampling sequence and a hilbert transform result of the window sampling sequence;
the third determining module is used for determining the window gravity acceleration according to the analytic signal and the falling parameter of the window sampling sequence;
and the fourth determining module is used for determining the absolute gravity acceleration of the falling body according to the gravity acceleration sequence corresponding to the gravity acceleration of each window.
Preferably, the apparatus further comprises a transformation module for:
determining a first Hilbert transform result based on Hilbert transforming the window sample sequence;
determining a spectral signal based on a fast Fourier transform of the first Hilbert transform result;
determining a second Hilbert transform result based on performing an inverse fast Fourier transform on the spectral signal, and taking the second Hilbert transform result as the Hilbert transform result.
Preferably, the falling parameters include a preliminary phase, a falling displacement of the falling body, a falling time of the falling body, a laser wavelength, a starting position of the falling body, an initial velocity of the falling body, and a gravitational acceleration of the falling body at the starting position, and the third determining module is specifically configured to:
determining an instantaneous phase of the window sample sequence from a real part and an imaginary part of the analytic signal, the real part being determined from the window sample sequence and the imaginary part being determined from the Hilbert transform result;
determining a free falling body motion trail equation according to the falling parameters;
and determining the window gravity acceleration according to the instantaneous phase and the free-fall motion trajectory equation.
Preferably, the device further comprises a correction module for:
correcting the window gravity acceleration according to a preset gravity gradient constant and the effective measurement height, and determining a corrected window gravity acceleration according to the corrected result;
and determining the gravity acceleration sequence according to the gravity acceleration of each correction window.
Preferably, the modification module is specifically configured to:
according to the formula g ═ g0+γhefDetermining the corrected window gravitational acceleration;
wherein g is the gravity acceleration of the correction window, g0Is the window gravitational acceleration, gamma is the preset gravitational gradient constant, hefThe height is measured for the effective measurement.
The invention discloses a method and equipment for determining absolute gravitational acceleration, the method comprises recording interference fringe sampling sequence generated in free falling process of falling body in laser interference absolute gravimeter, sequentially intercepting the interference fringe sampling sequence based on preset window duration and preset translation duration to determine multiple window sampling sequences, determining analytic signal of the window sampling sequences according to Hilbert transform result of the window sampling sequences and the window sampling sequences, then determining window gravitational acceleration according to the analytic signal and falling parameter of the window sampling sequences, determining absolute gravitational acceleration of the falling body according to gravitational acceleration sequence corresponding to each window gravitational acceleration, and avoiding defect that zero-crossing point algorithm discards other data except zero-crossing point by fully utilizing all interference fringe data collected in falling process of the falling body, and directly determining the window gravity acceleration based on the instantaneous phase and the free-fall motion trajectory equation, thereby further improving the measurement accuracy of the gravity acceleration value under the condition of vibration interference.
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In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart illustrating a method for determining absolute gravitational acceleration in accordance with a preferred embodiment of the present invention;
FIG. 2 is a flow chart illustrating a method for determining absolute gravitational acceleration according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an apparatus for determining absolute gravitational acceleration according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The absolute gravimeter is a main precise instrument which is developed internationally and used for directly measuring the gravity acceleration, is also an important technical means for detecting the information of the earth gravitational field, and plays more and more roles in the aspects of national gravity datum point establishment, earthquake and sea level monitoring, precise measurement of the ground level, vertical deformation of the earth crust, national defense construction and the like.
As described in the background art, there are two common methods in the prior art for acquiring and processing data of interference fringes of a laser interference absolute gravimeter, one method is to perform function fitting on a data segment of the interference fringe acquired data including a zero crossing point to accurately obtain the time of the zero crossing point of the interference fringe, and then calculate a gravity acceleration value for a sequence according to a falling body position and time data.
The other method is to perform full waveform processing on the laser interference fringe signals, and fit the falling body track by using a least square method to obtain the gravity acceleration value, but in the regression process of the method, the regression correlation can not completely pass through each regression data point, so that the measurement accuracy of the gravity acceleration value is reduced.
Therefore, the present application proposes a method for determining an absolute gravitational acceleration, so as to further improve the measurement accuracy of the gravitational acceleration value in the presence of vibration interference.
Fig. 1 is a schematic flow chart of a method for determining absolute gravitational acceleration according to a preferred embodiment of the present invention, which includes the following steps:
step S101, recording interference fringe sampling sequences generated in the free falling process of a falling body in a laser interference absolute gravimeter, and sequentially intercepting the interference fringe sampling sequences to determine a plurality of window sampling sequences based on preset window duration and preset translation duration.
In the step, the falling body in the laser interference absolute gravimeter can generate interference fringes containing falling body movement information in the free falling process, and the generated interference fringes are sampled to obtain an interference fringe sampling sequence.
The window duration and the translation duration can be preset, a plurality of windows are obtained according to the preset window duration and the preset translation duration, and each window is used for sampling the interference fringes to obtain a plurality of window sampling sequences.
The window duration and the translation duration can be flexibly set by those skilled in the art according to actual needs, which does not affect the scope of the present application.
Step S102, determining an analytic signal of the window sampling sequence according to the window sampling sequence and a Hilbert transform result of the window sampling sequence.
It should be noted that the hilbert transform is to convolve the signal s (t) with 1/(tt) to obtain s' (t). Thus, the result of the hilbert transform s' (t) can be interpreted as the output of a linear time-invariant system whose input is s (t), and whose impulse response is 1/(π t), so that the amplitude of each frequency component in the frequency domain remains unchanged after the hilbert transform of the signal, but the phase will appear 90 ° phase shift. I.e. lags pi/2 for positive frequencies and leads pi/2 for negative frequencies, the hilbert transformer is also called a 90 deg. phase shifter.
Specifically, the collected window sampling sequence needs to be further analyzed to obtain an analysis signal, and in order to obtain the analysis signal, the collected window sampling sequence needs to be subjected to hilbert transform first, and a transformed result is combined with an original window sampling sequence signal to obtain the analysis signal.
In order to accurately determine the analytic signal, in a preferred embodiment of the present application, before determining the analytic signal of the window sample sequence according to the window sample sequence and the hilbert transform result of the window sample sequence, the method further includes:
determining a first Hilbert transform result based on Hilbert transforming the window sample sequence;
determining a spectral signal based on a fast Fourier transform of the first Hilbert transform result;
determining a second Hilbert transform result based on inverse fast Fourier transforming the spectrum signal, and taking the second Hilbert transform result as the Hilbert transform result.
It should be noted that Fast Fourier Transform (FFT), which is a general name of an efficient and fast calculation method for calculating discrete Fourier transform by using a computer, is abbreviated as FFT, the more the number N of transformed sampling points, the more significant the saving of the calculation amount of the FFT algorithm, and the inverse fast Fourier transform can convert the frequency domain expression of a signal into the time domain expression.
Specifically, the window sampling sequence is first subjected to hilbert transform to determine a first hilbert transform result, then the first hilbert transform result is subjected to fast fourier transform once to determine a frequency spectrum signal of the first hilbert transform result, and then the frequency spectrum signal is subjected to inverse fast fourier transform to determine a second hilbert transform result, that is, the hilbert transform result of the analytic signal is determined finally.
And S103, determining the window gravity acceleration according to the analysis signal and the falling parameters of the window sampling sequence.
Specifically, by determining a plurality of window sampling sequences, each window sampling sequence corresponds to a gravity acceleration value, and the gravity acceleration corresponding to each window sampling sequence can be determined according to the falling parameters and the analytic signals of the window sampling sequences.
In order to accurately determine each window gravitational acceleration, in a preferred embodiment of the present application, the falling parameters include a preliminary phase, a falling displacement of the falling body, a falling time of the falling body, a laser wavelength, a starting position of the falling body, an initial velocity of the falling body, and a gravitational acceleration of the falling body at the starting position, and the window gravitational acceleration is determined according to the analytic signal and the falling parameters of the window sampling sequence, specifically:
determining an instantaneous phase of the window sample sequence from a real part and an imaginary part of the analytic signal, the real part being determined from the window sample sequence and the imaginary part being determined from the Hilbert transform result;
determining a free falling body motion trail equation according to the falling parameters;
and determining the window gravity acceleration according to the instantaneous phase and the free-fall motion trajectory equation.
It should be noted that the analytic signal (analytic signal) is a complex function without negative frequency components. The real and imaginary parts of the analytic signal are real-valued functions associated by the hilbert transform, and the phase is the position in its cycle for a wave at a particular instant: a scale of whether it is at a peak, trough or some point in between, the phase describes a measure of the change in the waveform of the signal, usually in degrees (angle) also known as the phase angle, when the signal waveform changes in a periodic manner, the waveform cycles through 360 °.
In the step, the instantaneous phase of a window sampling sequence is determined according to the real part and the imaginary part in the obtained analytic signal, the free fall running track equation of the measured fall is determined according to the fall parameters, and the gravity acceleration of each window is determined according to the obtained instantaneous phase and the free fall motion track equation.
And step S104, determining the absolute gravity acceleration of the falling body according to the gravity acceleration sequence corresponding to the gravity acceleration of each window.
In this step, after determining the gravity acceleration sequence corresponding to each of the window gravity accelerations, the average value of the gravity acceleration sequence may be used as the absolute gravity acceleration of the falling body, and in order to further improve the accuracy of the measurement, multiple measurements may be performed based on steps S101 to S104, and the final absolute gravity acceleration may be determined according to multiple measurement results.
In order to improve the accuracy of measuring the absolute gravitational acceleration in consideration of the gravitational gradient influence, in a preferred embodiment of the present application, before determining the absolute gravitational acceleration of the falling body according to the gravitational acceleration sequence corresponding to each of the window gravitational accelerations, the method further includes:
correcting the window gravity acceleration according to a preset gravity gradient constant and the effective measurement height, and determining a corrected window gravity acceleration according to the corrected result;
and determining the gravity acceleration sequence according to the gravity acceleration of each correction window.
Specifically, after the window gravitational acceleration is obtained, the corrected window gravitational acceleration needs to be obtained according to the gravity gradient constant and the effective measurement height, and then the gravitational acceleration sequence is determined according to the corrected window gravitational acceleration.
In order to determine an accurate corrected window acceleration, in a preferred embodiment of the present application, the window gravitational acceleration is corrected according to a preset gravitational gradient constant and an effective measurement height, and the corrected window gravitational acceleration is determined according to a correction result, specifically:
according to the formula g ═ g0+γhefDetermining the corrected window gravitational acceleration;
wherein g is the gravity acceleration of the correction window, g0Is the window gravitational acceleration, gamma is the preset gravitational gradient constant, hefThe height is measured for the effective measurement.
By applying the technical scheme, an interference fringe sampling sequence generated in the free falling process of a falling body in a laser interference absolute gravimeter is recorded, the interference fringe sampling sequence is sequentially intercepted based on preset window duration and preset translation duration so as to determine a plurality of window sampling sequences, an analytic signal of the window sampling sequence is determined according to the window sampling sequence and a Hilbert transform result of the window sampling sequence, then window gravitational acceleration is determined according to the analytic signal and falling parameters of the window sampling sequence, absolute gravitational acceleration of the falling body is determined according to a gravitational acceleration sequence corresponding to each window gravitational acceleration, the defect that a zero-crossing point algorithm discards other data except for a zero-crossing point is avoided by fully utilizing all interference fringe data acquired in the falling process of the falling body, and the window gravitational acceleration is directly determined based on an instant phase and a free falling body motion trajectory equation, therefore, the measurement accuracy of the gravity acceleration value can be further improved under the condition of vibration interference.
In order to further explain the technical idea of the present invention, the technical solution of the present invention is now described with reference to a specific application scenario of gravitational acceleration measurement.
The specific embodiment of the invention provides a method for determining absolute gravitational acceleration, which comprises the steps of obtaining a multi-window interference fringe sampling sequence, conducting Hilbert transform on each window sampling sequence, obtaining a frequency spectrum signal of a transform result, namely conducting fast Fourier transform on the transform result, conducting inverse fast Fourier transform on the frequency spectrum signal to obtain a final transform result, constructing an analysis signal according to the final transform result, calculating the instantaneous phase of the analysis signal, determining the gravitational acceleration of each window, and finally determining the absolute gravitational acceleration according to each window gravitational acceleration sequence.
As shown in fig. 2, the method comprises the following specific steps:
step S201, obtaining an interference fringe sampling sequence ui。
Specifically, in the free fall process of the measured falling body, the measuring beam reflected by the reference prism interferes with the reference beam to generate interference fringes, the interference fringes contain the movement information of the falling body, and the interference fringe signal can be represented by the following formula:
U(θ)＝Acosθ+Bsinθ
wherein A and B are amplitudes, f0For the fundamental frequency, k is the frequency modulation rate and θ is the instantaneous phase.
Step S202, intercepting a sampling sequence u in a 0.1ms windowk。
Specifically, in the measurement process of the absolute gravimeter, the running time of the free falling body is about 0.2s, which can be regarded as the maximum period, the corresponding frequency lower limit is 5Hz, the window size is set to be 0.1ms, each time of translation is 0.05ms, each window calculates an absolute gravity value, the sampling rate is 20KHz, the frequency upper limit is 10KHz, and the interference fringe signal of the measured falling body falling once is subjected to segmented sampling on the interference fringe waveform by adopting a multi-period window sliding method.
Step S203, determining whether the current window serial number is smaller than the preset window serial number.
Specifically, the number k of windows may be calculated according to the falling time of the detected falling body and the preset window size, the preset window number is the last window j, and when the current window number is not less than the preset number, the sampling is finished after the last window is executed, that is, step S211 is finished.
Step S204, calculating ukBy Hilbert transform vk。
Specifically, the real signal can be obtained by performing hilbert transform on the sampling sequence
And an imaginary signal.
Step S205, obtaining FFT spectrum V of vkk。
FFT (fast Fourier transform), namely, fast Fourier transform, and the obtained Hilbert transform result is subjected to fast Fourier transform to obtain a frequency spectrum signal Vk。
Step S206, obtaining VkInverse FFT of (a) to obtain vk。
Specifically, the spectrum signal Vk obtained in step S205 is subjected to inverse fast fourier transform, that is, inverse FFT, to obtain vk。
Step S207, exercise ukAnd vkConstruction of ukAnalytic signal z ofk。
Specifically, the above obtained result can be calculated according to the following formula to obtain an analytic signal:
step S208, calculating analysis signal ZkThe instantaneous phase of (c).
Specifically, Z can be calculated by the following formulakInstantaneous phase of (d):
and step S209, resolving and correcting the gravity acceleration value.
Specifically, each half laser wavelength of the free fall corresponds to one period of the interference fringe waveform, and the free fall can be represented by the following formula under the condition of ignoring gravity gradient:
in the formula [ theta ]0For preliminary phase, x is the falling displacement of the free-fall, t is the falling time of the free-fall, λ is the laser wavelength, x0Is a starting position, v0As initial velocity, g0For the gravity acceleration of the start position, the absolute gravity value can be calculated by combining the two formulas in step S208 and step S209, but considering the gravity gradient influence, the following formula is also used for calculating the absolute gravity value g0And (5) correcting:
g＝g0+γhef
wherein g is the absolute gravity value after correction, gamma is the gravity gradient constant, hefTo effectively measure the height.
And step S210, adding 0.05ms to the current window sequence number.
Specifically, adding 0.05ms to the current window serial number actually serves as a next window, and after the calculation of the gravitational acceleration value of the current window is completed, calculation of the gravitational acceleration value of the next window is started, and until the calculation of the gravitational acceleration values of all windows is completed, the gravitational acceleration value sequence calculated by all windows can be obtained.
And step S211, ending.
By applying the technical scheme, a plurality of window interference fringe sampling sequences are obtained, Hilbert transform is carried out on each window sampling sequence, and obtaining the frequency spectrum signal of the transformation result, namely, performing fast Fourier transformation on the transformation result, performing inverse fast Fourier transformation on the frequency spectrum signal to obtain the final transformation result, constructing an analytic signal through the final transformation result, calculating the instantaneous phase of the analytic signal, determining the window gravity acceleration of each window, determining the absolute gravity acceleration according to the gravity acceleration sequence of the window gravity acceleration, by fully utilizing all interference fringe data acquired in the falling process of the falling body, the defect that other data except the zero crossing point are discarded by a zero crossing point algorithm is avoided, directly determining the window gravity acceleration based on the instantaneous phase and the free-fall motion trajectory equation, therefore, the measurement accuracy of the gravity acceleration value can be further improved under the condition of vibration interference.
Corresponding to the method for determining the absolute gravitational acceleration in the preferred embodiment of the present application, the present application further provides an apparatus for determining the absolute gravitational acceleration, as shown in fig. 3, where the apparatus includes:
the system comprises a first determining module, a second determining module and a control module, wherein the first determining module is used for recording interference fringe sampling sequences generated in the free falling process of a falling body in the laser interference absolute gravimeter, and sequentially intercepting the interference fringe sampling sequences to determine analytic signals of a plurality of window sampling sequences based on preset window duration and preset translation duration;
a second determining module, configured to determine an analytic signal of the window sampling sequence according to the window sampling sequence and a hilbert transform result of the window sampling sequence;
the third determining module is used for determining the window gravity acceleration according to the analytic signal and the falling parameter of the window sampling sequence;
and the fourth determining module is used for determining the absolute gravity acceleration of the falling body according to the gravity acceleration sequence corresponding to the gravity acceleration of each window.
In a specific application scenario, the system further includes a transformation module, configured to:
determining a first Hilbert transform result based on Hilbert transforming the window sample sequence;
determining a spectral signal based on a fast Fourier transform of the first Hilbert transform result;
determining a second Hilbert transform result based on performing an inverse fast Fourier transform on the spectral signal, and taking the second Hilbert transform result as the Hilbert transform result.
In a specific application scenario, the falling parameters include a preliminary phase, a falling displacement of the falling body, a falling time of the falling body, a laser wavelength, a starting position of the falling body, an initial velocity of the falling body, and a gravitational acceleration of the falling body at the starting position, and the third determining module is specifically configured to:
determining an instantaneous phase of the window sample sequence from a real part and an imaginary part of the analytic signal, the real part being determined from the window sample sequence and the imaginary part being determined from the Hilbert transform result;
determining a free falling body motion trail equation according to the falling parameters;
and determining the window gravity acceleration according to the instantaneous phase and the free-fall motion trajectory equation.
In a specific application scenario, the system further comprises a modification module, configured to:
correcting the window gravity acceleration according to a preset gravity gradient constant and the effective measurement height, and determining a corrected window gravity acceleration according to the corrected result;
and determining the gravity acceleration sequence according to the gravity acceleration of each correction window.
In a specific application scenario, the modification module is specifically configured to:
according to the formula g ═ g0+γhefDetermining the corrected window gravitational acceleration;
wherein g is the correction windowAcceleration of mouth gravity, g0Is the window gravitational acceleration, gamma is the preset gravitational gradient constant, hefThe height is measured for the effective measurement.
Through the above description of the embodiments, those skilled in the art will clearly understand that the present invention may be implemented by hardware, or by software plus a necessary general hardware platform. Based on such understanding, the technical solution of the present invention can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a usb disk, a removable hard disk, etc.), and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the method according to the implementation scenarios of the present invention.
Those skilled in the art will appreciate that the figures are merely schematic representations of one preferred implementation scenario and that the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
Those skilled in the art will appreciate that the modules in the devices in the implementation scenario may be distributed in the devices in the implementation scenario according to the description of the implementation scenario, or may be located in one or more devices different from the present implementation scenario with corresponding changes. The modules of the implementation scenario may be combined into one module, or may be further split into a plurality of sub-modules.
The above-mentioned invention numbers are merely for description and do not represent the merits of the implementation scenarios.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not necessarily depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A method of determining absolute gravitational acceleration, the method comprising:
recording interference fringe sampling sequences generated in the free falling process of a falling body in a laser interference absolute gravimeter, and sequentially intercepting the interference fringe sampling sequences to determine a plurality of window sampling sequences based on preset window duration and preset translation duration;
determining an analytic signal of the window sampling sequence according to the window sampling sequence and a Hilbert transform result of the window sampling sequence;
determining the window gravity acceleration according to the analytic signal and the falling parameter of the window sampling sequence;
and determining the absolute gravity acceleration of the falling body according to the gravity acceleration sequence corresponding to the gravity acceleration of each window.
2. The method of claim 1, further comprising, prior to determining the analytic signal of the window sample sequence from the window sample sequence and the result of the hilbert transform of the window sample sequence:
determining a first Hilbert transform result based on Hilbert transforming the window sample sequence;
determining a spectral signal based on a fast Fourier transform of the first Hilbert transform result;
determining a second Hilbert transform result based on inverse fast Fourier transforming the spectrum signal, and taking the second Hilbert transform result as the Hilbert transform result.
3. The method of claim 1, wherein the fall parameters include a preliminary phase, a fall displacement of the fall, a fall time of the fall, a laser wavelength, a starting position of the fall, an initial velocity of the fall, and a gravitational acceleration of the fall at the starting position, and wherein the window gravitational acceleration is determined from the resolved signal and the fall parameters of the window sampling sequence by:
determining an instantaneous phase of the window sample sequence from a real part and an imaginary part of the analytic signal, the real part being determined from the window sample sequence and the imaginary part being determined from the Hilbert transform result;
determining a free falling body motion trail equation according to the falling parameters;
and determining the window gravity acceleration according to the instantaneous phase and the free-fall motion trajectory equation.
4. The method of claim 1, further comprising, prior to determining the absolute gravitational acceleration of the fall from the sequence of gravitational accelerations corresponding to each of the window gravitational accelerations:
correcting the window gravity acceleration according to a preset gravity gradient constant and the effective measurement height, and determining a corrected window gravity acceleration according to the corrected result;
and determining the gravity acceleration sequence according to the gravity acceleration of each correction window.
5. The method according to claim 4, wherein the window gravitational acceleration is corrected based on a preset gravitational gradient constant and an effective measurement height, and a corrected window gravitational acceleration is determined based on the result of the correction, in particular:
according to the formula g ═ g0+γhefDetermining the corrected window gravitational acceleration;
wherein g is the gravity acceleration of the correction window, g0Is the window gravitational acceleration, gamma is the preset gravitational gradient constant, hefThe height is measured for the effective measurement.
6. An apparatus for determining absolute gravitational acceleration, the apparatus comprising:
the system comprises a first determining module, a second determining module and a control module, wherein the first determining module is used for recording interference fringe sampling sequences generated in the free falling process of a falling body in the laser interference absolute gravimeter, and sequentially intercepting the interference fringe sampling sequences to determine analytic signals of a plurality of window sampling sequences based on preset window duration and preset translation duration;
a second determining module, configured to determine an analytic signal of the window sampling sequence according to the window sampling sequence and a hilbert transform result of the window sampling sequence;
the third determining module is used for determining the window gravity acceleration according to the analytic signal and the falling parameter of the window sampling sequence;
and the fourth determining module is used for determining the absolute gravity acceleration of the falling body according to the gravity acceleration sequence corresponding to the gravity acceleration of each window.
7. The device of claim 6, further comprising a transformation module to:
determining a first Hilbert transform result based on Hilbert transforming the window sample sequence;
determining a spectral signal based on a fast Fourier transform of the first Hilbert transform result;
determining a second Hilbert transform result based on performing an inverse fast Fourier transform on the spectral signal, and taking the second Hilbert transform result as the Hilbert transform result.
8. The apparatus of claim 6, wherein the fall parameters include a preliminary phase, a fall displacement of the fall, a fall time of the fall, a laser wavelength, a start position of the fall, an initial velocity of the fall, and a gravitational acceleration of the fall at the start position, the third determination module being specifically configured to:
determining an instantaneous phase of the window sample sequence from a real part and an imaginary part of the analytic signal, the real part being determined from the window sample sequence and the imaginary part being determined from the Hilbert transform result;
determining a free falling body motion trail equation according to the falling parameters;
and determining the window gravity acceleration according to the instantaneous phase and the free-fall motion trajectory equation.
9. The apparatus of claim 6, further comprising a modification module to:
correcting the window gravity acceleration according to a preset gravity gradient constant and the effective measurement height, and determining a corrected window gravity acceleration according to the corrected result;
and determining the gravity acceleration sequence according to the gravity acceleration of each correction window.
10. The device of claim 9, wherein the modification module is specifically configured to:
according to the formula g ═ g0+γhefDetermining the corrected window gravitational acceleration;
wherein g is the gravity acceleration of the correction window, g0Is the window gravitational acceleration, gamma is the preset gravitational gradient constant, hefThe height is measured for the effective measurement.
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