CN114527520A - Vibration compensation method for correcting interference fringes of atomic interference gravimeter - Google Patents
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Abstract
The invention discloses a vibration compensation method for correcting interference fringes of an atomic interference gravimeter, which comprises the following steps: s1, setting a sweep frequency rate sequence, a gravity reference value, a pulse interval duration and a valid wave vector; s2, importing measured data; s3, calculating and setting an optimization target through the original stripes; s4, dividing the vibration sensor signal according to the trigger signal to obtain a vibration sensor signal corresponding to each transition probability; s5, setting a delay coefficient and a starting range of a gain coefficient; s6, obtaining an optimal delay coefficient and an optimal gain coefficient by a traversal search method or a golden section search method; and S7, calculating the vibration speed of the reference mirror during each atomic interference through the optimal delay coefficient and the optimal gain coefficient, further obtaining a vibration phase noise sequence, an atomic phase sequence only affected by vibration and a correction fringe, and finally calculating to obtain an RMSE value when the correction fringe is fitted to the standard cosine signal.
Description
Technical Field
The invention relates to the field of gravity measurement, in particular to a vibration compensation method for correcting interference fringes of an atomic interference gravimeter.
Background
Absolute gravity measurement, namely accurate measurement of the absolute value of gravity acceleration, is widely applied to the fields of auxiliary navigation, resource exploration, geophysical and measurement. The existing high-precision absolute gravimeter generally adopts a free-fall method, and mainly comprises a laser interference type absolute gravimeter taking a pyramid prism as a falling object and an atomic interference type absolute gravimeter taking a cold atomic group as the falling object, which are respectively referred to as an optical gravimeter and an atomic gravimeter hereinafter. The former measures the motion track of free falling of a pyramid prism in vacuum through a laser interferometer, and solves the gravity acceleration through fitting, and the latter calculates the gravity acceleration according to atom interference fringes formed by three times of Raman laser pulse action in the free falling process of atomic groups. Since the actual measurement object of both is the acceleration of the motion of the falling object or the falling radical relative to a reference mirror (corner cube or flat mirror) in the instrument, the acceleration of the reference mirror itself must be coupled into the measurement result. Theoretically, when the vibration of the reference mirror is neglected, the measurement precision of the existing absolute gravimeter can reach the micro-Gal magnitude; in practice, however, if the reference mirror is placed directly on the ground, the dispersion of the measurements caused by ground vibrations will exceed ten micro-gal, even of the order of milligal or deca-gal in a complex vibration environment. Therefore, obtaining the motion acceleration of the reference mirror by using the vibration measuring instrument and correcting the influence of the motion acceleration when calculating the gravity acceleration is one of effective means for improving the measurement accuracy of the absolute gravimeter, and the correction method is generally called vibration compensation.
Specifically, the ground vibration noise affecting the atomic gravimeter is mainly environmental noise, and is related to the measurement time and the ground, coordinates and environment of the measurement point, and can be roughly distinguished according to the frequency. The first is human activity noise, typically greater than 1Hz, such as walking by people nearby during instrument testing, vibrations from artificial vibration sources such as vehicles, and building jolts. Secondly, the noise from the earth itself is generally between 0.1Hz and 1Hz and mainly comprises vibration caused by the earth internal motion such as periodic earth pulsation and earthquake, wherein the acceleration power spectral density of the earth pulsation noise model has peaks at the positions with the frequencies of 0.2Hz and 3 Hz. Finally, atmospheric motion noise such as air pressure fluctuation and the like is generally less than 0.1Hz, generally changes slowly, has low amplitude and has negligible influence on absolute gravity measurement. Because absolute gravity measurement only depends on displacement data in the vertical direction for calculation, when the atom interference fringes are subjected to vibration compensation, the horizontal component of ground vibration is generally ignored, and only a vertical vibration signal output by a vibration measuring instrument is needed.
The existing internationally mature atomic gravimeter is a CAG-01 type atomic gravimeter developed by a Paris astronomical stage of France, and the international gravity comparison is carried out for a plurality of times, and the adopted vibration processing method is the combination of a passive vertical vibration isolation system and vibration compensation, wherein the specific principle of the vibration compensation is as follows: the data acquisition card synchronously records a speed signal and an atomic interference fringe output by the seismometer in the atomic interference process, an IIR (Infinite Impulse Response) filter and a non-causal low-pass filter are used for processing the seismometer signal in control software, so that the influences of inconstant amplitude-frequency characteristic and non-linear phase-frequency characteristic of a transfer function of the seismometer are reduced, a more real vibration signal of the reference mirror is obtained, finally, phase noise introduced by the vibration of the reference mirror is obtained by using the processed signal, and the atomic interference fringe is corrected. In the measuring environment of the instrument, the vibration compensation method can improve the sensitivity of the gravimeter by 3 times. The university of hannover, germany, proposes to preprocess the output signal of the vibration sensor with digital low-pass and high-pass filters to obtain more accurate phase noise introduced by the vibration of the reference mirror, thereby realizing vibration compensation. The experimental result shows that the sensitivity of the gravimeter can be effectively improved by utilizing a high-precision commercial seismometer to perform vibration compensation in a quieter environment or by utilizing a commercial accelerometer with lower precision or a novel optical inertial sensor independently developed by the commercial accelerometer in a complex vibration environment.
In China, the homemade atomic gravimeter of Zhejiang university also adopts a vibration compensation method, and the method is mainly characterized in that commercial inversion software is used for correcting the influence of the actual measurement transfer function of the seismometer to obtain a more real vibration signal of the reference mirror (as shown in figure 1). In its laboratory environment, the method can increase the sensitivity of the gravimeter to levels close to those when passive vibration isolation systems are used. The national defense science and technology university carries out detailed analysis on measurement noise introduced by vertical vibration and horizontal deflection of the reference mirror, the accelerometer is used for measuring the vibration of the reference mirror when the atomic gravimeter works, and meanwhile, the transfer function between the accelerometer and the reference mirror is calibrated more accurately. The actual measurement result shows that the vibration compensation method can realize obvious vibration compensation effect in a more complex vibration environment. The vibration compensation method proposed by the national defense innovation institute of military science institute adopts the Michelson laser interferometer with the high-precision four-channel phase-shift detector to replace the traditional vibration sensor. The interferometer can directly measure the phase shift of the atomic interference fringes, and determine the change of the phase fraction of the atomic interference fringes before and after the Raman laser pulse action by combining the methods of signal shaping, digital phase discrimination and the like to obtain the atomic interference phase deviation caused by the vibration of the reference mirror. And removing the phase deviation, and correcting the transition probability signal measured by the gravimeter. In addition, different types of vibration isolation systems have been developed by units such as the China metrological science research institute, the Chinese academy of sciences precision measurement research institute, the Huazhong university of science and technology, the China university of science and technology, the national defense university of science and technology, the American Stanford university, the Germany Hongbu university and the like, so as to reduce the influence of ground vibration on the atomic gravimeter.
However, the existing atomic gravimeter has poor adaptability, and when the measurement environment changes, the vibration compensation effect is obviously reduced, thereby affecting the measurement accuracy of the atomic gravimeter, and therefore, it is necessary to improve the existing atomic gravimeter.
Disclosure of Invention
The present invention is directed to solve the above problems, and an object of the present invention is to provide a vibration compensation method for correcting interference fringes of an atomic interference gravimeter, which has an optimal compensation effect in each measurement environment.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a vibration compensation method for correcting interference fringes of an atomic interference gravimeter, comprising the steps of:
s1, setting a sweep frequency rate sequence, a gravity reference value, pulse interval duration and a significant wave vector;
s2, importing measured data;
s3, calculating and setting an optimization target through the original stripes;
s4, dividing the vibration sensor signal according to the trigger signal to obtain a vibration sensor signal corresponding to each transition probability;
s5, setting a delay coefficient and a starting range of a gain coefficient;
s6, obtaining an optimal delay coefficient and an optimal gain coefficient by a traversal search method or a golden section search method;
and S7, calculating the vibration speed of the reference mirror during each atomic interference through the optimal delay coefficient and the optimal gain coefficient, further obtaining a vibration phase noise sequence, an atomic phase sequence only affected by vibration and a correction fringe, and finally calculating to obtain an RMSE value when the correction fringe is fitted to the standard cosine signal.
Further, in the step S2, the measured data includes a measured transition probability sequence corresponding to the sweep rate sequence, a vertical direction output signal of the vibration sensor for measuring the vibration of the reference mirror in the same time period, and a trigger signal before each radical falls in the same time period.
Further, in step S3, the optimization target is one of an RMSE value at the time of the original fringe fitting, a coefficient that can be determined at the time of the original fringe fitting, a standard deviation of interference fringe residuals, and a correlation coefficient between the original fringe residuals and the fringe residuals affected only by the vibration.
Further, in step S4, the vibration sensor signal is subjected to a filtering process operation using a corrector transfer function.
Further, in step S6, when the traversal search method or the golden section search method is used to obtain the optimal delay coefficient and the optimal gain coefficient, and when the optimization target is the RMSE value at the time of fitting the original fringe, the delay coefficient and the gain coefficient corresponding to the RMSE value at the time of fitting the original fringe reaching the minimum value are used as the optimal delay coefficient and the optimal gain coefficient;
when the optimization target is a coefficient which can be determined during the fitting of the original stripe, taking a delay coefficient and a gain coefficient which correspond to the coefficient which can be determined during the fitting of the original stripe and reaches the minimum value as an optimal delay coefficient and an optimal gain coefficient;
when the optimization target is the standard deviation of the interference fringe residual error, taking a corresponding delay coefficient and a corresponding gain coefficient as an optimal delay coefficient and an optimal gain coefficient when the standard deviation of the interference fringe residual error reaches a minimum value;
when the optimization target is a correlation coefficient between the original fringe residual and the fringe residual affected only by vibration, taking a corresponding delay coefficient as an optimal delay coefficient when the absolute value of the correlation coefficient between the original fringe residual and the fringe residual affected only by vibration reaches a maximum value; and taking the corresponding gain coefficient when the other optimization targets reach the minimum value as the optimal gain coefficient.
Further, in step S7, when the vibration velocity of the reference mirror at each time of atomic interference is calculated by the optimal delay coefficient and the optimal gain coefficient, and when the vibration sensor is an earthquake timer, the calculation formula is:
in the formula, vm(t) is the vibration speed of the reference mirror; tau is the optimal delay coefficient; k is the optimal gain coefficient; u shapes(t) is the seismometer output signal; v. ofsThe sensitive mass vibration speed of the seismometer; ksIs the nominal sensitivity of the seismometer;
when the vibration sensor is an accelerometer, the calculation formula is as follows:
in the formula, vm(t) is the vibration speed of the reference mirror; tau is the optimal delay coefficient; k is the optimal gain coefficient; kaIs the nominal sensitivity of the accelerometer; u shapea(t) is the accelerometer output signal.
Further, in step S7, when the vibration speed of the reference mirror is calculated by the optimal delay coefficient and the optimal gain coefficient at each atomic interference, and when the vibration sensor is an accelerometer, the vibration speed of the reference mirror is calculated by using a half-cycle integration algorithm.
Compared with the prior art, the invention has the advantages and positive effects that:
the method has excellent adaptability to the environment, can realize the best vibration compensation effect at the time and in the local when the measuring environment changes, solves the problem that the vibration compensation effect of the existing vibration compensation method is relatively reduced when the measuring environment changes, and effectively improves the vibration compensation effect of the atomic gravimeter in the vibration environment, thereby improving the measuring precision of the atomic gravimeter and further making certain contribution to the measurement work of the absolute gravity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a flow chart of a vibration compensation method of Zhejiang industry university;
FIG. 2 is a schematic diagram of atomic interference fringes;
FIG. 3 is a frame diagram of seismometer output signal versus true vibration of the reference mirror;
FIG. 4 is a flowchart of a vibration compensation algorithm of embodiment 1;
FIG. 5 is a flowchart of a vibration compensation algorithm of embodiment 2;
fig. 6 is a flowchart of the vibration compensation algorithm of embodiment 10.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived from the embodiments of the present invention by a person skilled in the art without any creative effort, should be included in the protection scope of the present invention.
General principle for vibration compensation of interference fringes of atomic interference gravimeter
The atomic gravimeter is based on the cold atomic substance wave interference principle, applies laser pulse to cold atomic groups, and realizes the atomic interference process through a two-photon stimulated Raman transition or multi-photon Bragg diffraction process. Taking an atomic gravimeter based on stimulated Raman transition as an example, a cold atomic group freely falls in a vacuum cavity, a plane reference mirror below the vacuum cavity reflects a Raman laser beam vertically downwards to make two beams of oppositely emitted laser simultaneously act on the atomic group, in the process, three continuous laser pulses realize beam splitting, inversion and beam combination of atomic wave packets, namely a 1 st pi/2 pulse, a pi pulse and a 2 nd pi/2 pulse, and the time interval of adjacent pulses is T. Atoms in any energy state after combination are formed by overlapping atoms on two paths, and the transition probability P of the atomic group after pulse action, namely interference fringes, can be detected through a fluorescence signal to meet the requirement
Wherein, Delta phi is an atomic phase and is related to the local gravity acceleration g; coefficients a and B representing the fringe contrast can be obtained by cosine fitting the interference fringes. Ideally, the atomic phase Δ Φ is equal to its theoretical value Δ ΦthI.e. by
ΔΦth＝(keffg-α)T2. (2)
Wherein k iseffAlpha represents the sweep rate of the laser for the effective wave vector. And if the alpha in the control software regulation and control formula (2) of the gravimeter is linearly increased, the atomic phase delta phi also linearly changes, so that the interference fringes are in a standard cosine signal form. In this case P should be matched to the standard signal PfitAre identical to that of
However, in practice, the atomic phase Δ Φ is equal to its actual value Δ Φ due to various phase noise effectsmIs provided with
Wherein, isvibPhase noise introduced for the vibration of the reference mirror, hereinafter referred to simply as vibration phase; delta phi others is the sum of the phase noise introduced by other noise sources, hereinafter referred to as other phase noise. At this time P is represented by PfitBecome into
When the vibration phase is dominant in the phase noise, the vibration compensation process for correcting the interference fringe P can be determined according to the above principle.
First, the original measured stripe P (delta phi)th) A cosine fit was performed (note: the stripe is a curve, the ordinate outside the bracket is the ordinate of the curve, and the abscissa inside the bracket is the abscissa of the curve), and the fitted theoretical stripe P is obtainedfit(ΔФth) And coefficients A and B in the formula (1).
Secondly, obtaining the real vibration speed v of the reference mirror in a period of time t through a vibration sensormAnd then according to
Calculating the true vibration phase delta phivibWhere S (T) is the sensitivity function of the gravimeter, T1And T3The action time of the 1 st pi/2 pulse and the 2 nd pi/2 pulse respectively is determined by the known parameters of the gravimeter control software. It should be noted that although the gravity value g is an unknown quantity to be measured, an approximate rough measurement value g may be used in the initial stage of actual measurementthSubstitution formula (2) for calculating theoretical atomic phase delta phithTo obtain a fitted fringe PfitAnd then obtaining an accurate measured value g through subsequent measurement and signal processing.
Thirdly, calculating the atomic phase delta phi only influenced by vibrationvAnd the transition probability PvI.e. by
At this time, the angle is increased again by Delta phivData pairs P (Δ Φ) obtained for abscissa and P for ordinatev) I.e. the corrected interference fringes, and the compensation process is finished. As shown in fig. 2, with the original fringe P (Δ Φ)th) In contrast, the fringe P (Δ Φ) is correctedv) Should theoretically be closer to the standard cosine signal, i.e. the theoretical stripe P is fittedfit(ΔФth). That is, for the corrected fringe P (Δ Φ)v) The goodness of fit when cosine fitting is carried out again is higher than that of the original stripe P (delta phi)th) Goodness of fit when fitting was performed.
Secondly, the specific principle of the vibration compensation method described in the invention
The method for simplifying the model based on the transfer function to realize the vibration compensation process comprises two aspects of hardware and software.
In terms of hardware, a separate seismometer or accelerometer is placed beside or below the reference mirror to measure the vibration. Taking seismometer as an example, the output signal U of the seismometer is limited by the mechanical structure and the performance of the seismometers(t) does not reflect the vibration velocity v of the reference mirror completely trulym(t) the relationship is shown in FIG. 3, wherein GaRepresenting the transfer function from the ground vibration speed to the vibration speed of the reference mirror, GbRepresenting the transfer function from the ground vibration velocity to the vibration velocity of the sensitive mass of the seismometer, GcRepresenting the transfer function from the velocity of motion of the sensitive mass to the output voltage of the seismometer. Since the sensitive mass inside the seismometer is necessarily different horizontally and vertically from the actual position of the reference mirror, the reference mirror is a mirror of a reference mirrorGaAnd GbIt is not possible to be equal and the two transfer functions may themselves change as the ground material changes.
On the other hand, the transfer function G of the seismometer itselfcThe amplitude-frequency characteristic is not constant, the phase-frequency characteristic is a linear ideal transfer function, and may change with the measurement time and the environment (because the environmental parameters such as temperature, humidity, air pressure, etc. affect the parameters of the electromechanical module inside the seismometer, and the parameters may drift with the time). In summary, the transfer function H between the true vibration velocity of the reference mirror and the voltage signal output by the seismometer satisfies
Although in the actual case Ga、Gb、GcThe measurement environment does not change significantly in a single gravity measurement task, and the measurement time generally does not exceed 24 hours, so that H can be estimated by using a simplified model consisting of a delay coefficient tau and a gain coefficient K, and the values of the two coefficients are considered to remain unchanged in the current measurement process. From this, the simplified model of FIG. 3 can be derived as
Wherein, KsIs the nominal sensitivity of the seismometer, provided by the manufacturer.
Theoretically, when the delay coefficient tau and the gain coefficient K are closest to the true value, the voltage U is output from the seismometersThe reference mirror vibration velocity v calculated from the equation (9)mAnd the correction effect on the stripes is best because the correction effect is closest to the true value. The specific idea of vibration compensation is therefore: giving the value ranges of tau and K, selecting a parameter value representing goodness of fit as an optimization target, and searching for the corresponding optimal value when the parameter reaches the optimal valueDelay coefficient tauoptAnd an optimum gain factor Kopt. After the search is finished, setting the delay to be tauoptA gain of KoptIn the case of (2), the corrected fringe P (Δ Φ) is obtainedv) The parameter values as optimization targets are recalculated.
Due to the fact that the seismometer has its own transfer function GcIs not in an ideal form, namely the characteristics of non-constant amplitude-frequency characteristic, non-linear phase-frequency characteristic and the like, so that the output signal U of the seismometers(t) distortion may be present. Therefore, before searching for the delay coefficient τ and the gain coefficient K, a correction filter F may be used first for the signal Us(t) processing to reduce the distortion degree.
The hardware part is replaced by an accelerometer from a seismometer, and the output signal U of the accelerometer can be directly processeda(t) carrying out primary integration, and combining the delay coefficient and the gain coefficient to obtain a vibration signal v of the reference mirrorm(t)。
The corresponding calculation formula is
Wherein, KaNominal sensitivity for the accelerometer, provided by the manufacturer; the integration time is set according to actual needs and at least comprises the whole time period of free falling of the atomic groups. Other integration algorithms such as half-cycle integration may also be used to derive the accelerometer signal U from the accelerometer signala(t) calculating a reference mirror velocity signal vm(t)。
Third, example
(1) Example 1
A vibration compensation method for correcting interference fringes of an atomic interference gravimeter is characterized by comprising the following steps: the method comprises the following steps:
s1, setting a sweep frequency rate sequence, a gravity reference value, pulse interval duration and a significant wave vector;
s2, importing an actual measurement transition probability sequence corresponding to the sweep frequency rate sequence, a vibration sensor vertical direction output signal for measuring the vibration of the reference mirror in the same time period, and a trigger signal before each time of the radical falling in the same time period;
s3, calculating and setting the RMSE value as the optimization target when fitting the original stripes through the original stripes;
s4, segmenting the seismometer signals according to the trigger signals to obtain seismometer signals corresponding to each transition probability;
s5, setting a delay coefficient and a starting range of a gain coefficient;
s6, solving an optimal delay coefficient and an optimal gain coefficient through a traversal search method;
and S7, calculating the vibration speed of the reference mirror during each atomic interference through the optimal delay coefficient and the optimal gain coefficient, further obtaining a vibration phase noise sequence, an atomic phase sequence only affected by vibration and a correction fringe, and finally calculating to obtain an RMSE value when the correction fringe is fitted to the standard cosine signal.
In this embodiment, the hardware sensor is a seismometer, and the output signal is Us(t) of (d). With the RMSE value (Root Mean Square Error) during stripe fitting as an optimization target, firstly, the search delay coefficient tau is traversed, and then, the search gain coefficient K is traversed. Respectively corresponding delay coefficient and gain coefficient are taken as tau when RMSE value reaches minimum valueoptAnd Kopt. The specific algorithm flow is shown in fig. 4.
(2) Example 2
The steps are the same as those of the embodiment 1, the RMSE value during the fitting of the stripes is still taken as an optimization target, and the embodiment 2 adopts a golden section method to search the delay coefficient tau and the gain coefficient K at the same time. The specific algorithm flow is shown in fig. 5.
(3) Example 3
For seismometer signal U after data preprocessing in FIG. 4s(t) adding a correction step, namely filtering the signal by using a set corrector transfer function F, wherein a specific filter function can be independently written or a function library of software can be used. The procedure of "search for optimum parameters by traversal" and "calculation of result" in embodiment 1 is then performed on the corrected signal.
(4) Example 4
To fit the stripesTaking R-square (coefficient of decision) as an optimization target, and respectively taking a corresponding delay coefficient and a corresponding gain coefficient as tau when the R-square value reaches a minimum valueoptAnd Kopt. The method of searching for the delay factor search and the gain factor K is the same as in embodiment 1, i.e., the traversal search.
(5) Example 5
Taking R-square (coefficient of solution) as optimization target when fitting stripe, and taking the corresponding delay coefficient and gain coefficient as tau when R-square value reaches minimum valueoptAnd Kopt. The search delay factor and the search gain factor K are the same as those in embodiment 2, that is, the golden section method is adopted.
(6) Example 6
The RMSE values have simple and intuitive mathematical meanings, but physical meanings are not obvious. Another more physically meaningful variable can therefore be used as an optimization target, namely the change in the fringe fitting residual. The step of searching the coefficients is the same as that in embodiment 1, and the search delay coefficient τ is traversed first, and then the search gain coefficient K is traversed.
Before running the vibration compensation algorithm, the original fringe P (delta phi) is calculatedth) Compared with the theoretical stripe Pfit(ΔФth) Residual error R ofm(ΔФth) Standard deviation of (a)m. When the vibration compensation algorithm is operated, given the current delay coefficient tau, the interference fringes P affected only by vibration are obtained according to the equations (6), (7) and (9)vCompared with the theoretical stripe PfitResidual error R ofv. At the same time, note the original stripe P and the stripe P only affected by vibrationvIs Rc. It is clear that RcI.e. the original fringe residual RmResidual R from stripes affected only by vibrationvThe difference of (3) corresponds to a streak residual after removal of the influence of vibration. Theoretically, the better the vibration compensation effect, the vibration phase delta phivibThe more accurate the calculation of (A), the more the deduced fringe residual R introduced only by the vibrationvThe closer to the original fringe residual Rm. At this time RcWill tend to be dominated by other phase noise only delta phiothersIntroduced streak residual, its standard deviation σcShould also tend towards a minimum. Thus, example 6 will σcSet as optimization target, at σcWhen the minimum value is reached, the corresponding delay coefficient and gain coefficient are respectively tauoptAnd Kopt(ii) a The search method for the delay coefficient and the gain coefficient is the same as that of embodiment 1, i.e., the search is performed in a respective traversal manner.
(7) Example 7
Using the interference fringe residual standard deviation sigma in example 6cTo optimize the objective, the golden section method in embodiment 2 is adopted, and the delay coefficient τ and the gain coefficient K are searched simultaneously.
(8) Example 8
As described in example 6, theoretically, the better the vibration compensation effect, the calculated fringe residual R introduced only by vibrationvThe closer to the original fringe residual Rm. Thus example 8 with RmAnd RvCorrelation coefficient C ofRFor optimizing the target, the search delay coefficient tau is traversed by CRThe absolute value of (d) reaches the maximum value, the corresponding delay factor is tauopt。
Since the raw data needs to be normalized when calculating the correlation coefficient, CRAnd cannot be used as an optimization target when searching for gain coefficients. The RMSE value in embodiment 1 may be used here as an optimization target for the traversal search gain factor K.
(9) Example 9
With the correlation coefficient C in example 8RAnd searching the delay coefficient tau in a traversing way for optimizing the target. Further using the interference fringe residual standard deviation sigma in the embodiment 6cAnd traversing and searching the gain coefficient K for the optimization target.
(10) Example 10
The hardware sensor of vibration compensation is replaced by an accelerometer, and the output signal is Ua(t) of (d). At the moment, the first-time integration is adopted and the time delay coefficient and the gain coefficient are combined to obtain the time delay coefficient and the gain coefficienta(t) obtaining a vibration velocity signal v of the reference mirrorm(t) of (d). Still like the step of embodiment 1, with the RMSE value when fitting the stripe as the optimization target, the search for the delay coefficient τ and the gain coefficient K is traversed respectively. The specific algorithm flow is shown in fig. 6.
(11) Example 11
The vibration-compensated hardware sensor is still an accelerometer, in example 10 from the acceleration signal Ua(t) calculating the velocity signal vmThe method of (t) employs a half-cycle integration method. And still taking the RMSE value when the stripes are fitted as an optimization target, and respectively traversing and searching the delay coefficient tau and the gain coefficient K.
The method has excellent adaptability to the environment, can realize the best vibration compensation effect at the time and in the local when the measuring environment changes, solves the problem that the vibration compensation effect of the existing vibration compensation method is relatively reduced when the measuring environment changes, and effectively improves the vibration compensation effect of the atomic gravimeter in the vibration environment, thereby improving the measuring precision of the atomic gravimeter and further making certain contribution to the measurement work of the absolute gravity.
Claims (7)
1. A vibration compensation method for correcting interference fringes of an atomic interference gravimeter is characterized in that: the method comprises the following steps:
s1, setting a sweep frequency rate sequence, a gravity reference value, pulse interval duration and a significant wave vector;
s2, importing measured data;
s3, calculating and setting an optimization target through the original stripes;
s4, dividing the vibration sensor signal according to the trigger signal to obtain a vibration sensor signal corresponding to each transition probability;
s5, setting a delay coefficient and a starting range of a gain coefficient;
s6, obtaining an optimal delay coefficient and an optimal gain coefficient by a traversal search method or a golden section search method;
and S7, calculating the vibration speed of the reference mirror during each atomic interference through the optimal delay coefficient and the optimal gain coefficient, further obtaining a vibration phase noise sequence, an atomic phase sequence only affected by vibration and a correction fringe, and finally calculating to obtain an RMSE value when the correction fringe is fitted to the standard cosine signal.
2. The vibration compensation method for correcting interference fringes of an atomic interference gravimeter according to claim 1, characterized in that: in step S2, the measured data includes a measured transition probability sequence corresponding to the sweep rate sequence, a vertical output signal of the vibration sensor for measuring the vibration of the reference mirror in the same time period, and a trigger signal before each radical drop in the same time period.
3. The vibration compensation method for correcting interference fringes of an atomic interference gravimeter according to claim 2, characterized in that: in step S3, the optimization target is one of the RMSE value at the time of the original fringe fitting, the coefficient of reliability at the time of the original fringe fitting, the standard deviation of the interference fringe residual, and the correlation coefficient between the original fringe residual and the fringe residual affected only by the vibration.
4. The vibration compensation method for correcting interference fringes of an atomic interference gravimeter according to claim 1, characterized in that: in step S4, the vibration sensor signal is subjected to a filter processing operation using a corrector transfer function.
5. The vibration compensation method for correcting interference fringes of an atomic interference gravimeter according to claim 3, characterized in that: in step S6, when the traversal search method or the golden section search method is used to obtain the optimal delay coefficient and the optimal gain coefficient, and when the optimization target is the RMSE value at the time of fitting the original fringe, the delay coefficient and the gain coefficient corresponding to the RMSE value at the time of fitting the original fringe reaching the minimum value are used as the optimal delay coefficient and the optimal gain coefficient;
when the optimization target is a coefficient which can be determined during the fitting of the original stripe, taking a delay coefficient and a gain coefficient which correspond to the coefficient which can be determined during the fitting of the original stripe and reaches the minimum value as an optimal delay coefficient and an optimal gain coefficient;
when the optimization target is the standard deviation of the interference fringe residual error, taking a corresponding delay coefficient and a corresponding gain coefficient as an optimal delay coefficient and an optimal gain coefficient when the standard deviation of the interference fringe residual error reaches a minimum value;
when the optimization target is a correlation coefficient between the original fringe residual and the fringe residual affected only by vibration, taking a corresponding delay coefficient as an optimal delay coefficient when the absolute value of the correlation coefficient between the original fringe residual and the fringe residual affected only by vibration reaches a maximum value; and taking the corresponding gain coefficient when the other optimization targets reach the minimum value as the optimal gain coefficient.
6. The vibration compensation method for correcting interference fringes of an atomic interference gravimeter according to claim 5, characterized in that: in step S7, when the vibration velocity of the reference mirror at each time of atomic interference is calculated by the optimal delay coefficient and the optimal gain coefficient, and when the vibration sensor is an earthquake timer, the calculation formula is:
in the formula, vm(t) is the vibration speed of the reference mirror; tau is the optimal delay coefficient; k is the optimal gain coefficient; u shapes(t) is the seismometer output signal; v. ofsThe sensitive mass vibration speed of the seismometer; ksIs the nominal sensitivity of the seismometer;
when the vibration sensor is an accelerometer, the calculation formula is as follows:
in the formula, vm(t) is the vibration speed of the reference mirror; tau is the optimal delay coefficient; k is the optimal gain coefficient; kaIs the nominal sensitivity of the accelerometer; u shapeaAnd (t) is an accelerometer output signal.
7. The vibration compensation method for correcting interference fringes of an atomic interference gravimeter according to claim 5, characterized in that: in the step S7, when the vibration speed of the reference mirror is calculated by the optimal delay coefficient and the optimal gain coefficient at each atomic interference, and when the vibration sensor is an accelerometer, the vibration speed of the reference mirror is calculated by using a half-cycle integration algorithm.
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