CN103453898B - Improve the method for north-seeking of fiber optic gyroscope precision in the presence of a harsh environment - Google Patents

Abstract

The present invention relates to one in the presence of a harsh environment, particularly improve the method for north-seeking of fiber optic gyroscope precision under severe temperature environment, according to technical scheme provided by the invention, the described method improving north-seeking of fiber optic gyroscope precision in the presence of a harsh environment, the method of described raising north-seeking of fiber optic gyroscope precision comprises the steps: s1, choose N number of measuring position point, optical fibre gyro is utilized to carry out measurement of azimuth to N number of location point, wherein, initial measurement and end measurement are carried out to the initial position point in the point of N number of measuring position, to obtain N+1 measured value, the angle intervals of adjacent two measuring position points is n=ml+1, s2, to an above-mentioned N+1 measured value, to choose k measured value be one group to order, to the angle, k measured value calculating group interior orientation in every group, s3, according to the angle, some groups of interior orientations obtained in above-mentioned steps s2, calculate required final bearing.The present invention is easy to operate, can suppress simultaneously, increase signal to noise ratio (S/N ratio), improve north finding precision, wide accommodation noise and drift.

Description

Improve the method for north-seeking of fiber optic gyroscope precision in the presence of a harsh environment

Technical field

The present invention relates to a kind of method, especially a kind of method improving north-seeking of fiber optic gyroscope precision in the presence of a harsh environment, belongs to the technical field of seeking northern orientation survey.

Background technology

Fibre optic gyroscope is a kind of novel all solid state Fibre Optical Sensor not having mechanical rotor, and it is used for measuring the angular velocity of rotation of object.Because its precision is high, anti shock and vibration ability is strong, is easy to the features such as Design and manufacture, now more and more extensive at north finder, transit, and tiltmeter etc. are sought northern directed field and used.But when environment temperature Tai Gaotai is low or acute variation time, gyrostatic drift will increase rapidly, and this can cause north finding precision sharply to decline.

In traditional north finding method, Multiple station method or N position method right and wrong method usually.Such as 4 position methods, three position methods etc.North finding precision depends on offset drift and the noise of gyro.The Measuring Time of each position of usual increase can suppress the impact of gyro noise, reduces the impact that Measuring Time can suppress offset drift.Therefore, restraint speckle and suppression offset drift conflict mutually, and particularly when environment temperature becomes severe, offset drift will significantly increase.Seek north to realize high precision, key finds the method solving restraint speckle and offset drift simultaneously.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, provide a kind of method improving north-seeking of fiber optic gyroscope precision in the presence of a harsh environment, it is easy to operate, can suppress simultaneously, increase signal to noise ratio (S/N ratio), improve north finding precision, wide accommodation noise and drift.

According to technical scheme provided by the invention, the described method improving north-seeking of fiber optic gyroscope precision in the presence of a harsh environment, the method for described raising north-seeking of fiber optic gyroscope precision comprises the steps:

S1, choose N number of measuring position point, utilize optical fibre gyro to carry out measurement of azimuth to N number of location point, wherein, initial measurement and end measurement are carried out to the initial position point in the point of N number of measuring position, to obtain N+1 measured value, the angle intervals of adjacent two measuring position points is n=ml+1;

S2, to an above-mentioned N+1 measured value, to choose k measured value be one group to order, to the angle, k measured value calculating group interior orientation in every group;

S3, according to the angle, some groups of interior orientations obtained in above-mentioned steps s2, calculate required final bearing.

In described step s1, when utilizing optical fibre gyro to measure, the Measuring Time of each position is 5 ~ 20s, and the switching time between position is 3 ~ 5s.

In described step s3, calculating mean value is carried out to angle, some groups of interior orientations and obtains final bearing.

The value of described k is 3 or 4.

Advantage of the present invention: by measuring twice to initial position in measurement initial time and end time, thus offset drift; Be divided into one group to calculate prescription parallactic angle by the every k of a measuring sequence adjacent locations, final position angle is on average obtained by prescription parallactic angle; During each measurement, Index angle gap becomes large, thus makes in the same set, and earth rate difference on three positions of same group is very large, thus improves to-noise ratio; Simultaneously, seeking in northern process, must be as quickly as possible to the transposition speed of another position from a position, being solved in gyroscope north searching process by said process can not the dilemma of restraint speckle and drift simultaneously, also can be applied to other and make gyro offset drift become large and need high precision to seek the occasion in north.

Accompanying drawing explanation

Fig. 1 is the offset drift schematic diagram of deviational survey gyro when temperature rises in existing measurement.

Fig. 2 is the schematic diagram of earth rotation component.

Fig. 3 is gyroscope north searching schematic diagram.

Fig. 4 is the schematic diagram that existing N position method seeks north.

Fig. 5 of the present inventionly seeks northern schematic diagram.

To be the present invention to seek in the test of north optical fibre gyro at the output schematic diagram of initial position to Fig. 6.

Embodiment

Below in conjunction with concrete drawings and Examples, the invention will be further described.

In order to improve north-seeking of fiber optic gyroscope precision in the presence of a harsh environment, the method for described raising north-seeking of fiber optic gyroscope precision comprises the steps:

S1, choose N number of measuring position point, utilize optical fibre gyro to carry out measurement of azimuth to N number of location point, wherein, initial measurement and end measurement are carried out to the initial position point in the point of N number of measuring position, to obtain N+1 measured value, the angle intervals of adjacent two measuring position points is n=ml+1; In general, m value makes 90 ° of < Δ θ <180 °, and l, m are integer.

When utilizing optical fibre gyro to measure, the Measuring Time of each position is 5 ~ 20s, and the switching time between position is 3 ~ 5s.In the embodiment of the present invention, by shortening the switching time between Measuring Time and position, can the error that offset drift causes effectively be suppressed.

S2, to an above-mentioned N+1 measured value, to choose k measured value be one group to order, to the angle, k measured value calculating group interior orientation in every group;

The value of described k is 3 or 4, is divided into 3 one group or 4 one group by N+1 measured value, when k is 3, according to N+1 measured value, can obtain N-1 group angle, interior orientation, when k is 4, according to N+1 measured value, can obtain N-2 group angle, interior orientation.

S3, according to the angle, some groups of interior orientations obtained in above-mentioned steps s2, calculate required final bearing.Calculating mean value is carried out to angle, some groups of interior orientations and obtains final bearing.

Illustrate below by concrete description, further illustrate feasibility and validity that the present invention carries out improving north-seeking of fiber optic gyroscope precision, particularly:

The noise of optical fibre gyro can describe by Alan's variance usually, that is:

${\mathrm{\&sigma;}}_{\mathrm{\&psi;}}^2\left({\mathrm{nT}}_0\right)=\frac{R^2{n}^2{T_0}^2}{2}+\frac{K^2{\mathrm{nT}}_0}{3}+B^2\left[\frac{2}{\mathrm{\&pi;}}\right]\ln \left(2\right)+\frac{N^2}{{\mathrm{nT}}_0}+\frac{3Q^2}{n^2{T_0}^2}---\left(1\right)$

Wherein, Q is quantizing noise coefficient, and N is white noise coefficient, and B is biased unstability index, and K is speed random walk coefficient, and R is rate slope coefficient, 1/T ₀be data sampling rate, n is integer, nT ₀show the sampling time.In above-mentioned five noise items, the variance of quantizing noise be inversely proportional to the time square, can ignore when seeking north.Biased instability and time have nothing to do.Variance and the time of white noise are inversely proportional to, so can suppress by increasing Measuring Time.Speed random walk is proportional to the time, rate ramp be proportional to the time square, so can by reduce Measuring Time suppress.Speed random walk and rate ramp can range offset drift.Therefore, offset drift and restraint speckle is suppressed to be afoul mutually.When environment temperature is severe, understand more obvious because offset drift sharply increases this conflict.

Optical fibre gyro can be expressed as following form in the output of measuring position i:

$y_i={\mathrm{\&Omega;}}_i+b_i+v_i---\left(2\right)$

Wherein, subscript i represents measuring sequence, y _iexport at the gyro of measuring position i, Ω _ithe component of earth rotation at position i, b _ioffset drift, v _iwhite noise.

As shown in Figure 1: the offset drift being certain optical fibre gyro for oil well deviational survey.When temperature rises to 70 DEG C from 25 DEG C, offset drift and rate ramp all become large.The gyro of normal temperature 0.102 °/h reaches 32.385 °/h during when temperature conditions worsens, in this case, in order to suppress offset drift, Measuring Time must shorten.But the error caused due to white noise like this will increase.Therefore, the contradiction between offset drift and white noise allows north finding precision sharply worsen.

As shown in Figures 2 and 3: gyro optical fiber is arranged on turntable, the sensitive axes of gyro optical fiber is parallel to turntable plane.Turntable adjustment level guarantees that gyro sensitive axes is parallel to surface level.The horizontal component of earth rotation has

ω _h=ω _ecosα （3）

Wherein, ω _ethe latitude of to be the autorotation speed 15.041 °/h, α of the earth be measurement point.As shown in Figure 3, in the horizontal plane, optical fibre gyro inserts to the rotation horizontal component of the different position sensing earth thus calculates geographical north.

As shown in Figure 4: be existing N position north finding method, Fig. 5 is N+1 position of the present invention north finding method, and gyro exports and can be expressed as

y _i=ω _ecosαcos(φ-θ _i)+b _i+v _i（4）

Wherein, φ is orientation, geographical north, θ _ibe the angle of measuring position i relative to reference position, and have θ _i=(i-1) Δ θ, i=1 ..., N, in order to simplify expression formula above, can obtain

y _i=acosθ _i+csinθ _i+b _i+v _i（5）

Wherein, a=ω _ecos α cos φ, c=ω _esin α sin φ, the final estimated value of position angle φ is

$\widehat{\mathrm{\&phi;}}=\arctan \frac{\hat{c}}{\hat{a}}---\left(6\right)$

Fig. 4 is that northern method is sought, wherein N=9, Δ θ=40 ° in the N position of existing level face north finding method, and Bei Fazhong is sought, N=9, m=4, l=2 in N+1 position of the present invention, Δ θ=160 °.

Bei Fazhong is sought in existing N position, the angle intervals Δ θ=2 π/N between measuring position.In the north finding method of existing N position, offset drift b _iregarded constant in each measuring position, so temperature offset drift is left in the basket completely, namely supposed b _i≈ b (i=1 ..., N), linear equation Y=AX+V can be obtained by following formula

$Y=\left[\begin{array}{c}{y}_1\\ y_2\\ .\\ .\\ .\\ y_N\end{array}\right],A=\left[\begin{array}{ccc}\cos {\mathrm{\&theta;}}_1& \sin {\mathrm{\&theta;}}_1& 1\\ \cos {\mathrm{\&theta;}}_2& \sin {\mathrm{\&theta;}}_2& 1\\ .& .& .\\ .& .& .\\ .& .& .\\ \cos {\mathrm{\&theta;}}_N& {\sin \mathrm{\&theta;}}_N& 1\end{array}\right],X=\left[\begin{array}{c}a\\ c\\ b\end{array}\right],V=\left[\begin{array}{c}{v}_1\\ v_2\\ .\\ .\\ .\\ v_N\end{array}\right]---\left(7\right)$

The least-squares estimation of linear equation is based on orthogonality of trigonometric function, this estimation can be simplified as

$\hat{a}=\frac{2}{N}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{y}_i\cos {\mathrm{\&theta;}}_i,\hat{c}=\frac{2}{N}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{y}_i\sin {\mathrm{\&theta;}}_i,\hat{b}=\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{y}_i.---\left(8\right)$

The disadvantage of the method is that it thinks that offset drift is constant b _i≈ b (i=1 ..., N), so when offset drift badly sharply can not be declined by as north finding precision during constant in environment temperature.

As shown in Figure 5: in order to compensate offset drift, we carry out twice measurement to reference position, namely start time measure once, at the end of measure once.In addition, the angle intervals Δ θ between two measuring positions increases, so the difference of the component of earth rotation in two adjacent locations can be very large.Assuming that N can be write as the form of N=ml+1, location interval can be selected

$\mathrm{\&Delta;\&theta;}=\frac{2\mathrm{m\&pi;}}{N}---\left(9\right)$

As selected N=9, we can select m=4, l=2, Δ θ=160 °, then new measuring sequence is as shown in Figure 5.

Consider that offset drift becomes large problem under severe temperature environment, we adopt grouping scheme, in the embodiment of the present invention, every three measuring positions closed on are divided into one group.Therefore, (N+1) individual position is divided into (N-1) group, so there is grouping q ₁={ λ ₁, λ ₂, λ ₃, q ₂={ λ ₂, λ ₃, λ ₄..., q _j={ λ _j, λ _j+1, λ _j+2..., q _n-1={ λ _n-1, λ _n, λ _n+1, wherein, q _j, j=1 ..., N-1 is grouping, and λ is measured value; To often organizing q _j, optical fibre gyro exports and is

$\left\{\begin{array}{c}{y}_j=a\cos {\mathrm{\&theta;}}_j+c\sin {\mathrm{\&theta;}}_j+b_j+v_j\\ y_{j+1}=a\cos {\mathrm{\&theta;}}_{j+1}+c\sin {\mathrm{\&theta;}}_{j+1}+b_{j+1}{+v}_{j+1}\\ y_{j+2}=a\cos {\mathrm{\&theta;}}_{j+2}+c\sin {\mathrm{\&theta;}}_{j+2}+b_{j+2}{+v}_{j+2}\end{array}\right.---\left(10\right)$

Concerning often organizing, because Measuring Time is relatively short, we can suppose b ₁≈ b ₂≈ b ₃, b ₂≈ b ₃≈ b ₄..., b _n-1≈ b _n≈ b _n+1so we can obtain organizing the position angle that often group calculates for

${\hat{a}}_j=\frac{\sin {\mathrm{\&theta;}}_j(y_{j+1}-y_{j+2})+\sin {\mathrm{\&theta;}}_{j+1}(y_{j+2}-y_j)+\sin {\mathrm{\&theta;}}_{j+2}(y_j-y_{j+1})}{\sin {\mathrm{\&theta;}}_j(\cos {\mathrm{\&theta;}}_{j+1}-\cos {\mathrm{\&theta;}}_{j+2})+{\sin \mathrm{\&theta;}}_{j+1}(\cos {\mathrm{\&theta;}}_{j+2}-\cos {\mathrm{\&theta;}}_j)+\sin {\mathrm{\&theta;}}_{j+2}({\cos \mathrm{\&theta;}}_j-{\cos \mathrm{\&theta;}}_{j+1})}---\left(11\right)$

${\hat{c}}_j=\frac{\cos {\mathrm{\&theta;}}_j(y_{j+1}-y_{j+2})+\cos {\mathrm{\&theta;}}_{j+1}(y_{j+2}-y_j)+\cos {\mathrm{\&theta;}}_{j+2}(y_j-y_{j+1})}{\cos {\mathrm{\&theta;}}_j(\sin {\mathrm{\&theta;}}_{j+1}-\sin {\mathrm{\&theta;}}_{j+2})+\cos {\mathrm{\&theta;}}_{j+1}(\sin {\mathrm{\&theta;}}_{j+2}-\sin {\mathrm{\&theta;}}_j)+\cos {\mathrm{\&theta;}}_{j+2}(\sin {\mathrm{\&theta;}}_j-\sin {\mathrm{\&theta;}}_{j+1})}---\left(12\right)$

${\widehat{\mathrm{\&phi;}}}_j=\arctan \frac{{\hat{c}}_j}{{\hat{a}}_j}.---\left(13\right)$

Because Measuring Time is relatively short, the error caused due to offset drift is suppressed greatly.The error at the angle, group interior orientation calculated mainly comes from white noise.Then be averaged to angle, all groups of interior orientations, white noise is also suppressed obtains final bearing.

$\widehat{\mathrm{\&phi;}}=\underset{j=1}{\overset{N-1}{\mathrm{\&Sigma;}}}{\widehat{\mathrm{\&phi;}}}_j/(N-1)---\left(14\right)$

Notice formula (11) and formula (12), in the item in output speed, have y _j+1-y _j+2, y _j+2-y _jand y _j-y _j+1, in the embodiment of the present invention, by increasing angular spacing Δ θ, the difference organizing interior three position earth rotation components is larger, can improve to-noise ratio like this.Special in N is larger, increase interval, measuring position and to optimize sequence of positions very necessary.Switching time between diverse location also must be as far as possible short.By this series of measures, gyroscope north searching precision can improve greatly.In the embodiment of the present invention, when utilizing optical fibre gyro to measure, the Measuring Time of each position is 5 ~ 20s, and the switching time between position is 3 ~ 5s; By above-mentioned set of time, can ensure the time requirement of position conversion and the requirement to each measurement point Measuring Time.

In order to prove validity of the present invention and reliability further, adopt a deviational survey gyroscope to carry out seeking north test, wherein, optical fibre gyro is column type, diameter 32mm.Concerning logging Application, when temperature is elevated to 70 DEG C from room temperature, optical fibre gyro seek northern error be less than ± 1.5 °.We adopt existing method and method of the present invention to carry out seeking north operation respectively.

Shown in the comparison following table of new aging method, the sampling rate of gyro is 10Hz, and each position measurement time is 10 seconds.

Table 1 north finding method compares, reference azimuth θ _r=82.148 °

Can notice from table 1, use classic method, all measurement of azimuth values are all lower than true bearing angle θ _r=82.148 °.There is systematic error in existing north finding method, this is because rate ramp exists slowly drift.Fig. 6 represents that optical fibre gyro is at position 1(initial position when temperature rises to 70 DEG C from 25 DEG C) 17 times export.Rate ramp causes systematic error.By contrast, present invention inhibits rate ramp.Experiment display the method applied in the present invention is maximum, and to seek northern error be 0.941 °, and the maximum error that the north is sought in existing N position is 3.525 °, this means that method of the present invention can inhibit 73.3% to error.

The present invention is by measuring twice to initial position in measurement initial time and end time, thus offset drift; Be divided into one group to calculate prescription parallactic angle by the every k of a measuring sequence adjacent locations, final position angle is on average obtained by prescription parallactic angle; During each measurement, Index angle gap becomes large, thus makes in the same set, and earth rate difference on three positions of same group is very large, thus improves to-noise ratio; Simultaneously, seeking in northern process, must be as quickly as possible to the transposition speed of another position from a position, being solved in gyroscope north searching process by said process can not the dilemma of restraint speckle and drift simultaneously, also can be applied to other and make gyro offset drift become large and need high precision to seek the occasion in north.

Claims (3)

1. improve a method for north-seeking of fiber optic gyroscope precision in the presence of a harsh environment, it is characterized in that, the method for described raising north-seeking of fiber optic gyroscope precision comprises the steps:

(s1) N number of measuring position point, is chosen, utilize optical fibre gyro to carry out measurement of azimuth to N number of location point, wherein, initial measurement and end measurement are carried out to the initial position point in the point of N number of measuring position, to obtain N+1 measured value, the angle intervals of adjacent two measuring position points is

M value makes 90 ° of < Δ θ <180 °, and l, m are integer;

(s2), to an above-mentioned N+1 measured value, to choose k measured value be one group to order, to the angle, k measured value calculating group interior orientation in every group; During concrete grouping: (N+1) individual position is divided into (N-1) group, so there is grouping q ₁={ λ ₁, λ ₂, λ ₃, q ₂={ λ ₂, λ ₃, λ ₄..., q _j={ λ _j, λ _j+1, λ _j+2..., q _n-1={ λ _n-1, λ _n, λ _n+1, wherein, q _j, j=1 ..., N-1 is grouping, and λ is measured value;

(s3), according to the angle, some groups of interior orientations obtained in above-mentioned steps (s2), calculating mean value obtains final bearing.

2. the method improving north-seeking of fiber optic gyroscope precision in the presence of a harsh environment according to claim 1, it is characterized in that: in described step (s1), when utilizing optical fibre gyro to measure, the Measuring Time of each position is 5 ~ 20s, and the switching time between position is 3 ~ 5s.

3. the method improving north-seeking of fiber optic gyroscope precision in the presence of a harsh environment according to claim 1, is characterized in that: the value of described k is 3 or 4.