CN103453898A - Method for improving north-seeking precision of fiber-optic gyroscope in severe environment - Google Patents

Abstract

The invention relates to a method for improving the north-seeking precision of a fiber-optic gyroscope in a severe environment, particularly in a severe temperature environment. According to the technical scheme provided by the invention, the method for improving the north-seeking precision of the fiber-optic gyroscope in the severe environment comprises the following steps of s1. selecting N measuring positions, and carrying out measurement of azimuth on the N measuring points by utilizing the fiber-optic gyroscope, wherein initial measurement and ending measurement are performed on the initial position in the N measuring positions so as to obtain N+1 measured values, and the angle interval of every two adjacent measuring positions is delta theta=2mpi/N, N=m1+1; s2. sequentially selecting k measured values as one group according to the N+1 measured values, and calculating the intra-group azimuth angles of the K measured values in the group; s3. calculating the needed final azimuth angle according to a plurality of groups of intra-group azimuth angles obtained in the step s2. According to the method, the operation is convenient, noise and drift can be inhibited simultaneously, the signal to noise ratio is increased, the north-seeking precision is improved, and the application scope is large.

Description

Improve the method for north-seeking of fiber optic gyroscope precision under rugged surroundings

Technical field

The present invention relates to a kind of method, especially a kind of method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings, belong 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 that there is no mechanical rotor, and it is used for measuring the angular velocity of rotation of object.Because its precision is high, the anti shock and vibration ability is strong, is easy to the characteristics such as Design and manufacture, is more and more extensively seeking northern instrument now, transit, and tiltmeters etc. are sought northern directed field and are used.But, when environment temperature Tai Gaotai is low or during acute variation, gyrostatic drift will increase rapidly, this can cause north finding precision sharply to descend.

In traditional north finding method, Multiple station method or N position method right and wrong are the method for use usually.Such as 4 Fa，San position, position methods etc.North finding precision depends on offset drift and the noise of gyro.Usually the Measuring Time that increases each position can suppress the impact of gyro noise, reduces the impact that Measuring Time can suppress offset drift.Therefore, suppress noise and suppress offset drift and mutually conflict, particularly, when environment temperature becomes severe, offset drift will significantly increase.In order to realize that high precision seeks north, key is to find solution to suppress the method for noise and offset drift simultaneously.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art, a kind of method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings is provided, it is easy to operate, can suppress noise and drift simultaneously, increases signal to noise ratio (S/N ratio), improves north finding precision, wide accommodation.

According to technical scheme provided by the invention, the described method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings, the method for described raising north-seeking of fiber optic gyroscope precision comprises the steps:

S1, choose N measuring position point, utilize optical fibre gyro to carry out measurement of azimuth to N location point, wherein, the initial position point in N measuring position point is carried out to initial measurement and end measurement, 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 be measured, the Measuring Time of each position is 5～20s, and be 3～5s the switching time between position.

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

The value of described k is 3 or 4.

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

The accompanying drawing explanation

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

The schematic diagram that Fig. 2 is the earth rotation component.

Fig. 3 is the gyroscope north searching schematic diagram.

Fig. 4 seeks northern schematic diagram for existing N position method.

Fig. 5 is the northern schematic diagram of seeking of the present invention.

Fig. 6 optical fibre gyro that is the present invention in seeking the north test is at the output schematic diagram of initial position.

Embodiment

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

In order to improve the north-seeking of fiber optic gyroscope precision under rugged surroundings, the method for described raising north-seeking of fiber optic gyroscope precision comprises the steps:

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

n=ml+1; In general, the m value makes 90 °<Δ θ<180 °, l, and m is integer.

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

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 about to N+1 measured value and is divided into 3 one group or 4 one group, 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 in angle, some groups of interior orientations and obtain final bearing.

Description explanation below by concrete, further illustrate feasibility and validity that the present invention is improved the north-seeking of fiber optic gyroscope precision, particularly:

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

${\mathrm{\&sigma;}}_{\mathrm{\&psi;}}^2\left({\mathrm{nT}}_0\right)=\frac{R^2{n}^2{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="HDA0000378991180000032.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}^2}{2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="HDA0000378991180000022.png,HDA0000378991180000031.png"\; state="\{\{state\}\}">K</figure-callout>}}^2{\mathrm{<figure-callout\; id="0"\; label="nT"\; filenames="HDA0000378991180000032.png"\; state="\{\{state\}\}">nT</figure-callout>}}_0}{3}+B^2\left[\frac{2}{\mathrm{\&pi;}}\right]\ln \left(2\right)+\frac{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA0000378991180000022.png,HDA0000378991180000031.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}{{\mathrm{<figure-callout\; id="0"\; label="nT"\; filenames="HDA0000378991180000032.png"\; state="\{\{state\}\}">nT</figure-callout>}}_0}+\frac{3Q^2}{n^2{{\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="HDA0000378991180000032.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}^2}---\left(1\right)$

Wherein, Q is the quantizing noise coefficient, and N is the white noise coefficient, and B is the biasing unstability index, and K is the speed random walk coefficient, and R is the speed 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, seeking in northern and can ignore.Biasing instability and time-independent.Variance and the time of white noise are inversely proportional to, so can suppress by increasing Measuring Time.The speed random walk is proportional to the time, rate ramp be proportional to the time square, so can suppress by reducing Measuring Time.Speed random walk and rate ramp can range offset drift.Therefore, it is afoul mutually suppressing offset drift and suppress noise.When environment temperature is severe, due to offset drift, sharply to increase this conflict meeting more obvious.

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 means measuring sequence, y _ithe gyro output at measuring position i, Ω _ithe component of earth rotation at position i, b _ioffset drift, v _iwhite noise.

As shown in Figure 1: be the offset drift for certain optical fibre gyro of oil well deviational survey.When temperature rises to 70 ℃ from 25 ℃, it is large that offset drift and rate ramp all become.When the gyro of 0.102 °/h of normal temperature reaches 32.385 °/h when temperature conditions worsens, in this case, in order to suppress offset drift, Measuring Time must shorten.Yet 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, and the sensitive axes of gyro optical fiber is parallel to the turntable plane.Turntable adjustment level guarantees that the gyro sensitive axes is parallel to surface level.The horizontal component of earth rotation has

ω _h=ω _ecosα （3）

Wherein, ω _ebe the 15.041 °/h of autorotation speed of the earth, α is the latitude of measurement point.As shown in Figure 3, on surface level, thereby inserting to the rotation horizontal component of the different position sensing earth, optical fibre gyro calculates geographical north.

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

y _i=ω _ecosαcos(φ-θ _i)+b _i+v _i （4）

Wherein, φ is the orientation, geographical north, θ _ibe the angle of measuring position i with respect to reference position, and θ is arranged _i=(i-1) Δ θ, i=1 ..., N, in order to simplify top expression formula, 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

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

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

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

$Y=\left[\begin{array}{c}{y}_1\\ y_2\\ .\\ .\\ .\\ y_N\end{array}\right],A=\left[\begin{array}{ccc}\cos {\mathrm{\&theta;}}_1& \sin {\mathrm{\&theta;}}_1& 1\\ \cos {\mathrm{\&theta;}}_2& \sin {\mathrm{\&theta;}}_2& 1\\ .& .& .\\ .& .& .\\ .& .& .\\ \cos {\mathrm{\&theta;}}_N& {\sin \mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000378991180000022.png,HDA0000378991180000031.png"\; state="\{\{state\}\}">N</figure-callout>}}& 1\end{array}\right],X=\left[\begin{array}{c}a\\ c\\ b\end{array}\right],V=\left[\begin{array}{c}{v}_1\\ v_2\\ .\\ .\\ .\\ v_N\end{array}\right]---\left(7\right)$

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 severe and can not sharply descend by north finding precision by as constant the time in environment temperature.

As shown in Figure 5: in order to compensate offset drift, we carry out twice measurement to reference position, when starting, measure once, during end, measure once.In addition, the angle intervals Δ θ between two measuring positions increases, so the difference of the component of earth rotation on two adjacent locations can be very large.Suppose 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 select N=9, and we can select m=4, l=2, and 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 the grouping scheme, in the embodiment of the present invention, every three measuring positions of closing on are divided into to one group.Therefore, (N+1) individual position is divided into (N-1) group, so grouping q is arranged 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, λ is measured value; To every group of q _j, optical fibre gyro output 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 every group, 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 every batch total obtains

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 angle, all groups of interior orientations is averaged, white noise is the suppressed final bearing that obtains also.

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

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

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

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 °

From table 1, can notice, 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, and this is because there is slowly drift in rate ramp.Fig. 6 means that optical fibre gyro is at position 1(initial position when temperature rises to 70 ℃ from 25 ℃) 17 times output.Rate ramp causes systematic error.By contrast, the present invention has suppressed rate ramp.Experiment shows that it is 0.941 ° that the method applied in the present invention maximum is sought northern error, and to seek northern maximum error be 3.525 ° in existing N position, this means that method of the present invention can suppress 73.3% to error.

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

Claims (4)

1. a method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings, is characterized in that, the method for described raising north-seeking of fiber optic gyroscope precision comprises the steps:

(s1), choose N measuring position point, utilize optical fibre gyro to carry out measurement of azimuth to N location point, wherein, the initial position point in N measuring position point is carried out to initial measurement and end measurement, 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.

2. the method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings according to claim 1, it is characterized in that: in described step (s1), when utilizing optical fibre gyro to be measured, the Measuring Time of each position is 5～20s, and be 3～5s the switching time between position.

3. the method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings according to claim 1, is characterized in that: in described step (s3), calculating mean value is carried out in angle, some groups of interior orientations and obtain final bearing.

4. the method that improves the north-seeking of fiber optic gyroscope precision under rugged surroundings according to claim 1, it is characterized in that: the value of described k is 3 or 4.

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