CN104634364A - Fiber-optic gyroscope scale factor self-calibration system based on step pulse modulation - Google Patents

Abstract

The invention belongs to the field of inertial sensitive components, and in particular relates to a self-calibration method of the optical fiber gyroscope scale factor based on the step wave modulation proposed by the digital closed-loop optical fiber gyroscope step wave modulation principle. The invention includes: recording the digital quantity output by the gyroscope; using the full circle calibration method when calculating the data respectively; inputting the angular velocity into the corresponding gyroscope output; Naike phase difference; add the calculated digital quantity to the FPGA using VHDL language; use the least square method to find the slope. The calibration method proposed by the present invention is not based on the turntable, and can solve the problem that if the input angular rate of the turntable is too small during the calibration process of the turntable, the gyroscope will be in the nonlinear region, and the accuracy of the calibrated scaling factor is not high; The difficulty requirement of the turntable removes the influence of the accuracy and performance of the inertial measurement element on the calibration results.

Description

A Self-Calibration Method of Fiber Optic Gyroscope Scale Factor Based on Ladder Wave Modulation

technical field

The invention belongs to the field of inertial sensitive components, and in particular relates to a self-calibration method of the optical fiber gyroscope scale factor based on the step wave modulation proposed by the digital closed-loop optical fiber gyroscope step wave modulation principle.

Background technique

The working principle of the strapdown inertial navigation system is to convert its output to the navigation coordinate system through the strapdown matrix, combine certain initial information, and then determine the speed, position and attitude information of the carrier through certain navigation calculations. However, as an autonomous navigation system, the strapdown inertial navigation system will inevitably have some system errors during use. If these errors are not corrected in time, the navigation accuracy of the system will eventually be affected. To compensate these errors, it must first be calibrated with high-precision inertial measurement devices, so the research on calibration technology is of great significance to improve the navigation accuracy of the whole system.

At the present stage, the calibration of the fiber optic gyroscope scale factor in the SINS is mainly done through the speed test of the turntable. The advantage of this calibration method is that its principle is simple, and it is convenient for laboratory implementation. This method establishes the relationship between its input and output by analyzing the error equation of the inertial component, and designs a reasonable calibration path through the analysis to stimulate the various parameters in the error equation. In the actual working process of the inertial navigation system, the calibration results are compensated to improve the navigation accuracy of the system. However, in the experiment of its existence, if the input angular rate of the turntable is too small, the gyro will be in the nonlinear region, and the accuracy of the calibrated scale factor is not high; if the angular rate is too large, the difficulty requirements for the turntable will be increased; if the sampling points are too dense, the time cost will be increased. Too high; too sparse sampling points will increase the risk of measurement error; this calibration method is based on a turntable and must be carried out in the laboratory. In practical applications, it cannot effectively improve work efficiency and is relatively cumbersome.

From the above problems, it can be seen that the calibration efficiency of the fiber optic gyroscope’s scaling factor is not high at present, and new methods are needed to improve the efficiency.

Contents of the invention

The purpose of the present invention is to propose a self-calibration method of the optical fiber gyroscope scale factor based on step wave modulation.

The purpose of the present invention is achieved like this:

Including the following steps:

(1) Through the existing calibration method, it can be seen that during the calibration process, when the input angular rate of the turntable is around 20°/s, the scale factor has good linearity and high calibration accuracy. s and 1°/s are the step lengths to find the digital quantity of the corresponding staircase wave signal. Through the turntable speed experiment, the angles of 20°/s, 20.01°/s, 20.1°/s, and 21°/s are recorded respectively. In the case of speed input, the digital output of the gyro;

(2) Calculate the mean value of the gyro output when the turntable rotates around the X, Y, and Z axes under different speed conditions The whole circle calibration method is used for data processing, and the data of the whole circle is taken so that the component of the earth's rotation angular velocity on the horizontal axis can be averaged out when the platform rotates one circle, and the calibration accuracy is improved;

When the input angular rate is 20°/s; rotate a circle at an angular velocity of 20°/s T=360/20=18s; intercept the data of the 20s-560s of the positive and negative Z-axis respectively, and the number of rotations N=30; When reversing around the Z axis, the sum of gyroscope output digital quantities ∑N _gz+ , ∑N _gz-

When reversing around the X axis, we get

When turning forward and backward around the Y axis, we get

get at the same time

(3) Make the difference between the digital value obtained in step (2), and obtain the gyro output corresponding to the angular velocity input of each axis of 0.01°/s, 0.1°/s, and 1°/s respectively:

(4) According to the step wave modulation principle of the digital closed-loop fiber optic gyroscope, when the fiber optic loop is sensitive to angular velocity, the two beams of light with different transmission directions in the fiber loop will produce a Sagnac phase difference Φ _s proportional to the rotation rate Ω as

${\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;LD</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;c</span>}}\mathrm{<span\; class="notranslate">\; \&Omega;</span>}$

The step wave is added to the phase modulator of the Y waveguide, and the phase difference between the two beams of light caused by it is

Φ _j ＝Φ _m (t)-Φ _m (t-τ)

Among them, Φ _m (t) is the additional phase shift of light transmitted clockwise caused by step wave modulation, and Φ _m (t-τ) is the additional phase shift of light transmitted counterclockwise caused by step wave modulation; the bias signal A square wave is used, the period of the square wave signal is 2τ, the square wave modulation signal is used as a bias signal, and the phase shift generated in the positive and negative half cycles is Then the non-reciprocal phase shift produced by the step wave and square wave in the Sagnac interferometer is:

ΔΦ=Φ _s +Φ _j +Φ _f ,

Where Φ _s is the Sagnac phase shift, Φ _j is the additional phase shift of the ladder wave, and Φ _f is the additional phase shift of the square wave;

The output signal of the sagnac interferometer is

I=A·[1+cos(Φ _s +Φ _j +Φ _f )],

In the positive half cycle of the square wave, the output signal of the sagnac interferometer is

I=A·[1-sin(Φ _s +Φ _j )],

In the negative half cycle of the square wave, the output signal of the sagnac interferometer is

I=A·[1+sin(Φ _s +Φ _j )],

Subtract the output signals of the positive half cycle and the negative half cycle of the square wave to get

ΔI=-2Asin(Φ _s +Φ _j ),

When ΔI≠0, ΔI can be used as the feedback quantity to control the step wave height, so that Φ _s + Φ _j tends to 0. In the digital closed-loop fiber optic gyro system, the step height is the angular rate signal output by the gyro;

(5) Add the calculated digital quantity to the FPGA using VHDL language to generate a staircase wave with equal gradients and equal time intervals. The duration is 1 minute. Through digital signal processing, the optical fiber ring is generated without being sensitive to angular velocity. Non-reciprocal phase shift, record the digital output of the gyro at this time;

(6) Obtain the output data point by step (5), get the average value of a section of data of the output digital quantity corresponding to the angular rate ω _j successively, obtain the output N _j0 corresponding to the rate point; intercept the part of the fiber optic gyroscope when the test begins Calculate the average value N ₀ of the output, then N _j =N _j0 -N ₀ , eliminate the influence of the earth's rotation angular velocity on the test results, use the least square method to fit the straight line N _j =K·ω _j +N ₀ , and use the least square method to obtain Find the slope K

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}{<span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>$

Among them, M is the number of input angular rates, and K is the scaling factor of the gyroscope.

Step (1) Take 0.01°/s, 0.1°/s, 1°/s as the step size to find the digital quantity of the corresponding staircase wave signal,

When the turntable rotates at 20°/s, the gyro output digital value N is measured _{to be 20°/s}

_{20°/s outside} N = _{20°/s inside} N

When the turntable rotates at 20.01°/s, the gyro output digital value N is measured _{to be 20.01°/s}

_{20.01°/s outside} N = _{20.01°/s inside} N

ΔN _{inner 0.01°/s} = N _{inner 20.01°/s} -N _{inner 20°/s} = N _{outer 20.01°/s} -N _{outer 20°/s}

When rotating at angular rates of 20.1°/s and 21°/s, it can be obtained

ΔN _{inner 0.1°/s} = N _{inner 20.1°/s} -N _{inner 20°/s} = N _{outer 20.1°/s} -N _{outer 20°/s}

ΔN _{inner 1°/s} = N _{inner 21°/s} - N _{inner 20°/s} = N _{outer 21°/s} - N _{outer 20°/s} .

The beneficial effects of the present invention are:

(1) The calibration method proposed by the present invention is not based on the turntable, and can solve the problem that the input angular rate of the turntable is too small during the calibration of the turntable, which will cause the gyroscope to be in the nonlinear region, and the accuracy of the calibrated scale factor is not high; The problem of the difficulty requirement of the turntable is added, and the influence of the accuracy and performance of the inertial measurement element on the calibration result is removed.

(2) After finding the relationship between the gradient of the added digital staircase wave signal and the fitted angular rate input, the sampling point density can be set arbitrarily, which solves the problem that the time cost is too high if the sampling points are too dense in the existing calibration method; If the points are too sparse, the risk of measurement error increases.

(3) This calibration method makes the calibration not limited by the occasion, and can be used for on-site calibration, which greatly improves the calibration efficiency.

Description of drawings

Fig. 1 is method flowchart of the present invention;

Figure 2 is a schematic diagram of the self-calibration of the fiber optic gyroscope scale factor.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

The invention aims at proposing a new calibration method so that the calibration process can be realized without a turntable and improves the calibration efficiency. This method intends to add a ladder wave signal to the digital signal processing part of the closed-loop fiber optic gyroscope, and change the phase difference between the two lights through the Y waveguide. In this way, the input of the angular velocity of the turntable is simulated, and the scale factor can be fitted under the static base. And calculate its non-linear error, in order to achieve the purpose of calibration.

The present invention comprises the following steps:

Step 1. In order to find the digital quantity of the staircase wave signal corresponding to the step length of 0.01°/s, 0.1°/s, and 1°/s, record 20°/s, 20.01°/s, 20.1 °/s, 21°/s angular rate input, the digital output of the gyro.

Step 2. Calculate the average value of the gyro output when the turntable rotates around the X, Y, and Z axes under different speed conditions The whole circle calibration method is used in data processing, and the data of the whole circle is taken so that the component of the earth's rotation angular velocity on the horizontal axis can be averaged out when the platform rotates once, so as to improve the calibration accuracy.

Step 3. The average value of the digital quantity obtained in step 2 is subtracted to obtain the gyroscope output corresponding to the angular velocity input of each axis of 0.01°/s, 0.1°/s, and 1°/s respectively.

Step 4. According to the step wave modulation principle of the digital closed-loop fiber optic gyroscope, the step height of the digital step wave signal is proportional to the angular rate of the gyroscope. According to this principle, the corresponding relationship between the step height of the digital staircase wave signal and the gyro input can be found.

Step 5. Obtain the above data, that is, after finding the corresponding relationship _between the ΔN and the planned input angular rate, add the calculated digital quantity to the FPGA using VHDL language. Make it generate a ladder wave with equal gradient and equal time interval (duration is 1 minute), and artificially make the optical fiber ring produce non-reciprocal phase shift without being sensitive to angular velocity through digital signal processing. Record the digital output of the gyro at this time.

Step 6: A series of output data points can be obtained from step 5, and a segment of output digital data corresponding to the angular rate ω _j is taken in turn to calculate the average value, and the output N _j0 corresponding to the rate point is obtained. Intercept the output of part of the fiber optic gyroscope at the beginning of the test to calculate the average value N ₀ , then N _j =N _j0 -N ₀ , to eliminate the influence of the earth's rotation angular velocity on the test results. And use the least squares method to fit the straight line N _j =K·ω _j +N ₀ to find the slope K, which is the scale factor of the gyroscope.

The invention proposes a fiber optic gyroscope self-calibration method based on the digital closed-loop fiber optic gyroscope step wave modulation principle, which can use digital step wave signals to fit the angular rate input of the turntable without using the turntable, so as to achieve the purpose of calibration. This method enables the calibration of the fiber optic gyroscope not to be performed under laboratory conditions, greatly improves the calibration efficiency, and removes the error caused by the inertial measurement element to the calibration.

The present invention is a fiber optic gyroscope self-calibration method based on the digital closed-loop fiber optic gyroscope ladder wave modulation principle. The flow chart is shown in Figure 1, including the following steps:

Step 1 is to find the digital quantity of the staircase wave signal corresponding to the steps of 0.01°/s, 0.1°/s, and 1°/s.

When the turntable rotates at 20°/s, the gyro output digital value N is measured _{to be 20°/s}

At this time, it is considered that _{20°/s outside} N = _{20°/s inside} N

When the turntable rotates at 20.01°/s, the gyro output digital value N is measured _{to be 20.01°/s}

At this time, it is considered that _{20.01°/s outside} N = _{20.01°/s inside} N

Then there is _{0.01°/s in} ΔN = _{20.01°/s in N - 20°/s} in N = _{20.01° /s} outside N - _{20°/s outside} N

Similarly, when rotating at an angular rate of 20.1°/s and 21°/s, it can be obtained

ΔN _{inner 0.1°/s} = N _{inner 20.1°/s} -N _{inner 20°/s} = N _{outer 20.1°/s} -N _{outer 20°/s}

ΔN _{inner 1°/s} = N _{inner 21°/s} -N _{inner 20°/s} = N _{outer 21°/s} -N _{outer 20°/s}

Through the turntable rate experiment, record the digital output of the gyro under the input conditions of angular rates of 20°/s, 20.01°/s, 20.1°/s, and 21°/s. The steps are as follows:

1. The X, Y, and Z axes of the fiber optic gyroscope coordinate system, when we fix the fiber optic gyroscope on the turntable, we can strictly consider that the rotation axes of the inner, middle and outer frames of the turntable and our fixed strapdown inertial components are strictly parallel.

2. Position the turntable. Make the rotation axis of the turntable perpendicular to the rotation axis of the outer frame and keep the rotation axis of the outer frame parallel to the local vertical line, so that through the positioning of the turntable, it can always ensure that the rotation axis of the inner frame of the turntable points north horizontally, meeting our design requirements . Perform an angular rate experiment. Adjust the Z-axis of the fiber optic gyro to a position parallel to the local vertical.

3. Carry out the angular rate experiment. Adjust the Z-axis of the fiber optic gyro to a position parallel to the local vertical.

4. Make the outer frame of the turntable rotate at an angular velocity of 20°/s for 10 minutes, then rotate at the same angular velocity in the opposite direction for 10 minutes, and record the output of the gyro during the rotation.

5. Adjust the X and Y axes of the fiber optic gyro to a position parallel to the local vertical line. And repeat step 4.

6. Repeat the above steps to make the outer frame of the turntable rotate at the angular speeds of 20°/s, 20.01°/s, 20.1°/s, and 21°/s respectively.

Step 2. Calculate the average value of the gyro output when the turntable rotates around the X, Y, and Z axes under different speed conditions The whole circle calibration method is used in data processing, and the data of the whole circle is taken so that the component of the earth's rotation angular velocity on the horizontal axis can be averaged out when the platform rotates once, so as to improve the calibration accuracy.

When the input angular rate is 20°/s

Turn around at an angular velocity of 20°/s T=360/20=18s

Intercept the data of the 20s-560s of the positive and negative rotation of the Z-axis respectively (the number of rotations N=30)

When the positive and negative rotation around the Z axis is calculated, the sum of the gyroscope output digital quantities ∑N _gz+ and ∑N _gz- during the positive and negative rotation is calculated, then it can be calculated

Similarly, when rotating forward and backward around the X axis, we can get

When turning forward and backward around the Y axis, we can get

The same reason can be obtained

Step 3. The average value of the digital quantity obtained in step 2 is subtracted to obtain the gyroscope output corresponding to the angular velocity input of each axis of 0.01°/s, 0.1°/s, and 1°/s respectively.

Step 4. According to the staircase wave modulation principle of the digital closed-loop fiber optic gyroscope, when the fiber optic loop is sensitive to angular velocity, the two beams of light with different transmission directions in the fiber optic loop will produce a Sagnac phase difference Φ _s proportional to the rotation rate Ω as

${\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;LD</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;c</span>}}\mathrm{<span\; class="notranslate">\; \&Omega;</span>}$

The step wave is added to the phase modulator of the Y waveguide, and the phase difference between the two beams of light caused by it is

Φ _j ＝Φ _m (t)-Φ _m (t-τ)

Among them, Φ _m (t) is the additional phase shift of the clockwise transmitted light caused by step wave modulation, and Φ _m (t-τ) is the additional phase shift of counterclockwise transmitted light caused by step wave modulation.

The bias signal is a square wave, the period of the square wave signal is 2τ, the square wave modulation signal is used as the bias signal, and the phase shift generated in the positive and negative half cycles is

Then the non-reciprocal phase shift generated in the Sagnac interferometer for the step wave and the square wave is:

ΔΦ＝Φ _s +Φ _j +Φ _f

Among them, Φ _s is the Sagnac phase shift, Φ _j is the additional phase shift of the step wave, and Φ _f is the additional phase shift of the square wave.

At this time, the output signal of the sagnac interferometer is

I＝A·[1+cos(Φ _s +Φ _j +Φ _f )]

In the positive half cycle of the square wave, the output signal of the sagnac interferometer is

I＝A·[1-sin(Φ _s +Φ _j )]

In the negative half cycle of the square wave, the output signal of the sagnac interferometer is

I＝A·[1+sin(Φ _s +Φ _j )]

Subtract the output signals of the positive half cycle and the negative half cycle of the square wave to get

ΔI＝-2Asin(Φ _s +Φ _j )

It can be seen from the above formula that if you want to ensure that the sagnac interferometer works near zero phase, that is, keep ΔI≈0, you must ensure that Φ _s +Φ _j ≈0. When ΔI≠0, you can use ΔI as the feedback quantity control ladder wave height such that Φ _s +Φ _j ≈0. Therefore, in the digital closed-loop fiber optic gyroscope system, the step height is the angular rate signal output by the gyroscope.

Step 5. Obtain the above data, that is, after finding the corresponding relationship _between the ΔN and the planned input angular rate, add the calculated digital quantity to the FPGA using VHDL language. Make it generate a ladder wave with equal gradient and equal time interval (duration is 1 minute), and artificially make the optical fiber ring produce non-reciprocal phase shift without being sensitive to angular velocity through digital signal processing. Record the digital output of the gyro at this time.

Step 6: A series of output data points can be obtained from step 5, and a segment of output digital data corresponding to the angular rate ω _j is taken in turn to calculate the average value, and the output N _j0 corresponding to the rate point is obtained. Intercept the output of part of the fiber optic gyroscope at the beginning of the test to calculate the average value N ₀ , then N _j =N _j0 -N ₀ , to eliminate the influence of the earth's rotation angular velocity on the test results. And use the least square method to fit the straight line N _j =K·ω _j +N ₀ , the least square method (also known as the least square method) is a mathematical optimization technique to find the best function matching of the data by minimizing the square sum of errors. The slope K can be obtained by the method of least squares.

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}{<span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Among them, M is the number of input angular rates, and K is the scaling factor of the gyroscope.

Claims (2)

1., based on an optical fibre gyro self-calibrating method for digital closed-loop optic fiber gyroscope Staircase wave principle, it is characterized in that, comprise the steps:

(1) can be found out in calibration process by existing scaling method, the scale factor linearity of turntable input angle speed when 20 °/about s is good and stated accuracy is high, and want with 0.01 °/s, 0.1 °/s, 1 °/s is the digital quantity that step-length finds the step signal of its correspondence, by turntable rate experiments, record respectively 20 °/s, 20.01 °/s, 20.1 °/s, under this several angular speed input condition of 21 °/s, the digital quantity that gyro exports;

(2) under calculating different rates condition respectively, the gyro of turntable when X, Y, Z axis is rotated exports average with whole circle standardization during data processing, the data rounding circle make the component of rotational-angular velocity of the earth on transverse axis on average can fallen when stage body rotates a circle, and improve stated accuracy;

When input angle speed is 20 °/s; One week T=360/20=18s is rotated with the angular velocity of 20 °/s; Intercept the data of the 20s-560s of Z axis forward and backward respectively, rotate number of turns N=30; When around Z axis rotating, when having calculated forward and backward, gyro exports digital quantity summation Σ N _gz+, Σ N _gz-

When X-axis rotating,

When Y-axis rotating,

Obtain simultaneously

(3) the digital quantity average that step (2) obtains is done difference, obtain respectively each axle 0.01 °/s, 0.1 °/s, gyro that the turning rate input of 1 °/s is corresponding exports:

(4) according to the Staircase wave principle of digital closed-loop optic fiber gyroscope, when fiber optic loop sensitivity is to angular velocity, the two-beam that in optical fiber loop, transmission direction is different is proportional to the Sagnac phase differential Φ of speed of rotation Ω by producing _sfor

${\mathrm{\&Phi;}}_s=\frac{2\mathrm{\&pi;LD}}{\mathrm{\&lambda;c}}\mathrm{\&Omega;}$

Staircase waveform is added on the phase-modulator of Y waveguide, and the phase differential between the two-beam caused is

Φ _j＝Φ _m(t)-Φ _m(t-τ)

Wherein, Φ _mt additional phase shift that () causes the light of clockwise transmission to produce for Staircase wave, Φ _mthe additional phase shift that (t-τ) causes the light of counterclockwise transmission to produce for Staircase wave; Offset signal is that the cycle of this square-wave signal is 2 τ with square wave, and square-wave modulation signal is as offset signal, and the phase shift produced in positive-negative half-cycle is then staircase waveform and square wave, the nonreciprocal phase shift produced in Sagnac interferometer is:

ΔΦ＝Φ _s+Φ _j+Φ _f，

Wherein Φ _sfor Sagnac phase shift, Φ _jfor the additional phase shift of staircase waveform, Φ _ffor the additional phase shift of square wave;

The output signal of sagnac interferometer is

I＝A·[1+cos(Φ _s+Φ _j+Φ _f)]，

At the positive half cycle of square wave, the output signal of sagnac interferometer is

I＝A·[1-sin(Φ _s+Φ _j)]，

At the negative half period of square wave, the output signal of sagnac interferometer is

I＝A·[1+sin(Φ _s+Φ _j)]，

The signal subtraction that positive for square wave half cycle and negative half period export is obtained

ΔI＝-2Asin(Φ _s+Φ _j)，

When Δ I ≠ 0, just can control staircase waveform height with Δ I as feedback quantity, make Φ _s+ Φ _jlevel off to 0, in digital closed-loop optic fiber gyroscope system, ladder height is exactly the angle rate signal that gyro exports;

(5) VHDL language is utilized to be added on FPGA calculating gained digital quantity, generation gradient is equal, the staircase waveform that the time interval is also equal, duration is 1 minute, making fiber optic loop when not having responsive to produce nonreciprocal phase shift to when angular velocity by digital signal processing, recording the digital quantity of now gyro output;

(6) obtained exporting data point by step (5), get angular speed ω successively _jthe one piece of data of corresponding output digital quantity is averaged, and obtains the output N that this speed point is corresponding _j0; The gyrostatic output quantity of part fiber intercepted when test starts is averaged N ₀, then N _j=N _j0-N ₀, eliminate rotational-angular velocity of the earth to the impact of test result, with least square fitting straight line N _j=K ω _j+ N ₀, obtain slope K by least square method

$K=\frac{\underset{j=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_j{F}_j-\frac{1}{M}\underset{j=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_j\underset{j=1}{\overset{M}{\mathrm{\&Sigma;}}}{F}_j}{\underset{j=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_j^2-\frac{1}{M}{\left(\underset{j=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_j\right)}^2},$

Wherein M is the constant multiplier of the number of input angle speed, K and gyro.

2. a kind of optical fibre gyro self-calibrating method based on digital closed-loop optic fiber gyroscope Staircase wave principle according to claim 1, it is characterized in that: described step (1) with 0.01 °/s, 0.1 °/s, 1 °/s is the digital quantity that step-length finds corresponding step signal

When turntable rotates with 20 °/s, measure gyro and export digital quantity N _{outer 20 °/s}

N _{outer 20 °/s}=N _{interior 20 °/s}

When turntable rotates with 20.01 °/s, measure gyro and export digital quantity N _{outer 20.01 °/s}

N _{outer 20.01 °/s}=N _{interior 20.01 °/s}

Δ N _{interior 0.01 °/s}=N _{interior 20.01 °/s}-N _{interior 20 °/s}=N _{outer 20.01 °/s}-N _{outer 20 °/s}

Can obtain when rotating with the angular speed of 20.1 °/s, 21 °/s

Δ N _{interior 0.1 °/s}=N _{interior 20.1 °/s}-N _{interior 20 °/s}=N _{outer 20.1 °/s}-N _{outer 20 °/s}

Δ N _{interior 1 °/s}=N _{interior 21 °/s}-N _{interior 20 °/s}=N _{outer 21 °/s}-N _{outer 20 °/s}.