CN103940593B - A kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms - Google Patents

Abstract

The invention discloses a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms. Adopt digital sawtooth signal to modulate electrooptic modulator; Rear composition result sequence is sampled, processed to sawtooth signal by increasing progressively traversal one by one, to sawtooth signal modulation result under different cycles in cycle span; In result sequence, in sawtooth signal cycle corresponding to minimum of a value, calculate first measurement result; Set cycle span for the second time by first measurement result, repeat above step and obtain measurement result sequence for the second time; By sawtooth signal cycle corresponding to its minimum of a value, calculate measurement result for the second time, obtain the final optical fibre gyro transition time. The present invention can do not add any testing equipment or during prerequisite under quick test optical fibre gyro transition time, solve the transition time variation issue being caused by optical system adjustment in optical fibre gyro production process, meet flexibly through engineering approaches, the mass production of optical fibre gyro.

Description

A kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms

Technical field

The present invention relates to a kind of processing method of signal of fiber optical gyroscope, relate in particular to a kind of based on digital sawtooth waveformsOptical fibre gyro transition time method for fast measuring.

Background technology

Light is propagated one week needed time and is called the transition time in optical fibre gyro has the light path of reciprocity.Mostly adopt at present the technological means of digital closed loop both at home and abroad in middle high-precision optical fiber gyro research field, pass throughElectrooptic modulator is modulated optical fibre gyro, and analog-digital converter is by the output analog voltage signal of optical fibre gyroBe converted to data signal, carry out differential ference spiral processing by digital signal processor. Electrooptic modulator is mainly doneWith having two: time delay differential modulation, the operating bias that changes optical fibre gyro puts to improve sensitivity, the linearity;The phase difference detecting is fed back, realize optical fibre gyro closed loop policy.

Zero bias stability is the key index of optical fibre gyro, and the method that improves zero bias stability is to reduce integratedThe modulation error of photoelectricity phase-modulator. The main cause that causes modulation error comprise the modulation signal half period andTransition time is unequal, modulation channels is non-linear and electrooptic modulator nonlinearity etc. Modulation signal halfCycle and transition time are unequal is topmost factor, and the existence of this error can make optical fibre gyro produce phaseClose skew, be equivalent to the error component that superposes in the output signal of optical fibre gyro, make optical fibre gyro essenceDegree declines with resolution ratio, and therefore zero bias stability is more subject to environmental change impact. Therefore, Measurement accuracy optical fiberThe gyro transition time also chooses with this basic premise that be raising zero bias stability suitable modulation period.

The transition time of optical fibre gyro is determined by length and the refractive index of fiber optic loop. In process of production, optical fiberThe refractive index of ring can think that approximate constant, transition time are mainly determined by the length of fiber optic loop, can be with thisObtain the estimated value of transition time, precision is about 50ns magnitude, can not meet wanting of middle high-precision optical fiber gyroAsk. In addition, in optical fibre gyro production process, there is the mutual welding of multiple photoelectric devices, the meeting of fiber optic loop lengthAgain change, after all photoelectric device assemblings, whole fiber optic loop is just determined. Therefore needOne method, can optical fibre gyro assemble complete after, do not need additional devices, equipment, only rely on get overTime Estimate value, realizes the Quick Measurement of optical fibre gyro transition time by signal processing, meet and measure essenceDegree reaches the requirement of optical fibre gyro through engineering approaches simultaneously.

Summary of the invention

Measurement accuracy requirement to the transition time in producing at present middle high-precision optical fiber gyro through engineering approaches, separatesThe transition time variation issue certainly causing because of optical system adjustment in production process, the object of the invention is to carryFor a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms.

The technical solution used in the present invention comprises that step is as follows:

1) adopt digital sawtooth signal to modulate electrooptic modulator, the peak-to-peak value of this sawtooth signal is solidFixed;

2) sawtooth signal travels through one by one by the order increasing progressively in cycle span, until sawtooth signalCycle span in traveled through, sawtooth signal modulation result under different cycles is sampled, is locatedComposition result sequence after reason, 1/10th of the cycle span that traversal step-length is sawtooth signal;

3) the sawtooth signal cycle corresponding according to minimum of a value in result sequence, when calculating optical fibre gyro and getting overBetween first measurement result;

4) set the value model of cycle for the second time of sawtooth signal by first measurement result of optical fibre gyro transition timeEnclose repeating step 2), obtain measurement result sequence for the second time;

5) according to sawtooth signal cycle corresponding to minimum of a value in measurement result sequence for the second time, calculate optical fiberThe measurement result for the second time of gyro transition time, obtains the final optical fibre gyro transition time.

Described step 1) in the peak-to-peak value of sawtooth signal be fixed as integrated electro phase-modulator half-wave electricityPress 2 times.

Described step 2) in the cycle T of sawtooth signal_nSpan is 1.8 τ_Estimate≤T_n≤2.2τ_Estimate, itsMiddle n is traversal cycle sequence number, τ_EstimateFor optical fibre gyro transition time estimated value, by total fiber optic loop length and the light velocityBe divided by and calculate.

Described step 2) to sawtooth signal modulation result sampling under different cycles, the concrete steps bag processedDraw together: at 0～T_nIn/2 time, get cumulative first half periodic accumulation and the A of obtaining of 32 sampled points_n, at T_n/2～T_nTime in get that 32 sampled points are cumulative obtains later half cycle cumulative sum B_n, first half periodic accumulation and A_nWithLater half cycle cumulative sum B_nSubtract each other after taking absolute value and obtain result D_n＝|A_n–B_n|; Again by different cyclesT_nCorresponding demodulation result composition result sequence D={ D₁,D₂,D₃,…,D₁₁}。

Described step 3) specifically comprise: by the minimum of a value D of result sequence D_minCorresponding sawtooth signalCycle is T_min, first measurement result τ of optical fibre gyro transition time_Just＝T_min/2；

Described step 4) described cycle T for the second time_n' span is 1.98 τ_Just≤T_n’≤2.02τ_Just, whereinN is traversal cycle sequence number, τ_JustStep 3) the first measurement result of optical fibre gyro transition time that obtains.

Described step 5) specifically comprise: by measurement result sequence D for the second time ' minimum of a value D_min' correspondingThe sawtooth signal cycle is T_min', final optical fibre gyro transition time τ=T_min’/2。

The value of described traversal cycle sequence number n is n=0,1,2 ..., 11.

The beneficial effect that the present invention has is:

The present invention can Quick Measurement optical fibre gyro transition time, measuring process does not need additional devices or establishesStandby; According to measurement procedure, the measuring process used time is less than 5ms, and it is quick, high accuracy characteristic is enough to meet lightFine gyro through engineering approaches, batch production requirements.

Brief description of the drawings

Fig. 1 is optical fibre gyro system structural representation.

Fig. 2 is T_nOptical Fiber Gyroscope schematic diagram when=2 τ.

Fig. 3 is T_n> Optical Fiber Gyroscope schematic diagram when 2 τ.

Fig. 4 is T_nOptical Fiber Gyroscope schematic diagram when < 2 τ.

Fig. 5 is Optical Fiber Gyroscope peak-to-peak value and modulation sawtooth signal cycle T_nBe related to schematic diagram.

Fig. 6 is curve of first measurement result-signal period of optical fibre gyro transition time.

Fig. 7 is optical fibre gyro transition time measurement result-signal period curve for the second time.

Detailed description of the invention

Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.

The inventive method comprises the following steps:

1) adopt digital sawtooth signal to modulate electrooptic modulator, the peak-to-peak value of this sawtooth signalFixing;

2) sawtooth signal travels through one by one by the order increasing progressively in cycle span, until sawtooth signalCycle span in traveled through, sawtooth signal modulation result under different cycles is sampled, is locatedComposition result sequence after reason, 1/10th of the cycle span that traversal step-length is sawtooth signal;

3) the sawtooth signal cycle corresponding according to minimum of a value in result sequence, when calculating optical fibre gyro and getting overBetween first measurement result, as coarse value;

4) set the value model of cycle for the second time of sawtooth signal by first measurement result of optical fibre gyro transition timeEnclose repeating step 2), obtain measurement result sequence for the second time;

5) according to sawtooth signal cycle corresponding to minimum of a value in measurement result sequence for the second time, calculate optical fiberThe measurement result for the second time of gyro transition time, obtains the final optical fibre gyro transition time, as accuratelyValue.

Step 1) in the peak-to-peak value of sawtooth signal be fixed as 2 of integrated electro half-wave voltage of phase modulatorDoubly.

Step 2) in the cycle T of sawtooth signal_nSpan is 1.8 τ_Estimate≤T_n≤2.2τ_Estimate, wherein n isTraversal cycle sequence number, n=0,1,2 ..., 11, τ estimates for optical fibre gyro transition time estimated value, by total fiber optic loopLength and the light velocity are divided by and calculate.

Step 2) concrete steps of the sampling of sawtooth signal modulation result, processing under different cycles are comprised:0～T_nIn/2 time, get cumulative first half periodic accumulation and the A of obtaining of 32 sampled points_n, at T_n/2～T_nTimeIn get that 32 sampled points are cumulative obtains later half cycle cumulative sum B_n, first half periodic accumulation and A_nWith second halfPhase cumulative sum B_nSubtract each other after taking absolute value and obtain result D_n＝|A_n–B_n|; Again by different cycles T_nCorrespondingDemodulation result composition result sequence D={ D₁,D₂,D₃,…,D₁₁}。

Step 3) specifically comprise: by the minimum of a value D of result sequence D_minThe corresponding sawtooth signal cycle isT_min，D_min=min (D), first measurement result τ of optical fibre gyro transition time_Just＝T_min/2；

Step 4) described cycle T for the second time_n' span is 1.98 τ_Just≤T_n’≤2.02τ_Just, wherein n is timeGo through cycle sequence number, n=0,1,2 ..., 11, τ_JustStep 3) optical fibre gyro transition time of obtaining measures for the first timeResult.

Step 5) specifically comprise: by measurement result sequence D for the second time ' minimum of a value D_min' corresponding sawtooth waveformsSignal period is T_min’，D_min'=min (D '), final optical fibre gyro transition time τ=T_min’/2。

The inventive method can be to signal of fiber optical gyroscope place in optical fibre gyro system structure as shown in Figure 1Reason, samples to Optical Fiber Gyroscope by analog-digital converter, by FPGA, sampled result is carried outProcess and form result sequence.

Design principle of the present invention is:

If sawtooth signal modulation amplitude is ± pi/2 to be expressed as follows:

${\mathrm{\&phi;}}_m\left(t\right)=(2t/T_n-2k-1)\frac{\mathrm{\&pi;}}{2}k\&Element;Z$

Wherein, φ_m(t) be the phase modulation that electrooptic modulator is introduced, t is the time, T_nSawtooth period, kIt is sequence numbering modulation period. Suppose that the optical fibre gyro transition time is τ, according to time delay differential modulation principle,In fiber optic loop, propagate and the phase difference φ of the counterclockwise two-beam of propagating after electrooptic modulator along clockwise_m(t)For:

Δφ_m(t)＝φ_m(t)-φ_m(t-τ)

The output signal of optical fibre gyro is expressed as:

I(t)＝I₀{1+cos[Δφ_m(t)]}

Wherein, I₀Be optical fibre gyro input light intensity, I (t) is optical fibre gyro output interference light intensity.

Work as T_nWhen=2 τ, can be obtained fom the above equation:

${\mathrm{\&Delta;\&phi;}}_m\left(t\right)=\left\{\begin{array}{c}-\frac{\mathrm{\&pi;}}{2}......{\mathrm{kT}}_n<t\&le;{\mathrm{kT}}_n+\mathrm{\&tau;}\\ \frac{\mathrm{\&pi;}}{2}......{\mathrm{kT}}_n+\mathrm{\&tau;}<t\&le;(k+1)T_n\end{array}\right.k\&Element;Z$

Now, by (3) Shi Ke get: I (t)=I₀

Fig. 2 is T_nOptical Fiber Gyroscope schematic diagram when=2 τ, according to time delay differential modulation principle, two bundlesThe phase difference φ of backpropagation light_m(t) value is ± V_π/2, by interfering output intensity expression formula (3) to obtainOptical Fiber Gyroscope is normal value.

T_n> when 2 τ, by (1), (2) Shi Ke get:

${\mathrm{\&Delta;\&phi;}}_m\left(t\right)=\left\{\begin{array}{c}-\frac{\mathrm{\&pi;}}{2}(2-2\mathrm{\&tau;}/T_n)......{\mathrm{kT}}_n<t\&le;{\mathrm{kT}}_n+\mathrm{\&tau;}\\ \frac{\mathrm{\&pi;}}{2}(2\mathrm{\&tau;}/T_n)......{\mathrm{kT}}_n+\mathrm{\&tau;}<t\&le;(k+1)T_n\end{array}\right.k\&Element;Z$

Now, from (3) formula, interfere that output intensity shows as that dutycycle is less than 1, the cycle is T_n, allValue approximates I₀Square wave.

Fig. 3 is T_n> Optical Fiber Gyroscope schematic diagram when 2 τ, according to time delay differential principle, two beam reversalsPropagate the phase difference φ of light_m(t) average is constant, but dutycycle changes. Express by interfering output intensityThe output signal that formula can obtain optical fibre gyro shows as that dutycycle is less than 1, the cycle is T_n, average approximatesI₀Square wave. Electrooptic modulator is at ± V_π/2Better linear when near work, establish T_n=2.2 τ, can be calculated lightThe peak value of fine gyro output square-wave signal is 0.858I₀、1.142I₀。

T_nWhen < 2 τ, by (1), (2) Shi Ke get:

${\mathrm{\&Delta;\&phi;}}_m\left(t\right)=\left\{\begin{array}{c}-\frac{\mathrm{\&pi;}}{2}(2-2\mathrm{\&tau;}/T_n)......{\mathrm{kT}}_n<t\&le;{\mathrm{kT}}_n+\mathrm{\&tau;}\\ \frac{\mathrm{\&pi;}}{2}(2\mathrm{\&tau;}/T_n)......{\mathrm{kT}}_n+\mathrm{\&tau;}<t\&le;(k+1)T_n\end{array}\right.k\&Element;Z$

Now, from (3) formula, interfere that output intensity shows as that dutycycle is greater than 1, the cycle is T_n, allValue approximates I₀Square wave.

Fig. 4 is T_nOptical Fiber Gyroscope schematic diagram when < 2 τ, according to time delay differential principle, two beam reversalsPropagate the phase difference φ of light_m(t) average is constant, but dutycycle changes. Express by interfering output intensityThe output signal that formula can obtain optical fibre gyro shows as that dutycycle is greater than 1, the cycle is T_n, average approximatesI₀Square wave. Electrooptic modulator is at ± V_π/2Better linear when near work, establish T_n=1.8 τ, can be calculated lightThe peak value of fine gyro output square-wave signal is 0.826I₀、1.174I₀。

By above-mentioned a), b), c) derive, T_nNear 2 τ, get different values, Optical Fiber Gyroscope I (t) withVariation: T_n＝2τ，I(t)＝I₀For normal value; T_n≠ 2 τ, I (t) is that certain dutycycle, cycle are T_n, averageBe about I₀Square wave, square wave peak-to-peak value can approximate representation be:

$\mathrm{\&Delta;I}=|1-\frac{2\mathrm{\&tau;}}{T_n}|{\mathrm{\&pi;I}}_0$

Optical Fiber Gyroscope peak-to-peak value with modulation the sawtooth signal cycle relation curve as shown in Figure 5,T when can obtaining accordingly exporting square-wave signal peak-to-peak value minimum_n＝2τ。

According to above-mentioned principle, the Quick Measurement of fast optical fibre gyro transition time can adopt the inventive method.

Certainty of measurement of the present invention depends on measurement result D_nPrecision, D_nPrecision depends on dividing of analog-digital converterDistinguish rate and obtain A_n、B_nAccumulative frequency, as use 16 bit resolution analog-digital converters, the present invention measures essenceDegree can reach 1/2¹⁶⁺⁵, be about 2,000,000/.

Embodiments of the invention:

In the present embodiment, draw transition time estimated value τ according to fiber optic loop length and the light velocity_Estimate=6.782 microseconds.When step is carried out actual test according to the present invention, obtain first measurement result, draw measurement result-signal weekPhase curve, is shown in accompanying drawing 6; Obtain sawtooth signal cycle T corresponding to first measurement result sequence minimum of a value_min＝1.96τ_Estimate, calculate thus τ_Just＝T_min/2＝0.98τ_Estimate=6.646 microseconds. By the optical fibre gyro transition timeFirst measurement result is set after the cycle span for the second time of sawtooth signal, duplicate measurements step 2,Arrive measurement result for the second time, draw measurement result-signal period curve, see accompanying drawing 7; Surveyed for the second timeSawtooth signal cycle T corresponding to amount result sequence minimum of a value_min’＝1.996τ_Just, calculate thus τ=T_min’/2＝0.998τ_Just=6.632 microseconds.

In measuring process, calculate the required time of each sawtooth signal period Tn alignment processing result Dn approximatelyFor 2 times of the transition time, corresponding 22 different signal periods of whole testing process, the used time is about while getting overBetween 45 times; Common optical fiber gyro taking fiber optic loop length as 300m is example, and whole test process takesBetween be about 1ms, add FPGA data communication required time, the measuring process used time is less than 5ms. The present invention is logicalThe method of crossing twice traversal and changing traversal step-length has been saved the testing time. With single ergodic, step-length be the cycleOne of percentage of span is compared, and the time is reduced to approximately 45 times of transition time by approximately 200 times of transition time.

Above-mentioned detailed description of the invention is used for the present invention that explains, instead of limits the invention, at thisIn the spirit of invention and the protection domain of claim, any amendment and change that the present invention is made, all fallEnter protection scope of the present invention.

Claims (6)

1. the optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms, is characterized in that the step of the method is as follows:

1) adopt digital sawtooth signal to modulate electrooptic modulator, the peak-to-peak value of this sawtooth signal is fixed;

2) sawtooth signal travels through one by one by the order increasing progressively in cycle span, until traveled through in the cycle span of sawtooth signal, rear composition result sequence is sampled, processed to sawtooth signal modulation result under different cycles, 1/10th of the cycle span that traversal step-length is sawtooth signal;

3) in the sawtooth signal cycle corresponding according to minimum of a value in result sequence, calculate first measurement result of optical fibre gyro transition time;

By result sequenceDMinimum of a valueD _minThe corresponding sawtooth signal cycle isT _min, first measurement result τ of optical fibre gyro transition time_Just=T _min/2；

4) set the span of cycle for the second time of sawtooth signal by first measurement result of optical fibre gyro transition time, repeating step 2), obtain measurement result sequence for the second time;

5) according to sawtooth signal cycle corresponding to minimum of a value in measurement result sequence for the second time, calculate the measurement result for the second time of optical fibre gyro transition time, obtain the final optical fibre gyro transition time;

By measurement result sequence for the second timeD' minimum of a valueD _min' the corresponding sawtooth signal cycle isT _min', final optical fibre gyro transition time τ=T _min’/2。

2. a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms according to claim 1, is characterized in that: the peak-to-peak value of the sawtooth signal in described step 1) is fixed as 2 times of electrooptic modulator half-wave voltage.

3. a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms according to claim 1, is characterized in that: described step 2) in cycle of sawtooth signalT _n Span is 1.8 τ_Estimate≤T _n ≤2.2τ_Estimate, wherein n is traversal cycle sequence number, τ_EstimateFor optical fibre gyro transition time estimated value, be divided by and calculate by total fiber optic loop length and the light velocity.

4. a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms according to claim 3, is characterized in that: described step 2) sawtooth signal modulation result sampling under different cycles, the concrete steps processed are comprised: 0～T _n In/2 time, get 32 sampled points cumulative obtain first half periodic accumulation andA _n ,T _n /2～T _n Time in get that 32 sampled points are cumulative obtains later half cycle cumulative sumB _n , first half periodic accumulation andA _n With later half cycle cumulative sumB _n Subtract each other after taking absolute value and obtain resultD _n =|A _n –B _n |; Again by different cyclesT _n Corresponding demodulation result composition result sequenceD={D ₁,D ₂,D ₃,…,D ₁₁}。

5. a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms according to claim 1, is characterized in that: the cycle for the second time described in described step 4)T _n ' span is 1.98 τ_Just≤T _n ’≤2.02τ_Just, wherein n is traversal cycle sequence number, τ_JustIt is the first measurement result of optical fibre gyro transition time that step 3) obtains.

6. according to the arbitrary described a kind of optical fibre gyro transition time method for fast measuring based on digital sawtooth waveforms of claim 3 or 4, it is characterized in that: the value of described traversal cycle sequence number n isn=0,1,2,…,11。