CN102607547B - Digital domain balanced detecting method and device for optical fiber gyroscope - Google Patents

Abstract

The invention provides a digital domain balanced detecting method for an optical fiber gyroscope, which comprises the following steps of: applying a phase modulation signal to a phase modulator, wherein the phase modulation signal is obtained after a sinusoidal signal and a cosine signal which have the same modulation frequency are linearly combined; using the applied sinusoidal signal as an I-path reference signal and carrying out derivation on the I-path reference signal to obtain a Q-path reference signal; respectively carrying out coherent processing on a signal output by the optical fiber gyroscope and the I-path reference signal and the Q-path reference signal so as to obtain an I-path detection signal and a Q-path detection signal; respectively demodulating the I-path and Q-path detection signals to obtain an I-path angular velocity measured value and a Q-path angular velocity measured value; and according to a preset linear formula, combining the I-path and Q-path angular velocity measured values to obtain a measured value of an angular velocity to be measured, wherein the preset linear formula is predetermined according to the linear combination of the applied sinusoidal signal and cosine signal. Due to the utilization of the method, the bias stability of the optical fiber gyroscope can be improved.

Description

Numeric field balance detection method and the device of fibre optic gyroscope

Technical field

The present invention relates to communication technical field, more specifically, relate to a kind of numeric field balance detection method and device of fibre optic gyroscope.

Background technology

Gyroscope is a kind of rotation sensor, for measuring the rotational angular velocity of its place carrier.The fields such as gyroscope is widely used the guidance at various aircraft and weapon, industrial and military multiple precision measurement.Common gyroscope has three types: mechanical gyroscope, lasergyro, and fibre optic gyroscope (Fiber-optic gyroscope, FOG).Both are all optical gyroscope afterwards.The features such as optical gyroscope has compact conformation, sensitivity height, but degree of stability is not as good as some modern mechanical gyros.Due to the needs of application, novel gyroscope should have high sensitivity and degree of stability, lower cost and power consumption, and the feature such as volume is little.

The principle of optical gyroscope is based on Sagnac effect (Sagnac effect).In closed light path, the two-beam of (CW) along clockwise direction being sent by same light source and counterclockwise (CCW) transmission interferes, utilize the variation of the poor or interference fringe of detected phase, just can measure closed light path angular velocity of rotation.The common expression way of one of Sagnac effect is that the two-beam of clockwise direction (CW) and counterclockwise (CCW) transmission has produced the phase differential being directly proportional to angular velocity of rotation, this phase differential is known as Sagnac phase shift, and expression formula is as follows:

$\mathrm{\Δ\φ}=\frac{4\mathrm{\ωA}}{c^2}\mathrm{\Ω}$ Equation (1)

Wherein ω is light frequency, and c is the light velocity in vacuum, and A is the area that light path is enclosed, and Ω is rotational angular velocity.In interferometric fiber optic gyroscope, the longer optical fiber of normal employing turns to multiturn gyro coil.In this case, one of Sagnac effect uses more conveniently expression formula to be

$\mathrm{\Δ\φ}=2\mathrm{\π}\frac{\mathrm{LD}}{\mathrm{\λc}}\mathrm{\Ω}$ Equation (2)

The length that wherein L is optical fiber, D is fiber optic coils diameter, the wavelength that λ is light wave.

The foundation structure of fibre optic gyroscope is sagnac interferometer, and this structure need to meet the reciprocity conditions such as beam splitter reciprocity, single mode reciprocity, polarization reciprocity.Reciprocity has guaranteed that spread state and the path of CW light and CCW light is in full accord, has played the effect of " common mode inhibition ", the deviation causing to eliminate multiple ghost effect.Fig. 1 shows the minimum reciprocal structure of fibre optic gyroscope.The use of two coupling mechanisms is in order to guarantee that two-beam is identical through the cumulative phase shift of coupling mechanism, guarantees coupling mechanism heterogeneite.And having guaranteed two-beam, propagates at same polarization mode by the polarizer i.e. polarization reciprocity.

Adopting polarization maintaining optical fibre is the effective means of heterogeneite that guarantees optical fibre gyro structure, only by a kind of light of polarization mode for detection of slewing rate, and the polarized light that suppresses another direction is to realize reciprocity.But in engineering application, polarization maintaining optical fibre gyro still exists cost high, to bending responsive, to problems such as magnetic-field-sensitives.Thereby people have proposed again depolarized scheme, the optical fibre gyro structure that adopts depolarizer and single-mode fiber to build lower cost.

In order to make fibre optic gyroscope be operated in the higher state of sensitivity, phase-modulation (for example, PZT phase-modulator) need to be added in one end of fiber optic coils (, fiber optic loop), as shown in Figure 2.PZT phase-modulator makes two-beam ripple be subject to phase-modulation φ at different time _m(t), produce a phase differential, as follows

Δ φ (t)=φ _cCW(t)-φ _cW(t)=φ _m(t)-φ _m(t-τ) equation (3)

Wherein τ=n _effl/c represents that light is by the transmission time of whole fiber optic coils length, n _effit is the effective refractive index of optical fiber.Apply after modulation, interference light intensity signal is

I _d=I ₀{ 1+cos[φ _s+ Δ φ (t)] } equation (4)

In open loop interference type optical fiber gyroscope, conventionally adopt the modulation of single frequency sinusoidal ripple

φ _m(t)=φ ₀sin (ω _mt) equation (5)

Now

$\mathrm{\Δ\φ}\left(t\right)=2{\mathrm{\φ}}_0\sin \left(\frac{{\mathrm{\ω}}_m\mathrm{\τ}}{2}\right)\cos \left[{\mathrm{\ω}}_m(t-\mathrm{\τ}/2)\right]$ Equation (6)

The spectrum component of interference light intensity signal

I _d=I ₀{ 1+[J ₀(φ _b)+2 ∑s (1) ⁿj _2n(φ _m) cos 2n ω _m(t-τ/2)] cos (φ _s) equation (7)

-2∑(-1) ⁿ⁺¹J _2n-1(φ _b)cos[(2n-1)ω _m(t-τ/2)]sin(φ _S)}

Wherein

φ _b=2 φ ₀sin (ω _mτ/2) equation (8)

Separating timing, first utilize 2 order harmonic components of modulating frequency and the amplitude of 4 order harmonic components to obtain φ _b, solve an equation

I (4 ω _m)/I (2 ω _m)=J ₄(φ _b)/J ₂(φ _b) equation (9)

Then, utilize 1 subharmonic of modulating frequency and 2 order harmonic components amplitudes to try to achieve Sagnac phase shift φ _s

φ _s=arctan{I (ω _m) J ₂(φ _b)/I (2 ω _m) J ₁(φ _b) equation (10)

Further obtain rotational angular velocity Ω according to equation (2).It is more than the open loop interference type optical fiber gyroscope principle of traditional unifrequency Sine Modulated.

Interference type optical fiber gyroscope need to have been divided different precision grades according to its application, the technical requirement that following table is each precision grade.Wherein zero bias stability is to weigh the most important technical indicator of interference type optical fiber gyroscope precision, and improving this index is to realize the necessary condition of accurate inertial guidance.

The precision grade of table 1 interference type optical fiber gyroscope and technical requirement

Wherein, zero bias stability is to weigh the most important technical indicator of interference type optical fiber gyroscope precision, and improving this index is to realize the necessary condition of accurate inertial guidance.

But, in existing method for measuring angular velocity, the drift that existing faraday's magnetic field effect, temperature fluctuation cause or other low-frequency noises, and polarization in optical fibre gyro develops and the flicker noise of detector, will cause the i.e. zero bias stability reduction of fluctuation of data zero offset.Need new measuring method, suppress zero partially unsettled inducement, or noise is carried out to the elimination in later stage.

Summary of the invention

In view of above-mentioned, the invention provides a kind of numeric field balance detection method and device of fibre optic gyroscope, the method and device can improve zero bias stability of optical fibre gyro.

According to an aspect of the present invention, a kind of numeric field balance detection method of fibre optic gyroscope is provided, wherein said fibre optic gyroscope comprises phase-modulator, and described method comprises: be applied with by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the phase modulated signal obtaining after linear combination to described phase-modulator; Applied sinusoidal signal is used as to I road reference signal, and I road reference signal is carried out to differentiate, obtain Q road reference signal; By the signal of optical fibre gyro output respectively with the processing that be concerned with of described I road reference signal, Q road reference signal, acquisition I road detection signal, Q road detection signal; To obtained I road, the demodulation respectively of Q road detection signal, obtain I road angular velocity measurement value, Q road angular velocity measurement value; According to predetermined linear formula, obtained I, Q two-way angular velocity measurement value are combined to the measured value that obtains angular velocity to be measured, wherein, described predetermined linear formula pre-determines according to the linear combination of applied sinusoidal signal and cosine signal.

In one or more examples aspect above-mentioned, described fibre optic gyroscope utilizes wide spectrum light source to be connected realization by polarization maintaining optical fibre successively with optical fiber circulator, the polarizer, y-shaped waveguide phase-modulator, polarization-maintaining fiber coil.

In one or more examples aspect above-mentioned, described fibre optic gyroscope utilizes wide spectrum light source to be connected by polarization maintaining optical fibre successively with 3dB fiber coupler, the polarizer, 3dB polarization-maintaining coupler, two Loyt depolarizers, and is connected realization with PZT phase-modulator, single-mode fiber ring thereafter by single-mode fiber.

In one or more examples aspect above-mentioned, the assertive evidence frequency that described modulating frequency is described fibre optic gyroscope.

In one or more examples aspect above-mentioned, the linear combination signal of the sinusoidal signal applying on described phase-modulator and cosine signal is V ₀[sin (ω _mt)-cos (ω _m] or V t) ₀[sin (ω _mt)+cos (ω _mt)], described predetermined linear formula is (angular velocity measurement value-I road, Q road angular velocity measurement value)/2 or (angular velocity measurement value+I road, Q road angular velocity measurement value)/2, wherein V ₀the amplitude of applied signal, and ω _mit is the eigenfrequency of fibre optic gyroscope.

In one or more examples aspect above-mentioned, described relevant processing comprise by the first harmonic in the output signal of fibre optic gyroscope respectively with the line amplitude convergent-divergent processing of going forward side by side of multiplying each other of I road reference signal and Q road reference signal, then convergent-divergent signal after treatment is carried out to low-pass filtering.

According to a further aspect in the invention, provide a kind of for fibre optic gyroscope being carried out to the sniffer of numeric field balance detection, wherein said fibre optic gyroscope comprises phase-modulator, described sniffer comprises: modulation signal applying unit, for being applied with on described phase-modulator by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the phase modulated signal obtaining after linear combination; I road reference signal acquiring unit, for being used as I road reference signal by applied sinusoidal signal; Q road reference signal acquiring unit, for I road reference signal is carried out to differentiate, obtains Q road reference signal; Relevant processing unit, for by the signal of optical fibre gyro output respectively with the processing that be concerned with of described I road reference signal, Q road reference signal, acquisition I road detection signal, Q road detection signal; Demodulating unit, for the I road to obtained, the demodulation respectively of Q road detection signal, obtains I road angular velocity measurement value, Q road angular velocity measurement value; Linear combination unit, be used for according to predetermined linear formula, obtained I, Q two-way angular velocity measurement value are combined to the measured value that obtains angular velocity to be measured, and wherein, described predetermined linear formula pre-determines according to the linear combination of applied sinusoidal signal and cosine signal.

In one or more examples aspect above-mentioned, described fibre optic gyroscope utilizes wide spectrum light source to be connected realization by polarization maintaining optical fibre successively with optical fiber circulator, the polarizer, y-shaped waveguide phase-modulator, polarization-maintaining fiber coil.

In one or more examples aspect above-mentioned, described fibre optic gyroscope utilizes wide spectrum light source to be connected by polarization maintaining optical fibre successively with 3dB fiber coupler, the polarizer, 3dB polarization-maintaining coupler, two Loyt depolarizers, and is connected realization with PZT phase-modulator, single-mode fiber ring thereafter by single-mode fiber.

In one or more examples aspect above-mentioned, the linear combination signal of the sinusoidal signal applying on described phase-modulator and cosine signal is V ₀[sin (ω _mt)-cos (ω _m] or V t) ₀[sin (ω _mt)+cos (ω _mt)], described predetermined linear formula is (angular velocity measurement value-I road, Q road angular velocity measurement value)/2 or (angular velocity measurement value+I road, Q road angular velocity measurement value)/2, wherein V ₀the amplitude of applied signal, and ω _mit is the eigenfrequency of fibre optic gyroscope.

In order to realize above-mentioned and relevant object, one or more aspects of the present invention comprise below by the feature that describes in detail and particularly point out in the claims.Explanation below and accompanying drawing describe some illustrative aspects of the present invention in detail.But, the indication of these aspects be only some modes that can use in the variety of way of principle of the present invention.In addition, the present invention is intended to comprise all these aspects and their equivalent.

Beneficial effect

Utilize said method and device, by the phase-modulator of fibre optic gyroscope is applied to the linear combination of sinusoidal signal and cosine signal as the input signal of optical fibre gyro, and the signal that the sinusoidal signal that utilization applies carries out as I road reference signal and to I road reference signal obtaining after differentiate is as Q road reference signal, respectively the output signal of fibre optic gyroscope is carried out to I road and Q road relevant, then utilize predetermined linear combination to combine to obtain angular velocity measurement value to the relevant output signal in the I road after demodulation and Q road.In the manner described above, can eliminate the common-mode noise component in I, Q two-way, thereby improve zero bias stability of fibre optic gyroscope.

Accompanying drawing explanation

By reference to the content below in conjunction with the description of the drawings and claims, and along with understanding more comprehensively of the present invention, other object of the present invention and result will be understood and easy to understand more.In the accompanying drawings:

Fig. 1 is the diagram of the minimum reciprocal structure of optical fibre gyro;

Fig. 2 is the phase-modulation diagram of optical fibre gyro;

Fig. 3 is principle diagram of the present invention;

Fig. 4 shows the process flow diagram of the numeric field equivalent detection method of fibre optic gyroscope according to an embodiment of the invention;

Fig. 5 is according to the structural representation of the numeric field balance detection method of the optical fibre gyro of first embodiment of the invention;

Fig. 6 is according to the structural representation of the numeric field balance detection method of the optical fibre gyro of second embodiment of the invention;

Fig. 7 is the gyroscope output data time-domain diagram in the embodiment of Fig. 5;

Fig. 8 is I in the embodiment of Fig. 5, the scatter diagram of Q two-way detected value on two dimensional surface;

Fig. 9 is the Allan analysis of variance diagram of the gyroscope output data in the embodiment of Fig. 5;

Figure 10 shows according to of the present invention for optical fibre gyro being carried out to the block diagram of the sniffer of numeric field balance detection.

In institute's drawings attached, identical label is indicated similar or corresponding feature or function.

Embodiment

In the following description, for purposes of illustration, for the complete understanding to one or more embodiment is provided, many details have been set forth.But, clearly, also can in the situation that there is no these details, realize these embodiment.In other example, one or more embodiment for convenience of description, known structure and equipment illustrate with the form of block scheme.

Come below with reference to accompanying drawings each embodiment according to the present invention to be described in detail.

Fig. 3 shows square ratio juris diagram in the present invention.As shown in Figure 3, adopt the signal of I, the orthogonal form of Q two-way to carry out phase-modulation to fibre optic gyroscope, that is, the input using the linear combination of I, Q two-way orthogonal signal as fibre optic gyroscope, is input on the phase-modulator of fibre optic gyroscope.And in the time measuring, the detection signal that photodetector is detected is concerned with to process and obtains respectively I, Q two-way detection signal, thereby realize the balance detection of the numeric field of optical fibre gyro.

Fig. 4 shows the process flow diagram of the numeric field equivalent detection method of fibre optic gyroscope according to an embodiment of the invention.

As shown in Figure 4, first, at step S410, the phase-modulator of fibre optic gyroscope is applied with by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the signal obtaining after linear combination.Then, detecting via photodetector after the output signal of fibre optic gyroscope, at step S420, applied sinusoidal signal is used as to I road reference signal, and I road reference signal is carried out after differentiate, obtain Q road reference signal.Here the eigenfrequency that, described modulating frequency is fibre optic gyroscope.Then, at step S430, by the output signal of fibre optic gyroscope respectively with the processing that is concerned with of I road reference signal and Q road reference signal, obtain I road detection signal and Q road detection signal.Here, relevant processing refers to multiplies each other the first harmonic of output signal respectively with two-way reference signal, and convergent-divergent amplitude (for example, carrying out amplitude normalization), then carries out low-pass filtering.

Then, at step S440, obtained I road detection signal and Q road detection signal are carried out to demodulation, obtain I road angular velocity measurement value and Q road angular velocity measurement value.

Obtaining after above-mentioned I road angular velocity measurement value and Q road angular velocity measurement value, at step S450, according to predetermined linear formula, obtained I road, Q road angular velocity measurement value are combined to the measured value that obtains angular velocity to be measured, wherein, described predetermined linear formula is determined according to the linear combination cosine of applied sinusoidal signal and cosine signal.For example, preferably, the linear combination signal of the sinusoidal signal applying on described phase-modulator and cosine signal is V ₀[sin (ω _mt)-cos (ω _m] or V t) ₀[sin (ω _mt)+cos (ω _mt)], V wherein ₀the amplitude of applied signal, and ω _mit is the eigenfrequency of fibre optic gyroscope.Correspondingly, to be confirmed as be (angular velocity measurement value-I road, Q road angular velocity measurement value)/2 or (angular velocity measurement value+I road, Q road angular velocity measurement value)/2 to described predetermined linear formula.In addition,, in other example, linear combination signal also can adopt other linear combination form, and predetermined linear formula also can correspondingly change.

Fig. 5 shows according to the structural representation of the numeric field balance detection method of the fibre optic gyroscope of first embodiment of the invention.As shown in Figure 5, fibre optic gyroscope is formed by connecting by polarization maintaining optical fibre successively by wide spectrum light source and optical fiber circulator, the polarizer, y-shaped waveguide phase-modulator, polarization-maintaining fiber coil, is a kind of typical inclined to one side interference type optical fiber gyroscope structure of protecting.

In the present embodiment, wherein wide spectrum light source is ASE light source or SLED light source, and polarization-maintaining fiber coil is long is 1.98km, applies with sine, cosine signal subtract each other the orthogonal demodulation signal obtaining frequently on phase-modulator.Modulating frequency is the eigenfrequency 52.35KHz (, the eigenfrequency of fibre optic gyroscope) of described polarization-maintaining fiber coil.Wherein, wherein sinusoidal signal as separating the I road reference signal of timing.

The function of Usage data collection card and computer realization digital processing in this example: receive photodetector and detect output from Gyroscope, I road reference signal is carried out to differentiate and obtain the Q road reference signal orthogonal with it; Photodetector is detected to the first harmonic in Optical Fiber Gyroscope is concerned with I road reference signal, Q road reference signal respectively, obtains I road detection signal, Q road detection signal; To obtained I, the demodulation respectively of Q two-way detection signal, obtain I road angular velocity measurement value, Q road angular velocity measurement value that symbol is contrary; I, Q two-way angular velocity measurement value are subtracted each other after 2 and obtained angular velocity output valve.

Compared with the angular velocity that gained angular velocity output valve obtains with traditional detection method, zero bias stability improves several times to order of magnitude.

Fig. 6 shows according to the structural representation of the numeric field balance detection method of the optical fibre gyro of second embodiment of the invention.As shown in Figure 6, wide spectrum light source is connected by polarization maintaining optical fibre successively with 3dB fiber coupler, the polarizer, 3dB polarization-maintaining coupler, two Loyt depolarizers, and be connected by single-mode fiber with PZT phase-modulator, single-mode fiber ring thereafter, be a kind of typical depolarized interference type optical fiber gyroscope structure.Its input is identical with the first example with digital processing method.

Below the numeric field balance detection process of above-described embodiment is made a concrete analysis of.

In the present invention, the eigenfrequency ω of fibre optic gyroscope _m=π/τ, is learnt by equation (7), and under eigenfrequency modulation, the first harmonic of gyrostatic output signal is

$I\left({\mathrm{\ω}}_m\right)=-2I_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\cos ({\mathrm{\ω}}_{m}t-\frac{\mathrm{\π}}{2})$ Equation (11)

$=2I_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\sin ({\mathrm{\ω}}_{m}t+\mathrm{\π})$

The conversion coefficient that wherein η is photodetector.The phase differential of first harmonic and sinusoidal modulation signal is π, 180 °.In the present embodiment, modulation signal is

${\mathrm{\φ}}_m\left(t\right)={\mathrm{\φ}}_0[\sin \left({\mathrm{\ω}}_{m}t\right)-\cos \left({\mathrm{\ω}}_{m}t\right)]=\sqrt{2}{\mathrm{\φ}}_0\sin ({\mathrm{\ω}}_{m}t-\frac{\mathrm{\π}}{4})$ Equation (12)

Now the first harmonic of gyrostatic output signal is

$I\left({\mathrm{\ω}}_m\right)=2I_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\sin ({\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})$ Equation (13)

Wherein ${\mathrm{\φ}}_b=2\sqrt{2}{\mathrm{\φ}}_0\sin ({\mathrm{\ω}}_m\mathrm{\τ}/2),$ And I road reference signal is

V _i(t)=V _fsin (ω _mt) equation (14)

Differentiate divided by ω _mafter (carrying out unified to amplitude), obtain Q road reference signal

V _q(t)=V _fcos (ω _mt) equation (15)

First harmonic is 3 π/4 with respect to the phase place of I road reference signal, 135 °.By relevant to first harmonic and reference signal, can obtain respectively I, the first harmonic amplitude of Q two paths of signals.Relevant process realizes at numeric field, first first harmonic multiplied each other with two-way reference signal respectively, and convergent-divergent amplitude, and the process expression that establishes an equation as follows

$\frac{\sqrt{2}}{V_f}I\left({\mathrm{\ω}}_m\right)V_I\left(t\right)=2\sqrt{2}{I}_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\sin ({\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})\sin \left({\mathrm{\ω}}_{m}t\right)$

$=\sqrt{2}{I}_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)(-\cos (2{\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})+\cos \left(\frac{3\mathrm{\π}}{4}\right))$

$=-\sqrt{2}{I}_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\cos (2{\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})-2I_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)$ Equation (16)

$\frac{\sqrt{2}}{V_f}I\left({\mathrm{\ω}}_m\right)V_Q\left(t\right)=2\sqrt{2}{I}_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\sin ({\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})\cos \left({\mathrm{\ω}}_{m}t\right)$

$=\sqrt{2}{I}_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)(\sin (2{\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})+\sin \left(\frac{3\mathrm{\π}}{4}\right))$

$=\sqrt{2}{I}_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)\sin (2{\mathrm{\ω}}_{m}t+\frac{3\mathrm{\π}}{4})+2I_0\mathrm{\η}{J}_1\left({\mathrm{\φ}}_b\right)\sin \left({\mathrm{\φ}}_S\right)$ Equation (17)

Result is carried out to low-pass filtering, obtain result as follows

I _i(ω _mthe 2I of)=- ₀η J ₁(φ _b) sin (φ _s) equation (18)

I _q(ω _m)=2I ₀η J ₁(φ _b) sin (φ _s) equation (19)

Be similar to traditional single-frequency modulation optical fibre gyro, detect amplitude I (2 ω of 2 order harmonic components of modulating frequency _m) and 4 order harmonic components I (4 ω _m) amplitude after, utilize equation (9) can solve φ _b.

Then, use the quadrature detection result of two first harmonics of equation (18), equation (19) to replace the first harmonic in equation (10), obtain I, the phase differential that Q two-way detects

φ _i=arctan{I _i(ω _m) J ₂(φ _b)/I (2 ω _m) J ₁(φ _b)=-φ _sequation (20)

φ _q=arctan{I _q(ω _m) J ₂(φ _b)/I (2 ω _m) J ₁(φ _b)=φ _sequation (21)

Finally, the phase differential substitution equation (2) detecting is obtained to I, the detection magnitude of angular velocity of Q two-way

${\mathrm{\Ω}}_I=\frac{\mathrm{\λc}}{2\mathrm{\πLD}}{\mathrm{\φ}}_I=-\frac{\mathrm{\λc}}{2\mathrm{\πLD}}{\mathrm{\φ}}_S=-{\mathrm{\Ω}}_0$ Equation (22)

${\mathrm{\Ω}}_Q=\frac{\mathrm{\λc}}{2\mathrm{\πLD}}{\mathrm{\φ}}_Q=\frac{\mathrm{\λc}}{2\mathrm{\πLD}}{\mathrm{\φ}}_S={\mathrm{\Ω}}_0$ Equation (23)

Due to reasons such as experimental situations, the angular velocity that detects can comprise the error that noise brings, thereby departs to a certain extent the true value Ω of angular velocity to be measured ₀.Each detection angular velocimeter is shown to two, and wherein Section 1 embodies true value Ω ₀, Section 2 represents the noise of introducing in testing process.

Ω _i=-Ω ₀+ N _qequation (24)

Ω _q=Ω ₀+ N _iequation (25)

Two-way detected value is carried out to linear operation, obtain the gyro output angle velocity amplitude of numeric field equivalent detection method

$\mathrm{\Ω}=\frac{{\mathrm{\Ω}}_Q-{\mathrm{\Ω}}_I}{2}={\mathrm{\Ω}}_0+\frac{N_Q-N_I}{2}$ Equation (26)

Noise contribution complexity in the angular velocity that fibre optic gyroscope detects, comprises quantum noise, angle random walk, zero bias stability, speed random walk, rate ramp etc., and wherein zero bias stability is to weigh the most important index of fiber optic gyroscope performance.Described index can obtain by gyro output is carried out to Allan variance analysis.The method providing in above-described embodiment is provided, and is V at modulation signal ₀[sin (w _mt)-cos (w _mt) under situation], according to equation (26), I, the noise of Q two-way is to do poor form, and wherein identical composition (common-mode noise) is eliminated, and can eliminate thus I, common-mode noise composition in Q two-way, the indexs such as zero bias stability of raising gyro.

Fig. 7 shows the time domain comparison diagram of the gyroscope Output speed value in Fig. 5, comprising classic method demodulation result, numeric field balance detection result, I road result, Q road result.In figure, transverse axis is that measurement data is counted, and the longitudinal axis is the magnitude of angular velocity measuring, unit for degree/hour.Experiment measuring to as if rotational-angular velocity of the earth, on the surface level of laboratory dimension (north latitude 40.0 is spent), theoretical value to be measured be 9.67 degree/hour.Data output gap is about 0.15 second, test duration length 50 minutes.

Fig. 8 shows the I in Fig. 5, the scatter diagram of Q two-way detected value on two dimensional surface, and wherein transverse axis is I road detected value, and the longitudinal axis is Q road detected value.As seen from the figure, center of distribution is on 135 ° of lines of coordinate plane.

Fig. 9 shows the Allan analysis of variance diagram of the angular velocity time domain data in Fig. 5, comprising classic method demodulation result and numeric field balance detection result.As we know from the figure, zero bias stability of classic method demodulation result is

numeric field balance detection result zero bias stability is

that is to say, compared with classic method, zero bias stability of the embodiment shown in Fig. 5 has improved a magnitude.

To Fig. 9, the numeric field equivalent detection method of fibre optic gyroscope is according to an embodiment of the invention described above with reference to Fig. 3.The numeric field equivalent detection method of above-mentioned fibre optic gyroscope of the present invention, can adopt software to realize, and also can adopt hardware to realize, or adopts software and hardware array mode to realize.

Figure 10 shows according to an embodiment of the invention for optical fibre gyro being carried out to the block diagram of the sniffer 1000 of numeric field balance detection.Described sniffer 1000 is for carrying out numeric field balance detection to fibre optic gyroscope, wherein said fibre optic gyroscope comprises phase-modulator, and on described phase-modulator, is applied with by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the phase modulated signal obtaining after linear combination.Here, modulating frequency is preferably the eigenfrequency of fibre optic gyroscope.

As shown in figure 10, sniffer 1000 according to the present invention comprises modulation signal applying unit 1010, I road reference signal acquiring unit 1020, Q road reference signal acquiring unit 1030, relevant processing unit 1040, demodulating unit 1050 and linear combination unit 1060.

Modulation signal applying unit 1010 is for being applied with to described phase-modulator by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the phase modulated signal obtaining after linear combination.I road reference signal acquiring unit 1020, for obtaining after the output signal of fibre optic gyroscope, is used as I road reference signal by applied sinusoidal signal.Q road reference signal acquiring unit 1030, for I road reference signal is carried out to differentiate, obtains Q road reference signal.

Relevant processing unit 1040 for by the signal of fibre optic gyroscope output respectively with the processing that be concerned with of described I road reference signal, Q road reference signal, acquisition I road detection signal, Q road detection signal.Here, relevant processing refers to multiplies each other the first harmonic of output signal respectively with two-way reference signal, and convergent-divergent amplitude (for example, carrying out amplitude normalization), then carries out low-pass filtering.

Demodulating unit 1050, for the I road to obtained, the demodulation respectively of Q road detection signal, obtains I road angular velocity measurement value, Q road angular velocity measurement value.Then, linear combination unit 1060 is according to predetermined linear formula, obtained I, Q two-way angular velocity measurement value are combined to the measured value that obtains angular velocity to be measured, and wherein, described predetermined linear formula pre-determines according to the linear combination of applied sinusoidal signal and cosine signal.For example, preferably, the linear combination signal of the sinusoidal signal applying on described phase-modulator and cosine signal is V ₀[sin (ω _mt)-cos (ω _m] or V t) ₀[sin (ω _mt)+cos (ω _mt)], V wherein ₀the amplitude of applied signal, and ω _mit is the eigenfrequency of fibre optic gyroscope.Correspondingly, to be confirmed as be (angular velocity measurement value-I road, Q road angular velocity measurement value)/2 or (angular velocity measurement value+I road, Q road angular velocity measurement value)/2 to described predetermined linear formula.In addition,, in other example, linear combination signal also can adopt other linear combination form, and predetermined linear formula also can correspondingly change.

In addition, described fibre optic gyroscope can utilize wide spectrum light source to be connected realization by polarization maintaining optical fibre successively with optical fiber circulator, the polarizer, y-shaped waveguide phase-modulator, polarization-maintaining fiber coil.Or, described fibre optic gyroscope also can utilize wide spectrum light source to be connected by polarization maintaining optical fibre successively with 3dB fiber coupler, the polarizer, 3dB polarization-maintaining coupler, two Loyt depolarizers, and is connected realization with PZT phase-modulator, single-mode fiber ring thereafter by single-mode fiber.

Although disclosed content shows exemplary embodiment of the present invention above, it should be noted that under the prerequisite of scope of the present invention that does not deviate from claim restriction, can carry out multiple change and modification.Need not carry out with any particular order according to the function of the claim to a method of inventive embodiments described herein, step and/or action.In addition, although element of the present invention can be with individual formal description or requirement, also it is contemplated that multiple, unless be clearly restricted to odd number.

Although disclose the present invention in conjunction with the preferred embodiment that is shown specifically and describes, but those skilled in the art are to be understood that, propose for the invention described above for optical fibre gyro being carried out to method and the device of numeric field balance detection, can also on the basis that does not depart from content of the present invention, make various improvement.Therefore, protection scope of the present invention should be determined by the content of appending claims.

Claims (8)

1. a numeric field balance detection method for fibre optic gyroscope, wherein said fibre optic gyroscope comprises phase-modulator, described method comprises:

Apply by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the phase modulated signal obtaining after linear combination to described phase-modulator;

Applied sinusoidal signal is used as to I road reference signal, and I road reference signal is carried out to differentiate, obtain Q road reference signal;

By the signal of fibre optic gyroscope output respectively with the processing that be concerned with of described I road reference signal, Q road reference signal, acquisition I road detection signal, Q road detection signal;

To obtained I, the demodulation respectively of Q two-way detection signal, obtain I road angular velocity measurement value, Q road angular velocity measurement value;

According to predetermined linear formula, obtained I road, Q road angular velocity measurement value are combined to the measured value that obtains angular velocity to be measured,

Wherein, described predetermined linear formula pre-determines according to the linear combination of applied sinusoidal signal and cosine signal,

The linear combination signal of the sinusoidal signal applying on described phase-modulator and cosine signal is V ₀[sin (ω _mt)-cos (ω _m] or V t) ₀[sin (ω _mt)+cos (ω _mt)], described predetermined linear formula is (angular velocity measurement value-I road, Q road angular velocity measurement value)/2 or (angular velocity measurement value+I road, Q road angular velocity measurement value)/2, wherein V ₀the amplitude of applied signal, and ω _mit is the eigenfrequency of fibre optic gyroscope.

2. the method for claim 1, wherein described fibre optic gyroscope utilizes wide spectrum light source to be connected realization by polarization maintaining optical fibre successively with optical fiber circulator, the polarizer, y-shaped waveguide phase-modulator, polarization-maintaining fiber coil.

3. the method for claim 1, wherein, described fibre optic gyroscope utilizes wide spectrum light source to be connected by polarization maintaining optical fibre successively with 3dB fiber coupler, the polarizer, 3dB polarization-maintaining coupler, two Loyt depolarizers, and is connected realization with PZT phase-modulator, single-mode fiber ring thereafter by single-mode fiber.

4. the eigenfrequency that the method for claim 1, wherein described modulating frequency is described optical fibre gyro.

5. the method for claim 1, wherein, described relevant processing comprise by the first harmonic in the output signal of fibre optic gyroscope respectively with the line amplitude convergent-divergent processing of going forward side by side of multiplying each other of I road reference signal and Q road reference signal, then convergent-divergent signal after treatment is carried out to low-pass filtering.

6. for fibre optic gyroscope being carried out to a sniffer for numeric field balance detection, wherein said fibre optic gyroscope comprises phase-modulator, and described sniffer comprises:

Modulation signal applying unit, for being applied with to described phase-modulator by the sinusoidal signal with identical modulating frequency and cosine signal are carried out to the phase modulated signal obtaining after linear combination;

I road reference signal acquiring unit, for being used as I road reference signal by applied sinusoidal signal;

Q road reference signal acquiring unit, for I road reference signal is carried out to differentiate, obtains Q road reference signal;

Relevant processing unit, for by the signal of fibre optic gyroscope output respectively with the processing that be concerned with of described I road reference signal, Q road reference signal, acquisition I road detection signal, Q road detection signal;

Demodulating unit, for the I road to obtained, the demodulation respectively of Q road detection signal, obtains I road angular velocity measurement value, Q road angular velocity measurement value;

Linear combination unit, for the linear formula according to predetermined, combines to obtained I, Q two-way angular velocity measurement value the measured value that obtains angular velocity to be measured,

Wherein, described predetermined linear formula pre-determines according to the linear combination of applied sinusoidal signal and cosine signal,

The linear combination signal of the sinusoidal signal applying on described phase-modulator and cosine signal is V ₀[sin (ω _mt)-cos (ω _m] or V t) ₀[sin (ω _mt)+cos (ω _mt)], described predetermined linear formula is (angular velocity measurement value-I road, Q road angular velocity measurement value)/2 or (angular velocity measurement value+I road, Q road angular velocity measurement value)/2, wherein V ₀the amplitude of applied signal, and ω _mit is the eigenfrequency of fibre optic gyroscope.

7. sniffer as claimed in claim 6, wherein, described fibre optic gyroscope utilizes wide spectrum light source to be connected realization by polarization maintaining optical fibre successively with optical fiber circulator, the polarizer, y-shaped waveguide phase-modulator, polarization-maintaining fiber coil.

8. sniffer as claimed in claim 6, wherein, described fibre optic gyroscope utilizes wide spectrum light source to be connected by polarization maintaining optical fibre successively with 3dB fiber coupler, the polarizer, 3dB polarization-maintaining coupler, two Loyt depolarizers, and is connected realization with PZT phase-modulator, single-mode fiber ring thereafter by single-mode fiber.

Images