Closed-loop fiber-optic gyroscope system modeling method

Abstract

The invention belongs to a fiber-optic gyroscope modeling method, and particularly relates to a closed-loop fiber-optic gyroscope system modeling method. A light path, a circuit and a closed-loop control loop of the closed-loop fiber-optic gyroscope are modeled in sequence to form a system model of the closed-loop fiber-optic gyroscope, and the system model can be used for simulating modulation, pre-amplification, sampling, demodulation, step wave generation, 2 pi reset and other modules of the fiber-optic gyroscope. Actual parameters of all the modules are substituted into the model for simulation calculation, the signal transmission condition in the closed-loop fiber-optic gyroscope can be visually observed, the influence of all the modules on the output performance of the fiber-optic gyroscope is analyzed, theoretical support is provided for parameter design of the fiber-optic gyroscope, and the debugging efficiency of the fiber-optic gyroscope is improved.

Description

Technical Field

[0001] The invention belongs to a fiber optic gyroscope modeling method, and in particular relates to a closed-loop fiber optic gyroscope system modeling method. Background Art

[0002] Fiber optic gyroscope is an angular rate sensor designed based on the Sagnac effect. Due to its flexible design, no moving parts, and long life, it has received great attention since it was proposed. It has been widely used in flight control systems and inertial navigation systems. With the expansion of application fields, different systems have different performance requirements for fiber optic gyroscopes, which requires parameter design and debugging of fiber optic gyroscopes according to the requirements.

[0003] At present, the parameter design and debugging of fiber optic gyroscope mainly rely on the experience of designers and repeated debugging at the production site, which greatly reduces the production efficiency of gyroscope. Therefore, constructing a theoretical model of fiber optic gyroscope can more conveniently study the influence of various device parameters, modulation coefficients, etc. on the performance of fiber optic gyroscope, and improve the efficiency of design and debugging. In recent years, the modeling of closed-loop fiber optic gyroscope mainly starts from control theory, and reasonably simplifies nonlinear factors such as the cosine function relationship of the light wave interference output in the fiber optic gyroscope and the quantization error of A / D conversion, so that the nonlinear transfer function in the system is equivalent to a linear transfer function, thereby simplifying the nonlinear model to a linear model. This model is used to simulate and calculate the response of the system under different angular rate input conditions. The calculation results can reflect the performance of the fiber optic gyroscope such as bandwidth and phase lag. However, the fiber optic gyroscope control model can only reflect the change law of some signals, and cannot fully reflect the change law of the input and output signals in each module of the closed-loop fiber optic gyroscope, nor can it reflect the influence of 2π reset error, Y waveguide half-wave voltage error, etc. on the output of the fiber optic gyroscope.

[0004] Therefore, we urgently need a new model that can accurately reflect the signal changes of each module in the closed-loop fiber optic gyroscope. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a closed-loop fiber optic gyroscope system modeling method, which realizes parameter design and debugging of the fiber optic gyroscope by modeling each module.

[0006] The present invention includes the following technical solutions:

[0007] A closed-loop fiber optic gyroscope system modeling method, characterized in that it includes the following steps:

[0008] Step 1: Use the Step submodule to simulate the input angular rate of the fiber optic gyroscope

[0009] Step 2: Use the MATLAB Function submodule to simulate the optical path module and convert the angular velocity output in step 1 Input optical path module, output interference light intensity I;

[0010] Step 3: Use the Gain submodule to simulate the photoelectric conversion module of the detector, input the interference light intensity I output in step 2 into the photoelectric conversion module, and output the signal V T ;

[0011] Step 4: Use the Gain submodule to simulate the preamplifier module and convert the analog signal V output in step 3 T Input preamplifier module, amplification factor is K1, output signal V A ;

[0012] Step 5: Use the Idealized ADC quantizer submodule to simulate the analog-to-digital conversion module. Input the signal output from step 4 into the analog-to-digital conversion module. Set the number of conversion bits to the number of bits of the A / D converter. Output signal D AD ;

[0013] Step 6: Construct a sampling module to convert the signal D output in step 5 AD Input sampling module, subtract the positive and negative half-cycle sampling signals D1 and D2 to obtain signal D sa ;

[0014] Step 7: Construct a rate integration module to convert the signal D output from step 6 sa Input the fiber optic gyro output module, and after one integration, output the digital value D of the fiber optic gyro output out ;

[0015] Step 8: Build a step wave generation module and convert the digital value D output in step 7 out Input the step wave generation module, and output the step wave D after the second integration. step After multiplying by the feedback coefficient K1, it is superimposed with the modulated square wave after a time delay of τ, and the output signal D M ;

[0016] Step 9: Use the MATLAB Function submodule to simulate the 2π reset module and convert the signal D output in step 8 M Input 2π reset module, output reset signal D ’ M ;

[0017] Step 10: Use the Gain submodule to adjust the output signal D of step 9 ’ M After D / A conversion and post-amplification, it is divided into two parts. One part is subtracted from the other part after a time delay of τ to form an analog modulation signal V M ;

[0018] Step 11: Build a Y-waveguide modulation module and convert the analog modulation signal V output in step 10 M After multiplying with the Y waveguide modulation coefficient, the signal V is obtained. Y , as the variable in step 2 to perform phase modulation and closed-loop feedback on the light wave.

[0019] Furthermore, the specific steps of calculating the interference light intensity I in step 2 are:

[0020] Step 2-1: Create the Jones matrix E of the light source S :

[0021]

[0022] Where p is the polarization degree of the light source; E x is the light vector vibrating in the x direction; E y is the light vector vibrating in the y direction;

[0023] Step 2-2: Create the Jones matrix of the coupler:

[0024] Since there is a phase difference of π / 2 between the transmitted light wave and the coupled light wave of the coupler, for the transmitted light wave:

[0025]

[0026] For coupled light waves:

[0027]

[0028] In the formula, J T is the transmission matrix of the transmitted light wave; J C is the transmission matrix of coupled light waves; γ is the additional loss of the coupler; K is the splitting ratio of the coupler; j is the imaginary unit;

[0029] Step 2-3: Establish the Jones matrix P of the polarizer;

[0030]

[0031] Where ε is the amplitude extinction coefficient;

[0032] Step 2-4: Establish the Jones matrix M of the phase modulator;

[0033] When the modulation signal applied is When , for a light wave propagating clockwise, its transmission matrix is:

[0034]

[0035] For a light wave propagating counterclockwise, the transmission matrix is

[0036]

[0037] In the formula, is the modulation signal of the light wave propagating clockwise; is the modulated signal of the light wave propagating counterclockwise;

[0038] Step 2-5: Establish the Jones matrix R of the fiber ring;

[0039]

[0040] In the formula, The Sagnac phase shift caused by the rotation of the gyroscope;

[0041] Step 2-6: Multiply the Jones matrices of each optical device in sequence according to the optical path connection method to obtain the output light field E of the light wave transmitted in the clockwise and counterclockwise directions. CW and E CCW They are:

[0042]

[0043] Where P T is the transposed matrix of P;

[0044] Step 2-7: Calculate the interference light intensity as:

[0045]

[0046] In the formula, For E CW The conjugate transposed matrix of ; For E CCW The conjugate transposed matrix of ; I0 is the light intensity output by the light source.

[0047] Furthermore, the signal V output in step 3 T The expression is:

[0048] V T =ηRI

[0049] Where η is the detector responsivity and R is the transimpedance.

[0050] Furthermore, the signal D output in step 5 AD for:

[0051]

[0052] Among them, N AD is the number of bits of the A / D converter.

[0053] Furthermore, the step 6 specifically includes:

[0054] Step 6-1: Use the Pulse Generator submodule to generate a clock signal with a period of 2τ;

[0055] Step 6-2: Use the Transport Delay submodule to delay the generated clock signal by τ1=0.1τ and τ2=1.1τ respectively to avoid spike pulses;

[0056] Step 6-3: Convert the output signal D of step 5 AD After being divided into two parts, the Sample and Hold submodule is used to sample the signals of the positive half cycle and the negative half cycle respectively. The sampling trigger signals are the clock signals D1 and D2 after delays of τ1 and τ2 respectively.

[0057] Step 6-4: Subtract the two output signals D1 and D2 to obtain the differential signal D sa .

[0058] Furthermore,

[0059] In step 7, the differential signal D output from step 6 is processed by using the Sample and Hold submodule. sa Perform an integration;

[0060] In step 8, the Sample and Hold submodule is used to sample the digital signal D output in step 7. out Perform a quadratic integral;

[0061] The trigger signal of the Sample and Hold submodule is generated by the Pulse Generator submodule and has a period of 2τ.

[0062] Furthermore, the above steps 1-11 are executed to complete the closed loop of the fiber optic gyroscope.

[0063] A closed-loop fiber optic gyroscope system proposed in the present invention is characterized in that it is modeled using the above method, and includes an optical path module, a photoelectric conversion module, a preamplifier module, an analog-to-digital conversion module, a sampling module, a rate integration module, a step wave generation module, a 2π reset module, a D / A conversion module, a post-amplifier module and a Y-waveguide modulation module.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] 1. The modeling of the existing closed-loop fiber optic gyroscope is mainly based on control theory. The model simplifies and approximately linearizes each module of the closed-loop fiber optic gyroscope, and cannot fully reflect the change law of the input and output signals in each module of the closed-loop fiber optic gyroscope. The present invention proposes a closed-loop fiber optic gyroscope system modeling method, which models each module in the closed-loop fiber optic gyroscope and can accurately reflect the change of the signal of each module in the closed-loop fiber optic gyroscope.

[0066] 2. Inputting the parameters of each device, modulation coefficient and other indicators into the closed-loop fiber optic gyroscope system model established by the present invention can accurately reflect the changing law of the output performance of the closed-loop fiber optic gyroscope. Therefore, the model provides a clear basis for the design of the closed-loop fiber optic gyroscope parameters.

[0067] 3. During the debugging process of the closed-loop fiber optic gyroscope, the parameters of each module are substituted into the closed-loop fiber optic gyroscope system model established by the present invention, so that the influence of each module parameter on the performance of the fiber optic gyroscope can be more intuitively understood, thereby avoiding problems such as damage to components and low debugging efficiency caused by traditional debugging methods such as repeated replacement of components and adjustment of software parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The drawings described below are only an example of the present invention. A person skilled in the art can obtain other drawings based on these drawings without creative work.

[0069] Figure 1 It is a closed-loop fiber optic gyroscope system model;

[0070] Figure 2 is the input angular rate of the fiber optic gyroscope;

[0071] Figure 3 is the interference light intensity output by the optical path;

[0072] Figure 4 It is the digital signal output by the analog-to-digital conversion module;

[0073] Figure 5 The signal output by the sampling module, where the red curve is the signal output by sampling the positive half cycle of the square wave, the yellow curve is the signal output by sampling the negative half cycle of the square wave, and the green curve is the difference signal output after the difference between the positive and negative half cycle sampling results of the square wave;

[0074] Figure 6 The output signal is the result of integrating the difference signal of the sampled output once;

[0075] Figure 7 It is the step wave signal output by the secondary integration;

[0076] Figure 8 is a square wave modulation signal;

[0077] Fig. 9 It is the total modulation signal output after the square wave modulation signal and the step wave signal are superimposed;

[0078] Fig.10 is the total modulation signal after 2π reset;

[0079] Fig.11 is the phase difference produced by the Y waveguide. DETAILED DESCRIPTION

[0080] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0081] See attached Figure 1 The present invention provides a closed-loop fiber optic gyroscope system modeling method, which specifically includes the following steps:

[0082] Step 1: Use the Step submodule to simulate the input angular rate of the fiber optic gyroscope Its waveform is as Figure 2 shown.

[0083] Step 2: Use the MATLAB Function submodule to simulate the optical path module and convert the angular velocity output in step 1 Input the optical path module, and use the optical path module to simulate and calculate the interference light intensity I output by the optical path part, such as Figure 3 As shown, since this example adopts square wave modulation, the output signal of the fiber optic gyroscope is a square wave.

[0084] At present, the modeling of optical modules usually adopts the Jones matrix method. This method requires first establishing the Jones matrix of optical devices such as light source, coupler, polarizer, phase modulator, beam splitter and fiber ring, and then multiplying the Jones matrices of each optical device in sequence according to the optical path connection method to obtain the output light field of the light wave transmitted in the clockwise and counterclockwise directions. Finally, the total light intensity of the optical path output is calculated according to the interference principle. The specific implementation steps are:

[0085] Step 2-1: Create the Jones matrix E of the light source S .

[0086]

[0087] Where p is the polarization degree of the light source; E x is the light vector vibrating in the x direction; E y is the light vector vibrating in the y direction.

[0088] Step 2-2: Create the Jones matrix of the coupler.

[0089] Since there is a phase difference of π / 2 between the transmitted light wave and the coupled light wave of the coupler, for the transmitted light wave:

[0090]

[0091] For coupled light waves:

[0092]

[0093] In the formula, J T is the transmission matrix of the transmitted light wave; J C is the transmission matrix of the coupled light wave; γ is the additional loss of the coupler; K is the coupler splitting ratio; j is the imaginary unit.

[0094] Step 2-3: Establish the Jones matrix P of the polarizer.

[0095]

[0096] Where ε is the amplitude extinction coefficient.

[0097] Step 2-4: Establish the Jones matrix M of the phase modulator.

[0098] When the modulation signal applied is When , for a light wave propagating clockwise, its transmission matrix is:

[0099]

[0100] For a light wave propagating counterclockwise, the transmission matrix is:

[0101]

[0102] In the formula, is the modulation signal of the light wave propagating clockwise; is the modulation signal of the light wave propagating counterclockwise.

[0103] Step 2-5: Establish the Jones matrix R of the fiber ring.

[0104]

[0105] In the formula, is the Sagnac phase shift caused by the rotation of the gyroscope.

[0106] Step 2-6: Multiply the Jones matrices of each optical device in sequence according to the optical path connection method to obtain the output light field E of the light wave transmitted in the clockwise and counterclockwise directions. CW and E CCW They are:

[0107]

[0108]

[0109] Where P T is the transposed matrix of P.

[0110] Step 2-7: Calculate the interference light intensity as:

[0111]

[0112] In the formula, For E CW The conjugate transposed matrix of ; For E CCW The conjugate transposed matrix of ; I0 is the light intensity output by the light source.

[0113] Step 3: Use the Gain submodule to simulate the photoelectric conversion module of the detector, input the interference light intensity I output in step 2 into the photoelectric conversion module, and the output signal is:

[0114] V T =ηRI

[0115] Where η is the detector responsivity and R is the transimpedance.

[0116] Step 4: Use the Gain submodule to simulate the preamplifier module and convert the analog signal V output in step 3 T Input preamplifier module, the amplification factor is K1, the output signal is:

[0117] V A =K1V T

[0118] Step 5: Use the Idealized ADC quantizer submodule to simulate the analog-to-digital conversion module. Input the signal output from step 4 into the analog-to-digital conversion module. Set the number of conversion bits to the number of bits of the A / D converter. The output signal is:

[0119]

[0120] Where N AD is the number of bits of the A / D converter.

[0121] The interference signal is converted into a voltage signal after passing through the photoelectric conversion module and the preamplifier module, and then converted into a digital signal after passing through the analog-to-digital conversion module. Figure 4 shown.

[0122] Step 6: Construct a sampling module to convert the signal D output in step 5 AD Input sampling module, subtract the positive and negative half-cycle sampling signals D1 and D2 to obtain signal D sa .

[0123] Step 6-1: Use the Pulse Generator submodule to generate a clock signal with a period of 2τ;

[0124] Step 6-2: Use the Transport Delay submodule to delay the generated clock signal by τ1=0.1τ and τ2=1.1τ respectively to avoid spike pulses;

[0125] Step 6-3: Convert the output signal D of step 5 AD After being divided into two parts, the Sample and Hold submodules are used to sample the signals of the positive half cycle and the negative half cycle respectively. The sampling trigger signals are the clock signals D1 and D2 after delays of τ1 and τ2 respectively. Figure 5 As shown in red and yellow signals;

[0126] Step 6-4: Subtract the two output signals D1 and D2 to obtain the differential signal D sa like Figure 5 Shown in green signal.

[0127] Step 7: Construct a rate integration module to convert the signal D output from step 6 sa Input the fiber optic gyro output module, and after one integration, output the digital value D of the fiber optic gyro output out .

[0128] The Pulse Generator submodule is used to generate the trigger signal of the Sample and Hold submodule with a period of 2τ; the Sample and Hold submodule is then used to generate the differential signal D output in step 6. sa Perform an integration and obtain an integrated signal such as Figure 6 As shown, the first integrated signal is used as the digital quantity D output by the fiber optic gyroscope. out , on the other hand it serves as the negative feedback signal of the fiber optic gyroscope.

[0129] Step 8: Build a step wave generation module and use the Sample and Hold submodule again to generate the digital signal D output in step 7. out After the second integration, the step wave signal D is obtained. step ,like Figure 7 As shown, the step wave signal D step After multiplying by the feedback coefficient K1, it is then delayed by time τ (τ is the transit time of the fiber optic gyroscope) and Figure 8 The square wave modulation signals shown are superimposed to generate the total modulation signal D M ,like Fig. 9 shown.

[0130] Step 9: Use the MATLAB Function submodule to simulate the 2π reset module. Due to the limitation of the number of bits of the D / A converter, the total modulation signal cannot be increased infinitely, and a 2π reset is required to convert the total modulation signal D output in step 8 into M Input 2π reset module, output reset signal D ’ M like Fig.10 shown.

[0131] Step 10: Use the Gain submodule to adjust the output signal D of step 9 ’ M After D / A conversion and post-amplification, it is divided into two parts. One part is subtracted from the other part after a time delay of τ to form an analog modulation signal V M .

[0132] Step 11: Build a Y-waveguide modulation module and convert the analog modulation signal V output in step 10 M The phase difference signal V generated between the clockwise and counterclockwise propagating light waves is multiplied by the Y waveguide modulation coefficient. Y like Fig.11 As shown, the phase difference signal V Y In the input optical path module, the light wave is phase modulated and closed-loop fed back as the variable in step 2, thus completing the closed loop of the fiber optic gyroscope.

[0133] Run the model established in steps 1-11 and observe the gyroscope output signal and the output signals of each module.

[0134] The present invention models each module of the closed-loop fiber optic gyroscope based on the working principle, and finally forms a system model. The signals output by each module of the model are consistent with the actual output signals of the closed-loop fiber optic gyroscope, which can accurately reflect the influence of each module on the output characteristics of the closed-loop fiber optic gyroscope, and provides theoretical support for the parameter design and debugging of the closed-loop fiber optic gyroscope.

Claims

1. A closed-loop fiber optic gyroscope system modeling method, characterized in that: The following steps are involved: Step 1: Use the Step submodule to simulate the input angular rate of the fiber optic gyroscope Step 2: Use the MATLAB Function submodule to simulate the optical path module and convert the angular velocity output from step 1 into Input optical path module, output interference light intensity I; Step 3: Use the Gain submodule to simulate the photoelectric conversion module of the detector, input the interference light intensity I output in step 2 into the photoelectric conversion module, and output the signal V T ; Step 4: Use the Gain submodule to simulate the preamplifier module and convert the analog signal V output in step 3 T Input preamplifier module, amplification factor is K1, output signal V A ; Step 5: Use the Idealized ADC quantizer submodule to simulate the analog-to-digital conversion module. Input the signal output from step 4 into the analog-to-digital conversion module. Set the number of conversion bits to the number of bits of the A / D converter. Output signal D AD ; Step 6: Construct a sampling module to convert the signal D output in step 5 AD Input sampling module, subtract the positive and negative half-cycle sampling signals D1 and D2 to obtain signal D sa ; Step 7: Construct a rate integration module to convert the signal D output from step 6 sa Input the fiber optic gyro output module, and after one integration, output the digital value D of the fiber optic gyro output out ; Step 8: Build a step wave generation module and convert the digital value D output in step 7 out Input the step wave generation module, and output the step wave D after the second integration. step After multiplying by the feedback coefficient K1, it is superimposed with the modulated square wave after a time delay of τ, and the output signal D M ; Step 9: Use the MATLAB Function submodule to simulate the 2π reset module and convert the signal D output in step 8 M Input 2π reset module, output reset signal D ’ M ; Step 10: Use the Gain submodule to adjust the output signal D of step 9 ’ M After D / A conversion and post-amplification, it is divided into two parts. One part is subtracted from the other part after a time delay of τ to form an analog modulation signal V M ; Step 11: Build a Y-waveguide modulation module and convert the analog modulation signal V output in step 10 M After multiplying with the Y waveguide modulation coefficient, the signal V is obtained. Y , as the variable in step 2 to perform phase modulation and closed-loop feedback on the light wave.

2. A closed-loop fiber optic gyroscope system modeling method as claimed in claim 1, characterized in that: The specific steps for calculating the interference light intensity I in step 2 are: Step 2-1: Create the Jones matrix E of the light source S : Where p is the polarization degree of the light source; E x is the light vector vibrating in the x direction; E y is the light vector vibrating in the y direction; Step 2-2: Create the Jones matrix of the coupler: Since there is a phase difference of π / 2 between the transmitted light wave and the coupled light wave of the coupler, for the transmitted light wave: For coupled light waves: In the formula, J T is the transmission matrix of the transmitted light wave; J C is the transmission matrix of coupled light waves; γ is the additional loss of the coupler; K is the splitting ratio of the coupler; j is the imaginary unit; Step 2-3: Establish the Jones matrix P of the polarizer; Where ε is the amplitude extinction coefficient; Step 2-4: Establish the Jones matrix N of the phase modulator; When the modulation signal applied is When , for a light wave propagating clockwise, its transmission matrix is: For a light wave propagating counterclockwise, the transmission matrix is In the formula, is the modulation signal of the light wave propagating clockwise; is the modulation signal of the light wave propagating counterclockwise; Step 2-5: Establish the Jones matrix R of the fiber ring; In the formula, The Sagnac phase shift caused by the rotation of the gyroscope; Step 2-6: Multiply the Jones matrices of each optical device in sequence according to the optical path connection method to obtain the output light field E of the light wave transmitted in the clockwise and counterclockwise directions. CW and E CCW They are: Where P T is the transposed matrix of P; Step 2-7: Calculate the interference light intensity as: In the formula, For E CW The conjugate transposed matrix of ; For E CCW The conjugate transposed matrix of ; I0 is the light intensity output by the light source.

3. A closed-loop fiber optic gyroscope system modeling method as claimed in claim 1, characterized in that: The output signal V in step 3 T The expression is: IN T =ηRI Where η is the detector responsivity and R is the transimpedance.

4. A closed-loop fiber optic gyroscope system modeling method as claimed in claim 1, characterized in that: The signal D output in step 5 AD for: Among them, N AD is the number of bits of the A / D converter.

5. A closed-loop fiber optic gyroscope system modeling method as claimed in claim 1, characterized in that: The step 6 specifically includes: Step 6-1: Use the Pulse Generator submodule to generate a clock signal with a period of 2τ; Step 6-2: Use the Transport Delay submodule to delay the generated clock signal by τ1=0.1τ and τ2=1.1τ respectively to avoid spike pulses; Step 6-3: Convert the output signal D of step 5 AD After being divided into two parts, the Sample and Hold submodule is used to sample the signals of the positive half cycle and the negative half cycle respectively. The sampling trigger signals are the clock signals D1 and D2 after delays of τ1 and τ2 respectively. Step 6-4: Subtract the two output signals D1 and D2 to obtain the differential signal D sa .

6. A closed-loop fiber optic gyroscope system modeling method as claimed in claim 1, characterized in that: In step 7, the differential signal D output from step 6 is processed by using the Sample and Hold submodule. sa Perform an integration; In step 8, the Sample and Hold submodule is used to sample the digital signal D output in step 7. out Perform a quadratic integral; The trigger signal of the Sample and Hold submodule is generated by the Pulse Generator submodule and has a period of 2τ.

7. A closed-loop fiber optic gyroscope system modeling method as described in claims 1-6, characterized in that: Run steps 1-11 to complete the closed loop of the fiber optic gyroscope.

8. A closed-loop fiber optic gyroscope system, characterized in that: The modeling is performed using the method described in any one of claims 1 to 7, including an optical path module, a photoelectric conversion module, a preamplifier module, an analog-to-digital conversion module, a sampling module, a rate integration module, a step wave generation module, a 2π reset module, a D / A conversion module, a post-amplifier module and a Y-waveguide modulation module.

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