A method for online compensation of modulation depth of fiber optic gyroscope

Abstract

This invention discloses an online method for compensating the modulation depth of a fiber optic gyroscope, the steps of which include: 1) determining the optimal modulation depth φ of the target fiber optic gyroscope. m0 ;2) Establish modulation depth φ m 1) The relationship between ambient temperature T and modulation voltage V applied to the Y-waveguide of the target fiber optic gyroscope is given by the formula, where k and σ0 are constants to be measured; 2) Obtain any two sets of parameters of the target fiber optic gyroscope, each set including an ambient temperature value, an applied modulation voltage value, and a corresponding modulation depth value; substitute these two sets of parameters into the formula to solve for k and σ0; 3) Compensate for the modulation depth of the target fiber optic gyroscope by adjusting the applied modulation voltage V according to the formula, so that the modulation depth φ of the target fiber optic gyroscope is increased. m Always maintain the optimal modulation depth φ m0 .

Description

Technical Field

[0001] This invention belongs to the field of fiber optic gyroscope technology and relates to an online method for compensating the modulation depth of a fiber optic gyroscope. Background Technology

[0002] A fiber optic gyroscope is a sensor used to measure the angular motion of an object. After years of research and development, fiber optic gyroscopes have been widely used in many fields such as inertial navigation, earthquake monitoring, and precision measurement due to their advantages such as low cost, all-solid-state operation, high resolution, no rotating parts, long service life, and large dynamic range.

[0003] Fiber optic gyroscopes can achieve extremely high-precision angular motion measurements. However, a significant challenge lies in their susceptibility to environmental factors, particularly temperature. When operating in environments with drastic temperature variations, the temperature field introduces substantial additional errors, severely interfering with accurate measurements and greatly limiting their application in complex scenarios. Temperature-induced variations in the modulation depth of the integrated optical modulator (Y-waveguide) are a major contributor to these errors. Therefore, real-time online compensation based on changes in the modulation depth of the fiber optic gyroscope is crucial for suppressing temperature-induced measurement errors.

[0004] Traditional fiber optic gyroscope modulation depth has the following drawbacks:

[0005] 1. The 2π parameter, i.e. half-wave voltage, in the existing technology only adjusts the 2π parameter itself, which is not very practical for fiber optic gyroscopes.

[0006] 2. The 2π parameter adjustment in the existing technology must be achieved in a closed-loop fiber optic gyroscope under the premise of square wave modulation and demodulation, and a second closed loop is required.

[0007] 3. Existing technologies require full-temperature testing of fiber optic gyroscopes, which involves many key parameters.

[0008] 4. Existing technologies require adjusting the parameters and highest-order coefficients of the fitting polynomial based on the accuracy of the fiber optic gyroscope and the usage environment, resulting in high algorithm complexity. Summary of the Invention

[0009] To address the problems existing in the prior art, the present invention aims to provide an online compensation method for the modulation depth of a fiber optic gyroscope. This method adjusts the voltage based on real-time temperature data to compensate the modulation depth of the fiber optic gyroscope online. The present invention is applicable to fiber optic gyroscopes of any structure, requiring only the determination of compensation parameters at two temperature points.

[0010] The technical solution of this invention is as follows:

[0011] A method for online compensation of modulation depth of a fiber optic gyroscope, comprising the following steps:

[0012] 1) Determine the optimal modulation depth φ of the target fiber optic gyroscope m0 ;

[0013] 2) Establish modulation depth φ m The relationship between ambient temperature T and modulation voltage V applied to the Y-waveguide of the target fiber optic gyroscope. Where k,σ0 are the constants to be measured;

[0014] 3) Obtain any two sets of parameters from the target fiber optic gyroscope. Each set of parameters includes an ambient temperature value, an applied modulation voltage value, and a corresponding modulation depth value. Substitute these two sets of parameters into the relevant formula. Solve for k and σ0;

[0015] 4) According to the relation The modulation depth of the target fiber optic gyroscope is compensated by adjusting the applied modulation voltage V, thereby increasing the modulation depth φ of the target fiber optic gyroscope. m Always maintain the optimal modulation depth φ m0 .

[0016] According to claim 1, the method is characterized in that the method for compensating the modulation depth of the target fiber optic gyroscope is as follows:

[0017] 21) Set the voltage error threshold ε φ ;

[0018] 22) Obtain the real-time modulation depth φ of the target fiber optic gyroscope. m ;

[0019] 23) If |φ m0 -φ m |>ε φ Then proceed to step 24); otherwise return to step 22.

[0020] 24) Adjust the applied voltage value V to compensate for the modulation depth of the target fiber optic gyroscope; wherein, the amount of change in the applied modulation voltage V is adjusted.

[0021] Furthermore, the real-time modulation depth φ of the target fiber optic gyroscope is calculated using the ratio of the second harmonic to the fourth harmonic. m .

[0022] Furthermore, the real-time modulation depth φ of the target fiber optic gyroscope is calculated using the ratio of the first harmonic to the third harmonic. m .

[0023] Furthermore, the real-time modulation depth φ of the target fiber optic gyroscope is calculated using a lookup table. m.

[0024] Furthermore, the target fiber optic gyroscope is an open-loop fiber optic gyroscope with an optimal modulation depth φ. m0 = 2.7 rad.

[0025] Furthermore, the target fiber optic gyroscope is a closed-loop fiber optic gyroscope with an optimal modulation depth.

[0026] This invention directly adjusts the modulation depth parameter, making it more widely applicable and not limited to closed-loop fiber optic gyroscopes; it is also suitable for open-loop fiber optic gyroscopes.

[0027] This invention does not require full-temperature testing; it only requires calculating the coefficient at any two temperature points.

[0028] This invention does not involve polynomial fitting or multi-parameter fitting, has low computational complexity, is simple in form, and conforms to actual measurement practices.

[0029] The feedback control process of this invention is simple and effective.

[0030] The advantages of this invention are as follows:

[0031] In existing technologies, the 2π parameter, or half-wave voltage, is adjusted only for the 2π parameter itself. This invention, however, directly adjusts the modulation depth, which corresponds to the half-wave voltage, making it more practical for fiber optic gyroscopes.

[0032] Existing technologies require 2π parameter adjustment to be implemented within a closed-loop fiber optic gyroscope, under the premise of square wave modulation and demodulation, and necessitate a second closed loop. This invention, however, directly adjusts the modulation depth, which corresponds to the half-wave voltage. This invention places no structural requirements on the fiber optic gyroscope and can be implemented in any fiber optic gyroscope, making it highly practical.

[0033] Existing technologies require full-temperature testing of fiber optic gyroscopes, while this invention does not require full-temperature testing; it only requires determining key parameters at two temperatures.

[0034] Existing technologies require adjusting the parameters and highest-order coefficients of the fitting polynomial based on the accuracy of the fiber optic gyroscope and the usage environment. The compensation method used in this invention has a fixed form and does not require additional adjustments for different fiber optic gyroscopes.

[0035] This invention starts from the definition and physical principles of half-wave voltage, and introduces ambient temperature T into the feedback process of modulation depth, giving a relationship between modulation depth, ambient temperature, and applied voltage. Compared with polynomial fitting methods, its relationship model is more consistent with physical reality. Attached Figure Description

[0036] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0038] The technical solution of the present invention includes the following steps:

[0039] 1. Determine the optimal modulation depth φ of the currently used fiber optic gyroscope. m0 For open-loop fiber optic gyroscopes, φ m0 Typically 2.7 rad. For closed-loop fiber optic gyroscopes, φ m0 Usually

[0040] 2. Based on the modulation depth φ m The relationship between the modulation voltage V applied to the Y waveguide and the modulation depth φ is given. m The relationship between the applied voltage V and the ambient temperature T. Modulation depth φ m The relationship between the applied voltage V and the voltage V is:

[0041]

[0042] In the formula, r is the electro-optic coefficient of the Y-waveguide in the fiber optic gyroscope, Γ is the overlap factor between the applied electric field and the optical field in the fiber optic gyroscope, L is the length of the modulation electrode of the Y-waveguide in the fiber optic gyroscope, and n e λ is the unusual refractive index of the Y-waveguide in the fiber optic gyroscope, λ is the wavelength of the light source used in the fiber optic gyroscope, and b is the distance between the two electrode plates of the Y-waveguide in the fiber optic gyroscope.

[0043] Based on the definition of half-wave voltage: the voltage corresponding to a modulation depth of π, the modulation depth φ can be given. m Half-wave voltage V π The relationship between the applied voltage V and the following formula:

[0044]

[0045] Due to modulation depth φ m The relationship between the voltage and ambient temperature T is directly proportional; therefore, the half-wave voltage is also directly proportional to ambient temperature T, which can be expressed as:

[0046] V π =kT+σ0

[0047] Where k, σ0 are the constants to be measured. Therefore, the modulation depth φ m The relationship between ambient temperature T and applied voltage V can be expressed as:

[0048]

[0049] 3. Based on the temperature values ​​at any two points, the applied modulation voltage value, and the corresponding modulation depth value, we can solve for k and σ0.

[0050] 4. According to The modulation depth of the fiber optic gyroscope is compensated by adjusting the applied modulation voltage value V, thereby increasing the modulation depth φ of the fiber optic gyroscope. m Always maintain the optimal modulation depth φ m0 .

[0051] Specifically, the voltage adjustment steps in step 4 are as follows:

[0052] 1) Set the voltage error threshold ε φ ;

[0053] 2) Calculate the real-time modulation depth φ of the fiber optic gyroscope using the existing demodulation method. m ;

[0054] 3) Determine |φ m0 -φ m |>ε φ If false, return to step 2). If true, proceed to step 4.

[0055] 4) Adjust the voltage to perform modulation depth compensation. Specifically, the amount of modulation voltage change adjusted is as follows:

[0056] In the above scheme, the modulation depth φ m There are many names for gyroscopes, including but not limited to Y-waveguide bias voltage, gyroscope operating depth, and gyroscope operating point.

[0057] Real-time modulation depth φ m There are various measurement methods, including but not limited to calculations using the ratio of the second harmonic to the fourth harmonic, calculations using the ratio of the first harmonic to the third harmonic, and calculations by looking up tables.

[0058] When adjusting the voltage for modulation depth compensation, the specific adjustment voltage value does not necessarily need to be the one specified in this article. It can be determined based on the actual usage environment and usage conditions.

[0059] Although specific embodiments of the invention have been disclosed for illustrative purposes to aid in understanding and implementing the invention, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the content disclosed in the preferred embodiments, and the scope of protection claimed by the invention is defined by the claims.

Claims

1. An on-line compensation method for modulation depth of fiber-optic gyroscope, comprising the steps of: 1) determining the optimal modulation depth φ of the target fiber-optic gyroscope m0 ; 2) Establish the modulation depth φ m The relationship between the ambient temperature T and the modulation voltage V applied to the target fiber-optic gyroscope Y waveguide Wherein k, σ0 are constants to be measured; 3) obtaining any two groups of parameters of the target fiber-optic gyroscope, each group of parameters comprising an ambient temperature value, an applied modulation voltage value, and a corresponding modulation depth value; substituting the two groups of parameters into the relationship solving k and σ0; 4) according to the relationship By adjusting the applied modulation voltage V to compensate for the modulation depth of the target fiber optic gyroscope, so that the modulation depth φ m Always keep the optimal modulation depth φ m0 ; wherein, The method for compensating the modulation depth of the target fiber optic gyroscope is: 41) setting a voltage error threshold ε φ ; 42) obtaining the real-time modulation depth φ m of the target fiber optic gyroscope; 43) if |φ m0 -φ m |>ε φ , then go to step 44), otherwise return to step 42); 44) adjusting the applied modulation voltage V to compensate the modulation depth of the target fiber optic gyroscope; wherein the change amount of adjusting the applied modulation voltage V is 2. The method of claim 1, wherein, The real-time modulation depth φ of the target fiber-optic gyroscope is calculated by using the ratio of the second harmonic and the fourth harmonic m .

3. The method of claim 1, wherein, The real-time modulation depth φ of the target fiber-optic gyroscope is calculated by using the ratio of the first harmonic and the third harmonic m .

4. The method of claim 1, wherein, The real-time modulation depth φ of the target fiber optic gyroscope is calculated by using a lookup table m .

5. The method of claim 1, wherein, The target fiber-optic gyroscope is an open-loop fiber-optic gyroscope, and the optimal modulation depth φ m0 = 2.7 rad.

6. The method of claim 1, wherein, The target fiber-optic gyroscope is a closed-loop fiber-optic gyroscope, and the optimal modulation depth

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