On-line compensation method for modulation depth of fiber-optic gyroscope

Abstract

The invention discloses an online compensation method for the modulation depth of a fiber-optic gyroscope. The method comprises the following steps: 1) determining the optimal modulation depth phi m0 of a target fiber-optic gyroscope; 2) establishing a relational expression # imgabs0 # among the modulation depth phi m, the ambient temperature T and the modulation voltage V applied to the Y waveguide of the target fiber-optic gyroscope, wherein k and sigma 0 are constants to be measured; 3) acquiring any two groups of parameters of the target fiber-optic gyroscope, wherein each group of parameters comprises an environment temperature value, an applied modulation voltage value and a corresponding modulation depth value; substituting the two groups of parameters into a relational expression # imgabs1 # to solve k and sigma 0; and 4) compensating the modulation depth of the target fiber-optic gyroscope by adjusting the applied modulation voltage V according to the relational expression # imgabs2, so that the modulation depth phi m of the target fiber-optic gyroscope is always kept at the optimal modulation depth phi m0.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber optic gyroscopes and relates to an online compensation method for modulation depth of a fiber optic gyroscope. Background Art

[0002] Fiber optic gyroscope is a sensor that measures the angular motion of an object. After years of research and development, fiber optic gyroscope has been widely used in many fields such as inertial navigation, earthquake monitoring, precision measurement, etc. due to its advantages such as low cost, all solid state, high resolution, no moving parts, long service life and large dynamic range.

[0003] Fiber optic gyroscopes can achieve extremely high-precision angular motion measurement, but the problem that comes with it is that the fiber optic gyroscope itself is easily affected by environmental factors, especially the temperature. When the fiber optic gyroscope works in an environment with drastic temperature changes, the temperature field will introduce a large amount of additional errors, seriously interfering with the accurate measurement of the fiber optic gyroscope, greatly limiting the application of the fiber optic gyroscope in complex scenarios. Among them, the change in modulation depth of the integrated optical modulator (Y waveguide) caused by temperature is an important cause of the error. Therefore, real-time online compensation of the fiber optic gyroscope based on the change in its modulation depth is of great significance to suppressing the measurement error of the fiber optic gyroscope caused by temperature.

[0004] The traditional fiber optic gyro modulation depth has the following disadvantages:

[0005] 1. The 2π parameter in the prior art is the half-wave voltage, which only adjusts the 2π parameter itself, and is not practical for a fiber optic gyroscope.

[0006] 2. The 2π parameter adjustment in the prior art must be implemented 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. The existing technology requires full-temperature testing of the fiber optic gyroscope, which requires many key parameters.

[0008] 4. The existing technology needs to adjust the parameters and the highest-order coefficients of the fitting polynomial according to the accuracy of the fiber optic gyroscope and the use environment, and the algorithm complexity is high. Summary of the invention

[0009] In view of the problems existing in the prior art, the purpose of the present invention is to provide an online compensation method for modulation depth of a fiber optic gyroscope, which is used to adjust the voltage according to real-time temperature data, so as to compensate the modulation depth of the fiber optic gyroscope online. The present invention can be applied to a fiber optic gyroscope of any structure, and only needs to determine the compensation parameters at two temperature points.

[0010] The technical solution of the present invention is:

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

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

[0013] 2) Establish the modulation depth φ m The relationship between the ambient temperature T and the modulation voltage V applied to the target fiber gyroscope Y waveguide is: Among them, k,σ 0 is the constant to be measured;

[0014] 3) Obtain any two sets of parameters of 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 the two sets of parameters into the relationship Solve for k,σ 0 ;

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

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

[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 go to step 24), otherwise return to step 22);

[0020] 24) adjusting the applied voltage value V to compensate for the modulation depth of the target fiber optic gyroscope; wherein the 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 by table lookup. m .

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

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

[0026] The present invention directly adjusts the parameter of modulation depth, and has wider applicability, and is not limited to closed-loop fiber optic gyroscopes, but is also applicable to open-loop fiber optic gyroscopes.

[0027] The present invention does not need to perform full temperature testing, and only needs to take two temperature points at random to calculate the coefficient.

[0028] The present invention does not involve polynomial fitting or multi-parameter fitting, has a small amount of calculation, is simple in form, and conforms to measurement practice.

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

[0030] The advantages of the present invention are as follows:

[0031] The 2π parameter in the prior art is the half-wave voltage, and only the 2π parameter itself is adjusted. However, the present invention directly adjusts the modulation depth corresponding to the half-wave voltage, which is more practical for the fiber optic gyroscope.

[0032] The 2π parameter adjustment in the prior art must be implemented in a closed-loop fiber optic gyroscope under the premise of square wave modulation and demodulation, and a second closed loop is required. The present invention directly adjusts the modulation depth corresponding to the half-wave voltage. The present invention has no requirements on the structure of the fiber optic gyroscope and can be implemented in any fiber optic gyroscope, which is highly practical.

[0033] The prior art requires full-temperature testing of the fiber optic gyroscope, but the present invention does not require full-temperature testing and only requires determining key parameters at two temperatures.

[0034] The prior art needs to adjust the parameters and the highest-order coefficients of the fitting polynomial according to the accuracy and use environment of the fiber optic gyroscope. The compensation method used in the present invention is fixed in form and does not require additional adjustments for different fiber optic gyroscopes.

[0035] Starting from the definition and physical principle of half-wave voltage, the present invention introduces ambient temperature T in the feedback process of modulation depth, and provides a relationship between modulation depth, ambient temperature and applied voltage. Compared with the polynomial fitting method, its relationship model is more in line with physical reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention but not to limit the scope of the present invention.

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

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

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

[0041]

[0042] Where r is the electro-optic coefficient of the Y waveguide in the fiber gyroscope, Γ is the overlap factor of the external electric field and optical field of the fiber gyroscope, L is the modulation electrode length of the Y waveguide in the fiber gyroscope, and n e is the extraordinary light 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] According to the definition of half-wave voltage: the voltage corresponding to the modulation depth of π, the modulation depth φ can be given m , half-wave voltage V π , the relationship between the applied voltage V:

[0044]

[0045] Since the modulation depth φ m It is proportional to the ambient temperature T, so the half-wave voltage is also proportional to the ambient temperature T, which can be expressed as:

[0046] V π =kT+σ 0

[0047] Among them, k,σ 0 is the constant to be measured. Therefore, the modulation depth φ mThe relationship between the ambient temperature T and the applied voltage V can be expressed as:

[0048]

[0049] 3. According to the temperature value of any two points, the applied modulation voltage value and the corresponding modulation depth value, k and σ are solved. 0 ;

[0050] 4. According to The modulation depth of the fiber optic gyroscope is compensated by adjusting the applied modulation voltage value V, so that the modulation depth of the fiber optic gyroscope φ 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) According to the original demodulation method, the real-time modulation depth φ of the fiber optic gyroscope is obtained m ;

[0054] 3) Judge |φ m0 -φ m |>ε φ ? If false, go back to step 2). If true, go to step 4);

[0055] 4) Adjust the voltage to perform modulation depth compensation. The specific adjustment of the modulation voltage change is:

[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, gyroscope operating point, etc.

[0057] Real-time modulation depth φ m There are many measurement methods, including but not limited to calculation using the ratio of the second harmonic to the fourth harmonic, calculation using the ratio of the first harmonic to the third harmonic, table lookup calculation, etc.

[0058] When adjusting the voltage for modulation depth compensation, the specific adjustment voltage value does not necessarily need to be It can be determined according to the actual usage environment and usage conditions.

[0059] Although the specific embodiments of the present invention are disclosed for the purpose of illustration, the purpose is to help understand the content of the present invention and implement it accordingly, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the best embodiment, and the scope of the present invention is subject to the scope defined in the claims.

Claims

1. A method for online compensation of modulation depth of a fiber optic gyroscope, comprising the steps of: 1) Determine 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 gyroscope Y waveguide is: Among them, k,σ0 are the constants to be measured; 3) Obtain any two sets of parameters of 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 the two sets of parameters into the relationship Solve for k,σ0; 4) According to the relationship The modulation depth of the target fiber optic gyroscope is compensated by adjusting the applied modulation voltage V, so that the modulation depth of the target fiber optic gyroscope is φ m Always maintain the optimal modulation depth φ m0 .

2. The method according to claim 1, characterized in that The method for compensating the modulation depth of the target fiber optic gyroscope is: 21) Set the voltage error threshold ε φ ; 22) Obtain the real-time modulation depth φ of the target fiber optic gyroscope m ; 23) If |φ m0 -φ m |>ε φ Then go to step 24), otherwise return to step 22); 24) adjusting the applied modulation voltage V to compensate for the modulation depth of the target fiber optic gyroscope; wherein the change amount of the applied modulation voltage V is adjusted 3. The method according to claim 2, characterized in that 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 .

4. The method according to claim 2, characterized in that: The real-time modulation depth φ of the target fiber optic gyroscope is calculated by using the ratio of the first harmonic to the third harmonic. m .

5. The method according to claim 2, characterized in that: The real-time modulation depth φ of the target fiber optic gyroscope is calculated by table lookup. m .

6. The method according to claim 1 or 2, characterized in that: The target fiber optic gyroscope is an open-loop fiber optic gyroscope, and the optimal modulation depth φ m0 =2.7rad.

7. The method according to claim 1 or 2, characterized in that: The target fiber optic gyroscope is a closed-loop fiber optic gyroscope with an optimal modulation depth

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