A method for adjusting 2π voltage parameters of square wave modulated fiber optic gyroscope at full temperature start-up

Abstract

The present invention relates to the technical field of fiber optic gyroscopes, and in particular to a method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup, comprising: S1, adjusting the fiber optic gyroscope software to a parameter adjustment mode; S2, applying a preset virtual rotation speed to the fiber optic gyroscope, and generating a digital step wave with the virtual rotation speed as a closed-loop feedback amount; S3, after collecting the detector signal difference before and after the digital step wave is reset, calculating the 2π voltage error information, and adjusting the 2π voltage parameters through the 2π voltage error information; S4, analyzing whether the adjustment amount is less than a preset adjustment threshold when adjusting the 2π voltage parameters in S3, if less than, turning to S5, if not less than, returning to S2; S5, completing the parameter adjustment, and switching the fiber optic gyroscope software to a solution working mode. The method can still quickly realize the calibration of the 2π voltage parameters of the gyroscope under high or low temperature environmental conditions, and ensure the stability and rapidity of the 2π voltage parameter calibration of the gyroscope.

Description

Technical Field

[0001] The invention relates to the technical field of fiber optic gyroscopes, and in particular to a method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup. Background Art

[0002] Fiber optic gyroscopes are the core components of inertial navigation systems. The rotational angular velocity information provided by fiber optic gyroscopes can be used to complete the attitude calculation of the carrier. Among various types of fiber optic gyroscopes, closed-loop fiber optic gyroscopes based on digital step wave feedback have been widely used due to their high precision, large dynamic range, and good nonlinearity.

[0003] The accuracy of the fiber optic gyroscope is closely related to the two parameters of zero bias and scale factor, and these two parameters will change with the change of temperature environment. Studies have found that the change of 2π voltage of the integrated optical modulator (Y waveguide) with temperature is one of the important reasons for the drift of the two parameters of zero bias and scale factor of the fiber optic gyroscope. Therefore, servo adjustment of the 2π voltage parameters in the circuit according to the change of 2π voltage in the fiber optic gyroscope is of great significance for suppressing the temperature drift of the fiber optic gyroscope. At present, the common method in this field is to monitor the 2π voltage error of the fiber optic gyroscope and adjust the 2π voltage parameters according to the error. This technology is called 2π voltage parameter servo adjustment technology. The introduction of 2π voltage parameter servo adjustment technology enables the fiber optic gyroscope to servo adjust the 2π voltage parameters according to the change of temperature, so that it always remains accurate and adapts to different temperature requirements.

[0004] Due to the characteristics of the digital step wave (it cannot rise or fall infinitely), when the digital step wave exceeds the set upper or lower limit, it must be reset, that is, when it exceeds the upper limit, the preset reset value is subtracted, and when it exceeds the preset lower limit, the preset reset value is added. Therefore, in the square wave modulated fiber optic gyroscope, the 2π voltage error information is calculated based on the detector difference before and after the digital step wave is reset. The detector signal difference is the reset value subtracted when the digital step wave exceeds the upper limit, or the reset value added when it exceeds the lower limit. In order to comprehensively consider the full temperature range requirements of the fiber optic gyroscope, the initial value of the 2π voltage parameter is generally a given accurate value at normal temperature.

[0005] However, in actual work, if the fiber optic gyroscope works at low speed or no speed (the sensitive axis points to the east / west) in a low or high temperature environment, when the fiber optic gyroscope is started at this time, on the one hand, due to the temperature deviation from the normal temperature, the 2π voltage parameter will be inaccurate; on the other hand, due to the low speed, the digital step wave takes a long time to reset or does not reset, and the 2π voltage error information cannot be obtained in time. At this time, the servo adjustment of the 2π voltage parameter will be impossible, which will have a certain impact on the accuracy of the fiber optic gyroscope.

[0006] Therefore, when the FOG is in a high or low ambient temperature, how to quickly adjust the 2π voltage parameters during the startup phase to ensure the accuracy of the FOG has become an urgent problem to be solved. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a method for adjusting the 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup. Even in a low or high temperature environment, the 2π voltage parameters can be quickly adjusted during the startup phase to ensure the accuracy of the fiber optic gyroscope.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup comprises the following steps:

[0010] S1, adjusting the fiber optic gyro software to a parameter adjustment mode, and executing step S2;

[0011] S2, applying a preset virtual rotation speed to the fiber optic gyroscope, and generating a digital step wave with the virtual rotation speed as a closed-loop feedback quantity;

[0012] S3, collecting the detector signal difference before and after the digital step wave is reset, and calculating the 2π voltage error information, and then adjusting the 2π voltage parameter according to the 2π voltage error information;

[0013] S4, analyzing whether the adjustment amount is less than the preset adjustment threshold when the 2π voltage parameter is adjusted in S3, if so, go to S5, if not, return to S2;

[0014] S5, completing the parameter adjustment, switching the fiber optic gyroscope software to the solution working mode, and solving the rotation angular velocity of the fiber optic gyroscope.

[0015] Preferably, in S2, the virtual speed is a preset fixed speed value.

[0016] Preferably, in S5, after the fiber optic gyro software is switched to a solution working mode, a digital step wave is generated as a closed-loop feedback quantity using the odd and even sampling difference.

[0017] Preferably, in S5, when the digital step wave is reset using the odd-even sampling difference as the closed-loop feedback amount, the calculation formula for the odd-even sampling difference is:

[0018] ΔP=P - -P + =P0 sinΦ0sinΦ S ;

[0019] Among them, ΔP represents the difference between odd and even sampling, P -Represents the sampling value within the half cycle of negative modulation, P + Represents the sampling value in the half cycle of positive modulation; Φ S represents the phase difference caused by rotation, P0 represents the absolute stillness of the fiber optic gyroscope (Φ S =0) is the optical power reaching the detector, and Φ0 is the square wave modulation amplitude.

[0020] Preferably, in S5, when the odd-even sampling difference is used as the closed-loop feedback quantity to reset the digital step wave, the odd-even sampling value is:

[0021] Among them, Φ f is the closed-loop feedback phase.

[0022] Preferably, the closed-loop feedback phase Φ f Satisfy the condition Φ f =-Φ S .

[0023] Preferably, when the digital step wave is reset, the calculation formula of the detection signal is: In the formula,

[0024] Among them, τ is the time it takes for a light wave to propagate one circle in the optical fiber ring;

[0025] Φ fw =Φ f ±2π*k; where k is a positive integer.

[0026] Preferably, the Φ fw The calculation formula of the positive and negative signs is as follows: f When Φ is positive, take the negative sign; when Φ f When it is negative, take the positive sign.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Using this method, when the fiber optic gyroscope is powered on and started, during the startup period, the fiber optic gyroscope software will first enter the parameter adjustment mode, and apply a preset virtual rotation speed to the fiber optic gyroscope, so that the digital step wave is quickly reset, and the 2π voltage error information is calculated by collecting the difference in detector signals before and after the reset, and then the 2π voltage parameters are adjusted. Thereby, the rapid adjustment of the 2π voltage error is achieved. In this way, even in a low or high temperature environment, the 2π voltage parameters can be quickly adjusted during the startup phase to ensure the accuracy of the fiber optic gyroscope. The test results show that even in a low or high temperature environment, the present application can still calibrate the gyroscope's 2π voltage parameters within 2 seconds. Using this solution, the stability and rapidity of the gyroscope 2π voltage parameter calibration can be guaranteed.

[0029] 2. By analyzing the value of the adjustment amount when adjusting the 2π voltage parameter in S3, the 2π voltage parameter of the FOG can be analyzed. If the adjustment amount is less than the preset adjustment threshold, it means that the 2π voltage parameter is accurate at this time, that is, the FOG can work normally. Therefore, the 2π voltage parameter adjustment task is completed, and the FOG software is switched to the solution working mode to solve the rotation angular velocity of the FOG. In this way, the computing power of the FOG software is reasonably used so that it can play the corresponding effect in each stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0031] Figure 1 Flow chart of the method for adjusting 2π voltage parameters at full-temperature startup of a square wave modulated fiber optic gyroscope in an embodiment. DETAILED DESCRIPTION

[0032] The following is a further detailed description through specific implementation methods:

[0033] Example

[0034] In order to facilitate understanding of the principles of the present application, the closed-loop principle of the fiber optic gyroscope and the implementation principle of the digital step wave closed-loop feedback are first explained.

[0035] (I) Fiber Optic Gyroscope Closed Loop Principle

[0036] The optical power reaching the detector under square wave modulation can be expressed as follows:

[0037]

[0038] Where: P0 is the optical power reaching the detector when the fiber optic gyroscope is absolutely stationary (ΦS=0); ΦS is the phase difference caused by rotation.

[0039] Where Φm is:

[0040]

[0041] Where: Φ0 is the square wave modulation amplitude, τ is the transit time of the fiber ring (the time it takes for the light wave to transmit one circle in the fiber ring). After the above square wave modulation, the half-cycle of the positive and negative modulation can be sampled respectively to obtain the odd and even sampling values ​​of the fiber optic gyroscope:

[0042]

[0043] Subtracting the odd and even sampling values ​​gives:

[0044] ΔP=P - -P+ =P0 sinΦ0 sinΦ S …………………………(4)

[0045] Once the square wave modulation amplitude is determined, it is a constant value, so P0sinΦ0 is a constant term and can be represented by A. On the other hand, when ΦS is a small amount, sinΦS=ΦS, so the difference between odd and even samples is:

[0046] ΔP=AΦ S …………………………(5)

[0047] From equation (5), we can see that the difference between the odd and even sampling under square wave modulation is proportional to the phase difference caused by rotation, which can be used as the rotation angular rate output. At the same time, the total phase difference is servo-controlled to near zero through closed-loop control. The odd and even sampling values ​​after closed-loop control are:

[0048]

[0049] Where: Φf is the closed-loop feedback phase, which satisfies:

[0050] Φ f =-Φ S …………………………(7)

[0051] Formula (6) can also be expressed as:

[0052]

[0053] From the above, it can be seen that the role of the closed loop in the closed-loop fiber optic gyroscope is to servo-control the total phase difference to be near zero.

[0054] (II) Principle of digital step wave closed-loop feedback

[0055] Digital step wave closed-loop feedback is achieved by introducing a digital step wave signal on the electrodes of the Y-waveguide modulator and utilizing the piezoelectric effect of the crystal. The Y-waveguide is made of lithium niobate crystal. When a voltage is applied to the crystal, the light wave passing through it will produce a phase difference, which is proportional to the voltage.

[0056] In the optical path structure of the fiber optic gyroscope, the light wave emitted by the light source is modulated once by the modulation signal when passing through the Y waveguide, and is modulated again when returning to the Y waveguide after being transmitted through the fiber ring (at the same time, the subsequent light waves are modulated for the first time). The time interval between the two modulations is the light wave transmission time of the fiber ring, that is, the transit time. Since the transmission channels of the two light waves are exchanged during the two modulations, the phase difference actually introduced into the optical path is the difference between the two modulation phase differences (hereinafter referred to as the modulation phase), that is, the modulation phase is the first-order difference of the modulation voltage waveform with the fiber ring transit time as the step size. Therefore, in order to generate a constant feedback phase difference Φf, the feedback voltage signal must be continuously increased or decreased (increase corresponds to positive, decrease corresponds to negative), where the amplitude of increase or decrease corresponds to the feedback phase difference. According to this principle, the closed-loop control can be realized by applying the following feedback waveform on the Y waveguide:

[0057]

[0058] or:

[0059]

[0060] In the formula is the voltage value corresponding to the phase difference Φf, equation (9) represents the introduction of a positive phase difference (digital step wave rises), and equation (10) represents the introduction of a negative phase difference (digital step wave falls).

[0061] The above waveform is in the shape of a step, which is called a digital step wave. The digital step wave cannot rise or fall infinitely, and must be reset. The phase difference introduced by the reset voltage difference and the feedback phase difference introduced by the normal rise or fall of the digital step wave must differ by 2π or an integer multiple of 2π to avoid causing reset rotation error. That is, when resetting, the detector signal is:

[0062]

[0063] In the formula, Φ fw is the phase difference introduced during the digital step wave reset. Generally speaking (when the 2π voltage is accurate), it satisfies:

[0064] Φ fw =Φ f ±2π*k……………………(12)

[0065] Where k is a positive integer (generally 1 in practical applications). The positive and negative signs in the above formula are: when Φf is positive, take a negative sign; when Φf is negative, take a positive sign.

[0066] By comparing equations (8) and (11), it can be seen that when the 2π voltage parameter of the fiber optic gyroscope is accurate, that is, when equation (12) holds, it can be seen from the periodicity of the trigonometric function that no reset error will be introduced during the reset period. However, when the 2π voltage of the fiber optic gyroscope changes (especially when the temperature changes), that is, when equation (12) does not hold, a reset error will be introduced. Therefore, it is necessary to introduce servo adjustment technology to servo adjust the 2π voltage parameter.

[0067] In the square wave modulated fiber optic gyroscope, the servo adjustment technology is implemented as follows: the reset error information is obtained according to the difference of the detector signal before and after the reset, and the error information is adjusted by superimposing the 2π voltage parameter after calculation.

[0068] (III) Analysis of defects in 2π voltage parameter servo adjustment technology under square wave modulation

[0069] From the principle and implementation method of the 2π voltage parameter servo adjustment technology, it can be seen that the 2π voltage error information comes from the difference in detector signals before and after the digital step wave is reset. From the closed-loop principle, it can be seen that the reset frequency of the digital step wave is closely related to the rotation angular velocity. The higher the rotation speed, the higher the reset frequency. When the rotation speed is slow, there may be a situation where the 2π voltage error information cannot be obtained in time (it takes a long time). When the fiber optic gyroscope is stationary (the sensitive axis points to the east / west), the digital step wave will not be reset. At this time, the 2π voltage error information cannot be obtained, and even if the 2π voltage parameter is inaccurate, it cannot be adjusted. On the other hand, in order to comprehensively consider the full temperature range requirements of the fiber optic gyroscope, the initial value of the 2π voltage parameter is generally the accurate value at a given normal temperature. Then, when the fiber optic gyroscope is at a higher or lower ambient temperature, how to quickly complete the adjustment of the 2π voltage parameter during the startup phase to ensure the accuracy of the fiber optic gyroscope has become an urgent problem to be solved.

[0070] (IV) Square wave modulated fiber optic gyroscope full temperature start 2π voltage parameter adjustment method

[0071] To solve the above problems, Figure 1 As shown, the present invention provides a method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup, comprising the following steps:

[0072] S1, adjust the fiber optic gyroscope software to the parameter adjustment mode, and execute step S2. In specific implementation, when the fiber optic gyroscope is started, the fiber optic gyroscope software can be adjusted to enter the parameter adjustment mode to quickly adjust the parameters.

[0073] The fiber optic gyroscope software is the embedded control software of the fiber optic gyroscope. It should be noted that in order to implement the specific process of this method, it is necessary to perform coding expansion on the embedded control software of the fiber optic gyroscope so that the control software has both a parameter adjustment mode and a solution mode. The specific content of the coding expansion can be specifically set by those skilled in the art according to the specific content of this method, and will not be repeated here.

[0074] S2, applying a preset virtual rotation speed to the fiber optic gyroscope, and generating a digital step wave with the virtual rotation speed as the closed-loop feedback amount; wherein the virtual rotation speed is a preset fixed rotation speed value, and its value range can be set between 5 and 50 degrees per second. The specific value of the virtual rotation speed can be set by those skilled in the art according to the effect of software debugging, and will not be repeated here.

[0075] S3, collecting the detector signal difference before and after the digital step wave is reset, and calculating the 2π voltage error information, and then adjusting the 2π voltage parameter according to the 2π voltage error information;

[0076] Reset, that is, when the digital step wave exceeds the maximum or minimum value, the preset difference is increased or decreased, and the preset difference is collected. Based on this preset difference, it is analyzed whether there is a voltage error, so as to adjust the 2π voltage parameter.

[0077] S4, analyzing whether the adjustment amount is less than the preset adjustment threshold when the 2π voltage parameter is adjusted in S3, if so, go to S5, if not, return to S2;

[0078] S5, complete the parameter adjustment, and switch the fiber optic gyroscope software to the solution working mode. At this time, the parameter adjustment is completed, and the fiber optic gyroscope software can be switched to the solution working mode to work normally and solve the rotation angular velocity of the fiber optic gyroscope.

[0079] In actual applications, after the fiber optic gyro software is switched to the solution working mode, the odd-even sampling difference is used as the closed-loop feedback to generate a digital step wave. In the normal solution working mode of the fiber optic gyro, the digital step wave is generated by the odd-even sampling difference as the closed-loop feedback, so that the closed loop can be achieved. The closed-loop feedback is the step height of the digital step wave. Specifically, when the digital step wave is reset by using the odd-even sampling difference as the closed-loop feedback, the calculation formula for the odd-even sampling difference is:

[0080] ΔP=P - -P + =P0 sinΦ0 sinΦ S ;

[0081] Among them, ΔP represents the difference between odd and even sampling, P - Represents the sampling value within the half cycle of negative modulation, P +Represents the sampling value in the half cycle of positive modulation; Φ S represents the phase difference caused by rotation, P0 represents the absolute stillness of the fiber optic gyroscope (Φ S =0) is the optical power reaching the detector, and Φ0 is the square wave modulation amplitude.

[0082] The odd and even sampling values ​​are:

[0083] Among them, Φ f is the closed-loop feedback phase; the closed-loop feedback phase Φ f Satisfy the condition Φ f =-Φ S .

[0084] When the digital step wave is reset, the calculation formula of the detection signal is: In the formula, Among them, τ is the time it takes for a light wave to propagate one circle in the optical fiber ring;

[0085] Φ fw =Φ f ±2π*k; where k is a positive integer. Φ fw The calculation formula of the positive and negative signs is as follows: f When Φ is positive, take the negative sign; when Φ f When it is negative, take the positive sign.

[0086] Using this method, when the fiber optic gyroscope is powered on and started, during the startup period, the fiber optic gyroscope software will first enter the parameter adjustment mode, and apply a preset virtual speed to the fiber optic gyroscope, so that the digital step wave is quickly reset, and the 2π voltage error information is calculated by collecting the difference of the detector signal before and after the reset, and then the 2π voltage parameter is adjusted. Thereby realizing the rapid adjustment of the 2π voltage error. In this way, even in a low or high temperature environment, the 2π voltage parameter can be quickly adjusted in the startup phase to ensure the accuracy of the fiber optic gyroscope. By analyzing the value of the adjustment amount when the 2π voltage parameter is adjusted in S3, the 2π voltage parameter of the fiber optic gyroscope can be analyzed. If the adjustment amount is less than the preset adjustment threshold, it means that the 2π voltage parameter is accurate at this time, that is, the fiber optic gyroscope can work normally. Therefore, the 2π voltage parameter adjustment task is completed, and the fiber optic gyroscope software is switched to the solution working mode to solve the rotational angular velocity of the fiber optic gyroscope. In this way, the computing power of the fiber optic gyroscope software is reasonably utilized so that it can play a corresponding effect in each stage.

[0087] The test results show that even in a low or high temperature environment, the present application can still calibrate the gyroscope's 2π voltage parameters within 2 seconds. Using this solution, the stability and rapidity of the gyroscope's 2π voltage parameter calibration can be guaranteed.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup, characterized in that: The following steps are involved: S1, adjusting the fiber optic gyro software to a parameter adjustment mode, and executing step S2; S2, applying a preset virtual rotation speed to the fiber optic gyroscope, and generating a digital step wave with the virtual rotation speed as a closed-loop feedback quantity; S3, collecting the detector signal difference before and after the digital step wave is reset, and calculating the 2π voltage error information, and then adjusting the 2π voltage parameter according to the 2π voltage error information; S4, analyzing whether the adjustment amount is less than the preset adjustment threshold when the 2π voltage parameter is adjusted in S3, if so, go to S5, if not, return to S2; S5, completing the parameter adjustment, switching the fiber optic gyroscope software to the solution working mode, and solving the rotation angular velocity of the fiber optic gyroscope.

2. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 1, characterized in that: In S2, the virtual speed is a preset fixed speed value.

3. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 1, characterized in that: In S5, after the fiber optic gyro software is switched to the solution working mode, a digital step wave is generated as a closed-loop feedback quantity using the odd and even sampling difference.

4. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 3, characterized in that: In S5, when the digital step wave is reset using the odd-even sampling difference as the closed-loop feedback quantity, the calculation formula for the odd-even sampling difference is: ΔP=P - -P + =P0 sinΦ0sinΦ S ; Among them, ΔP represents the difference between odd and even sampling, P - Represents the sampling value within the half cycle of negative modulation, P + Represents the sampling value in the half cycle of positive modulation; Φ S represents the phase difference caused by rotation, P0 represents the phase difference caused by rotation, P0 represents the phase difference caused by rotation, S =0 is the optical power reaching the detector, Φ0 is the square wave modulation amplitude.

5. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 4, characterized in that: In S5, when the odd-even sampling difference is used as the closed-loop feedback quantity to reset the digital step wave, the odd-even sampling value is: Among them, Φ f is the closed-loop feedback phase.

6. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 5, characterized in that: Closed loop feedback phase Φ f Satisfy the condition Φ f =-Φ S .

7. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 6, characterized in that: When the digital step wave is reset, the calculation formula of the detection signal is: In the formula, Among them, τ is the time it takes for a light wave to propagate one circle in the optical fiber ring; Φ fw =Φ f ±2π*k; where k is a positive integer.

8. The method for adjusting 2π voltage parameters of a square wave modulated fiber optic gyroscope at full temperature startup according to claim 7, characterized in that: The Φ fw The method of choosing the positive and negative signs in the calculation formula is: when Φ f When it is positive, take the negative sign; when Φ f When it is negative, take the positive sign.

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