Random dithering method suitable for dithering laser gyroscope

Abstract

The invention belongs to the technical field of avionics, and relates to a random jitter method suitable for jitter laser gyroscopes. Comprising the following steps: setting random jitter parameters including jitter offset frequency quantity, a random jitter base value, a noise adding digit and a proportional relation between jitter stress application and jitter stress reduction; performing digital filtering on the beat frequency signal to obtain a first signal; performing high-pass filtering on the first signal to obtain a second signal; performing low-pass filtering on the second signal to obtain a third signal; the third signal is used for adjusting the jittering stress application code value and the jittering stress reduction code value, and the offset frequency amount is kept unchanged; performing pseudo-random adjustment on the jitter force application period and the jitter force reduction period of the jitter driving signal through a pseudo-random algorithm; the method comprises the following steps of: tracking the resonant frequency of a gyroscope dithering wheel to obtain the actual dithering frequency of the dithering wheel at the moment of applying dithering stress application and dithering stress reduction; assigning the actual jitter frequency to the jitter driving signal; and changing the duty ratio of jitter force application and the duty ratio of jitter force reduction of the jitter driving signal through a pseudo-random algorithm.

Description

Technical Field

[0001] The invention belongs to the technical field of avionics, and in particular relates to a random jitter method suitable for jittering a laser gyroscope. Background Art

[0002] Inertial navigation system is an important part of modern avionics system. Laser gyro is an optical gyro based on Sagnac effect, which is mainly composed of optical system and circuit system. The circuit system is mainly a control circuit, which is used to control the error of laser gyro and improve its performance. Compared with electromechanical and optical angle sensitive elements, it has advantages such as wide dynamic range and rapid startup, and is widely used in aviation, aerospace, navigation and other fields.

[0003] The locking effect of the laser gyro is an important factor affecting its measurement sensitivity. Since its birth, the laser gyro has been committed to eliminating the influence of the locking effect. Mechanical dithering frequency deviation is the earliest applied laser gyro frequency deviation technology. Its principle is to use a small amplitude and high-speed mechanical dither device to force the laser gyro to rotate back and forth around the axis perpendicular to the plane of the resonant cavity loop, providing a fast alternating frequency deviation for the opposite traveling wave pairs in the resonant cavity, and finally eliminating this frequency difference in the signal processing process to obtain the angular rate signal.

[0004] The jitter laser gyro noise is to add noise during the jitter process, eliminate the dynamic lock area of ​​the jitter laser gyro, and improve the nonlinearity of the gyro. The jitter methods include periodic jitter and random jitter. Periodic jitter and random noise are simple and easy to implement, and the single gyro has high precision. However, after the three gyros with different frequencies are combined in the table body, the table body coupling is large, and the gyro performance is significantly reduced. The random jitter and random noise are complex to implement, and the single gyro precision is lower than that of periodic noise, but the coupling in the table body is small, and the gyro precision in the table body is consistent with that of the single gyro. Summary of the invention

[0005] Purpose of the invention: To provide a random dithering method suitable for a dithering laser gyroscope, replacing the conventional method based on periodic dithering plus random noise to eliminate the dynamic lock zone of the dithering laser gyroscope.

[0006] Technical solution:

[0007] A random jitter method for jittering a laser gyroscope comprises the following steps:

[0008] Step 1: Set the random jitter parameters, including the jitter frequency deviation, the base value of random jitter, the number of bits to be added for noise, and the ratio between jitter addition and jitter reduction.

[0009] Step 2: digitally filter the beat frequency signal to obtain a first signal;

[0010] Step 3: Perform high-pass filtering on the first signal to obtain a second signal;

[0011] Step 4: low-pass filter the second signal to obtain a third signal;

[0012] Step 5: Use the third signal to adjust the jitter force addition and jitter force reduction code values ​​to keep the frequency deviation unchanged;

[0013] Step 6: Pseudo-randomly adjust the jitter force-adding period and the jitter force-reducing period of the jitter driving signal by using a pseudo-random algorithm;

[0014] Step 7: Track the resonant frequency of the gyro shaking wheel to obtain the actual shaking frequency of the shaking wheel, and assign the actual shaking frequency to the shaking drive signal at the moment of applying shaking force and shaking force reduction;

[0015] Step 8: Change the duty ratio of the dithering force addition and the duty ratio of the dithering force reduction of the dithering driving signal through a pseudo-random algorithm.

[0016] Preferably, in step 3, the filtering method is a digital 6th-order high-pass IIR filter, and the filtering formula is:

[0017] y(n)=b_0x(n)+b_1x(n-1)+b_2x(n-2)+b_3x(n-3)+b_4x(n-4)+b_5x(n-5)-a_1x(n-1)-a_2x(n-2)-a_3x(n-3)-a_4x(n-4)-a_5x(n-5)-a_6x(n-6), wherein x(n) is the first signal, y(n) is the output second signal, and b_0, b_1, b_2, b_3, b_4, b_5 and a_1, a_2, a_3, a_4, a_5, a_6 are filter coefficients.

[0018] Preferably, in step 4, the filtering method is a digital 5th-order low-pass IIR filter, and the filtering formula is:

[0019] z(n)=c_0y(n)+c_1y(n-1)+c_2y(n-2)+c_3y(n-3)+c_4y(n-4)+d_1z(n-1)+d_2z(n-2)+d_3z(n-3)+d_4z(n-4)+d_5z(n-5), where y(n) is the second signal, z(n) is the third signal, c_0, c_1, c_2, c_3, c_4 and d_1, d_2, d_3, d_4, d_5 are filter coefficients.

[0020] Preferably, step 6 specifically includes:

[0021] The third signal is accumulated 128 times, and then the average value is calculated, and the average value is compared with the set frequency deviation value; when the average value is greater than the set frequency deviation value, the jitter force code value decreases by 10 per cycle during the force application process; otherwise, the jitter force code value increases by 10 per cycle;

[0022] When the average value is greater than the set frequency deviation, the jitter force reduction code value decreases by 10 per cycle during the force reduction process; otherwise, the jitter force reduction code value increases by 10 per cycle.

[0023] Preferably, step 6 specifically includes: changing the jitter force increase period and the jitter force reduction period of the jitter drive signal through a pseudo-random algorithm so that the jitter force increase period and the jitter force reduction period are both between a first value and a second value, wherein the first value is the base value of the random jitter, and the second value is the sum of the base value of the random jitter and the number of noise-added bits.

[0024] Preferably, step 6 specifically includes: the pseudo-random algorithm is implemented by a Mersenne twister algorithm.

[0025] Preferably, step 7 specifically includes: obtaining a real-time jitter frequency by sampling and filtering a PWM waveform generated by the jitter feedback signal.

[0026] Preferably, step 7 specifically includes: applying a shaking drive signal to the shaking wheel when the angular velocity is 0 in a gyro angular velocity feedback mode;

[0027] In the gyro angular position feedback mode, when the angular position is maximum, the shaking drive signal is applied to the shaking wheel.

[0028] Beneficial effects:

[0029] (1) The frequency deviation information obtained by digital filtering and demodulation of the beat frequency signal is more accurate, and no jitter feedback effective value conversion chip is required, thereby reducing costs;

[0030] (2) The frequency components generated by periodic noise are eliminated through a random jitter algorithm, thereby reducing the coupling degree of the jitter laser gyro in the platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solution implemented by the present invention, the following is a brief introduction to the drawings required for the description of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 The present invention is a flowchart of a random dithering method for dithering a laser gyroscope according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] The features of various aspects of the embodiments of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to fully understand the present invention. However, it is obvious to those skilled in the art that the present invention can also be implemented without these specific details. The following description of the embodiments is only for a better understanding of the present invention by illustrating examples of the present invention. The present invention is not limited to any specific settings and methods provided below, but covers all product structures, any improvements, replacements, etc. of the methods covered without departing from the spirit of the present invention. In the various drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity of the present invention.

[0035] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0036] For the jittered bias frequency laser gyro, random noise is generally injected into the periodic jitter to eliminate the dynamic lock area. The random jitter method of the present invention is that the jitter force period and the jitter force reduction period are random numbers, and the jitter force addition duty cycle and the jitter force reduction duty cycle are random numbers, which greatly reduces the coupling between the gyros in the platform.

[0037] Random dithering is used to combine dithering and noise into one, eliminating the harmonics generated by single gyroscope periodic dithering and random noise.

[0038] The present invention proposes a random jitter method suitable for a jitter laser gyroscope, which belongs to the field of avionics technology. The method includes realizing the randomness of jitter force addition and jitter force reduction through a digital signal processing chip (DSP) and an algorithm, thereby eliminating the dynamic lock area of ​​the gyroscope. The communication module of the DSP is used to write the parameters of the random jitter through online loading, and the gyroscope beat frequency signal is filtered through digital filtering to obtain information about the jitter, and then demodulated to obtain the jitter frequency deviation. The code values ​​of the jitter force addition and jitter force reduction are calculated by sliding filtering the frequency deviation. The values ​​of the jitter force addition cycle and the jitter force reduction cycle are obtained through a pseudo-random algorithm. Finally, the jitter code value is converted into a duty cycle of the jitter force addition and applied to the jitter wheel. The method realizes the randomness of the jitter by combining DSP and software algorithms, and has the advantages of low cost, high autonomous controllability, hardware saving, and high reliability.

[0039] Figure 1 The present invention is a flowchart of a random dithering method for dithering a laser gyroscope according to an embodiment of the present invention.

[0040] A random jitter method for jittering a laser gyroscope comprises the following steps:

[0041] Step 1: Initialize the random jitter parameters through the online loading function of the DSP, including the jitter frequency deviation, the base value of the random jitter, the number of bits to add noise, and the ratio between the jitter force increase and the jitter force reduction. The online writing method is to write the random jitter parameters into the DSP through the serial port assistant, RS422 bus and the serial communication module of the DSP. Online loading can realize the change of random jitter parameters and system debugging without dismantling the platform;

[0042] Step 2: Digitally filter the beat frequency signal through the filtering function of the orthogonal coding module of the DSP to remove the noise brought by the hardware circuit to obtain the first signal.

[0043] Step 3: Perform high-pass filtering on the first signal to obtain the second signal, and the filtering method is a digital 6th-order high-pass IIR filter. The filtering formula is:

[0044] y(n)=b_0x(n)+b_1x(n-1)+b_2x(n-2)+b_3x(n-3)+b_4x(n-4)+b_5x(n-5)-a_1x(n-1)-a_2x(n-2)-a_3x(n-3)-a_4x(n-4)-a_5x(n-5)-a_6x(n-6), wherein x(n) is the first signal, y(n) is the output second signal, b_0, b_1, b_2, b_3, b_4, b_5 and a_1, a_2, a_3, a_4, a_5, a_6 are filter coefficients, and the filter parameters are obtained through the filter design function of MATLAB software.

[0045] Step 4: Low-pass filter the second signal to obtain the third signal, and the filtering method is a digital 5th-order low-pass IIR filter. The filtering formula is:

[0046] z(n)=c_0y(n)+c_1y(n-1)+c_2y(n-2)+c_3y(n-3)+c_4y(n-4)+d_1z(n-1)+d_2z(n-2)+d_3z(n-3)+d_4z(n-4)+d_5z(n-5), wherein y(n) is the second signal, z(n) is the third signal, c_0, c_1, c_2, c_3, c_4 and d_1, d_2, d_3, d_4, d_5 are filter coefficients, and the filter parameters are obtained through the filter design function of MATLAB software.

[0047] Step 5: The third signal is accumulated 128 times, and then the average value is calculated, and the average value is compared with the set frequency deviation value; when the average value is greater than the set dither frequency deviation value, the dithering force code value decreases by 10 per cycle during the force application process; otherwise, the dithering force code value increases by 10 per cycle;

[0048] When the average value is greater than the set jitter frequency deviation, the jitter force reduction code value decreases by 10 per cycle during the force reduction process; otherwise, the jitter force reduction code value increases by 10 per cycle;

[0049] Keep the jitter frequency deviation unchanged;

[0050] Changing the code value can change the duty cycle of the dithering driving signal, that is, change the dithering force.

[0051] Step 6: Change the jitter force-adding cycle and the jitter force-reducing cycle of the jitter driving signal through a pseudo-random algorithm, so that the jitter force-adding cycle and the jitter force-reducing cycle are randomly changed between the base value of the random jitter and the base value of the random jitter plus the number of noise bits. Random jitter is achieved by changing the randomness of the force-adding and force-reducing cycles.

[0052] The pseudo-random algorithm is implemented by the Mersenne Twister algorithm.

[0053] Step 7: Track the resonant frequency of the gyro jitter wheel through the pulse capture module of the DSP module to obtain the actual jitter frequency of the jitter wheel (the real-time jitter frequency is obtained by sampling and filtering the PWM waveform generated by the jitter feedback signal.) Then assign the actual jitter frequency to the jitter drive signal.

[0054] In the gyro angular rate feedback mode, when the angular rate is 0, the shaking drive signal is applied to the shaking wheel;

[0055] In the gyro angular position feedback mode, when the angular position is maximum, a shaking drive signal is applied to the shaking wheel;

[0056] Step 8: Based on the values ​​of the dithering force-adding period and the dithering force-reducing period obtained by the pseudo-random algorithm, the pseudo-random algorithm implemented by the Mersenne rotation algorithm changes the dithering force-adding duty cycle and the dithering force-reducing duty cycle of the dithering driving signal.

[0057] The randomness of the jitter cycle and the jitter drive is realized at the same time, and then the jitter code value is assigned to the jitter drive signal to complete the random jitter control.

[0058] It should be noted that the above process operations can be combined and applied to different degrees. For the sake of simplicity, the implementation methods of various combinations are not described in detail. Those skilled in the art can flexibly adjust the order of the steps of the above method (or the position of the components of the product) according to actual conditions, or perform operations such as combination.

[0059] It should be noted that the implementation of the functional components shown in the above embodiments can be hardware, software or a combination of the two. When implemented in hardware, it can be an electronic circuit, an application specific integrated circuit (ASIC), a plug-in, a function card, etc. When implemented in software, it can be a program or code segment used to perform the required task. The program or code segment can be stored in a machine or readable medium, or it can be transmitted on a transmission medium or a communication link through a data signal carried in a carrier.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A random jitter method for jittering a laser gyroscope, characterized in that: The following steps are involved: Step 1: Set the random jitter parameters, including the jitter frequency deviation, the base value of random jitter, the number of bits to be added for noise, and the ratio between jitter addition and jitter reduction. Step 2: digitally filter the beat frequency signal to obtain a first signal; Step 3: Perform high-pass filtering on the first signal to obtain a second signal; Step 4: low-pass filter the second signal to obtain a third signal; Step 5: Use the third signal to adjust the jitter force addition and jitter force reduction code values ​​to keep the frequency deviation unchanged; Step 6: Pseudo-randomly adjust the jitter force-adding period and the jitter force-reducing period of the jitter driving signal by using a pseudo-random algorithm; Step 7: Track the resonant frequency of the gyro shaking wheel to obtain the actual shaking frequency of the shaking wheel at the moment of applying shaking force and shaking force reduction; Assigning the actual jitter frequency to the jitter drive signal; Step 8: Change the duty ratio of the dithering force addition and the duty ratio of the dithering force reduction of the dithering driving signal through a pseudo-random algorithm.

2. The method according to claim 1, characterized in that In step 3, the filtering method is a digital 6th-order high-pass IIR filter, and the filtering formula is: y(n)=b_0x(n)+b_1x(n-1)+b_2x(n-2)+b_3x(n-3)+b_4x(n-4)+b_5x(n-5)-a_1x(n-1)-a_2x(n-2)-a_3x(n-3)-a_4x(n-4)-a_5x(n-5)-a_6x(n-6), wherein x(n) is the first signal, y(n) is the output second signal, and b_0, b_1, b_2, b_3, b_4, b_5 and a_1, a_2, a_3, a_4, a_5, a_6 are filter coefficients.

3. The method according to claim 1, characterized in that In step 4, the filtering method is a digital 5th-order low-pass IIR filter, and the filtering formula is: z(n)=c_0y(n)+c_1y(n-1)+c_2y(n-2)+c_3y(n-3)+c_4y(n-4)+d_1z(n-1)+d_2z(n-2)+d_3z(n-3)+d_4z(n-4)+d_5z(n-5), where y(n) is the second signal, z(n) is the third signal, c_0, c_1, c_2, c_3, c_4 and d_1, d_2, d_3, d_4, d_5 are filter coefficients.

4. The method according to claim 1, characterized in that: Step 6 specifically includes: The third signal is accumulated 128 times, and then the average value is calculated, and the average value is compared with the set frequency deviation value; when the average value is greater than the set frequency deviation value, the jitter force code value decreases by 10 per cycle during the force application process; otherwise, the jitter force code value increases by 10 per cycle; When the average value is greater than the set frequency deviation, the jitter force reduction code value decreases by 10 per cycle during the force reduction process; otherwise, the jitter force reduction code value increases by 10 per cycle.

5. The method according to claim 1, characterized in that Step 6 specifically includes: changing the jitter force increase period and the jitter force reduction period of the jitter driving signal through a pseudo-random algorithm so that the jitter force increase period and the jitter force reduction period are both between a first value and a second value, wherein the first value is a base value of random jitter, and the second value is a sum of the base value of random jitter and the number of noise added bits.

6. The method according to claim 1, characterized in that Step 6 specifically includes: the pseudo-random algorithm is implemented by a Mersenne twister algorithm.

7. The method according to claim 1, characterized in that Step 7 specifically includes: obtaining a real-time jitter frequency by sampling and filtering the PWM waveform generated by the jitter feedback signal.

8. The method according to claim 1, characterized in that Step 7 specifically includes: applying a shaking drive signal to the shaking wheel when the angular velocity is 0 in a gyro angular velocity feedback mode; In the gyro angular position feedback mode, when the angular position is maximum, the shaking drive signal is applied to the shaking wheel.

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