A random jitter method for jittering laser gyroscopes

Abstract

This invention belongs to the field of avionics technology and relates to a random jitter method suitable for jittering laser gyroscopes. It includes setting random jitter parameters, including jitter frequency offset, random jitter base value, noise bit depth, and the ratio of jitter acceleration to jitter deceleration; digitally filtering the beat frequency signal to obtain a first signal; high-pass filtering the first signal to obtain a second signal; low-pass filtering the second signal to obtain a third signal; adjusting the jitter acceleration and deceleration code values ​​using the third signal while keeping the frequency offset constant; pseudo-randomly adjusting the jitter acceleration and deceleration periods of the jitter drive signal using a pseudo-random algorithm; tracking the resonant frequency of the gyroscope jitter wheel to obtain the actual jitter frequency of the jitter wheel, and applying the jitter acceleration and deceleration at the moment of application; assigning the actual jitter frequency to the jitter drive signal; and changing the duty cycle of the jitter acceleration and deceleration of the jitter drive signal using a pseudo-random algorithm.

Description

Technical Field

[0001] This invention belongs to the field of avionics technology, specifically relating to a random jitter method suitable for jittering laser gyroscopes. Background Technology

[0002] Inertial navigation systems are an important component of modern avionics systems. A laser gyroscope, an optical gyroscope based on the Sagnac effect, mainly consists of an optical system and a circuit system. The circuit system primarily controls the gyroscope's errors, improving its performance. Compared to electromechanical and optical angle-sensitive elements, it offers advantages such as a wider dynamic range and faster start-up, making it widely used in aviation, aerospace, and maritime fields.

[0003] The latch-up effect of laser gyroscopes is a significant factor affecting their measurement sensitivity. Since their inception, laser gyroscopes have been designed to eliminate the impact of the latch-up effect. Mechanical dithering is the earliest applied laser gyroscope frequency shifting technology. Its principle involves using a small-amplitude, high-speed mechanical dithering device to force the laser gyroscope to rotate back and forth around an axis perpendicular to the resonant cavity loop plane. This provides a rapidly alternating frequency shift for the opposing traveling waves within the resonant cavity. Finally, this frequency difference is eliminated during signal processing to obtain the angular rate signal.

[0004] Noise addition to jittered laser gyroscopes involves introducing noise during the jittering process to eliminate the dynamic locking region and improve the gyroscope's nonlinearity. Jittering methods include periodic jittering and random jittering. Periodic jittering and random noise addition are simple to implement and offer high single-gyroscope accuracy; however, when three gyroscopes of different frequencies are combined in a platform, the platform coupling becomes large, significantly degrading gyroscope performance. Random jittering and random noise addition are more complex to implement, resulting in lower single-gyroscope accuracy than periodic noise addition. However, they have lower coupling within the platform, and the accuracy of the gyroscope within the platform is consistent with that of a single gyroscope. Summary of the Invention

[0005] Purpose of the invention: To provide a random jitter method suitable for jittering laser gyroscopes, replacing the traditional method of dynamic region locking of jittering laser gyroscopes based on periodic jittering plus random noise reduction.

[0006] Technical solution:

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

[0008] Step 1: Set the random jitter parameters, including jitter frequency offset, random jitter base value, noise bit depth, and the ratio of jitter amplification to jitter reduction;

[0009] Step 2: Perform digital filtering on the beat frequency signal to obtain the first signal;

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

[0011] Step 4: Perform low-pass filtering on the second signal to obtain the third signal;

[0012] Step 5: Use the third signal to adjust the jitter amplification and jitter reduction code values ​​while keeping the frequency offset constant;

[0013] Step 6: Perform pseudo-random adjustment on the jitter acceleration period and jitter deceleration period of the jitter drive signal using a pseudo-random algorithm;

[0014] Step 7: Track the resonant frequency of the gyroscope's jitter wheel to obtain the actual jitter frequency of the jitter wheel. At the moment of applying jitter force and jitter force reduction, assign the actual jitter frequency to the jitter drive signal.

[0015] Step 8: Change the duty cycle of jitter acceleration and jitter deceleration of the jitter drive signal using 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), where x(n) is the first signal, y(n) is the second signal obtained from the output, 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 the coefficients of the filter.

[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, and c_0, c_1, c_2, c_3, c_4 and d_1, d_2, d_3, d_4, d_5 are the coefficients of the filter.

[0020] Preferably, step 6 specifically includes:

[0021] The third signal is accumulated 128 times, and then the average value is calculated. 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 offset, the jitter reduction code value decreases by 10 per cycle during the reduction process; conversely, when the average value is less than the set frequency offset, the jitter reduction code value increases by 10 per cycle.

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

[0024] Preferably, step 6 specifically includes: the pseudo-random algorithm is implemented using the Mason rotation algorithm.

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

[0026] Preferably, step 7 specifically includes: in the mode of gyroscope angular rate feedback, when the angular rate is 0, applying a jitter drive signal to the jitter wheel;

[0027] In the gyroscope angular position feedback mode, when the angular position is at its maximum, the jitter drive signal is applied to the jitter wheel.

[0028] Beneficial effects:

[0029] (1) The frequency offset information is more accurate by digitally filtering and demodulating the beat frequency signal, and no jitter feedback RMS conversion chip is needed, thus reducing costs;

[0030] (2) The frequency components generated by periodic noise are eliminated by random dithering algorithm, thereby reducing the coupling of the dithered laser gyroscope in the platform. Attached Figure Description

[0031] To more clearly illustrate the technical solutions implemented in this invention, the accompanying drawings used in the following description will be briefly introduced. Obviously, the drawings described below are merely some embodiments of this invention. Those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0032] Figure 1 This is a schematic flowchart of a random jittering method for a jittering laser gyroscope according to an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention. In the various drawings and the following description, well-known structures and techniques are not shown to avoid unnecessarily obscuring the invention.

[0035] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] For jitter-biased laser gyroscopes, dynamic region locking is typically eliminated by injecting random noise into the periodic jitter. The random jitter method of this invention uses random numbers for the jitter application period and jitter deceleration period, as well as random numbers for the jitter application duty cycle and jitter deceleration duty cycle, significantly reducing coupling between gyroscopes within the platform.

[0037] By employing random jitter, the jitter and noise are integrated into one, eliminating the harmonics generated by single-gyroscope periodic jitter and random noise.

[0038] This invention proposes a random jitter method suitable for jitter-prone laser gyroscopes, belonging to the field of avionics technology. The method involves implementing random jitter application and deceleration through a digital signal processing chip (DSP) and algorithms to eliminate dynamic lock-in zones in the gyroscope. The DSP's communication module writes random jitter parameters online, filters the gyroscope beat frequency signal using digital filtering to obtain jitter information, and then demodulates it to obtain the jitter offset. By applying a sliding filter to the offset, the code values ​​for jitter application and deceleration are calculated. The jitter application period and deceleration period are obtained using a pseudo-random algorithm. Finally, the jitter code values ​​are converted into the duty cycle of jitter application and applied to the jitter wheel. This method, combining DSP and software algorithms to achieve jitter randomness, offers advantages such as low cost, high autonomy and controllability, hardware savings, and high reliability.

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

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

[0041] Step 1: Initialize and configure the random jitter parameters using the DSP's online loading function, including jitter frequency offset, base value of random jitter, noise bit depth, and the ratio of jitter amplification to jitter reduction. The online parameter writing method involves using a serial port assistant, an RS422 bus, and the DSP's serial communication module to write the random jitter parameters into the DSP's internal memory. Online loading allows for changing random jitter parameters and system debugging without disassembling the DSP.

[0042] Step 2: The beat frequency signal is digitally filtered by the orthogonal encoding module of the DSP to remove noise from the hardware circuit and obtain the first signal.

[0043] Step 3: High-pass filter the first signal to obtain the second signal. 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), where 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 the filter coefficients, which are obtained through the filter design function of MATLAB software.

[0045] Step 4: Low-pass filter the second signal to obtain the third signal. 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), where y(n) is the second signal, z(n) is the third signal, and c_0, c_1, c_2, c_3, c_4 and d_1, d_2, d_3, d_4, d_5 are the coefficients of the filter. The filter parameters are obtained through the filter design function of MATLAB software.

[0047] Step 5: Accumulate the third signal 128 times, then calculate the average value and compare it with the set frequency offset value. If the average value is greater than the set jitter frequency offset value, the jitter acceleration code value decreases by 10 per cycle during the acceleration process; otherwise, the jitter acceleration code value increases by 10 per cycle.

[0048] When the average value is greater than the set jitter frequency offset, the jitter reduction code value decreases by 10 per cycle during the reduction process; conversely, when the average value is less than the set value, the jitter reduction code value increases by 10 per cycle.

[0049] Keep the jitter frequency offset constant;

[0050] Changing the code value can change the duty cycle of the jitter drive signal, which in turn changes the jitter force.

[0051] Step 6: Modify the jitter acceleration and deceleration periods of the jitter drive signal using a pseudo-random algorithm, ensuring that both periods vary randomly between the base value of random jitter and the base value plus the number of bits of noise. Random jitter is achieved by altering the randomness of the acceleration and deceleration periods.

[0052] The pseudo-random algorithm is implemented using the Mason rotation algorithm.

[0053] Step 7: Track the resonant frequency of the gyroscope's jitter wheel using 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 gyroscope angular rate feedback method, when the angular rate is 0, the jitter drive signal is applied to the jitter wheel;

[0055] In the gyroscope angular position feedback method, when the angular position is at its maximum, the jitter drive signal is applied to the jitter wheel;

[0056] Step 8: Based on the values ​​of the jitter acceleration period and jitter deceleration period obtained through the pseudo-random algorithm, the duty cycle of the jitter acceleration and the duty cycle of the jitter deceleration of the jitter drive signal are changed by the pseudo-random algorithm implemented by the Mason rotation algorithm.

[0057] Simultaneously, the jitter period and jitter drive are randomized, and then the jitter code value is assigned to the jitter drive signal to complete random jitter control.

[0058] It should be noted that the above process operations can be combined to varying degrees. For the sake of simplicity, the implementation methods of various combinations will not be elaborated further. Those skilled in the art can flexibly adjust or combine the order of the steps of the above method (or the position of the components of the product) according to the actual situation.

[0059] It should be noted that the functional components shown in the above embodiments can be implemented in hardware, software, or a combination of both. When implemented in hardware, they can be electronic circuits, application-specific integrated circuits (ASICs), plug-ins, function cards, etc. When implemented in software, they can be programs or code segments used to perform the required tasks. Programs or code segments can be stored in a machine or readable medium, or they can be transmitted over a transmission medium or communication link via data signals carried in a carrier wave.

[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 person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A random jittering method suitable for jittering laser gyroscopes, characterized in that, Includes the following steps: Step 1: Set the random jitter parameters, including jitter frequency offset, random jitter base value, noise bit depth, and the ratio of jitter amplification to jitter reduction; Step 2: Perform digital filtering on the beat frequency signal to obtain the first signal; Step 3: Perform high-pass filtering on the first signal to obtain the second signal; Step 4: Perform low-pass filtering on the second signal to obtain the third signal; Step 5: Use the third signal to adjust the jitter amplification and jitter reduction code values ​​while keeping the frequency offset constant; Step 6: The jitter acceleration period and jitter deceleration period of the jitter drive signal are pseudo-randomly adjusted using a pseudo-random algorithm. Specifically, the third signal is accumulated 128 times, and the average value is calculated. The average value is then compared with the set frequency offset value. When the average value is greater than the set frequency offset value, the jitter acceleration code value decreases by 10 per cycle during acceleration; conversely, the jitter acceleration code value increases by 10 per cycle. When the average value is greater than the set frequency offset value, the jitter deceleration code value decreases by 10 per cycle during deceleration. Conversely, the jitter reduction code value increases by 10 per cycle; the jitter acceleration and jitter reduction cycles of the jitter drive signal are changed by a pseudo-random algorithm so that both the jitter acceleration and jitter reduction cycles are between the first and second values, where the first value is the base value of random jitter and the second value is the sum of the base value of random jitter and the number of bits added for noise; the pseudo-random algorithm is implemented using the Mason rotation algorithm; Step 7: Track the resonant frequency of the gyroscope's jitter wheel to obtain the actual jitter frequency of the jitter wheel. At the moment of applying jitter force and jitter force reduction, assign the actual jitter frequency to the jitter drive signal. Step 8: Change the duty cycle of jitter acceleration and jitter deceleration of the jitter drive signal using 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), where 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 the coefficients of the filter.

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, and c_0, c_1, c_2, c_3, c_4 and d_1, d_2, d_3, d_4, d_5 are the coefficients of the filter.

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

5. The method according to claim 1, characterized in that, Step 7 specifically includes: in the gyroscope angular rate feedback mode, when the angular rate is 0, applying the jitter drive signal to the jitter wheel; In the gyroscope angular position feedback mode, when the angular position is at its maximum, the jitter drive signal is applied to the jitter wheel.

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