Hemispherical resonator gyroscope high-precision frequency tracking circuit and method thereof

Abstract

The invention relates to a hemispherical resonator gyroscope high-precision frequency tracking circuit and a method thereof.The hemispherical resonator gyroscope high-precision frequency tracking circuit comprises an x-electrode signal tracking circuit, a y-electrode signal tracking circuit and an average summator, the x-electrode signal tracking circuit is used for receiving x-electrode signals and outputting x-electrode resonant frequency, and the y-electrode signal tracking circuit is used for receiving y-electrode resonant frequency; the y electrode signal tracking circuit is used for receiving a y electrode signal and outputting y electrode resonant frequency, and the averaging summator is used for increasing the frequency output signal-to-noise ratio after accumulating and averaging the x electrode resonant frequency and the y electrode resonant frequency. According to the invention, the four paths of AD simultaneously acquire signals on the electrodes, accumulate the output of the four paths of AD, change the frequency tracking control scheme, demodulate the resonant frequencies on the two paths of electrodes of the gyroscope respectively, eliminate the defect of poor frequency precision caused by phase errors, and improve the frequency tracking precision through the accumulative averaging of the two paths of frequency tracking loops.

Description

Technical Field

[0001] The present invention belongs to the technical field of hemispherical resonant gyroscopes, and in particular, to a high-precision frequency tracking circuit and method for a hemispherical resonant gyroscope. Background Technique

[0002] Resonant gyroscopes, as a type of solid wave gyroscope based on the Coriolis effect, include quartz hemispherical resonant gyroscopes, metal cylindrical resonant gyroscopes, nested ring gyroscopes, and micro-hemispherical gyroscopes, etc. The quartz hemispherical resonant gyroscope is a Coriolis vibration gyroscope without rotating parts. Compared with traditional mechanical gyroscopes, it has a simple structure. Its core working components are only a quartz resonator and an electrode base, and it works by relying on micro-amplitude vibration without mechanical wear, making it have the characteristics of low cost, high reliability, and long life, and also having advantages such as high precision, high resolution, and strong radiation resistance.

[0003] Therefore, hemispherical resonant gyroscopes have broad application prospects in marine inertial navigation systems, aviation inertial navigation systems, weapon inertial navigation systems, and space inertial navigation systems.

[0004] The basic control loop for the normal operation of a hemispherical resonant gyroscope includes: a frequency tracking loop, an amplitude control loop, and an orthogonal control loop. Among them, the signal of the frequency tracking loop is not only used to keep the main vibration mode vibrating at a constant amplitude at the resonant frequency point, but also used to complete the demodulation of the gyroscope output signal. Therefore, the tracking frequency stability performance and tracking accuracy determine the stability of the gyroscope main vibration mode and the linearity of the output scale factor. Improving the accuracy of the frequency tracking loop becomes crucial. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and propose a high-precision frequency tracking circuit and method for a hemispherical resonant gyroscope, which can maintain the stable operation of the power grid, can quickly and accurately give the optimal load transfer scheme, greatly improve the work efficiency of dispatchers, and ensure the safe and stable operation of the power grid.

[0006] The present invention solves its technical problems by adopting the following technical solutions:

[0007] A high-precision frequency tracking circuit for a hemispherical resonant gyroscope includes an x-electrode signal tracking circuit, a y-electrode signal tracking circuit, and an average summator. Among them, the x-electrode signal tracking circuit is used to receive the x-electrode signal and output the x-electrode resonant frequency, the y-electrode signal tracking circuit is used to receive the y-electrode signal and output the y-electrode resonant frequency, and the average summator is used to perform, after accumulating and averaging the x-electrode resonant frequency and the y-electrode resonant frequency, to improve the signal-to-noise ratio of the frequency output.

[0008] Moreover, the x - electrode signal tracking circuit and the y - electrode signal tracking circuit have the same structure. The x - electrode signal tracking circuit includes an ADC acquisition module, a phase - angle error detection module, a loop filter PI, and a DDS synthesizing sine signal VCO. Among them, the ADC acquisition module, the phase - angle error detection module, the loop filter PI, and the DDS synthesizing sine signal VCO are connected in sequence. The ADC acquisition module is used to convert the electrode signal into a digital signal u o (t). The phase - angle error detection module is used to compare the DDS - synthesized sine signal and the gyro - electrode digital signal u o (t), and obtain an error signal u d (t). The loop filter PI is used to convert the error signal u d (t) into a control signal u c (t). The DDS synthesizing sine signal VCO is used to change the frequency so that the output frequency of the DDS synthesizing sine signal VCO is equal to the resonance frequency on the gyro - electrode.

[0009] Moreover, the ADC acquisition module includes an analog signal amplifier, a four - channel ADC chip, and an FPGA. Among them, the input terminals of the analog signal amplifier are respectively connected to the x + electrode signal and the x - electrode signal. The output terminal of the analog signal amplifier is connected to the input terminal of the four - channel ADC chip. The output terminal of the four - channel ADC chip is connected to the input terminal of the FPGA. The input terminals of the four - channel ADC chip and the FPGA are connected to a 40 - MHz clock.

[0010] A working method of a high - precision frequency tracking circuit for a hemispherical resonator gyroscope includes the following steps:

[0011] Step 1: The x - electrode signal tracking circuit acquires the x - electrode signal, and the y - electrode signal tracking circuit acquires the y - electrode signal;

[0012] Step 2: The x - electrode signal tracking circuit acquires the x - electrode signal and outputs the x - electrode resonance frequency, and the y - electrode signal tracking circuit acquires the y - electrode signal and outputs the y - electrode resonance frequency;

[0013] Step 3: The averaging summator is used to perform an operation on the x - electrode resonance frequency and the y - electrode resonance frequency. After cumulative averaging, the signal - to - noise ratio of the frequency output is improved.

[0014] Moreover, Step 2 includes the following steps:

[0015] Step 2.1: The ADC acquisition module converts the electrode signal into a digital signal u o (t),

[0016] Step 2.2: The phase - angle error detection module compares the DDS - synthesized sine signal and the gyro - electrode digital signal u o (t), and obtains an error signal u d (t),

[0017] Step 2.3. The loop filter PI converts the error signal u d (t) into a control signal u c (t).

[0018] Step 2.4. The DDS synthesizes a sine signal. The VCO changes the frequency so that the output frequency of the DDS-synthesized sine signal VCO is equal to the resonant frequency on the gyro electrodes.

[0019] Moreover, the specific implementation method of the said Step 2.1 is as follows: The input of each ADC consists of a signal term V S and a noise term V N . The total output of the system is: Summing the four noise voltage sources can generate a total voltage V T . Due to the noise sources of the signals, they are uncorrelated with each other and do not directly superimpose; the value is the linear summation of the four signal voltages and the four noise voltages as:

[0020]

[0021] Since V S1 = V S2 = V S3 = V S4 , therefore, the effective value of the signal is quadrupled, while the RMS value of the converter noise is equal and only doubled, so the coefficient of the signal-to-noise ratio improvement is 2.

[0022] The advantages and positive effects of the present invention are:

[0023] 1. The present invention includes an x-electrode signal tracking circuit, a y-electrode signal tracking circuit, and an averaging summator. Among them, the x-electrode signal tracking circuit is used to receive the x-electrode signal and output the x-electrode resonant frequency, the y-electrode signal tracking circuit is used to receive the y-electrode signal and output the y-electrode resonant frequency, and the averaging summator is used to perform the x-electrode resonant frequency and the y-electrode resonant frequency. After cumulative averaging, the signal-to-noise ratio of the frequency output is improved. The present invention simultaneously collects the signals on the electrodes through four channels of AD, sums the outputs of the 4 channels of AD, and simultaneously changes the frequency tracking control scheme to separately demodulate the resonant frequencies on the two channels of electrodes of the gyro, eliminating the disadvantage of poor frequency accuracy caused by phase error. Through the cumulative averaging of the two-channel frequency tracking loops, the frequency tracking accuracy is improved.

[0024] 2. The present invention can improve the detection accuracy of the formation angle of the full-angle gyro, and improve the equivalent detection accuracy of the 10-bit AD to the equivalent accuracy of 11-bit. The signal-to-noise ratio of the detection signal is increased by 6 dB.

[0025] 3. The present invention uses a dual-channel frequency tracking loop to improve the frequency tracking accuracy by 3 dB. Finally, the overall scheme improves the frequency tracking accuracy of the resonant gyro by 9 dB, that is, the frequency tracking noise accuracy is improved by 1.5 times. Description of the Drawings

[0026] Figure 1 This is the resonance motion trajectory model of the present invention;

[0027] Figure 2 This is the classical resonance frequency control loop diagram;

[0028] Figure 3 This is the resonance gyroscope frequency control loop model diagram of the present invention;

[0029] Figure 4 This is the dual-channel frequency output structure diagram of the present invention;

[0030] Figure 5 This is the implementation block diagram of the four-channel AD acquisition circuit of the present invention. Detailed Implementation Manner

[0031] The present invention will be further described in detail below with reference to the drawings.

[0032] Obtain the original signal of the gyro electrode:

[0033] As Figure 1 shown, the motion trajectory of the resonator of the hemispherical resonator gyroscope is equivalent to a two-dimensional pendulum. At a constant external angular rate, the trajectory of its center of gravity is elliptical, as Figure 1 shown, where a is the semi-major axis of the ellipse (main wave amplitude), q is the semi-minor axis of the ellipse (orthogonal wave amplitude), θ is the rotation angle of the semi-major axis (standing wave precession angle), and φ' is the oscillator orbit phase.

[0034] In order to obtain the motion state of the resonator, resonator detection electrodes are respectively arranged in the x and y directions, and a phase-locked loop is used as an external reference signal generator to track the motion of the resonator. The motion equations of the resonator in the x and y directions are:

[0035]

[0036] where ω0 is the natural frequency of the resonator; is the initial phase of vibration, A d is the amplitude of the sine wave on the x electrode, Q d is the amplitude of the sine wave on the y electrode, is the phase of the sine wave on the x electrode, is the phase of the sine wave on the x electrode; the motion trajectory of the resonator of the hemispherical resonator gyroscope is obtained by detecting the amplitude and phase of the sine waves on different electrodes.

[0037] When orthogonal control and frequency control are applied to the gyroscope, the gyroscope signal can be simplified to:

[0038]

[0039] Frequency tracking signal:

[0040] The transfer function from the excitation signal to the vibration displacement at the 0-degree electrode axis of the hemispherical resonant gyroscope is as follows:

[0041]

[0042] In the formula, ω0 is the resonant frequency of the hemispherical resonant gyroscope; and Q is the quality factor of the hemispherical resonant gyroscope.

[0043] Gyroscope excitation signal:

[0044] f(t) = A sin ω d t. (4)

[0045] The gyroscope output signal is:

[0046]

[0047] According to Equation (3), the amplitude-frequency and phase-frequency functions of the transfer function can be obtained:

[0048]

[0049] According to Equations (6) and (7), when the frequency of the excitation signal is ω d = ω0, the phase shift of the response signal relative to the excitation signal is equal to 90°. That is, when the gyroscope operates in the resonant state, the phase of the gyroscope vibration signal lags behind the excitation signal by 90°, which is consistent with the frequency characteristics reflected in the figure. Based on this, a phase-locked loop control scheme based on the phase-frequency characteristic curve is proposed, as Figure 2 shown.

[0050] According to the phase-frequency characteristic curve of the gyroscope, when the frequency ω d of the excitation signal is different, the phase shift of the response signal is different.

[0051] Therefore, when the phase shift of the response signal is..., it indicates that the frequency of the excitation signal, and the gyroscope operates at the resonant frequency, and the frequency control loop has completed the target function. However, in the actual circuit, due to the existence of the parasitic characteristics of operational amplifiers and electronic devices, it will have a certain impact on the phase detection of the detection signal. At this time, the frequency tracking will deviate greatly. As shown in Equation 2, on the x and y electrodes, sinusoidal wave signals with equal frequencies appear respectively, and the frequency signal ω0 at this time is the natural frequency of the resonator.

[0052] For a full - angle mode hemispherical resonant gyroscope, its core is to accurately detect and control the standing - wave angle of the resonator to identify the external angular velocity or angle. The gyroscope frequency determines the accuracy of gyroscope detection and control. Based on the working principle of the hemispherical resonant gyroscope, this patent proposes a new circuit form that can obtain gyroscope frequency information with higher accuracy and use it as the basic signal for gyroscope control.

[0053] The construction idea of the present invention is as follows: The traditional frequency - tracking control loop is limited by the noise output of the charge amplifier, the parasitic parameters of components such as operational amplifiers, and the noise of the AD acquisition circuit, resulting in a decrease in frequency control accuracy. The present invention improves the signal - to - noise ratio of the gyroscope output signal through an innovative hardware architecture and an improved frequency - tracking control scheme.

[0054] A high - precision frequency - tracking circuit for a hemispherical resonant gyroscope, as Figure 4 shown, includes an x - electrode signal tracking circuit, a y - electrode signal tracking circuit, and an averaging summator. Among them, the x - electrode signal tracking circuit is used to receive the x - electrode signal and output the x - electrode resonant frequency, the y - electrode signal tracking circuit is used to receive the y - electrode signal and output the y - electrode resonant frequency, and the averaging summator is used to perform accumulation and averaging on the x - electrode resonant frequency and the y - electrode resonant frequency to improve the signal - to - noise ratio of the frequency output.

[0055] The x - electrode signal tracking circuit and the y - electrode signal tracking circuit have the same structure. As Figure 3 shown, the x - electrode signal tracking circuit includes an ADC acquisition module, a phase - angle error detection, a loop filter PI, and a DDS - synthesized sine - wave VCO. Among them, the ADC acquisition module, the phase - angle error detection, the loop filter PI, and the DDS - synthesized sine - wave VCO are connected in sequence. The ADC acquisition module is used to convert the electrode signal into a digital signal u o (t), the phase - angle error detection is used to compare the DDS - synthesized sine - wave and the gyro - electrode digital signal u o (t), and obtain an error signal u d (t). The loop filter PI is used to convert the error signal u d (t) into a control signal u c (t). The DDS - synthesized sine - wave VCO is used to change the frequency so that the output frequency of the DDS - synthesized sine - wave VCO is equal to the resonant frequency on the gyro - electrode.

[0056] As Figure 5As shown in the figure, the ADC acquisition module includes an analog signal amplifier, a four-channel ADC chip, and an FPGA. Among them, the input ends of the analog signal amplifier are respectively connected to the x+ electrode signal and the x- electrode signal, the output end of the analog signal amplifier is connected to the input end of the four-channel ADC chip, the output ends of the four-channel ADC chip are connected to the input end of the FPGA, and the input ends of the four-channel ADC chip and the FPGA are connected to a 40 MHz clock.

[0057] A working method of a high-precision frequency tracking circuit for a hemispherical resonator gyroscope includes the following steps:

[0058] Step 1: The x-electrode signal tracking circuit collects the x-electrode signal, and the y-electrode signal tracking circuit collects the y-electrode signal.

[0059] Step 2: The x-electrode signal tracking circuit collects the x-electrode signal and outputs the x-electrode resonance frequency, and the y-electrode signal tracking circuit collects the y-electrode signal and outputs the y-electrode resonance frequency.

[0060] Step 2.1: The ADC acquisition module converts the electrode signal into a digital signal u o (t).

[0061] Limited by the noise output of the charge amplifier and the noise of the ADC acquisition line, the frequency control accuracy decreases. To further improve the gyro frequency output accuracy, it is necessary to improve the signal-to-noise ratio of the ADC acquisition. Using a four-channel ADC chip to collect the same electrode differential signal can effectively improve the signal-to-noise ratio of the gyro electrode signal acquisition. The principle of the ADC acquisition module is as follows:

[0062] Assume that the input of each ADC consists of a signal term (V S ) and a noise term (V N ). The total output of the system is: The summation of the four noise voltage sources can generate a total voltage V T . Due to the noise sources of the signals, they are uncorrelated and do not directly superimpose. The value is the linear summation of the four signal voltages and the four noise voltages as follows:

[0063]

[0064] Since V S1 = V S2 = V S3 = V S4 , therefore, the effective value of the signal is quadrupled, while the converter noise - whose RMS value is equal - only doubles. Thus, the coefficient of the signal-to-noise ratio improvement is 2, that is, 6.02 dB. Therefore, the 6.02 dB (SNR increment) increased by summing four similar signals will bring the benefit of 1 bit of additional effective resolution.

[0065] Therefore, summing the outputs of the four ADCs can improve the signal-to-noise ratio (SNR) by 6 dB.

[0066] Step 2.2: Phase angle error detection. Compare the DDS synthesized sine signal and the gyro electrode digital signal u o (t), and obtain the error signal u d (t).

[0067] Step 2.3: The loop filter PI converts the error signal u d (t) into a control signal u c (t).

[0068] Step 2.4: The DDS synthesized sine signal VCO changes the frequency so that the output frequency of the DDS synthesized sine signal VCO is equal to the resonant frequency on the gyro electrode.

[0069] Step 3: The averaging summer is used to sum the x-electrode resonant frequency and the y-electrode resonant frequency. After cumulative averaging, the signal-to-noise ratio of the frequency output is improved.

[0070] According to the above-mentioned high-precision frequency tracking circuit and method for a hemispherical resonant gyro, after testing, the ADC acquisition module of the present invention can improve the signal-to-noise ratio (SNR) by 6 dB by summing the outputs of the four ADCs. At the same time, the averaging summer is used to sum the x-electrode resonant frequency and the y-electrode resonant frequency. After cumulative averaging, the signal-to-noise ratio of the frequency output can be improved by 3 dB. Therefore, the dual-channel frequency tracking loop and the four-ADC redundant acquisition architecture can effectively improve the frequency accuracy of the hemispherical resonant gyro by 9 dB.

[0071] The present invention can improve the detection accuracy of the formation angle of the full-angle gyro, and improve the 10-bit AD equivalent detection accuracy to an equivalent accuracy of 11 bits. The signal-to-noise ratio of the detection signal is increased by 6 dB.

[0072] The present invention uses a dual-channel frequency tracking loop to improve the frequency tracking accuracy by 3 dB. Finally, the overall scheme improves the frequency tracking accuracy of the resonant gyro by 9 dB, that is, the frequency tracking noise accuracy is increased by 1.5 times.

[0073] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific embodiments. Any other embodiments obtained by those skilled in the art according to the technical solutions of the present invention also belong to the scope of protection of the present invention.

Claims

1. A high-precision frequency tracking circuit for a hemispherical resonant gyroscope, characterized in that: The invention comprises an x-electrode signal tracking circuit, a y-electrode signal tracking circuit and an average summer, wherein the x-electrode signal tracking circuit is used to receive the x-electrode signal and output the x-electrode resonant frequency, the y-electrode signal tracking circuit is used to receive the y-electrode signal and output the y-electrode resonant frequency, and the average summer is used to accumulate and average the x-electrode resonant frequency and the y-electrode resonant frequency to improve the frequency output signal-to-noise ratio.

2. A high-precision frequency tracking circuit for a hemispherical resonant gyroscope according to claim 1, characterized in that: The x-electrode signal tracking circuit and the y-electrode signal tracking circuit have the same structure. The x-electrode signal tracking circuit includes an ADC acquisition module, a phase error detection, a loop filter PI and a DDS synthesized sinusoidal signal VCO. The ADC acquisition module, the phase error detection, the loop filter PI and the DDS synthesized sinusoidal signal VCO are connected in sequence. The ADC acquisition module is used to convert the electrode signal into a digital signal u o (t), phase angle error detection is used to compare the DDS synthesized sinusoidal signal and the gyro electrode digital signal u o (t), and get the error signal u d (t), the loop filter PI is used to convert the error signal u d (t) is converted into control signal u c (t), the DDS synthesized sinusoidal signal VCO is used to change the frequency so that the output frequency of the DDS synthesized sinusoidal signal VCO is equal to the resonant frequency on the gyro electrode.

3. The high-precision frequency tracking circuit of a hemispherical resonant gyroscope according to claim 1, characterized in that: The ADC acquisition module includes an analog signal amplifier, four ADC chips and FPGA, wherein the input end of the analog signal amplifier is respectively connected to the x+ electrode signal and the x- electrode signal, the output end of the analog signal amplifier is connected to the input end of the four ADC chips, the output end of the four ADC chips is connected to the input end of the FPGA, and the input ends of the four ADC chips and the FPGA are connected to a 40MHz clock.

4. A method for operating the high-precision frequency tracking circuit of a hemispherical resonator gyroscope according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, the x-electrode signal tracking circuit collects the x-electrode signal, and the y-electrode signal tracking circuit collects the y-electrode signal; Step 2, the x-electrode signal tracking circuit collects the x-electrode signal and outputs the x-electrode resonant frequency, and the y-electrode signal tracking circuit collects the y-electrode signal and outputs the y-electrode resonant frequency; Step 3: The average summer is used to accumulate and average the resonance frequency of the x-electrode and the resonance frequency of the y-electrode to improve the frequency output signal-to-noise ratio.

5. The working method of the high-precision frequency tracking circuit of a hemispherical resonant gyroscope according to claim 4, characterized in that: The step 2 comprises the following steps: Step 2.1, ADC acquisition module converts the electrode signal into digital signal u o (t), Step 2.2, phase angle error detection compares the DDS synthesized sinusoidal signal and the gyro electrode digital signal u o (t), and get the error signal u d (t), Step 2.3: The loop filter PI converts the error signal u d (t) is converted into control signal u c (t), Step 2.4: The DDS synthesized sinusoidal signal VCO changes its frequency so that the output frequency of the DDS synthesized sinusoidal signal VCO is equal to the resonant frequency on the gyro electrode.

6. A high-precision frequency tracking circuit and method for a hemispherical resonant gyroscope according to claim 5, characterized in that: The specific implementation method of step 2.1 is: the input of each ADC is composed of the signal term V S and the noise term V N The total output of the system is: The sum of the four noise voltage sources can produce a total voltage V T , due to the noise source of the signal, they are uncorrelated and not directly superimposed; the value is the linear sum of the four signal voltages and the four noise voltages: Since V S1 =V S2 =V S3 =V S4 , so the effective value of the signal is quadrupled, while the RMS value of the converter noise is the same and is only doubled, so the signal-to-noise ratio is improved by a factor of 2.

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