Resonant accelerometer digital measurement and control circuit based on orthogonal phase-locked loop

Abstract

The invention discloses a digital measurement and control circuit of a resonant accelerometer based on an orthogonal phase-locked loop. Comprising an FPGA core board, an ADC / DAC board card and a gauge outfit analog interface board, and the high-precision resonant accelerometer is driven and detected through digital closed-loop control. The implementation method comprises the following steps: after capacitance / voltage conversion, modulation and demodulation and filtering, a resonator displacement signal is acquired by a high-precision ADC and input into an FPGA, a driving signal generated by the FPGA through an orthogonal phase-locked loop and an automatic gain control module is output through a DAC, and the driving signal is applied to a resonator driving end after shunt superposition of a direct current quantity. The digital quadrature phase-locked loop is adopted to replace a traditional phase-locked loop, the contradiction between dynamic response and noise suppression is solved, and the digital quadrature phase-locked loop has the advantages of being high in phase control precision, wide in capture bandwidth, high in anti-interference performance and excellent in compatibility.

Description

Technical Field

[0001] The invention belongs to the field of measurement and control circuits of micro-electromechanical systems and inertial navigation devices, and relates to a resonant accelerometer digital measurement and control circuit based on an orthogonal phase-locked loop. Background Art

[0002] As the core sensitive component of the inertial system, the accelerometer can accurately measure the acceleration of the moving carrier by detecting the inertial force of the mass block. Its technological development level directly affects the system performance in the fields of navigation and positioning, aerospace, military equipment, intelligent transportation, industrial automation and consumer electronics. Among the many types of accelerometers, the resonant accelerometer avoids the error accumulation caused by the analog-to-digital conversion link of the traditional accelerometer due to its direct frequency output characteristics. It has shown significant advantages in measurement accuracy, anti-interference ability and long-term stability, and has become the research focus in the field of high-precision inertial measurement.

[0003] The measurement and control circuits of existing resonant accelerometers mainly adopt two technical solutions: self-oscillation and phase-locked loop drive. Among them, the self-oscillation drive system converts the detection displacement signal into an electrical signal through a capacitor / voltage conversion circuit, and multiplies it with the amplitude stable signal generated by the automatic controller after 90° phase shift processing to generate a drive signal. Although this analog circuit solution has the characteristics of simple structure, it is limited by the problem of phase control accuracy attenuation under high-frequency resonance conditions and is only applicable to resonators with high quality factor values. In addition, the inherent defects of the analog circuit make the system susceptible to temperature drift, electromagnetic interference and parasitic parameters, which seriously restricts its application reliability in harsh environments.

[0004] In contrast, phase-locked loop drive technology has shown stronger technical adaptability in the field of digital control. This solution uses a digital signal processor to achieve precise phase-frequency tracking, which can improve phase control accuracy and effectively expand the system's compatibility with low-quality factor resonators. However, the existing digital phase-locked loop solution still has an inherent contradiction between dynamic response speed and phase noise suppression. It may cause tracking loss when dealing with frequency and phase mutations, noise and high-order harmonic interference, and the capture bandwidth will also limit the range of the resonant accelerometer. This technical bottleneck needs to be broken through urgently. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a digital measurement and control circuit of a resonant accelerometer based on an orthogonal phase-locked loop.

[0006] Technical solution: To solve the above technical problems, the present invention adopts the following technical solution:

[0007] A digital measurement and control circuit for a resonant accelerometer based on an orthogonal phase-locked loop. Its hardware part includes an FPGA core board, an ADC / DAC board card, and a head analog interface board. The displacement at the detection end of the resonator is collected by the ADC board card after passing through a capacitance / voltage conversion circuit. The ADC board card inputs the digital signal into the FPGA core board through the bottom board. The FPGA core board processes the detection signal digitally, generates a driving signal after passing through an orthogonal phase-locked loop phase control loop and an automatic gain controller, and the driving signal is output by the DAC board card and input to the driving end of the resonator to realize the closed-loop measurement and control circuit of the resonant accelerometer. Among them, the orthogonal phase-locked loop consists of a phase detector, a loop filter, a numerically controlled oscillator, and an in-phase / quadrature loop. The phase detector extracts the phase difference between the input signal and the orthogonal reference signal through a multiplier, an integrator, and an adder.

[0008] Further, the capacitance / voltage conversion circuit includes: a modulation and demodulation circuit based on a ring diode for applying a high-frequency carrier to the common electrode of the resonator and demodulating the weak capacitance signal. A differential amplifier converts the demodulated differential signal into a single-ended signal, and a low-pass filter filters out the high-frequency carrier noise and then outputs it to the ADC board card.

[0009] Further, the phase detector of the orthogonal phase-locked loop includes: six multipliers, two integrators, and three adders, which are used to multiply and integrate the in-phase signal and the quadrature signal output by the numerically controlled oscillator with the error signal respectively to generate A s and A c signals; through the weighted summation of A s and Ac and , an output signal y(n) that is in the same frequency and in the same phase as the input signal is generated, and a 90° phase shift is performed on it.

[0010] Further, a rectifier circuit performs full-wave rectification on the input signal, and a low-pass filter extracts the amplitude component of the signal; a proportional-integral controller stabilizes the amplitude to the reference value V ref and then multiplies it with the phase-shifted quadrature signal to generate an AC driving signal V AC .

[0011] The specific method steps are as follows:

[0012] The displacement of the resonator is converted into a change in capacitance by the detection electrode and then converted into a voltage signal using a capacitance / voltage conversion circuit based on a ring diode. The weak capacitance signal is modulated by applying a high-frequency carrier to the common electrode of the resonator, and then demodulated using a ring diode. After capacitance / voltage conversion, differential amplification is performed, the differential signal is converted into a single-ended signal, and the noise brought by the high-frequency carrier is filtered out by a low-pass filter. Subsequently, ADC acquisition is carried out. After converting the acquired detection voltage signal into a digital signal, one path is sent to an orthogonal phase-locked loop for phase control. The phase detector of the orthogonal phase-locked loop consists of six multipliers, two integrators, and three adders. The in-phase and quadrature signals output by the numerically controlled oscillator are respectively multiplied by the A s and A c signals, and the results are added to generate an output signal y(n) that is in the same frequency, in the same phase, and has the same amplitude as the input signal. Subsequently, the output signal y(n) is phase-shifted by 90 degrees. The other path enters the automatic gain control module for amplitude control after rectification. In the automatic gain controller, the input signal is rectified, low-pass filtered, and then proportional-integral control is performed to stabilize the amplitude to V ref . After that, it is multiplied by the phase-shifted signal of y(n) to generate a stable AC drive signal V AC . V AC is divided into two paths. One path is inverted, and the other path remains unchanged. A DC quantity V DC is respectively added to form a drive voltage applied to the positive and negative electrodes of the drive electrode, forming a closed-loop control.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention realizes a closed-loop measurement and control circuit for a resonant accelerometer in a digital circuit, replaces the traditional phase-locked loop with an orthogonal phase-locked loop. The orthogonal phase-locked loop avoids the main structural defects of the traditional phase-locked loop and provides a drive signal equal to the phase change for the numerically controlled oscillator. The orthogonal phase-locked loop has superior performance compared to the traditional phase-locked loop, especially a wider locking and synchronization range, a faster convergence speed, and stronger noise interference suppression ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a hardware block diagram of a digital measurement and control circuit for a resonant accelerometer based on an orthogonal phase-locked loop.

[0015] Figure 2 is a block diagram of the digital control algorithm of the measurement and control circuit. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following further clarifies the present invention in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0017] As shown in the figure, the FPGA core board of the measurement and control circuit selects the FPGA chip EP4S40G2F40I2N, the ADC chip used in the ADC board is ADS6445, the DAC chip used in the DAC board is DAC5689. The ADC / DAC board is connected to the bottom board through the FMC interface, and the FPGA measurement and control core board is linked to the bottom board through the FEP interface. The bottom board also includes a power management module, a communication interface module, and a frequency measurement module.

[0018] The digital signal processing algorithm part of the measurement and control circuit includes an orthogonal phase-locked loop phase control loop and an automatic gain controller, which are used to control the phase and amplitude of the drive signal respectively. The orthogonal phase-locked loop consists of a phase detector, a loop filter, a numerically controlled oscillator, and in-phase and quadrature loops, and locks the input signal. The automatic gain controller is implemented through a proportional-integral controller.

[0019] The specific implementation steps are as follows:

[0020] Step 1, the displacement of the resonator is converted into a change in capacitance through the detection electrode, and then converted into a voltage signal using a capacitance / voltage conversion circuit based on a ring diode. The weak capacitance signal is modulated by applying a high-frequency carrier to the common electrode of the resonator, and then demodulated using a ring diode.

[0021] Step 2, the detected signal is differentially amplified after capacitance / voltage conversion, the differential signal is converted into a single-ended signal, and the noise brought by the high-frequency carrier is filtered out through a low-pass filter, and then ADC acquisition is performed.

[0022] Step 3, after the collected detection voltage signal is converted into a digital signal, it is divided into two paths. One path is sent to the orthogonal phase-locked loop for phase control. The phase detector of the orthogonal phase-locked loop consists of six multipliers, two integrators, and three adders. The in-phase and quadrature signals output by the numerically controlled oscillator are multiplied by the A s and A c signals generated by the phase detector respectively, and the results are added to generate an output signal with the same frequency, phase, and amplitude as the input signal Subsequently, the output signal y(n) is phase-shifted by 90 degrees.

[0023] Step 4, the other path enters the automatic gain control module for amplitude control after rectification. In the automatic gain controller, the input signal is rectified, low-pass filtered, and then proportional-integral controlled to stabilize the amplitude to V ref After that, it is multiplied by the phase-shifted signal of y(n) to generate a stable AC drive signal V AC .

[0024] Step 5, V AC is divided into two paths. One path is inverted, and the other path remains unchanged, and a DC quantity V DCA driving voltage is applied to the positive and negative electrodes of the driving electrode to form a closed-loop control.

[0025] Through the description of the above embodiments, the present invention realizes high-precision phase control through an orthogonal phase-locked loop. The orthogonal phase-locked loop can track the frequency and amplitude of the input signal, thereby generating a more accurate output signal. Its stability and locking time in response to phase, frequency, amplitude mutations, and noise interference are superior to those of traditional phase-locked loops. Moreover, it has a higher capture bandwidth and synchronization bandwidth.

[0026] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A digital measurement and control circuit for a resonant accelerometer based on an orthogonal phase-locked loop, characterized in that, It includes an FPGA core board, an ADC / DAC board, and a meter head analog interface board; the signal processing flow is as follows: the displacement signal at the resonator detection end is converted into an electrical signal through a capacitance / voltage conversion circuit, collected by the ADC board and input into the FPGA core board. The FPGA core board performs digital processing on the detection signal, including an orthogonal phase-locked loop phase control loop and automatic gain control. The generated drive signal is output to the resonator drive end through the DAC board to form a closed-loop measurement and control loop; among them, the orthogonal phase-locked loop consists of a phase detector, a loop filter, a numerically controlled oscillator, and an in-phase / quadrature loop. The phase detector realizes the extraction of the phase difference between the input signal and the orthogonal reference signal through a multiplier, an integrator, and an adder.

2. The digital measurement and control circuit of a resonant accelerometer based on an orthogonal phase-locked loop according to claim 1, characterized in that, The capacitance / voltage conversion circuit includes: a modulation and demodulation circuit based on a ring diode is used to apply a high-frequency carrier to the common electrode of the resonator and demodulate the weak capacitance signal. A differential amplifier converts the demodulated differential signal into a single-ended signal, and a low-pass filter filters out the high-frequency carrier noise and then outputs it to the ADC board.

3. The digital measurement and control circuit of a resonant accelerometer based on an orthogonal phase-locked loop according to claim 1, characterized in that The phase detector of the orthogonal phase-locked loop includes: six multipliers, two integrators and three adders, which are used to multiply and integrate the in-phase signal and the quadrature signal output by the numerically controlled oscillator with the error signal respectively to generate A s and A c signals; through A s and the weighted sum of Ac and generate the output signal y(n) with the same frequency and phase as the input signal, and perform a 90° phase shift on it.

4. A digital measurement and control circuit for a resonant accelerometer based on an orthogonal phase-locked loop according to claim 1, characterized in that, The automatic gain control module includes: a rectifying circuit that performs full-wave rectification on the input signal, and a low-pass filter that extracts the amplitude component of the signal; a proportional-integral controller that stabilizes the amplitude to a reference value V ref and multiplies it with the quadrature signal after phase shift to generate an AC drive signal V AC .

5. A digital measurement and control circuit for a resonant accelerometer based on an orthogonal phase-locked loop according to claim 1, characterized in that, The specific implementation steps of the circuit are as follows: Step 1, the displacement of the resonator is converted into a change in capacitance through the detection electrode and then converted into a voltage signal using a capacitance / voltage conversion circuit based on a ring diode. The weak capacitance signal is modulated by applying a high-frequency carrier to the common electrode of the resonator, and then demodulated using a ring diode. Step 2, after the detection signal is converted by the capacitance / voltage conversion, it is differentially amplified, the differential signal is converted into a single-ended signal, and the noise brought by the high-frequency carrier is filtered out through a low-pass filter, and then ADC acquisition is performed. Step 3: After converting the collected detection voltage signal into a digital signal, it is divided into two paths. One path is sent to a quadrature phase-locked loop for phase control. The phase detector of the quadrature phase-locked loop consists of six multipliers, two integrators, and three adders. The in-phase and quadrature signals output by the numerically controlled oscillator are respectively multiplied by the A s and A c signals, and the results are added to generate an output signal with the same frequency, the same phase, and the same amplitude as the input signal Subsequently, the output signal y(n) is phase-shifted by 90 degrees; Step 4: Another path enters the automatic gain control module for amplitude control after rectification. In the automatic gain controller, the input signal is rectified, low-pass filtered, and then proportional-integral control is performed to stabilize the amplitude at V ref and then multiplied by the signal after phase shifting of y(n) to generate a stable AC drive signal V AC ; Step 5, when dividing V AC into two paths, one path is inverted, the other path remains unchanged, and a DC voltage V DC is respectively added to form a driving voltage applied to the positive and negative electrodes of the driving electrode to form a closed-loop control.

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