A small frequency difference MEMS gyroscope detection phase shift suppression system

Abstract

The application discloses a small frequency difference MEMS gyroscope detection phase shift suppression system, which is composed of a MEMS gyroscope, a driving loop, an angular velocity demodulation module and a parametric suppression loop. The application focuses on applying a parametric suppression signal to the detection resonator, electrostatically correcting the amplitude-phase frequency response, suppressing the detection phase shift under the small frequency difference mode, and improving the impact resistance. The detection resonator is embedded in the parametric suppression loop to generate stable amplitude self-excitation oscillation. A band-pass phase shifter is used to generate a parametric suppression signal twice the detection frequency from the detection amplitude multiplier. After the phase is shifted by 90 degrees to meet the parametric suppression phase condition, the parametric suppression signal acts on the parametric suppression electrode. Without losing the mechanical sensitivity of the MEMS gyroscope, the detection phase shift and the resonance peak amplitude at the detection natural frequency are suppressed, and the impact resistance is improved.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems and microinertial measurement technology, and in particular, a phase shift suppression system for small frequency difference MEMS gyroscope detection. Background Technology

[0002] MEMS gyroscopes are angular velocity sensors based on the Coriolis principle and fabricated using MEMS technology. They are characterized by their small size, light weight, low cost, low power consumption, and mass production capability, and have found wide application in consumer electronics, smart cities, industrial control, aerospace, and other fields. The market potential for MEMS gyroscopes with zero-bias stability of 0.1–1° / h is enormous. Reducing the frequency difference is an effective means to improve mechanical sensitivity, but at small frequency differences, the phase shift of the detection resonator is not ideal, leading to quadrature leakage, deteriorating zero-position noise, and limiting the improvement of MEMS gyroscope accuracy.

[0003] Due to limitations in manufacturing processes, MEMS gyroscopes suffer from machining errors such as irregular comb teeth and asymmetrical support beams. These errors generate orthogonal coupling errors, which are 90° out of phase with the useful signal and can reach speeds of 10–1000° / s. Furthermore, they are easily affected by ambient temperature. Currently, the measurement range of MEMS gyroscopes is approximately ±400° / s. The presence of orthogonal coupling errors severely impacts the gyroscope's range and zero-point output, necessitating effective correction methods. Phase-sensitive demodulation is a common method for suppressing orthogonal errors. It utilizes the 90° phase relationship between the orthogonal error and the useful signal to filter out orthogonal signals, but requires maintaining a strict phase relationship between the driving and detection modes. In mode-separated MEMS gyroscopes, at a 100Hz frequency difference, the driving and detection modes may exhibit a phase error of approximately 0.5°, resulting in orthogonal residuals in the zero-point signal reaching the dps level. Simultaneously, its sensitivity to temperature changes worsens the zero-point noise, affecting the gyroscope's accuracy. In addition, methods such as force feedback correction and orthogonal coupling stiffness correction are commonly used orthogonal correction techniques, which effectively offset orthogonal errors through correction electrodes and auxiliary closed-loop circuits. However, these methods are complex, consume high power, and generate significant noise interference, which limits further improvements in the accuracy of MEMS gyroscopes. Therefore, a simple and efficient phase shift suppression technique for small frequency difference MEMS gyroscopes is needed, which is of great significance for reducing orthogonal residuals and improving the accuracy of MEMS gyroscopes.

[0004] Increasing the detection Q value can suppress detection phase shift, but when the detection Q value of a MEMS gyroscope reaches tens of thousands, external shock inputs can cause resonance in the detection axis. This resonance is difficult to suppress by circuit filters in small frequency difference modes, and the recovery time can exceed 1 second, significantly impacting the normal operation of the MEMS gyroscope. Therefore, a technique is needed to reduce the detection Q value of a MEMS gyroscope to improve its shock resistance, while simultaneously ensuring that the detection phase shift is not increased to maintain the low quadrature leakage characteristics of the MEMS gyroscope. Summary of the Invention

[0005] The purpose of this invention is to provide a small frequency difference MEMS gyroscope detection phase shift suppression system. By applying a parametric suppression signal to the detection resonator, electrostatic correction is performed on its amplitude and phase frequency response, thereby suppressing the detection phase shift in the small frequency difference mode and improving its shock resistance characteristics.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] A small-frequency-difference MEMS gyroscope detection phase shift suppression system includes:

[0008] The drive loop is used to convert a pair of differential drive displacement current signals output by the MEMS gyroscope into a first voltage signal V. DS This generates a driving signal that acts on the driving comb teeth, ensuring that the MEMS gyroscope's driving mode maintains its operating frequency at the driving frequency ω. d The steady-amplitude oscillation motion;

[0009] The parametric suppression loop is used to generate a parametric suppression signal that acts on the parametric suppression comb teeth;

[0010] The detection resonant loop embedded in the parametric suppression loop is used to convert a pair of differential displacement current signals output by the MEMS gyroscope into a second voltage signal V. S It generates a detection drive signal to maintain the MEMS gyroscope's detection mode at the detection frequency ω. s The steady-amplitude oscillation motion;

[0011] The angular velocity demodulation module is used to extract the MEMS gyroscope input angular velocity information from the detection mode;

[0012] The significant advantages of this invention compared to existing technologies are:

[0013] (1) To address the problem of unsatisfactory phase shift detection in small frequency difference MEMS gyroscopes, a suppression signal twice the detection frequency is applied to the detection mode of the MEMS gyroscope, making the detection phase response curve maintain a longer interval of 0° before the detection frequency, thus widening the frequency range of 0° phase shift detection of the MEMS gyroscope. This suppresses the detection phase shift without affecting the original angular velocity detection function of the MEMS gyroscope.

[0014] (2) While performing phase shift correction, it has the additional effect of suppressing the detection resonance peak, and does not affect the amplitude response of the detection mode at the driving frequency, thus achieving the effect of reducing the detection Q value and improving the shock resistance of the MEMS gyroscope.

[0015] (3) Regarding the generation of the parametric suppression signal, the voltage-controlled oscillator and phase synchronization stage are omitted. The parametric suppression signal is generated directly from the detection resonant loop, which is simple to operate and easy to implement.

[0016] (4) No ADC or DAC is required, the method is simple and easy to implement. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a phase shift suppression system for a small frequency difference MEMS gyroscope.

[0018] Figure 2 This is a schematic diagram of the interface circuit in this invention;

[0019] Figure 3 This is a structural diagram of an example of a MEMS gyroscope used.

[0020] Figure 4 The graph shows the relationship between the suppression signal phase and the detection amplitude response gain.

[0021] Figure 5 This is a graph showing the relationship between the detection amplitude response gain and frequency difference for an example of a MEMS gyroscope.

[0022] Figure 6 This is a graph showing the relationship between the detected phase shift and frequency difference in a MEMS gyroscope example. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] The MEMS gyroscope 2 of this invention comprises a drive detection comb 2A, a mass block 2B, a detection drive comb 2C, a detection comb 2D, a parametric suppression comb 2E, and a drive comb 2F; the drive detection comb 2A is used to output a pair of differential drive displacement current signals i from the MEMS gyroscope. ds ±; The potential of mass block 2B is determined by an externally input DC bias voltage V. M Decision; the detection drive comb 2C is used to receive the external input detection mode drive voltage signal V. SD This causes the detection mode of the MEMS gyroscope to generate motion; the 2D detection comb teeth are used to output a pair of differential detection displacement current signals i from the MEMS gyroscope. s ±; The parametric suppression comb 2E is a variable-pitch comb structure used to receive the second harmonic parametric suppression signal V generated by the parametric suppression loop. P After modulation with the detection displacement, a parametric suppression effect is achieved, thus suppressing the detection phase shift; the drive comb 2F is used to receive the externally input drive voltage signal V. D ± causes the driving mode of the MEMS gyroscope to generate motion.

[0025] Combination Figure 1 The present invention discloses a phase shift suppression system for a small frequency difference MEMS gyroscope, which consists of a drive loop 1, an angular velocity demodulation module 3, and a parametric suppression loop 4.

[0026] The drive loop 1 consists of a drive interface circuit 1A and an amplitude control circuit 1B; the drive interface circuit 1A is used to drive the MEMS gyroscope 2 to detect a pair of differential drive displacement current signals i. ds After being amplified to a voltage signal, the signal is differentially processed to output a single voltage signal V. DS Amplitude control circuit 1B is used to control V. DS The signal amplitude is maintained at a specific value and undergoes a 90° phase shift to satisfy the phase condition of the self-excited oscillation loop, generating the driving signal V. D ± acts on the driving comb teeth 2F, enabling the MEMS gyroscope's driving mode to maintain a steady-amplitude oscillation motion, with its operating frequency being the driving frequency ω. d .

[0027] The parametric suppression loop 4 consists of an embedded detection resonant loop 4A and a bandpass phase shifter 4B; the detection resonant loop 4A consists of a detection interface circuit 4Aa, a detection drive multiplier 4Ab, a detection amplitude multiplier 4Ac, a PI module 4Ad, and a low-pass filter 4Ae; the detection interface circuit 4Aa is used to convert a pair of differential detection displacement current signals i output by the MEMS gyroscope 2 into a single signal. s After being amplified to a voltage signal, it undergoes differential processing and a 90° phase shift to satisfy the phase condition of the self-excited oscillation loop, outputting a single voltage signal V. S The amplitude multiplier 4Ac is used to convert V S Signal self-multiplication; low-pass filter 4Ae is used to extract V. S Signal amplitude information; reference DC voltage V ref The input of the subtraction from the low-pass filter output is fed into the PI module 4Ad, whose output is the same as V. S The signal generates a detection drive signal V through the detection drive multiplier 4Ab. SD This is used to keep the operating frequency of the MEMS gyroscope 2 detection mode at the detection frequency ω. s The steady-amplitude oscillation motion is achieved by setting a reference DC voltage V. ref The resonant amplitude is made much larger than the detection amplitude generated by the input angular velocity; the filter gain of the bandpass phase shifter 4B is adjustable, which is used to generate a parametric suppression signal twice the detection frequency from the detection amplitude multiplier 4Ac. After the phase shift of 90° satisfies the parametric suppression phase condition, it acts on the parametric suppression comb 2E of the detection resonator.

[0028] The angular velocity demodulation module 3 consists of a low-pass filter 3A and a multiplier 3B; the multiplier 3B is used to convert V...S With V DS Multiplication; low-pass filter 3A is used to extract V S With V DS The DC component produced after multiplication, i.e. from V S The amplitude information of the driving frequency component is extracted to obtain the input angular velocity information of the MEMS gyroscope.

[0029] Combination Figure 2 The drive interface circuit 1A consists of a transimpedance amplifier 5 and a differential amplifier 6; the transimpedance amplifier 5 will input i ds The ± current signal is amplified into a voltage signal; differential amplifier 6 performs differential processing on the two voltage signals to suppress common-mode interference and outputs a single voltage signal V. DS .

[0030] The detection interface circuit 4Aa consists of a transimpedance amplifier 7, a differential amplifier 8, and a bandpass phase shifter 9; the transimpedance amplifier 7 converts the input i s The ± current signal is amplified into a voltage signal; differential amplifier 8 performs differential processing on the two voltage signals to suppress common-mode interference; bandpass phase shifter 9 is mainly used for 90° phase shift to meet the loop phase condition of self-excited oscillation. By using reasonable parameters, the phase shift at the operating frequency is made 90°, while further suppressing low-frequency interference signals, and outputting a voltage signal V. S .

[0031] Combination Figure 3 The MEMS resonator example used in this invention has a detection mode natural frequency of ω. s The detection quality is m s Damping is b s The stiffness is k s The DC potential difference of all comb teeth is V. M The detected driving voltage is V. SD =V sd cos(ωt), V sd To detect the amplitude of the driving voltage, ω is the frequency of the driving voltage, and t is time; the parametric suppression voltage is V. P =V p cos(2ωt+Φ), V p Let Φ be the amplitude of the parametric suppression voltage, and Φ be the phase of the parametric suppression voltage; define the upward displacement y as positive, then its equation of motion is:

[0032]

[0033] Among them, K p K is the incentive coefficient. sd To detect the driving coefficient, let the expression for the detected displacement be:

[0034] y = y i cos(ωt+θ i (2)

[0035] Among them, y i To detect the displacement amplitude, θ i To detect phase shift, the cosine square term is transformed into a fourth harmonic term, and then a product-to-sum transform is performed. After filtering out high-frequency components, the following can be obtained:

[0036]

[0037] For ease of analysis, record

[0038]

[0039] In the above formula, Q s To detect the initial quality factor, ω s To detect the modal natural frequency, the amplitude response and phase response are respectively...

[0040]

[0041] To eliminate the frequency difference Δf=(ω-ω s The amplitude response change caused by the ) / 2π reduction is assumed to be due to the existence of only DC voltage on the parametric suppression comb 2D. That is, if A and C remain constant and B = 0, then the amplitude response gain caused by the suppression voltage is:

[0042]

[0043] When ω=ω s At that time, the equivalent quality factor Q of the detection mode p for

[0044]

[0045] Combination Figure 4 The example of the MEMS gyroscope used in this invention has an amplitude response gain G. i The relationship between the phase Φ of the suppression voltage and the effect of parametric suppression can be achieved at 90°.

[0046] Combination Figure 5 As an example of the present invention, its amplitude response gain G i The relationship between frequency difference and its effect on parametric suppression occurs at Δf = 0, with an equivalent quality factor Q. p The smaller the value, the more significant the suppression effect on the detection resonance peak, with a maximum suppression of approximately 50%.

[0047] Combination Figure 6 As an example of the present invention, it detects phase shift θ i Relationship between frequency difference and equivalent quality factor Qp The smaller the value, the more drastic the changes in the detected phase shift near the detection frequency, and the longer the interval where the detected phase shift is 0° before the detection frequency, thus achieving the purpose of phase shift correction in MEMS gyroscopes.

Claims

1. A phase shift suppression system for a small frequency difference MEMS gyroscope, characterized in that, include: The drive loop is used to convert a pair of differential drive displacement current signals output by the MEMS gyroscope into a first voltage signal. V DS It generates a driving signal that acts on the driving comb teeth, causing the MEMS gyroscope's driving mode to maintain its operating frequency at the driving frequency. ω d The steady-amplitude oscillation motion; The parametric suppression loop is used to generate a parametric suppression signal that acts on the parametric suppression comb teeth; The detection resonant loop embedded in the parametric suppression loop is used to convert a pair of differential displacement current signals output by the MEMS gyroscope into a second voltage signal. V S It also generates a detection drive signal, causing the MEMS gyroscope's detection mode to maintain its operating frequency at the detection frequency. ω s The steady-amplitude oscillation motion; The angular velocity demodulation module is used to extract the MEMS gyroscope input angular velocity information from the detection mode; The parametric suppression loop includes: The detection interface circuit is used to detect a pair of differential displacement current signals output by the MEMS gyroscope. i s After being amplified into a voltage signal, the signal undergoes differential processing and a 90° phase shift to satisfy the phase condition of the self-excited oscillation loop, outputting a second voltage signal. V S ; The amplitude multiplier is used to detect the second voltage signal. V S Self-multiplication; A low-pass filter is used to extract the second voltage signal. V S Amplitude information; The PI module is used to subtract the output of the low-pass filter from the reference DC voltage; The detection driver multiplier is used to combine the PI module output with the second voltage signal. V S Multiplication generates detection drive signal V SD This is used to keep the operating frequency of the MEMS gyroscope's detection mode at the detection frequency. ω s The steady-amplitude oscillation motion; A bandpass phase shifter is used to generate a parametric suppression signal twice the detection frequency from the detection amplitude multiplier. After being phase-shifted by 90° to satisfy the parametric suppression phase condition, it acts on the parametric suppression comb teeth of the detection resonator. The angular velocity demodulation module includes: A multiplier is used to convert the second voltage signal. V S With the first voltage signal V DS Multiply; A low-pass filter is used to extract the second voltage signal. V S With the first voltage signal V DS The DC component generated after multiplication, i.e., from the second voltage signal V S The amplitude information of the driving frequency component is extracted to obtain the input angular velocity information of the MEMS gyroscope.

2. The small frequency difference MEMS gyroscope phase shift suppression system according to claim 1, characterized in that, The drive loop includes: The drive interface circuit is used to convert a pair of differential drive displacement current signals output by the MEMS gyroscope. i ds After being amplified to a voltage signal, differential processing is performed to output a first voltage signal. V DS ; Amplitude control circuit, used to control the first voltage signal V DS The amplitude is maintained at a specific value and a 90° phase shift is performed to meet the phase condition of the self-excited oscillation loop, generating a driving signal that acts on the driving comb teeth.

3. The small frequency difference MEMS gyroscope phase shift suppression system according to claim 2, characterized in that, The driving interface circuit includes: A transimpedance amplifier is used to amplify an input current signal into a voltage signal; A differential amplifier is used to differentially process two voltage signals, suppress common-mode interference, and output a first voltage signal. V DS .

4. The small frequency difference MEMS gyroscope phase shift suppression system according to claim 1, characterized in that, The detection interface circuit includes: A transimpedance amplifier is used to amplify an input current signal into a voltage signal; A differential amplifier is used to process two voltage signals differentially to suppress common-mode interference; A bandpass phase shifter is used for 90° phase shifting to meet the loop phase condition for self-excited oscillation, and outputs a second voltage signal. V S .

Images