CN117367396A - Detection phase shift suppression system for small-frequency-difference MEMS gyroscope - Google Patents

Abstract

The invention 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 parameter suppression loop. The focus of the present invention is to apply a parametric suppression signal to the detection resonator to electrostatically correct its amplitude-phase-frequency response, suppress the detection phase shift in the small frequency difference mode, and improve its anti-shock characteristics. The detection resonant loop is embedded in the parametric suppression loop to cause the detection resonator to have steady-amplitude self-oscillation. A bandpass phase shifter is used to generate a parametric suppression signal twice the detection frequency from the detection amplitude multiplier, with a phase shift of 90 °After meeting the parametric suppression phase conditions, it acts on the parametric suppression electrode to suppress the detection phase shift and the resonance peak amplitude at the detection natural frequency without losing the mechanical sensitivity of the MEMS gyroscope, thereby improving its impact resistance.

Description

A small frequency difference MEMS gyroscope detection phase shift suppression system

Technical field

The invention belongs to the technical fields of microelectronic mechanical systems and microinertial measurement, and is particularly a small frequency difference MEMS gyroscope detection phase shift suppression system.

Background technique

MEMS gyroscope is an angular velocity sensor based on the Coriolis principle and processed using MEMS technology. It has the characteristics of small size, light weight, low cost, low power consumption, and can be mass produced. It is widely used in consumer electronics, smart cities, and industry. It has been widely used in control, aerospace and other fields, and the market prospect of MEMS gyroscopes with bias stability of 0.1~1°/h is huge. Reducing the frequency difference is an effective means to improve mechanical sensitivity. However, the phase shift of the detection resonator under small frequency differences is not ideal, leading to orthogonal leakage, worsening zero-position noise, and restricting the improvement of MEMS gyroscope accuracy.

MEMS gyroscopes are limited by the level of technology and have processing errors such as irregular comb teeth and asymmetric support beams. This results in an orthogonal coupling error that is 90° out of phase with the useful signal. It can reach 10-1000°/s and is easy to Affected by ambient temperature. Currently, the measuring range of MEMS gyroscopes is about ±400°/s. The existence of orthogonal coupling error seriously affects the measuring range and zero output of the gyroscope, and effective means must be taken to correct it. Phase-sensitive demodulation is a common method to suppress orthogonal errors. It uses the 90° phase relationship between the orthogonal error and the useful signal to filter out the orthogonal signal, but it needs to ensure the strict phase relationship between the driving mode and the detection mode. In a mode-separated MEMS gyroscope with a frequency difference of 100Hz, there may be a phase error of about 0.5° between the driving mode and the detection mode. The orthogonal residual amount in the zero signal reaches the dps level. At the same time, it is sensitive to temperature changes. Deteriorating the zero noise and affecting the accuracy of the gyroscope. In addition, methods such as force feedback correction method and orthogonal coupling stiffness correction method are commonly used orthogonal correction techniques, which effectively offset the orthogonal error through correction electrodes and auxiliary closed-loop circuits. However, its system complexity, high power consumption, and obvious noise interference restrict the further improvement of the accuracy of MEMS gyroscopes. Therefore, a simple and efficient small frequency difference MEMS gyroscope detection phase shift suppression technology is needed, which is of great significance for reducing orthogonal residuals and improving the accuracy of MEMS gyroscopes.

Increasing the detection Q value can suppress the detection phase shift. However, when the detection Q value of the MEMS gyroscope reaches tens of thousands, the external impact input will cause the detection axis to resonate, which is difficult to be suppressed by the circuit filter in the small frequency difference mode, and its recovery time It can reach more than 1s, which has a great impact on the normal use of MEMS gyroscopes. Therefore, a technology is needed to reduce the detection Q value of the MEMS gyroscope to improve its impact resistance; at the same time, it is necessary to ensure that the detection phase shift is not increased to ensure the low orthogonal leakage characteristics of the MEMS gyroscope.

Contents of the invention

The object of the present invention is to provide a detection phase shift suppression system for a small frequency difference MEMS gyroscope. By applying a parametric suppression signal to the detection resonator, electrostatic correction is performed on its amplitude-phase frequency response to suppress the detection phase shift in the small frequency difference mode. , and improve its impact resistance properties.

The technical solution to achieve the purpose of the present invention is:

A small frequency difference MEMS gyroscope detection phase shift suppression system, including:

The drive loop is used to convert a pair of differential drive displacement current signals output by the MEMS gyroscope into the first voltage signal V _DS , and generate a drive signal to act on the drive comb teeth, so that the MEMS gyroscope drive mode maintains the operating frequency as the drive Steady amplitude oscillatory motion with frequency ω _d ;

The parametric suppression loop is used to generate a parametric suppression signal to act on the parametric suppression comb teeth;

The detection resonant loop embedded in the parameter suppression loop is used to convert a pair of differential detection displacement current signals output by the MEMS gyroscope into the second voltage signal V _S and generate a detection drive signal to maintain the detection mode of the MEMS gyroscope. The working frequency is a steady-amplitude oscillation motion of the detection frequency ω _s ;

Angular velocity demodulation module, used to extract MEMS gyroscope input angular velocity information from the detection mode;

Compared with the prior art, the significant advantages of the present invention are:

(1) In order to solve the problem of unsatisfactory detection phase shift of small frequency difference MEMS gyroscope, by applying a suppression signal twice the detection frequency to the MEMS gyroscope detection mode, the detection phase response curve can maintain a 0° interval before the detection frequency. Long, it broadens the frequency range of the MEMS gyroscope's 0° detection phase shift, and suppresses the detection of phase shift without affecting the original angular velocity detection function of the MEMS gyroscope.

(2) While correcting the detection phase shift, it has the additional function of suppressing the detection resonance peak, and does not affect the amplitude response of the detection mode at the driving frequency, thereby reducing the detection Q value and improving the impact resistance of the MEMS gyroscope. Effect;

(3) Regarding how to generate the parametric suppression signal, the voltage controlled oscillator and phase synchronization links are omitted, and the parametric suppression signal is generated directly from the detection resonant loop, which is simple to operate and easy to implement;

(4) No ADC and DAC are required, the method is simple and easy to implement.

Description of the drawings

Figure 1 is a schematic structural diagram of a small frequency difference MEMS gyroscope detection phase shift suppression system;

Figure 2 is a schematic diagram of the interface circuit part of the present invention;

Figure 3 is an example structure diagram of a MEMS gyroscope used;

Figure 4 is a diagram showing the relationship between the phase of the suppression signal and the gain of the detection amplitude response;

Figure 5 is a graph showing the relationship between the detection amplitude response gain and the frequency difference of an example of a MEMS gyroscope;

Figure 6 is a graph showing the relationship between the detected phase shift and the frequency difference of an example of a MEMS gyroscope.

Detailed ways

The present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments.

The MEMS gyroscope 2 targeted by the present invention is composed of a driving detection comb 2A, a mass block 2B, a detection driving comb 2C, a detection comb 2D, a parameter suppression comb 2E, and a driving comb 2F; the driving detection comb 2A is used for Outputs a pair of differential drive displacement current signals i _ds ± of the MEMS gyroscope; the potential of the mass block 2B is determined by the DC bias voltage V _M input from the outside; the detection drive comb 2C is used to receive the detection mode drive voltage signal input from the outside V _SD , causing the detection mode of the MEMS gyroscope to move; the detection comb teeth 2D are used to output a pair of differential detection displacement current signals i _s ± of the MEMS gyroscope; the parametric suppression comb teeth 2E are variable-pitch comb teeth structures for It receives the double-frequency parameter suppression signal V _P generated by the parameter suppression loop, and modulates it with the detection displacement to achieve the parameter suppression effect and perform detection phase shift suppression; the driving comb 2F is used to receive the driving voltage signal V _D ± input from the outside, so that The drive modes of MEMS gyroscopes generate motion.

With reference to Figure 1, a small frequency difference MEMS gyroscope detection phase shift suppression system of the present invention is composed of a driving loop 1, an angular velocity demodulation module 3, and a parameter suppression loop 4.

The drive loop 1 is composed of a drive interface circuit 1A and an amplitude control circuit 1B; the drive interface circuit 1A is used to amplify a pair of differential drive displacement current signals i _ds ± of the MEMS gyroscope 2 to drive and detect the comb teeth into a voltage signal. Differential processing, outputs a voltage signal V _DS ; the amplitude control circuit 1B is used to control the amplitude of the V _DS signal to maintain a specific value, and performs a 90° phase shift to meet the phase conditions of the self-oscillation loop, and generates a drive signal V _D ± Acting on the driving comb tooth 2F, the MEMS gyroscope driving mode maintains a steady amplitude oscillation motion, and its operating frequency is the driving frequency ω _d .

The parameter suppression loop 4 is composed of an embedded detection resonant loop 4A and a bandpass phase shifter 4B; the detection resonant loop 4A is composed of a detection interface circuit 4Aa, a detection drive multiplier 4Ab, and a detection amplitude multiplier. It is composed of a device 4Ac, a PI module 4Ad, and a low-pass filter 4Ae; the detection interface circuit 4Aa is used to amplify a pair of differential detection displacement current signals i _s ± output by the MEMS gyroscope 2 into a voltage signal, perform differential processing, and perform 90° The phase is shifted to meet the phase condition of the self-oscillation loop and a voltage signal V _S is output; the detection amplitude multiplier 4Ac is used to self-multiply the V _S signal; the low-pass filter 4Ae is used to extract the amplitude information of the V _S signal; The reference DC voltage V _ref is subtracted from the output of the low-pass filter and then input into the PI module 4Ad. Its output and the V _S signal are passed through the detection drive multiplier 4Ab to generate a detection drive signal V _SD , which is used to maintain the detection mode of the MEMS gyroscope 2 The working frequency is a steady-amplitude oscillatory motion at the detection frequency ω _s . By setting the reference DC voltage V _ref , the resonance amplitude is 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 detect the amplitude from the detection amplitude. The multiplier 4Ac generates a parametric suppression signal twice the detection frequency, shifts the phase by 90° to satisfy the parametric suppression phase condition, and then acts on the parametric suppression comb 2E of the detection resonator.

The angular velocity demodulation module 3 is composed of a low-pass filter 3A and a multiplier 3B; the multiplier 3B is used to multiply V _S and V _DS ; the low-pass filter 3A is used to extract the multiplied value of V _S and V _DS The generated DC component, that is, the amplitude information of the driving frequency component is extracted from V _S to achieve the purpose of obtaining the input angular velocity information of the MEMS gyroscope.

With reference to Figure 2, the driving interface circuit 1A is composed of a transistor amplifier 5 and a differential amplifier 6; the transimpedance amplifier 5 amplifies the input i _ds ± current signal into a voltage signal; the differential amplifier 6 performs differential processing on the two voltage signals. Suppress common mode interference and output a voltage signal V _DS .

The detection interface circuit 4Aa is composed of a transgroup amplifier 7, a differential amplifier 8, and a bandpass phase shifter 9; the transimpedance amplifier 7 amplifies the input i _s ± current signal into a voltage signal; the differential amplifier 8 conducts the two voltage signals. Differential processing to suppress common mode interference; the bandpass phase shifter 9 is mainly used for 90° phase shift to meet the loop phase conditions of self-oscillation. Through reasonable parameters, the phase shift at the operating frequency is 90°, while further Suppress low-frequency interference signals and output a voltage signal V _S .

Combined with Figure 3, an example of the MEMS resonator used in the present invention has a detection mode natural frequency of ω _s , detection mass of m _s , damping of b _s , stiffness of _ks , and the DC potential difference of all comb teeth is V _M . The driving voltage is V _SD =V _sd cos(ωt), V _sd is the detected driving voltage amplitude, ω is the detected driving voltage frequency, t is the time; the parameter suppression voltage is V _P =V _p cos(2ωt+Φ), V _p is the amplitude of the parametric suppression voltage, Φ is the phase of the parametric suppression voltage; define the upward movement of the detected displacement y as positive, then its motion equation is:

Among them, K _p is the excitation coefficient, and K _sd is the detection drive coefficient. Let the detection displacement expression be

y＝y _i cos(ωt+θ _i ) (2)

Among them, y _i is the detected displacement amplitude, and θ _i is the detected phase shift. Convert the cosine square term into a quadruple frequency term, perform product and difference transformation, and filter out the high-frequency components to obtain

For the convenience of analysis, remember

In the above formula, Q _s is the detection initial quality factor, and ω _s is the detection mode natural frequency. Then the amplitude response and phase response are respectively

In order to eliminate the amplitude response changes caused by the reduction of frequency difference Δf = (ω-ω _s )/2π, it is considered that only DC voltage exists on the parametric suppression comb tooth 2D That is, A and C remain unchanged, B=0, then the amplitude response gain caused by the suppression voltage is

When ω=ω _s , the equivalent quality factor Q _p of the detection mode is

Figure 4 shows an example of a MEMS gyroscope used in the present invention. Its amplitude response gain G _i changes with the suppression voltage phase Φ, which can achieve a parametric suppression effect at 90°.

Figure 5 is an example of the present invention. The amplitude response gain G _i changes with the frequency difference. It has the effect of parametric suppression at Δf=0. The smaller the equivalent quality factor Q _p , the better the suppression of the detection resonance peak. The more obvious the effect, the maximum inhibition can be about 50%.

Figure 6 is an example of the present invention, which shows the relationship between the detection phase shift θ _i and the frequency difference. The smaller the equivalent quality factor Q _{p is} , the more drastic the detection phase shift changes near the detection frequency. The detection phase shift is detected before the detection frequency. The interval shifted to 0° is longer, achieving the purpose of phase shift correction for MEMS gyroscope detection.

Claims (6)

1. A small frequency difference MEMS gyroscope detection phase shift suppression system, comprising:

a driving loop for converting a pair of differential driving displacement current signals output by the MEMS gyroscope into a first voltage signal V _DS And generates a driving signal to act on the driving comb teeth to maintain the working frequency of the MEMS gyroscope driving mode to be the driving frequency omega _d Is fixed in amplitude and oscillating;

the parameter suppression loop is used for generating a parameter suppression signal to act on the parameter suppression comb teeth;

a detection resonance loop embedded in the parameter suppression loop for electrically detecting a pair of differential detection displacements outputted by the MEMS gyroscopeConversion of the flow signal into a second voltage signal V _S And generating a detection driving signal to maintain the working frequency of the MEMS gyroscope detection mode to be the detection frequency omega _s Is fixed in amplitude and oscillating;

and the angular velocity demodulation module is used for extracting the input angular velocity information of the MEMS gyroscope from the detection mode.

2. The small frequency differential MEMS gyroscope detection phase shift suppression system of claim 1, wherein the drive loop comprises:

a drive interface circuit for outputting a pair of differential drive displacement current signals i from the MEMS gyroscope _ds After being amplified into voltage signals, the voltage signals are subjected to differential processing, and a path of first voltage signals V are output _DS ；

An amplitude control circuit for controlling the first voltage signal V _DS And 90 deg. phase shift to meet the phase condition of self-oscillating loop, and to produce driving signal to act on the driving comb teeth.

3. The small frequency differential MEMS gyroscope detection phase shift suppression system of claim 1, wherein the parametric suppression loop comprises:

a detection interface circuit for outputting a pair of differential detection displacement current signals i from the MEMS gyroscope _s Amplifying into voltage signal, differential processing, 90 deg. phase shifting to meet self-oscillation loop phase condition, outputting second voltage signal V _S ；

A detection amplitude multiplier for multiplying the second voltage signal V _S Self-multiplying;

a low-pass filter for extracting the second voltage signal V _S Amplitude information of (a);

the PI module is used for subtracting the output of the low-pass filter from the reference direct-current voltage;

a detection drive multiplier for outputting the PI module and the second voltage signal V _S Multiplication generates a detection drive signal V _SD For maintaining the operating frequency of the MEMS gyroscope detection mode at the detection frequency omega _s Is fixed in amplitude and oscillating;

and the band-pass phase shifter is used for generating a parameter suppression signal twice the detection frequency from the detection amplitude multiplier, and the phase-shifted 90 DEG phase-shifted parameter suppression comb teeth act on the detection resonator after meeting parameter suppression phase conditions.

4. The small frequency differential MEMS gyroscope detection phase shift suppression system of claim 1, wherein the angular velocity demodulation module comprises:

multiplier for multiplying the second voltage signal V _S And a first voltage signal V _DS Multiplying;

a low-pass filter for extracting the second voltage signal V _S And a first voltage signal V _DS The dc component resulting from multiplication, i.e. from the second voltage signal V _S Amplitude information of the driving frequency component is extracted to obtain input angular velocity information of the MEMS gyroscope.

5. The small frequency differential MEMS gyroscope detection phase shift suppression system of claim 2, wherein the drive interface circuit comprises:

a transimpedance amplifier for amplifying an input current signal into a voltage signal;

a differential amplifier for performing differential processing on the two voltage signals to suppress common mode interference and outputting a first voltage signal V _DS 。

6. The small frequency differential MEMS gyroscope detection phase shift suppression system of claim 3, wherein the detection interface circuit comprises:

a transimpedance amplifier for amplifying an input current signal into a voltage signal;

the differential amplifier is used for carrying out differential processing on the two paths of voltage signals and inhibiting common-mode interference;

the band-pass phase shifter is used for 90-degree phase shifting to meet the loop phase condition of self-oscillation and output a path of second voltage signal V _S 。