阅读说明：本技术 一种双路正交移相解调滤波的mems陀螺干扰抑制方法 (MEMS gyro interference suppression method for two-way quadrature phase-shift demodulation filtering ) 是由 冯立辉 邬俊杰 郭芃 孙宇飞 崔建民 卢继华 于 2020-12-14 设计创作，主要内容包括：本发明涉及一种双路正交移相解调滤波的MEMS陀螺干扰抑制方法,属于MEMS陀螺仪及抗干扰技术领域。所述方法,包括：位移传感信号通过放大器放大,分别乘以I路和Q路解调信号再进行低通滤波；判断Q路低通滤波后的信号中是否含有交流分量,若不包含则输出I路低通滤波后的信号为角速度信号,否则报警提示并对Q路低通滤波后的信号进行希尔伯特变换；将I路低通滤波后信号和Q路希尔伯特变换后信号分别相加和相减,截取相加和相减后信号中时间轴相同的一段信号,计算这两段信号的能量大小,选择能量较小的那一段信号为角速度信号。所述方法能滤除作用在传感方向上频率不等于驱动频率的位移干扰信号,简化了陀螺仪的结构和体积,也降低了制造成本。(The invention relates to an MEMS gyroscope interference suppression method of two-way quadrature phase shift demodulation filtering, belonging to the technical field of MEMS gyroscopes and interference resistance. The method comprises the following steps: amplifying the displacement sensing signal by an amplifier, multiplying the amplified displacement sensing signal by the I path demodulation signal and the Q path demodulation signal respectively, and then performing low-pass filtering; judging whether the Q path of low-pass filtered signals contain alternating current components, if not, outputting the I path of low-pass filtered signals as angular velocity signals, otherwise, giving an alarm and performing Hilbert transform on the Q path of low-pass filtered signals; and respectively adding and subtracting the I-path low-pass filtered signal and the Q-path Hilbert transformed signal, intercepting a section of signal with the same time axis in the added and subtracted signal, calculating the energy of the two sections of signals, and selecting the section of signal with smaller energy as an angular velocity signal. The method can filter the displacement interference signals with the frequency not equal to the driving frequency acting on the sensing direction, simplify the structure and the volume of the gyroscope and reduce the manufacturing cost.)

1. A method for suppressing interference of two-way quadrature phase shift demodulation filtering is characterized in that: the method comprises the following steps:

step 1, amplifying a displacement sensing signal of a gyroscope through an amplifier to obtain an amplified displacement sensing signal;

step 2, multiplying the amplified displacement sensing signal by an I path demodulation signal, and obtaining an I path low-pass filtered signal after passing through a low-pass filter;

step 3, multiplying the amplified displacement sensing signal by a Q-path demodulation signal, and obtaining a Q-path low-pass filtered signal after passing through a low-pass filter;

step 4, judging whether the Q path of low-pass filtered signals contain alternating current components, if not, outputting I path of low-pass filtered signals as complete angular velocity signals, otherwise, giving an alarm and jumping to the step 5;

step 5, performing Hilbert transform on the Q-path low-pass filtered signal to obtain a Q-path Hilbert transformed signal;

step 6, adding and subtracting the I path of low-pass filtered signal and the Q path of Hilbert transformed signal respectively to obtain an added signal and a subtracted signal;

step 7, respectively intercepting a section of signal with the same time axis in the added signal and the subtracted signal, and calculating the energy of the two sections of signals;

and 8, selecting the signal corresponding to the section of signal with smaller energy as the required complete angular velocity signal.

2. The interference suppression method of two-way quadrature phase shift demodulation filtering according to claim 1, wherein: the method relies on displacement sensing signals, the signals are divided into I, Q paths of signals after passing through an amplifier, compared with a single-path demodulation filtering method, a Q-path demodulation phase-shifting circuit is added, namely Q-path demodulation filtering is added on the basis of the original single-path demodulation filtering method of the MEMS gyroscope, and displacement interference signals with different frequencies and driving frequencies in the sensing direction can be filtered.

3. The interference suppression method of two-way quadrature phase shift demodulation filtering according to claim 2, wherein: in step 2, the I path of demodulated signal is recorded as: cos (omega)_dt+φ_x+φ_y)；ω_dIndicating the demodulation frequency, phi_xTo representPhase-frequency characteristic of the driving direction, phi_yThe phase frequency characteristic representing the sensing direction.

4. The interference suppression method of two-way quadrature phase shift demodulation filtering according to claim 3, wherein: in step 3, Q paths of demodulated signals are recorded as: sin (omega)_dt+φ_x+φ_y) (ii) a The demodulation frequency omega of the Q-path demodulation signal_dDemodulation frequency omega of I-path demodulation signal_dSimilarly, the phase differs by 90 ° from the phase of the I-path demodulated signal.

5. The interference suppression method of two-way quadrature phase-shift demodulation filtering according to claim 4, wherein: in step 4, if the alternating current component is not contained, the gyroscope is not interfered by sound waves; if the alternating current component is contained, the gyroscope is indicated to be subjected to sound wave interference.

6. The interference suppression method of two-way quadrature phase shift demodulation filtering according to claim 5, wherein: in step 7, the proportion of the first section of signal to the added signal and the subtracted signal is 10% -90%.

Technical Field

The invention particularly relates to an MEMS gyroscope interference suppression method of two-way quadrature phase shift demodulation filtering, and belongs to the technical field of MEMS gyroscopes and interference resistance.

Background

MEMS gyroscopes for measuring angular velocity and angular acceleration have been rapidly developed in recent years due to their advantages of small size, light weight, low power consumption, low cost, easy integration, etc., and are widely used in the fields of aerospace, automotive industry, intelligent electronic devices, etc. However, the MEMS gyroscope adopts a spring-mass-damping structure, and is susceptible to acoustic wave and vibration interference near a resonant frequency, resulting in the gyroscope outputting an incorrect angular velocity signal. The control system calling the gyroscope data does not generally check the accuracy of the sensing data, so that the control system carrying the MEMS gyroscope is easily interfered by sound waves and vibration, and equipment is out of control and even damaged. Since the gyroscope mainly works in a sound wave frequency band and is easily interfered by sound waves, corresponding protective measures need to be taken against the sound wave interference.

The simplest protection method is to increase the resonance frequency of the MEMS gyroscope to be outside the acoustic frequency range. The scheme can ensure that the MEMS gyroscope is not interfered by sound waves, but can ensure that the gyroscope is easily influenced by interference signals of other frequency bands, and the method cannot fundamentally protect the MEMS gyroscope.

The existing acoustic protection method mainly comprises two aspects of physical sound insulation and optimization of a sensor structure. The physical sound insulation means is to coat a sound absorption material on the MEMS gyroscope. The method utilizes the sound absorption material to design and manufacture the shell, and then the shell wraps the gyroscope, thereby achieving good noise reduction effect. However, sound absorbing materials are generally only effective for sound waves of a specific frequency band, and need to be prepared and designed for the resonance frequency of the gyroscope. Furthermore, the application of sound absorbing material also increases the volume of the overall sensor and also increases manufacturing costs. Optimizing the sensor structure refers to using dual-mass blocks in a MEMS gyroscope to make measurements. The method adopts two completely same mass blocks, when the gyroscope works, simple harmonic driving voltage with same frequency and opposite phase is applied to the two mass blocks, so that the two mass blocks vibrate with same amplitude and opposite phase, signals generated by the two mass blocks are differentiated, and sound wave interference signals can be eliminated theoretically. However, in practical use, the gyroscope with the structure is still easily subjected to acoustic interference, which indicates that the distribution situation of the sound field inside the gyroscope is complex, and the acoustic interference signals acting on the two mass blocks are not completely in a common mode.

Although the currently used acoustic protection methods for MEMS gyroscopes can achieve a certain degree of protection, these methods have great limitations. Therefore, the invention provides an MEMS gyro interference suppression method of two-way quadrature phase shift demodulation filtering.

Disclosure of Invention

The invention aims to overcome the technical defects that the protection effect cannot cover the whole sound wave frequency band, the protection effect only on common-mode noise is ideal, and the protection effect on non-common-mode interference is poor in the existing MEMS gyroscope acoustic protection method, and provides an interference suppression method for two-path orthogonal phase-shift demodulation filtering.

The MEMS gyro interference suppression method based on two-way quadrature phase shift demodulation filtering comprises the following steps:

step 1, amplifying a displacement sensing signal of a gyroscope through an amplifier to obtain an amplified displacement sensing signal;

step 2, multiplying the amplified displacement sensing signal by an I path demodulation signal, and obtaining an I path low-pass filtered signal after passing through a low-pass filter;

wherein, the I path demodulated signal is recorded as: cos (omega)_dt+φ_x+φ_y)；

ω_dIndicating the demodulation frequency, phi_xPhase-frequency characteristic, phi, representing the driving direction_yA phase-frequency characteristic representing a sensing direction;

step 3, multiplying the amplified displacement sensing signal by a Q-path demodulation signal, and obtaining a Q-path low-pass filtered signal after passing through a low-pass filter;

wherein, Q way demodulation signal is noted as: sin (omega)_dt+φ_x+φ_y) (ii) a The demodulation frequency omega of the Q-path demodulation signal_dDemodulation frequency omega of I-path demodulation signal_dThe phase difference is 90 degrees with the phase of the I path demodulation signal;

step 4, judging whether the Q path of low-pass filtered signals contain alternating current components, if not, outputting I path of low-pass filtered signals as complete angular velocity signals, otherwise, giving an alarm and jumping to the step 5;

if the alternating current component is not contained, the gyroscope is not interfered by sound waves; if the gyroscope contains the alternating current component, the gyroscope is subjected to sound wave interference;

step 5, performing Hilbert transform on the Q-path low-pass filtered signal to obtain a Q-path Hilbert transformed signal;

step 6, adding and subtracting the I path of low-pass filtered signal and the Q path of Hilbert transformed signal respectively to obtain an added signal and a subtracted signal;

step 7, respectively intercepting a section of signal with the same time axis in the added signal and the subtracted signal, and calculating the energy of the two sections of signals;

wherein, the proportion range of the first section of signal in the added signal and the subtracted signal is 10% -90%;

step 8, selecting a signal corresponding to the section of signal with smaller energy as a required complete angular velocity signal; thus, the interference suppression method of the two-way quadrature phase shift demodulation filtering is completed through the steps 1 to 8.

Advantageous effects

Compared with the prior single-path demodulation method, the MEMS gyro interference suppression method of the two-path orthogonal phase shift demodulation filtering has the following beneficial effects:

1. the method can obtain complete angular velocity information, simultaneously filter displacement interference signals with frequencies not equal to the driving frequency and acting on the sensing direction, and has a protection effect on sound wave interference signals of the whole sound wave frequency band;

2. according to the method, a mass block does not need to be additionally arranged in the gyroscope or a protective shell does not need to be additionally arranged outside the gyroscope, so that the structure of the gyroscope is simplified, the volume of the gyroscope is reduced, and meanwhile, the manufacturing cost is also reduced.

Drawings

FIG. 1 is a flow chart of the interference suppression method of the two-way quadrature phase shift demodulation filtering of the present invention;

FIG. 2 is a simulation result of the output signals of the one-way (a) and two-way (b) filtering method in a non-acoustic wave environment when the angular velocity to be measured is 0 °/s;

FIG. 3 is a simulation result of signals output by the one-way (a) and two-way (b) filtering methods in a sound wave environment with a frequency of 5592Hz when the angular velocity to be measured is 0 °/s;

FIG. 4 is a simulation result of the output signals of the one-way (a) and two-way (b) filtering method in the acoustic wave environment with the frequency of 5592Hz when the angular velocity to be measured is 50 °/s;

fig. 5 is a simulation result of output signals of the one-way (a) and two-way (b) filtering methods in a sound wave environment with a frequency of 5598Hz when the angular velocity to be measured is 0 °/s.

Detailed Description

The method for suppressing the interference of the MEMS gyroscope with two-way quadrature phase shift demodulation and filtering according to the present invention is described in detail with reference to the following embodiments, and the embodiments of the method according to the present invention are described with reference to the accompanying drawings.

Example 1

When acoustic interference is present, the action of the acoustic waves is equivalent to the action of the force. The motion of a MEMS gyroscope can be described by the kinetic equations:

wherein, x is the displacement in the driving direction and represents the driving mode of the MEMS gyroscope, and y is the displacement in the sensing direction and representsA modality is detected.Andrepresenting the velocity and acceleration in the driving and sensing directions, respectively. m is_x、m_yMasses in the drive and sense directions, respectively, D_xx、D_yyAs damping coefficient, k_xx、k_yyIs the elastic coefficient. D_xy、D_yxParameters introduced for non-proportional damping, k_xy、k_yxThe parameters introduced for anisoelasticity characterize the interplay of motion in both the drive and sense directions. Omega (t) is the angular velocity omega_nIs the frequency of the sound wave, F_X、F_YExternal forces in the driving and sensing directions, respectively.

In practice, the coupling coefficient between the driving direction and the sensing direction is very small. In order to analyze the displacement signal of the gyroscope under the action of sound pressure and facilitate the calculation process, the formula (1) is reasonably simplified, namely, no external force exists in the sensing direction, and only sound interference exists, namely F_Y0; the displacement in the sensing direction is very small. Therefore, the effect of coupling the sense direction to the drive direction can be neglected, i.e. removing D in equation (1) above_xyAnd k_xyThe influence of (c). However, due to the limitation of the manufacturing process, the influence of the motion coupling from the driving direction to the sensing direction is large and cannot be ignored. Finally, by solving the simplified kinetic equation, the sensing displacement signal y (t) in the sound-wave-free environment and the displacement interference signal N brought by the sound wave can be obtained_y(t) analytical formula

Wherein, ω is_dTo drive the frequency, A_x、A_yRespectively characterizing the amplitude-frequency characteristics, phi, of the driving direction and the sensing direction_x、φ_yThe phase-frequency characteristics, A, characterizing the driving direction and the sensing direction, respectively_Nx、A_NyRespectively representing the amplitude-frequency characteristics, phi, of the driving direction and sensing direction displacement interference signals_Nx、φ_NyCharacterizing the phase, phi, of the acoustic wave in the driving direction and the sensing direction, respectively_NxxCharacterizing the phase-frequency characteristic, phi, of the displacement disturbance signal in the driving direction_Nyy、φ_NxyAnd characterizing the phase-frequency characteristics of the displacement interference signal in the sensing direction.

The following MEMS gyro interference suppression process of the two-way quadrature phase shift demodulation filtering according to the present invention is shown in FIG. 1 depending on the system and the process respectively, and includes the following steps:

and step 1, amplifying the displacement sensing signal of the gyroscope through an amplifier, and collecting the amplified displacement sensing signal.

Step 2, multiplying the collected amplified displacement sensing signal by an I-path demodulation signal cos (omega)_dt+φ_x+φ_y) Then the signal V is processed by a low-pass filter to obtain a signal V after I path of low-pass filtering_I。

From equations (2), (3) and the flow shown in fig. 1, it can be deduced that:

when the sound wave interference does not exist,

when the sound wave interference exists,

step 3, multiplying the collected amplified displacement sensing signal by a Q-path demodulation signal sin (omega)_dt+φ_x+φ_y) Then the Q path low-pass filtered signal V is obtained after passing through a low-pass filter_Q；

The demodulation frequency of the Q path demodulation signal is the same as that of the I path demodulation signal, and the phase difference between the Q path demodulation signal and the I path demodulation signal is 90 degrees.

From equations (2), (3) and the flow shown in fig. 1, it can be deduced that:

when the sound wave interference does not exist,

when the sound wave interference exists,

and 4, judging whether the Q path of low-pass filtered signals contain alternating current components, if not, outputting the I path of low-pass filtered signals as complete angular velocity signals, otherwise, giving an alarm and jumping to the step 5.

Comparing equations (6) and (7), it can be seen that, when there is no sound wave interference, the Q path low-pass filtered signal only contains a direct current component, and at this time, the I path low-pass filtered signal can be directly output as a complete angular velocity signal. When sound wave interference exists, the Q-path low-pass filtered signal contains low-frequency alternating current components besides direct current components.

And intercepting a section of signal from the Q path low-pass filtered signal, and calculating the energy of the signal. Wherein, the proportion range of the first-stage signal in the Q-path low-pass filtered signal is 10%. The energy level is defined as the root mean square value of the size of all data points in a segment of signal, i.e. the energy level is

Wherein n is the number of data points, m_iIs the size of the ith data point.

If the energy E of the Q path low-pass filtered signal_QSatisfies the conditions

The gyroscope is considered to be subject to acoustic interference. Where δ represents the minimum resolution of the gyroscope. According to the characteristic, an alarm prompting mechanism can be established to alarm the sound wave interference, and then the step 5 is carried out.

And 5, processing the Q path of low-pass filtered signal by Hilbert transform to obtain a Q path of Hilbert transformed signal V'_Q。

The hilbert transform, which is used to compensate for the 90 phase shift in the method, is a commonly used method in communication systems. The hilbert transform of a continuous-time signal s (t) corresponds to the output signal of the signal after passing through a linear system with an impulse response of 1/(tt), which can be expressed as:

wherein denotes a convolution operation; the hilbert transform is essentially a phase shifter, whose frequency domain form is:

the direct current component of the signal after Hilbert transform can be filtered, the amplitude of other frequency components is kept unchanged, but the phase is shifted by 90 degrees. The acoustic frequency is less than the driving frequency, and the phase is 90 degrees ahead; the frequency of the sound wave is greater than the driving frequency, and the phase lags by 90 degrees, i.e.

Step 6, adding and subtracting the I path low-pass filtered signal and the Q path Hilbert signal respectively to obtain an added signal V₊And the subtraction signal V_-。

When the frequency of the sound wave is less than the driving frequency, the complete angular velocity signal is

When the sound wave frequency is greater than the driving frequency, the complete angular velocity signal is

This method also requires comparison of the magnitude of the acoustic wave frequency and the driving frequency, which are obtained in advance. It is clear that the complete angular velocity signal does not contain a displacement interference signal, and therefore it must be the lower energy one of the added and subtracted signals, and step 6 is continued.

And 7, respectively intercepting a small section of signal with the same time axis in the addition signal and the subtraction signal, calculating the energy of the two small sections of signal, and comparing.

Wherein, the proportion range of the signal after the addition and the signal after the subtraction is 10%, the energy size calculation formula is the same as the formula (9).

And 8, selecting the signal corresponding to the section of signal with smaller energy as the required complete angular velocity signal.

So far, through the steps 1 to 8, the MEMS gyroscope interference suppression of the two-way quadrature phase shift demodulation filtering is completed.

Matlab is used for simulating the filtering effect of the IQ double-path orthogonal demodulation filtering method in various sound wave environments, and specific simulation parameters are shown in the table below.

TABLE 1 simulation parameters

Firstly, responses of two methods to angular velocity signals in a sound-free environment are simulated, and the simulation result is shown in fig. 2. V in FIG. 2_IThe output signal of the single-path demodulation filtering method in the non-acoustic wave interference environment is in direct proportion to the angular speed to be measured. When the angular speed to be measured is 0 DEG/s, the output signal has 0.5V direct current bias, which is an in-phase error angular speed signal introduced by non-proportional damping. V in FIG. 2_IQThe IQ double-path orthogonal phase-shift demodulation filtering method is an output signal of the IQ double-path orthogonal phase-shift demodulation filtering method in a non-acoustic wave interference environment, and the two methods have consistent response to angular velocity, which shows that the normal angular velocity measurement of the gyroscope cannot be influenced by the IQ double-path orthogonal phase-shift demodulation filtering method.

And then simulating the influence of the sound wave interference on a single-path demodulation filtering method and an IQ double-path orthogonal phase-shift demodulation filtering method. Assuming that the angular velocity to be measured is 0 °/s and a sound wave with a frequency of 5592Hz exists in the working environment, the output signals of the two methods in the sound wave interference environment are simulated, and the simulation result is shown in fig. 3. As can be seen from fig. 3(a), a sinusoidal oscillation with a frequency of 10Hz is present in the output signal of the one-way demodulation filtering method, and the oscillation amplitude is 0.39V. This is because the single-path demodulation filtering method cannot filter the displacement interference signal, which results in the gyroscope outputting a pseudo angular velocity signal, and the oscillation frequency of the pseudo angular velocity signal is the difference between the sound frequency (5592Hz) and the driving frequency (5602 Hz). As can be seen from fig. 3(b), a pseudo angular velocity signal with a frequency of 10Hz still exists in the output signal of the IQ dual-path quadrature phase-shift demodulation filtering method, but the oscillation amplitude is significantly reduced to 0.015V. Compared with simulation results of the two methods, the IQ two-way orthogonal phase-shift demodulation filtering method can effectively filter displacement interference signals brought by sound waves, and the filtering effect can reach 96.3%.

In order to verify the universality of the IQ two-way quadrature phase-shift demodulation filtering method, the simulation state is changed next. The gyroscope was subjected to an angular velocity of 50 °/s, and the output signals of both methods were simulated in the acoustic environment also at a frequency of 5592Hz, and the simulation results are shown in fig. 4. As can be seen from fig. 4(a), an angular velocity signal of 1.36V and a pseudo angular velocity signal having an oscillation amplitude of 0.395V coexist in the output signal. As can be seen from fig. 4(b), after the IQ dual-path quadrature phase-shift demodulation filtering method is adopted, the oscillation amplitude of the pseudo angular velocity signal is reduced to 0.01V, and the filtering effect can reach 97.5%.

And finally, verifying the filtering effect of the IQ double-path orthogonal phase-shift demodulation filtering method on displacement interference signals with different frequencies. Assuming that the angular velocity to be measured is 0 °/s, the sound wave with the frequency of 5598Hz exists in the working environment, the output signals of the two methods in the sound wave interference environment are simulated, and the simulation result is shown in fig. 5. As can be seen from fig. 5(a), the oscillation amplitude caused by the acoustic wave in the output signal is 0.415V, and the oscillation frequency is 4 Hz. As can be seen from fig. 5(b), after the IQ dual-path quadrature phase-shift demodulation filtering method is adopted, the oscillation amplitude is reduced to 0.015V, and the filtering effect can reach 96.4%.

The simulation results show that the method provided by the invention can effectively filter displacement interference signals of various frequencies on the premise of ensuring the integrity of angular velocity signals, and the filtering effect can generally reach 96%. The method does not need to additionally increase a mass block in the gyroscope or additionally install a protective shell outside the gyroscope, simplifies the structure of the gyroscope, reduces the volume of the gyroscope and reduces the manufacturing cost at the same time.

While the foregoing is directed to the preferred embodiment of the present invention, it is not intended that the invention be limited to the embodiment and the drawings disclosed herein. The description of the implementation is only intended to help understand the method of the invention and its core ideas; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and the content of the present specification should not be construed as a limitation to the present invention. Various obvious modifications to it without departing from the spirit of the process of the invention and the scope of the claims are within the scope of protection of the invention.