Online real-time measurement system for resonant frequency of single-port detection resonator of MEMS gyroscope

Abstract

The invention discloses a single-port detection resonator resonant frequency on-line real-time measurement system for an MEMS gyroscope, and the system comprises a closed-loop drive circuit which is used for driving a resonator to resonate and outputting a drive detection signal; the first C / V conversion circuit converts the current into a detection voltage signal, and the on-off of the first C / V conversion circuit and the negative resistance circuit is controlled by a voltage control switch; the negative resistance circuit enables the equivalent input resistance of the first C / V conversion circuit to be a negative value so as to generate positive damping feedback force on the detection resonator; the multiplier is used for carrying out multiplication demodulation on the detection voltage signal and the driving detection signal, and the angular velocity of the MEMS gyroscope is output after the signals are filtered by the low-pass filter; the upper computer controls the on-off of the voltage control switch, the frequency fd and the frequency fs are calculated through fast Fourier transform by driving the detection signal and the detection voltage signal respectively, the frequency difference is obtained by solving the difference, and the resonant frequency of the single-port detection resonator is measured on the premise that the work of the MEMS gyroscope is not affected.

Description

Technical Field

[0001] This invention belongs to the field of silicon micromechanical gyroscope detection, and in particular, it is a single-port detection resonator resonant frequency online real-time measurement system for MEMS gyroscopes. Background Technology

[0002] MEMS gyroscopes are miniaturized chip-based angular velocity sensors widely used in consumer electronics, automotive safety control, and other space-constrained applications due to their small size, light weight, and low power consumption. Any fault in a MEMS gyroscope that affects structural stiffness, mass distribution, or damping will directly impact the frequency and quality factor of its resonator. Temperature fluctuations cause the scaling factor to change with frequency differences, introducing angular velocity measurement errors. Online real-time measurement of the resonant frequency of the single-port detection resonator in a MEMS gyroscope allows for online monitoring of the gyroscope's operating status and real-time online scaling factor compensation.

[0003] For mode-separated MEMS gyroscopes, in open-loop detection mode, the single-port detection resonator is in a forced vibration state rather than a resonant state, and its resonant frequency cannot be directly obtained. A common testing method is to use one of the detection electrodes as the excitation electrode, applying an external excitation signal to make the detection resonator resonate, thereby measuring its resonant frequency. A less common method is to drive the detection resonator in a closed loop, which can also measure the resonant frequency of the single-port detection resonator. All of these methods are offline testing methods and cannot monitor changes in the resonant frequency of the single-port detection resonator online. Furthermore, the MEMS gyroscope loses its ability to measure angular velocity. In contrast, online measurement methods can characterize the resonant frequency of the single-port detection resonator online without affecting the normal operation of the MEMS gyroscope, making them more suitable for diverse application scenarios of MEMS gyroscopes.

[0004] Existing online testing methods for the resonant frequency of single-port detection resonators include determining a frequency difference of 0 by using the residual quadrature error and a 90° phase difference between the driving signal and the frequency. These methods are only applicable to mode-matched MEMS gyroscopes with a frequency difference of 0 and cannot characterize other frequency differences. Alternatively, the resonant frequency can be indirectly reflected by noise power spectrum estimation or the double-sideband amplitude of the vibration signal. Chinese patent CN111272193A discloses an online frequency difference identification method for MEMS gyroscopes based on noise power spectrum estimation. Under normal operating conditions, the theoretical power spectrum curve is correlated with the power spectrum curve of the output signal to calculate the frequency difference of the gyroscope's operating mode. This invention extracts resonant frequency information online in real time without affecting the normal operation of the MEMS gyroscope. This measurement method indirectly reflects the resonant frequency of the single-port detection resonator through noise power spectrum estimation. However, due to the small amplitude of the noise, accurately obtaining the noise under actual vibration conditions presents a challenge. Currently, there is no direct measurement method for the resonant frequency of a single-port detection resonator in a MEMS gyroscope that does not require an external excitation signal. Summary of the Invention

[0005] The purpose of this invention is to provide an online real-time measurement system for the resonant frequency of a single-port detection resonator in a MEMS gyroscope. Based on the negative impedance principle of an operational amplifier, a feedback loop constructed with a negative resistance circuit excites the detection resonator. The feedback loop only affects the gain of the signal at the resonant frequency of the detection resonator, without affecting the gain of the Coriolis force signal at the resonant frequency of the driving resonator. Without affecting the open-loop detection state of the MEMS gyroscope, the system can measure the resonant frequency of the single-port detection resonator online in real time, and can monitor the working status of the gyroscope and perform online real-time scaling factor compensation.

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

[0007] A single-port detection resonator resonant frequency online real-time measurement system for a MEMS gyroscope includes:

[0008] A closed-loop drive circuit is used to drive the resonator to resonate and output a drive detection signal.

[0009] The first C / V conversion circuit is used to convert the current signal output by the detection resonator into a detection voltage signal;

[0010] A voltage-controlled switch is used to control the on / off state of the first C / V conversion circuit and the negative resistance circuit. When the first C / V conversion circuit and the negative resistance circuit are connected, the resonator resonance is detected; when the first C / V conversion circuit and the negative resistance circuit are disconnected, the resonator forced vibration is detected.

[0011] The negative resistance circuit is used to make the equivalent input resistance of the first C / V conversion circuit negative, so as to generate a positive damping feedback force on the detection resonator.

[0012] The multiplier is used to multiply and demodulate the detection voltage signal and the drive detection signal output by the first C / V conversion circuit to obtain a demodulated signal containing the angular velocity output.

[0013] A low-pass filter is used to filter the demodulated signal output from the multiplier to obtain the angular velocity output of the MEMS gyroscope.

[0014] The host computer controls the on / off state of the voltage control switch. It calculates the resonant frequency f of the drive resonator using a Fast Fourier Transform (FFT) on the drive detection signal and the detection voltage signal, respectively. d and detection of the resonant frequency f s And calculate the difference to obtain the frequency difference Δf.

[0015] The significant advantages of this invention compared to existing technologies are:

[0016] (1) Compared with the traditional method of measuring the resonant frequency of a single-port detection resonator by applying an external excitation signal, the present invention does not require an external excitation signal port. A negative resistance circuit is connected to the operational amplifier to enhance the effective quality factor of the detection resonator and realize the self-excited oscillation of the single-port detection resonator. The circuit is controlled by a voltage control switch, which provides a new method for measuring the resonant frequency of a single-port detection resonator in the online state of a MEMS gyroscope, which is more convenient and faster.

[0017] (2) Compared with the method of indirectly reflecting the resonant frequency of a single-port resonator based on noise power spectrum estimation or double-sideband amplitude of vibration signal, the present invention directly characterizes the resonant frequency of a single-port resonator. The measurement and control system is simple and convenient and can directly measure the magnitude of the resonant frequency of the single-port resonator online in real time, thereby directly obtaining frequency difference information.

[0018] (3) Compared with the traditional scaling factor compensation method of MEMS gyroscope, the present invention measures the resonant frequency and frequency difference of the single-port detection resonator of MEMS gyroscope online, and provides a new real-time scaling factor compensation method. It can essentially eliminate the influence of frequency difference on scaling factor and perform real-time self-compensation of scaling factor to improve the temperature stability of scaling factor. Attached Figure Description

[0019] Figure 1 A schematic diagram of a system for online real-time measurement of the resonant frequency of a single-port resonator.

[0020] Figure 2 To realize a feedback system for detecting the self-excited oscillation of a resonator

[0021] Figure 3To detect the gain of the resonator;

[0022] Figure 4 A flowchart illustrating the application of detecting the resonant frequency of a resonator.

[0023] Figure 5 A schematic diagram showing the connection of the equivalent model of the resonator, the negative resistance circuit 4, and the first C / V conversion circuit 2;

[0024] Figure 6 The system-level block diagram shows a detection resonator with resistive load effect and its noise source.

[0025] Figure 7 Here is the control flowchart for voltage-controlled switch 3;

[0026] Figure 8 This is a time-domain diagram of the voltage signal detected using the measurement method of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1 This is a schematic diagram of an online real-time measurement system for the resonant frequency of a single-port detection resonator of a MEMS gyroscope, including: detection resonator detection electrode 1, first C / V conversion circuit 2, voltage control switch 3, negative resistance circuit 4, multiplier 5, low-pass filter 6, driving resonator driving electrode 7 and driving detection electrode 8, second C / V conversion circuit 9, phase shifting circuit, automatic gain control circuit and host computer.

[0029] The detection electrode 1 is the output electrode of the MEMS gyroscope detection resonator, and the transfer function H(s) of the detection resonator is expressed as:

[0030] (1)

[0031] Where, m y To detect the equivalent quality of the resonator, c yy To detect the damping coefficient of the resonator, k yy To detect the stiffness coefficient of the resonator, s is in the Laplace domain. The input angular velocity and the driving velocity form a Coriolis force to detect the forced vibration of the resonator and generate a current signal.

[0032] The first C / V conversion circuit 2 consists of an operational amplifier, a capacitor Cc, and a third resistor R3, with the following connection relationship: Figure 5As shown, the first C / V conversion circuit 2 is connected to the detection electrode 1. Through the amplification effect of the operational amplifier, the current signal is converted into a detection voltage signal. The inverting input of the operational amplifier is connected to the detection electrode 1, the negative resistor circuit is connected to the non-inverting input and the output input of the operational amplifier, and the capacitor Cc and the third resistor R3 are connected in parallel between the inverting input and the output input of the operational amplifier for frequency compensation and limiting the high-frequency bandwidth of the circuit, ensuring the stable operation of the operational amplifier.

[0033] After the negative resistance circuit 4 is connected to the first C / V conversion circuit 2, a second resistor R2 is connected between the non-inverting input and the output of the operational amplifier, and a first resistor R1 is connected between the non-inverting input and ground. Utilizing the negative impedance principle of the operational amplifier, the equivalent input resistance of the operational amplifier is reduced, thus achieving a negative equivalent input resistance for the first C / V conversion circuit 2. The motion equation of the detection resonator can then be written as:

[0034] (2)

[0035] Where, m y To detect the equivalent quality of the resonator, ω s To detect the resonant frequency of the resonator, To detect the acceleration of the resonator, To detect the velocity of the resonator, y represents the displacement of the resonator, and Q... eff To detect the effective quality factor of the resonator, k eff To detect the effective stiffness of the resonator, Q eff =m y ω s / (c+c1), where c is the inherent damping of the detection resonator, c1 is the tuning damping of the detection resonator, and F d As an external driving force, F th Thermomechanical noise force, due to the presence of negative resistance, results in a voltage opposite to the velocity of the detection resonator appearing on its detection electrode, generating a damping force feedback loop. This enhances the effective quality factor of the detection resonator, enabling self-excited oscillation of the detection resonator. Figure 2 As shown, the negative resistance circuit 4 introduces a feedback coefficient β, and the loop transfer function G(s) is expressed as:

[0036] (3)

[0037] s is in the Laplace domain, jω is in the frequency domain, where j is the imaginary unit and ω is the angular frequency. When performing frequency domain analysis, the transfer function is transformed from the Laplace domain to the frequency domain by replacing s with jω. d To drive the resonant frequency of the resonator, ω s To detect the resonant frequency of the resonator, H(jω) d To detect the resonator at frequency ω d The gain at point H(jω)s To detect the resonator at frequency ω s Gain at point G(jω) d ) is the loop at frequency ω d Gain at point G(jω) s ) is the loop at frequency ω s The gain at point ω, for the sensing resonator, H(jω) d )<<1,H(jω s If )>>1, then:

[0038] (4)

[0039] like Figure 3 As shown, the introduction of the feedback loop does not change the gain of the Coriolis force signal at the driving frequency, but only changes the signal gain at the resonant frequency of the detection resonator. The feedback coefficient β is determined by... Figure 5 The resistance ratio R1 / R2 in the circuit determines the gain at the resonant frequency of the detection resonator. By changing the resistance ratio, the gain at the resonant frequency of the detection resonator is altered, thus achieving self-excited oscillation of the detection resonator. At this time, the detection voltage signal output by the first C / V conversion circuit 2 contains AC signals of both the driving resonator resonant frequency and the detection resonator resonant frequency. The host computer acquires the detection voltage signal and obtains the resonant frequency f of the detection resonator using the Fast Fourier Transform spectrum analysis method. s Voltage control switch 3 controls the negative resistance circuit 4 to disconnect from the first C / V conversion circuit 2, detects the forced vibration of the resonator, and the MEMS gyroscope returns to the open-loop detection working state.

[0040] The multiplier 5 is used to multiply and demodulate the detection voltage signal and the drive detection signal output by the first C / V conversion circuit 2 to obtain a demodulated signal containing angular velocity output.

[0041] The low-pass filter 6 is used to filter the demodulated signal output by the multiplier 5, and the output DC voltage reflects the amplitude of the angular velocity output of the MEMS gyroscope.

[0042] The MEMS gyroscope driving electrode serves as the driving electrode 7 of the measurement system. The driving force is input from this electrode to the driving resonator. The output signal of the driving detection electrode 8 is returned to the driving electrode 7 via the second C / V conversion circuit 9, the phase-shifting circuit, and the automatic gain control circuit, forming a closed-loop driving circuit. The MEMS gyroscope driving resonator performs a steady-amplitude oscillation at the driving frequency. The host computer acquires the driving detection signal output from the phase-shifting circuit and obtains the resonant frequency f of the driving resonator using a fast Fourier transform spectrum analysis method. d The host computer will detect the resonant frequency f of the resonator. s With the resonant frequency f of the drive resonator d The frequency difference Δf is obtained by taking the difference.

[0043] The Figure 4 This is a flowchart illustrating the application of resonator frequency detection. The host computer acquires frequency difference performance parameters online in real time and sets a predicted frequency difference value as a judgment condition. When the measured frequency difference value is not equal to the predicted value, a fault signal is issued, which can monitor the working status of the MEMS gyroscope. When the MEMS gyroscope detection resonator operates in open-loop mode, the expression for the scaling factor is:

[0044] (5)

[0045] Where, m c Let m be the mass of the Coriolis mass block. y To detect the equivalent quality of the resonator, ω d and ω s The resonant frequencies of the driving resonator and the sensing resonator are Q, respectively. s To detect the quality factor of the resonator, |x| represents the vibration displacement amplitude of the resonator driven by the MEMS gyroscope, and K... yC To detect resonator displacement / detect resonator capacitance-to-gain, K CV This is the gain of the first C / V conversion circuit 2. When Δf changes due to temperature variations, it affects the gyroscope's scaling factor. The angular velocity output from the low-pass filter 6 is multiplied by the Δf obtained from the host computer to eliminate the influence of Δf on the scaling factor, thus achieving online real-time scaling factor compensation.

[0046] Figure 5 To test the equivalent model of the resonator, the connection diagram of the negative resistance circuit 4 and the first C / V conversion circuit 2, the first resistor R1 and the second resistor R2 are the resistors of the negative resistance circuit. The first C / V conversion circuit 2 consists of an operational amplifier, a capacitor Cc and a third resistor R3. i It is the input voltage of the operational amplifier, V. o This is the output voltage of the operational amplifier. When the negative resistor circuit 4 is connected to the first C / V conversion circuit 2, the output voltage of the operational amplifier is expressed as:

[0047] (6)

[0048] I i This is the input current of the operational amplifier, equal in magnitude to the current flowing from the output of the operational amplifier through the third resistor R3 to the input, but with the opposite sign.

[0049] (7)

[0050] Therefore, the equivalent input resistance R of the operational amplifier in Represented as:

[0051] (8)

[0052] Figure 6 This is a system-level block diagram of a detection resonator with resistive loading effect and its noise source, m y To detect the equivalent quality of the resonator, c yy To detect the damping coefficient of the resonator, k yy To detect the stiffness coefficient of the resonator, To detect the acceleration of the resonator, To detect the velocity of the resonator, y is the displacement of the resonator, and F is the displacement of the resonator. C For Coriolis force, F th For thermomechanical noise force, R in R is the equivalent input resistance of the operational amplifier. After the negative resistance circuit 4 is connected to the first C / V conversion circuit 2, R in It is a negative value, and is in phase with the feedback current i of the resonator speed detection. t After R in This generates a voltage -V that is out of phase with the speed of the resonator being detected. t -V t Appearing on the detection electrode of the detection resonator, it generates a positive damping feedback force F. e This enhances the effective quality factor of the detection resonator. When the effective quality factor is enhanced to a certain value, the detection resonator will self-oscillate.

[0053] Figure 7 The flowchart for the voltage control switch 3 shows that the MEMS gyroscope is in closed-loop drive and open-loop detection mode. The host computer outputs a connection level signal, and the voltage control switch 3 controls the connection of the first C / V conversion circuit 2 with the negative resistor circuit 4. At this time, the negative resistor circuit excites the detection resonator, and the detection resonator is in a self-excited oscillation state. The detection voltage signal output by the first C / V conversion circuit 2 is fed back to the host computer. The host computer processes the detection voltage signal and outputs a disconnection level signal. The voltage control switch 3 controls the first C / V conversion circuit 2 to disconnect from the negative resistor circuit 4. The negative resistor circuit 4 no longer excites the detection resonator, and the detection resonator is in a forced vibration state. The MEMS gyroscope returns to the open-loop detection mode.

[0054] Figure 8 The time-domain diagram of the voltage signal detected by the measurement method of the present invention is shown. When the first C / V conversion circuit 2 is disconnected from the negative resistor circuit 4, the MEMS gyroscope detection resonator is in a non-resonant state, and the detected voltage signal only contains the signal of the driving frequency. After the first C / V conversion circuit 2 is connected to the negative resistor circuit 4, the detection resonator self-oscillates, and the detected voltage signal is superimposed on the signal of the original driving resonator resonant frequency.

[0055] In summary, the specific embodiments disclosed in this invention are as shown above. However, this content is only an example to help operators understand this invention and is not intended to limit the design of this invention. All equivalent changes made based on the key design features of this case fall within the protection scope of this case.

Claims

1. A system for online real-time measurement of the resonant frequency of a single-port resonator in a MEMS gyroscope, characterized in that, include: A closed-loop drive circuit is used to drive the resonator to resonate and output a drive detection signal. The first C / V conversion circuit is used to convert the current signal output by the detection resonator into a detection voltage signal; A voltage-controlled switch is used to control the on / off state of the first C / V conversion circuit and the negative resistance circuit. When the first C / V conversion circuit and the negative resistance circuit are connected, the resonator resonance is detected; when the first C / V conversion circuit and the negative resistance circuit are disconnected, the resonator forced vibration is detected. The negative resistance circuit is used to make the equivalent input resistance of the first C / V conversion circuit negative, so as to generate a positive damping feedback force on the detection resonator. The multiplier is used to multiply and demodulate the detection voltage signal and the drive detection signal output by the first C / V conversion circuit to obtain a demodulated signal containing the angular velocity output. A low-pass filter is used to filter the demodulated signal output from the multiplier to obtain the angular velocity output of the MEMS gyroscope. The host computer controls the on / off state of the voltage control switch. It calculates the resonant frequency f of the drive resonator using a Fast Fourier Transform (FFT) on both the drive detection signal and the detection voltage signal. d and detection of the resonant frequency f s And calculate the difference to obtain the frequency difference Δf.

2. The online real-time measurement system for the resonant frequency of a single-port resonator of a MEMS gyroscope according to claim 1, characterized in that, The first C / V conversion circuit consists of an operational amplifier, a capacitor Cc, and a third resistor R3; the negative resistance circuit includes a first resistor R1 and a second resistor R2; the inverting input of the operational amplifier is connected to the detection electrode, the negative resistance circuit is connected to the non-inverting input and the output terminal of the operational amplifier, and the capacitor Cc and the third resistor R3 are connected in parallel between the inverting input and the output terminal of the operational amplifier; the non-inverting input and the output terminal of the operational amplifier are connected to the second resistor R2, and the non-inverting input and ground are connected to the first resistor R1; after the negative resistance circuit is connected to the first C / V conversion circuit, the equivalent input resistance of the first C / V conversion circuit is negative, generating a voltage opposite to the speed of the detection resonator, which acts on the detection electrode of the detection resonator to generate a positive damping feedback force.

3. The online real-time measurement system for the resonant frequency of a single-port resonator of a MEMS gyroscope according to claim 1, characterized in that, The closed-loop drive circuit includes: The second C / V conversion circuit is used to convert the current signal output by the drive resonator into a drive detection signal; The phase-shifting circuit is used to convert the output signal of the second C / V conversion circuit into a phase-shifted drive detection signal by shifting the phase by 90 degrees through an integrator. The automatic gain control circuit is used to convert the phase-shifted drive detection signal into a positive half-cycle signal, extract the signal amplitude, compare the signal amplitude with the reference voltage, and finally output the gain control level.

4. The online real-time measurement system for the resonant frequency of a single-port resonator of a MEMS gyroscope according to claim 1, characterized in that, The host computer sets a predicted frequency difference value. After acquiring the frequency difference online in real time, it uses the predicted frequency difference value as a judgment condition. When the measured frequency difference value is not equal to the predicted value, a fault signal is issued to monitor the working status of the MEMS gyroscope. The angular velocity output by the low-pass filter is multiplied by the acquired frequency difference to eliminate the influence of the frequency difference on the scaling factor and realize online real-time scaling factor compensation.

5. The online real-time measurement system for the resonant frequency of a single-port resonator of a MEMS gyroscope according to claim 1, characterized in that, The voltage control switch is switched on and off via a level signal. The host computer outputs a connection level signal, and the voltage control switch controls the first C / V conversion circuit to connect with the negative resistor circuit. The host computer outputs a disconnect level signal, and the voltage control switch controls the first C / V conversion circuit to disconnect from the negative resistor circuit.

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