An acceleration measurement method based on multimodal micromechanical detection

Abstract

This invention discloses an acceleration measurement method based on multimodal micromechanical detection, belonging to the field of microelectromechanical sensor technology. Its basic operating principle is: by designing a uniaxial multimodal resonator system, including multiple masses and elastic beams, the displacement caused by uniaxial acceleration is synchronously detected using quasi-static and multi-order vibration modes. A multimodal filter is designed to achieve weight distribution of each order of displacement detection. The final displacement of the mass caused by acceleration is obtained through weighted fusion. In open-loop operation, this displacement directly represents the magnitude of acceleration. In closed-loop operation, the feedback control voltage that maintains this displacement constant represents the magnitude of acceleration. This invention can effectively suppress common-mode error and temperature drift and expand bandwidth.

Description

Technical Field

[0001] The present invention belongs to the technical field of acceleration sensors, and more specifically, relates to an acceleration measurement method based on multimodal micromechanical detection. Background Art

[0002] Accelerometers typically employ two detection methods: displacement and frequency. These methods typically measure quasi-static displacement changes caused by uniaxial acceleration or frequency changes in a resonant subsystem. Accordingly, capacitive micromachined accelerometers are categorized into quasi-static and resonant types, each with its own advantages and disadvantages. For example, the former offers high sensitivity but limited bandwidth, while the latter offers a wide dynamic range but low sensitivity. Since these two types of accelerometers operate in quasi-static and resonant states, respectively, integrating these two detection methods into a single sensor inevitably interferes with each other, making it difficult to achieve complementary advantages and disadvantages. Summary of the Invention

[0003] In response to the shortcomings and deficiencies of existing micromechanical accelerometers, the present invention provides an acceleration measurement method based on multimodal micromechanical detection. By constructing a multimodal micromechanical resonator system, which includes multiple micromasses and microelastic beams, the multimodal micromechanical resonator system is used to synchronously measure displacement. High-precision and high-bandwidth acceleration measurement is achieved through a filtering fusion method. In the traditional operating mode (quasi-static), due to the large stiffness of the elastic beams between the multiple masses, the same displacement is generated synchronously, which can be represented by measuring the displacement of one of the main masses using a capacitance detection method.

[0004] In high-order vibration modes, the main mass block generates high-order vibrations under the action of the variable-spacing actuator. The magnitude of the vibration is positively correlated with the displacement of the main mass block. The displacement of the main mass block can be synchronously measured by demodulating the magnitude of the vibration.

[0005] In open-loop operation, the multimodal displacements detected by synchronous testing are processed by designing a multimodal filter. That is, different weights are assigned according to the acceleration frequency information, and the displacement information is weighted to achieve data fusion to characterize the acceleration magnitude.

[0006] During closed-loop operation, the feedback control voltage is calculated by comparing the fused displacement with the reference displacement and applied to the variable area actuator to generate a balancing force, so that the displacement is fixed at a set position, such as the zero position.

[0007] The technical solution adopted in the present invention is as follows:

[0008] In a first aspect, the present invention provides a multi-modal micromechanical resonator system, comprising a multi-modal mass-spring system and a capacitor that moves along a single axis and is composed of multiple masses and elastic beams, wherein the multiple masses are connected to each other via high-rigidity elastic beams, and each of the multiple masses is connected to an anchor region via a low-rigidity elastic beam.

[0009] Mobile comb-tooth electrodes are distributed on a main mass block among the multiple mass blocks, including first mobile comb-tooth electrodes arranged on the left and right sides of the main mass block, and second, third, and fourth mobile comb-tooth electrodes arranged on the upper and lower sides of the main mass block; the direction of the first mobile comb-tooth electrode is the same as the direction of movement of the main mass block, and the directions of the second, third, and fourth mobile comb-tooth electrodes are perpendicular to the direction of movement of the main mass block;

[0010] The first movable comb electrode on the left and the fixed comb electrode fixed in the anchor area on the left side of the main mass block form a first variable area driver; the first movable comb electrode on the right and the fixed comb electrode fixed in the anchor area on the right side of the main mass block form a second variable area driver; the second movable comb electrode, the third movable comb electrode and the fourth movable comb electrode on the upper and lower sides respectively form a first variable spacing capacitor, a variable spacing driver and a second variable spacing capacitor with the corresponding fixed comb electrodes fixed in the anchor areas on the upper and lower sides of the main mass block.

[0011] As a preferred embodiment of the present invention, the large-rigidity elastic beam and the small-rigidity elastic beam are arranged in parallel along the uniaxial motion direction, and the rigidity of the large-rigidity elastic beam is much greater than that of the small-rigidity elastic beam.

[0012] As a preferred embodiment of the present invention, the variable pitch driver is a differential structure, which is used to drive the main mass block to generate high-order resonance and generate electrostatic negative stiffness.

[0013] In a second aspect, the present invention provides an acceleration measurement method based on multimodal micromechanical detection, which is implemented using the above-mentioned multimodal micromechanical resonator system. When the multimodal micromechanical resonator system is subjected to an acceleration below the fundamental frequency, multiple masses synchronously generate approximate displacements. Open-loop and closed-loop acceleration detection are respectively implemented by detecting the displacement of the main mass block or maintaining the position of the main mass block constant, wherein the feedback control voltage of the closed-loop acceleration detection is applied to the first variable area driver and the second variable area driver.

[0014] The multi-modal micromechanical resonator system generates high-order vibration modes under high-frequency excitation. In the high-order vibration modes, the vibration amplitude of the main mass block is positively correlated with the displacement of the main mass block. The displacement of the main mass block is synchronously measured by demodulating the vibration amplitude.

[0015] Furthermore, the relationship between the vibration amplitude of the main mass block and the displacement of the main mass block is as follows:

[0016]

[0017] Where δ is the vibration amplitude of the main mass block, x is the displacement of the main mass block, μ and Q are the variable spacing actuator constant and quality factor, respectively, and k m is the m-order modal elastic coefficient, V d V is the DC component of the excitation signal applied by the variable pitch driver. a It is the AC component of the excitation signal applied to the variable pitch driver.

[0018] Furthermore, the open-loop acceleration detection method includes:

[0019] Carrier signals with opposite phases are applied to the first variable-spacing capacitor and the second variable-spacing capacitor, and a high-order modal resonance excitation signal is applied to the variable-spacing driver. The signal on the mass block passes through the CV circuit and carrier demodulation in sequence, and the demodulated carrier signal is low-pass filtered to generate a quasi-static displacement signal. At the same time, the demodulated carrier signal is high-order secondary demodulated and then passed through a bandpass filter corresponding to the high-order mode to generate a high-order modal displacement signal. The displacement signals of each modal order after filtering by the multi-modal filter are fused as the final displacement signal, and the final displacement signal represents the magnitude of the acceleration.

[0020] Furthermore, the closed-loop acceleration detection method includes:

[0021] The controller calculates a feedback control voltage based on the difference between the final displacement signal obtained by open-loop acceleration detection and the reference displacement signal, and applies it to the first variable-area actuator and the second variable-area actuator on the left and right sides of the main mass block to generate a balancing force, so that the mass block is fixed at a preset reference position. The feedback control voltage represents the magnitude of the acceleration.

[0022] Furthermore, the power weighting method is used to fuse the filtered modal displacement signals of each order, specifically:

[0023] The square sum of the displacement signals of each order mode after filtering by the multimodal filter is calculated, and then the square root is calculated to obtain the final displacement signal.

[0024] Furthermore, the multimodal filter comprises a low-pass filter with a base frequency as the cut-off frequency and a band-pass filter corresponding to the frequency range of the high-order vibration mode;

[0025] The cutoff frequency of the low-pass filter is the same as the first cutoff frequency of the band-pass filter corresponding to the second-order mode, the first cutoff frequency of the band-pass filter corresponding to the m-order mode is the same as the second cutoff frequency of the band-pass filter corresponding to the m-1-order mode, and the second cutoff frequency of the band-pass filter corresponding to the m-order mode is the same as the first cutoff frequency of the band-pass filter corresponding to the m+1-order mode, and m≥3.

[0026] In general, the technical solution conceived by the present invention has the following beneficial effects compared with the prior art:

[0027] (1) The present invention, through the driving and structural design of the multi-modal micromechanical resonator system, can not only be used for traditional acceleration open-loop and closed-loop measurement methods, but also realize multi-modal working mode, with the advantages of simple structure, high integration, and miniaturization.

[0028] (2) The present invention can improve the acceleration detection accuracy and widen the acceleration detection bandwidth through the synchronous detection and data fusion of multi-modal displacement, thus achieving higher acceleration measurement performance.

[0029] (3) The present invention can simultaneously apply force balance closed-loop control and electrostatic adjustment technology to improve the linearity and accuracy of the micromechanical accelerometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is a schematic structural diagram of a two-mode micromechanical resonator system according to an embodiment of the present invention;

[0031] Figure 2 It is a schematic diagram of the first-order vibration mode (quasi-static) of a two-mode micromechanical resonator system;

[0032] Figure 3 It is a schematic diagram of the second-order vibration mode of the two-mode micromechanical resonator system;

[0033] Figure 4 It is a schematic diagram of the framework of displacement detection, fusion and closed-loop method based on a two-mode micromechanical resonator system;

[0034] In all the drawings, the same figure marks are used to represent the same structure, where: 1-first small stiffness elastic beam, 2-main mass block, 3-large stiffness elastic beam, 4-second mass block, 5-second small stiffness elastic beam, 6-first variable area type driver, 7-first variable spacing type capacitor, 8-variable spacing type driver, 9-second variable spacing type capacitor, 10-second variable area type driver. DETAILED DESCRIPTION

[0035] In order to more clearly express the purpose, technical solutions and advantages of the present invention, the following is a further explanation with reference to the accompanying drawings and formula derivations. It should be understood that the principles herein are used to explain the present invention, but are not limited to the present invention.

[0036] The invention is based on a multi-modal micromechanical resonator, the structure of which includes a movable micro-mass block, micro-elastic beams with different stiffnesses, variable-spacing displacement detection capacitors, variable-spacing drivers and variable-area drivers. Figure 11 is a schematic diagram of the structure of a typical two-mode micromechanical resonator system in an embodiment of the present invention, including a first low-rigidity elastic beam 1, a main mass block 2, a high-rigidity elastic beam 3, a second mass block 4, a second low-rigidity elastic beam 5, a variable-area driver 6, a variable-spacing capacitor 7, a variable-spacing driver 8, a variable-spacing capacitor 9, and a variable-area driver 10.

[0037] The elastic beam and mass form a two-modal mass-spring system that moves in the X-direction. The main mass and the second mass are rigid structures, connected by a high-stiffness elastic beam 3 and connected to the anchor structure by their own low-stiffness elastic beams. The fundamental resonant frequency is determined by the less-rigid elastic beam and the mass, while higher-order resonant frequencies are determined by the more-rigid elastic beam and the mass. Comb electrodes are distributed throughout the main mass 2, including first movable comb electrodes located on the left and right sides of the main mass, and second, third, and fourth movable comb electrodes located on the upper and lower sides of the main mass. Functionally, the first movable comb electrode is a variable-area drive electrode, the second and fourth movable comb electrodes are variable-pitch displacement detection electrodes, and the third movable comb electrode is a variable-pitch drive electrode. These movable comb electrodes, together with the corresponding fixed comb electrodes located on the anchor, form the variable-area actuator 6, variable-pitch capacitor 7, variable-pitch line actuator 8, variable-pitch capacitor 9, and variable-area actuator 10, respectively.

[0038] like Figure 4 As shown, when the micromechanical resonator is subjected to an acceleration below the fundamental frequency, the two masses synchronously generate approximately the same quasi-static displacement. By applying carrier signals with opposite phases to the variable-spacing capacitors 7 and 9 on the main mass, and extracting the response signals on the mass blocks through the C / V detection circuit, the displacement of the mass blocks can be detected. This displacement can be defined as the quasi-static modal detection displacement. At the same time, by applying a second-order modal vibration excitation signal to the variable-spacing actuator 8 on the main mass block, the electrodes on the main mass block generate a displacement that deviates from the center position of the variable-spacing actuator 8, generating a resonant driving force on the actuator that can cause second-order modal vibration. The magnitude of the resonant driving force is positively correlated with the distance of the main mass block from the center of the differential electrode. By extracting the response signals on the mass blocks, and subjecting them to carrier demodulation, secondary demodulation, and bandpass filtering, the displacement that deviates from the center position can be detected. This detected displacement can be defined as the second-order modal detection displacement. The second-order modal detection displacement is zero, that is, when the main mass block is at the center position of the variable-spacing actuator, the second-order modal driving force and response are both zero. Figure 2 and Figure 3 The first-order vibration mode (quasi-static) and second-order vibration mode of a two-modal micromechanical resonator system are shown.

[0039] The quasi-static modal detection displacement and the second-order modal detection displacement are processed by a low-pass filter and a band-pass filter after demodulation. On the one hand, high-frequency signals related to the carrier and the second-order excitation are filtered out. On the other hand, weight processing can be introduced for the two detection displacements in the frequency range. After power weighting, displacement information fused according to frequency characteristics can be obtained, that is, the quasi-static detection displacement weight in the low-frequency band is higher than the second-order detection displacement weight, and the quasi-static detection displacement weight in the high-frequency band is lower than the second-order detection displacement weight; the cutoff frequency of the low-pass filter is the same as the first cutoff frequency of the band-pass filter, and the second cutoff frequency of the band-pass filter determines the open-loop acceleration measurement bandwidth; this fusion method fully takes into account the high sensitivity of the quasi-static detection displacement method and the high bandwidth characteristics of the second-order detection displacement.

[0040] The multimodal displacement measurement of the present invention is to obtain the magnitude of each order of vibration by demodulating the response signal on the detection capacitor to satisfy the expression Where δ, μ, Q, k m ,V d ,V a , x are the vibration amplitude of the m-order mode, the driver constant, the quality factor, the elastic coefficient, the DC component and the AC component of the excitation signal applied by the variable pitch driver, and the displacement.

[0041] The closed-loop working mode of acceleration measurement is to compare the fused displacement with the set value, calculate the feedback control voltage through the controller, and apply it to the variable area drivers 6 and 10, so as to maintain the constant vibration amount, that is, the displacement of the main mass under the action of acceleration is constant. One typical closed-loop set value is zero, at this time the quasi-static displacement of the resonator is zero and the second-order vibration is zero.

[0042] The variable pitch driver 8 is a differential structure, which can drive the main mass block to generate second-order resonance and generate electrostatic negative stiffness, thereby reducing the fundamental frequency of the resonator and improving the quasi-static detection sensitivity.

[0043] In addition to the two-mode micromechanical resonator system shown in the above embodiment, other high-order forms can also be used, which must meet the requirements of a multi-modal mass-spring system and driver moving along a single axis direction composed of multiple mass blocks and elastic beams, where the multiple mass blocks are connected by high-rigidity elastic beams, and at the same time, the multiple mass blocks are each connected to the anchor area by a low-rigidity elastic beam; a variable-area driver 6, a variable-spacing capacitor 7, a variable-spacing driver 8, and a variable-spacing capacitor 9 are distributed on one of the main mass blocks.

[0044] The final displacement signal is obtained by fusing the displacement signals of each modal order after filtering by a multimodal filter. The final displacement signal represents the magnitude of acceleration. The multimodal filter comprises a low-pass filter with a base frequency as the cutoff frequency and a band-pass filter corresponding to the frequency range of the higher-order vibration modes.

[0045] The cutoff frequencies of the low-pass filter and the band-pass filter corresponding to the second-order mode are the same, and the cutoff frequencies of the band-pass filters corresponding to the second-order and higher-order modes satisfy the following relationship: the first cutoff frequency of the band-pass filter corresponding to the m-order mode is the same as the second cutoff frequency of the band-pass filter corresponding to the m-1-order mode, and at the same time, the second cutoff frequency of the band-pass filter corresponding to the m-order mode is the same as the first cutoff frequency of the band-pass filter corresponding to the m+1-order mode.

[0046] When fusing the displacement signals of each modal order after filtering by the multimodal filter, the power weighting method is used. After each modal displacement is processed by the corresponding filter, the square sum of the filtered modal displacements is calculated, and then the square root is calculated to obtain the final displacement.

[0047] This invention employs a uniaxial multimodal resonator system, utilizing multiple vibration modes to synchronously detect the displacement caused by uniaxial acceleration. A filter is then designed to weight the displacement measurements at each order. This weighted fusion process yields the final displacement of the mass caused by acceleration. In an open-loop system, this displacement directly represents the magnitude of the acceleration. In a closed-loop system, the feedback control voltage that maintains this displacement constant represents the magnitude of the acceleration. This invention effectively suppresses common-mode error and temperature drift while expanding bandwidth.

[0048] Those skilled in the art should understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-mode micromechanical resonator system, characterized in that: A multi-modal mass-spring system and a capacitor moving along a single axis, comprising a plurality of mass blocks and elastic beams, wherein the plurality of mass blocks are connected to each other via elastic beams having high stiffness, and each of the plurality of mass blocks is connected to an anchoring area via elastic beams having low stiffness; Mobile comb-tooth electrodes are distributed on a main mass block among the multiple mass blocks, including first mobile comb-tooth electrodes arranged on the left and right sides of the main mass block, and second, third, and fourth mobile comb-tooth electrodes arranged on the upper and lower sides of the main mass block; the direction of the first mobile comb-tooth electrode is the same as the direction of movement of the main mass block, and the directions of the second, third, and fourth mobile comb-tooth electrodes are perpendicular to the direction of movement of the main mass block; The first movable comb-tooth electrode on the left side and the fixed comb-tooth electrode fixed in the anchor area on the left side of the main mass block form a first variable area type driver (6); the first movable comb-tooth electrode on the right side and the fixed comb-tooth electrode fixed in the anchor area on the right side of the main mass block form a second variable area type driver (10); the second movable comb-tooth electrode, the third movable comb-tooth electrode and the fourth movable comb-tooth electrode on the upper and lower sides respectively form a first variable pitch type capacitor (7), a variable pitch type driver (8) and a second variable pitch type capacitor (9) with the corresponding fixed comb-tooth electrodes fixed in the anchor areas on the upper and lower sides of the main mass block.

2. The multi-mode micromechanical resonator system according to claim 1, characterized in that: The large-rigidity elastic beam and the small-rigidity elastic beam are arranged in parallel along the uniaxial motion direction, and the rigidity of the large-rigidity elastic beam is much greater than that of the small-rigidity elastic beam.

3. The multi-mode micromechanical resonator system according to claim 1, characterized in that: The variable pitch driver (8) is a differential structure, and is used to drive the main mass block to generate high-order resonance and electrostatic negative stiffness.

4. An acceleration measurement method based on multimodal micromechanical detection, implemented using the multimodal micromechanical resonator system of claim 1, characterized in that: When a multi-modal micromechanical resonator system is subjected to an acceleration lower than a fundamental frequency, multiple mass blocks synchronously generate approximate displacements, and open-loop and closed-loop acceleration detection are respectively realized by detecting the displacement of a main mass block or maintaining a constant position of the main mass block, wherein a feedback control voltage of the closed-loop acceleration detection is applied to a first variable area driver (6) and a second variable area driver (10); The multi-modal micromechanical resonator system generates high-order vibration modes under high-frequency excitation. In the high-order vibration modes, the vibration amplitude of the main mass block is positively correlated with the displacement of the main mass block. The displacement of the main mass block is synchronously measured by demodulating the vibration amplitude.

5. The acceleration measurement method based on multimodal micromechanical detection according to claim 4, characterized in that: The relationship between the vibration amplitude of the main mass block and the displacement of the main mass block is as follows: Where δ is the vibration amplitude of the main mass block, x is the displacement of the main mass block, μ and Q are the variable spacing actuator constant and quality factor, respectively, and k m is the m-order modal elastic coefficient, V d V is the DC component of the excitation signal applied by the variable pitch driver. a It is the AC component of the excitation signal applied to the variable pitch driver.

6. The acceleration measurement method based on multimodal micromechanical detection according to claim 4, characterized in that: Open-loop acceleration detection methods include: Carrier signals with opposite phases are applied to the first variable pitch capacitor (7) and the second variable pitch capacitor (9), and a high-order modal resonance excitation signal is applied to the variable pitch driver (8); the signal on the mass block passes through a CV circuit and carrier demodulation in sequence, the demodulated carrier signal is subjected to low-pass filtering to generate a quasi-static displacement signal, and the demodulated carrier signal is subjected to high-order secondary demodulation and then passed through a bandpass filter corresponding to the high-order mode to generate a high-order modal displacement signal, and the displacement signals of each order modal filtered by the multi-modal filter are fused as a final displacement signal, wherein the final displacement signal represents the magnitude of acceleration.

7. The acceleration measurement method based on multimodal micromechanical detection according to claim 6, characterized in that: Closed-loop acceleration detection methods include: The controller calculates a feedback control voltage based on the difference between a final displacement signal obtained by open-loop acceleration detection and a reference displacement signal, and applies the feedback control voltage to a first variable-area driver (6) and a second variable-area driver (10) on the left and right sides of the main mass block to generate a balancing force, thereby fixing the mass block at a preset reference position. The feedback control voltage represents the magnitude of acceleration.

8. The acceleration measurement method based on multimodal micromechanical detection according to claim 6, characterized in that: The power weighting method is used to fuse the filtered modal displacement signals of each order, specifically: The square sum of the displacement signals of each order mode after filtering by the multimodal filter is calculated, and then the square root is calculated to obtain the final displacement signal.

9. The acceleration measurement method based on multimodal micromechanical detection according to claim 6, characterized in that: The multimodal filter comprises a low-pass filter with a base frequency as the cut-off frequency and a band-pass filter corresponding to the frequency range of the high-order vibration mode; The cutoff frequency of the low-pass filter is the same as the first cutoff frequency of the band-pass filter corresponding to the second-order mode, the first cutoff frequency of the band-pass filter corresponding to the m-order mode is the same as the second cutoff frequency of the band-pass filter corresponding to the m-1-order mode, and the second cutoff frequency of the band-pass filter corresponding to the m-order mode is the same as the first cutoff frequency of the band-pass filter corresponding to the m+1-order mode, and m≥3.

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