Resonant accelerometer with double-ended fixed tuning fork structure

Abstract

This application provides a resonant accelerometer with a double-ended fixed tuning fork structure, comprising: a substrate; an anchoring platform disposed above the substrate, with an anchoring part in the middle of the anchoring platform and the anchoring part connected to the substrate; a mass block connected to the anchoring platform via a cantilever support assembly, the cantilever support assembly suspending the mass block above the substrate; an acceleration detection assembly including a resonant unit; and a force transmission assembly connecting the mass block and the resonant unit, the force transmission assembly transmitting the X-axis displacement generated by the mass block under acceleration to the resonant unit to change the Y-axis vibration frequency of the resonant unit; wherein, the resonant unit includes a tuning fork-shaped resonant beam, the tuning fork-shaped resonant beam including a first resonant beam and a second resonant beam arranged parallel and spaced apart, and a coupling beam connecting the two ends of the first resonant beam and the second resonant beam, the tuning fork-shaped resonant beam being connected to the force transmission assembly and the anchoring platform respectively through the coupling beams at both ends, and the Y-axis vibration frequency of the resonant unit being used to determine the acceleration.

Description

Technical Field

[0001] This application relates to the field of microelectromechanical systems (MEMS) technology, and in particular to a resonant accelerometer with a double-ended fixed tuning fork structure. Background Technology

[0002] Resonant accelerometers have significant applications in inertial navigation, precision instruments, and earthquake monitoring due to their advantages such as direct frequency signal output, strong anti-interference capability, and large dynamic range. The working principle of a resonant accelerometer is to utilize the inertial force caused by acceleration to change the stress state of the resonant structure, thereby modulating its inherent resonant frequency and achieving a highly sensitive conversion from acceleration to frequency.

[0003] However, in practical applications, traditional resonant accelerometers have poor zero-bias stability and zero-bias temperature stability of the resonant structure, are easily affected by environmental temperature drift, have large energy losses, and have a low quality factor (Q value). This can easily lead to smaller amplitudes under the same driving force and insufficient signal-to-noise ratio of the detected signal, thus affecting their practical applicability. Summary of the Invention

[0004] To address the existing technical problems, this application provides a resonant accelerometer with a double-ended fixed tuning fork structure that can effectively improve zero-bias stability and enhance the signal-to-noise ratio of the detection signal.

[0005] This application provides a resonant accelerometer with a double-ended fixed tuning fork structure, comprising: Substrate; An anchoring platform is disposed above the substrate, and the anchoring platform is connected to the substrate through an anchoring part; A mass block is connected to the anchoring platform via a cantilever support assembly, which suspends the mass block above the substrate. Acceleration detection components, including a resonant unit; A force transmission component connects the mass block and the resonant unit. The force transmission component transmits the X-axis displacement generated by the mass block under acceleration to the resonant unit, thereby changing the Y-axis vibration frequency of the resonant unit. The resonant unit includes a tuning fork-shaped resonant beam, which includes a first resonant beam and a second resonant beam arranged in parallel and spaced apart, and a coupling beam connecting the two ends of the first resonant beam and the second resonant beam. The tuning fork-shaped resonant beam is connected to the force transmission component and the anchoring platform through the coupling beams at both ends, respectively. The Y-axis vibration frequency of the resonant unit is used to determine the acceleration.

[0006] In the above embodiments, the resonant accelerometer with a double-ended fixed tuning fork structure includes a tuning fork-shaped resonant beam in the acceleration detection component. The tuning fork-shaped resonant beam includes a first and a second resonant beam arranged parallel and spaced apart, and a coupling beam connecting the two ends of the first and second resonant beams. The tuning fork-shaped resonant beam is connected to a force transmission component and an anchoring platform respectively through the coupling beams at both ends. The force transmission component transmits the X-axis displacement generated by the mass block under acceleration to the resonant unit, thereby changing the Y-axis vibration frequency of the resonant unit. The Y-axis vibration frequency of the resonant unit is used to determine... With constant acceleration, the anti-phase motion of the first and second resonant beams in the tuning fork resonant beam can effectively reduce system energy loss and improve the Q value. The high Q value results in a larger amplitude under the same driving force, enhancing the signal-to-noise ratio of the capacitor detection signal. Secondly, the differential output of the first and second resonant beams in the tuning fork resonant beam can cancel common-mode interference and significantly improve zero-bias stability. Thus, through the design optimization of the tuning fork resonant beam, it can be ensured that the frequency difference between in-phase and out-of-phase modes is always greater than 1kHz within the range, effectively avoiding inter-mode interference and eliminating the influence of other stray modes. Attached Figure Description

[0007] Figure 1 This is a top view of a resonant accelerometer with a double-ended fixed tuning fork structure provided in one embodiment.

[0008] Figure 2 for Figure 1 A three-dimensional view of a resonant accelerometer with a double-ended fixed tuning fork structure.

[0009] Figure 3 for Figure 1 The diagram shows a three-dimensional cross-sectional view of a resonant accelerometer with a double-ended fixed tuning fork structure.

[0010] Figure 4 This is a schematic diagram of the structure of a cantilever support assembly provided in one embodiment.

[0011] Figure 5 for Figure 4 The displacement distribution diagram of the cantilever support assembly is shown.

[0012] Figure 6 This is a schematic diagram of the force transmission component provided in one embodiment.

[0013] Figure 7 for Figure 6 A schematic diagram of the lever section in the force transmission assembly shown.

[0014] Figure 8 for Figure 7 The diagram shows the displacement distribution of the lever section.

[0015] Figure 9This is a schematic diagram of the structure of the resonant unit in the acceleration detection component in one embodiment.

[0016] Figure 10 This is a schematic diagram of the acceleration detection component in one embodiment.

[0017] Figure 11 for Figure 10 The diagram shows the in-phase vibration displacement distribution of the resonant unit in the acceleration detection component.

[0018] Figure 12 for Figure 10 The diagram shows the anti-phase vibration displacement distribution of the resonant unit in the acceleration detection component.

[0019] Figure 13 This is a diagram showing the axial sensitive modal displacement distribution of a resonant accelerometer with a double-ended fixed tuning fork structure in one embodiment.

[0020] Figure 14 This is a schematic diagram of the acceleration detection component in another embodiment.

[0021] Figure 15 for Figure 14 The diagram shows the structure of the tuning fork resonant beam in the acceleration detection component.

[0022] Figure 16 for Figure 14 The diagram shows the in-phase vibration displacement distribution of the resonant unit in the acceleration detection component.

[0023] Figure 17 for Figure 14 The diagram shows the anti-phase vibration displacement distribution of the resonant unit in the acceleration detection component.

[0024] Figure 18 This is a top view of a resonant accelerometer with a double-ended fixed tuning fork structure in another embodiment.

[0025] Figure 19 This is a top view of a resonant accelerometer with a double-ended fixed tuning fork structure in another embodiment. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] In the following description, the phrase "some embodiments" refers to a subset of all possible embodiments. It should be noted that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0029] In the following description, the terms "first, second, and third" are used merely to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first, second, and third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0030] In the design process of the micromechanical accelerometer, the inventors of this application conducted the following research to address the shortcomings of existing micromechanical accelerometers: Micromechanical accelerometers use resonant units as the acceleration sensing element, primarily constructed through deep silicon etching. However, traditional micromechanical accelerometers with known resonant structures often suffer from various limitations in practical applications: firstly, the zero-bias stability and zero-bias temperature stability of the resonant structure are poor, making them susceptible to environmental temperature drift interference; secondly, they suffer from high energy loss and a low quality factor (Q value), easily leading to smaller amplitudes under the same driving force and insufficient signal-to-noise ratio (SNR) of the detection signal. In view of this, the inventors of this application propose a tuning fork resonant beam design. By utilizing the dual resonant beams operating in anti-phase mode within the tuning fork resonant beam, the system energy loss is significantly reduced, and the Q value is increased. The higher Q value results in larger amplitudes under the same driving force, enhancing the SNR of the capacitive detection signal. The differential output of the dual resonant beams can cancel common-mode interference (such as environmental temperature drift interference), significantly improving zero-bias stability and zero-bias temperature stability.

[0031] Please see Figure 1 and Figure 2One embodiment of this application provides a resonant accelerometer with a double-ended fixed tuning fork structure, comprising: a substrate 10; an anchoring platform 20 disposed above the substrate 10, wherein an anchoring portion 21 is provided in the middle of the anchoring platform 20 and the anchoring portion 21 is connected to the substrate 10; a mass block 50 connected to the anchoring platform 20 via a cantilever support assembly 40, wherein the cantilever support assembly 40 suspends the mass block 50 above the substrate 10; an acceleration detection assembly 70 including a resonant unit 703; and a force transmission assembly 60 connecting the mass block 50 and the resonant unit 703. The force transmission component 60 transmits the X-axis displacement generated by the mass block 50 under acceleration to the resonant unit 70 to change the Y-axis vibration frequency of the resonant unit 70. The resonant unit 703 includes a tuning fork-shaped resonant beam, which includes a first resonant beam and a second resonant beam arranged in parallel and spaced apart, and a coupling beam connecting the two ends of the first resonant beam and the second resonant beam. The tuning fork-shaped resonant beam is connected to the force transmission component 60 and the anchoring platform 20 through the coupling beams at both ends, respectively. The Y-axis vibration frequency of the resonant unit 703 is used to determine the acceleration.

[0032] During the operation of the resonant accelerometer, the mass block 50 generates X-axis displacement under the action of acceleration. The force transmission component 60 transmits the X-axis displacement of the mass block 50 to the resonant unit 703 to change the Y-axis vibration frequency of the resonant unit 703. The acceleration is determined based on the vibration frequency of the resonant unit 703.

[0033] The substrate 10 serves as the supporting structure for the electrically isolated resonant micromechanical accelerometer. Anchoring platform 20 is located above substrate 10. Anchoring portion 21 and anchoring platform 20 are situated on the same structural layer. Anchoring platform 20 is connected to substrate 10 via anchoring portion 21, forming a rigid platform structure suspended above substrate 10. In this embodiment, anchoring portion 21 is a single-point anchoring region located at the geometric center of anchoring platform 20. The planar area of ​​anchoring platform 20 is not less than five times the planar area of ​​anchoring portion 21. The single-point anchoring portion 21 on anchoring platform 20 avoids uneven mechanical stress distribution. During temperature changes, the overall structure of the electrically isolated resonant micromechanical accelerometer can thermally expand almost freely within the plane, uniformly releasing thermal stress, reducing zero-bias temperature drift, and minimizing zero-bias error. Furthermore, it overcomes the structural asymmetry introduced by the manufacturing process tolerance of multi-anchor-point architectures, resulting in greater overall rigidity of anchoring platform 20 and more effective isolation of external mechanical strain.

[0034] Please see Figure 3 The substrate 10 includes a support base 11 and a support column 12 disposed on the support base 11. The support column 12 is connected between the anchoring part 21 and the substrate 10. The anchoring platform 20 is anchored to the substrate 10 only through the support column 12, and is suspended above the substrate 10.

[0035] In the above embodiment, the resonant accelerometer with a double-ended fixed tuning fork structure includes a tuning fork-shaped resonant beam in the acceleration detection component 70. The tuning fork-shaped resonant beam includes a first and a second resonant beam arranged parallel and spaced apart, and a coupling beam connecting the two ends of the first and second resonant beams. The tuning fork-shaped resonant beam is connected to the force transmission component 60 and the anchoring platform 20 respectively through the coupling beams at both ends. The force transmission component 60 transmits the X-axis displacement generated by the mass block 50 under acceleration to the resonant unit 703, thereby changing the Y-axis vibration frequency of the resonant unit 703. The Y-axis vibration frequency of 3 is used to determine the acceleration. The anti-phase motion of the first and second resonant beams in the tuning fork resonant beam can effectively reduce system energy loss and improve the Q value. The high Q value results in a larger amplitude under the same driving force, which enhances the signal-to-noise ratio of the capacitor detection signal. Secondly, the differential output of the first and second resonant beams in the tuning fork resonant beam can cancel common-mode interference and significantly improve zero-bias stability. Thus, through the design optimization of the tuning fork resonant beam, it can be ensured that the frequency difference between the in-phase and out-of-phase modes is always greater than 1kHz within the range, effectively avoiding inter-mode interference and eliminating the influence of other stray modes.

[0036] In some embodiments, the mass block 50 is arranged around the periphery of the anchoring platform 20; multiple cantilever support assemblies 40 are symmetrically arranged on opposite sides of the anchoring platform 20. The anchoring platform 20 and the mass block 50 are arranged at inner and outer intervals, and multiple cantilever support assemblies 40 are located on the outer periphery of the anchoring platform 20, connecting the anchoring platform 20 and the mass block 50. Each cantilever support assembly 40 can be various known beam structures, such as straight beams, bent beams, or folded beams. In this embodiment, there are four cantilever support assemblies 40, respectively located at the four corners of the outer periphery of the anchoring platform 20. The mass block 50 has corresponding notches at the positions of the cantilever support assemblies 40, and the cantilever support assemblies 40 are located within the notches and connected between the anchoring platform 20 and the mass block 50.

[0037] Please refer to the following: Figure 4 and Figure 5Each cantilever support assembly 40 includes anchor beams 41 and movable beams 42 spaced apart from each other, a node beam 43 connecting one end of the anchor beams 41 and movable beams 42, and an output beam 44 extending outward from the end of the movable beam 42 away from the node beam 43. The anchor beams 41 and movable beams 42 extend along the Y-axis, the end of the anchor beam 41 away from the node beam 43 is connected to the anchoring platform 20, and the output beam 44 is connected to the mass block 50. There can be one or more anchor beams 41 and movable beams 42, which are arranged parallel and spaced apart. The node beam 43 connects the same end of the anchor beams 41 and movable beams 42, forming a U-shape. In this embodiment, there are two anchor beams 41 and two movable beams 42. The movable beams 42 are arranged outside the anchor beams 41. The output beams 44 bend outward from the end of the movable beams 42 away from the node beams 43. The two middle anchor beams 41 are connected to the anchoring platform 20, and the two output beams 44 on both sides extend vertically outward from the ends of the movable beams 42. The output beams 44 are parallel to the node beams 43 and are connected to the mass blocks 50 respectively. When an axial acceleration is input, the displacement distribution of the cantilever support assembly 40 is as follows: Figure 5 As shown, the displacement response at the location of the output beam 44, which is directly connected to the mass block 50, is the maximum value, while the displacement response at the end of the anchor beam 41, which is connected to the anchoring platform 20, transmitted to the anchoring platform 20 through the cantilever support assembly 40, is the minimum value. Therefore, the cantilever support assembly 40 allows the mass block 50 to be suspended relative to the substrate 10 and controls the sensitive axis direction of the mass block 50, which is the X-axis. Under the same acceleration, the displacement response of the mass block 50 along the X-axis is much greater than that along the Y-axis.

[0038] The mass block 50 is connected to the anchoring platform 20 via the cantilever support assembly 40 and is configured to generate a displacement response along the X-axis under the action of acceleration in the X-axis direction. This displacement is converted into an axial force by the force transmission assembly 60 and transmitted to the acceleration detection assembly 70.

[0039] In some embodiments, the acceleration detection component 70 includes a first acceleration detection component 71 and a second acceleration detection component 72 symmetrically disposed on both sides of the anchoring portion 21; each acceleration detection component 70 further includes an electrode group 704 corresponding to the resonant unit 703. The resonant unit 703 includes a tuning fork-shaped resonant beam, and the electrode group 704 includes two electrode groups respectively corresponding to the first resonant beam 711 and the second resonant beam 712 in the tuning fork-shaped resonant beam. Each electrode group includes a driving electrode 7041 and a detection electrode 7042. For the first resonant beam 711 and the second resonant beam 712, the sum of the effective facing areas of the detection electrode 7042 and its corresponding electrode is greater than the sum of the effective facing areas of the driving electrode 7041 and its corresponding electrode. The first resonant beam 711 and the second resonant beam 712 extend along the X-axis direction, and the electrode group 704 is disposed on both sides of the corresponding resonant beam and parallel to it. The electrode group 704 and the resonant unit 703 constitute a variable capacitor structure.

[0040] Please refer to the following: Figure 6 and Figure 7 The force transmission component 60 includes a first force transmission component 61 corresponding to the first acceleration detection component 71 and a second force transmission component 62 corresponding to the second acceleration detection component 72. Each force transmission component 60 includes a resonant beam support 601 and two levers 602 connected to both ends of the resonant beam support 601. Each lever 602 includes a lever arm 6021, a lever input beam 6022, a lever output beam 6023, and a lever anchoring beam 6024 disposed on the lever arm 6021. The lever anchoring beam 6024 connects the lever arm 6021 to the resonant beam support 601, the lever input beam 6022 connects the lever arm 6021 to the mass block 50, and the lever output beam 6023 connects the lever arm 6021 to the anchoring platform 20. Taking the first force transmission component 61 as an example, ... Figure 6 As shown, the first force transmission component 61 includes two symmetrically arranged lever parts 602 and a resonant beam support part 601. Figure 7As shown, each lever portion 602 includes a lever arm 6021 constituting the main body of the lever portion 602. The lever input beam 6022, lever output beam 6023, and lever anchoring beam 6024 are all located on the same side of the lever arm 6021 (the same side in the Y-axis direction). Specifically, the lever portion 602 and the resonant beam support portion 601 are arranged along the Y-axis direction. The lever input beam 6022 and the lever output beam 6023 are located at opposite axial ends of the lever arm 6021. The lever input beam 6022 is connected to the mass block 50, and the lever output beam 6023 is connected to the resonant beam support platform. The resonant beam support platform serves as a transition structure between the lever portion 602 and the resonant unit 703 in the acceleration detection assembly 70. In each force transmission assembly 60, the two lever portions 602 are symmetrically arranged, which can counteract Y-axis displacement and avoid applying additional Y-axis force to the resonant unit 703. The lever anchor beam 6024 is positioned between the lever input beam 6022 and the lever output beam 6023 along the length of the lever arm 6021, i.e. along the Y-axis, and is fixed by the anchoring platform 20. The width of the lever arm 6021 is significantly greater than the widths of the lever input beam 6022, the lever anchor beam 6024, and the lever output beam 6023.

[0041] When an axial acceleration is input, the displacement of the lever 602 is as follows: Figure 8 As shown, the X-axis displacement of mass block 50 is converted into an axial force acting on the resonant beam support platform. The formula for calculating the magnitude of the axial force transmitted from the X-axis displacement to the resonant unit 703 by force transmission component 60 is shown in Formula 1 below: (Formula 1) Among them, F out L represents the magnitude of the axial force. in The distance L between the lever anchor beam 6024 and the lever input beam 6022 out The distance L between the lever anchor beam 6024 and the lever output beam 6023 is specified. In the force transmission assembly 60, the structural design of the lever portion 602 amplifies the force by adjusting the distance L between the lever anchor beam 6024 and the lever input beam 6022. in The distance L between the lever anchor beam 6024 and the lever output beam 6023. out It can change the magnitude of the axial force applied to the resonant unit 703 in the acceleration detection component 70.

[0042] The first acceleration detection component 71 and the second acceleration detection component 72 are arranged symmetrically with respect to the anchoring part 21. Please refer to the following reference. Figures 9 to 12Taking the first acceleration detection component 71 as an example, the first resonant beam 711 and the second resonant beam 712 in the tuning fork resonant beam are both composite beams. The composite beam includes a main beam, two secondary beams located on both sides of the main beam and parallel to the main beam, and a central boss connecting the main beam and the secondary beams. The two ends of the main beams of the first resonant beam 711 and the second resonant beam 712 are connected by coupling beams. In the first resonant beam 711 and the second resonant beam 712, the coupling beam at the first end of the main beam along the X-axis is fixed to the anchoring platform 20, and the coupling beam at the second end is connected to the mass block 50 through the force transmission component 60. The electrode group 704 is correspondingly set with the secondary beams. The driving electrode 7041 is located at the center of the corresponding secondary beam, and the detection electrode 7042 is located at both ends of the corresponding secondary beam. The sum of the effective facing areas of the detection electrode 7042 and the corresponding secondary beam is greater than the sum of the effective facing areas of the driving electrode 7041 and the corresponding secondary beam.

[0043] like Figure 9 As shown, the first resonant beam 711 includes a first main beam 7031, a first secondary beam 7032 disposed on both sides of the first main beam 7031 and parallel to the first main beam 7031, and a central boss 7034 connecting the first main beam 7031 and the first secondary beam 7032; the opposite ends of the first main beam 7031 are respectively connected to the force transmission component 60 and the anchoring platform 20 through coupling beams 7036. The second resonant beam 712 includes a second main beam 7037, a second secondary beam 7038 disposed on both sides of the second main beam 7037 and parallel to the second main beam 7037, and a central boss 7034 connecting the second main beam 7037 and the second secondary beam 7038; the opposite ends of the second main beam 7037 are respectively connected to the force transmission component 60 and the anchoring platform 20 through coupling beams 7036. Figure 10As shown, the resonant unit 703 further includes a first comb tooth portion 7033 disposed on the sub-beam. The first comb tooth portion 7033 includes a plurality of first teeth 7035 extending outward from the corresponding sub-beam along the Y-axis direction and arranged at intervals along the length direction of the corresponding sub-beam. The electrode group 704 includes a second comb tooth portion 7043 corresponding to the first comb tooth portion 7033. The second comb tooth portion 7043 includes second teeth 7045 that are staggered and spaced apart from the first teeth 7035. The second comb tooth portion 7043 on the detection electrode 7042 corresponds to the first comb tooth portion 7033 at both ends of the corresponding sub-beam, and the second comb tooth portion 7043 on the driving electrode 7041 corresponds to the first comb tooth portion 7033 in the middle of the corresponding sub-beam. In this embodiment, the first resonant beam 711 and the second resonant beam 712 in the resonant unit are both formed as composite structures, and their central regions are configured with a comb tooth array composed of a plurality of first teeth 7035. The aspect ratio of the first main beam 7031 and the second main beam 7037 is ≥80:1. The comb array consists of at least 10 (N≥10) thin beams arranged periodically along the X-axis. Each thin beam's length is along the Y-axis, with an aspect ratio ≥5:1. The spacing between adjacent thin beams (i.e., adjacent first teeth 7035) is 5~20 μm. The comb array is fixed to corresponding secondary beams, thus the secondary beams can serve as the ridges of multiple first teeth 7035. The ridges are connected to the central boss 7034 of the corresponding main beam. Sliding comb arrays are arranged on both opposite sides of the resonant beam. The vibration displacement distribution of the resonant unit is as follows... Figure 11 and Figure 12 As shown.

[0044] The resonant frequency f0 of the resonant unit 703 can be calculated using the following formula: (Formula 2) Wherein, keff is the effective stiffness of the resonant unit 703, which is related to the dimensional parameters of the resonant beam (thickness t, width w, length l) and is modulated by the axial external force Fx. It should be noted that the axial external force here refers to the magnitude F of the axial force F that the force transmission component 60 transmits the X-axis displacement to the resonant unit 703. out When the resonant beam is subjected to tensile axial force, keff increases (positive in Formula 2); when subjected to compressive axial force, keff decreases (negative in Formula 2). meff is the effective mass, which is related to the size parameters of the resonant beam, the material density ρ, and the total top-view projected area Sc of the resonant beam (first main beam 7031, central boss 7034, comb ridge and comb tooth array).

[0045] Mass block 50 is a single integral structure, and changes in its axial displacement generate axial forces that act synchronously on all resonant units 703. The displacement distribution of the axially sensitive modes of mass block 50 is as follows: Figure 13As shown, the length changes of the resonant unit 703 in the first acceleration detection component 71 and the resonant unit 703 in the second acceleration detection component 72 are always opposite, thus causing their resonant frequencies to change in opposite directions. The frequencies of the resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72 are subtracted, and the resonant frequency difference is used in conjunction with the axial input acceleration. a in Establish a connection. The acceleration calculation formula, based on the vibration frequency of the resonant unit 703, is shown in Formula 3 below: (Formula 3) Where λ represents the sensitivity coefficient. λ1 is the sensitivity coefficient of the resonant unit 703 in the first acceleration detection component 71, λ2 is the sensitivity coefficient of the resonant unit 703 in the second acceleration detection component 72, f01 is the resonant frequency of the resonant unit 703 in the first acceleration detection component 71, f02 is the resonant frequency of the resonant unit 703 in the second acceleration detection component 72, and Δ f For the resonant frequency difference, a in It is acceleration.

[0046] By characterizing the resonant frequency difference Δf between the resonant unit 703 in the first acceleration detection component 71 and the resonant unit 703 in the second acceleration detection component 72, the sensitivity to acceleration can be improved, the second-order nonlinear coefficient can be reduced, and common-mode errors such as residual stress and temperature drift can be eliminated.

[0047] When there is no acceleration input and the resonant frequencies of the two resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72 are similar, a zero-position self-locking phenomenon is likely to occur. That is, when the input axial acceleration is small, the differential frequency Δf hardly changes with the input acceleration. In some embodiments, during the design phase, a resonant frequency difference is created between the two resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72, thereby shifting the self-locking region (dead zone) to the non-working area or low-probability area of ​​the input acceleration range.

[0048] In each acceleration detection component 70, electrode groups 704 are disposed on both sides of the corresponding resonant beam, forming a variable capacitor structure with the resonant beam. For example... Figure 11In the resonant unit 703, which is equipped with a sliding diaphragm comb tooth array (first comb tooth portion 7033), the electrode group 704 has periodically arranged finger-like / comb-like fine beams (second comb tooth portion 7043), which are arranged in an alternating parallel configuration with the comb tooth fine beams of the resonant unit 703 to realize the sliding diaphragm damping drive and detection functions. For ease of description, the comb tooth fine beams in the resonant unit 703 are referred to as the first tooth 7035, and the comb teeth of the electrode group 704 are referred to as the second tooth 7045. The electrode gap 705 between the second tooth 7045 of the electrode group 704 and the first tooth 7035 of the resonant unit 703 is formed by deep reactive ion etching process. The width of the electrode gap 705 is in the range of 2~4 μm, the aspect ratio is ≥20:1, the sidewall perpendicularity deviation of the tooth is ≤1°, and the dimensional standard deviation of the electrode gap 705 is within the range of ±0.3 μm.

[0049] The electrode group 704 adopts differential driving and differential detection. Accordingly, the driving electrode 7041 includes a positive driving electrode and a negative driving electrode respectively disposed on opposite sides of the middle of the resonant beam; the detection electrode 7042 includes two groups, respectively disposed at both ends of the resonant beam, and each group of detection electrodes 7042 includes a positive detection electrode and a negative detection electrode respectively disposed on opposite sides of the resonant beam.

[0050] by Figure 10 Taking the comb array as an example, the positive and negative driving electrodes are the positive and negative terminals of the sliding diaphragm driving electrode, respectively. The driving electrical signals applied to the positive and negative terminals of the sliding diaphragm driving electrode are out of phase, forming a differential driving electrode pair. These differential driving electrode pairs are located on opposite sides of the center line of the resonant beam. Similarly, the positive and negative detection electrodes are the positive and negative terminals of the sliding diaphragm detection electrode, respectively. The detection electrical signals extracted from the positive and negative terminals of the sliding diaphragm detection electrode are out of phase, forming a differential detection electrode pair. These differential detection electrode pairs are located on opposite sides of both ends of the resonant beam. The total number of comb teeth / electrode beams in the differential detection electrode pair is greater than the total number of comb teeth / electrode beams in the differential driving electrode pair.

[0051] Please refer to the following: Figures 14 to 17Taking the resonant unit 703 using a pressure-film vibrating beam as an example, in the resonant unit 703, the first resonant beam 711 and the second resonant beam 712 are both single beams. The resonant unit also includes movable electrodes disposed on the single beams. The electrode group 704 is configured as a structure of multiple electrode pairs arranged parallel to and opposite to the resonant beams of the single beam structure to realize the driving and detection of the pressure-film damping. In a specific example, the driving electrode 7041 includes a positive driving electrode disposed between the two single beams and negative driving electrodes disposed on the outside of the two single beams and corresponding to the position of the positive driving electrode; the detection electrode 7042 includes a positive detection electrode disposed between the two single beams and negative detection electrodes disposed on the outside of the two single beams and corresponding to the position of the positive detection electrode.

[0052] The micron-level gap 7039 between the electrode assembly 704 and the resonant unit 703 is formed using deep reactive ion etching. The width of this micron-level gap 7039 ranges from 2 to 4 μm, the aspect ratio is ≥20:1, the sidewall verticality deviation is ≤1°, and the dimensional standard deviation of the micron-level gap 7039 is ≤0.3 μm. The electrode assembly 704 employs differential driving and differential detection. The driving electrode 7041 includes a positive driving electrode and a negative driving electrode located on opposite sides of the middle of the resonant beam of the single-beam structure. The positive driving electrode and the negative driving electrode are respectively the positive and negative electrodes of the pressure-film driving electrode. The driving electrical signals applied to the positive and negative electrodes of the pressure-film driving electrode are out of phase, forming a differential driving electrode pair. The detection electrodes 7042 comprise two sets, respectively located at both ends of the resonant beam. Each set of detection electrodes 7042 includes a positive detection electrode and a negative detection electrode located on opposite sides of the resonant beam. The positive and negative detection electrodes are respectively the positive and negative terminals of the pressure film detection electrode. The detection signals extracted by the positive and negative terminals of the pressure film detection electrode are out of phase, forming a differential detection electrode pair. Each differential driving electrode pair is located on both sides of the resonant beam. The total effective facing area of ​​the differential detection electrode pair and the resonant beam is greater than the total effective facing area of ​​the differential driving electrode pair and the resonant beam. Compared to the sliding film drive-detection scheme, the pressure film drive-detection scheme directly controls the resonant frequency by adjusting the voltage difference between the electrode set 704 and the resonant beam, making it easier to compensate for or balance the effects caused by non-ideal factors such as process errors and residual stress.

[0053] In some embodiments, such as Figure 18As shown, the mass block 50 has an isolation groove 30 in the middle, dividing the mass block 50 into two symmetrical parts, such as a first sub-mass block 51 and a second sub-mass block 52. The mass block 50 is physically divided into two sub-mass blocks by the isolation groove 30. At this time, the resonant frequency of the resonant unit 703 in the first acceleration detection component 71 is mainly affected by the axial displacement of the first sub-mass block 51 to which it is connected, and the resonant frequency of the resonant unit 703 in the second acceleration detection component 72 is mainly affected by the axial displacement of the second sub-mass block 52 to which it is connected. In this way, the mechanical coupling strength between the resonant units 703 in the two acceleration detection components 70 is weakened, which helps to narrow the self-locking acceleration range.

[0054] In other embodiments, such as Figure 19 As shown, an isolation groove 30 is provided in the middle of the anchoring platform 20, the mass block 50, and the anchoring part 21. The anchoring platform 20, the mass block 50, and the anchoring part 21 are divided into a symmetrical first part and a second part by the isolation groove 30. For example, the mass block 50 is divided into a first sub-mass block 51 and a second sub-mass block 52; the anchoring platform 20 is divided into a first anchoring sub-platform 22 and a second anchoring sub-platform 23; and the anchoring part 21 is divided into a first sub-anchoring part 211 and a second sub-anchoring part 212. The mass block 50, the anchoring platform 20, and the anchoring part 21 are all physically separated by the isolation groove 30, compared to... Figure 13 In the structure of the embodiment shown, the coupling strength between the resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72 is further weakened, and the self-locking range is further reduced.

[0055] In an optional example, in this resonant accelerometer with a double-ended fixed tuning fork structure, the anchoring platform 20, cantilever support assembly 40, mass block 50, force transmission assembly 60, and acceleration detection assembly 70 are all made of monocrystalline silicon (Si). Thus, this resonant accelerometer with a double-ended fixed tuning fork structure, through a geometrically symmetrical layout and stiffness gradient design (anchoring part 21 > support column 12 > resonant unit 703), combined with monocrystalline silicon integrated molding technology, allows the entire structure to expand freely, uniformly releasing thermal stress and reducing the zero-bias temperature coefficient to 0.5 ppm / ℃. The anchoring platform 20 is a rigid platform, effectively isolating 99% of external mechanical strain. This design overcomes the limitations of multi-anchor-point architectures and has significant application value in high-precision fields such as aerospace.

[0056] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A resonant accelerometer of a double-ended clamped-clamped tuning fork structure, characterized by, include: Substrate; An anchoring platform is disposed above the substrate, and the anchoring platform is connected to the substrate through an anchoring part; A mass block is connected to the anchoring platform via a cantilever support assembly, which suspends the mass block above the substrate. Acceleration detection components, including a resonant unit; A force transmission component connects the mass block and the resonant unit. The force transmission component transmits the X-axis displacement generated by the mass block under acceleration to the resonant unit, thereby changing the Y-axis vibration frequency of the resonant unit. The resonant unit includes a tuning fork-shaped resonant beam, which includes a first resonant beam and a second resonant beam arranged in parallel and spaced apart, and a coupling beam connecting the two ends of the first resonant beam and the second resonant beam. The tuning fork-shaped resonant beam is connected to the force transmission component and the anchoring platform through the coupling beams at both ends, respectively. The Y-axis vibration frequency of the resonant unit is used to determine the acceleration.

2. The resonant accelerometer with a double-ended fixed tuning fork structure according to claim 1, characterized in that, The acceleration detection assembly includes a first acceleration detection assembly and a second acceleration detection assembly symmetrically disposed on both sides of the anchoring portion; Each of the acceleration detection components further includes two electrode groups respectively disposed corresponding to the first resonant beam and the second resonant beam; each electrode group includes a driving electrode and a detection electrode, wherein the sum of the effective facing areas of the detection electrode and the corresponding resonant beam is greater than the sum of the effective facing areas of the driving electrode and the corresponding resonant beam.

3. The dual-ended clamped-beam tuning fork structure resonant accelerometer of claim 2, wherein, The first resonant beam and the second resonant beam are composite beams. The composite beam includes a main beam, two secondary beams located on both sides of the main beam and parallel to the main beam, and a central boss connecting the main beam and the secondary beams. The two ends of the main beams of the first resonant beam and the second resonant beam are respectively connected by coupling beams.

4. The resonant accelerometer with a double-ended fixed tuning fork structure according to claim 3, characterized in that, The resonant unit further includes a first comb tooth portion disposed on the sub-beam. The first comb tooth portion includes a plurality of first teeth extending outward from the sub-beam along the Y-axis direction and arranged at intervals along the length direction of the sub-beam. The electrode assembly includes a second comb tooth portion corresponding to the first comb tooth portion. The second comb tooth portion includes second teeth that are interleaved and spaced apart from the first teeth. The second comb tooth portion on the detection electrode corresponds to the first comb tooth portions at both ends of the corresponding sub-beam. The second comb tooth portion on the drive electrode corresponds to the first comb tooth portion in the middle of the corresponding sub-beam.

5. The dual-ended clamped-beam tuning fork structure resonant accelerometer of claim 2, wherein, The first resonant beam and the second resonant beam are single beams, and the resonant unit further includes a movable electrode disposed on the single beam; The driving electrode includes a positive driving electrode disposed between the two single beams and a negative driving electrode disposed on the outer side of the two single beams and corresponding to the position of the positive driving electrode; the detection electrode includes a positive detection electrode disposed between the two single beams and a negative detection electrode disposed on the outer side of the two single beams and corresponding to the position of the positive detection electrode.

6. The dual-ended clamped-beam tuning fork structure resonant accelerometer of claim 1, wherein, The mass block is arranged in a ring around the periphery of the anchoring platform; The cantilever support assembly comprises multiple components, symmetrically arranged on opposite sides of the anchoring platform.

7. The dual-ended clamped-beam tuning fork structure resonant accelerometer of claim 6, wherein, Each cantilever support assembly includes an anchor beam and a movable beam spaced apart from each other, a node beam connected to one end of the anchor beam and the movable beam, and an output beam extending outward from the end of the movable beam away from the node beam; The anchoring beam and the movable beam extend along the Y-axis, the end of the anchoring beam away from the node beam is connected to the anchoring platform, and the output beam is connected to the mass block.

8. The resonant accelerometer with a double-ended fixed tuning fork structure according to claim 2, characterized in that, The force transmission component includes a first force transmission component corresponding to the first acceleration detection component and a second force transmission component corresponding to the second acceleration detection component; Each of the force transmission components includes a resonant beam support and two levers connected to both ends of the resonant beam support. Each lever includes a lever arm, a lever input beam, a lever output beam, and a lever anchoring beam disposed on the lever arm. The lever anchoring beam connects the lever arm to the resonant beam support, the lever input beam connects the lever arm to the mass block, and the lever output beam connects the lever arm to the anchoring platform.

9. The resonant accelerometer with a double-ended fixed tuning fork structure according to any one of claims 1 to 8, characterized in that, The mass block has an isolation groove in its middle, dividing the mass block into two symmetrical parts; or, An isolation groove is provided in the middle of the anchoring platform, the mass block and the anchoring part, and the anchoring platform, the mass block and the anchoring part are divided into a symmetrical first part and a second part by the isolation groove.

10. The dual-ended clamped-beam tuning fork structure resonant accelerometer according to any one of claims 1 to 8, wherein, The aspect ratio of the first resonant beam and the second resonant beam is ≥80:1.

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