A large-capacitance, high-Q MEMS ring gyroscope with an external electrode

Abstract

The application provides a high-Q value MEMS ring gyroscope structure with external electrodes, which comprises a ring, a mass block arranged outside the ring and connected through a circumferential decoupling beam, a comb electrode arranged inside the mass block and a flat plate electrode arranged inside the ring. The MEMS gyroscope is connected through a radial connecting beam and an anchor point at the outermost side, the main working mode is a displacement amplification mode in which the inner multi-ring and the outer mass move in phase, the degeneration of the working mode and the detection mode can be realized, and the principle of the Coriolis effect is met. In addition, the external electrode of the application is an innovative stiffness-mass decoupling design, which optimizes the mode distribution of the ring gyroscope and improves the driving / detection capacitance of the gyroscope, so that the gyroscope has good dynamic characteristics and higher mechanical-electrical interface sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of gyroscope technology, specifically a MEMS ring gyroscope with large capacitance and high Q value and external electrodes. Background Technology

[0002] A gyroscope is a sensor that measures the angle, angular velocity, and angular acceleration of an object's motion relative to inertial space, and it has wide applications in both military and civilian fields. Currently, laser gyroscopes, fiber optic gyroscopes, and hemispherical resonator gyroscopes dominate the high-precision market. Although they can meet tactical requirements, their large size, high power consumption, complex manufacturing processes, and high cost limit their application and development in other fields.

[0003] Micro-mechanical gyroscopes, or MEMS (Micro Electro Mechanical systems) gyroscopes, have advantages such as small size, low power consumption, light weight, and low cost, making them promising for applications in high-precision attitude control and short-term intelligent device navigation. Currently, high-precision MEMS gyroscopes are mainly divided into two categories: traditional lumped-mass gyroscopes, whose operating modes are divided into driving and sensing modes, with the sensing mode detecting displacement signals under external angular velocity input; and solid-state wave gyroscopes, whose working principle is based on the inertial effect of elastic waves in a rotating axisymmetric structure. Ring gyroscopes are a type of solid-state wave gyroscope, and currently, Coriolis force vibration gyroscopes, represented by ring topologies, are becoming one of the mainstream technologies in this field. Benefiting from their flat, compact axisymmetric structural design, their driving and sensing mode modes are degenerate, resulting in high sensitivity and a simple structure, gradually becoming a widely used high-performance gyroscope. However, ring gyroscopes are limited by their structural form and spatial layout, resulting in a low quality factor (Q value). The spatial interference mode distribution is close to the gyroscope's operating mode, and the internal capacitance is small; increasing the capacitance increases nonlinearity, thus limiting their applications. Therefore, it is necessary to provide a new MEMS gyroscope to solve these problems. Summary of the Invention

[0004] The purpose of this invention is to propose a novel MEMS ring gyroscope structure with external electrodes. While increasing the capacitance, the stiffness-mass decoupling design adjusts the gyroscope's operating modes from the previously complex high-order modes to the first and second order modes, optimizing the gyroscope's dynamic characteristics. The gyroscope can operate in a high vacuum environment below 10 Pa, achieving a high Q value.

[0005] The technical solution to achieve the purpose of this invention is as follows:

[0006] A high-capacitance, high-Q MEMS ring gyroscope with external electrodes includes a ring component and a planar electrode located inside the ring component. The planar electrode is used for frequency tuning and quadrature suppression of the MEMS gyroscope.

[0007] The outer side of the annular component is connected to multiple mass blocks by multiple circumferential decoupling beams, and the multiple mass blocks are arranged at equal intervals along the circumference of the annular component; the circumferential decoupling beams are used to prevent the circumferential movement of the mass blocks from coupling with the circumferential movement of the annular component, and the circumferential decoupling beams are used to transmit the radial force from the mass blocks to the annular component.

[0008] The mass block is equipped with comb-tooth electrodes to increase the capacitance for driving and detection, and to reduce electrostatic nonlinearity and capacitive nonlinearity.

[0009] The comb electrode includes a driving electrode for driving the MEMS gyroscope structure to vibrate along a first direction and a second direction that are perpendicular to each other in generalized space, and a detection electrode for detecting the displacement of the mass block of the structure along the first direction and the second direction.

[0010] When the driving electrode is working, it generates an electrostatic force on the mass block, and provides a radial driving force to the ring part through the circumferential decoupling beam, thereby realizing displacement amplification.

[0011] The mass block is connected to the outermost anchor point via a first connecting beam and a second connecting beam along the radial direction of the gyroscope. The first connecting beam and the second connecting beam are used to adjust the radial stiffness of the mass block. By adjusting the radial stiffness and equivalent mass of the mass block, the operating mode frequency of the gyroscope is changed, thereby adjusting the frequency difference between the operating mode and other modes and optimizing the mechanical sensitivity of the gyroscope.

[0012] The significant advantages of this invention compared to existing technologies are:

[0013] By using external electrodes, the stiffness-mass decoupling design of the MEMS ring gyroscope is realized, enabling the adjustment of the gyroscope's operating mode order. On the other hand, the capacitance of the gyroscope is increased, thereby improving the electromechanical sensitivity of the gyroscope and enhancing the driving and detection efficiency of the MEMS ring gyroscope. This is of great significance for improving the performance of MEMS gyroscope prototypes. Attached Figure Description

[0014] Figure 1 This is a front view schematic diagram of the MEMS gyroscope disclosed in an embodiment of the present invention;

[0015] Figure 2 This is a partial schematic diagram of the MEMS gyroscope disclosed in an embodiment of the present invention;

[0016] Figure 3This is a simulation diagram of the thermoelastic damping of the MEMS gyroscope disclosed in an embodiment of the present invention;

[0017] Figure 4 This is a schematic diagram of the working modes of the MEMS gyroscope disclosed in an embodiment of the present invention;

[0018] Figure 5 This is a simplified dynamic model of the MEMS gyroscope disclosed in an embodiment of the present invention;

[0019] Figure 6 The equivalent mechanical sensitivity S of the MEMS gyroscope disclosed in this embodiment of the invention. mech The variation pattern of the resonant frequency;

[0020] Figure 7 The equivalent mechanical sensitivity S of the gyroscope mech A schematic diagram showing the relationship between the mass and the equivalent mass of the mass block.

[0021] Figure 8 The equivalent mechanical sensitivity S of the gyroscope mech A schematic diagram showing the relationship between the mass block and its equivalent stiffness. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, an embodiment of the present invention discloses a MEMS ring gyroscope 100 with external electrodes, including a ring component 1, a mass block 7 disposed outside the ring component 1 and connected by a circumferential decoupling beam 3, a driving electrode for driving the MEMS gyroscope structure to vibrate along a first direction and a second direction that are perpendicular to each other in generalized space, a detection electrode 4 for detecting the radial displacement of the mass block 7 of the structure along the first direction and the second direction, and sixteen planar electrodes 9 located inside the ring component 1 for orthogonal output suppression and modal frequency tuning of the MEMS gyroscope 100. The MEMS gyroscope 100 is connected to the outermost anchor point 2 by a first radial connecting beam 5 and a second radial connecting beam 6, as a novel stiffness-mass decoupling design for MEMS ring gyroscope structures.

[0024] like Figure 2As shown, in the embodiment of the present invention, the eight mass blocks 7 of the MEMS gyroscope 100 each have large-area comb-tooth electrodes 4 inside, serving as driving and detection electrodes for the gyroscope. This increases the capacitance by an order of magnitude, and the principle of variable area capacitance also reduces the electrostatic nonlinearity and capacitive nonlinearity of the electrodes. The present invention includes several spoke-connected annular components 1. The outermost ring is connected by a circumferential decoupling beam 3, forming a rotationally symmetrical structure with eight mass blocks 7. The centerline direction of the mass blocks 7 is consistent with the direction of the antinodes 2θ of the traditional annular structure. The angle formed between two adjacent mass blocks 7 and the center of the annular component 1 is 45° (45°×8=360°). The circumferential decoupling beam 3 is a flexible beam with high stiffness in the radial direction, providing electrostatic force from the driving electrodes to the annular component 1. It has low stiffness in the circumferential direction, enabling decoupling of the circumferential motion of the annular component 1 from the motion of the mass blocks 7.

[0025] In the embodiments of the present invention, the mass blocks of the MEMS gyroscope 100 are directly connected to the outermost triangular pyramidal anchor points via a first connecting beam located on the outer side and a second connecting beam located on the inner side. There is no coupling between any of the mass blocks, and the radial motion of the mass blocks is transmitted to the ring component only through the circumferential decoupling beam.

[0026] The MEMS gyroscope structure provided in the embodiments of the present invention generally operates under vacuum conditions (vacuum degree less than 10 Pa) to obtain a higher quality factor (Q value). Finite element simulation of a typical structure using finite element software yields a Q value of up to 700,000, as shown in the following figures. Figure 3 As shown, this structure, optimized for thermoelastic damping, achieves lower structural damping. The variable-area principle drive / detection comb provides the gyroscope structure with a smaller sliding film damping compared to the flat plate electrode pressure film damping.

[0027] When the MEMS gyroscope 100 is in use, in the absence of angular velocity in the inertial space, the mass block 7 is driven by the driving force F of the driving electrode 4. d Under the action of the first direction X (radial) and the second direction Y (radial), the ring part 1 with multiple spokes connected to form a 2θ vibration mode in this direction. Figure 4 Images A and B show the vibration modes of the MEMS gyroscope 100 in the X and Y directions, respectively. When an angular velocity exists in inertial space, according to the Coriolis principle, the angular velocity of the object's rotation will cause the ring component 1 to generate a Coriolis force in the orthogonal direction. Driven by the Coriolis force, the resonator vibrates along another mode-sensitive direction, forming a detection mode. The comb electrode 4 placed inside the mass block 7 can detect the radial displacement of the mass block 7, and after processing, the magnitude of the angular velocity in inertial space can be obtained.

[0028] The simplified model of the gyroscope 100 disclosed in this embodiment of the invention can be used Figure 5The multi-degree-of-freedom dynamic model is shown below. Figure 5 The figure shows a simplified dynamic model of the MEMS gyroscope 100 structure. Here, mass m1 represents the equivalent mass of the radially moving mass block 7 of the MEMS gyroscope 100, which is periodically distributed at 45°. Spring stiffness k1 represents the radial equivalent stiffness of beams 5 and 6 at the connection point between mass block 7 and the anchor point. c1 represents the damping coefficient of mass block 7. m2, k2, and c2 represent the equivalent mass, equivalent stiffness, and equivalent damping of the ring component 1, respectively. Since the mass blocks of the driving mode and the detection mode are not coupled, the working principle of this simplified model is as follows: through the driving force F... d This forces m1 to move in the driving direction (X direction), causing mass m2 to move as well. The in-phase motion mode of m1 and m2 is located in the first order of the multi-degree-of-freedom system, and the displacement of m2 can be amplified relative to the displacement of m1, with a displacement amplification factor of A. When the object rotates, m2 will generate a Coriolis force Fcor in the 90° direction perpendicular to the generalized space. The Coriolis force Fcor of m2 will become the driving force in another direction (Y direction) for m2 and m1, causing the structure to vibrate in the detection direction (Y direction). The simplified model's dynamic formula is:

[0029]

[0030]

[0031]

[0032]

[0033] Where x1 and x2 are the displacements of m1 and m2 along the driving direction (X direction), respectively; y1 and y2 are the displacements of mass blocks m1 and m2 along the detection direction (Y direction), respectively; Ω represents the magnitude of the angular velocity in the inertial space; and Ag represents the Coriolis coupling coefficient of the ring component. Therefore, the simplified model of the MEMS gyroscope with external electrodes has four degrees of freedom, while the traditional simplified model of a MEMS gyroscope has only two degrees of freedom. Based on the above formulas, the relationship between the displacement amplification factor A and the resonant frequency w of the MEMS resonator and various structural parameters can be derived:

[0034]

[0035]

[0036] The simplified model can be solved using the above formula, yielding two modes: a lower-order mode where m1 and m2 move in phase, representing displacement amplification, and a higher-order mode where m1 and m2 move out of phase. The in-phase mode amplifies the displacement of m2, which corresponds to the amplitude amplification of the ring component 1 relative to the mass block 7 in the actual model. Using the in-phase mode as the operating mode of the MEMS gyroscope 100, the mechanical sensitivity S of the gyroscope is... mech The distribution with resonant frequency can be as follows Figure 6 As shown, the in-phase mode is located in the first order of the multi-degree-of-freedom system, while the second and third orders are the natural frequency and out-of-phase motion mode of the ring component, respectively. The mechanical sensitivity of the in-phase mode is greater than that of other modes, and also greater than that of the traditional ring MEMS gyroscope dynamic model under the same structural parameters. The frequency difference between modes can also be adjusted by regulating the mass m1 and stiffness k1, thus optimizing the mode distribution. Therefore, the MEMS gyroscope 100 with external electrodes can serve as a solution for improving the dynamic characteristics of gyroscopes.

[0037] The MEMS gyroscope 100 disclosed in this invention embodiment can also be used as a stiffness-mass decoupled MEMS resonator model. While the ring width, spoke width, and number of rings in a traditional MEMS ring gyroscope can be considered structural parameters, the multi-ring structure, as a special form, cannot allow for separate adjustment of stiffness and mass. The MEMS gyroscope 100 disclosed in this invention embodiment can be adjusted... Figure 1 The stiffness k1 in the simplified dynamic model of the connecting beams 5 and 6 can be adjusted by modifying the layout area of ​​mass block 7, thereby achieving independent adjustment of the resonator's stiffness and mass. The mechanical sensitivity S of the equivalent dynamic model... mech The relationship between various structural parameters can be expressed as:

[0038]

[0039] Its variation law and its relationship with mass m1 and stiffness k1 can be referred to Figure 7 and Figure 8 As shown.

[0040] This invention innovatively uses the displacement amplification mode of the annular component and the mass block moving in phase as the driving and detection mode of the gyroscope. This mode is located in the first and second order of the gyroscope mode distribution. By adjusting the radial stiffness and equivalent mass of the mass block, the frequency of the gyroscope's working mode can be changed, thereby adjusting the frequency difference between the working mode and other modes and optimizing the mechanical sensitivity of the gyroscope.

Claims

1. A high-capacitance, high-Q MEMS ring gyroscope with external electrodes, comprising a ring component and a planar electrode located inside the ring component, wherein the planar electrode is used for frequency tuning and quadrature suppression of the MEMS gyroscope; characterized in that, The outer side of the annular component is connected to multiple mass blocks by multiple circumferential decoupling beams, and the multiple mass blocks are arranged at equal intervals along the circumference of the annular component; the circumferential decoupling beams are used to prevent the circumferential movement of the mass blocks from coupling with the circumferential movement of the annular component, and the circumferential decoupling beams are used to transmit the radial force from the mass blocks to the annular component. The mass block is equipped with comb-tooth electrodes to increase the capacitance for driving and detection, and to reduce electrostatic nonlinearity and capacitive nonlinearity. The comb electrode includes a driving electrode for driving the MEMS gyroscope structure to vibrate along a first direction and a second direction that are perpendicular to each other in generalized space, and a detection electrode for detecting the displacement of the mass block of the structure along the first direction and the second direction. When the driving electrode is working, it generates an electrostatic force on the mass block, and provides a radial driving force to the ring part through the circumferential decoupling beam, thereby realizing displacement amplification. The mass block is connected to the outermost anchor point via a first connecting beam and a second connecting beam along the radial direction of the gyroscope. The first connecting beam and the second connecting beam are used to adjust the radial stiffness of the mass block. By adjusting the radial stiffness and equivalent mass of the mass block, the operating mode frequency of the gyroscope is changed, thereby adjusting the frequency difference between the operating mode and other modes and optimizing the mechanical sensitivity of the gyroscope.

2. The MEMS ring gyroscope with large capacitance and high Q value of external electrodes according to claim 1, characterized in that, The mass blocks move only radially, and the direction of movement is consistent with the direction of the antinode of the 2θ mode vibration of the ring. No Coriolis force is transmitted between adjacent mass blocks.

3. The MEMS ring gyroscope with large capacitance and high Q value of external electrodes according to claim 1, characterized in that, The anchor point is in the shape of a triangular pyramid.

4. The MEMS ring gyroscope with large capacitance and high Q value of external electrodes according to claim 1, characterized in that, The circumferential decoupling beam uses a flexible beam to connect the radial motion of the mass block and the ring component. The radial stiffness is greater than the circumferential stiffness, which can achieve decoupling of the circumferential motion of the mass block and the ring component.

5. The MEMS ring gyroscope with large capacitance and high Q value of external electrodes according to claim 1, characterized in that, The angle between the line connecting the center of the adjacent mass block and the center of the ring component is 45 degrees.

6. The MEMS ring gyroscope with large capacitance and high Q value of external electrodes according to any one of claims 1-5, characterized in that, Its resonant frequency w and its structural parameters satisfy: Where m1 and k1 represent the equivalent mass and equivalent stiffness of the mass block along the driving / detection direction, and m2 and k2 represent the equivalent mass and equivalent stiffness of the ring component along the driving / detection direction.

7. The MEMS ring gyroscope with large capacitance and high Q value of external electrodes according to any one of claims 1-5, characterized in that, Its mechanical sensitivity S mech Its structural parameters satisfy: Where Ag represents the Coriolis coupling coefficient of the ring component, j is the complex unit, w is the resonant frequency, A is the displacement amplification factor, and m2, k2 and c2 represent the equivalent mass, equivalent stiffness and equivalent damping of the ring component, respectively.

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