Mass-stiffness decoupled ring-shaped MEMS resonator structure and trimming method

Abstract

This invention discloses a mass-stiffness decoupling ring-type MEMS resonator structure and its tuning method. The mass-stiffness decoupling ring-type MEMS resonator structure includes an anchor point, a resonant ring, and a support beam located between the anchor point and the resonant ring. The resonant ring has raised mass blocks evenly distributed circumferentially. This invention achieves mass-stiffness decoupling of the resonator by adding raised mass blocks to the resonant ring, thereby improving the equivalent vibrational mass of the system and reducing the system frequency. This enables rapid modal tuning of the resonator, ultimately improving the system's sensitivity, resolution, and signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, and more specifically, to a mass stiffness decoupling ring MEMS resonator structure and tuning method. Background Technology

[0002] Frequency splitting is a major obstacle in the development of high-performance gyroscopes, severely impacting their sensitivity, resolution, and signal-to-noise ratio. Tuning of ring gyroscopes has always been a significant research topic, with many institutions continuously exploring new structural designs and tuning methods to address modal mismatch issues caused by manufacturing errors. Chinese invention patent ZL201910811367.4 proposes removing a mass block at a corresponding position inside the resonant ring using laser tuning to correct the stiffness mismatch between the gyroscope's drive and detection axes. In traditional mechanical tuning, ring-type MEMS gyroscopes can only have mass removed or added to the ring, which simultaneously affects the mass and stiffness distribution of the gyroscope resonator, making the tuning process overly cumbersome and difficult. Therefore, it is necessary to design a mass-stiffness decoupled ring-type MEMS resonator structure and tuning method. Summary of the Invention

[0003] The purpose of this invention is to provide a mass stiffness decoupling ring MEMS resonator structure and tuning method to overcome the defects of the prior art.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A mass stiffness decoupling ring MEMS resonator structure includes an anchor point, a resonant ring, and a support beam located between the anchor point and the resonant ring. The resonant ring has protruding mass blocks evenly distributed in the circumferential direction.

[0006] Furthermore, the number of the mass blocks is a multiple of 8.

[0007] Furthermore, the mass block can be any structure with mass.

[0008] Furthermore, the mass blocks are uniformly distributed in the circumferential direction of the resonant ring, satisfying the rotational symmetry condition.

[0009] The present invention also provides a method for adjusting the above-mentioned mass stiffness decoupling ring MEMS resonator structure, comprising the following steps:

[0010] S1. Frequency sweep test to determine frequency splitting and identify the position of low-frequency rigid shaft;

[0011] S2. Select the mass block closest to the rigid axis to begin adjustment, and monitor the alignment of the rigid axis in real time.

[0012] S3. After the rigid shaft is aligned, simultaneously and equally adjust the two mass blocks aligned with the rigid shaft until the frequency difference reaches the set requirement.

[0013] Furthermore, step S1 is specifically implemented through the following method:

[0014] Connect the signal input / output terminals of the lock-in amplifier to the signal output / input terminals of the gyroscope. Excite the resonator with the power supply to measure the phase and amplitude of the signal at the gyroscope's drive shaft.

[0015] If there are two peaks in the amplitude signal, the rigid axis will have a certain deflection angle. The horizontal coordinate corresponding to the peak is the frequency value of the mode, and the difference between the two horizontal coordinates is the frequency split value.

[0016] If the amplitude signal has only one peak, the rigid axis is already aligned. Continue frequency sweeping by replacing the rigid axis with another one. The frequency difference between the two frequency sweeps is the frequency splitting value.

[0017] Furthermore, the adjustment method in step S2 includes dot-type addition of conductive adhesive, femtosecond laser removal of mass blocks, or addition of mass blocks; if dot-type addition of conductive adhesive is used, the mass block closest to the high-frequency rigid axis is determined by the position of the high-frequency rigid axis determined in step S1 and then dotted with adhesive; if femtosecond laser removal of mass is used, the mass block closest to the high-frequency rigid axis is determined by the position of the low-frequency rigid axis determined in step S1 and then drilled.

[0018] Furthermore, in step S3, the two mass blocks aligned with the rigid shaft are simultaneously and equally adjusted, including adding conductive adhesive to increase the mass blocks or removing the mass blocks with a femtosecond laser; if a femtosecond laser is used for frequency modulation, the two mass blocks corresponding to the low-frequency rigid shaft are simultaneously drilled.

[0019] Furthermore, the adjustment also includes combinations of removing and adding mass, and combinations of mass blocks.

[0020] Furthermore, the adjustment also includes a balance adjustment, which involves removing or adding the same mass simultaneously at four equivalent symmetrical positions.

[0021] Compared with the prior art, the advantages of the present invention are as follows: The present invention provides a mass stiffness decoupling ring MEMS resonator structure and tuning method, which adopts the method of adding a raised mass block on the resonant ring to achieve mass stiffness decoupling of the resonator, improve the equivalent vibration mass of the system, and reduce the frequency of the system. It can quickly achieve mode tuning of the resonator, and ultimately achieve the goals of improving system sensitivity, resolution and signal-to-noise ratio. At the same time, the combined tuning is convenient and flexible, the tuning position is easy to determine and the balance tuning is utilized. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the mass stiffness decoupling ring MEMS resonator structure of the present invention;

[0024] Figure 2 This is a diagram of the topology of the harmonic oscillator with mass stiffness decoupling according to the present invention;

[0025] Figure 3 This is a schematic diagram of the first and second modes of the resonator with mass stiffness decoupling according to the present invention;

[0026] Figure 4 This is a schematic diagram of the harmonic oscillator assembly tuning for mass stiffness decoupling according to the present invention;

[0027] Figure 5 This is a schematic diagram of the adjustment method for the ring-type MEMS sensitive structure with mass stiffness decoupling according to the present invention.

[0028] Figure 6 This is a schematic diagram of the modal mismatch error based on orthogonal detection according to the present invention. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0030] See Figure 1 and Figure 2 As shown, this embodiment discloses a mass stiffness decoupling ring-type MEMS resonator structure. The overall frame is anchored on all four sides, including anchor points 100, a resonant ring 200, and a support beam 300 located between the anchor points 100 and the resonant ring 200. A typical implementation is as follows: Figure 1 As shown, the resonant ring has raised mass blocks 400 evenly distributed in the circumferential direction, which can achieve the decoupling effect of mass and stiffness. That is, by using femtosecond laser or other mechanical adjustment methods to change the mass on the raised mass blocks, only the mass distribution of the structure is affected, without affecting the stiffness of the structure.

[0031] In some embodiments, the beam width, thickness, and angle of the raised mass blocks of the gyroscope resonator can be designed according to the specific application environment requirements. Changing these parameters will affect the final performance of the gyroscope. In other embodiments, the number and shape of the raised mass blocks can be changed, and their topology is as follows: Figure 2 As shown.

[0032] In this embodiment, the number of mass blocks is a multiple of 8, such as 8 or 16.

[0033] In this embodiment, the mass block can be any structure with mass, and its shape is not limited.

[0034] In this embodiment, the mass blocks are uniformly distributed in the circumferential direction of the resonant ring, satisfying the rotational symmetry condition.

[0035] The ring-type MEMS gyroscope operates in n=2 modes, with the angle between the inherent rigid axes of the first and second modes being 45°. Figure 3 As shown.

[0036] like Figure 4 As shown, the raised mass blocks are numbered sequentially from 1 to 16. During the adjustment process, different combinations are selected according to actual needs. According to adjustment theory, adjustments on raised mass blocks 90° apart are equivalent. Without considering balance adjustment, when the high-frequency rigid shaft is directly opposite the center of raised mass block 1, shaft and frequency adjustment can be performed only on mass block 1. When the high-frequency rigid shaft deflection is small, such as between mass blocks 1 and 16, shaft alignment can be achieved by adjusting the mass block closest to the shaft, followed by simultaneous frequency adjustment on mass blocks 1 and 16 or mass blocks 2 and 3. When the high-frequency rigid shaft deflection angle is large, such as between mass blocks 1 and 2, shaft alignment can be performed simultaneously on both mass blocks, followed by simultaneous frequency adjustment on mass blocks 1 and 16 or mass blocks 2 and 3. Considering balance adjustment, changing the mass on a raised mass block requires simultaneously changing the same mass on mass blocks 90° or 180° apart. For example, based on the initial frequency split and the magnitude of the high-frequency rigid shaft deflection angle, adjustments can be made simultaneously on mass blocks 1 and 9, or on mass blocks 1, 5, 9, and 13. During shaft adjustment, a fixed combination of mass blocks is not always selected; the selected mass blocks can be changed as needed based on the deflection direction of the high-frequency rigid shaft, allowing for flexible and rapid shaft adjustment. For instance, when the high-frequency rigid shaft deflection angle is large, adjustments can be made on mass blocks 1 and 2. However, as the high-frequency rigid shaft gradually aligns and the deflection angle decreases, adjustments can then be made only on mass block 1 later. Combined continuous adjustments involve not only combinations of protruding mass blocks but also combinations of adjustment methods. For example, shaft adjustment might be performed by removing mass blocks on mass block 1, while frequency tuning might be performed by adding mass blocks on mass blocks 2 and 3.

[0037] This embodiment's tuning method utilizes femtosecond laser removal of mass to achieve frequency matching of the ring-shaped MEMS sensitive structure. Femtosecond laser mass removal tuning requires locating a low-frequency, high-frequency rigid axis to increase the frequency corresponding to that axis, thereby reducing the frequency difference. When removing mass from the protruding mass block using a femtosecond laser, it is crucial to ensure that the overall structure of the resonator is not excessively damaged; that is, the removed mass must be limited, generally based on 1 / 10 of the total mass of the protruding mass block designed in this embodiment. The location for mass removal can be the center of the protruding mass block or other locations; due to the decoupling of mass stiffness, this will not affect the distribution of structural stiffness. Based on the characteristics of femtosecond laser equipment, mass removal typically involves drilling holes in a cylindrical shape, extending outwards from the center of the protruding mass block. The amount of mass removed is determined by the deflection angle of the high-frequency rigid axis and the magnitude of frequency fragmentation, selecting the size of the femtosecond laser path and the drilling depth.

[0038] The overall approach of the adjustment method for the ring-shaped MEMS sensing structure in this invention is to adjust the axis first and then adjust the frequency. During the axis adjustment process, the key lies in accurately identifying the alignment problem of the rigid axis, such as... Figure 5 As shown, three position lines are used, with lines 17 and 18 spaced 45° apart, and line 19 being the angle bisector of the two. These lines primarily illustrate the position of the rigid axis during the adjustment process. The initial rigid axis deflection angle of the resonator ranges from 0 to 22.5° (assuming the rigid axis deflects to the right). The angle difference between the resonator's drive axis and detection axis is 45°, and the included angle between the centers of the two protruding mass blocks is 22.5°. This indicates that the rigid axis may deviate from the originally aligned two protruding mass blocks. To minimize the introduction of instability errors during gyroscope adjustment, the adjusted mass should be symmetrically distributed. The modal mismatch error identification in the adjustment method of this invention is mainly based on orthogonal detection, such as... Figure 6 As shown, due to the deflection of the rigid axis, the drive axis and the detection axis of the gyroscope resonator are simultaneously excited, generating orthogonal signals. The sinusoidal components in the orthogonal signals correspond one-to-one with the frequency difference introduced by the deflection of the rigid axis, which can be used to determine whether the rigid axis is aligned.

[0039] Taking a garland-type resonator as an example, the tuning method for the mass stiffness decoupling ring-type MEMS resonator structure in this embodiment includes the following steps:

[0040] Step S1: Use a frequency sweep test to determine the frequency split and identify the position of the low-frequency rigid shaft.

[0041] Specifically, the signal input and output terminals of a lock-in amplifier are connected to the signal output and input terminals of a gyroscope. By exciting the resonator with a power supply, the phase and amplitude of the signal can be measured at the gyroscope's driving (or detecting) axis. If there are two peaks in the amplitude signal, it indicates that the rigid axis has a certain deflection angle. The horizontal coordinate corresponding to the peak is the frequency value of that mode, and the difference between the two horizontal coordinates is the frequency split value. If the amplitude signal has only one peak, it indicates that the rigid axis is aligned. Then, the frequency sweep is continued by switching to another axis, and the frequency difference between the two sweeps is the frequency split value. Due to the symmetrical structure, such as Figure 5 As shown, black lines 17 and 18 represent the ideal positions of the drive axis and the detection axis, with an angle of 45°. Assuming the rigid axis deflects to the right, based on the position of the drive or detection electrode and the frequency of the sweep, the low-frequency rigid axis can be roughly determined to be between 17 and 19, or 18 and 19. Generally, the initial frequency of the resonator is fragmented to tens of hertz, and the angle between the rigid axis and the ideal position is within 11.25°.

[0042] Step S2: Select the mass block closest to the rigid axis to begin adjustment, and monitor the alignment of the rigid axis in real time.

[0043] Specifically, this step is mainly to adjust the rigid shaft to the ideal position. The adjustment methods can include: dot-applying conductive adhesive and femtosecond laser removal of mass. Dot-applying conductive adhesive is a method to increase mass. Based on the relationship between frequency and mass, the position of the high-frequency rigid shaft is determined in step S1, and the protruding mass block closest to the high-frequency rigid shaft is applied with adhesive. Femtosecond laser removal of mass is a method to remove mass. The position of the low-frequency rigid shaft is determined in step S1, and the protruding mass block closest to the high-frequency rigid shaft is drilled.

[0044] The simplified second-order dynamic equation of the ring MEMS gyroscope resonator is as follows:

[0045]

[0046]

[0047] Where m is the equivalent mass, c1 and c2 are the equivalent damping, and k1 and k2 are the equivalent stiffness; the x-direction represents the driving mode, and the y-direction represents the sensing mode. Ideally, the driving force f is directed towards the driving shaft, and the driving frequency is w. d An angular velocity in the z-direction is applied in the plane, A g This represents the angle gain.

[0048] like Figure 6 As shown, due to the deflection of the rigid axis, the driving axis and the detection axis of the gyroscope resonator are simultaneously excited, generating orthogonal signals. Based on the above formulas (1) and (2), the expression for the orthogonal signal can be derived as follows:

[0049]

[0050] Where K is a relevant coefficient of the control system, and in the expression for the modal displacement of the mass block detection, only the component in phase with the driving modal displacement contains the angular velocity Ω. z Information. As can be seen from Formula 3, when the sinusoidal component of the orthogonal error signal is zero, the stiffness axis deflection angle, i.e., θ... w It is zero.

[0051] During axis alignment, the gyroscope output signal can be connected to an oscilloscope to monitor in real time whether the sinusoidal component of the quadrature signal is zero, thus determining whether the axis is aligned. For better alignment results, adjustments should not be made only on one raised mass block, but rather on symmetrical positions with equal amounts of adjustment.

[0052] Step S3: After the rigid shaft is aligned, adjust the two mass blocks on the rigid shaft simultaneously and equally until the frequency difference reaches the set requirement.

[0053] Specifically, after rigid alignment, i.e., axis adjustment, the purpose of this step is to perform frequency modulation. The rigid axis corresponds to two raised mass blocks, consistent with the adjustment method used in step S2. For example, when using a femtosecond laser for frequency modulation, locate the two raised mass blocks corresponding to the low-frequency rigid axis and simultaneously drill holes in them. To determine when frequency modulation ends, real-time axis-swapping frequency observation must be performed using a lock-in amplifier. When the axis-swapping frequency reaches the specified requirements, frequency modulation is considered complete, and equal adjustments should be made at symmetrical positions.

[0054] Table 1 Typical parameters of a garland-type MEMS gyroscope resonator model.

[0055]

[0056]

[0057] Table 2. Effects of Adjustment Position and Shape on Protruding Mass Blocks (Consistent Mass)

[0058]

[0059] This embodiment employs a method of adding a raised mass block to the resonant ring to achieve mass stiffness decoupling of the resonator, thereby improving the equivalent vibrating mass of the system and reducing the system frequency. This enables rapid modal tuning of the resonator, ultimately improving system sensitivity, resolution, and signal-to-noise ratio. Simulation results show that, under the model parameters listed in Table 1, the influence of the shape and position of the raised mass block on the tuning capability of the resonator is shown in Table 2. Removing the same mass from the raised mass block and changing its position or shape have no effect on the tuning effect of the resonator; the frequency difference remains consistent.

[0060] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, the patent owner may make various modifications or alterations within the scope of the appended claims, as long as they do not exceed the protection scope described in the claims of the present invention, they shall be within the protection scope of the present invention.

Claims

1. A mass stiffness decoupling ring-type MEMS resonator structure, characterized in that, It includes an anchor point, a resonant ring, and a support beam located between the anchor point and the resonant ring, wherein the resonant ring has protruding mass blocks evenly distributed in the circumferential direction; The number of the mass blocks is a multiple of 8; The mass block can be any structure with mass; The mass blocks are uniformly distributed in the circumferential direction of the resonant ring, satisfying the rotational symmetry condition.

2. The method for adjusting the mass stiffness decoupling ring-type MEMS resonator structure according to claim 1, characterized in that, Includes the following steps: S1. Frequency sweep test to determine frequency splitting and identify the position of low-frequency rigid shaft; S2. Select the mass block closest to the rigid axis to begin adjustment, and monitor the alignment of the rigid axis in real time. S3. After the rigid shaft is aligned, simultaneously and equally adjust the two mass blocks aligned with the rigid shaft until the frequency difference reaches the set requirement.

3. The adjustment method according to claim 2, characterized in that, Step S1 is specifically implemented through the following method: The signal input and output terminals of the lock-in amplifier are connected to the signal output and input terminals of the gyroscope. The phase and amplitude of the signal are measured at the gyroscope drive terminals by exciting the resonator with the power supply. If there are two peaks in the amplitude signal, the rigid axis will have a certain deflection angle. The horizontal coordinate corresponding to the peak is the frequency value of the mode, and the difference between the two horizontal coordinates is the frequency split value. If the amplitude signal has only one peak, the rigid shaft is already aligned. Continue frequency sweeping by replacing the rigid shaft with a different detection electrode. The frequency difference between the two sweeps is the frequency splitting value.

4. The adjustment method according to claim 2, characterized in that, The adjustment method in step S2 includes removing mass using femtosecond laser or adding conductive adhesive in a dotted manner to increase mass. If conductive adhesive is added in a dotted manner, the mass block closest to the high-frequency rigid axis is determined by the position of the high-frequency rigid axis in step S1 and the adhesive is applied. If femtosecond laser is used to remove mass, the mass block closest to the low-frequency rigid axis is determined by the position of the low-frequency rigid axis in step S1 and a hole is drilled.

5. The adjustment method according to claim 2, characterized in that, In step S3, the two mass blocks aligned with the rigid shaft are simultaneously and equally adjusted, including adding conductive adhesive in a spot manner, removing the mass block with a femtosecond laser, or adding a mass block; if a femtosecond laser is used for frequency modulation, the two mass blocks corresponding to the low-frequency rigid shaft are drilled simultaneously.

6. The adjustment method according to claim 2, characterized in that, The adjustment also includes combinations of removing and adding mass, and combinations of mass blocks.

7. The adjustment method according to claim 2, characterized in that, The adjustment also includes a balancing adjustment, which involves removing or adding the same mass simultaneously at four equivalent symmetrical positions.

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