A micro-shell vibrating gyroscope resonant structure processing method and forming mold

Abstract

The present invention belongs to the field of micro-shell vibrating gyroscope resonant structure processing, and specifically relates to a micro-shell vibrating gyroscope resonant structure processing method, comprising the following steps: S1, placing a substrate on a molding cavity, and matching n matching holes arranged in a circular array on the substrate with n positioning pins arranged in an annular array on the molding cavity one by one, wherein n is equal to a multiple of 8; S2, heating the substrate for a set time, and simultaneously evacuating the molding cavity; S3, taking out the incompletely molded substrate, rotating the substrate 360 ​​degrees / n, and placing the substrate on the molding cavity again, and matching n matching holes with n positioning pins one by one; S4, repeating S2 and S3 for a total of n times to obtain a micro-shell curved surface structure. The micro-shell curved surface structure obtained by the method provided by the present invention is blown in steps to achieve frequency doubling conversion of low-order harmonic errors, and can convert the fourth harmonic error into a higher-order harmonic component with a smaller amplitude, thereby effectively reducing the frequency cracking of the gyroscope.

Description

Technical Field

[0001] The invention belongs to the field of micro-shell vibrating gyroscope resonant structure processing, and in particular relates to a micro-shell vibrating gyroscope resonant structure processing method and a forming die. Background Art

[0002] A gyroscope is a sensor that detects the angular velocity or angle of a platform's rotation relative to inertial space. It is a core component of inertial navigation and attitude measurement systems and has significant application value in unmanned platforms, robotics, industrial exploration, weaponry, and other fields. With the miniaturization of these application platforms, there is an urgent need for high-performance micro-electromechanical (MEM) gyroscopes with advantages such as small size, low power consumption, and low cost. Micro-shell vibrating gyroscopes are developed based on traditional large hemispherical gyroscopes. They are manufactured using a three-dimensional forming process and can be processed from high-quality fused quartz. As a result, micro-shell vibrating gyroscopes can achieve quality factors in the millions, making them an ideal solution for navigation-grade MEMS gyroscopes.

[0003] The micro-shell vibrating gyroscope is essentially a solid wave micro-mechanical vibrating gyroscope that detects angular velocity input based on the Coriolis effect. The micro-shell vibrating gyroscope operates in a mode matching state, and its driving mode (such as Figure 1 ) and detection modality (as shown in Figure 2 (as shown) are both n=2 "wine glass-shaped" modes, the two modes are identical and the vibration mode axes are orthogonal. When the gyroscope is working, a sinusoidal voltage of a fixed frequency is applied to the driving electrode to excite the resonant structure to work in the driving mode, which is the main mode; when there is an external angular velocity input, the detection mode will be excited in the direction 45° apart from the driving mode. The input angular velocity can be calculated by demodulating the amplitude of the detection mode. According to the basic theory of modal matching vibration gyroscope, the frequency decomposition of the micro-shell vibration gyroscope (that is, the frequency difference between the driving mode and the detection mode) will reduce the sensitivity of the gyroscope, thereby greatly restricting the improvement of the gyroscope performance. The sensitivity expression of the gyroscope in the closed-loop working mode is formula (1);

[0004] (1)

[0005] in, ω x 、 ω y denote the driving and detecting modal resonant frequencies, respectively. Q x 、 Q y Represent the driving and detection modal quality factors respectively, Ag is the angle gain, F x is the driving force of the gyroscope, M eff is the equivalent mass of the gyroscope.

[0006] This indicates that when the resonant frequencies of the driving and sensing modes perfectly match, the gyroscope achieves maximum mechanical sensitivity. However, when frequency splitting occurs, the gyroscope's sensitivity decreases significantly. Previous reports (such as those published in "Solid-State Wave Gyroscopes") indicate that the fourth harmonic error of the shell-vibrating gyroscope structure is the dominant factor causing frequency splitting in gyroscopes. Therefore, to reduce the gyroscope's initial frequency splitting, the key is to suppress the fourth harmonic error of the microshell's curved surface structure.

[0007] The fused silica micro-shell vibrating gyroscope can be formed by high temperature softening method (such as Figure 3 The manufacturing process (as shown) of fused silica micro-shell vibrating gyros features short processing time, high efficiency, and strong operability. A major challenge in manufacturing fused silica micro-shell vibrating gyros is the difficulty in machining the highly symmetrical micro-shell curved surface structure. The asymmetry of the curved surface structure will cause the gyro to experience frequency cracking. Traditional hemispherical resonant gyros, to suppress the frequency cracking of the hemispherical shell structure, primarily employ precision mechanical tuning methods after the micro-surface structure is machined, achieving modal matching through mass balancing. However, due to the significant reduction in the size of the micro-shell vibrating gyro structure, the frequency tuning method is relatively complex and inefficient.

[0008] The paper (Xiao D., Li W., Hou Z., et al. Fused Silica Micro Shell Resonator With T-Shape Masses for Gyroscopic Application [J]. IEEE Journal of Microelectromechanical Systems, 2018, 27(1):47-58.) proposed a rotary high-temperature softening process. This process improves the uniformity of the temperature field of the fused quartz plate by using a high-speed rotating platform, thereby improving the symmetry of the micro-shell gyroscope curved surface structure. However, the roundness error of the graphite mold will be directly reflected on the softened fused quartz glass surface, resulting in irreversible manufacturing errors in the curved shell structure. This roundness error is difficult to eliminate by high-speed rotation of the fused quartz plate and the graphite mold. It still requires precision mechanical adjustment after processing to suppress the fourth harmonic error. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for processing a micro-shell vibrating gyroscope resonance structure and a forming die capable of suppressing the fourth harmonic error.

[0010] The present invention provides a method for processing a micro-shell vibrating gyroscope resonant structure, comprising the following steps:

[0011] S1. Place the substrate on the molding cavity, and mate n matching holes arranged in a circular array on the substrate with n positioning pins arranged in a ring array on the molding cavity one by one, where n is a multiple of 8;

[0012] S2, heating the substrate for a set time, and simultaneously evacuating the molding cavity;

[0013] S3, take out the incompletely formed substrate, rotate the substrate 360° / n, and place the substrate on the forming cavity again, with the n matching holes and n positioning pins matching one by one;

[0014] S4. Repeat S2 and S3 for n times to obtain a microshell surface structure.

[0015] Furthermore, the matching hole and the positioning pin are clearance-matched.

[0016] Furthermore, the matching hole is a through hole.

[0017] Furthermore, the substrate is a fused quartz wafer.

[0018] Furthermore, n fitting holes are provided outside the base material.

[0019] Furthermore, the cross-sections of the matching hole and the positioning pin are circular.

[0020] Furthermore, in S2, the set time is t / n, where t is the total time for one-time molding of the substrate.

[0021] The method further includes, S5, cutting the portion with the matching hole on the outer side of the micro-shell vibration gyroscope resonance structure.

[0022] The present invention also provides a micro-shell vibrating gyroscope resonant structure forming mold, including a mold body, on which a forming cavity is provided. The mold body is located on a platform outside the forming cavity and is provided with n positioning pins in a circular array centered on the axis of the forming cavity, wherein n is equal to a multiple of 8, and also includes a negative pressure hole connected to the forming cavity.

[0023] Furthermore, a boss is provided at the center of the molding cavity.

[0024] The present invention has the beneficial effect of using the method provided herein to produce a micro-shell curved surface structure, using a step-by-step blow molding process, to achieve frequency multiplication conversion of low-order harmonic errors. Specifically, the present invention uses a rotation number that is a multiple of 8, which can convert the fourth harmonic error into a higher-order harmonic component with a smaller amplitude, effectively reducing the frequency splitting of the gyroscope. In other words, the method provided herein can directly form a micro-shell curved surface structure with a small initial frequency difference and low-order harmonic errors after processing, replacing the later work of suppressing low-order harmonic errors through complex vibration testing and adjustment methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the driving mode of the micro-shell vibration gyroscope.

[0026] Figure 2 Schematic diagram of the detection mode of the micro-shell vibration gyroscope.

[0027] Figure 3 This is a processing method for conventional micro-shell curved surface structures.

[0028] Figure 4 Schematic diagram of the structure of the substrate in the present invention.

[0029] Figure 5 It is a structural schematic diagram of the forming mold in the present invention.

[0030] Figure 6 It is a structural schematic diagram of the processing process of the present invention.

[0031] Figure 7 for Figure 6 Schematic diagram of the processing process after rotating the substrate 360° / n after processing.

[0032] Figure 8 This is a graph showing the relationship between the fourth harmonic and frequency decomposition.

[0033] Figure 9 Flowchart of the method of the present invention.

[0034] In the figure, 1-molding mold; 11, 111~118-locating pins; 12-molding cavity; 13-mold body; 14-boss; 2-base material; 21, 211~218-matching holes; 3-heating equipment. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0038] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; it can mean mechanical connection, electrical connection, physical connection, or wireless communication connection; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] As attached Figure 4-9 As shown, the present invention provides a method for processing a micro-shell vibrating gyroscope resonant structure, comprising the following steps:

[0041] S1. Place the substrate 2 on the molding cavity 12. The n matching holes 21 arranged in a circular array on the substrate 2 are matched one by one with the n positioning pins 11 arranged in a ring array on the molding cavity 12. Where n is a multiple of 8, i.e., n is 8, 16, 24, 32, 40, etc.;

[0042] S2, heating the substrate 2 for a set time, and simultaneously evacuating the molding cavity 12, that is, softening the substrate 2 by the flame generated by the heating device 3, and evacuating the molding cavity 12 to generate negative pressure to deform the substrate 2;

[0043] S3. After the set time has elapsed, the heating device 3 is removed or the heating device 3 stops heating, and the incompletely formed substrate 2 is removed by mechanical equipment. The substrate 2 is rotated 360° / n and placed on the forming cavity 12 again, with the n matching holes 21 and the n locating pins 11 matched one by one. At this time, the n matching holes 21 and the n locating pins 11 are matched with each other at a position offset from the previous processing.

[0044] S4. Repeat S2 and S3 for n times, so that each matching hole 21 matches with n positioning pins 11 in sequence. After heating and rotating n times, the micro-shell curved surface structure is obtained.

[0045] The micro-shell curved surface structure produced using the method provided by the present invention utilizes a step-by-step blow molding process to achieve frequency multiplication of low-order harmonic errors. Using multiples of 8 rotations, the present invention converts the 4th harmonic error into higher-order harmonic components (8th, 16th, 32nd, and so on) with smaller amplitudes, effectively reducing the frequency cracking of the gyroscope. Specifically, the method provided by the present invention directly produces a micro-shell curved surface structure with a low initial frequency difference and low-order harmonic errors in the gyroscope after processing, replacing the need for complex vibration testing and adjustment methods to suppress low-order harmonic errors later. Furthermore, the method provided by the present invention allows the substrate 2 to be formed using the method by simply adding locating pins to the existing forming mold. This significantly reduces the initial roundness requirements for the substrate 2 and the precision of the fit between the substrate 2 and the forming mold, simplifying the processing to a certain extent.

[0046] The structure of the matching hole 21 can be a blind hole or a through hole. The matching hole 21 is preferably a through hole, which is easier to process and can ensure the uniformity of the fit between the substrate 2 and the molding die 1.

[0047] The substrate 2 is a fused quartz wafer, and the fitting holes 21 are etched on the fused quartz wafer.

[0048] The basic requirement for the mating holes 21 is that n mating holes 21 are arranged in a circular array. When the initial structure of the substrate 2 is preferably disc-shaped, the centers of the n mating holes 21 are evenly distributed on a circumference concentric with the center of symmetry of the substrate 2. The n mating holes 21 are arranged on the outside of the substrate 2, and the inner portion between the n mating holes 21 of the substrate 2 serves as the molding area for the micro-shell curved surface structure. In other words, the arrangement of the mating holes 21 does not affect the molding area of ​​the micro-shell curved surface structure.

[0049] The cross-sections of the matching hole 21 and the positioning pin 11 can be regular polygons or circles, and circles are preferred to simplify the processing and facilitate matching.

[0050] In S2, the set time is t / n, where t is the total time for one-time molding of the substrate 2, that is, the molding is completed by rotating n times, which is obtained by dividing the time of one-time molding by an average.

[0051] The method provided by the present invention further includes:

[0052] S5. Cut the portion with the matching hole 21 on the outer side of the micro-shell vibrating gyroscope resonance structure to ensure that the end surface of the micro-shell curved surface structure is circular.

[0053] The present invention also provides a micro-shell vibration gyroscope resonant structure forming mold, including a mold body 13, on which a molding cavity 12 is provided. The mold body 13 is located on a platform outside the molding cavity 12 and is provided with n positioning pins 11 in a circular array with the axis of the molding cavity 12 as the center, wherein n is equal to a multiple of 8. The mold body 13 also includes a negative pressure hole connected to the molding cavity 12, and the negative pressure hole is used to vacuum the molding cavity 12. N positioning pins 11 are provided in a circular array with the axis of the molding cavity 12 as the center for cooperating with n corresponding matching holes 21 on the substrate 2.

[0054] A boss 14 is provided at the center of the molding cavity 12 for forming a matching boss of the micro-shell curved surface structure.

[0055] The principle of suppressing the fourth harmonic error of the curved surface structure by multi-step high-temperature softening forming proposed in this invention is as follows: the machining error of the conventional graphite mold forming cavity will be mapped to the surface of the micro-shell vibrating gyroscope curved surface structure. Through the harmonic decomposition method, its surface annular profile can be expressed as formula (2);

[0056] (2)

[0057] in, represents the amplitude of the annular profile of an ideally symmetrical micro-surface structure, and Respectively i The amplitude and phase of the harmonic components.

[0058] During the forming process of the curved shell structure of the present invention, the relative position of the fused quartz sheet and the graphite mold is controlled in steps to achieve the frequency doubling conversion of low-order harmonic errors. Assuming that the relative rotation angle between the fused quartz sheet and the graphite mold is ∆ θ , at this time the circumferential profile of the resonant structure surface can be expressed as formula (3);

[0059] (3)

[0060] Then By performing Fourier series expansion, we can obtain the surface structure i The order harmonic amplitude can be expressed as formula (4);

[0061] (4)

[0062] By changing It can realize the original i The first-order harmonics are converted into higher-order harmonics with smaller amplitudes. Taking n=8 as an example, when the number of the matching holes 21 is 8, the number of rotations is also 8. During the step-by-step high-temperature softening process, the relative rotation angle between the substrate 2 and the molding die 1 is 360° / 8, that is, , the 4th harmonic component is converted into the 8th harmonic. Figure 8 As shown in the figure, the 8th harmonic has no effect on frequency splitting, while the 4th harmonic is converted into the 8th, which effectively improves the sensitivity of the gyroscope and greatly enhances the performance of the gyroscope.

[0063] Preferably, the matching hole 21 and the positioning pin 11 are clearance-matched, which simplifies the difficulty of matching the substrate 2 and the forming mold 1 without affecting the processing effect. After the substrate 2 and the forming mold 1 are matched, the forming cavity 12 of the forming mold will be connected to the vacuum pump to generate an adsorption effect to adsorb the substrate 2. The substrate 2 will be automatically centered, and then the heating device 3 will heat the substrate 2, and the substrate 2 will be softened and formed in the forming cavity 12.

[0064] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A method for processing a micro-shell vibrating gyroscope resonant structure, characterized in that: The steps include: S1. Placing the substrate (2) on the molding cavity (12), wherein n matching holes (21) arranged in a circular array on the substrate (2) are matched one by one with n positioning pins (11) arranged in a ring array on the molding cavity (12), wherein n is a multiple of 8; S2, heating the substrate (2) for a set time, and simultaneously evacuating the molding cavity (12); S3, taking out the incompletely formed substrate (2), rotating the substrate (2) 360° / n, and placing the substrate (2) on the forming cavity (12) again, with the n matching holes (21) and the n positioning pins (11) matching one by one; S4, repeat S2 and S3 for n times to obtain a microshell surface structure; The blow molding process is carried out in steps, and the number of revolutions is multiples of 8, which converts the 4th harmonic error into a higher-order harmonic component with a smaller amplitude, effectively reducing the frequency cracking of the gyroscope; specifically, the first step of the micro-shell curved surface structure is blown in multiples of 8. i Harmonic amplitude for: is the surface annular profile of the microshell curved surface structure, expressed as: in, represents the amplitude of the annular profile of an ideally symmetrical micro-surface structure, and They are the first and second microshell surface structures when the blowing process is not divided into steps. i The amplitude and phase of the harmonic components of order, It is the relative rotation angle between the substrate and the molding cavity each time.

2. The micro-shell vibrating gyroscope resonant structure processing method according to claim 1, characterized in that: The matching hole (21) and the positioning pin (11) are clearance-matched.

3. The micro-shell vibrating gyroscope resonant structure processing method according to claim 1, wherein: The matching hole (21) is a through hole.

4. The micro-shell vibrating gyroscope resonant structure processing method according to claim 1, wherein: The substrate (2) is a fused quartz wafer.

5. The micro-shell vibrating gyroscope resonant structure processing method according to claim 4, characterized in that: N matching holes (21) are arranged outside the substrate (2).

6. The micro-shell vibrating gyroscope resonant structure processing method according to claim 1, characterized in that: The cross-sections of the matching hole (21) and the positioning pin (11) are circular.

7. The method for processing a micro-shell vibrating gyroscope resonant structure according to claim 1, wherein: In S2, the set time is t / n, where t is the total time for one-time molding of the substrate (2).

8. The method for processing a micro-shell vibrating gyroscope resonant structure according to any one of claims 1 to 7, wherein: Also includes, S5, cutting the portion with the matching hole (21) on the outer side of the micro-shell vibration gyroscope resonance structure.

9. A micro-shell vibrating gyroscope resonant structure forming mold, characterized in that: A micro-shell vibrating gyroscope resonant structure is processed by the method described in any one of claims 1 to 8, wherein the molding mold comprises a mold body (13), a molding cavity (12) is provided on the mold body (13), the mold body (13) is located on an outer platform of the molding cavity (12), and n positioning pins (11) are provided in a circular array with the axis of the molding cavity (12) as the center, wherein n is equal to a multiple of 8, and further comprises a negative pressure hole connected to the molding cavity (12).

10. The micro-shell vibrating gyroscope resonant structure forming mold according to claim 9, wherein: A boss (14) is provided at the center of the molding cavity (12).

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