CN103234535B - A kind of quartz tuning-fork-type biaxial micro-gyroscope - Google Patents

Abstract

The invention relates to a MEMS angular velocity sensor, in particular to a quartz tuning fork type dual-axis micro gyroscope, which belongs to the technical field of inertial measurement devices. The biaxial micro-gyroscope of the present invention is processed by a z-cut quartz wafer with a certain thickness through a wet etching process. It specifically includes: four driving fingers, four sensitive fingers, a hexagonal frame, a left beam, a right beam, a central support structure, multiple driving electrodes, a y-axis sensitive electrode and a z-axis sensitive electrode. The angular velocity of the y-axis and the z-axis can be detected at the same time, and the separation of the driving finger and the sensitive finger reduces the cross-coupling between axes and ensures the measurement accuracy of the gyroscope. The y-axis sensitive electrodes and the z-axis sensitive electrodes are respectively arranged on different fingers, which reduces the difficulty of making the electrodes and ensures the feasibility of the process. The hexagonal frame reduces the error of the gyro. The central fixed support structure ensures the stability of the gyroscope.

Description

A Quartz Tuning Fork Dual-Axis Micro Gyroscope

technical field

The invention relates to a MEMS angular velocity sensor, in particular to a quartz tuning fork type dual-axis micro gyroscope, which belongs to the technical field of inertial measurement devices.

Background technique

Quartz micro gyroscope is a MEMS angular rate sensor, which is the core device of attitude control and inertial guidance. It has the advantages of small size, light weight and high reliability. With the development of microfabrication technology in recent years, the performance of quartz microgyroscope has been steadily improved, showing the characteristics of diversified structure, miniaturized volume, multi-axis measurement, and digital circuit.

The quartz micro-gyroscope manufactured by CST Corporation in the United States is the most mature. The typical structure of the gyroscope chip is an H-shaped structure, which is a y-axis sensitive gyroscope, as shown in Figure 1. The driving fingers and the sensitive fingers are respectively distributed above and below the central frame, and the coupling between the two fingers is small and the sensitivity is high. The quartz microgyroscope with this structure has been mass-produced and has the advantages of high precision, high stability and low noise. At the same time, the company also produces micro-gyroscopes for multi-axis measurement, which have low power consumption, low cost, good temperature characteristics and shock resistance characteristics, and are mainly used in military applications. However, the gyroscope is composed of multiple single-axis gyroscopes. The measurement unit packaged by the instrument combination does not use a single gyroscope chip for multi-axis measurement, which limits the further miniaturization of the device.

The multi-fingered single-axis quartz micro-gyroscope manufactured by EPSON Corporation of Japan has been used in the fields of automobile braking system, image stabilization and robot control. The typical structure of its products is double T-shaped, which is a z-axis sensitive single-axis gyroscope, as shown in Figure 2. The structure has four driving fingers and two sensitive fingers, the four driving fingers are distributed on both sides of the middle box, and the two sensitive fingers are respectively connected above and below the box. The advantage is that the difficulty of the manufacturing process is reduced, and the volume can be made very small. The packaged size is 5×3.2×1.3mm ³ , which expands the application field of the gyroscope. The multi-axis gyroscope produced by the company is also composed of multiple single-axis gyroscopes, and there is still the problem that it is not easy to further miniaturize.

In terms of electrode production, side block electrodes have been successfully produced in China. The Chinese patent "A Metallization Processing Method for Three-Dimensional Quartz Sensitive Structure" (Application Publication No.: CN102110771A) proposes a method that can process side electrodes with different polarities on the same side, which can be used in the mass production of quartz microdevices . This method provides a basis for the feasibility of single-chip quartz micro-gyroscope technology.

In short, the microfabrication technology related to the quartz micro-gyroscope is becoming more and more mature. At present, there are sufficient conditions to manufacture a multi-axis measurement quartz micro-gyroscope on a single chip, which further miniaturizes the device and expands its application range. Meet the needs of the market. However, the known single-chip quartz micro-gyroscope structure still has the following technical deficiencies: the electrode layout is relatively complicated, and the process is not easy to realize; there is a large cross-coupling between the two axes, which affects the measurement accuracy of the gyroscope.

Contents of the invention

The object of the present invention is to realize a single-chip dual-axis micro-gyroscope while reducing the difficulty of making the electrodes and reducing the cross-coupling between two axes, and proposes a quartz tuning fork type dual-axis micro-gyroscope. The gyroscope combines the characteristics of the American H-shaped tuning fork structure and the Japanese double-T-shaped tuning fork structure, and realizes the function of using a quartz chip to simultaneously detect two axial angular velocities.

The utility model relates to a quartz tuning fork type biaxial micro-gyroscope, which is processed by a Z-cut quartz wafer with a certain thickness through a wet etching process. It specifically includes: four driving fingers, four sensitive fingers, a hexagonal frame, a left beam, a right beam, a central support structure, multiple driving electrodes, a y-axis sensitive electrode and a z-axis sensitive electrode. The determination principle of the y-axis and the z-axis is as follows: the center of the hexagonal frame is used as the origin, the right beam is the positive direction of x, and the coordinate system established according to the right-hand principle is determined.

The central fixed support structure includes an upper connecting beam, a lower connecting beam and a fixing block. The fixed block is located in the center of the hexagonal frame, and the upper connecting beam and the lower connecting beam are drawn from the positive and negative directions of the y-axis of the fixed block respectively, and are connected to the midpoints of the upper and lower sides of the hexagonal frame parallel to the x-axis.

The two symmetrical vertices of the hexagonal frame are respectively distributed in the positive and negative directions of the x-axis, the left beam is connected to the vertices of the hexagonal frame along the negative direction of the x-axis; Connect with the vertices of the hexagonal frame.

The four driving fingers have the same structure and are respectively the first driving finger, the second driving finger, the third driving finger and the fourth driving finger. The first driving fork and the second driving fork are symmetrically located on both sides of the x-axis and perpendicular to the left beam; the third driving fork and the fourth driving fork are symmetrically located on both sides of the x-axis and perpendicular to the right beam. The first driving fork, the second driving fork, the third driving fork, and the fourth driving fork are symmetrical to the center of the hexagonal frame.

The four sensitive fingers have the same structure and are respectively the first sensitive finger, the second sensitive finger, the third sensitive finger and the fourth sensitive finger. The first sensitive fork, the second sensitive fork, the third sensitive fork and the fourth sensitive fork are respectively parallel to the y-axis, located at the first driving fork, the second driving fork, the third driving fork, the fourth Between the driving fork and the hexagonal frame; and the first sensitive fork, the second sensitive fork, the third sensitive fork, and the fourth sensitive fork are symmetrical to the center of the hexagonal frame.

The driving electrodes are divided into driving positive electrodes and driving negative electrodes. The driving positive electrodes are respectively arranged on the upper and lower surfaces of the first and second driving fingers and the left and right sides of the third and fourth driving fingers; the driving negative electrodes are respectively arranged on the left and right sides of the first and second driving fingers and the third and fourth driving fingers. 3. The fourth drives the upper and lower surfaces of the fork fingers. Wherein the upper surface electrode is connected with the lower surface electrode through the tip of the fingers, and the left side electrode is connected with the right side electrode through a lead wire.

The y-axis sensitive electrodes are divided into y-axis sensitive positive electrodes and y-axis sensitive negative electrodes. The y-axis sensitive positive electrode is arranged on the lower half of the left side of the third sensitive fork and the upper half of the right side and the upper half of the left side of the fourth sensitive fork and the lower half of the right side; y The axis-sensitive negative electrode is arranged on the upper half of the left side and the lower half of the right side of the third sensitive finger, and the lower half of the left side and the upper half of the right side of the fourth sensitive finger.

The z-axis sensitive electrodes are divided into z-axis sensitive positive electrodes and z-axis sensitive negative electrodes. The z-axis sensitive positive electrode is arranged on the upper and lower surfaces of the first sensitive fork finger and the second sensitive fork finger; the z-axis sensitive negative electrode is arranged on the left and right sides of the first sensitive fork finger and the second sensitive fork finger.

The lead wires of the above-mentioned multiple driving electrodes and sensitive electrodes are gathered in the fixed square of the central fixed support structure and lead out therefrom. The above-mentioned electrodes on the side cover the entire side; the electrodes on the upper and lower surfaces cover the entire length direction of the fingers, and leave a certain distance from the side electrodes in the width direction to prevent short circuit caused by contact with the side electrodes.

The working process of the quartz tuning fork type dual-axis micro-gyroscope of the present invention is as follows: when applying phase-opposite electrical signals to each positive and negative driving electrodes, the four driving fingers are made to perform simple harmonic vibration in the x-axis direction through the inverse piezoelectric effect ; When the y-axis has an angular velocity input, the four driving fingers generate a Coriolis force in the z direction, and the vibration is coupled to the four sensitive fingers through the left and right beams, so that the four sensitive fingers vibrate along the z-axis direction, through The charge collected by the y-axis sensitive electrode is amplified, filtered, and demodulated to measure the angular velocity in the y-axis; when the angular velocity is input in the z-axis, the four driving fork fingers generate a Coriolis force in the y-direction, which is transmitted by the left and right beams The vibration is coupled to the four sensitive fingers, so that the four sensitive fingers vibrate along the x-axis direction, and the angular velocity in the z-axis can be measured by amplifying, filtering, and demodulating the charges collected by the z-axis sensitive electrodes.

Beneficial effect

1. Using a quartz chip, it can detect the angular velocity of y-axis and z-axis at the same time.

2. The separation of the driving finger and the sensitive finger reduces the cross-coupling between axes and ensures the measurement accuracy of the gyroscope.

3. The y-axis sensitive electrode and the z-axis sensitive electrode are respectively arranged on different fingers, which reduces the difficulty of making the electrodes and ensures the feasibility of the process.

4. The hexagonal frame effectively suppresses the mechanical coupling between the driving finger and the sensitive finger, reducing the error of the gyroscope.

5. The central fixed support structure effectively isolates the influence of other vibration modes on the working mode, ensuring the stability of the gyroscope.

Description of drawings

Fig. 1 is the structure of H type quartz tuning fork in the background technology;

Fig. 2 is the structure of double T type quartz tuning fork in the background technology;

Fig. 3 is the arrangement of the structure of the quartz tuning fork and the driving electrodes and sensitive electrodes of the present invention; wherein (a) is the overall structure diagram of the quartz tuning fork, (b) is the structure diagram of the A-A section in the figure (a), and (c) is the diagram ( a) The structural diagram of the B-B section in (d) is the structural diagram of the C-C section in Figure (a);

Fig. 4 is the driving mode when the quartz tuning fork of the present invention works;

Fig. 5 is the y-axis sensitive mode when the quartz tuning fork of the present invention works;

Fig. 6 is the z-axis sensitive mode when the quartz tuning fork of the present invention works;

Fig. 7 is the electric field distribution of the fork fingers of the quartz tuning fork in different vibration directions in the specific embodiment; where (a) is the electric field distribution diagram when the fork fingers vibrate along the z direction, and (b) is the electric field when the fork fingers vibrate along the x direction Distribution;

Explanation of symbols: 110-first driving finger, 120-second driving finger, 130-third driving finger, 140-fourth driving finger, 201-left crossbeam, 202-right crossbeam, 310-first sensitive Fork, 320-second sensitive fork, 410-third sensitive fork, 420-fourth sensitive fork, 501-hexagonal frame, 502-upper connecting beam, 503-lower connecting beam, 504-fixed block , 111-the surface electrode of the first driving finger, 112-the left side electrode of the first driving finger, 113-the right side electrode of the first driving finger, 121-the surface electrode of the second driving finger, 122-the second driving Interdigital left side electrode, 123-second driving fork finger right side electrode, 131-third driving fork finger surface electrode, 132-third driving fork finger right side electrode, 133-third driving fork finger left side Surface electrode, 141-surface electrode of the fourth driving finger, 142-right side electrode of the fourth driving finger, 143-left side electrode of the fourth driving finger, 311-surface electrode of the first sensitive finger, 312-the first One sensitive fork finger right side electrode, 313-first sensitive fork finger left side electrode, 321-second sensitive fork finger surface electrode, 322-second sensitive fork finger left side electrode, 323-second sensitive fork finger electrode Right side electrode, 411-the third sensitive fork finger right upper half electrode, 412-the third sensitive fork finger left upper half electrode, 413-the third sensitive fork finger right lower half electrode, 414-the lower half electrode on the left side of the third sensitive fork finger, 421-the upper half electrode on the right side of the fourth sensitive fork finger, 422-the upper half electrode on the left side of the fourth sensitive fork finger, 423-the fourth sensitive fork finger Fork refers to the electrode on the lower half of the right side, 424-the fourth sensitive fork refers to the electrode on the lower half of the left side.

Detailed ways

In order to better illustrate the purpose and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

The tuning fork structure of the invention is processed by a z-cut quartz wafer with a certain thickness through a wet etching process. Fig. 3 is a specific structure of the present invention, including: four driving fingers, four sensitive fingers, two beams, a hexagonal frame and a central fixed support structure. The first driving finger 110, the second driving finger 120, the third driving finger 130, the fourth driving finger 140, and the four sensitive fingers 310, 320, 410, 420 are evenly distributed in the hexagonal frame 501. On both sides, the first sensitive fork 310 and the second sensitive fork 320 are sensitive fork for z-axis detection, the third sensitive fork 410 and fourth sensitive fork 420 are sensitive fork for y-axis detection Refer to; the left crossbeam 201 and the right crossbeam 202 are two crossbeams connecting the driving fork and the sensitive fork, and are connected to the left and right vertices of the hexagonal frame 501; the upper connecting beam 502, the lower connecting beam 503 and the fixed square 504 Form a central fixed support structure.

The distribution of each drive electrode of the present invention is shown in Figure 3(a): the surface electrode 111 of the first drive finger, the surface electrode 121 of the second drive finger, the right side electrode 132 of the third drive finger, the third drive finger The left side electrode 133, the fourth driving fork finger right side electrode 142 and the fourth driving fork finger left side electrode 143 are driving positive electrodes, the first driving fork finger left side electrode 112, the first driving fork finger right side The surface electrode 113, the second driving fork finger left side electrode 122, the second driving fork finger right side electrode 123, the third driving fork finger surface electrode 131 and the fourth driving fork finger surface electrode 141 are driving negative electrodes, wherein the first A driving fork finger surface electrode 111, a second driving fork finger surface electrode 121, a third driving fork finger surface electrode 131 and a fourth driving fork finger surface electrode 141 are arranged on the upper and lower surfaces of the fork finger, and the left side of the first driving fork finger Electrode 112, first driving finger right side electrode 113, second driving finger left side electrode 122, second driving finger right side electrode 123, third driving finger right side electrode 132, third driving finger The left side electrode 133 of the interdigital finger, the right side electrode 142 of the fourth driving fork finger and the left side electrode 143 of the fourth driving fork finger are arranged on the left and right sides of the fork finger, and the cross-sectional view in the yz plane is shown in Figure 3(b) As shown; the first sensitive fork finger surface electrode 311 and the second sensitive fork finger surface electrode 321 are z-axis sensitive positive electrodes, arranged on the upper and lower surfaces of the fork finger, the first sensitive fork finger right side electrode 312, the first sensitive fork finger The finger left side electrode 313, the second sensitive fork finger left side electrode 322 and the second sensitive fork finger right side electrode 323 are z-axis sensitive negative electrodes arranged on the left and right sides of the fork finger. The electrode arrangement is the same; the third sensitive fork refers to the upper half electrode 412 on the left side, the third sensitive fork refers to the lower half electrode 413 on the right side, the fourth sensitive fork refers to the upper half electrode 421 on the right side and the fourth sensitive fork The lower half electrode 424 on the left side of the finger is a y-axis sensitive positive electrode, the third sensitive fork refers to the upper half electrode 411 on the right side, the third sensitive fork refers to the lower half electrode 414 on the left side, and the fourth sensitive fork refers to the left side half electrode 414. The upper half electrode 422 on the side and the lower half electrode 423 on the right side of the fourth sensitive finger are y-axis sensitive negative electrodes, and the arrangement of the electrodes in the yz plane is shown in Fig. 3(c) and (d).

As shown in Figure 4, when applying periodic voltage signals with opposite phases to the driving positive electrode and the driving negative electrode respectively, the first driving finger 110, the second driving finger 120, the third The driving finger 130 and the fourth driving finger 140 generate periodic bending vibrations in the x direction. When the frequency of the input periodic voltage signal is the same as the eigenfrequency of the driving finger, the driving finger generates a reference vibration in the x direction.

As shown in Figure 5, when the first driving fork 110, the second driving fork 120, the third driving fork 130 and the fourth driving fork 140 generate reference vibration in the x direction, if there is an angular velocity input on the y-axis, then Drive the fork to generate the Coriolis force in the z direction, and generate simple harmonic vibration along the z direction, while the left beam 201 and the right beam 202 make simple harmonic vibration in the opposite direction along the z axis, and the vibration is coupled to the first sensitive fork 310 , the second sensitive finger 320 , the third sensitive finger 410 and the fourth sensitive finger 420 , and generate simple harmonic vibration along the z direction. Due to the piezoelectric effect of the quartz crystal, an electric field as shown in FIG. The positive and negative charges collected by the axis-sensitive positive electrode and the z-axis sensitive negative electrode neutralize each other, and the output is zero; at the same time, the y-axis sensitive positive electrode and the y-axis sensitive negative electrode form a differential charge, which can be obtained after amplification, filtering and demodulation. The angular velocity of the axis input.

As shown in Figure 6, when the first driving fork 110, the second driving fork 120, the third driving fork 130 and the fourth driving fork 140 generate reference vibration in the x direction, if there is an angular velocity input on the z axis, then Drive the fork to generate the Coriolis force in the y direction, and generate simple harmonic vibration along the y direction. At the same time, the left beam 201 and the right beam 202 make simple harmonic vibration in the opposite direction along the y axis, and the vibration is coupled to the first sensitive finger 310 , the second sensitive finger 320 , the third sensitive finger 410 and the fourth sensitive finger 420 , and generate vibration along the x direction. Due to the piezoelectric effect of the quartz crystal, an electric field as shown in FIG. The positive and negative charges collected by the axis-sensitive positive electrode and the y-axis sensitive negative electrode neutralize each other, and the output is zero; at the same time, the z-axis sensitive positive electrode and the z-axis sensitive negative electrode form a differential charge, which can be obtained after amplification, filtering and demodulation. The angular velocity of the axis input.

Above, an example of the present invention has been described in detail. In addition, the present invention has the following advantages: the separation of the driving fork and the sensitive fork reduces the cross-coupling between the two axes and ensures the measurement accuracy of the gyroscope; the left crossbeam 201 and the right crossbeam 202 connected to the two vertices of the hexagonal frame 501 can effectively suppress the mechanical coupling of the driving fork to the sensitive fork and reduce the error of the gyroscope; the central fixed support structure can effectively isolate the influence of other vibration modes and ensure the work of the gyroscope Stability; the y-axis sensitive electrode and the z-axis sensitive electrode are respectively arranged on different fingers, which reduces the difficulty of the process and ensures the feasibility of the structure in the process. However, the present invention still has shortcomings. Due to the anisotropy of the quartz crystal, after the wet etching process, there will still be a certain degree of coupling error between the y-axis sensitive mode and the z-axis sensitive mode, which can be optimized by optimizing the electrode layout. Or increase the difference between the two modal frequencies to reduce the influence of the coupling error and further improve the measurement accuracy of the gyroscope.

The above description is a preferred example of the present invention, and the protection scope of the present invention is not limited to this example. The basic idea of the present invention is to combine the working modes of the H-type tuning fork and the double-T-type tuning fork by using the multi-finger structure, separate the driving fork from the sensitive fork, and realize the dual-axis angular velocity detection on a single chip. The technical solutions under the idea of the present invention all belong to the category of the present invention.

Claims (5)

1. a quartz tuning-fork-type biaxial micro-gyroscope, is characterized in that: specifically comprise that four drivings are interdigital, four sensitivities are interdigital, hexagonal-shaped frame, left crossbeam, right crossbeam, center fixed support structure, multiple drive electrode, y-axis sensitive electrode and z-axis sensitive electrode;

Described center fixed support structure comprises tie-beam, lower tie-beam and fixed blocks; Fixed blocks is positioned at hexagonal-shaped frame center, and upper tie-beam, lower tie-beam are drawn from the y-axis positive dirction of fixed blocks, negative direction respectively, are connected to the mid point on the hexagonal-shaped frame up and down both sides parallel with x-axis;

In the positive dirction that two symmetrical summits of described hexagonal-shaped frame are distributed in x-axis respectively and negative direction, left crossbeam is along x-axis negative direction, be connected with the summit of hexagonal-shaped frame; Right crossbeam is along x-axis positive dirction, be connected with the summit of hexagonal-shaped frame;

Described four drive interdigital structures identical, be respectively the first driving interdigital, second drive interdigital, the 3rd drive interdigital and four-wheel drive is interdigital; First drives interdigital, that the interdigital symmetry of the second driving is positioned at x-axis both sides, perpendicular to left crossbeam; 3rd drives the both sides interdigital, the interdigital symmetry of four-wheel drive is positioned at x-axis, perpendicular to right crossbeam; First driving is interdigital, the second driving is interdigital drives interdigital, the interdigital relative hexagonal-shaped frame Central Symmetry of four-wheel drive with the 3rd;

Four described responsive interdigital structures are identical, are respectively first responsive interdigital, second responsive interdigital, the 3rd responsive interdigital and the 4th responsive interdigital; First is responsive interdigital, second responsive interdigital, the 3rd responsive interdigital responsive interdigital parallel with y-axis respectively with the 4th, first drive interdigital, second drive interdigital, the 3rd drive interdigital, four-wheel drive is interdigital and between hexagonal-shaped frame; And first responsive interdigital, the second responsive interdigital, four responsive interdigital relative hexagonal-shaped frame Central Symmetry responsive interdigital with the 3rd;

Described drive electrode is divided into driving positive electrode and drives negative electrode; Positive electrode is driven to be arranged in first, second left and right side driving interdigital upper and lower surface and the 3rd, four-wheel drive interdigital; The upper and lower surface driving negative electrode electrodes to be arranged in first, second to drive interdigital left and right side and the 3rd, four-wheel drive interdigital; Wherein upper surface electrode is connected by interdigital top with lower surface electrode, and left surface electrode is connected by lead-in wire with right flank electrode;

Described y-axis sensitive electrode is divided into the responsive positive electrode of y-axis and the responsive negative electrode of y-axis; The responsive positive electrode of y-axis is arranged in the 3rd responsive Lower Half of interdigital left surface and the first half of right flank and the 4th responsive first half of interdigital left surface and the Lower Half of right flank; The responsive negative electrode of y-axis is arranged in the 3rd responsive first half of interdigital left surface and the Lower Half of right flank and the 4th responsive Lower Half of interdigital left surface and the first half of right flank;

Described z-axis sensitive electrode is divided into the responsive positive electrode of z-axis and the responsive negative electrode of z-axis; The responsive positive electrode of z-axis is arranged in first responsive interdigital and the second responsive interdigital upper and lower surface; The responsive negative electrode of z-axis is arranged in first responsive interdigital and the second responsive interdigital left and right side.

2. a kind of quartz tuning-fork-type biaxial micro-gyroscope according to claim 1, is characterized in that: with the center of hexagonal-shaped frame for initial point, right crossbeam is x forward, and the coordinate system set up according to right hand principle determines y-axis and z-axis.

3. a kind of quartz tuning-fork-type biaxial micro-gyroscope according to claim 1, is characterized in that: the lead-in wire of multiple drive electrode and sensitive electrode comes together in the fixed blocks of center fixed support structure, and from then on draws.

4. a kind of quartz tuning-fork-type biaxial micro-gyroscope according to claim 1, is characterized in that: the electrode being positioned at side covers whole side; The electrode being positioned at upper and lower surface, in the whole covering of interdigital length direction, leaves certain distance at Width and side electrode, and preventing contacts with side electrode causes short circuit.

5. a kind of quartz tuning-fork-type biaxial micro-gyroscope according to claim 1, is characterized in that: process through wet-etching technology to cutting quartz wafer by having certain thickness z.