KR100231715B1 - Planer vibratory microgyroscope - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration type micro gyroscope, and a conventional rotary gyroscope has many disadvantages such as being bulky and expensive to maintain high precision, and being easily damaged by shock and vibration. Accordingly, the present invention resonates the structure by using electrostatic force, and in this case, the springs supporting the resonant structure are arranged in a vertically and horizontally symmetrical manner so that resonance can always occur even in a detection direction perpendicular to the driving direction. Compared to the vibratory gyroscope, it is characterized by excellent sensitivity without the need for tuning the resonance mode frequency.

Description

Planer vibratory micorgyroscope

The present invention relates to silicon micro gyroscopes fabricated using micromachining techniques.

In general, gyroscopes are well known as angular velocity measuring devices used in navigational devices and inertial guidance devices such as aircraft, ships and automobiles. However, the conventional rotary gyroscope has a number of disadvantages such as being bulky and expensive to maintain high precision, and being easily damaged by shock and vibration. In addition, gyroscopes using fiber optics and lasers have excellent sensitivity, but have not overcome the disadvantages of being expensive, difficult to manufacture and bulky.

Therefore, a gyroscope is required to have high sensitivity, low cost, and miniaturization, and a sensor having a new driving principle has been developed due to the demand of an angular velocity measuring device capable of solving this problem. Systron of the United States manufactures a vibratory gyroscope that processes quartz with piezoelectric properties in the form of a tuning fork and detects strain due to Coriolis forces. In addition, US Patent 4,655,081 (4/1987 J.S.Burdess et al.) Introduced an angular velocity meter that measures the amount of resonance mode change in proportion to the rotational angular velocity while resonating the cylindrical structure with a piezoelectric element.

In order to realize a more miniaturized sensor, a study on a vibratory angular velocity device using silicon micromachining has been carried out, and various forms of design and invention have been made. Among them, US Patents 5,349,855 (9/1994 J. Bernstein et al.), 5,488,863 (2/1996 Y. Mochida et al.), 5,496,436 (3/1996 J.Bernstein et al.), 5,505,084 (4/1996 P.Greiff et al.) and the like are inventions related to micro gyroscopes that apply the vibration principle of the tuning fork, and US Pat. No. 5,535,902 (7/1996 P. Greiff et al.) applies rotational vibration to gimbals discs to The invention relates to a gyroscope for measuring the rotational speed. In addition, US Patent 5,450,751 (9/1995 M. Putty et al.) Is an invention that implements the US Patent 4,655,081 by a fine processing technology.

The above-mentioned inventions are gyroscopes that can be manufactured by a microfabrication technique, and most of them have a principle of vibrating the structure by generating a Coriolis force in a direction perpendicular to the plane in which the structure is placed and vibrating. It is the mainstream of silicon vibrating micro gyroscopes.

The conventional micro gyroscopes described above satisfy the requirements of low cost and miniaturization, but there are some problems to be solved for high sensitivity. First, a vacuum packaging process is required to reduce the air attenuation effect, and second, an operation of tuning the resonance mode frequencies of the driving and the detection which are located perpendicular to each other in order to increase the detection signal is required as accurately as possible.

Accordingly, the present invention has been made to solve the above problems, and has a structure of a sensor in which a detection mode is formed in a direction parallel to the substrate, compared to a gyroscope having a detection mode in a direction perpendicular to a conventional substrate. Since the lower detection electrode is not required, the process is simplified and the structure designed to have the same resonance mode frequency of driving and detection provides a low-cost, high-sensitivity micro gyroscope that does not require the frequency tuning required by the conventional vibratory gyroscope. There is a purpose.

1 is a configuration diagram of an embodiment of a planar vibrating gyroscope according to the present invention, which can be fabricated using a silicon on insulator (SOI) wafer and has the same resonance mode frequency of driving and detection.

2 is a schematic diagram for explaining the principle of measuring a change in capacitance from a detection electrode.

3 is another embodiment configuration diagram of a planar vibrating gyroscope according to the present invention that can be fabricated using an SOI wafer and has the same resonance mode frequency of driving and detection.

Figure 4 is a cross-sectional view to help understand the three-dimensional structure and manufacturing process of the planar vibrating gyroscope according to the present invention.

* Description of the symbols for the main parts of the drawings *

1: Structure Anchor 2: Plane Vibration Structure

3: angled beam spring 4a, 4b: left and right comb drive electrodes

5a, 5b: left and right driving electrode anchors 6a, 6b: upper and lower detection electrode anchors

7a, 7b: Upper and lower detection electrodes 8: Fixed detection electrodes

9: moving detection electrode 10: narrow detection interval

11: wide detection interval 12: direction of driving vibration

13: direction of detection vibration 14: DC voltage

15a, 15b: left and right driving electrodes 16: oxide film

17: substrate

The planar vibrating micro gyroscope according to the present invention for achieving the above object is a structure anchor (1) formed in the center of the entire structure; A curved beam spring (3) provided on the outside of the structure anchor (1) and having a symmetrical shape with respect to two axes in the vertical and horizontal directions; A planar vibrating structure (2) connected to the structure anchor (1) by the bent spring (3) and floating from the substrate (17); The planar vibrating structure 2 is provided on both left and right sides of the planar vibrating structure 2 so that the planar vibrating structure 2 vibrates in the left and right direction with respect to the structure anchor 1 and vibrates in the vertical direction when a rotational angular velocity is applied. Comb drive electrodes 4a and 4b for providing directional electrostatic force; Drive electrode anchors (5a, 5b) provided with metal electrodes to generate vibrations by applying a drive signal to the comb drive electrodes (4a, 4b); Detection electrodes (7a, 7b) provided at the upper and lower ends of the planar vibration structure (2) so as to detect vibration generated when the planar vibration structure (2) receives the Coriolis force by the external angular velocity by the capacitance method; It is characterized in that it comprises a detection electrode anchor (6a, 6b) provided with a metal electrode in order to receive the capacitance change from the detection electrodes (7a, 7b) as a detection signal.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 is a configuration diagram of an oscillating gyroscope capable of fabricating using an SOI wafer and having the same resonant mode frequencies of driving and detection, and FIG. 2 is a schematic diagram illustrating a principle of measuring a change in capacitance from a detection electrode. 3 is another embodiment configuration diagram of a vibrating gyroscope capable of fabricating using an SOI wafer and having the same resonant mode frequencies of driving and detection, and FIG. 4 is a schematic diagram illustrating a three-dimensional structure and manufacturing process of a planar vibrating gyroscope. It is a cross section.

The planar vibration type micro gyroscope of the present invention proposes a structure of a sensor in which a detection mode is formed in a direction parallel to the substrate, and also includes a vertical resonant frequency in which the resonant frequencies of the two modes are designed so that the frequency tuning of the driving and detection modes is unnecessary. We propose the structure of symmetrical folded beam spring. First, the structure and principle of the micro gyroscope of the present invention, in which both the driving and the detection vibration occur in parallel to the plane in which the structure is placed and the two mode frequencies are the same, are as follows.

1 shows the overall shape of a planar vibrating gyroscope structure that can be fabricated using an SOI wafer.

A structural anchor 1 is formed in the center of the entire structure in the form of a circle, and a planar vibrating structure 2 having a circular hole is formed on the outside of the structural anchor 1. The structure anchor 1 and the planar vibrating structure 2 are connected by a bent beam spring 3 so that the planar vibrating structure 2 is supported from the substrate. Comb drive electrodes 4a and 4b formed on the left and right sides of the planar vibrating structure 2 receive the signal from the left and right drive electrode anchors 5a and 5b and have the planar vibrating structure 2 in the left and right directions of FIG. 1. . At this time, when an angular velocity having a rotation axis perpendicular to the plane on which the plane vibration structure 2 is placed is applied, Coriolis force is generated in the up and down direction of FIG. 1 to vibrate the plane vibration structure 2 in the up and down direction. Upper and lower detection electrodes 7a and 7b which exhibit a sensitive capacitance change when the planar vibration structure 2 vibrates up and down are provided at both upper and lower ends of the planar vibration structure 2 and the upper and lower detection electrode anchors 6a. , 6b) receives a signal of capacitance change proportional to the external angular velocity from the upper and lower detection electrodes 7a and 7b.

The shape of the bent spring 3 is symmetrical about two axes of up, down, left and right from the center of the structure anchor 1 in the shape of a circle. Therefore, the spring constants in the vertical direction and the left and right directions are the same, which means that the mode frequencies in the vertical direction and the left and right directions are the same. Therefore, when the driving signal of the fundamental mode frequency is applied to the left and right comb drive electrodes 4a and 4b when there is a rotational angular velocity from the outside, the planar vibration structure 2 resonates in the left and right directions and at the same time up and down by Coriolis force. Resonance also occurs in the direction. Due to the bent spring 3, the mode frequency in the driving and detection directions can be automatically tuned to achieve high sensitivity of the sensor.

The structure of FIG. 1 forms a pattern by anisotropic etching of an SOI wafer and wet etches the oxide film 16 buried under single crystal silicon. In this case, all of the anchors 1, 5a, 5b, 6a, and 6b to be fixed to the substrate have a wider pattern so that the oxide layer 16 remains after the wet etching is finished, and the planar vibration to be floated from the substrate 17 The structure 2 is made of a lattice structure having many etching holes. Since the structure using the microfabrication of the SOI wafer is single crystal silicon, it has excellent mechanical and electrical properties, and has a high cross-sectional ratio, but it is impossible to form a lower electrode. Therefore, the shape of the detection electrode must be carefully considered.

2 simplifies and shows a part of the upper detection electrode 7a.

The fixed detection electrode 8, which is connected to the upper detection electrode anchor 6a as part of the upper detection electrode 7a, is fixed, and the upper planar vibrating structure as part of the upper detection electrode 7a. The movement detection electrode 9 connected to (2) moves in the direction 12 of the drive vibration and the direction 13 of the detection vibration like the planar vibration structure 2. In the initial equilibrium position without vibration, the fixed detection electrode 8 and the movement detection electrode 9 are arranged to have a narrow detection interval 10 and a wide detection interval 11 with each other.

The fixed detection electrode 8 detects a change in capacitance generated when a DC voltage 14 is applied between the movement detection electrode 9 and the fixed detection electrode 8 to move the movement detection electrode 9. do. When the movement detection electrode 9 moves in the direction 12 of the driving vibration, the increase and decrease of the capacitance occur simultaneously on both sides of the fixed detection electrode 8, so they cancel each other and the amount of change is very small. Even when the movement detecting electrode 9 moves in the direction 13 of the detection vibration, a change in capacitance that is opposite to each other occurs in the narrow detection interval 10 and the wide detection interval 11, but the wide detection Since the change in capacitance occurring in the interval 11 is very small compared to the change in capacitance occurring in the narrow detection interval 10, the change in the narrow detection interval 10 shows the change in the dominant capacitance. . Therefore, the upper and lower detection electrodes 7a and 7b change the capacitance insensitive to the driving vibration in the left and right directions, so that the amount thereof can be neglected, and the capacitance is sensitive to the vibration in the vertical direction to obtain a signal proportional to the vibration. Can be.

FIG. 3 shows another embodiment having left and right driving electrodes 15a and 15b in a form that prevents instability that may occur in the embodiment of FIG. 1.

In the embodiment of FIG. 1, the comb teeth driving electrodes 4a and 4b maintain the normal operation when the planar vibrating structure 2 vibrates only in the left and right directions, and have a factor of instability when vibrating in the upward direction. . In the embodiment of FIG. 3, the left and right driving electrodes 15a and 15b have a structure similar to that of the upper and lower detection electrodes 7a and 7b and have a long driving stroke. Therefore, even if the planar vibrating structure 2 vibrates in the up and down direction, the left and right driving electrodes 15a and 15b receive very small electrostatic force, thereby reducing the possibility of instability.

FIG. 4 shows a central section of the embodiment of FIG. 1 to aid in understanding the three-dimensional structure and manufacturing process of a planar vibrating microgyroscope.

1, 2 and 3 show an embodiment of the gyroscope fabrication using the microfabrication technology of the SOI wafer. However, the gyroscope of the present invention can produce the same structure even by using surface micromachining of polycrystalline silicon or plating of metal. In particular, in the case of manufacturing a gyroscope using the surface microfabrication of polycrystalline silicon, since the three-dimensional wiring can be performed under the structure using a multilayer structure, the shape of the detection electrode can be changed.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those who have

As described above, according to the present invention, the vibration of the gyroscope structure and the direction of detection lies on one plane, and the shape of the spring supporting the structure is symmetrically on the left and right and up and down axes so that the modes of vibration are the same. It provides the effect of achieving high sensitivity of the gyroscope without the need for frequency tuning.

Claims (5)

A structure anchor formed at the center of the entire structure; A curved beam spring provided outside the structure anchor and symmetrical with respect to two axes in the vertical direction and the left and right directions; A planar vibrating structure connected to the structure anchor with the bent beam springs floating from the substrate; Comb drive electrodes provided on both left and right sides of the planar vibrating structure to vibrate in the vertical direction when the planar vibrating structure vibrates in the left and right directions with respect to the structure anchor and to vibrate in the vertical direction when the rotational angular velocity is applied. and; A driving electrode anchor provided with a metal electrode to generate a vibration by applying a driving signal to the comb teeth driving electrode; Detection electrodes provided at upper and lower ends of the planar vibrating structure to detect vibration generated when the planar vibrating structure receives a Coriolis force due to an external angular velocity by an electrostatic capacitance method; And a detection electrode anchor provided with a metal electrode to receive a change in capacitance from the detection electrode as a detection signal. The method of claim 1, The bent spring spring, A flat vibration type micro gyroscope comprising the same vibration modes in the vertical and horizontal directions, and arranged symmetrically with respect to the upper, lower, left and right axes of the structure to sense the high sensitivity without the need for frequency tuning. The method of claim 1, The substrate, And a substrate vibrating microstructure of an SOI wafer so as not to form a thin film of an electrode or a wiring under the planar vibrating structure. The method according to any one of claims 1 to 3, The detection electrode, The detection electrode anchors are arranged in an arrangement of narrow detection intervals and wide detection intervals so that the upper and lower detection electrodes detect a change in capacitance which is insensitive to driving vibrations in the left and right directions and sensitive to the direction of the detection vibrations in the vertical direction. A flat vibration type micro gyroscope comprising: a fixed detection electrode attached thereto and a moving detection electrode attached to the planar vibrating structure. The method of claim 1, The drive electrode is similar in shape to the detection electrode in place of the comb drive electrode to prevent instability that may occur in the comb teeth driving electrode when the vibration in the detection direction is present, and further includes a driving electrode to increase the stroke of the vibration according to the driving signal. Planar vibration type micro gyroscope, characterized in that the configuration.

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