KR19990073822A - Vibrating gyroscope - Google Patents

Abstract

The present invention relates to a vibration type gyroscope, and to provide a constant power driving and electromagnetic force detection type planar vibration gyroscope which is driven by constant power and has a structure of sensing angular velocity by voltage detected by electromagnetic force. The vibratory gyroscope includes: a constant power actuator vibrating in a horizontal direction by the constant power; Magnetic force detection unit is magnetically coupled to the electrostatic force actuator, and detects the amount of vertical movement of the actuator generated by the Coriolis force when the angular velocity is input by the magnetic induction voltage generated by the magnetic coupling It is configured to include.

Description

Vibrating gyroscope

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gyroscope, and more particularly, to a constant power drive and an electromagnetic force detection plane vibrating gyroscope having a structure that is driven by electrostatic force and senses angular velocity by voltage due to electromagnetic force detection. will be.

Conventional gyroscopes are designed to measure angular velocity by sensing a voltage proportional to the angular velocity driven by a constant power and constant power, or by sensing a voltage driven by an electromagnetic force and proportional to an angular velocity by an electromagnetic force. Such a gyroscope is a sensor for detecting an angular velocity and is used in a wide range of industrial fields. For example, it is applied to a wide range of industrial fields such as navigation systems, medical apparatuses, air-bags controllers for vehicles, and civil appliances.

A representative example of measuring the angular velocity by detecting a voltage corresponding to the vertical vibration of a vibrator driven by a constant power, driven horizontally by a constant power and driven by a Coriolis force, is described by "J. Bernstein et al. The paper may be "A Micromachined Comb-Drive Tuning Fork Rate Gyroscope", Proceeding of IEEE workshop on Microelectomechanical System, pp.143-148, 1993. In addition, it is anticipated that the sensor circuit must be integrated and manufactured in order to increase the sensitivity, which lowers the production yield, which in turn hinders the cost reduction, and is driven by the electromagnetic force and detects the voltage corresponding to the angular velocity by the electromagnetic force. The gyroscope has a large size of the driving coil and requires a lot of input power. It is difficult to apply to a very small product that becomes suitable.

Accordingly, an object of the present invention is to provide a vibrating gyroscope that is driven at a constant power and detects the angular velocity by detecting the vertical movement of the vibrator due to the Coriolis force by the electromagnetic force.

Another object of the present invention is to provide a vibrating gyroscope having an electrostatic drive actuator that can be easily implemented on a silicon wafer.

Another object of the present invention is to provide a vibrating gyroscope having a very high detection sensitivity of the angular velocity.

According to an aspect of the present invention, there is provided a vibration type gyroscope comprising: a constant power actuator vibrating from side to side by a constant voltage input; It is magnetically coupled to the electrostatic force actuator, and includes an electromagnetic force detection unit for detecting the amount of vertical movement of the actuator generated by the Coriolis force by the magnetic induction voltage generated by the magnetic coupling when the angular velocity input It is characterized by the configuration characterized by the configuration.

The electrostatic actuator according to the principles of the present invention, the oscillator formed with a predetermined size in the center of the bulk silicon substrate having a predetermined thickness, coupled between the vibrator and the ground electrode and the spring pad on the silicon substrate, respectively, First and second springs for supporting a vibrator on the substrate and the silicon substrate and spaced apart in the shape of the vibrator and the comb to horizontally drive the actuator by a driving voltage having a different phase. It is configured to include a drive electrode, characterized in that the bulk silicon substrate having a silicon crystal direction of "110" by the process of four masks and four etchings (etching).

In addition, the thicknesses of the first and second driving electrodes, the ground electrodes, and the spring pads of the electrostatic actuator according to the principles of the present invention are formed by the thickness of the bulk silicon substrate, and the thickness of the springs is relatively thin.

1 is an exploded perspective view for explaining a schematic configuration of a vibrating gyroscope according to an embodiment of the present invention.

FIG. 2 is a view illustrating in more detail the structure of the comb-driver actuator shown in FIG. 1 for explaining the design conditions of the polysilicon spring between the vibrator, the ground electrode, and the spring pad.

FIG. 3 illustrates a planar structure of a comb-driver actuator of a gyroscope according to an exemplary embodiment of the present invention, and is a view for explaining that electrostatic actuation is performed.

4 is a cross-sectional view of a portion shown for explaining the operation of the electromagnetic force generator of the gyroscope according to an embodiment of the present invention.

5A to 5H and 5I are views for explaining a manufacturing process of the polysilicon spring according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to obscure the subject matter of the present invention.

1 is an exploded perspective view for explaining a schematic configuration of a vibrating gyroscope according to an embodiment of the present invention. In Fig. 1, reference numeral 12 denotes a comb-driver actuator that is driven at an input of electrostatic and vibrates horizontally. A cylindrical sensing coil 28 is fixed on the upper and lower surfaces of the comb-drive actuator 12, and the sensing coil 28 is coupled to an electromagnetic force generator 34 including a permalloy core 32 having a feed coil 30 at the center thereof.

The comb-drive actuator 12 is a vibrator 14 formed in a predetermined size on a bulk silicon substrate, first and second drive electrodes 16 and 18 spaced apart in the form of a comb on both sides of the vibrator 14 and the vibrator A grounding electrode 20 and a spring pad 22 connected to another symmetrical part of 14, respectively. At this time, the both sides of the vibrator 14 and the ground electrode 20 and the spring pads 22 is fixedly coupled by an elastic body 24 having a relatively good conductivity, and the vibrator between both sides of the vibrator 14 and the first, second driving electrodes 20, 22 A plurality of comb-fingers extending from the 14 and the driving electrodes 20 and 22, respectively, are spaced apart to form a comb-form. In the above, the conductive material 24 having good conductivity may be a spring formed by etching poly-silicon or a metal formed by a micro plating method. In addition, each of the electrodes 16, 18, and 20 of the comb-drive actuator 12 and the spring pad 22 may be anodized by a glass support (not shown in FIG. 1) located below. Supported. The comb-drive actuator 12 as described above is formed through the use of four masks on a bulk silicon substrate having a crystalline form of silicon " 110 ", as described in the manufacturing process with reference to FIGS. 6A to 6H. Its contents will be clearly understood.

Although not shown in detail in FIG. 1, both ends of the coils forming the sensing coils 28 are separated and electrically connected to two polysilicon pads 24 electrically insulated from each other on the upper portion of the spring pad 22. As shown in FIG. 1, the two polysilicon springs 24 separated from the upper portion of the spring pad 22 serve as an electrode for outputting a voltage Vo derived from the sensing coil 28. In addition, the feed coil 30 located in the center of the permalloy core 32 of the electromagnetic force generator 34 of FIG. 1 generates magnetic flux in a circular air gap g by supplying a predetermined DC current I _d .

First, the operation of the vibration gyroscope according to the present invention will be described with reference to FIG. 1.

Now, when the first and second driving voltages V1 and V2 having different phases are supplied between the first driving electrode 16, the ground electrode 20, and the second driving electrode 18 and the ground electrode 20, as shown in Equation 1 below, the ground electrode 20 The vibrator 14 supported on the glass support 26 by a polysilicon spring 24 connected to the spring pad 22 is driven along the X-axis direction of FIG. 1. When the vibrator 14 vibrates in the X-axis direction as described above, the circular sensing coils 28 coupled to the vibrator 14 reciprocate on the vertical movement path of the conductor formed in the form of a hole in the electromagnetic force generator 34, that is, the air gap g.

In Equation 1, V _d and V _s are magnitudes of a DC voltage and an AC voltage supplied from the outside.

That is, when the first and second driving voltages as shown in Equation 1 are supplied to the first and second driving electrodes 16 and 18, two combs are formed on the first and second driving electrodes 16 and 18 and the vibrator 14, respectively. The vibrator 14 is push-pull driven in the X-axis direction by the electrostatic force generated between the fingers. At this time, when a predetermined DC current I _d is supplied to the feed coil 30 in the electromagnetic force generator 34, magnetic flux Φ is generated in the vertical movement path, that is, the air gap g of the electromagnetic force generator 34.

In this state, when the surface fixed in the Y direction perpendicular to the driving direction of the vibrator 14 rotates, the vibrator 14 moves in the vertical direction Z by the Coriolis force. The amount of vertical movement of the vibrator 14 is detected as the voltage Vo by the sensing coils 28 attached to the upper and lower surfaces of the vibrator 14 and the electromagnetic force generator 34 magnetically coupled thereto. The voltage Vo detected by the coils 28 corresponds to the angular velocity Ω. Such operation details will be more clearly understood by the following description.

FIG. 2 is an exploded perspective view of the comb-driver actuator shown in FIG. 1 to describe resonance conditions in relation to the coupling state of the vibrator and the ground electrode, the spring pad and the sensing coil, and the design conditions of the polysilicon spring. . 3 is a view illustrating a planar structure of a comb-driver actuator of a gyroscope according to an exemplary embodiment of the present invention, and is a diagram for describing actuation by electrostatic power.

2 and 3, the polysilicon springs 24 formed between the ground electrode 20 and the vibrator 14 shown in FIG. 1 are contact via hles (not shown) formed in the ground electrode 20 and the vibrator 14, respectively. This contact is conductively coupled through). In addition, the polysilicon spring 24 connected between the vibrator 14 and the spring pad 22 is used as an electrode pad for outputting the voltage Vo output from the sensing coil 28 located on the upper and lower surfaces of the vibrator 14. a second driving electrode 16, respectively, extending from 18 formed comb - is the height (thickness) h _e is (thick) high of the finger, and the polysilicon spring 24, the thickness (height) of t _k is very thin (low) is made The driving force by electrostatic power was made large. This is because the driving force of the vibrator 14 is proportional to the height (thickness) h _e of the comb-fingers as electrodes. In addition, since the elastic strength of the polysilicon springs 24 becomes smaller as the thickness (height) t _k of the spring 24 becomes smaller, the sensitivity is increased, so that the improvement of the electromagnetic force sensing performance can be described well. In the present invention, the height h _e of the comb-fingers is about 500 μm, and the separation distance between the comb-fingers of the vibrator 14 and the comb-fingers of the first or second driving electrodes 16 and 18 is about 5 μm. The width w _k and the thickness t _k of the silicon springs 24 are formed very thinly (about 5 μm) compared to the thickness (depth) h _e (h _e = 525 μm) of the silicon substrate. More specifically, the shape of the polysilicon springs 24 is square.

If the resonance frequency of the com-drive actuator 12 manufactured as shown in Figs. 2 and 3 is f, it is expressed by Equation 3 below.

Where M and m are the mass of the vibrator 14 and polysilicon spring 24 and N _k is the number of comb-fingers of the polysilicon spring 24. And l _k represents the length of the polysilicon springs 24. In accordance with the present invention, the comb-drive actuator 12 configured as shown in FIGS. 2 and 3 is designed such that the resonance frequency f can be about 200 Hz. In this case, since the polysilicon springs 24 have a fixed-fixed beam structure at both ends of the vibrator 14, the ground electrode 20, and the spring pads 22, the coefficient of the polysilicon springs 24 is K _sys . Becomes

E in Equation 4 is the Young's modulus of polysilicon springs 24, I = (1/12) w _k t _k ³ Is the moment of inertia of the polysilicon springs 24 and W _k , t _k , l _k are the width, thickness and length of the polysilicon springs 24.

The first and second driving voltages V1 and V2 of Equations 1 and 2 described above are supplied to the first and second driving electrodes 16 and 18 to the comb-drive actuator 12 of FIG. 2 designed to have the resonance frequency f as described above. Then, the vibrator 14 is driven and vibrated in the X-axis direction by the constant power F ^e _x as shown in Equation 5 below.

In Equation 5, ε ₀ is the dielectric constant of the silicon silicon substrate, h _e is the height of the comb-fingers of the first, second driving electrodes 16 and 18, g _e is the comb of the first, second driving electrodes 16 and 18 The gap of the fingers, N _e is the number of comb fingers, ω _d is the excitation frequency, V _d is the DC voltage supplied, V _s is the magnitude of the AC voltage supplied.

Therefore, when the first and second driving voltages V1 and V2 as shown in Equations 1 and 2 are supplied to the com-drive actuator 12 configured as shown in FIG. 2, the vibrator 14 is formed by the constant power F ^e _x as shown in Equation 5. It reciprocates in the horizontal direction, that is, in the X-axis direction. At this time, if the displacement function in the X-axis direction by the electrostatic force F ^e _x as described above is x (t), it is expressed by the following equation (6).

Where K _x is the stiffness of the polysilicon springs 24 upon vibration in the X axis and Q _x is the quality factor. In addition, it is assumed that the driving frequency of the vibrator 14 is equal to the resonance frequency f to obtain a high sensing ability.

In the state in which the vibrator 14 vibrates in the X-axis direction as shown in Equation 6, when the angular velocity Ω is applied to the Y-axis of FIG. 2, the vibrator 14 causes vibration in the vertical Z-axis by Coriolis force. That is, the Coriolis force F ^e _Z generated by the angular rate Ω of the Y axis attention causes the comb-drive actuator 12 to be driven in the Z-axis direction. The displacement Z (t) induced by the Z axis is represented by Equation 7 below.

In Equation 7, Ω is the angular velocity, K _z is the stiffness of the polysilicon springs 24 along the Z axis, Q _x and Q _z is the quality factor, K _x and K _z of the polysilicon springs 24 equal to the value of K In this case, the resonance frequencies along the X and Z axes are matched.

Therefore, the comb-drive actuator 12 of the present invention having the configuration as shown in FIG. 2 is horizontally vibrated by the electrostatic force as described above, and when the fixed surface of the vibrator 14 is vibrated rotates as shown in Equation 7 It moves in the vertical direction.

The vertical movement is detected as an electromagnetic force by the sensing coils 28 installed on the upper and lower surfaces of the vibrator 14 and the electromagnetic force generator 34 magnetically coupled to the sensing coils 28. As such, the operation of sensing the vertical movement amount of the vibrator 14 by the electromagnetic force will be described with reference to FIG. 4.

Figure 4 is a cross-sectional view of a portion shown for explaining the operation of the electromagnetic force generator of the gyroscope according to an embodiment of the present invention. Referring to FIG. 4, the magnetic coupling relationship of a sensing coil 28 fixedly connected to the vibrator 14 of the comb-drive actuator 12 and the electromagnetic force generator 34 positioned below the sensing coil 28 may be clearly understood. Lost

As described above, when the angular velocity? Is generated on the surface of the vibrator 14, the vibrator 14 is vibrated in the vertical Z axis by the equation (7). That is, the ratio of the angular velocity Ω causes the vibration of the comb-drive actuator 12 and the sense coil 28 along the Z axis. When the vibrator 14 vibrates along the Z axis, the cylindrical sense coil 28 is vertically moved along the air gap g _m of the electromagnetic force generator 34.

At this time, the magnetic flux Φ is generated from the feed coil 30 according to the current I _d flowing through the feed coil 30, and the magnetic flux Φ generated by the feed coil 30 is an air gap of the cylindrical sensing coil 28 located on the vibrator 14. g _m , that is, sinusoidally changes as it passes through the vertical path of motion of the conductor At this time, the magnetic flux density of the air gap g _m is generated by the feed coil 30 supplied with the DC voltage i _d , and when the conductor passes through the magnetic field of the air gap g, the induced voltage Vo as shown in Equation 8 is detected. Outputs at 28

In Equation 8, N _f is the number of turns of the feed coil 30, i _d is the applied current, g _m is the length of the air gap, N _s is the number of turns of the sensing coil 28, h _m is the thickness of the magnetic material, r _m Is the average radius of the air gap, h _m is the height of the sense coil 28, and V _z is the vibration velocity in the vertical direction of the sense coil 28.

The sensitivity of the vibration gyroscope constructed in accordance with an embodiment of the present invention can be derived from Equation 8 as shown in Equation 9 below.

In Equation 9, the sensitivity of the gyroscope is dependent on various variables. Among these variables, the sensitivity Vo / Ω is proportional to the height of the electrodes of the comb-drive actuator 12, ie comb-fingers, and inversely proportional to the spacing of the electrodes, as described above. In addition, the highest sensitivity Vo / Ω of the vibrating gyroscope according to the embodiment of the present invention is obtained by a thin and long polysilicon spring, and is matched to the resonant frequency of two vibration modes (detection by horizontal driving and vertical vibration). The ratio of sensitivity to angular velocity Ω is amplified by the Q factor of resonance, improving the operating performance of the sensor.

5A to 5H and 5I are views for explaining the manufacturing process of the polysilicon spring according to the present invention, which is a cross-sectional structure when the polysilicon spring 24 shown in FIGS. 2 and 3 is cut in the X-axis direction. Indicates. The gyroscope of the present invention described above will be described with reference to the above drawings in which the crystal form of silicon is formed on a silicon substrate having a " 110 " shape in which vertical etching is relatively easy.

After completion of alignment target etching on a bulk silicon substrate having a 110 crystal structure, a comb-like structure as shown in FIGS. 2 and 3 is patterned using a second mask. Thereafter, an oxide layer (TEOS SiO ₂ ) and a nitride layer (Si ₃ N ₄ ) layer are deposited and patterned to form a polysilicon spring using a third mask. This process forms a hole for contact between the polysilicon and the bulk silicon substrate (see FIG. 5A) having the 110 crystal orientation.

Then, a polysilicon layer is deposited thereon by LPCVD. At this time, the polysilicon layer deposited on the bulk silicon substrate by the above process is deposited to a thickness that is very suitable to be used as a spring, for example, about 5 μm thick. After the above process, a nitride film (Si ₃ N ₄ ) by LPCVD and an oxide film (SiO ₂ ) by TEOS are deposited on the top of polysilicon (see FIG. 5B).

When the polysilicon layer is deposited on the bulk silicon substrate by the above process, the structure of the polysilicon spring is patterned using a fourth mask, and the LPCVD nitride film (Si ₃ N ₄ ) is deposited on the silicon bulk etching. The formed polysilicon spring is protected during operation (FIG. 5D). And after removing the nitride film (Si ₃ N ₄₎ and a nitride film (Si ₃ N ₄₎ deposited on top of the polysilicon spring deposition subjected to conventional dry etching on a bulk silicon substrate in sequence (Fig. 5E and 5F) . At this time, the nitride film (Si ₃ N ₄ ) deposited on the side of the polysilicon spring by the dry etching is not removed, which is very important to protect the spring when bulk etching the 110 silicon substrate. Thereafter, the oxide film TEOS SiO ₂ is removed based on wet etching.

When the substrate is made in the shape of a polysilicon spring on the 110 silicon substrate by the above process, the silicon substrates of the edge areas which are symmetrical by anodically bonding the glass support 26 to the outer side of the lower surface of the silicon substrate. Are combined (FIG. 5G). Thereafter, when wet etching is performed, the silicon substrate having a thickness of 525 mu m having a 110 crystal structure is bulk etched in the vertical direction. FIG. 5H is a SEM photograph taken after the process of FIG. 5C and shows the shape of the polysilicon spring. FIG.

The reason why the bulk silicon substrate having the 110 crystal direction is used is because the etching efficiency in the vertical direction during wet etching is relatively good, and the present invention is not limited to only 110 substrates. Therefore, it can be seen that the structure of the gyroscope having the above-described configuration can be easily implemented using a semiconductor process on a bulk silicon substrate having 110 crystals.

In the above-described embodiment, the polysilicon spring supporting the vibrator on the substrate is formed on only one surface of the vibrator. However, by forming the vibrator up and down symmetrically, the signal sensed by the sensing coil by the vertical movement is differentially included in the signal. It should be noted that nonlinear components can be eliminated and the sensitivity can be doubled, and the present invention will claim to this category.

As described above, the present invention can be miniaturized by driving by electrostatic force and sensing acceleration by an electromagnetic force, and can improve the sensitivity of sensing angular velocity very well. In addition, since the driver is realized by a relatively simple method on a bulk silicon substrate having a structure of 110 crystals, the driver can be manufactured in a very small size, and mass production is very easy.

Claims (11)

In vibratory gyroscopes, A constant power actuator vibrating in the horizontal direction by the electrostatic force generated by the constant voltage input; And a magnetic force detecting unit which is magnetically coupled to the electrostatic force actuator and detects the amount of vertical movement of the actuator by the force of the Coriolis when the angular velocity is input by the magnetic induction voltage generated by the magnetic coupling. Vibration gyroscope with power drive and electromagnetic force detection. The method of claim 1, wherein the constant power actuator, A comb-vibrator formed with a predetermined size on a bulk silicon substrate having a predetermined thickness, Springs coupled between the comb-vibrator, the ground electrode and the spring pad, respectively, to support the comb-vibrator on the substrate; And a first and a second driving electrode positioned on the silicon substrate and spaced apart in the form of the vibrator and the comb to drive the actuator horizontally by input of a constant voltage having a different phase. Gyroscope. The vibratory gyroscope of claim 2, wherein the first and second driving electrodes have the same thickness as that of the silicon substrate. The vibratory gyroscope of claim 1, wherein the springs are symmetrically disposed on upper and lower surfaces of the vibrator. The vibratory gyroscope according to claim 1 or 4, wherein the electromagnetic force detector is symmetrically disposed on upper and lower surfaces of the vibrator. The vibratory gyroscope of claim 3, wherein the springs are polysilicon and are formed by etching after being deposited on the silicon substrate. The vibratory gyroscope according to claim 3, wherein the spring is metal plated using a microplating mold. The vibratory gyroscope according to any one of claims 2 to 4, wherein the springs are formed by surface microfabrication on the silicon substrate very thinly compared to the first and second driving electrodes. The vibratory gyroscope according to any one of claims 1 to 4, wherein the silicon substrate has a crystal direction of "110". The method of claim 5, wherein the electromagnetic force detection unit, An electromagnetic force generator having a vertical motion path of the conductor and generating magnetic flux of a predetermined density on the vertical motion path in response to a current supply; And cylindrical sensing coils respectively positioned at the centers of both sides of the vibrator and detecting the induced voltage generated when passing through the magnetic field of the vertical movement path and output through the springs connected to the spring pads. Vibrating gyroscope. The method of claim 10, wherein the electromagnetic force generator, A feed coil which generates a magnetic flux by supplying a predetermined current, And a permalloy core configured to induce magnetic flux generated from the feed coil in different directions and to concentrate on a vertical movement path of a conductor located at the center.