CN1948906B - Capacitive type complete decoupling horizontal axis miniature mechanical gyro - Google Patents

Abstract

The invention relates to a capacitive fully decoupled horizontal-axis micromechanical gyroscope, which is characterized in that it includes a glass substrate, a driving capacitor, a driving feedback capacitor, a detection capacitor, a driving mass, an asymmetric mass and a detection mass; The quality block is located in the center, and the two ends of the drive mass block are respectively connected to the anchor points fixed on the glass substrate through the laterally arranged driving mode elastic beams; the movable electrodes of the drive capacitor and the drive feedback capacitor are connected to the drive mass block, and the drive The fixed electrodes of the capacitor and the driving feedback capacitor are fixed on the glass substrate; the two ends outside the asymmetric mass block are respectively connected to the detection mass block through the driving mode elastic beams arranged horizontally, and the two ends inside the asymmetric mass block are respectively connected through the vertical The set detection mode elastic beam is connected to the drive mass; the movable electrodes of the detection capacitor are fixed on both sides of the detection mass, and the fixed electrodes of the detection capacitor are fixed on the glass substrate; the two ends of the detection mass are respectively arranged vertically The detected modal elastic beams are connected by anchors fixed on the glass substrate. The invention has a double decoupling structure, which can well suppress parasitic effects and reduce drift; and has good linearity and off-axis sensitivity.

Description

A capacitive fully decoupled horizontal axis micromachined gyroscope

technical field

The invention relates to a micro-mechanical gyroscope, in particular to a capacitive fully decoupled horizontal-axis micro-mechanical gyroscope using vertical comb-tooth capacitance detection.

Background technique

Micromechanical gyroscopes are a type of inertial sensor that uses Coriolis force to measure the angular velocity of an object's rotation. Due to the use of micro-electromechanical system (MEMS) technology, micro-mechanical gyroscopes have the advantages of small size, light weight, and low cost. They have very broad application prospects in inertial navigation, weapon guidance, automobiles, and consumer electronics. In order to obtain the complete information of the object's rotation, it is necessary to detect the angular velocity signals of three axes at the same time, which requires a combination of multi-axis gyroscopes or three single-axis gyroscopes. Using MEMS technology to process three single-axis gyroscopes on a single chip at the same time is a good solution. The orthogonal alignment between the axes of the devices in this solution is automatically realized through structural design, which avoids assembly problems and can reduce the volume and weight of the entire system. In addition, the gyroscope structure of each unidirectional axis in the three-axis gyroscope realized by this technology can be independently optimized, so that higher performance can be obtained.

Judging from the current progress of gyroscope research in the world, the research on Z-axis gyroscopes (inertial sensors used to detect angular velocity perpendicular to the surface of the device) has been quite mature, and high-performance Z-axis gyroscopes have been frequently reported and have reached a practical level. There is still a big gap in the research of X and Y axis gyroscopes (also known as horizontal axis gyroscopes, inertial sensors used to detect the angular velocity parallel to the surface of the device). Therefore, designing and manufacturing a high-performance horizontal-axis micromachined gyroscope is a key technology to realize the integration of three-axis gyroscopes.

When the gyro is working, the mechanical coupling of the two modes of driving and detection will seriously affect the performance of the gyro. The solution is to increase the complexity of the structure, so that the driving part and the detection part move independently to realize the so-called decoupling structure. Decoupling is divided into first-level decoupling and second-level decoupling (full decoupling). The first-level decoupling structure is that the motion of the driving (or detecting) part is independent, while the motion of the detecting (or driving) part will be affected by the motion of the driving (or detecting) part. Full decoupling means that the driving and detection movements are completely independent and do not affect each other. At present, almost all high-performance Z-axis gyroscopes in the world have a fully decoupled structure. Such as the gyroscope design scheme (Proc.Transducers2005) of Gomez et al. in Germany, and the design scheme (MEMS2006) of Alper et al. of Middle East Technical University in Turkey. The common feature of this type of gyroscope is that it adopts bulk silicon technology with a high aspect ratio, and has a large mass and a large sensitive capacitor; the driving and detection parts are constrained by independent elastic beams, and its motion is only related to the sensitive mass, and they are mutually independent. It is completely independent, realizes a fully decoupling structure, suppresses parasitic effects well, and effectively improves device performance. For the horizontal-axis gyroscope that needs to detect the movement in the Z direction, due to the limitation of the MEMS process characteristics, a more complex elastic beam is required to realize the out-of-plane movement, and it is difficult to realize a fully decoupled structure. Most of the existing solutions only achieve one-level decoupling, such as The torsional gyro structure designed by W.Geiger et al. in Germany (Sensors and Actuators A 2002), and the gyro scheme (Proc.Transducers2005) proposed by Yang Zhenchuan et al. in China using unequal-height sparse-tooth capacitance detection. The common feature of this type of gyroscope is that the driving mode has one degree of freedom, and the detection mode has two degrees of freedom. The influence of the detection mode on the driving mode is suppressed, and the parasitic effect is reduced. However, the pickup circuit connected to the detection mode is jointly affected by the two modes, which will also cause parasitic effects such as quadrature error, which limits the performance of the device.

Contents of the invention

The purpose of the present invention is to provide a high-sensitivity capacitive fully decoupled horizontal-axis micro-mechanical gyroscope.

To achieve the above object, the present invention adopts the following technical solutions: a capacitive fully decoupled horizontal axis micromachined gyroscope, characterized in that: it includes a glass substrate, a drive capacitor, a drive feedback capacitor, a detection capacitor, a drive mass, no A symmetrical mass and a detection mass; the driving mass is located in the center, and the two ends of the driving mass are respectively connected to the anchor points fixed on the glass substrate through the driving mode elastic beams arranged laterally; the driving The movable electrodes of the capacitor and the driving feedback capacitor are connected to the driving mass, and the fixed electrodes of the driving capacitor and the driving feedback capacitor are fixed on the glass substrate; the two ends of the asymmetric mass are respectively passed through The driving mode elastic beam arranged horizontally is connected to the detection mass, and the inner two ends of the asymmetric mass are respectively connected to the driving mass through the detection mode elastic beam arranged vertically; the movable detection capacitor The electrodes are fixed on both sides of the detection mass, and the fixed electrodes of the detection capacitor are fixed on the glass substrate; the two ends of the detection mass are respectively connected and fixed on the Anchor points on the glass substrate.

The detection sensitive capacitor adopts a double-terminal unequal height vertical sparse-tooth capacitor structure.

The detection capacitors located on the left and right sides are equally divided into four groups on each side, and the two groups of capacitors in the middle of each side are combined into a middle group of capacitors, so that the middle group of capacitors on each side is the sum of the upper and lower two groups of capacitors ; The position of the middle group of capacitors on each side is higher than the position of the fixed teeth, and the position of the upper and lower capacitors on each side is lower than that of the fixed teeth. The upper and lower sets of capacitors on the other side form a detection capacitor, and form two detection capacitors in total to form a differential capacitor pair.

The driving mass and the asymmetric mass of the present invention have a degree of freedom in the Y direction under the constraints of two sets of driving elastic beams. There will be relative movement, and the detection mass block is constrained by the detection elastic beam, and has no degree of freedom in the Y direction, so the present invention does not affect the motion of the detection part when the drive part moves; The asymmetric mass block takes the detection elastic beam as the axis, and can do torsional movement. The detection mass block and the asymmetric mass block are connected by a driving elastic beam, and there is no relative displacement between the two when torsion. The driving mass block is driven by the elastic beam. Constraints, no torsional movement occurs, so the detection component of the present invention does not affect the movement of the driving component when it moves. That is to say that the motion of the driving part (comprising driving mass and movable coarse teeth) and detection part (comprising proof mass and movable coarse teeth) of the present invention is only associated with the asymmetric mass respectively, and the motion between them is independent movements.

The present invention has the following advantages due to the adoption of the above technical scheme: 1. The drive mass and the detection mass of the present invention are constrained by independent elastic beams, and their motion is only associated with the asymmetric mass, and the motion between them is Mutually independent movements, that is, the present invention has a double decoupling structure, which can well suppress the mechanical coupling between the driving mode and the detection mode, thereby suppressing parasitic effects and effectively reducing drift. 2. The detection of the present invention adopts the differential detection of two sets of double-terminal unequal-height comb capacitances. According to the distribution scheme in the present invention, the capacitance change caused by torsional motion is a differential mode signal, and the capacitance changes caused by small displacements in other directions are common Modulo signal, so that the gyro has good linearity and off-axis sensitivity.

Description of drawings

Figure 1a and Figure 1b are schematic diagrams of the working principle of the double-terminal unequal height sparse-tooth capacitor type I of the present invention

Figure 2a and Figure 2b are schematic diagrams of the working principle of type II double-ended unequal-height sparse-tooth capacitors of the present invention

Fig. 3 is a schematic diagram of the structure of the present invention.

Fig. 4a is a schematic diagram of the driving mode of the present invention.

Fig. 4b is a schematic diagram of the detection mode of the present invention.

Detailed ways

For the convenience of describing the present invention, two kinds of double-terminal unequal-height vertical comb capacitors involved in the present invention will be described first.

As shown in Figure 1a and Figure 1b, it is the working principle diagram of type I double-terminal unequal-height comb capacitor. 1 and 2 have the same thickness, and the top and bottom thereof are higher than the top and bottom of the fixed electrodes 1 and 2 . In the initial position (as shown in Figure 1a), the overlapping areas of the electrodes of the two capacitors are the same, and the values are equal. When the movable electrode 3 is twisted counterclockwise at a small angle (as shown in Figure 1b), the overlapping area between the fixed electrode 1 and the movable electrode 3 increases, that is, the sensitive capacitance increases; The overlapping area is reduced, that is, the sensitive capacitance is reduced. When the movable electrode 3 is twisted clockwise at a small angle, the change of the sensitive capacitance is opposite to that of the counterclockwise twist, and the differential value of the two sensitive capacitances is proportional to the twist angle.

As shown in Figure 2a and Figure 2b, it is the working principle diagram of type II comb-tooth capacitor with unequal height at both ends. 1 and 2 have the same thickness, and their tops and bottoms are lower than the tops and bottoms of the fixed electrodes 1 and 2 . Its working principle is basically the same as the double-terminal unequal height sparse-tooth capacitor type I, but the change of the sensitive capacitance is opposite to that of the double-terminal unequal-height sparse-tooth capacitor type I, so as to realize differential mode signal detection.

As shown in Figure 3, the present invention is a horizontal axis (X-axis) micromechanical gyroscope, which includes a drive capacitor 4, a drive feedback capacitor 5, detection capacitors 6, 7, a detection mass (outer frame) 8, and an asymmetric mass 9 , drive mass 10, drive modal elastic beams 11, 12, detect modal elastic beams 13, 14, anchor points 15, 16 and glass substrate. This embodiment includes eight groups of driving capacitors 4 , each group of driving capacitors 4 includes a movable electrode connected to the driving mass 10 and a fixed electrode connected to the glass substrate, and the driving capacitor 4 adopts a push-pull driving method. There are two groups of driving feedback capacitors 5, which are used to provide feedback signals for the driving capacitor 4, and closed-loop driving can be realized through an external circuit. The detection capacitors 6 and 7 are located on both sides of the detection mass 8 and connected to the detection mass 8. The detection capacitors 6 and 7 are a pair of differential sensitive capacitors, and their distribution scheme will be described in detail later. The present invention adopts a frame structure, and the detection mass 8 is connected with two detection mode elastic beams 14 and fixed on the glass substrate through two anchor points 16 . The detection mass 8 is connected to the asymmetric mass 9 through four driving mode elastic beams 12 . The asymmetric mass block 9 is a semi-closed frame, and the mass is mainly concentrated on the left side. The asymmetric mass 9 is connected to the driving mass 10 through two detection mode elastic beams 13 . The driving mass 10 is rectangular, and the driving capacitor 4 and the feedback capacitor 5 are connected to both sides of the driving mass 10 . The driving mass 10 is connected with four driving mode elastic beams 11 and fixed on the glass substrate through anchor points 15 .

The present invention is a horizontal axis gyroscope with full decoupling structure, and its decoupling principle is as follows:

The driving mode elastic beams 11 and 12 have relatively small stiffness in the Y direction, and the driving mass 10 and the asymmetric mass 9 are constrained by the driving mode elastic beams 11 and 12 respectively, so they have degrees of freedom in the Y direction. The driving mass 10 and the asymmetric mass 9 are connected by a detection mode elastic beam 13, and the stiffness of the detection mode elastic beam 13 in the Y direction is much greater than that of the driving mode elastic beams 11, 12, so the driving mass 10 and the The asymmetric mass 9 has no relative movement in the Y direction. The detection mass 8 is constrained by the detection modal elastic beam 14, and the detection modal elastic beam 14 also has a very large stiffness in the Y direction, so the detection mass 8 has no degree of freedom in the Y direction. That is, the driving mode of the gyroscope of the present invention is that the driving mass 10 and the asymmetric mass 9 perform simple harmonic vibration in the Y direction, while the detection mass 8 remains stationary (as shown in FIG. 4 a ).

By the same token, the detection mode elastic beams 13 and 14 have small Y-axis torsional stiffness, while the Y-axis torsional stiffness of the driving mode elastic beams 11 and 12 is extremely large. Therefore, the asymmetric mass 9 and the detection mass 8 have a degree of freedom in the Z direction (torsional motion along the axial direction of the detection modal elastic beam) under the constraints of the detection modal elastic beams 13 and 14 respectively; the driving mass 10 is driven by Modal elastic beam 11 constraints, no Z-direction degrees of freedom. That is, the detection mode of the gyroscope of the present invention is that the detection mass 8 and the asymmetric mass 9 perform torsional motion along the central axis of the device (Y direction), while the driving mass 10 remains stationary (as shown in FIG. 4b ).

The micromechanical gyroscope of the present invention utilizes the Coriolis force to measure the angular velocity of the object, as shown in Figure 3, the drive capacitor 4 drives the device with electrostatic force during operation, so that the drive mass 10 and the asymmetric mass 9 vibrate along the Y direction; The proof mass has no stiffness in the Y direction and remains static. When the system has an X-direction angular velocity (rotating with the X-direction as the axis), both the drive mass 10 and the asymmetric mass 9 are subjected to a Coriolis force in the Z-direction (perpendicular to the substrate). Wherein the drive mass 10 will not produce axial rotation because the center of mass is on the torsion axis, and maintains the original motion state; the asymmetric mass 9 will drive the detection mass 8 and the connecting mass under the action of the Coriolis force. The movable electrodes of the detection capacitors 6 and 7 on the proof mass 8 perform torsional motion along the axial direction of the elastic beam of the detection mode, thereby causing the detection capacitors 6 and 7 to change, and the angular velocity information input by the X axis can be obtained through the detection circuit.

The above analysis assumes that the elastic beam is an ideal one-dimensional elastic beam (with certain stiffness in one direction and infinite stiffness in other directions). However, the stiffness of the actual elastic beam in other directions is not infinite, which means that the proof mass 8 is not an ideal single-degree-of-freedom mass block. When there is an acceleration input in a certain direction, it may have a small displacement in this direction, which will affect The off-axis sensitivity of the gyro. The present invention adopts the following scheme to solve this problem: the left and right detection capacitors are equally divided into four groups, and the middle two groups on each side are combined into a middle group, that is, the capacitance of the middle group is the sum of the upper and lower two groups of capacitances. Taking the capacitor on the left as an example, the middle group capacitor is defined as the double-terminal unequal height sparse-tooth capacitor type I mentioned above, and the upper and lower two groups of capacitors are defined as the above-mentioned double-terminal unequal height sparse-tooth capacitor II type; the distribution and definition of the capacitance on the right is the same as on the left. Among them, the left middle group (Type I) capacitor and the right upper and lower two groups (II type) capacitors constitute the detection capacitor 6; the right middle group (I type) capacitor and the left upper and lower group (II type) capacitors A detection capacitor 7 is formed, and the detection capacitor 6 and the detection capacitor 7 form a differential capacitance pair. When the proof mass 8 is twisted counterclockwise at a small angle with the axial direction of the detection mode elastic beam 14 as the axis, the I-type capacitance of the middle group on the left side with unequal height and sparse tooth capacitance increases, and the upper and lower groups on the right side have unequal heights. The type II capacitance of the sparse tooth capacitance increases, that is, the capacitance of the detection capacitor 6 increases; Small, that is, the capacitance of the detection capacitor 7 decreases. When the detection mass 8 has a slight displacement in the Y direction, the changes of the capacitances on the left and right sides are consistent, and the changes of the detection capacitances 6 and 7 are also consistent. When the detection mass 8 has a small displacement in the X direction, for example, when it moves to the positive direction (right) of X, the capacitance on the left side decreases, the capacitance on the right side increases, and the changes are equal, then the detection capacitances 6 and 7 are respectively constant. Through the above analysis, it can be seen that for the detection capacitors 6 and 7, the capacitance changes of the detection capacitors 6 and 7 caused by the torsional movement of the detection mass 8 with the Y direction as the axis are differential mode signals, and the detection mass 8 is in the X or Y direction. When a slight displacement occurs, the capacitances of the detection capacitors 6 and 7 are common-mode signals or remain unchanged.

Claims (3)

1. A capacitive full decoupling horizontal axis micromachined gyroscope is characterized in that: it comprises a glass substrate, a drive capacitor, a drive feedback capacitor, a detection capacitor, a drive mass, an asymmetric mass and a detection mass; The driving mass is located in the center, and the two ends of the driving mass are connected and fixed on the anchor point of the glass substrate through a set of laterally arranged driving mode elastic beams; the driving capacitor and the movable electrode of the driving feedback capacitor Connected to the driving mass, the fixed electrodes of the driving capacitor and the driving feedback capacitor are fixed on the glass substrate; the two ends of the asymmetric mass are elastically driven by another set of laterally arranged driving modes. The beam is connected to the detection mass, and the two ends inside the asymmetric mass are connected to the drive mass through a set of vertically arranged detection mode elastic beams; the movable electrode of the detection capacitor is fixed on the detection On both sides of the mass block, the fixed electrodes of the detection capacitor are fixed on the glass substrate; the two ends of the proof mass block are connected and fixed on the outside of the proof mass block through another set of vertically arranged detection mode elastic beams on the anchor point of the glass substrate. 2. A capacitive fully decoupled horizontal-axis micromechanical gyroscope according to claim 1, wherein the detection capacitor adopts a double-terminal unequal-height vertical sparse-tooth capacitor structure. 3. A capacitive full-decoupling horizontal-axis micromachined gyro as claimed in claim 1 or 2, characterized in that: the detection capacitors located on the left and right sides are equally divided into four groups on each side, and each The two sets of capacitors in the middle of the side are combined into a middle set of capacitors, so that the middle set of capacitors on each side is the sum of the upper and lower sets of capacitors; The upper and lower sets of capacitors on one side are movable and the positions of the teeth are lower than the positions of the fixed teeth. The middle set of capacitors on one side and the upper and lower sets of capacitors on the other side form a detection capacitor, and a total of two detection capacitors are formed. differential capacitor pair.

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