A decoupled tuning fork silicon micromechanical gyroscope capable of realizing interference modal isolation

Abstract

The application provides a decoupling type tuning fork silicon micromechanical gyroscope capable of realizing interference mode isolation, which comprises a substrate, a driving mass, a detecting mass, a coupling structure, a rotating frame and a spring beam. The driving mass and the detecting mass are supported by the spring beam and suspended in an XY plane, and the driving mass on the left and right sides of the gyroscope drives the detecting mass to vibrate in the Y axis direction in opposite phases in a driving mode; when a Z axis angular velocity is input, the detecting mass on the left and right sides is subjected to the Coriolis force and vibrates in the X axis direction in opposite phases; the rotating frame realizes the coupling between the driving masses, enables the driving masses to vibrate in the XY plane, and limits the displacement in other directions; and the coupling structure can inhibit the in-phase motion of the detecting mass. The gyroscope provided by the application can reduce the influence of process errors on the gyroscope, improve the robustness and thermal stability of the gyroscope, inhibit mechanical coupling interference, enhance the anti-linear acceleration response capacity, and realize the improvement of the performance and reliability of the gyroscope.

Description

Technical Field

[0001] This invention belongs to the field of Micro Electro Mechanical Systems (MEMS), specifically relating to a Z-axis MEMS gyroscope. Background Technology

[0002] Silicon micromechanical gyroscopes (MEMS) are inertial sensors fabricated on silicon semiconductors using micro-nano fabrication technology. They can be used to measure angular velocity or angular displacement. Compared with traditional optical gyroscopes and mechanical rotor gyroscopes, MEMS gyroscopes have advantages such as small size, high reliability, light weight, low power consumption, and mass production capability. They are currently widely used in many fields such as automobiles, industrial control, navigation systems, and consumer electronics, and have a very large market prospect and development potential.

[0003] The MEMS gyroscopes marketed are primarily capacitive vibratory gyroscopes. Their main components include a driving mass, a sensing mass, and a spring beam. These structures are suspended and movable under the connection and support of the spring beam. Under the action of a driving signal, the driving mass causes the sensing mass to vibrate in the driving direction. When an angular velocity is input perpendicular to the XY plane of the gyroscope, the sensing mass vibrates along the sensing direction under the action of the Coriolis force, causing a change in the sensing capacitance. The input angular velocity can be measured by detecting the change in its differential capacitance.

[0004] The tuning fork structure of a tuning fork-type micromechanical gyroscope requires high consistency between its two ends. Based on domestic manufacturing standards, the width error of the resonant beam is approximately 0.1µm. Since the resonant frequency is highly sensitive to dimensions, it's difficult to ensure that the resonant frequencies of the two ends are identical. Differences between the two ends lead to a decrease in the overall performance and stability of the gyroscope.

[0005] Furthermore, when manufacturing errors cause asymmetry in the driving mass at both ends of the tuning fork structure, existing driving coupling structures, such as rotating beams, will experience a deviation in the rotation center, leading to an increase in common-mode error. Even if the rotation center is forced back to its central position by the constraint of a short fixed beam in the middle of the beam, the high in-plane stiffness of the short fixed beam will reduce the displacement of the gyroscope's driving mode.

[0006] In particular, the detection masses at both ends of a traditional tuning fork gyroscope are uncorrelated, and the frequencies of the in-phase and out-of-phase modes of the detection masses are too small, making coupling interference between the two modes prone to occur. During gyroscope operation, the in-phase interference mode cannot be effectively isolated, and the detection masses are also easily affected by external linear acceleration, causing vibration output errors. To address these problems, a solution is proposed below. Summary of the Invention

[0007] The purpose of this invention is to provide a decoupled tuning fork silicon micromechanical gyroscope that can achieve interference mode isolation. By coupling the driving mass block and the detection mass block on the left and right sides respectively, the sensitivity of the gyroscope to process errors is reduced, and the robustness and thermal stability are improved. The coupling structure between the detection mass blocks on the left and right sides can increase the frequency difference between the interference mode and the detection mode, and reduce the mutual influence between the two. The driving mode and the detection mode of the micromechanical gyroscope are decoupled, reducing the mutual interference between modes.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A MEMS gyroscope is proposed, comprising a substrate, a driving mass, a sensing mass, a coupling structure, a rotating frame, and a spring beam; the planar structure of the gyroscope is symmetrical about the X-axis and the Y-axis.

[0010] Furthermore, the driving mass block is connected to at least one set of driving beams and fixed anchor points, thereby enabling it to be held within the XY plane; the driving mass block is provided with driving movable electrodes and driving detection movable electrodes, which, together with the corresponding driving fixed electrodes and driving detection fixed electrodes provided on the anchor points, can form driving capacitors and driving detection capacitors.

[0011] Furthermore, the rotating frame is connected to a fixed anchor point via a cross-shaped support beam, enabling it to vibrate around the fixed anchor point in the XY plane while restricting displacement in other directions; the rotating frame is connected to the driving mass blocks on the left and right sides via a connecting beam, thereby achieving coupling of driving forces.

[0012] Furthermore, the detection mass block is connected to the driving mass block at least through the detection isolation beam, thereby enabling it to move along the Y-axis direction following the driving mass block; the detection mass blocks on the left and right sides are connected through an inner coupling structure; the detection isolation beam and the coupling structure enable the detection mass block to suspend in the XY plane and maintain a movable state; the detection mass block is provided with a movable electrode of the detection electrode, which can form a variable detection capacitor with the corresponding fixed electrode set on the anchor point;

[0013] Furthermore, the coupling structure is composed of a plurality of spring beams, which extend along the X-axis direction and / or the Y-axis direction;

[0014] Furthermore, the coupling structure can not only suppress the in-phase motion of the detection mass block in the X-axis direction, but also decouple the motion of the detection mass block in the X-axis direction and the motion in the Y-axis direction.

[0015] Furthermore, the fixed adjusting electrode and the movable adjusting electrode disposed on the detection mass block constitute an adjusting capacitor; applying a suitable voltage to the adjusting capacitor can reduce the deflection of the detection mass block caused by process errors, thereby reducing the orthogonal error; applying a suitable voltage to the adjusting capacitor can adjust the detection frequency.

[0016] Furthermore, the driving mode of the gyroscope is to apply an alternating electrostatic driving force by applying an AC / DC voltage of a certain frequency to the driving capacitor. Under the drive of this electrostatic force, the driving mass blocks on the left and right sides drive the detection mass blocks to vibrate in opposite phases along the Y-axis direction respectively. The gyroscope can detect the motion state of the driving mode through the driving detection capacitor.

[0017] Furthermore, when the gyroscope is in the driving mode, if an angular velocity along the Z-axis is applied to the gyroscope from the outside, the detection mass blocks on the left and right sides will vibrate in opposite phases along the X-axis under the action of Coriolis force; the gyroscope can detect the displacement of the detection mode through the detection capacitor, thereby obtaining the angular velocity information in the Z-axis direction.

[0018] Preferably, the driving comb teeth are variable-pitch comb teeth electrodes or variable-area comb teeth electrodes; the two sets of driving capacitors input signals with the same amplitude but opposite phase to achieve differential driving;

[0019] Preferably, the detection comb teeth are variable-pitch comb teeth electrodes or variable-area comb teeth electrodes; the two sets of detection capacitors output signals with the same amplitude but opposite phase to achieve differential output;

[0020] Preferably, the driving detection comb teeth are variable-pitch comb teeth electrodes or variable-area comb teeth electrodes; the two sets of driving detection capacitors output signals with the same amplitude but opposite phase to achieve differential output;

[0021] Preferably, the structure can employ a coupling structure. The coupling structure consists of several spring beams along the X-axis and Y-axis directions, and oblique spring beams extending in the XY plane. The entire coupling structure is symmetrical about the Y-axis. This structure can distinguish the frequencies of in-phase and out-of-phase modes, suppressing inter-mode interference and improving the gyroscope's shock resistance in the X-axis direction.

[0022] The advantages of this invention are:

[0023] The gyroscope structure is symmetrical about the X and Y axes in the plane. When residual stress and packaging stress are introduced during processing or packaging, the symmetrical structure can effectively offset the external stress and reduce the sensitivity of the gyroscope to process errors. In particular, the symmetrical structure can reduce the influence of thermal stress introduced by changes in ambient temperature and improve the thermal stability of the gyroscope.

[0024] The gyroscope employs a rotating frame with anchor points. Compared to traditional rotating frames without anchor points, this allows the rotation center to be located at the center of the frame, ensuring the opposite phase and equal amplitude motion of the driving mass and improving driving accuracy. The rotating frame is connected to fixed anchor points via spring beams. Spring beams extending along the X and Y axes respectively allow the frame to rotate while restricting displacement in other directions, achieving separation of the driving mode from other interference modes and significantly reducing the impact of external linear acceleration on the driving structure.

[0025] The driving mass block adopts a compact tuning fork-type driving structure, which has good consistency and synchronization of driving motion. The driving mass block and the detection mass block are concentrated on the middle two sides and distributed in a block shape, which has good uniformity of structural size and reduces in-phase coupling interference caused by mass asymmetry when the gyroscope is working.

[0026] The detection mass blocks on the left and right sides are coupled through a coupling structure to suppress in-phase vibration of the detection mass blocks in the detection direction and improve detection accuracy. This coupling structure utilizes the stiffness difference along the X-axis and Y-axis to decouple the driving mode and the detection mode, achieving coupling of the detection mode without affecting the driving motion, thus reducing the mechanical coupling error of the gyroscope.

[0027] This invention proposes a coupling structure that can adjust the stiffness of in-phase and out-of-phase motion by changing the inclination angle of the intermediate inclined beam, thereby achieving the tuning of the structure's motion in the detection direction, distinguishing the frequencies of in-phase and out-of-phase modes, achieving the purpose of separating the detection mode from other interfering modes, suppressing inter-mode interference, and improving the detection output's ability to resist external vibrations. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the MEMS gyroscope structure according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the driving mode and detection mode of a MEMS gyroscope.

[0030] Figure 3 This is a schematic diagram of the coupling structure of a MEMS gyroscope.

[0031] Figure 4 This is a schematic diagram of a MEMS gyroscope structure using a preferred coupling structure in an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram of a preferred coupling structure for a MEMS gyroscope.

[0033] Figure 6 The influence of common-mode error in the driving direction on two types of MEMS gyroscopes with and without fixed anchor points in the rotating frame. Detailed Implementation

[0034] In the description of the embodiments of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "inner," "outer," "clockwise," "counterclockwise," "X," "Y," and "Z," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The accompanying drawings are schematic diagrams or conceptual diagrams, and the relationships between the thickness and width of each part, as well as the proportional relationships between each part, etc., are not entirely consistent with their actual values.

[0035] Figure 1 The Z-axis gyroscope of this example is shown, including fixed anchor points A1 to A5, spring beams S1 to S4, mass blocks M1 to M2, rotating frame F1, and coupling structure C1. Fixed anchor points A1 to A5 are connected to a base (not shown in the figure) and are fixed to the base.

[0036] Two mass blocks M1 are driving mass blocks, and two mass blocks M2 are detection mass blocks. Fixed anchor point A1 is a support anchor point. Electrodes are respectively installed on fixed anchor points A2 to A5.

[0037] The driving mass block M1 is equipped with a driving movable electrode, which, together with the driving fixed electrode on the fixed anchor point A2, forms a driving capacitor. The fixed anchor point A2.1 and the driving mass block M1 together form the driving capacitor C. DR+ The fixed anchor point A2.2 and the driving mass block M1 form the driving capacitor C. DR- .

[0038] The detection electrode consists of a movable detection electrode on the detection mass block M2 and a fixed detection electrode on the fixed anchor point A3. The fixed anchor point A3.1 and the detection mass block M2 together form the detection capacitor C. SS+ The fixed anchor point A3.2 and the detection mass block M2 together form the detection capacitor C. SS- .

[0039] The adjustable electrode C is formed by the adjustable movable electrode on the mass block M2 and the adjustable fixed electrode on the fixed anchor point A4. ADJ .

[0040] The driving mass block M1 is equipped with a driving detection movable electrode, which, together with the driving detection fixed electrode on the fixed anchor point A5, constitutes the driving detection electrode. The fixed anchor point A5.1 and the driving mass block M1 together form the driving detection capacitor C. DS+ The fixed anchor point A5.2 and the driving mass block M1 together form the driving detection capacitor C. DS- .

[0041] The driving mass block M1, the detection mass block M2, and the rotating frame F1 are connected to the fixed anchor point A1 via spring beams such as the driving beam S1, the detection isolation beam S2, the connecting beam S3, and the cross support beam S4, forming the movable part of the gyroscope.

[0042] Specifically, the driving mass M1 is connected to the fixed anchor point A1 via the driving beam S1, and to the detection mass M2 via the detection isolation beam S2. It is also connected to the rotating frame F1 via the connecting beam S3. The detection mass M2 is connected to the fixed anchor point A1 via the coupling structure C1, which also enables coupling between the detection mass blocks M2. The rotating frame F1 is connected to the driving mass M1 via the connecting beam S3, and also to the fixed anchor point A1 via the cross support beam S4.

[0043] The working principle of the Z-axis gyroscope can be divided into two parts: driving and Z-axis angular velocity detection.

[0044] like Figure 2 As shown in the driving mode, in the driving capacitor C DR+ and C DR- Applying AC or DC voltages of a certain frequency to both ends will generate alternating electrostatic force, causing the driving mass blocks M1 on the left and right sides to vibrate in opposite phases along the Y-axis. Under the action of the cross support beam S4, the rotating frame F1 will vibrate around the fixed anchor point A1, realizing the coupling of driving force and limiting the displacement of the driving mass blocks except for the opposite phase motion. Driven by the detection isolation beam S2, the detection mass block M2 also reciprocates in the Y-axis direction.

[0045] like Figure 2 As shown in the detection mode diagram, when there is an angular velocity input in the Z-axis direction, under the Coriolis effect, the detection mass blocks M2 on the left and right sides will move in opposite phases along the X-axis direction. Since the detection isolation beam S2 has a decoupling effect, the displacement caused by the movement of the detection mass block M2 along the X-axis direction will not be transmitted to the driving mass block M1, which helps to increase the stability of the driving mass block M1. The coupling structure C1 will change the stiffness in the X-axis direction, resulting in a frequency difference between the resonant frequencies of the in-phase and out-of-phase movements, thus avoiding mutual interference between the two modes.

[0046] Under the above motion state, the detection capacitor C SS+ and C SS- The capacitance value will change in the opposite way, for example, when the capacitance C is detected... SS+ When the capacitance value increases, the detection capacitor C SS- The capacitance value decreases, and the detection capacitance ΔC = ΔC can be obtained through differential calculation. SS+ -ΔC SS- The detection capacitor ΔC is proportional to the external angular velocity; by measuring ΔC, the input angular velocity can be obtained.

[0047] The driving mass block M1 moves in the Y-axis direction, causing the driving detection capacitor C to move. DS+ and C DS The capacitance value will change in the opposite direction accordingly, for example, when the driving detection capacitor C DS+ When the capacitance value increases, the detection capacitor C DS- The capacitance value decreases, and the detection capacitance ΔC can be obtained through differential calculation. D =ΔC DS+ -ΔC DS- Detecting capacitance ΔC D The displacement is proportional to the displacement of the driving mass block, which is determined by measuring ΔC. D This allows us to obtain the displacement of the driving mass block.

[0048] Figure 3 This invention proposes a coupling structure comprising spring beams C1.1 and C1.2 along the Y-axis and spring beam C1.3 along the X-axis, symmetrically distributed along the Y-axis. Spring beam C1.3 serves as a decoupling beam connecting the detection mass blocks on both sides. Spring beam C1.2 reduces the impact of the gyroscope's Y-axis motion on the coupling structure. When the detection mass blocks on both sides move in opposite phases, spring beam C1.1 remains stationary, achieving tuning of the structure's motion in the detection direction. When the detection mass blocks on both sides move in phase, spring beam C1.2 changes its stiffness in the X-axis direction, thereby distinguishing the frequencies of in-phase and out-of-phase modes, achieving separation of the detection mode from other interfering modes, and suppressing intermodal interference.

[0049] Figure 4 This is a MEMS gyroscope using a preferred coupling structure, wherein C2 is the preferred coupling structure. Figure 5 This invention proposes a preferred coupling structure comprising a spring beam C2.1 along the Y-axis, a diagonal spring beam C2.2, and a spring beam C2.3 along the X-axis, symmetrically distributed along the Y-axis and resembling a triangle. This coupling structure allows adjustment of the stiffness of in-phase and out-of-phase motions by changing the inclination angle of the central diagonal beam, achieving tuning of the structure's motion in the detection direction. This distinguishes the frequencies of in-phase and out-of-phase modes, achieving separation of the detection mode from other interfering modes, suppressing intermodal interference, and improving the detection output's resistance to external vibrations.

[0050] Spring beam C2.2 connects to the fixed anchor point, while spring beam C2.3 serves as a decoupling beam connecting the detection mass blocks on both sides. Spring beam C2.3 reduces the impact of the gyroscope's Y-axis motion on the coupled structure. When the detection mass blocks on both sides move in opposite phases, spring beam C2.2 remains stationary, achieving tuning of the structure's motion in the detection direction. When the detection mass blocks on both sides move in the same phase, the inclined spring beam C2.2 increases the stiffness in the X-axis direction, thereby improving the gyroscope's shock resistance and enhancing the detection output's ability to withstand external vibrations. It also distinguishes the frequencies of in-phase and out-of-phase modes, achieving the separation of the detection mode from other interfering modes and suppressing intermodal interference.

[0051] Due to limitations in the manufacturing process, the detection mass block M2 may deflect, causing the driving mode and the detection mode to interfere with each other, resulting in orthogonal errors. This is achieved through C... ADJ The electrostatic force generated by applying a suitable voltage can twist the detection mass block M2, reducing the influence of the driving mode on them.

[0052] In C ADJ The electrostatic force generated by applying a suitable voltage can adjust the stiffness in the X-axis direction. When the gyroscope is operating in mode separation mode, changing the resonant frequency of the detection mode can optimize the bandwidth of the gyroscope. When the gyroscope is operating in mode matching mode, the resonant frequencies of the driving mode and the detection mode are made equal.

[0053] The Z-axis gyroscope in this embodiment has the following advantages:

[0054] 1. The rotating frame uses anchor points. When there is linear acceleration, the cross support beam S4 increases the elastic stiffness in the X and Y axis directions, reducing the impact of external vibration on the structure. At the same time, the huge stiffness difference between the driving motion and other non-ideal motions can also distinguish the driving mode frequency from other interference mode frequencies, reducing the influence of interference modes and gyroscope drive.

[0055] 2. The rotation center of the rotating frame is located in the middle of the frame, ensuring that the driving mass blocks M1 on the left and right sides move in opposite phases, thus improving test accuracy. For example... Figure 6 As shown, without anchor points, the rotation center of the driving mode is significantly shifted due to the influence of common mode error.

[0056] 3. The driving mass block M1 adopts a compact tuning fork drive structure with good structural size uniformity and good motion consistency and synchronization between the left and right structures.

[0057] 4. The two detection mass blocks M2 are coupled using a coupling structure. This coupling structure can distinguish the resonant frequencies of the detection mode and the interference mode, thereby suppressing the in-phase motion of the detection mass blocks and reducing common-mode error.

[0058] 5. The coupling structure can decouple the driving mode from the detection mode, thereby greatly reducing the coupling between the two modes under non-ideal conditions.

[0059] 6. The coupling structure can avoid the problem of different resonant frequencies at the two ends of the gyroscope due to manufacturing errors, thereby improving the stability and robustness of the gyroscope and reducing the sensitivity of the gyroscope to manufacturing errors.

[0060] 7. The preferred coupling structure will have higher stiffness when encountering impact, enhancing the gyroscope's resistance to linear acceleration.

[0061] 8. The detection capacitors on the two detection mass blocks M2 form a differential, thereby eliminating interference caused by external acceleration signals in the detection direction and improving the anti-interference capability of the system. The angular velocity signal is a differential signal, which improves the sensitivity.

[0062] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A decoupled tuning fork silicon micromechanical gyroscope capable of isolating interference modes, comprising a substrate, a driving mass, a sensing mass, a coupling structure, a rotating frame, and a spring beam, wherein the gyroscope is symmetrical about the X-axis and Y-axis, characterized in that, Several fixed anchor points are fixed on the base. The rotating frame is connected to the fixed anchor points through a cross-shaped support beam to achieve coupling between the driving mass blocks on both sides. The detection mass blocks located on the left and right sides are coupled through a coupling structure. The driving mass block is connected to the fixed anchor point via a driving beam, and the detection mass block is connected to the driving mass block via a detection isolation beam, so that the driving mass block and the detection mass block are kept in the XY plane. Movable electrodes are provided on both the driving mass block and the detection mass block, and fixed electrodes are provided on the fixed anchor point. The movable electrodes and the corresponding fixed electrodes constitute a driving capacitor, a driving detection capacitor, and a detection capacitor. The rotating frame has stiffness along the X-axis and Y-axis directions, and is suitable for vibrating around a fixed anchor point in the XY plane while restricting displacement in other directions.

2. A decoupled tuning fork silicon micromechanical gyroscope capable of achieving interference mode isolation as described in claim 1, characterized in that, The rotating frame is connected to the driving mass blocks on the left and right sides by connecting beams, thereby realizing the coupling of driving force. The coupling structure is composed of spring beams arranged along the X-axis and / or Y-axis, and is symmetrically distributed along the Y-axis. The coupling structure connects the detection mass blocks on both sides. The fixed anchor point is provided with an adjustable fixed electrode, and the detection mass block is provided with an adjustable movable electrode. The adjustable fixed electrode and the adjustable movable electrode constitute an adjustable capacitor. The adjustable capacitor can reduce the orthogonal error between the driving mode and the detection mode and optimize the gyroscope bandwidth. Applying an AC / DC voltage of a certain frequency to the driving capacitor generates an alternating electrostatic driving force. Under the drive of this electrostatic force, the driving mass blocks on the left and right sides of the gyroscope cause the detection mass blocks to vibrate in opposite phases along the Y-axis. When there is a Z-axis angular velocity input, the detection mass blocks on the left and right sides are subjected to Coriolis force and vibrate in opposite phases along the X-axis. The intermediate coupling structure causes the detection mass blocks to move in opposite phases. The detection capacitor on the detection mass block changes, and the input angular velocity can be measured by the change in the output capacitance.

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