A multi-ring resonant MEMS gyroscope with high processing error tolerance

Abstract

The invention discloses a multi-ring resonant gyroscope with high processing error tolerance, comprising a supporting bottom layer (1), an oxidized insulating layer (2), and a device structure layer (3); the device structure layer comprises an anchoring platform, a plurality of concentric ring structures, an inter-ring connecting beam, and an electrode; the electrode further comprises a working electrode and an island electrode. The multi-ring resonant gyroscope proposed by the invention not only has a completely symmetrical resonant structure and a high processing error tolerance, but also solves the problems of large orthogonal error in the output of the multi-ring resonant gyroscope and large frequency splitting of two working modes. More importantly, the designed double folded beam spoke structure effectively reduces the influence of processing errors and greatly improves the performance of the gyroscope.

Description

Technical Field

[0001] The invention relates to a resonant MEMS gyroscope, in particular to a multi-ring resonant MEMS gyroscope with high processing fault tolerance. Background Art

[0002] A gyroscope is a sensor used to sense the rotation of a carrier. It has been widely used in navigation and guidance, industrial robots, gesture recognition, optical image stabilization, 3D games and other fields. The high-precision gyroscopes currently in use mainly include mechanical rotor gyroscopes, laser gyroscopes and hemispherical resonant gyroscopes. The advantages of these gyroscopes are high precision, but their large size, high power consumption, complex process and high manufacturing cost limit their application in smaller carriers. Micromechanical gyroscopes manufactured based on micro-electro-mechanical systems (MEMS) technology have incomparable advantages in size, power consumption and cost, and can meet the needs of the rapid development of aerospace industry, inertial navigation and other fields. Vibration gyroscopes are inertial sensors that can measure the angle or rate of rotation around a specific axis based on the Coriolis effect. For MEMS vibration ring gyroscopes, the resonant ring enters the driving mode through electrostatic oscillation. When the gyroscope has an angular velocity input, the generated Coriolis force transfers the gyroscope from the excited driving mode to the sensing mode, and the two working modes form a 45° angle. When the resonant frequencies of the driving mode and the sensing mode are close to or equal, it is called modal matching. At this time, the displacement amplitude of the sensing mode is the largest and the maximum sensitivity can be achieved.

[0003] From the research of Dr. DDLynch in the United States, it can be known that the main source of error in the axisymmetric resonant gyroscope is the mismatch of the stiffness of the resonant structure. The asymmetric stiffness of the resonant structure in the driving axis and the sensing axis makes it have an orthogonal main stiffness axis, and there is a stiffness axis deviation angle with the reference coordinate system. Therefore, the gyroscope will output an orthogonal error, which hinders the improvement of the gyroscope performance. Compared with the traditional multi-ring resonant gyroscope, the multi-ring resonant MEMS gyroscope with high processing tolerance designed by the present invention has better stiffness consistency in all directions in the XY plane. When the processing error causes the inter-ring connecting spokes and the resonant ring width of the gyroscope to change, the gyroscope structure proposed by the present invention has a small change in stiffness in all directions in the XY plane, while when the inter-ring connecting spokes and the resonant ring width of the traditional gyroscope change, the stiffness of the gyroscope in different directions in the XY plane is quite different. Therefore, the multi-ring resonant MEMS gyroscope structure designed in this article can not only significantly reduce the influence of the processing error, reduce the deviation angle between the main stiffness axis and the gyroscope reference coordinate, but also reduce the frequency cracking between the two working modes, thereby improving the performance of the gyroscope. Summary of the invention

[0004] In view of common processing methods and technical solutions, the present invention provides a multi-ring resonant MEMS gyroscope with high processing error tolerance.

[0005] A multi-ring resonant MEMS gyroscope with high processing error tolerance provided by the present invention includes a supporting bottom layer, an oxide insulating layer, and a device structure layer;

[0006] The supporting bottom layer is located at the bottom and is used to set the oxidation insulation layer;

[0007] The oxide insulating layer is arranged on the top of the supporting bottom layer, and the top of the oxide insulating layer is used to arrange the device structure layer;

[0008] The device structure layer is arranged on the top of the oxide insulating layer, and also includes an anchoring platform, a plurality of concentric ring structures, connecting beams between the rings, and electrodes;

[0009] The anchoring platform is circular and concentric with the supporting bottom layer, and an oxidized insulating layer is provided at the bottom of the anchoring platform;

[0010] The multiple concentric ring structures are arranged on the anchoring platform through inter-ring connecting beams, no oxidized insulating layer is arranged at the bottom of the multiple concentric rings, and the multiple concentric rings are divided into multiple groups, the first ring close to the anchoring platform is arranged as one group, and the remaining rings far away from the first ring are arranged as each group including two rings;

[0011] Preferably, the plurality of concentric rings are arranged to have unequal widths, and the width gradually increases or decreases from the ring close to the anchoring platform to the ring far away from the anchoring platform, or the width of one or more of the plurality of concentric rings may be increased or decreased;

[0012] The inter-ring connecting beams include double folding beams and straight arm shapes; a plurality of straight arm connecting beams uniformly distributed in the circumferential direction are arranged between the anchoring platform and the first circular ring; a plurality of double folding beam connecting beams uniformly distributed in the circumferential direction are arranged between the first circular ring and a group of concentric circular rings close to the first circular ring, and between the remaining groups of concentric circular rings; the radial directions of the corresponding double folding beam connecting beams correspond to each other and are staggered from the radial directions of the straight arm connecting beams; the two concentric circular rings in each group of concentric circular rings are arranged as straight arm connecting beams;

[0013] Preferably, the double-folded beam spokes between the first circular ring and a group of concentric circular rings close to the first circular ring and between the remaining groups of concentric circular rings are composed of two independent beams; the straight-arm-shaped connecting beam between the anchoring platform and the first circular ring is composed of two independent beams; the circular rings that form a group of two concentric circular rings are connected by a single straight-arm-shaped connecting beam;

[0014] The double folded beam spoke stiffness coefficient is expressed as follows: l, d, t are the length, width, and thickness of the beam, respectively; E is the elastic modulus of the material; K is the stiffness coefficient; F is the tensile force on the cantilever beam; and M is the bending moment on the cantilever beam;

[0015] According to the stiffness coefficient formula of ordinary cantilever beam under bending moment and stretching, we can know that:

[0016]

[0017]

[0018] When a cantilever beam is subjected to bending moment, the stiffness coefficient is inversely proportional to the cube of the beam length. When a cantilever beam is subjected to tension, the stiffness coefficient is inversely proportional to the first power of the length.

[0019] In the present invention, the single folded beam spoke is composed of four beams. The stiffness coefficient of each beam of the single folded beam spoke under the action of bending moment and tension is as follows, wherein l1, l2, l3, and l4 are the four beams constituting the single folded beam spoke respectively:

[0020] l1=l4,l2=l3

[0021]

[0022]

[0023]

[0024]

[0025] The stiffness coefficient of the single folding beam spoke designed by the present invention can be equivalent to the stiffness coefficient of the series spring, and k is the stiffness coefficient of a single beam constituting the single folding beam spoke:

[0026] k l1 =k l4 , k l2 =k l3

[0027]

[0028] The stiffness coefficients of the single folded beam spokes under the action of bending moment and tension are:

[0029]

[0030]

[0031] In the double-folded beam spoke designed by the present invention, l2 is much larger than l1, and l2 is much larger than d. The change in stiffness of the double-folded beam spoke under the action of bending moment and tension mainly depends on the change in spoke length, and the change in spoke width has almost no effect on stiffness.

[0032] The electrodes also include working electrodes and island electrodes, and both types of electrodes have an oxidized insulating layer at the bottom;

[0033] The working electrodes are arranged in a plurality and are evenly distributed between two groups of concentric rings, and sixteen pairs of electrodes are arranged between each two groups of concentric rings for inputting driving signals or outputting detection signals;

[0034] The island electrodes are arranged on both sides of the outer side of the double folded beam spokes and inside the double folded beam spokes. Eight double folded beams are arranged between every two groups of concentric rings. Each double folded beam spoke corresponds to a group of island electrodes. A group of island electrodes includes three island electrodes for isolating the working electrode from the double folded beam spokes.

[0035] Preferably, the working electrode, the island electrode and the top of the anchoring platform are all provided with a conductive layer, and the conductive layer can be a metal such as gold, aluminum, chromium, etc.

[0036] The structural scheme designed by the present invention has the following significant advantages:

[0037] 1. The multi-ring resonant MEMS gyroscope designed in this paper is combined with multiple concentric rings and double-folded beam-shaped and straight-arm spokes. Since the change in the stiffness of the beam under the action of bending moment and tension mainly depends on the change in the length of the spoke, the change in the spoke width has almost no effect on the stiffness. Therefore, it has a high processing tolerance and can adapt to different processing technologies;

[0038] 2. The double folded beam spokes in the multi-ring resonant MEMS gyroscope designed in this paper have good stiffness consistency when subjected to tension and bending moments, and the orthogonal main stiffness axis has a small deflection angle with the reference coordinate axis, which effectively reduces the gyroscope orthogonal error output;

[0039] 3. The length of the double folded beam spokes in the multi-ring resonant MEMS gyroscope designed in this paper is longer than that of the traditional straight-arm spokes, which prolongs the heat transfer time of the gyroscope and significantly reduces energy dissipation, which is beneficial to the improvement of the quality factor and the sensitivity of the gyroscope;

[0040] 4. The multi-ring resonant MEMS gyroscope designed in this paper has small frequency splitting between the two working modes and works in a mode matching state, which significantly improves the effective displacement of the sensing mode and improves the sensitivity of the gyroscope.

[0041] 5. The multi-ring resonant MEMS gyroscope designed in this paper has multiple concentric ring structures with unequal ring widths. The combination of multiple concentric ring structures with unequal widths and connecting beams between the rings effectively improves the working modal quality. The gyroscope has a large working displacement response and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A top view of the multi-ring resonant MEMS gyroscope with high processing error tolerance proposed by the present invention;

[0043] Figure 2A three-dimensional diagram of the multi-ring resonant MEMS gyroscope resonant structure with high processing error tolerance proposed by the present invention;

[0044] Figure 3 A schematic cross-sectional view of a multi-ring resonant MEMS gyroscope with high processing error tolerance proposed by the present invention;

[0045] Figure 4(a) , 4(b) A top view of the structure and electrode arrangement of a multi-ring resonant MEMS gyroscope device with high processing tolerance proposed by the present invention;

[0046] Figure 5(a) , 5(b) This is a structural diagram of a multi-ring resonant MEMS gyroscope spoke with high processing tolerance proposed by the present invention;

[0047] Figure 6 This is a driving modal diagram of a multi-ring resonant MEMS gyroscope with high processing fault tolerance proposed by the present invention;

[0048] Figure 7 This is the sensing modal diagram of the multi-ring resonant MEMS gyroscope with high processing fault tolerance proposed by the present invention;

[0049] Figure 8 This is a driving mode diagram of a multi-ring resonant micromechanical gyroscope with the same structural parameters;

[0050] Fig. 9 This is a sensing mode diagram of a multi-ring resonant micromechanical gyroscope with the same structural parameters;

[0051] in:

[0052] 1-support bottom layer, 2-oxidized insulating layer, 3-device structure layer, 31-316-working electrodes, 41-416-working electrodes, 51-53-island electrodes, 61-62-double folded beam spokes, 71-73-straight arm spokes, 8-anchoring platform, 91-99-first ring to ninth ring. DETAILED DESCRIPTION

[0053] The scheme proposed in the present invention is described in detail below with reference to the accompanying drawings and specific examples. However, it should be pointed out that the present invention not only protects the proposed embodiments, but any improvements made on this basis fall within the protection scope of the present invention.

[0054] like Figure 1-4, the present invention discloses a multi-ring resonant MEMS gyroscope with high processing tolerance, including a supporting bottom layer 1, an oxide insulating layer 2, and a device structure layer 3; the device structure layer includes an anchoring platform 8, a plurality of concentric ring structures 91-99, double folded beam spokes 61-62, and electrodes; the electrodes also include working electrodes 31-316, 41-416, and island electrodes 51-53.

[0055] The anchoring platform 8 is arranged on the top of the oxide insulating layer 2 and is concentric with the center of the supporting bottom layer 1. The anchoring platform is connected to a plurality of concentric circular rings 91-99 through inter-ring connecting beams. The plurality of concentric circular rings 91-99 are suspended relative to the supporting bottom layer to form a resonant structure.

[0056] The multiple concentric rings are divided into multiple groups, the first ring close to the anchoring platform is set as the first group 91, and the remaining rings outside the first ring are set to include two rings in each group, namely the second group of rings 92 and 93, the third group of rings 94 and 95, the fourth group of rings 96 and 97, and the fifth group of rings 98 and 99; the anchoring platform 8 is connected to the first group of rings 91 through double straight beams 71~72, and the two adjacent groups of rings are connected by double folded beam spokes 61~62. Except for the first group, the two rings in the remaining groups are connected by a straight arm beam 73.

[0057] The double-folded beam spokes 61-62 are composed of two independent beams, and the short connecting beams at both ends of each independent beam are respectively connected to the ring at one end thereof.

[0058] The electrodes include working electrodes and island electrodes. The working electrodes 31-316 and 41-416 are arranged between the fourth and fifth groups of circular rings, and the working electrodes 41-416 are arranged on the outer circumference of the circular ring 99; the island electrodes 51-53 are arranged on the inner side and outer sides of the double-folded beam spokes 61-62.

[0059] The present embodiment is further described below:

[0060] As the instruction manual Figure 2 As shown, the thickness of the device structure layer 3 can be set to 30-200um, the ratio of the diameter of the ninth ring 99 to the diameter of the anchoring platform 8 is set to 0.3-0.5, the first to ninth 91-99 concentric rings are set to have unequal widths, and the ring width can be set to 10um-30um. In this embodiment, the device layer thickness is set to 150um, the ratio of the diameter of the ninth ring to the anchoring platform is 0.4, the ring width is set to 15um and 25um, the first group of rings 91, the second group of rings 92 and 93, the third group of rings 94 and 95 are set to 15um, the fourth group of rings 96 and 97, and the fifth group of rings 98 and 99 are set to 25um.

[0061] like Figure 6 , Figure 7As shown, the multi-ring resonant MEMS gyroscope with high processing tolerance has a driving mode and a sensing mode stiffness axis with a reference coordinate angle of almost zero, which can greatly reduce the output orthogonal error. Figure 8 , Fig. 9 , the multi-ring resonant gyro driving mode and sensing mode stiffness axis with the same structural parameters have a large deviation angle θ from the reference coordinates ω This will output a large orthogonal error, which will seriously limit the improvement of the gyroscope performance. At the same time, the two working mode frequencies of the multi-ring resonant MEMS gyroscope with high processing tolerance designed by the present invention are 12889Hz and 12890Hz respectively, and the two working mode frequencies are split into 1Hz. Figure 8 , Fig. 9 The two working mode frequencies are 16054 Hz and 16083 Hz respectively, and the frequency splitting of the two working modes is 19 Hz. It can be seen that the multi-ring resonant MEMS gyroscope with high processing tolerance designed by the present invention significantly reduces the frequency splitting, which is beneficial to the improvement of the gyroscope performance.

[0062] Calculation of the spoke stiffness of the double folded beam of the multi-ring resonant MEMS gyroscope, where l, d, and t are the length, width, and thickness of the connecting beam between the rings, respectively, E is the elastic modulus of the material, K is the stiffness coefficient, F is the tensile force on the cantilever beam, and M is the bending moment on the cantilever beam:

[0063] According to the stiffness coefficient formula of ordinary cantilever beam under bending moment and stretching, we know

[0064]

[0065]

[0066] When a cantilever beam is subjected to bending moment, the stiffness coefficient is inversely proportional to the cube of the beam length. When a cantilever beam is subjected to tension, the stiffness coefficient is inversely proportional to the first power of the length.

[0067] In the present invention, the single folded beam spoke is composed of four beams. The stiffness coefficient of each beam of the single folded beam spoke under the action of bending moment and tension is: l1, l2, l3, l4 are the four beams constituting the single folded beam spoke respectively:

[0068] l1=l4,l2=l3

[0069]

[0070]

[0071]

[0072]

[0073] The stiffness coefficient of the single folding beam spoke designed by the present invention can be equivalent to the stiffness coefficient of the series spring, and k is the stiffness coefficient of the single beam constituting the single folding beam spoke:

[0074] k l1 =k l4 , k l2 =k l3

[0075]

[0076] The stiffness coefficients of the single folded beam spokes under the action of bending moment and tension are:

[0077]

[0078]

[0079] The stiffness coefficient of the double folded beam spoke under the action of bending moment and tension is twice the elastic coefficient of the single folded beam. The quotient of the stiffness coefficient of the double folded beam spoke under the action of bending moment and tension is:

[0080]

[0081] In this embodiment, l1=l4=23.5um, l2=l3=242um, d=12.5um, l2 is much larger than l1, l2 is much larger than d, so:

[0082]

[0083] Figure 8 , 9 In the structure with the same structural parameters, l5=320um, d=12.5um, the stiffness coefficient of the spoke under the action of bending moment and tension is calculated as follows:

[0084]

[0085] It can be concluded that the spokes of the comparative structure have a large difference in stiffness under the action of bending moment and tension, and it can be seen that the double-folded beam spokes of the present invention have good stiffness consistency under the action of bending moment and tension. In the double-folded beam spokes designed by the present invention, l2 is much larger than l1, and l2 is much larger than d. The change in stiffness of the double-folded beam spokes under the action of bending moment and tension mainly depends on the change in spoke length, and the change in spoke width has almost no effect on stiffness. Therefore, it can effectively reduce the influence of processing errors, reduce the deflection angle between the orthogonal main stiffness axis and the reference coordinate axis, and reduce the frequency decomposition of the two working modes, which is beneficial to the improvement of gyroscope performance.

[0086] Working principle:

[0087] like Figure 3As shown, the working electrodes 31-316, 41-416 are evenly distributed along the circumference and keep a certain distance from the ring. The side walls of the working electrodes and the side walls of the ring form a capacitor for driving, detecting, tuning and controlling. The electrodes between the rings are arranged in pairs as sixteen pairs along the circumference, and the outermost ring electrodes are arranged separately as sixteen along the circumference. A conductive layer is provided on the upper surface of all electrodes, and the conductive layer can be a metal such as gold, aluminum, or chromium.

[0088] The working electrodes are set to two working modes: the first is to use the inter-ring electrodes for driving and detection; a voltage is applied to the device structure, and two pairs of electrodes 33 and 34 respectively arranged in the positive and negative directions of the X-axis input driving signals, and the electrodes 33 and 34 generate electrostatic forces with the rings 97 and 98, and generate displacement responses in the Y-axis direction. The capacitance changes between the two pairs of electrodes 37 and 38 arranged in the positive and negative directions of the Y-axis and the rings 97 and 98 are analyzed to detect the frequency response of the driving mode and obtain the resonant frequency of the driving mode.

[0089] When the gyroscope senses angular velocity, the first to ninth rings 91-99 generate displacement responses in the direction of 45° with the X-axis. The capacitance changes generated by the four pairs of electrodes 35 and 36 or 31 and 32 arranged between the seventh ring 97 and the eighth ring 98 in the direction of 45° with the X-axis and the rings 97 and 98 are analyzed to obtain the magnitude of the angular velocity.

[0090] The electrodes arranged outside the ninth ring 99 are used for tuning control. When the perceived modal frequency is greater than the driven modal frequency, a voltage is applied to the electrodes 43, 411 or 47, 415 in the direction of the X-axis or at an angle of 45° to the X-axis, and the two working modal frequencies are adjusted by the electrostatic negative stiffness generated by the electrodes 43, 411 or 47, 415 and the ring 99 to achieve modal matching. Conversely, when the perceived modal frequency is less than the driven modal frequency, a voltage is applied to the electrodes 41, 49 in the Y-axis direction, and the two working modal frequencies are adjusted by the electrostatic negative stiffness generated by the electrodes 41, 49 and the ring 99 to achieve modal matching.

[0091] The second working mode is to apply voltage to the device structure, and two pairs of electrodes 33 and 37 respectively arranged in the positive and negative directions of the X and Y axes input driving signals; the remaining two pairs of electrodes 34 and 38 respectively arranged in the positive and negative directions of the X and Y axes sense the capacitance change between the ring 97 to detect the frequency response of the driving mode and obtain the resonant frequency of the driving mode.

[0092] When the carrier has an angular velocity input, multiple concentric rings generate displacement responses in the direction of 45° with the X-axis, and the capacitance changes of the four pairs of electrodes 35 and 36 or 31 and 32 respectively set between the seventh ring 97 and the eighth ring 98 in the direction of 45° with the X-axis and the rings 97 and 98 are analyzed to obtain the magnitude of the angular velocity. When the frequencies of the two working modes do not match, the mode matching control is performed through the tuning method in the first working mode.

Claims

1. A multi-ring resonant MEMS gyroscope with high processing fault tolerance, comprising a supporting bottom layer, an oxide insulating layer, and a device structure layer; The supporting bottom layer is located at the bottom and is used to set the oxidation insulation layer; The oxide insulating layer is arranged on the top of the supporting bottom layer, and the top of the oxide insulating layer is used to arrange the device structure layer; The device structure layer is arranged on top of the oxide insulating layer. Features: The device structure layer includes an anchoring platform, a plurality of concentric ring structures, connecting beams between the rings, and electrodes; The anchoring platform is circular and concentric with the supporting bottom layer, and an oxidized insulating layer is provided at the bottom of the anchoring platform; The multiple concentric ring structures are arranged on the anchoring platform through inter-ring connecting beams, no oxidized insulating layer is arranged at the bottom of the multiple concentric rings, and the multiple concentric rings are divided into multiple groups, the first ring close to the anchoring platform is arranged as one group, and the remaining rings far away from the first ring are arranged as each group including two rings; The inter-ring connecting beams include double folding beams and straight arm types; a plurality of straight arm connecting beams uniformly distributed in the circumferential direction are arranged between the anchoring platform and the first circular ring, and a plurality of double folding beam connecting beams uniformly distributed in the circumferential direction are arranged between the first circular ring and a group of concentric circular rings close to the first circular ring, and between the remaining groups of concentric circular rings; the radial directions of the corresponding double folding beam connecting beams correspond to each other, and are staggered from the radial directions of the straight arm connecting beams; the two concentric circular rings in each group of concentric circular rings are arranged as straight arm connecting beams; The electrodes also include working electrodes and island electrodes, and both types of electrodes have an oxidized insulating layer at the bottom; The working electrodes are arranged in a plurality and are evenly distributed between two groups of concentric rings, and sixteen pairs of electrodes are arranged between each two groups of concentric rings for inputting driving signals or outputting detection signals; The island electrodes are arranged on both sides of the outside of the double-folded beam spokes and inside the double-folded beam spokes. Eight double-folded beams are arranged between every two groups of concentric rings. Each double-folded beam spoke corresponds to a group of island electrodes. A group of island electrodes includes three island electrodes, which are used to isolate the working electrode from the double-folded beam spokes.

2. A multi-ring resonant MEMS gyroscope with high processing fault tolerance as claimed in claim 1, characterized in that: The multiple concentric rings are arranged to have unequal widths, and the width gradually increases or decreases from the ring close to the anchoring platform to the ring far away from the anchoring platform.

3. A multi-ring resonant MEMS gyroscope with high processing fault tolerance as claimed in claim 1, characterized in that: The width of one or more of the multiple concentric rings increases or decreases.

4. A multi-ring resonant MEMS gyroscope with high processing fault tolerance as claimed in claim 1, characterized in that: The double-folded beam spokes between the first circular ring and a group of concentric circular rings close to the first circular ring and between the remaining groups of concentric circular rings are composed of two independent beams; the straight-arm connecting beam between the anchoring platform and the first circular ring is composed of two independent beams; and the circular rings that form a group of two concentric circular rings are connected by a single straight-arm connecting beam.

5. A multi-ring resonant MEMS gyroscope with high processing fault tolerance as claimed in claim 1, characterized in that: The working electrode, the island electrode and the top of the anchoring platform are all provided with a conductive layer.

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