CN220795494U - Symmetrical MEMS gravity meter - Google Patents
Symmetrical MEMS gravity meter Download PDFInfo
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- CN220795494U CN220795494U CN202322296291.0U CN202322296291U CN220795494U CN 220795494 U CN220795494 U CN 220795494U CN 202322296291 U CN202322296291 U CN 202322296291U CN 220795494 U CN220795494 U CN 220795494U
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Abstract
The utility model discloses a symmetrical MEMS gravity meter, which comprises a central mass block, an outer frame, a group of positive rigidity buckling beams and a group of negative rigidity buckling beams. One end of the buckling beam is connected with the central mass block, the other end of the buckling beam is connected with the outer frame, the outer frame provides fixed support for the buckling beam, the central mass block is subjected to external acceleration to generate displacement relative to the outer frame, and the outer frame can limit the displacement range of the central mass block. The two groups of buckling beams adopt a positive and negative rigidity compensation principle, so that the symmetrical MEMS gravimeter has quasi-zero rigidity characteristics and extremely low resonant frequency. The symmetrical MEMS gravimeter has the advantages of small volume, low cost and the like.
Description
Technical Field
The utility model relates to the field of gravimeters, in particular to a symmetrical MEMS gravimeter.
Background
Since newtons found gravitational attraction, humans have been attracted to the mystery of gravitational attraction. Through long-term astronomical observation, scientists find that the motion of celestial bodies in the universe follows the law of universal gravitation. Then, the Kalvadeda performs an original torsion balance experiment, measures the value of the gravitational constant G, and is less than 1% different from the measurement result of a modern instrument. Micro-g-Solutions developed FG5-X absolute gravimeter based on JILA gravimeter, which was the most advanced and automated gravimeter in the world at that time. Brahim El Mansouri to the university of delf, et al developed a high resolution MEMS inertial sensor with integrated capacitance readings, the resonant frequency of which varied with tilt angle, at 34 ° to horizontal, the resonant frequency of which was observed to be 8.7Hz, and the noise power spectral density of which was found to be 17 ng/v Hz from the noise of the displacement detection circuit and the mechanical sensitivity of the MEMS sensor. Currently, CG-5 type auto-gravity meters, designed using the "Fused Silica" technology, are widely used as commercial gravity meters. It has a user-friendly operation, without resetting the reading, a resolution of 0.001 mGlul, a noise power spectral density of 2 μGal/VevHz@1Hz, and a range of 8000 mGlul. A suspension type MEMS gravity meter is designed by canal self-strengthening et al of Huazhong university of science and technology, and the noise power spectral density of the MEMS gravity meter is 2.4 ng/. V Hz@10Hz through an optical fiber displacement sensor. In addition, R.P. Middless et al, university of Grassgo, designed a three cantilever structure MEMS gravimeter, which had an asymmetric "geometrical anti-spring" design, such that the MEMS gravimeter had an extremely low resonant frequency, with a noise power spectral density of 40 μGal/+.v Hz@1Hz, and a drift of 111 μGal/day, as reported.
The study of gravimeters was matured at the end of the last century, as in FG5-X, CG-5, et al, by Micro-g&FG5-X gravimeter developed by LaCoste corporation reaches a precision of 15. Mu.Gal, but its total weight reaches150Kg, volume 1.5m 3 Because the traditional commercial gravimeter is large in size, high in cost and incapable of being popularized and the like, the difficulty of gravity detection and research cost are increased, and the traditional large-size gravimeter is miniaturized by combining the MEMS technology, so that the manufacturing cost of the gravimeter is reduced.
To make the MEMS gravity meter more sensitive to weak changes in gravitational acceleration, the formula is: Δa=Δx· (2pi.f 0 2 )
Wherein Δa is the change in acceleration, Δx is the displacement of the central mass, f 0 Is the resonant frequency of the MEMS gravimeter. When the MEMS gravimeter has extremely low resonant frequency, the weak gravity acceleration change can lead to the center mass to have larger displacement, and the design scheme is beneficial to subsequent displacement detection. According to the formula:
where k is the rigidity of the MEMS gravimeter and m is the mass of the MEMS gravimeter, the conventional commercial gravimeter can achieve the purpose of lowering the resonant frequency by increasing the mass of the sensor, but the MEMS technology is characterized by miniaturizing the gravimeter, so the volume and mass of the MEMS gravimeter are much smaller than those of commercial superconducting gravimeter GWR-iGrv, atomic interference gravimeter Micro-g FG-515, etc. How to design a material with extremely low stiffness and resonance frequency is a problem that is under development at this stage.
Disclosure of Invention
The utility model aims to provide a symmetrical MEMS gravity meter, which has the advantages of reduced volume, mass and manufacturing cost.
The technical aim of the utility model is realized by the following technical scheme:
a symmetrical MEMS gravimeter comprises a central mass block, an outer frame and two groups of buckling beams, wherein the two groups of buckling beams are respectively a group of positive rigidity buckling beams and a group of negative rigidity buckling beams,
the outer frame provides fixed support for the buckling beams, an outer frame limiting space is arranged on the inner side of the outer frame, and the outer frame limiting space is used for limiting the displacement range of the center mass block;
the central mass block is positioned in the limited space of the outer frame, and generates displacement relative to the outer frame under the action of external force;
the two groups of bent beams are respectively provided with an outer frame, one end of each outer frame is connected with the central mass block, and the other end of each outer frame is connected with the outer frame to provide fixed support.
Preferably, the positive stiffness buckling beam and the negative stiffness buckling beam are subjected to stiffness compensation in a parallel connection mode.
Preferably, the positive stiffness buckling beam comprises a first positive stiffness buckling beam and a second positive stiffness buckling beam, the negative stiffness buckling beam comprises a first negative stiffness buckling beam and a second negative stiffness buckling beam, the first positive stiffness buckling beam and the second positive stiffness buckling beam are bilaterally symmetrical about the central mass block, and the first negative stiffness buckling beam and the second negative stiffness buckling beam are also bilaterally symmetrical about the central mass block.
Preferably, the center mass block is provided with four center supporting structures, the four center supporting structures are a first center supporting structure, a second center supporting structure, a third center supporting structure and a fourth center supporting structure, the first center supporting structure and the second center supporting structure are bilaterally symmetrical about the center mass block, and the third center supporting structure and the fourth center supporting structure are bilaterally symmetrical about the center mass block;
four frame supporting structures are arranged on the inner side face of the outer frame, and the four frame supporting structures are a first frame supporting structure, a second frame supporting structure, a third frame supporting structure and a fourth frame supporting structure;
two ends of the first positive rigidity bending beam are respectively connected with the first central supporting structure and the first frame supporting structure; two ends of the second positive stiffness bending beam are respectively connected with the second central supporting structure and the second frame supporting structure; the two ends of the first negative stiffness bending beam are respectively connected with the center supporting structure III and the frame supporting structure III, and the two ends of the second negative stiffness bending beam are respectively connected with the center supporting structure IV and the frame supporting structure IV.
Preferably, when the center mass block generates displacement relative to the outer frame under the action of gravity, so that the group of negative rigidity buckling beams have negative rigidity characteristics, the group of positive rigidity buckling beams still have positive rigidity, and rigidity compensation is performed on the positive rigidity buckling beams and the negative rigidity buckling beams in a parallel connection mode, so that the symmetrical MEMS gravity instrument has quasi-zero rigidity characteristics, and the resonant frequency of the symmetrical MEMS gravity instrument is effectively reduced.
The beneficial effects of the utility model are as follows:
(1) Under the action of gravity, the resonance frequency of the symmetrical MEMS gravimeter can reach 10Hz or lower, which means that the MEMS gravimeter is extremely sensitive to weak acceleration change;
(2) The design of the buckling beam ensures that the symmetrical MEMS gravimeter cannot lose the quasi-zero stiffness characteristic due to the change of the beam width caused by the processing error of the MEMS process, and reduces the influence caused by the processing;
(3) The microstructure size of the symmetrical MEMS gravimeter can be controlled within the size of 20mm multiplied by 0.2mm, so that the symmetrical MEMS gravimeter has smaller volume and mass compared with the traditional gravimeter;
(4) The symmetrical MEMS gravimeter can be produced in large quantities due to the mass production capacity of MEMS technology, and the production cost of the MEMS gravimeter is effectively reduced.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a symmetrical MEMS gravimeter according to an embodiment of the present utility model;
FIG. 2 is a partial view of the top of the center mass provided by an embodiment of the present utility model;
FIG. 3 is a force versus displacement curve of a symmetrical MEMS gravimeter according to an embodiment of the present utility model;
FIG. 4 is a plot of resonant frequency versus angle between MEMS gravimeter and horizontal plane for a symmetrical MEMS gravimeter provided by an embodiment of the utility model;
fig. 5a, 5b and 5c are force-displacement curves of a symmetrical MEMS gravity meter based on different width buckling beams according to an embodiment of the present utility model.
In all the drawings, "d" represents the depth direction, "w" represents the width direction, "l" represents the longitudinal direction, i.e., the horizontal direction.
Reference numerals: 1. a central mass block; 2. an outer frame; 3. a curved beam; 3a, positive stiffness buckling beams; 3a-1, a first positive stiffness buckling beam; 3a-2, a second positive stiffness buckling beam; 3b, negative stiffness buckling beams; 3b-1, a first negative stiffness buckling beam; 3b-2, a second negative stiffness buckling beam; 4. a central support structure; 4a, a first central support structure; 4b, a center support structure II; 4c, a center support structure III; 4d, a center support structure IV; 5. a frame support structure; 5a, a first frame supporting structure; 5b, a frame support structure II; 5c, a frame supporting structure III; 5d, a frame supporting structure IV; 6. the outer frame defines a space.
Detailed Description
In order to make the objects, technical solutions and advantages of the present utility model more apparent, the present utility model will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model. In addition, the technical features of the embodiments of the present utility model described below may be combined with each other as long as they do not collide with each other.
As shown in fig. 1, in an embodiment of the present utility model, a symmetrical MEMS gravity meter is disclosed; the method comprises the following steps: a central mass 1, an outer rim 2, a set of positive stiffness buckling beams 3a and a set of negative stiffness buckling beams 3b. One end of the buckling beam 3 is connected with the central mass block 1, the other end of the buckling beam is connected with the outer frame 2 which can provide fixed support, the central mass block 1 is bilaterally symmetrical relative to the central mass block 1, the central mass block 1 is positioned in a limited space 6 of the outer frame 2, displacement relative to the outer frame 2 is generated under the action of external acceleration, the outer frame 2 provides fixed support for the buckling beam 3, and the displacement range of the central mass block 1 is limited.
As shown in fig. 1 and 2, in the implementation of the present utility model, a symmetrical MEMS gravity meter is disclosed, wherein four center support structures 4 are provided at two ends of a center mass 1, and the four center support structures 4 are a first center support structure 4a, a second center support structure 4b, and a center support structure junction, respectivelyThe structure three 4c and the center support structure four 4d are arranged on the inner side of the outer frame 2, four frame support structures 5 are respectively a frame support structure one 5a, a frame support structure two 5b, a frame support structure three 5c and a frame support structure four 5d, the positive rigidity buckling beam 3a is bilaterally symmetrical relative to the center mass block 1, the negative rigidity buckling beam 3b is bilaterally symmetrical relative to the center mass block 1, two ends of the positive rigidity buckling beam 3a-1 are connected with the support structures 4a and 5a, two ends of the positive rigidity buckling beam 3a-2 are connected with the support structures 4b and 5b, two ends of the negative rigidity buckling beam 3b-1 are connected with the support structures 4c and 5c, and two ends of the negative rigidity buckling beam 3b-2 are connected with the support structures 4d and 5 d. Fig. 2 shows more clearly the relative dimensions of the central mass 1 and the positive stiffness flexure beams 3a in an embodiment. The "depth direction" is denoted by "d", the "width direction" is denoted by "w", and the "length direction" is denoted by "l". The width of the positive stiffness buckling beam 3a in fig. 1 and 2 is denoted by "w flex "means that the thickness is defined by" d flex "means that the width of the central mass 1 is defined by" w mass "means that the thickness is defined by" d mass "means that the length is defined by" l mass "means.
As shown in fig. 3, an embodiment of the present utility model provides a force-displacement relationship for a symmetrical MEMS gravity meter; the dashed line in the figure shows the force-displacement curve of the negative stiffness buckling beam 3b, the dashed line in the figure shows the force-displacement curve of the positive stiffness buckling beam 3a, and the solid line in the figure shows the force-displacement curve of the symmetrical MEMS gravimeter. In the force-displacement relation curve, the positive stiffness bending beam 3a and the negative stiffness bending beam 3b of the section I are respectively represented as positive stiffness, the positive stiffness bending beam 3a of the section II is respectively represented as positive stiffness, the negative stiffness bending beam 3b is respectively represented as negative stiffness, the symmetrical MEMS gravimeter is enabled to have extremely low stiffness and the stiffness is fixed value by performing stiffness compensation on the positive stiffness bending beam 3a and the negative stiffness bending beam 3b, and the stiffness and resonance frequency of the symmetrical MEMS gravimeter can be effectively reduced by adopting the design scheme, and the positive stiffness bending beam 3a and the negative stiffness bending beam 3b of the section III are respectively represented as positive stiffness.
As shown in FIG. 4, the embodiment of the utility model provides a curve of the resonance frequency of the symmetrical MEMS gravity meter, namely the included angle between the MEMS gravity meter and the horizontal plane, wherein the resonance frequency of the symmetrical MEMS gravity meter is reduced along with the increase of the included angle when the included angle between the symmetrical MEMS gravity meter and the horizontal plane is 0-90 degrees, the resonance frequency of the symmetrical MEMS gravity meter is increased along with the increase of the included angle when the included angle between the symmetrical MEMS gravity meter and the horizontal plane is 90-92 degrees, the resonance frequency of the symmetrical MEMS gravity meter is not more than 10Hz when the included angle between the symmetrical MEMS gravity meter and the horizontal plane is 88-92 degrees, the resonance frequency of the symmetrical MEMS gravity meter is 8.9Hz when the included angle between the symmetrical MEMS gravity meter and the horizontal plane is 90 degrees, and the mass of the central mass block 1 is not more than 80mg.
As shown in fig. 5, embodiments of the present utility model provide force-displacement curves for symmetrical MEMS gravimeters with different width buckling beams, and Deep Reactive Ion Etching (DRIE) techniques will be applied to the width "w" of buckling beam 3 flex 5 a-5 c show force-displacement curves of symmetrical MEMS gravimeter with the width of the bending beam 3 being 18 μm, 16 μm and 12 μm respectively, the symmetrical MEMS gravimeter with three different beam widths still has quasi-zero stiffness characteristic, but the bending load is reduced along with the reduction of the beam width, which means that the symmetrical MEMS gravimeter is fixed at a proper angle, namely, the MEMS gravimeter can have quasi-zero stiffness characteristic and extremely low resonance frequency when the gravity component in the sensitive axis direction is equal to the bending load, the resonance frequency of the symmetrical MEMS gravimeter is 6.87Hz when the width of the bending beam 3 is 18 μm, the resonance frequency of the symmetrical MEMS gravimeter is 8.44Hz when the width of the bending beam 3 is 16 μm, and the resonance frequency of the symmetrical MEMS gravimeter is 5.16Hz when the width of the bending beam 3 is 12 μm.
It will be readily understood by those skilled in the art that the foregoing description is merely illustrative of the preferred embodiments of the utility model and that no limitations are intended to the scope of the utility model, except insofar as modifications, equivalents, and improvements may be made within the spirit and principles of the utility model.
Claims (4)
1. A symmetrical MEMS gravimeter comprises a central mass block, an outer frame and two groups of buckling beams, wherein the two groups of buckling beams are respectively a group of positive rigidity buckling beams and a group of negative rigidity buckling beams,
the outer frame provides fixed support for the buckling beams, an outer frame limiting space is arranged on the inner side of the outer frame, and the outer frame limiting space is used for limiting the displacement range of the center mass block;
the central mass block is positioned in the limited space of the outer frame, and generates displacement relative to the outer frame under the action of external force;
the two groups of bent beams are respectively provided with an outer frame, one end of each outer frame is connected with the central mass block, and the other end of each outer frame is connected with the outer frame to provide fixed support.
2. The symmetrical MEMS gravity gauge of claim 1, wherein the positive stiffness buckling beam and the negative stiffness buckling beam are stiffness compensated in parallel.
3. The symmetrical MEMS gravity gauge of claim 1, wherein the positive stiffness buckling beam comprises a first positive stiffness buckling beam and a second positive stiffness buckling beam, the negative stiffness buckling beam comprises a first negative stiffness buckling beam and a second negative stiffness buckling beam, the first positive stiffness buckling beam and the second positive stiffness buckling beam are laterally symmetrical about the central mass, and the first negative stiffness buckling beam and the second negative stiffness buckling beam are also laterally symmetrical about the central mass.
4. The symmetrical MEMS gravity meter of claim 1, wherein the central mass is provided with four central support structures, the four central support structures being a first central support structure, a second central support structure, a third central support structure and a fourth central support structure, the first central support structure and the second central support structure being bilaterally symmetrical about the central mass, the third central support structure and the fourth central support structure being bilaterally symmetrical about the central mass;
four frame supporting structures are arranged on the inner side face of the outer frame, and the four frame supporting structures are a first frame supporting structure, a second frame supporting structure, a third frame supporting structure and a fourth frame supporting structure;
two ends of the first positive rigidity bending beam are respectively connected with the first central supporting structure and the first frame supporting structure; two ends of the second positive stiffness bending beam are respectively connected with the second central supporting structure and the second frame supporting structure; the two ends of the first negative stiffness bending beam are respectively connected with the center supporting structure III and the frame supporting structure III, and the two ends of the second negative stiffness bending beam are respectively connected with the center supporting structure IV and the frame supporting structure IV.
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| CN202322296291.0U CN220795494U (en) | 2023-08-25 | 2023-08-25 | Symmetrical MEMS gravity meter |
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| CN202322296291.0U CN220795494U (en) | 2023-08-25 | 2023-08-25 | Symmetrical MEMS gravity meter |
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