CN113968570A

CN113968570A - Two-degree-of-freedom resonant MEMS sensor based on active coupling and application

Info

Publication number: CN113968570A
Application number: CN202010734433.5A
Authority: CN
Inventors: 赵纯
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2022-01-25

Abstract

The invention discloses a two-degree-of-freedom resonant MEMS sensor based on active coupling and application thereof, belonging to the fields of MEMS and sensing and control thereof in the field of information engineering. The MEMS resonant device comprises a first resonator and a second resonator; the active coupling module mutually and actively couples the first resonator and the second resonator, so that the frequency of the first resonator and the frequency of the second resonator are quickly converged in a specific interval, and in the interval with the quickly converged frequencies, the frequency change of the first resonator and the second resonator caused by the change to be measured is far higher than that of a traditional resonant sensing mode without an active coupling structure. The invention can solve the problem of lower sensitivity and resolution of the resonant acceleration sensor in the prior art.

Description

Two-degree-of-freedom resonant MEMS sensor based on active coupling and application

Technical Field

The invention belongs to the fields of micro electro mechanical systems and sensing and control thereof in the field of information engineering, and particularly relates to a two-degree-of-freedom resonant MEMS sensor based on active coupling and application thereof.

Background

The MEMS sensor has the advantages of small size, low cost and the like, and is applied to the commercial fields of consumer electronics, automotive electronics and the like and the high-end fields of oil exploration, gravity investigation and the like. Compared with the MEMS sensor using voltage output, including capacitance readout, light intensity readout, etc., the MEMS resonant sensor uses frequency output, which has the advantages of high stability and high resolution, and thus is the development direction and trend of high-performance MEMS sensors. To achieve high stability and high resolution, it is necessary to improve the sensitivity of the MEMS resonant sensor.

At present, the sensitivity of the MEMS resonant sensor is improved mainly in a powerful mode, a displacement mode, a strain amplification mode and the like. Methods for magnifying force and displacement are common, for example, the patent MEMS resistive interferometer with magnified electrical characteristics (US9354246B2), which states that the magnification is limited by the size of the lever. For smaller sizes in MEMS sensors, the amplification of the lever is typically limited. Strain amplification methods, such as Kose, et al, journal of Micromechanics and microermination, 26(4),045012,2016, etc., are limited by the process of device fabrication. These limiting factors all reduce the efficiency of sensitivity enhancement, and therefore, a new way for enhancing sensitivity needs to be explored to realize a high-performance MEMS resonant sensor.

In recent years, dynamic systems described by non-hermitian matrix Hamiltonian quantities have become hot research in condensed physical, acoustic, and optical fields, mainly including parity-time symmetry (odd-even-time symmetric) systems and anti-parity-time symmetry (anti-odd-time symmetric) systems. Among them, the pace of well-blow studies following the parity-time symmetric system (R ü ter, et al. nature Physics,6(3), 192-. However, up to now, an anti-parity-time symmetric system has not been implemented in microelectromechanical systems.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides an active coupling-based two-degree-of-freedom resonant MEMS sensor and application thereof, so that the technical problems of poor stability and low resolution of the MEMS sensor caused by low sensitivity in the prior art are solved.

To achieve the above object, according to one aspect of the present invention, there is provided a two-degree-of-freedom resonant MEMS sensor based on active coupling, comprising an active coupling module, a sensing module and a MEMS resonant device;

the MEMS resonant device comprises a first resonator and a second resonator, and the first resonator and the second resonator are connected through the active coupling module to form a closed loop so as to realize active coupling;

the first resonator and the second resonator after being coupled with each other have an anti-odd-even-time symmetry phenomenon, so that the first resonator and the second resonator have sensitivity to a to-be-measured value;

the sensing module is connected with the first resonator or the second resonator and used for sensing the frequency change of the first resonator and the second resonator which are to be measured and are coupled with each other, so as to obtain frequency signal data used for calculating the frequency to be measured.

Preferably, the active coupling module comprises a first active coupling circuit and a second active coupling circuit; the input end of the first active coupling circuit is connected with the output end of the first resonator, and the output end of the first active coupling circuit is connected with the input end of the second resonator; the input end of the second active coupling circuit is connected with the output end of the second resonator, and the output end of the second active coupling circuit is connected with the input end of the first resonator.

Preferably, the first active coupling circuit comprises a first amplifying circuit and a first adjusting circuit, an input end of the first amplifying circuit is connected with an output end of the first resonator, and an output end of the first amplifying circuit is connected with an input end of the first adjusting circuit;

the first amplifying circuit is used for converting the dynamic current generated by the first resonator into a first voltage and applying the first voltage to the second resonator; the first adjusting circuit is used for adjusting the amplitude of the first voltage generated by the first amplifying circuit and the phase between the first voltage and the driving voltage.

Preferably, the first resonator includes a first adjustment electrode, a second adjustment electrode, a first drive electrode, and a first detection electrode;

the input end of the first driving electrode is connected with the output end of a driving power supply, and the first driving electrode is used for driving the first resonator to oscillate so as to generate the natural frequency of the first resonator;

the output end of the first detection electrode is connected with the input end of the first amplifying circuit, and the first detection electrode is used for converting the vibration of the first resonator into dynamic current to be input to the first amplifying circuit;

the first adjusting electrode and the second adjusting electrode are symmetrically arranged and are used for adjusting initial misalignment caused by process errors.

Preferably, the first amplifying circuit is a charge amplifying circuit or a current amplifying circuit.

Preferably, the second active coupling circuit includes a second amplifying circuit and a second adjusting circuit, an input terminal of the second amplifying circuit is connected to an output terminal of the second resonator, an output terminal of the second amplifying circuit is connected to an input terminal of the second adjusting circuit, and an output terminal of the second adjusting circuit is connected to an input terminal of the first resonator;

the second amplifying circuit is used for converting the dynamic current generated by the second resonator into a second voltage and applying the second voltage to the first resonator; the second regulating circuit is used for regulating the amplitude of the second voltage generated by the second amplifying circuit and the phase between the second voltage and the driving voltage.

Preferably, the second resonator includes a third adjustment electrode, a fourth adjustment electrode, a second drive electrode, and a second detection electrode;

the input end of the second driving electrode is connected with the output end of a driving power supply, and the second driving electrode is used for driving the second resonator to oscillate so as to generate the natural frequency of the second resonator;

the output end of the second detection electrode is connected to the input end of the second amplifying circuit, and the second detection electrode is used for converting the vibration of the second resonator into dynamic current which is input to the second amplifying circuit;

the third adjusting electrode and the fourth adjusting electrode are symmetrically arranged and are used for adjusting initial misalignment caused by process errors.

Preferably, the second amplifying circuit is a charge amplifying circuit or a current amplifying circuit.

Preferably, the detection module comprises a force amplification device, a cantilever beam and a mass; the cantilever beams are symmetrically arranged on two sides of the mass block, and the mass block is connected with the first resonator through the force amplifying device.

According to another aspect of the present invention, there is provided an application of the two-degree-of-freedom resonant MEMS sensor based on active coupling as described above in measuring temperature, magnetic field strength, pressure, stress strain.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

1. according to the invention, two independent resonators are mutually coupled by adopting active coupling, an anti-odd-even-time symmetry phenomenon is introduced, the resonance frequency difference between the two resonators is to be measured, the energy difference between the two resonators is essentially changed, further the system is close to a special point at a symmetrical-asymmetrical phase change interface, the two resonators mutually coupled are rapidly converged near the special point, so that the sensitivity of the resonance frequency of the two resonators to the change to be measured is greatly improved, and the extremely high sensitivity can be realized in the interval;

2. the invention can change the resonance device which is not sensitive to the measured quantity into the resonance device which is sensitive to the measured quantity by introducing the active coupling module;

3. in the working range, the frequency change of the two resonators in the MEMS resonant device is opposite to the direction of the change to be measured, so that frequency differential detection can be realized, the sensitivity is further improved, and the common mode rejection is improved;

4. the sensitivity of the sensor is further adjusted by adjusting the gain in the adjusting circuit and the frequency difference between the first resonator and the second resonator;

5. the invention can be applied to various sensors such as temperature sensors, magnetic field sensors, pressure sensors and the like, and has wide application range.

Drawings

FIG. 1 is a schematic structural diagram of an active coupling-based two-degree-of-freedom resonant MEMS sensor of the present invention;

FIG. 2 is a schematic diagram of the anti-odd-even-time symmetry phenomenon in the two-degree-of-freedom resonant MEMS sensor based on active coupling according to the present invention;

FIG. 3 is a graphical representation of the sensitivity of the first resonator and the second resonator to changes in input acceleration without introducing active coupling in one embodiment of the present invention;

fig. 4 is a graph illustrating the sensitivity of the resonant frequency of the first resonator and the second resonator to changes in input acceleration with active coupling introduced in one embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Fig. 1 is a schematic structural diagram of a two-degree-of-freedom resonant MEMS sensor based on active coupling according to the present invention, as shown in fig. 1, including: the MEMS sensing device comprises a MEMS resonant device, a sensing module and an active coupling module, wherein the MEMS resonant device comprises a first resonator 1 and a second resonator 4; the active coupling module comprises a first active coupling circuit and a second active coupling circuit, the first active coupling circuit and the second active coupling circuit are identical in structure, the first active coupling circuit comprises a first amplifying circuit 2 and a first adjusting circuit 3, the second active coupling circuit comprises a second amplifying circuit 9 and a second adjusting circuit 10, and the sensing module comprises a force amplifying device 15, a cantilever beam 16 and a mass block 17.

To explain further, the first resonator 1 includes a first adjustment electrode 11, a second adjustment electrode 12, a first driving electrode 13 and a first detection electrode 14, the first adjustment electrode 11 and the second adjustment electrode 12 are symmetrically disposed, and the first driving electrode 13 and the first detection electrode 14 are symmetrically disposed; the second resonator 4 comprises a third adjusting electrode 5, a fourth adjusting electrode 6, a second driving electrode 7 and a second detecting electrode 8, the third adjusting electrode 5 and the fourth adjusting electrode 6 are symmetrically arranged, and the second driving electrode 7 and the second detecting electrode 8 are symmetrically arranged.

To explain further, the output end of the first detection electrode 14 is connected to the input end of the first amplifying circuit 2, the output end of the first amplifying circuit 2 is connected to the input end of the first adjusting circuit 3, the output end of the first adjusting circuit 3 is connected to the input end of the second driving electrode, the output end of the second detection electrode 8 is connected to the input end of the second amplifying circuit 9, the output end of the second amplifying circuit 9 is connected to the input end of the second adjusting circuit 10, and the output end of the second adjusting circuit 10 is connected to the input end of the first driving electrode 13.

To be further described, the display device further includes a driving power supply, the driving power supply is configured to output a driving voltage signal, and an output end of the driving power supply is respectively connected to the input end of the first driving electrode 13 and the input end of the second driving electrode 7.

To explain further, the mass 17 is connected to the force amplification device 15, and the cantilever beam 16 is disposed on both sides of the force amplification device 15.

Optionally, the first amplifying circuit 2 is a charge amplifying circuit or a current amplifying circuit.

Optionally, the second amplifying circuit 9 is a charge amplifying circuit or a current amplifying circuit.

It should be noted that, compared with the prior art, the two-degree-of-freedom resonant MEMS sensor based on active coupling provided by the present invention introduces an anti-odd-time symmetry phenomenon, which is used to make the first resonator 1 and the second resonator 4 sensitive to a measurement.

Specifically, the first active coupling circuit and the second active coupling circuit connect the first resonator 1 and the second resonator 4 to form a closed loop, and the first resonator 1 and the second resonator 4 are both sensitive to a measurement value by actively coupling the first resonator 1 and the second resonator 4.

Specifically, as shown in fig. 2(a), in the case of no active coupling, the variation curve of the resonant frequency of the first resonator with δ (i.e. the variation caused by measurement) indicates that the first resonator is sensitive to the measurement; as shown in fig. 2(b), the variation of the frequency of the second resonator with δ (i.e. the variation caused by the quantity to be measured) without introducing active coupling indicates that the second resonator is insensitive to the quantity to be measured, and fig. 2(a) and 2(b) indicate that no anti-parity-time symmetry phenomenon occurs without introducing active coupling. Fig. 2(c) and 2(d) show the variation of the resonant frequency of the first resonator and the second resonator with δ (i.e. the variation caused by the quantity to be measured) after the introduction of active coupling, respectively, and it can be seen that the anti-parity-symmetry phenomenon occurs after the introduction of active coupling, wherein two resonant frequencies, Mode1 and Mode2 identified in fig. 2(d), occur in the first resonator and the second resonator, wherein the resonant frequencies of Mode1 and Mode2 are both sensitive to the quantity to be measured; meanwhile, an absolute point is marked in fig. 2(d), and near this point, the resonance frequencies of Mode1 and Mode2 are rapidly close and eventually meet at the absolute point. In this interval, the sensitivity of the resonant frequencies of Mode1 and Mode2 to δ (i.e., the change caused by the measurement to be measured) is greatly improved, that is, the sensitivity of the first resonator and the second resonator to the measurement to be measured is high, so that the sensitivity of the sensor is improved, and the detection precision is improved. It should be noted that, as shown in fig. 2(d), at an explicit point, the sensitivity of the first resonator and the second resonator to be measured is the highest, and the sensor detects the measurement to be measured most accurately. The present invention improves the sensitivity of the sensor by exactly taking advantage of the anti-parity-symmetry phenomenon and by exploiting the properties in this convergence interval. The lean response characteristics of the first resonator in different intervals are shown in fig. 2(e), fig. 2(f) and fig. 2(g), respectively.

In a more specific embodiment, the two-degree-of-freedom resonant MEMS sensor based on active coupling is applied to an acceleration sensor. As shown in fig. 3(a), 3(b) and 3(c), fig. 3(a) shows the sensitivity curve of the resonance frequency of the independent first resonator to the change of the input acceleration without introducing the active coupling, fig. 3(b) shows the sensitivity curve of the resonance frequency of the independent second resonator to the change of the input acceleration without introducing the active coupling, and as can be seen from fig. 3(c), the resonance frequency of the first resonator is sensitive to the change of the external acceleration with the sensitivity of 2800Hz/g, and the output frequency of the second resonator is hardly affected by the external acceleration with the sensitivity of 0 Hz/g.

Specifically, an active coupling module as shown in fig. 1 is introduced, that is, the first amplifying circuit 2 and the first adjusting circuit 3 constitute the first active coupling circuit, the second amplifying circuit 9 and the second adjusting circuit 10 constitute the second active coupling circuit, phase and gain adjustment is performed through the first adjusting circuit 3 and the second adjusting circuit 10, and appropriate parameter values, that is, appropriate parameter values are selected

(i.e. the phase of the first adjusting circuit) ≈ 90 ° (or ≈ -90 °),

g1 ≈ G2, the specific value may be adjusted according to the sensitivity requirement, for example, 10 times the gain value calculated from the initial frequency difference of the first resonator and the second resonator.

Specifically, after the active coupling module is introduced, the resonant frequency of the first resonator and the resonant frequency of the second resonator change along with the external acceleration, and the curve is shown in fig. 4, wherein the sensitivity of the first resonator is improved from 2800Hz/g to 52500Hz/g, and the sensitivity of the second resonator is changed from 0Hz/g to-50500 Hz/g.

To explain further, the two-degree-of-freedom resonant MEMS sensor based on active coupling as shown in fig. 1 can also be applied to implement a high-sensitivity resonant temperature sensor, a magnetic field sensor, a pressure sensor, a stress strain sensor, and the like.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A two-degree-of-freedom resonant MEMS sensor based on active coupling is characterized by comprising an active coupling module, a sensing module and an MEMS resonant device;

the MEMS resonant device comprises a first resonator (1) and a second resonator (4), wherein the first resonator (1) and the second resonator (4) are connected through the active coupling module to form a closed loop circuit, so that active coupling is realized;

the first resonator (1) and the second resonator (4) which are coupled with each other have an anti-parity-time symmetry phenomenon, so that the first resonator (1) and the second resonator (4) have sensitivity to a to-be-measured value;

the sensing module is connected with the first resonator (1) or the second resonator (4) and used for sensing the frequency change of the first resonator and the second resonator which are to be measured and are coupled with each other to obtain frequency signal data used for calculating the frequency to be measured.

2. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1, wherein: the active coupling module comprises a first active coupling circuit and a second active coupling circuit; the input end of the first active coupling circuit is connected with the output end of the first resonator (1), and the output end of the first active coupling circuit is connected with the input end of the second resonator (4); the input end of the second active coupling circuit is connected with the output end of the second resonator (4), and the output end of the second active coupling circuit is connected with the input end of the first resonator (1).

3. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1 or 2, wherein: the first active coupling circuit comprises a first amplifying circuit (2) and a first regulating circuit (3), wherein the input end of the first amplifying circuit (2) is connected with the output end of the first resonator (1), and the output end of the first amplifying circuit (2) is connected with the input end of the first regulating circuit (3);

the first amplifying circuit (2) is used for converting the dynamic current generated by the first resonator (1) into a first voltage and applying the first voltage to the second resonator (4); the first adjusting circuit (3) is used for adjusting the amplitude of the first voltage generated by the first amplifying circuit (2) and the phase between the first voltage and the driving voltage.

4. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 3, wherein: the first resonator (1) comprises a first adjustment electrode (11), a second adjustment electrode (12), a first drive electrode (13) and a first detection electrode (14);

the input end of the first driving electrode (13) is connected with the output end of a driving power supply, and the first driving electrode (13) is used for driving the first resonator (1) to oscillate so as to generate the natural frequency of the first resonator;

the output end of the first detection electrode (14) is connected with the input end of the first amplifying circuit (2), and the first detection electrode (14) is used for converting the vibration of the first resonator (1) into a dynamic current to be input into the first amplifying circuit (2);

the first adjusting electrode (11) and the second adjusting electrode (12) are symmetrically arranged and are used for adjusting initial deviation caused by process errors.

5. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 3, wherein: the first amplifying circuit (2) is a charge amplifying circuit or a current amplifying circuit.

6. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1 or 2, wherein: the second active coupling circuit comprises a second amplifying circuit (9) and a second regulating circuit (10), wherein the input end of the second amplifying circuit (9) is connected with the output end of the second resonator (4), the output end of the second amplifying circuit (9) is connected with the input end of the second regulating circuit (10), and the output end of the second regulating circuit (10) is connected with the input end of the first resonator (1);

the second amplifying circuit (9) is used for converting the dynamic current generated by the second resonator (4) into a second voltage and applying the second voltage to the first resonator (1); the second adjusting circuit (10) is used for adjusting the amplitude of the second voltage generated by the second amplifying circuit (9) and the phase between the second voltage and the driving voltage.

7. The two-degree-of-freedom resonant MEMS sensor based on active coupling as claimed in claim 6, wherein: the second resonator (4) comprises a third adjusting electrode (5), a fourth adjusting electrode (6), a second driving electrode (7) and a second detecting electrode (8);

the input end of the second driving electrode (7) is connected with the output end of a driving power supply, and the second driving electrode (7) is used for driving the second resonator (4) to oscillate so as to generate the natural frequency of the second resonator;

the output end of the second detection electrode (8) is connected to the input end of the second amplifying circuit (9), and the second detection electrode (8) is used for converting the vibration of the second resonator (4) into a dynamic current which is input to the second amplifying circuit (9);

the third adjusting electrode (5) and the fourth adjusting electrode (6) are symmetrically arranged and are used for adjusting initial deviation caused by process errors.

8. The two-degree-of-freedom resonant MEMS sensor based on active coupling as claimed in claim 6, wherein: the second amplifying circuit (9) is a charge amplifying circuit or a current amplifying circuit.

9. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1, wherein: the detection module comprises a force amplification device (15), a cantilever beam (16) and a mass block (17); the cantilever beams (16) are symmetrically arranged on two sides of the mass block (17), and the mass block (17) is connected with the first resonator (1) through the force amplifying device (15).

10. Use of the two-degree-of-freedom resonant MEMS sensor based on active coupling according to any of claims 1 to 9 for measuring temperature, magnetic field strength, pressure, stress strain.