A two-degree-of-freedom resonant MEMS sensor based on active coupling and its application

Abstract

The present invention discloses a two-degree-of-freedom resonant MEMS sensor based on active coupling and its application, which belongs to the field of micro-electromechanical systems and their sensing and control in the field of information engineering. It includes an active coupling module, a sensing module and a MEMS resonant device, and the MEMS resonant device includes a first resonator and a second resonator; the active coupling module actively couples the first resonator and the second resonator to each other, so that the frequency of the first resonator and the frequency of the second resonator converge rapidly within a specific interval, and within the interval of rapid frequency convergence, the frequency change of the first resonator and the second resonator caused by the change to be measured is much higher than the traditional resonant sensing method without active coupling structure, and the change to be measured can be measured by detecting the frequency change of the first resonator and the second resonator, and the difference between the frequency changes of the first resonator and the second resonator. The present invention can solve the problem of low sensitivity and resolution of resonant acceleration sensors in the prior art.

Description

Technical Field

[0001] The present invention belongs to the field of micro-electromechanical systems and sensing and control thereof in the field of information engineering, and more specifically, relates to a two-degree-of-freedom resonant MEMS sensor based on active coupling and its application. Background Art

[0002] MEMS sensors have advantages such as small size and low cost. They are used in commercial fields such as consumer electronics and automotive electronics, as well as high-end fields such as oil exploration and gravity survey. Compared with MEMS sensors that use voltage output, including capacitance readout and light intensity readout, MEMS resonant sensors use frequency output, which has the advantages of stability and high resolution. Therefore, it is the development direction and trend of high-performance MEMS sensors. In order to achieve high stability and high resolution, it is necessary to improve the sensitivity of MEMS resonant sensors.

[0003] At present, the main methods to improve the sensitivity of MEMS resonant sensors include force, displacement, and strain amplification. The force and displacement amplification methods are relatively common. For example, the patent MEMS resonant accelerometer having improved electrical characteristics (US9354246B2) records that its amplification factor is limited by the size of the lever. For smaller sizes in MEMS sensors, the amplification factor of the lever is usually limited. The strain amplification method, such as Kose, et al. Journal of Micromechanics and Microengineering, 26(4), 045012,2016, etc., is limited by the device processing technology. These limiting factors will reduce the efficiency of sensitivity improvement, so it is necessary to explore new ways to improve sensitivity and thus realize high-performance MEMS resonant sensors.

[0004] In recent years, dynamic systems described by non-Hermitian Hamiltonians have gradually become a research hotspot in the fields of condensed matter physics, acoustics, and optics, mainly including parity-time symmetry systems and anti-parity-time symmetry systems. Following the rapid development of parity-time symmetry systems (Rüter, et al. Nature physics, 6(3), 192-195, 2010, etc.), research on anti-parity-time symmetry systems has gradually emerged in recent years and has been implemented in acoustics (Li, et al. Science, 364(6436), 170-173, 2019), optics (Peng, et al. Nature Physics, 12(12), 1139-1145, 2016), cold atoms (Jiang, et al. Physical review letters, 123(19), 193604, 2019), and other fields. However, to date, anti-parity-time symmetric systems have not been realized in micro-electromechanical systems. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a two-degree-of-freedom resonant MEMS sensor based on active coupling and its application, thereby solving the technical problems of low sensitivity of MEMS sensors in the prior art resulting in poor stability and low resolution.

[0006] To achieve the above object, according to one aspect of the present invention, a two-degree-of-freedom resonant MEMS sensor based on active coupling is provided, characterized in that it includes an active coupling module, a sensing module and a MEMS resonant device;

[0007] The MEMS resonator device comprises a first resonator and a second resonator, wherein the first resonator and the second resonator are connected to form a closed loop through the active coupling module, thereby realizing active coupling;

[0008] The first resonator and the second resonator after being coupled to each other have an anti-odd-time symmetry phenomenon, so that the first resonator and the second resonator have sensitivity to the measurement to be measured;

[0009] The sensing module is connected to the first resonator or the second resonator, and is used to sense the value to be measured and cause the frequency of the first resonator and the second resonator coupled to each other to change, so as to obtain frequency signal data used to calculate the value to be measured.

[0010] Preferably, the active coupling module includes a first active coupling circuit and a second active coupling circuit; the input end of the first active coupling circuit is connected to the output end of the first resonator, and the output end thereof is connected to the input end of the second resonator; the input end of the second active coupling circuit is connected to the output end of the second resonator, and the output end thereof is connected to the input end of the first resonator.

[0011] Preferably, the first active coupling circuit comprises a first amplifier circuit and a first regulating circuit, the input end of the first amplifier circuit is connected to the output end of the first resonator, and the output end of the first amplifier circuit is connected to the input end of the first regulating circuit;

[0012] The first amplifier circuit is used to convert the dynamic current generated by the first resonator into a first voltage, and apply the first voltage to the second resonator; the first adjustment circuit is used to adjust the amplitude of the first voltage generated by the first amplifier circuit and the phase between it and the driving voltage.

[0013] Preferably, the first resonator comprises a first adjustment electrode, a second adjustment electrode, a first driving electrode and a first detection electrode;

[0014] The input end of the first driving electrode is connected to the output end of the driving power supply, and the first driving electrode is used to drive the first resonator to oscillate to generate its natural frequency;

[0015] The output end of the first detection electrode is connected to the input end of the first amplifying circuit, and the first detection electrode is used to convert the vibration of the first resonator into a dynamic current and input it into the first amplifying circuit;

[0016] The first adjustment electrode and the second adjustment electrode are symmetrically arranged, and are both used to adjust the initial deflection caused by process errors.

[0017] Preferably, the first amplifier circuit is a charge amplifier circuit or a current amplifier circuit.

[0018] Preferably, the second active coupling circuit comprises a second amplifier circuit and a second regulating circuit, the input end of the second amplifier circuit is connected to the output end of the second resonator, the output end of the second amplifier circuit is connected to the input end of the second regulating circuit, and the output end of the second regulating circuit is connected to the input end of the first resonator;

[0019] The second amplifier circuit is used to convert the dynamic current generated by the second resonator into a second voltage and apply the second voltage to the first resonator; the second adjustment circuit is used to adjust the amplitude of the second voltage generated by the second amplifier circuit and the phase between it and the driving voltage.

[0020] Preferably, the second resonator comprises a third adjustment electrode, a fourth adjustment electrode, a second driving electrode and a second detection electrode;

[0021] The input end of the second driving electrode is connected to the output end of the driving power supply, and the second driving electrode is used to drive the second resonator to oscillate to generate its natural frequency;

[0022] 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 to convert the vibration of the second resonator into a dynamic current and input it into the second amplifying circuit;

[0023] The third adjustment electrode and the fourth adjustment electrode are symmetrically arranged, and are both used to adjust the initial deflection caused by process errors.

[0024] Preferably, the second amplifier circuit is a charge amplifier circuit or a current amplifier circuit.

[0025] Preferably, the sensing module comprises a force amplifying device, a cantilever beam and a mass block; the cantilever beam is symmetrically arranged on both sides of the mass block, and the mass block is connected to the first resonator through the force amplifying device.

[0026] According to another aspect of the present invention, there is provided an application of the above-mentioned two-degree-of-freedom resonant MEMS sensor based on active coupling in measuring temperature, magnetic field intensity, pressure, stress and strain.

[0027] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0028] 1. The present invention couples two independent resonators to each other by active coupling, introduces the anti-parity-time symmetry phenomenon, and changes the resonant frequency difference between the two resonators by the measurement to be measured, which essentially changes the energy difference between the two, thereby causing the system to approach a special point at the symmetric-asymmetric phase change interface. The two mutually coupled resonators converge rapidly near the special point, thereby greatly improving the sensitivity of the resonant frequencies of the two resonators to the change of the measurement to be measured, and extremely high sensitivity can be achieved within this range;

[0029] 2. The present invention can make a resonant device that is insensitive to the measurement to be measured sensitive by introducing an active coupling module;

[0030] 3. In the working range of the present invention, the frequency changes of the two resonators in the MEMS resonant device are opposite to the direction of the change of the measured value, which can realize frequency differential detection, further improve the sensitivity and improve the common mode suppression;

[0031] 4. The present invention further adjusts the sensitivity of the sensor by adjusting the gain in the adjustment circuit and the frequency difference between the first resonator and the second resonator;

[0032] 5. The present invention can be applied to various sensors such as temperature sensors, magnetic field sensors, pressure sensors, etc., and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of a two-degree-of-freedom resonant MEMS sensor based on active coupling of the present invention;

[0034] Figure 2 It is a schematic diagram of the anti-odd-time symmetry phenomenon in the two-degree-of-freedom resonant MEMS sensor based on active coupling of the present invention;

[0035] Figure 3 is a schematic diagram of sensitivity curves of the first resonator and the second resonator to input acceleration changes when active coupling is not introduced in one embodiment of the present invention;

[0036] Figure 4 It is a schematic diagram of a sensitivity curve of the resonant frequencies of the first resonator and the second resonator to changes in input acceleration when active coupling is introduced in one embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Figure 1 The schematic diagram of the structure of the two-degree-of-freedom resonant MEMS sensor based on active coupling provided by the present invention is as follows: Figure 1 As shown, it includes: a MEMS resonant device, a sensing module and an active coupling module, wherein the MEMS resonant device includes a first resonator 1 and a second resonator 4; the active coupling module includes a first active coupling circuit and a second active coupling circuit, the first active coupling circuit and the second active coupling circuit have the same structure, the first active coupling circuit includes a first amplifying circuit 2 and a first regulating circuit 3, the second active coupling circuit includes a second amplifying circuit 9 and a second regulating circuit 10, and the sensing module includes a force amplifying device 15, a cantilever beam 16 and a mass block 17.

[0039] To further explain, 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 arranged, and the first driving electrode 13 and the first detection electrode 14 are symmetrically arranged; the second resonator 4 includes a third adjustment electrode 5, a fourth adjustment electrode 6, a second driving electrode 7 and a second detection electrode 8, the third adjustment electrode 5 and the fourth adjustment electrode 6 are symmetrically arranged, and the second driving electrode 7 and the second detection electrode 8 are symmetrically arranged.

[0040] To further explain, the output end of the first detection electrode 14 is connected to the input end of the first amplifier circuit 2, the output end of the first amplifier circuit 2 is connected to the input end of the first adjustment circuit 3, the output end of the first adjustment 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 amplifier circuit 9, the output end of the second amplifier circuit 9 is connected to the input end of the second adjustment circuit 10, and the output end of the second adjustment circuit 10 is connected to the input end of the first driving electrode 13.

[0041] Further explanation, it also includes a driving power supply, which is used to output a driving voltage signal, and the output end of the driving power supply is connected to the input end of the first driving electrode 13 and the input end of the second driving electrode 7 respectively.

[0042] To further explain, the mass block 17 is connected to the force amplifying device 15 , and the cantilever beam 16 is disposed on both sides of the force amplifying device 15 .

[0043] Optionally, the first amplifier circuit 2 is a charge amplifier circuit or a current amplifier circuit.

[0044] Optionally, the second amplifier circuit 9 is a charge amplifier circuit or a current amplifier circuit.

[0045] It should be noted that the two-degree-of-freedom resonant MEMS sensor based on active coupling proposed in the present invention introduces an anti-parity-time symmetry phenomenon compared to the prior art, so as to make the first resonator 1 and the second resonator 4 sensitive to the measurement to be measured.

[0046] 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 by actively coupling the first resonator 1 and the second resonator 4, both the first resonator 1 and the second resonator 4 are sensitive to the measurement.

[0047] Specifically, Figure 2As shown in (a), without the introduction of active coupling, the curve of the resonant frequency of the first resonator changing with δ (i.e., the change caused by the to-be-measured value) indicates that the first resonator is sensitive to the to-be-measured value; Figure 2 (b) shows the variation curve of the frequency of the second resonator with δ (i.e., the variation caused by the measurement to be measured) without the introduction of active coupling, indicating that the second resonator is insensitive to the measurement to be measured. Figure 2 (a) and Figure 2 (b) shows that the anti-parity-time symmetry phenomenon does not occur when no active coupling is introduced. Figure 2 (c) and Figure 2 (d) shows the variation curves of the resonant frequencies of the first resonator and the second resonator with δ (i.e., the variation caused by the measurement to be measured) after the active coupling is introduced. It can be seen that the anti-odd-symmetry phenomenon occurs after the active coupling is introduced, where the first resonator and the second resonator both have two resonant frequencies, i.e. Figure 2 (d) Mode 1 and Mode 2 are marked, where the resonant frequencies of Mode 1 and Mode 2 are both sensitive to the measurement. Figure 2 (d) shows the exceptional point. Near this point, the resonant frequencies of Mode 1 and Mode 2 approach each other rapidly and finally converge at the exceptional point. In this range, the sensitivity of the resonant frequencies of Mode 1 and Mode 2 to δ (i.e., the change caused by the measurement to be measured) is greatly improved. That is, the first resonator and the second resonator are highly sensitive to the measurement to be measured, which improves the sensitivity of the sensor and the detection accuracy. It should be noted that Figure 2 As shown in (d), at the exceptional point, the first resonator and the second resonator have the highest sensitivity to the measured value, and the sensor is most accurate in detecting the measured value. The present invention improves the sensitivity of the sensor by using the anti-odd-symmetry phenomenon and the characteristics in this convergence interval. Figure 2 (e) Figure 2 (f) and Figure 2 (g) shows the amplitude-frequency response characteristics of the first resonator in different intervals.

[0048] In a more specific embodiment, the above-mentioned two-degree-of-freedom resonant MEMS sensor based on active coupling is applied to an acceleration sensor. Figure 3 (a) Figure 3 (b) and Figure 3 (c) Figure 3 (a) shows the sensitivity curve of the resonance frequency of the independent first resonator to the input acceleration change without the introduction of active coupling. Figure 3 (b) shows the sensitivity curve of the resonant frequency of the independent second resonator to the input acceleration change without the introduction of active coupling, which is given by Figure 3 (c) It can be seen that the resonant frequency of the first resonator is sensitive to changes in external acceleration, and its sensitivity is 2800 Hz / g. The output frequency of the second resonator is almost unaffected by external acceleration, and its sensitivity to acceleration is 0 Hz / g.

[0049] Specifically, when introducing Figure 1 The active coupling module shown, that is, the first amplifying circuit 2 and the first regulating circuit 3 constitute the first active coupling circuit, the second amplifying circuit 9 and the second regulating circuit 10 constitute the second active coupling circuit, the phase and gain adjustment are performed by the first regulating circuit 3 and the second regulating circuit 10, and appropriate parameter values ​​are selected, that is, Δφ1 (that is, the phase of the first regulating circuit) ≈ 90° (or ≈ -90°), Δφ2 (that is, the phase of the second regulating circuit) ≈ Δφ1 (or exactly the same); G1 ≈ G2, the specific value can be adjusted according to the sensitivity requirement, for example, 10 times the gain value calculated by the initial frequency difference between the first resonator and the second resonator.

[0050] Specifically, after the active coupling module is introduced, the curve of the resonant frequency of the first resonator and the second resonator changing with the external acceleration is as follows: Figure 4 As shown, the sensitivity of the first resonator is increased from 2800 Hz / g to 52500 Hz / g, and the sensitivity of the second resonator is changed from 0 Hz / g to -50500 Hz / g.

[0051] Further explanation, such as Figure 1 The two-degree-of-freedom resonant MEMS sensor based on active coupling shown can also be applied to realize high-sensitivity resonant temperature sensors, magnetic field sensors, pressure sensors, stress strain sensors, etc.

[0052] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A two-degree-of-freedom resonant MEMS sensor based on active coupling, characterized in that: It includes an active coupling module, a sensing module and a MEMS resonant device; The MEMS resonator device comprises a first resonator (1) and a second resonator (4), wherein the first resonator (1) and the second resonator (4) are connected via the active coupling module to form a closed loop, thereby achieving active coupling; After being coupled to each other, the first resonator (1) and the second resonator (4) exhibit an anti-odd-time symmetry phenomenon, so that the first resonator (1) and the second resonator (4) are sensitive to the measurement to be made; The sensing module is connected to the first resonator (1) or the second resonator (4), and is used to sense the value to be measured and cause the frequency of the first resonator and the second resonator to change, so as to obtain frequency signal data for calculating the value to be measured; 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 to the output end of the first resonator (1), and the output end of the first active coupling circuit is connected to the input end of the second resonator (4); The input end of the second active coupling circuit is connected to the output end of the second resonator (4), and the output end of the second active coupling circuit is connected to the input end of the first resonator (1); The first active coupling circuit comprises a first amplifier circuit (2) and a first regulating circuit (3), wherein the input end of the first amplifier circuit (2) is connected to the output end of the first resonator (1), and the output end of the first amplifier circuit (2) is connected to the input end of the first regulating circuit (3); The first amplifier circuit (2) is used to convert the dynamic current generated by the first resonator (1) into a first voltage, and apply the first voltage to the second resonator (4); the first regulating circuit (3) is used to regulate the amplitude of the first voltage generated by the first amplifier circuit (2) and the phase between the first voltage and the driving voltage; the second active coupling circuit includes a second amplifier circuit (9) and a second regulating circuit (10), the input end of the second amplifier circuit (9) is connected to the output end of the second resonator (4), the output end of the second amplifier circuit (9) is connected to the input end of the second regulating circuit (10), and the output end of the second regulating circuit (10) is connected to the input end of the first resonator (1); The second amplifying circuit (9) is used to convert the dynamic current generated by the second resonator (4) into a second voltage, and apply the second voltage to the first resonator (1); the second regulating circuit (10) is used to regulate the amplitude of the second voltage generated by the second amplifying circuit (9) and the phase between the second voltage and the driving voltage.

2. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1, characterized in that: The first resonator (1) comprises a first adjustment electrode (11), a second adjustment electrode (12), a first driving electrode (13) and a first detection electrode (14); The input end of the first driving electrode (13) is connected to the output end of the driving power supply, and the first driving electrode (13) is used to drive the first resonator (1) to oscillate to generate its natural frequency; The output end of the first detection electrode (14) is connected to the input end of the first amplifying circuit (2), and the first detection electrode (14) is used to convert the vibration of the first resonator (1) into a dynamic current and input it into the first amplifying circuit (2); The first adjustment electrode (11) and the second adjustment electrode (12) are symmetrically arranged and are both used to adjust the initial deflection caused by process errors.

3. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 2, characterized in that: The first amplifier circuit (2) is a charge amplifier circuit or a current amplifier circuit.

4. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1, characterized in that: The second resonator (4) comprises a third adjustment electrode (5), a fourth adjustment electrode (6), a second driving electrode (7) and a second detection electrode (8); The input end of the second driving electrode (7) is connected to the output end of the driving power supply, and the second driving electrode (7) is used to drive the second resonator (4) to oscillate to generate its natural frequency; 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 to convert the vibration of the second resonator (4) into a dynamic current and input it into the second amplifying circuit (9); The third adjustment electrode (5) and the fourth adjustment electrode (6) are symmetrically arranged, and are both used to adjust the initial deflection caused by process errors.

5. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 4, characterized in that: The second amplifier circuit (9) is a charge amplifier circuit or a current amplifier circuit.

6. The two-degree-of-freedom resonant MEMS sensor based on active coupling according to claim 1, characterized in that: The sensing module comprises a force amplifying device (15), a cantilever beam (16) and a mass block (17); the cantilever beam (16) is symmetrically arranged on both sides of the mass block (17), and the mass block (17) is connected to the first resonator (1) through the force amplifying device (15).

7. Application of the two-degree-of-freedom resonant MEMS sensor based on active coupling according to any one of claims 1 to 6 in measuring temperature, magnetic field intensity, pressure, stress and strain.

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