Resonant sensor for parallel measurement of multiple physical quantities and measurement method

Abstract

The invention relates to a resonant sensor for parallel measurement of multiple physical quantities and a measurement method. The resonant sensor comprises a substrate layer and a device layer; the device layer comprises an internal mass block, a main vibration ring, a nested multilayer ring and an external anchoring ring, the internal mass block is fixed at the center of the substrate layer, and the distance between the internal mass block and the main vibration ring is 3-5 microns. The measurement method comprises the following steps: applying an excitation signal to the sensor; performing frequency modulation sensing analysis on vibration of the sensor in different modes to obtain values of different physical quantities to be measured, and if coupling exists, performing decoupling calculation. Compared with the prior art, the sensor has different sensitivities to different physical quantities in different modes, cross coupling can be avoided, and simultaneous measurement of a plurality of physical quantities is realized; an excitation signal with the working frequency being the sum of the resonant frequencies of the multiple modes is applied to the resonant sensor, frequency modulation sensing analysis and decoupling calculation are carried out on vibration in different modes, and multiple physical quantities can be obtained.

Description

Technical Field

[0001] The invention relates to a sensor, and in particular to a resonant sensor and a measuring method for parallel measurement of multiple physical quantities. Background Art

[0002] Micro-electromechanical system (MEMS) resonant sensor is a sensor made by organically combining micro-electromechanical processing technology and mechanical resonant sensing technology. This type of sensor detects changes in the measured physical quantity by measuring the vibration frequency and vibration state of the object, and has the advantages of high precision, high sensitivity, fast response and good stability.

[0003] In the application of micro-electromechanical system (MEMS) resonant sensors, the sensing of a physical parameter is often affected by other physical quantities, and there is a problem of cross-coupling of physical parameters, resulting in cross-coupled readings. This problem can currently be solved by environmental control and output compensation, but these two technologies require additional sensors, reference resonators and interface circuits, and may reduce the resolution of the sensor and increase system power consumption. In addition, the improvement of resonator performance is to some extent limited by existing optimization methods, such as device structure design and interface circuit optimization.

[0004] In summary, how to design a sensor that can measure multiple physical quantities simultaneously and avoid cross-coupling readings is a technical problem that needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a resonant sensor and a measurement method for measuring multiple physical quantities in parallel in order to overcome the defect of the prior art that multiple physical quantities cannot be accurately measured simultaneously.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, a resonant sensor for parallel measurement of multiple physical quantities is provided, the resonant sensor comprising a substrate layer and a device layer; the device layer comprises, from the inside to the outside, a circular internal mass block and a main vibration ring, a nested multi-layer ring and an external anchoring ring that are interconnected and concentric, the internal mass block being fixed at the center of the substrate layer at a distance of 3 to 5 microns from the main vibration ring; when the resonant sensor is working, an excitation signal comprising the sum of multiple modal resonant frequencies is applied to the resonant sensor, the initial resonant frequency of the resonant sensor in different modes and the resonant frequency after sensing the physical quantity to be measured are measured, and the resonant frequency is analyzed to obtain the value of the physical quantity to be measured.

[0008] As a preferred technical solution, the nested multi-layer rings include a plurality of concentric nested rings connected by spokes.

[0009] As a preferred technical solution, the nested ring has a different diameter and width, and different stiffness and frequency from the main vibration ring.

[0010] As a preferred technical solution, the device layer further comprises a support ring, which is installed between the nested multi-layer ring and the external anchor ring and connected to the nested multi-layer ring and the external anchor ring through spokes.

[0011] As a preferred technical solution, the internal mass block is fixed at the center of the substrate layer through a suspension spring and an internal anchor.

[0012] As a preferred technical solution, the substrate layer and the device layer are anisotropic single crystal silicon, and the anisotropic single crystal silicon has different influence rules on different modes; the modes include second-order wine glass modes and third-order wine glass modes, and the resonant sensor is sensitive to acceleration after receiving the excitation signal of the second-order wine glass mode, and is sensitive to angular velocity after receiving the excitation signal of the third-order wine glass mode.

[0013] According to another aspect of the present invention, a measurement method of a resonant sensor using parallel measurement of multiple physical quantities is provided, which specifically comprises the following steps:

[0014] Step S101, applying an excitation signal to the resonant sensor, wherein the operating frequency of the excitation signal is the sum of the resonant frequencies of multiple modes, and different modes have different sensitivities to different physical quantities to be measured;

[0015] Step S102, performing frequency modulation sensing analysis on the vibration of the resonant sensor in different modes to obtain the values ​​of different physical quantities to be measured. If there is coupling between the different physical quantities to be measured, executing step S103;

[0016] Step S103, defining the sensitivity of different modes to different physical quantities to be measured, the product of the variation of different physical quantities to be measured and the corresponding sensitivity is the frequency variation of different modes, solving the equation group to obtain the values ​​of different physical quantities to be measured.

[0017] As a preferred technical solution, the step S101 is specifically as follows:

[0018] There is a potential difference between the internal mass block and the main vibration ring; the internal mass block is displaced under the action of the physical quantity to be measured, and the distance between the internal mass block and the main vibration ring changes; electrostatic force is generated between the internal mass block and the main vibration ring, and the stiffness of the main vibration ring changes; multiple modal frequencies change due to the change in stiffness.

[0019] As a preferred technical solution, the physical quantities to be measured include acceleration and angular velocity, and the modes include second-order wine glass mode and third-order wine glass mode; the resonant frequency of the second-order wine glass mode is inversely proportional to the acceleration; the third-order wine glass mode is divided into the first-third-order wine glass mode and the second-third-order wine glass mode according to the main vibration direction, and the frequency difference between the resonant peaks of the first-third-order wine glass mode and the second-third-order wine glass mode is proportional to the angular velocity.

[0020] As a preferred technical solution, the step S103 is specifically as follows:

[0021] The initial resonant frequency of the second-order wine glass mode is f a0 , the difference between the initial frequencies of the first third-order mode and the second third-order mode is △f g0 ; The resonant frequency after the second-order wine glass mode changes is f a , the difference between the resonant frequencies of the first third-order mode and the second third-order mode after the change is △f g ; When the sensitivity of the resonant frequency to acceleration and angular velocity is linear, the equation system is obtained:

[0022] f a =f a0 +S aa △a+S ag △Ω z ,

[0023] △f g =△f g0 +S ga △a+S gg △Ω z ,

[0024] Among them, △a and △Ω z are the changes of acceleration and angular velocity, S aa and S ag is the sensitivity of the second-order wine glass mode to acceleration and angular velocity, S ga and S gg are the sensitivities of the third-order wine glass mode to acceleration and angular velocity respectively; solving the equations yields the changes in acceleration and angular velocity.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The device layer of the present invention includes an internal mass block, a main vibration ring, a nested multi-layer ring and an external anchoring ring. The structure has different sensitivities to different physical quantities in different modes. When measuring multiple physical quantities at the same time, cross coupling can be avoided, thereby achieving simultaneous measurement of multiple physical quantities.

[0027] 2) In the present invention, multiple nested rings, support rings and other structures are connected by spokes with low stiffness to ensure weak coupling between structures; the width of the main vibration ring is inconsistent with that of the nested rings, which can control the sensitivity of different modes to different physical quantities; adding support rings can reduce the negative impact of anchor point loss on the vibration of the nested rings;

[0028] 3) The present invention applies an excitation signal whose operating frequency is the sum of the resonant frequencies of multiple modes to the resonant sensor. Since different modes have different sensitivities to different physical quantities to be measured, multiple physical quantities can be obtained by performing frequency modulation sensing analysis and decoupling calculation on the vibrations in different modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of a resonant sensor for parallel measurement of multiple physical quantities according to the present invention;

[0030] Figure 2 It is a schematic diagram of the device layer structure of the present invention;

[0031] Figure 3 This is a front view of the device layer of the present invention;

[0032] Figure 4 It is a schematic diagram of the local structure of the device layer of the present invention;

[0033] Figure 5 This is a schematic diagram of the structure in which the internal mass block of the present invention is fixed at the center of the substrate layer through a suspension spring;

[0034] Figure 6 It is a schematic diagram of various modes of the present invention;

[0035] Figure 7 Schematic diagram of a double-ended fixed beam for exciting a MEMS with an excitation signal;

[0036] Figure 8 This is the frequency response diagram after the excitation signal excites the double-ended fixed beam of the MEMS;

[0037] Fig. 9 This is the frequency response change diagram of the MEMS double-end fixed beam after mass disturbance;

[0038] Fig.10 A schematic diagram of a multi-modal excitation mechanism of a resonant sensor for parallel measurement of multiple physical quantities according to the present invention;

[0039] Fig.11 A graph showing the variation of the resonant frequency of the second-order wine glass mode and the third-order wine glass mode with acceleration of a resonant sensor for parallel measurement of multiple physical quantities according to the present invention;

[0040] Fig.12It is a time domain analysis of the third-order wine glass mode when the resonant sensor for parallel measurement of multiple physical quantities of the present invention does not measure the angular velocity;

[0041] Fig.13 It is the fast Fourier transform result of the third-order wine glass mode when the resonant sensor for parallel measurement of multiple physical quantities of the present invention does not measure the angular velocity;

[0042] Fig.14 It is a time domain analysis of the third-order wine glass mode when the resonant sensor for parallel measurement of multiple physical quantities of the present invention detects the angular velocity;

[0043] Fig.15 It is the fast Fourier transform result of time domain analysis of the third-order wine glass mode when the resonant sensor for parallel measurement of multiple physical quantities of the present invention detects the angular velocity;

[0044] Fig.16 A diagram showing the drift of the resonance frequency of the third-order wine glass mode of a resonant sensor for parallel measurement of multiple physical quantities according to the present invention with angular velocity;

[0045] The numbers in the figure show:

[0046] 1. Substrate layer, 2. Device layer, 21. Internal mass block, 22. Main vibration ring, 23. Nested multi-layer ring, 24. External anchoring ring, 25. Support ring, 251. First support ring, 252. Second support ring, 26. Spokes, 27. Suspension spring, 28. Internal anchor, 3. External electrode. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0048] MEMS resonators are widely used in the field of sensing. In addition to their advantages such as miniaturization, light weight, and high quality factor, they are also due to the sensitivity of their vibration modes to small disturbances. For a resonator, different vibration modes can be exhibited at different excitation frequencies. This is because there are multiple modes in a resonant system. Among the multiple modes, the lowest frequency is the first-order mode, and the frequency difference between different-order modes is relatively large; in the same-order mode, there are usually multiple modes with relatively close or even matching frequencies, showing similar vibration modes. Different-order modes of a resonator have different operating frequencies, and have different sensing sensitivities, operating bandwidths or quality factors for different physical quantities. Therefore, it is crucial to fully understand and utilize the different modal characteristics of the resonant system for the design of a resonant sensor. Ring resonators are often used as gyroscopes due to their unique in-plane modes, and nested ring resonators are made up of multiple resonant rings nested. Compared with traditional single-ring resonators, nested ring resonators have larger effective mass and transducer area, and can also effectively reduce the impact of damping, so they are suitable for gyroscopes with modal frequency matching. In order to realize the function of composite sensing, the present invention provides a resonant sensor and a measurement method for parallel measurement of multiple physical quantities, which has the ability to sense different modes (such as second-order wine glass mode and third-order wine glass mode) of different physical quantities (such as acceleration and angular velocity) and decouple the sensing of multiple physical quantities as much as possible.

[0049] Example 1

[0050] like Figure 1 As shown, the present invention provides a resonant sensor for parallel measurement of multiple physical quantities, which is circular in shape and includes a substrate layer 1 and a device layer 2. Figure 2 to Figure 4 As shown, the device layer 2 includes an internal mass block 21 , a main vibration ring 22 , a nested multi-layer ring 23 , a support ring 25 and an external anchoring ring 24 .

[0051] like Figure 5As shown, the internal mass block 21 is circular, and the internal mass block 21 is anchored in the center of the substrate layer 1 through the suspension spring 27 and the internal anchor 28, so that it can produce displacement in the plane. The outside of the internal mass block 21 is the main vibration ring 22, which is one of the main resonant parts of the resonator. There is no direct connection between the internal mass block 21 and the main vibration ring 22, but the two are very close to each other to ensure that the electrostatic softening effect can be generated between the main vibration ring 22, and the distance between the two is 3 to 5 microns. The internal mass block 21 does not participate in the resonance, but can produce displacement under the influence of acceleration. When there is a potential difference between the internal mass block 21 and the main vibration ring 22, when the small distance between the main vibration ring 22 and the internal mass block 21 changes, due to the electrostatic softening effect, the generated electrostatic force will change the stiffness of the main vibration ring 22, and the modal frequency of the resonant sensor has a strong sensitivity to stiffness disturbances, so the combination of the internal mass block 21 and the main vibration ring 22 can achieve the effect of acceleration sensing.

[0052] A nested multi-layer ring 23 is provided on the outside of the main vibration ring 22. The nested multi-layer ring 23 includes a plurality of concentric nested rings connected by spokes 26. The nested rings have a different width from the main vibration ring 22. The resonance frequencies of the main vibration ring 22 and the nested multi-layer ring 23 can be regulated by adjusting the width, which can also control the sensitivity of different modes to acceleration and angular velocity.

[0053] A support ring 25 is provided outside the nested multi-layer ring 23. The support ring 25 includes a concentric first support ring 251 and a second support ring 252. The first support ring 251 and the second support ring 252 are connected by spokes 26. The first support ring 251 is connected to the nested multi-layer ring 23 by spokes 26, and the second support ring 252 is connected to the external anchor ring 24 by spokes 26. The nested multi-layer ring 23 is directly fixed to the external anchor ring 24. The anchor loss will have a negative impact on the vibration of the nested multi-layer ring 23. Adding the support ring 25 can reduce the anchor loss. The distance between the first support ring 251 and the second support ring 252 is large, which is greater than the distance between the nested rings.

[0054] The spokes 26 have as small a stiffness as possible and as few a number as possible to ensure weak coupling and resonant mechanical connection between structures. The stiffness of the spokes 26 connected between the nested rings is less than one percent of the stiffness of the nested rings, and the stiffness of the spokes 26 connected between the first support ring 251 and the second support ring 252 is less than one percent of the stiffness of the support ring 25.

[0055] An external anchoring ring 24 is provided outside the supporting ring 25 for fixing the components.

[0056] The present invention is driven by the external electrode 3, which is evenly distributed in the circumferential area between the nested multi-layer ring 23 and the support ring 25, and its driving or sensing function is distinguished at different angles.

[0057] The main expectation of the present invention is to enable the main vibration ring 22 and the nested multi-layer ring 23 to independently realize the sensing function of different physical quantities. Therefore, in the modal analysis of the device, the most ideal situation is:

[0058] (1) A main vibration direction is unidirectional or orthogonal, and the main vibration ring 22 is the dominant resonance mode. Its symmetric mode can be separated by anisotropic single crystal material to achieve single mode sensitivity to acceleration.

[0059] (2) Two frequency-matched angular velocity sensing modes, the vibration mode is dominated by the nested multi-layer ring 23, and the main vibration ring 22 remains almost stationary, reducing the impact of acceleration on the angular velocity sensing mode frequency.

[0060] (3) The intrinsic coupling between the two modes is extremely small, that is, when any one of the modes is excited to sense a certain physical quantity, it will not be affected by the other physical quantity (or it will be extremely small).

[0061] Based on the above purpose, a modal analysis of a resonant sensor for parallel measurement of multiple physical quantities was performed, and the n = 2 wine glass mode (resonant frequency is ω a ), n = Mode 3-I and Mode 3-II in the 3rd-order wine glass mode (the resonant frequency is ω g ), and pseudo-extended modalities, such as Figure 6 As shown (only the main vibration ring 22 and the nested multi-layer ring 23 that participate in the resonance are shown), n is the order. Due to the presence of the support ring 25 in the resonator, the vibration of the nested multi-layer ring 23 in these modes has been proven to be more stable than the case without the support ring 25, and is less affected by the anchor point loss. The main vibration direction of the n = 2 mode is uniaxial, and the n = 2 wine glass mode is more sensitive to the stiffness disturbance caused by the change of external acceleration due to the single axial direction; and the two modes of the n = 3 wine glass mode are suitable for sensing angular velocity because of the frequency matching and the complex axial direction, which easily produces Coriolis force coupling; in the pseudo-extended mode, the main vibration ring 22 and the nested multi-layer ring 23 are in anti-phase motion, and there is also a certain potential in the sensing of acceleration.

[0062] Example 2

[0063] The invention provides a method for measuring multiple physical quantities in parallel, which adopts a resonant sensor for measuring multiple physical quantities in parallel to perform measurement.

[0064] A multi-modal excitation method is used to apply an excitation signal to the resonant sensor. The operating frequency of the excitation signal is the sum of the resonant frequencies of multiple modes. The low-order and high-order modes of the resonant sensor that measure multiple physical quantities in parallel are simultaneously excited, so that they are used to detect acceleration and angular acceleration, respectively. The vibration of the resonant sensor in different modes is subjected to frequency modulation sensing and analysis. Acceleration force decoupling is achieved by regulating the vibration amplitude of the main vibration ring 22, while angular velocity decoupling is achieved by separating the low-order symmetric modal frequencies and matching the high-order symmetric modal frequencies. When external inertial force is input, the resonant sensor outputs frequency output readings of the cross-coupled two inertial forces, and then a net inertial force reading is obtained through a multi-parameter decoupling method.

[0065] Resonant sensors driven in a certain mode are very sensitive to external disturbances, which are specifically manifested in the amplitude change and resonant frequency drift of the mode. Resonators that sense modal amplitude changes generally use the amplitude modulation (AM) sensing principle. The frequency modulation (FM) sensing method is used to sense the resonant frequency shift of the mode. The specific mechanism is: when the resonant sensor is driven at a specific modal resonant frequency, once the resonant sensor is subjected to a specific external disturbance (such as changes in ambient temperature, pressure, or acceleration / angular velocity and other physical quantities), the resonant frequency will shift. Compared with AM sensing, the advantage of the FM sensing method is that its scale factor is not limited, it is relatively stable, and the working bandwidth is not affected by modal frequency matching. Taking the microbeam used for micromass sensing as an example, assuming that it is driven in the first-order mode, at this time the microbeam adsorbs a certain gas molecule, and its effective mass increases slightly, it can be observed that the resonant frequency of its first-order mode changes from the initial value f 0 Reduce to (f 0 -Δf), such as Fig. 9 Ideally, the resonant frequency should change linearly with the independent variable, but due to environmental factors, manufacturing errors and defects, this sensitive change will show nonlinear characteristics.

[0066] 1) The specific process of acceleration sensing analysis is as follows:

[0067] The output reading of the resonant sensor is the change in modal resonant frequency. Sensing is mainly based on the frequency modulation (FM) sensing method, which detects the shift of the resonant frequency corresponding to the resonant peak as the external disturbance occurs. In actual testing, a closed-loop circuit can be built to control the amplitude output of the resonant sensor to a set value and detect its frequency change. The FM principle applied to resonant sensors has the advantages of stable scale factor and unlimited bandwidth. The n=2 wine glass mode and n=3 wine glass mode of the resonant sensor are numerically analyzed respectively. After inputting the external acceleration into the model, the frequency response of the n=2 wine glass mode and the n=3 wine glass mode can be obtained as the acceleration changes. The sensitivity of the two-order modes to acceleration is shown in Figure 2. Fig.11As shown in the figure, the results show that the resonant frequency of the n=2 wine glass mode decreases monotonically with the increase of external acceleration, and is more sensitive to acceleration; in contrast, the resonant frequency of the n=3 wine glass mode changes little with acceleration, which is three orders of magnitude lower than the n=2 wine glass mode, proving the feasibility of the n=2 wine glass mode as an acceleration sensing mode, and the n=3 wine glass mode is almost unaffected by the cross-coupling of acceleration.

[0068] 2) The specific process of angular velocity sensing analysis is as follows:

[0069] The sensing of angular velocity is based on the FM gyroscope model, which uses the inter-axis coupling generated by the Coriolis force to sense angular velocity. For the resonant sensor, the main vibration directions of the two n=3 modes of frequency matching are defined as the x-axis and the y-axis, and the axial direction perpendicular to the xy-axis plane is the z-axis. The dynamic equation of the resonant sensor is:

[0070]

[0071] where x and y, γ x With γ y ,ω x With ω y are the amplitude, damping factor and resonant frequency of the two modes, F x With F y is the driving force in two axial directions, m eq is the effective mass of the resonant sensor, ω d is the driving frequency, Ω z is the angular velocity around the z-axis, and η is the Coriolis coupling coefficient (angular gain). The fourth-order Runge-Kutta method is used to numerically simulate the dynamic equations of the resonant sensor, and the time domain and fast Fourier transform (FFT) results of this model can be obtained.

[0072] like Fig.12 and 13 As shown, when there is no angular velocity (Ω z = 0) and applying the initial driving force, the first third-order wine glass mode (mode 3-I) and the second third-order wine glass mode (mode 3-II) begin to resonate due to frequency matching. Due to the existence of damping, the vibration gradually decays over time. The final FFT image presented is two resonance peaks that almost overlap each other. The peak frequency is the initial resonance frequency of the two mode frequencies matching. Fig.14 and 15 As shown in the figure, the time domain and FFT results after adding the external angular velocity (Ω z=10Hz=3600deg / s), we can see that the time domain analysis results have changed significantly. This is because the inter-axis coupling term caused by the Coriolis force and the resonance in the two axes are mixed together to produce new amplitudes and frequencies. The FFT result is more intuitive. It can be seen that two resonance peaks are generated with the initial resonance frequency as the center and shifted to both sides of the center, that is, the addition of angular velocity produces frequency splitting. After verification, it can be proved that the generated frequency difference Δf (that is, the frequency difference between the two resonance peaks) is consistent with the measured angular velocity Ω z It is directly proportional to the Coriolis coupling coefficient (angular gain) η.

[0073] In addition to directly performing numerical analysis on the dynamic equations of the resonant sensor, theoretical deduction can also be performed to prove the relationship between the above frequency difference Δf and the angular velocity. By converting equation (1) into a matrix form and omitting the drive term, we can obtain:

[0074]

[0075] in, is the modal displacement vector, the damping matrix Stiffness Matrix Coriolis coupling matrix The coupling term γ caused by manufacturing error is introduced into the damping matrix and stiffness matrix. xy and ω xy , and then use the rotating wave approximation to solve equation (2), we can get the system's dynamic characteristic matrix D at the system's own angular velocity ω:

[0076]

[0077] When the modal frequencies are matched, all coupling terms (ω x =ω y =ω 0 , γ x =γ y =γ 0 ,ω xy =0,γ xy =0), the two eigenvalues ​​of D can be directly solved, and the real part of the eigenvalue λ ± = ±ηΩ z , this eigenvalue represents the change of the two modal resonant frequencies under complex dynamics, so the difference between the two modal frequencies can be obtained:

[0078] Δf=λ + -λ - =2ηΩ z (4)

[0079] The conclusion of formula (4) is Fig.14 and 15The results are consistent with those of the theoretical derivation and numerical analysis, which proves the correctness of the theoretical derivation and numerical analysis. It can be directly concluded by numerically analyzing the characteristic matrix D that the frequency mismatch (Δω=|ω x -ω y |) and the change of frequency difference when there is an error term. Fig.16 The figure shows the drift of the resonant frequency of mode 3-I and mode 3-II with angular velocity. In the case of mode matching, the frequency drift changes linearly with angular velocity, which is similar to Fig.14 and 15 The results of the fourth-order Runge-Kutta method match the results of the fourth-order Runge-Kutta method; the larger the frequency mismatch, the lower the linearity and sensitivity. The results show that the n=3 mode has a stable scaling factor for the angular velocity. In addition, the n=2 mode does not have a frequency-matching mode of the same order, so there is no Coriolis coupling, so the n=2 mode is almost not affected by the cross coupling of the angular velocity.

[0080] 3) The principle of multi-modal excitation and multi-parameter decoupling is as follows:

[0081] The traditional resonator driving method is to make the resonator work in a specific mode, that is, the frequency of the driving signal is set to the resonant frequency of a single mode, while multi-modal excitation is an excitation method that can use a single signal to excite multiple modes of the resonator. The multi-modal excitation method is based on the principle of parametric pumping. The input signal of the driving resonator is a blue sideband excitation (BSE) signal, and the operating frequency is set to the sum of the resonant frequencies of the required modes, so as to excite multiple modes in the resonator. Figure 7 As shown in the figure, taking a typical double-ended fixed microbeam as an example, the device is driven by a BSE signal with a frequency equal to the sum of the first two out-of-plane modal resonant frequencies of the microbeam. Signals close to the two modal frequencies can be demodulated from the output signal of the microbeam, as shown in Figure 8 This indicates that the BSE signal excites two modes in the microbeam simultaneously. This multi-modal excitation method can be applied to any resonator and any mode in the resonator.

[0082] In practical applications, the output of the resonator is always affected by the cross-coupling of multiple physical quantities. This problem can be solved by introducing a multi-parameter decoupling method in the resonator with multi-modal excitation. For example, if you want to decouple the output reading of the resonator output affected by m cross-coupled physical quantities, you need to excite m modes in the resonator, and the BSE signal frequency is f blue =f 1，0 +f 2，0 +…+f m，0 , where f i，0 (i=1, 2, ..., m) is the initial resonant frequency of each mode. Assuming that the output metric of each mode is the resonant frequency and its sensitivity to each physical quantity is linear, the output frequency of m modes is:

[0083]

[0084] Among them, f i , Δx j , S ij (i=1, 2, ..., m) are the output resonant frequency of the ith mode, the change of the jth cross-coupled physical quantity, and the sensitivity of the ith mode to the ith physical quantity, and the sensitivity matrix must be reversible. The relationship between the change of the net physical quantity and the change of the output resonant frequency can be easily derived from equation (5), thereby realizing multi-parameter decoupling in the case of linear sensitivity.

[0085] The present invention uses a blue sideband excitation (BSE) signal to simultaneously excite two modes in the resonant sensor: the n=2 mode mainly used to sense acceleration, with a modal frequency of ω a ; The two frequency-matched high-order n=3 modes used mainly for sensing angular velocity are mainly based on the frequency modulation principle for sensing angular velocity, and the modal frequency is ω g The frequency of the input BSE signal is the sum of the resonant frequencies of the n = 2 mode and the n = 3 mode, that is, ω blue =ω a +ω g Due to the frequency matching characteristics of n=3 modes, the angular velocity sensing component of the multi-modal excitation signal can act on mode 3-I and mode 3-II at the same time. Fig.10 As shown, when a BSE signal is input into the resonant system, it will generate two excitation components, which are used to excite the n=2 mode and the n=3 mode respectively: the excitation component 1 is used to excite the mode 2; the excitation component 2, which can only excite a single mode, can simultaneously excite the two matching modes of mode 3-I and mode 3-II.

[0086] Through the structural design of the resonant sensor, in an ideal situation, the cross coupling of the two physical quantities can be directly eliminated. However, once there is cross coupling, a multi-parameter decoupling method is required to obtain a pure reading. In the initial state, there are two initial output readings of the sensor: the initial resonant frequency f of the second-order wine glass mode (n = 2 mode) a0 , the difference between the initial frequencies of the first third-order mode and the second third-order mode is △f g0 , ideally this value is 0Hz. When the external acceleration and angular velocity change, the output readings of the two modes will be obtained after the changes, f a With △f g (The resonant frequency after the second-order wine glass mode changes is f a , the difference between the resonant frequencies of the first third-order mode and the second third-order mode after the change is △f g ). When the sensitivity of the output readings to the inertial force is linear, the two output readings can be written as:

[0087]

[0088] Among them, Δa and ΔΩ z are the changes of acceleration and angular velocity, S aa and S ag is the sensitivity of the second-order wine glass mode to acceleration and angular velocity, S ga and S gg is the sensitivity of the third-order wine glass mode to acceleration and angular velocity respectively; set Δf a =f a -f a0 , Δf g0 = 0, transform equation group (6) into acceleration and angular velocity output matrix form:

[0089]

[0090] In order to make the inverse matrix of the sensitivity matrix in equation (7) exist, and because of the different sensitivities of different modes to the sensed measurement, we set S aa ≠S ga , S ag ≠S gg By utilizing the difference in sensitivity of different modes to different inertial forces, the decoupled inertial forces can be obtained.

[0091] The present invention has the following advantages:

[0092] 1) Detect acceleration and angular velocity simultaneously: Since this solution uses multi-modal excitation and multi-parameter decoupling methods, a single resonator can be used to realize the composite sensing function of sensing multiple inertial forces. Traditional inertial measurement units (IMUs) contain multiple accelerometers, a single gyroscope, and complex interface circuits, while this solution can realize the composite sensing function with only a single resonator, saving device space and cost, and realizing the miniaturization of IMUs.

[0093] 2) Stable sensitivity and working bandwidth: Due to the use of FM principle, the sensor's scale factor is sufficiently stable and the working bandwidth is not limited;

[0094] 3) Noise suppression: After decoupling the two cross-coupled inertial forces, the output noise level is also reduced;

[0095] 4) Decoupling characteristics of the resonant sensor itself: Due to the specific structural design, there is almost no cross-coupling between the various physical quantities sensed by the resonant sensor.

[0096] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A resonant sensor for parallel measurement of multiple physical quantities, characterized in that: The resonant sensor comprises a substrate layer (1) and a device layer (2); the device layer (2) comprises, from the inside to the outside, a circular internal mass block (21), a main vibration ring (22) connected to each other and concentric, a nested multi-layer ring (23) and an external anchoring ring (24); the internal mass block (21) is fixed at the center of the substrate layer (1), and the distance between the internal mass block (21) and the main vibration ring (22) is 3 to 5 micrometers; when the resonant sensor is working, an excitation signal containing the sum of multiple modal resonant frequencies is applied to the resonant sensor, the initial resonant frequency of the resonant sensor under different modes and the resonant frequency after sensing the physical quantity to be measured are measured, and the resonant frequency is analyzed to obtain the value of the physical quantity to be measured.

2. A resonant sensor for parallel measurement of multiple physical quantities according to claim 1, characterized in that: The nested multi-layer ring (23) comprises a plurality of concentric nested rings connected by spokes (26).

3. A resonant sensor for parallel measurement of multiple physical quantities according to claim 2, characterized in that: The nested ring and the main vibration ring (22) have different diameters and widths, and different rigidities and frequencies.

4. A resonant sensor for parallel measurement of multiple physical quantities according to claim 2, characterized in that: The device layer (2) further comprises a support ring (25) which is installed between the nested multilayer ring (23) and the external anchor ring (24) and is connected to the nested multilayer ring (23) and the external anchor ring (24) through spokes (26).

5. The resonant sensor for parallel measurement of multiple physical quantities according to claim 1, characterized in that: The internal mass block (21) is fixed at the center of the substrate layer (1) via a suspension spring (27) and an internal anchor (28).

6. The resonant sensor for parallel measurement of multiple physical quantities according to claim 1, characterized in that: The substrate layer (1) and the device layer (2) are single crystal silicon with anisotropy, and the single crystal silicon with anisotropy has different influence rules on different modes; the modes include second-order wine glass modes and third-order wine glass modes, and the resonant sensor is sensitive to acceleration after receiving an excitation signal of the second-order wine glass mode, and is sensitive to angular velocity after receiving an excitation signal of the third-order wine glass mode.

7. A measurement method using a resonant sensor for parallel measurement of multiple physical quantities as claimed in claim 1, characterized in that: The specific steps include: Step S101, applying an excitation signal to the resonant sensor, wherein the operating frequency of the excitation signal is the sum of the resonant frequencies of multiple modes, and different modes have different sensitivities to different physical quantities to be measured; Step S102, performing frequency modulation sensing analysis on the vibration of the resonant sensor in different modes to obtain the values ​​of different physical quantities to be measured. If there is coupling between the different physical quantities to be measured, executing step S103; Step S103, defining the sensitivity of different modes to different physical quantities to be measured, the product of the variation of different physical quantities to be measured and the corresponding sensitivity is the frequency variation of different modes, solving the equation group to obtain the values ​​of different physical quantities to be measured.

8. The measuring method according to claim 7, characterized in that: The step S101 is specifically as follows: There is an electric potential difference between the internal mass block (21) and the main vibration ring (22); the internal mass block (21) is displaced under the action of a physical quantity to be measured, and the distance between the internal mass block (21) and the main vibration ring (22) changes; an electrostatic force is generated between the internal mass block (21) and the main vibration ring (22), and the stiffness of the main vibration ring (22) changes; and a plurality of modal frequencies change due to the change in stiffness.

9. The measuring method according to claim 7, characterized in that: The physical quantities to be measured include acceleration and angular velocity, and the modes include second-order wine glass mode and third-order wine glass mode; the resonant frequency of the second-order wine glass mode is inversely proportional to the acceleration; the third-order wine glass mode is divided into the first-third-order wine glass mode and the second-third-order wine glass mode according to the main vibration direction, and the frequency difference between the resonant peaks of the first-third-order wine glass mode and the second-third-order wine glass mode is proportional to the angular velocity.

10. The measuring method according to claim 9, characterized in that: The step S103 is specifically as follows: The initial resonant frequency of the second-order wine glass mode is f a0 , the difference between the initial frequencies of the first third-order mode and the second third-order mode is Δf g0 ; The resonant frequency after the second-order wine glass mode changes is f a , the difference in resonant frequency between the first third-order mode and the second third-order mode after the change is Δf g ; When the sensitivity of the resonant frequency to acceleration and angular velocity is linear, the equation system is obtained: f a =f a0 +S aa Δa+S ag DO z , Δf g =Δf g0 +S ga Δa+S gg DO z , Among them, Δa and ΔΩ z are the changes of acceleration and angular velocity, S aa and S ag is the sensitivity of the second-order wine glass mode to acceleration and angular velocity, S ga and S gg are the sensitivities of the third-order wine glass mode to acceleration and angular velocity respectively; solving the equations yields the changes in acceleration and angular velocity.

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