CN107976274A - A pressure detection device and detection method based on synchronous resonance - Google Patents

Abstract

The invention relates to a pressure detection device and a detection method based on synchronous resonance, belonging to pressure detection devices. It includes 2N resonant units, an upper base and a lower base, and each resonant unit is installed between the edge base and the central base. The present invention uses the inverse piezoelectric effect of the piezoelectric sheet arranged on the fixed beam to drive the beam to oscillate. When When the vibration frequency approaches the natural frequency of the fixed-supported beam, the fixed-supported beam and the cantilever beam resonate synchronously through the action of the coupling part, achieving frequency multiplication. The error control of N sets of data is carried out to improve the detection sensitivity and precision. The resonant frequency of the cantilever beam is detected under the closed-loop feedback control system, and the change of the resonant frequency represents the magnitude of the pressure to be measured, which has the advantages of high sensitivity, high precision and high resolution.

Description

A pressure detection device and detection method based on synchronous resonance

technical field

The invention relates to a pressure detection device, in particular to a pressure detection device based on synchronous resonance.

Background technique

Pressure detection devices currently on the market are mainly resonant, piezoresistive and capacitive. The output signals of the latter two are analog quantities, which need to be processed by a high-precision adjustment circuit. The disadvantage of this processing method is that it will lead to a decrease in measurement accuracy. The resonant pressure detection device uses the pressure change to change the resonant frequency of the beam, so that the pressure can be measured indirectly by measuring the change of the frequency, which can improve the measurement accuracy. Since the output of the resonant pressure detection device is a quasi-digital signal, it has the characteristics of high measurement sensitivity, high precision, high resolution, and strong anti-interference ability. It has the advantage of long-distance transmission without reducing its accuracy, and is more suitable for pressure measurement. Perform high-precision inspection.

Micro pressure sensors manufactured by MEMS technology, precision machining or other precision machining methods have the advantages of small size, light weight, high sensitivity, and high reliability, and have become a strategic research field worldwide. At present, the research on MEMS resonant pressure sensors at home and abroad is mainly silicon micro-resonant pressure sensors. The elastic elements and sensitive elements of the sensors are made of silicon materials and processed by silicon technology. For example, the patent of the Institute of Electronics of the Chinese Academy of Sciences "a beam-membrane split structure resonant beam pressure sensor" and the invention patent of Xiamen University "a fully symmetrical silicon micro-resonant pressure sensor" both use a vibration unit containing a vibration beam.

Contents of the invention

The invention provides a pressure detection device and detection method based on synchronous resonance, aiming to improve the measurement accuracy, sensitivity and resolution of the existing pressure sensor.

The technical solution adopted by the present invention is: the upper surface of the upper substrate is etched with an upper groove, and an upper single island is formed in the center; the lower groove is etched on the back of the upper substrate, and a lower single island is formed in the center, and 2N islands are evenly distributed inside the upper groove. Edge base, N is a positive integer; the center of the upper groove and the lower groove are located on the axis of the upper base, the upper part of the lower base is in contact with the lower part of the lower single island, and the lower base and the upper base are fixedly connected together, 2N The coupling part of the resonant unit is fixedly connected to 2N edge bases, the fixed support beam is fixedly connected to the side of the center base, and the bottom of the center base is in contact with the top of the upper single island.

The upper base and the lower base have the same dimensions and are cylindrical.

A groove is etched on the front side of the lower base, the groove is sealed and connected with the lower single island, and a pressure hole is processed in the center of the groove.

The structure of the resonant unit is: the cantilever beam and the fixed beam are respectively connected to the coupling part, and the piezoelectric sheet 1 and the piezoelectric sheet 2 are installed on the fixed ends of the fixed beam and the cantilever beam respectively.

A pressure detection method based on synchronous resonance, comprising the following steps:

(1) Before detecting the pressure, use an electric signal to excite the fixed beam to resonate, then apply the pressure or gas to the center of the lower base, and remove the pressure or gas after the signal is stable;

(2) Under the action of pressure, the film on the upper base moves upward, thereby forcing the central base to move upward, changing the natural frequency of the fixed beam, and picking up the amplified frequency signal on the cantilever beam and outputting it;

(3) Calculate the average value of all the data within the range of the error condition in the N sets of data, and use it as the final frequency output signal;

(4) Determine the pressure to be measured by the relationship between the output frequency and the pressure.

The advantage of the present invention is that: adopting a resonant unit to include two vibrating beams coupled together, using the synchronous resonance effect, the output signals of the coupled fixed beam and the cantilever beam will be multiplied according to the frequency ratio of the two, so that the output Greater frequency increases sensitivity and resolution. In addition, in the 2N resonant units arranged symmetrically in the center, the error comparison of N sets of data and the superposition and amplification of unit signals can improve the detection accuracy. The upper and lower substrates produced by MEMS technology, precision machining or other precision machining methods have excellent characteristics such as good dimensional accuracy, high reliability, and low cost. The design of bonding bosses on the front of the substrate and single islands on the back can improve linearity. Combining the advantages of the two, the resonant pressure sensor chip based on the novel synchronous resonance structure designed and produced by the present invention has the characteristics of high sensitivity, high precision, high resolution, and good linearity.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic diagram of a half-section structure of the present invention for detecting contact pressure;

Fig. 3 is a schematic diagram of a half-section structure for detecting gas pressure in the present invention;

Fig. 4 is a structural schematic diagram of a resonance unit of the present invention;

Fig. 5 is a structural schematic diagram of eight resonant units in the present invention;

Fig. 6 is a schematic structural diagram of four resonance units in the present invention.

Detailed ways

Referring to Fig. 1 and Fig. 2, an upper groove 102 is etched on the front of the upper substrate 1, and an upper single island 104 is formed in the center; a lower groove 103 is etched on the back of the upper substrate 1, and a lower single island 105 is formed in the center, and the upper groove 2N edge bases 101 are evenly distributed on the inner side, and N is a positive integer; the centers of the upper groove and the lower groove are located on the axis of the upper base, the upper part of the lower base 4 is in contact with the lower part of the lower single island 105, and the lower base 4 is in contact with the upper base. The surroundings of the base 1 are fixedly connected together, the coupling parts 201 of the 2N resonance units 2 are respectively fixedly connected to the 2N edge bases 101, the fixed support beams 203 are respectively fixedly connected to the side of the central base 3, and the bottom of the central base 3 is connected to the upper single Contact above Island 104;

The upper base 1 and the lower base 4 have the same dimensions and are cylindrical.

Referring to Fig. 3, a groove 401 is etched on the front side of the lower substrate 4, and the groove 401 is in sealing connection with the lower single island 105, and a pressure hole 402 is processed in the center of the groove; the pressure hole 402 is communicated with the atmosphere to form a gauge pressure detection device, or communicate with another measured gas source to form a differential pressure detection device.

Referring to Fig. 4, the structure of the resonant unit 2 is: the cantilever beam 202 and the fixed beam 203 are respectively connected to the coupling part 201, and the piezoelectric sheet one 204 and the piezoelectric sheet two 205 are installed on the fixed beam 203 and the cantilever beam 202 respectively. the fixed end.

The external pressure to be measured does not directly act on the resonant mechanism, but acts on the central base 3 through the lower single island 105 and the upper single island 104, thereby changing the stiffness of the resonant unit, changing its resonant frequency, and indirectly measuring the pressure to be measured, when When measuring the gas pressure, the lower single island 105 is subjected to an upward force of F=p·A _hole , and each rectangular beam is uniformly subjected to a force of F _N =F/N.

When working, the resonant unit is first excited to resonate, and then the pressure is applied or the gas to be measured is introduced. The pressure will force the lower single island and the upper single island to move upward, and press the central base 3 upward, thereby driving the fixed support beam 203 to deform; due to the deformation The axial mechanical stress changes, which in turn affects the natural frequency of the beam. It is assumed that the axial stress generated by the fixed beam with rectangular cross-section is approximately linearly proportional to _FN , that is:

σ＝δ·F _N

In the formula, σ is the axial stress of the rectangular cross-section beam, and δ is the linear coefficient;

when σ=0

The first-order natural frequency of the fixed beam is:

When σ≠0

where the critical Euler equation E is the elastic modulus of the material, ρ is the bulk density of the beam, a, b, and c are the length, width, and height of the rectangular cross-section beam, respectively.

The fixed-supported beam and the cantilever beam are designed based on the principle of synchronous resonance. If the natural frequencies of the fixed-supported beam and the cantilever beam are f ₁ and f ₂ , they satisfy:

The inverse piezoelectric effect of the piezoelectric sheet arranged on the fixed beam is used to drive the silicon beam to oscillate. When the vibration frequency approaches the natural frequency of the fixed beam, resonance occurs. Through the action of the coupling part, the fixed beam and the cantilever beam occur Synchronous resonance, the first-order natural frequency ratio of the fixed beam and the cantilever beam is m:n, m and n are integers, n>m, so as to achieve frequency multiplication, output the amplified frequency, and improve the sensitivity. The output frequency is:

The final output frequency _f2 has an approximately linear relationship with the pressure p, namely:

N groups of resonant units are symmetrically distributed in the center, and the errors of the N groups are compared. If the data of multiple groups differs greatly, it means that the chip is damaged and the data is wrong; otherwise, the data is correct and the measurement is accurate;

Referring to Fig. 5 and Fig. 6, the number of resonant units on the device of the present invention is 2N, which is variable, wherein N is an integer greater than 1, N=4 in Fig. 5, and N=2 in Fig. 6 .

The shape of each beam of the uniformly distributed resonant unit is not fixed, and may be strip-shaped or S-shaped.

A pressure detection method based on synchronous resonance, comprising the following steps:

(1) Before detecting the pressure, use an electric signal to excite the fixed beam to resonate, then apply the pressure or gas to the center of the lower base, and remove the pressure or gas after the signal is stable;

(2) Under the action of pressure, the film on the upper base moves upward, thereby forcing the central base to move upward, changing the natural frequency of the fixed beam, and picking up the amplified frequency signal on the cantilever beam and outputting it;

(3) Calculate the average value of all the data within the range of the error condition in the N sets of data, and use it as the final frequency output signal;

(4) Determine the pressure to be measured by the relationship between the output frequency and the pressure.

Claims (6)

1. A pressure detection device based on synchronous resonance, characterized in that: an upper groove is etched on the front side of the upper substrate to form an upper single island in the center; a lower groove is etched on the back side of the upper substrate to form a lower single island in the center, 2N edge bases are evenly distributed inside the upper groove, and N is a positive integer; the centers of the upper groove and the lower groove are both located on the axis of the upper base, and the top of the lower base is in contact with the bottom of the lower single island, and the lower base is in contact with the upper base. The surroundings are fixedly connected together, the coupling parts of the 2N resonant units are respectively fixedly connected with the 2N edge bases, the fixed support beams are respectively fixedly connected with the sides of the center base, and the bottom of the center base is in contact with the top of the upper single island. 2 . The pressure detection device based on synchronous resonance according to claim 1 , wherein the upper base and the lower base have the same external dimensions and are cylindrical. 3 . 3. A pressure detection device based on synchronous resonance according to claim 1 or 2, characterized in that: a groove is etched on the front side of the lower substrate, the groove is sealed with the lower single island, and the center of the groove Machine a pressure hole. 4. A kind of pressure detection device based on synchronous resonance according to claim 1 or 2, characterized in that: the structure of the resonance unit is: the cantilever beam and the fixed beam are respectively connected to the coupling part, the piezoelectric plate and the The second piezoelectric sheet is installed on the fixed end of the fixed support beam and the cantilever beam respectively. 5. A pressure detection device based on synchronous resonance according to claim 3, characterized in that: the structure of the resonance unit is: the cantilever beam and the fixed beam are respectively connected to the coupling part, the piezoelectric sheet one and the piezoelectric The second piece is installed on the fixed ends of the fixed support beam and the cantilever beam respectively. 6. A pressure detection method based on synchronous resonance, characterized in that, comprising the following steps: (1) Before detecting the pressure, use an electric signal to excite the fixed beam to resonate, then apply the pressure or gas to the center of the lower base, and remove the pressure or gas after the signal is stable; (2) Under the action of pressure, the film on the upper base moves upward, thereby forcing the central base to move upward, changing the natural frequency of the fixed beam, and picking up the amplified frequency signal on the cantilever beam and outputting it; (3) Calculate the average value of all the data within the range of the error condition in the N sets of data, and use it as the final frequency output signal; (4) Determine the pressure to be measured by the relationship between the output frequency and the pressure.