CN-121830824-B - MEMS sensor-based gas thermophysical parameter identification method and system

Abstract

The invention relates to the technical field of gas detection and thermophysical analysis, in particular to a gas thermophysical parameter identification method and system based on an MEMS sensor. The method comprises the steps of applying multi-frequency alternating current excitation current to a heating element to enable the heating element to generate Joule heat fluctuation of twice reference frequency and cause resistance same-frequency fluctuation, extracting a frequency-tripled output voltage signal through a lock amplification circuit, decomposing the frequency-tripled output voltage signal into in-phase and quadrature components through phase-sensitive detection, further calculating complex temperature rise and constructing a complex thermal impedance model, calculating a heat conduction coefficient based on the slope of a real part signal of the complex thermal impedance model along with frequency change, extracting thermal diffusivity through imaginary part and phase delay, and finally decoupling and outputting volume specific heat capacity by combining a correlation model. According to the invention, high-precision decoupling of multidimensional thermal parameters is realized through frequency domain impedance analysis, drift interference is effectively filtered, and the difficult problem that complex component gas is difficult to accurately identify under microscale is solved.

Inventors

• DONG SHENGLONG
• FU ZIJIAN
• LI LONG
• DUAN SUOXING

Assignees

• 祎智量芯(江苏)电子科技有限公司

Dates

Publication Date

20260512

Application Date

20260312

Claims (5)

1. 1. The gas thermophysical parameter identification method based on the MEMS sensor is characterized by comprising the following steps of: applying a multi-frequency alternating excitation current to a heating element of the MEMS sensor, so that the heating element generates Joule heat fluctuation with double reference frequency, and the resistance value of the heating element generates common-frequency fluctuation; The method comprises the steps of detecting and extracting frequency triples output voltage signals generated at two ends of a heating element in real time through a lock amplification circuit, decomposing the frequency triples output voltage signals into an in-phase component signal with the same phase as an alternating excitation current and a quadrature component signal with phase deviation with the alternating excitation current by utilizing a phase sensitive detection technology, calculating complex temperature rise of the heating element according to the in-phase component signal and the quadrature component signal, constructing a complex thermal impedance model of gas to be detected by combining with the joule thermal fluctuation, calculating complex temperature rise amplitude of the heating element under the condition of double reference frequency and phase lag relative to the alternating excitation current by utilizing the in-phase component signal, the quadrature component signal and the resistance temperature coefficient of the heating element, calculating joule thermal fluctuation power generated by the heating element according to an effective value of the alternating excitation current and a resistance base value of the heating element, defining the complex thermal fluctuation power as a dynamic thermal flow vector input into a gas environment to be detected, and carrying out complex operation on the complex thermal impedance model by utilizing the complex temperature rise and the dynamic thermal flow vector; The method comprises the steps of calculating the heat conductivity coefficient of the gas to be measured based on the slope of the real part signal of the complex thermal impedance model changing along with the logarithm of the reference frequency, extracting the thermal diffusivity of the gas to be measured based on the imaginary part signal of the complex thermal impedance model and the phase delay, wherein the step of calculating the heat conductivity coefficient and the thermal diffusivity comprises the steps of extracting the numerical value of the real part signal in the complex thermal impedance model in a preset frequency section, establishing the linear mapping relation between the real part signal and the reference frequency, calculating the slope of the linear mapping relation, combining the geometric characteristic parameter of the heating element, inverting to obtain the heat conductivity coefficient of the gas to be measured, and utilizing the imaginary part signal of the complex thermal impedance model to combine the heat conductivity coefficient, and obtaining the thermal diffusivity of the gas to be measured through intercept fitting calculation; The method comprises the steps of utilizing the heat conductivity coefficient and the heat diffusivity to be combined with a correlation model, decoupling and outputting the volume specific heat capacity of the gas to be tested, quantitatively analyzing the component proportion of the mixed gas, and outputting the volume specific heat capacity, wherein a thermal parameter characteristic matrix of the gas to be tested is established according to a physical correlation formula between the heat diffusivity and the heat conductivity coefficient as well as the volume specific heat capacity, the physical correlation formula meets the mathematical relation that the heat diffusivity is equal to the heat conductivity coefficient divided by the volume specific heat capacity, the calculated heat conductivity coefficient and the extracted heat diffusivity are substituted into the physical correlation formula, and the volume specific heat capacity of the gas to be tested is decoupled through numerical division operation.
2. 2. The method for identifying the gas thermophysical property parameters based on the MEMS sensor according to claim 1, wherein the step of applying the multi-frequency alternating current excitation current comprises the steps of generating n groups of reference sine wave signals with different preset frequencies by utilizing a digital frequency synthesizer, linearly weighting and superposing the n groups of reference sine wave signals to synthesize a composite signal containing n target reference frequency components, inputting the composite signal into a constant current driving circuit, outputting the multi-frequency alternating current excitation current to the heating element through closed loop control, adjusting the weight of each reference frequency in the multi-frequency alternating current excitation current according to the thermal response feedback of the gas to be detected, so that the resistance value generates the same-frequency fluctuation containing n double reference frequency components, and generates the triple-frequency output voltage signal containing the three-frequency components corresponding to each reference frequency.
3. 3. The method for identifying the gas thermophysical parameter based on the MEMS sensor according to claim 1, wherein the specific step of generating the frequency-tripled output voltage signal comprises the steps of enabling the heating element to generate temperature fluctuation containing twice as much as each reference frequency component by the multi-frequency alternating current excitation current, linearly modulating the temperature fluctuation into a dynamic resistance signal containing twice as much as each reference frequency component based on a resistance temperature coefficient, enabling the multi-frequency alternating current excitation current with the frequency being the reference frequency and the dynamic resistance signal with the frequency being twice as much as the reference frequency to interact at two ends of the heating element according to ohm law, generating an original voltage signal containing three times as much as the reference frequency component, processing the original voltage signal through the lock-in amplifying circuit, filtering the reference frequency component, and extracting the frequency-tripled output voltage signal representing the thermophysical characteristic of the gas to be detected.
4. 4. The method for identifying the gas thermophysical parameter based on the MEMS sensor according to claim 1, wherein the specific steps of extracting and decomposing to obtain an in-phase component signal and a quadrature component signal comprise the steps of generating a first reference sinusoidal signal which is the same frequency and in-phase with a triple reference frequency and a second reference sinusoidal signal which has a 90-degree phase difference with the first reference sinusoidal signal by utilizing a digital frequency synthesizer, multiplying a triple frequency output voltage signal with the first reference sinusoidal signal and the second reference sinusoidal signal respectively by utilizing a phase-sensitive detection technology, modulating a target frequency signal to a zero frequency band, generating a mixed signal containing twice the triple reference frequency, filtering the mixed signal by utilizing a low-pass filter, filtering a high-frequency component, and extracting the in-phase component signal representing the real part characteristic of the triple frequency output voltage signal and the quadrature component signal representing the imaginary part characteristic of the output voltage signal in real time.
5. 5. The gas thermophysical property parameter identification system based on the MEMS sensor is characterized by comprising: The driving module is used for applying multi-frequency alternating current excitation current to a heating element of the MEMS sensor, so that the heating element generates joule heat fluctuation with double reference frequency, and the resistance value of the heating element generates common-frequency fluctuation; The extraction module is used for detecting and extracting frequency tripled output voltage signals generated at two ends of the heating element in real time through a lock amplification circuit, decomposing the frequency tripled output voltage signals into an in-phase component signal which is in phase with the alternating excitation current and a quadrature component signal which has phase deviation with the alternating excitation current by utilizing a phase sensitive detection technology, calculating complex temperature rise of the heating element according to the in-phase component signal and the quadrature component signal, constructing a complex thermal impedance model of gas to be detected by combining the joule thermal fluctuation, calculating complex temperature rise amplitude of the heating element under double reference frequency and phase lag relative to the alternating excitation current by utilizing the in-phase component signal, the quadrature component signal and the resistance temperature coefficient of the heating element, calculating joule thermal fluctuation power generated by the heating element according to the effective value of the alternating excitation current and the resistance base value of the heating element, and defining the complex temperature rise amplitude and the dynamic thermal flow vector as dynamic thermal flow vector which are input into the gas environment to be detected, and obtaining the complex thermal impedance model; The calculation module is used for calculating the heat conductivity coefficient of the gas to be measured based on the slope of the real part signal of the complex thermal impedance model along with the logarithmic change of the reference frequency; the method comprises the steps of extracting the numerical value of a real part signal in a complex thermal impedance model in a preset frequency band, establishing a linear mapping relation between the real part signal and a reference frequency, calculating the slope of the linear mapping relation, combining the geometric characteristic parameters of a heating element, inverting to obtain the thermal diffusivity of the gas to be detected, and calculating and extracting the thermal diffusivity of the gas to be detected through intercept fitting calculation by utilizing the imaginary part signal of the complex thermal impedance model and combining the thermal diffusivity; the analysis module is used for decoupling and outputting the volume specific heat capacity of the gas to be tested by utilizing the heat conductivity coefficient and the heat diffusivity and combining a correlation model, and quantitatively analyzing the component proportion of the mixed gas, wherein the step of outputting the volume specific heat capacity comprises the steps of establishing a thermal parameter characteristic matrix of the gas to be tested according to a physical correlation formula between the heat diffusivity and the heat conductivity coefficient as well as the volume specific heat capacity, wherein the physical correlation formula satisfies the mathematical relation that the heat diffusivity is equal to the heat conductivity coefficient divided by the volume specific heat capacity, substituting the calculated heat conductivity coefficient and the extracted heat diffusivity into the physical correlation formula, and decoupling the volume specific heat capacity of the gas to be tested through numerical division operation.

Description

MEMS sensor-based gas thermophysical parameter identification method and system Technical Field The invention relates to the technical field of gas detection and thermophysical analysis, in particular to a gas thermophysical parameter identification method and system based on an MEMS sensor. Background Along with the development of industrial Internet of things and hydrogen energy economy, the accurate identification of thermophysical parameters of mixed gas is realized in a complex environment, and the method has become a key technical requirement for energy safety monitoring and quantitative analysis of gas components. Traditional gas detection mainly relies on chemical sensing technology, but drift and poisoning phenomena are easy to occur in a high-temperature and high-humidity environment. At present, the MEMS-based thermal conductivity sensor realizes physical detection by measuring the intrinsic thermal parameters of gas, and has better long-term stability. However, most of the existing identification methods adopt a steady-state direct current driving method or a simple transient pulse method, only a single heat conductivity coefficient can be obtained, and effective stripping of multiple physical parameters in complex background gas is difficult to realize. When facing gas components (such as carbon dioxide and argon) or multicomponent mixed gases (such as hydrogen-mixed natural gas) with similar heat conductivity coefficients, the prior art lacks decoupling capability of multidimensional physical quantity, so that identification precision is insufficient, cross sensitivity is serious, and the requirements of industrial-level high-precision qualitative and quantitative analysis cannot be met. The invention aims to solve the technical problem of improving synchronous identification precision and decoupling capability of a plurality of intrinsic thermal parameters such as heat conductivity coefficient, thermal diffusivity, volume specific heat capacity and the like in a multi-component mixed gas environment. Therefore, a gas thermophysical parameter identification method and a gas thermophysical parameter identification system based on MEMS sensors are provided. Disclosure of Invention The invention aims to provide a gas thermophysical parameter identification method and a gas thermophysical parameter identification system based on an MEMS sensor, which realize high-precision decoupling of multidimensional thermal parameters through frequency domain impedance analysis of frequency triplex and solve the problem of precise identification of complex component gases. In order to achieve the above purpose, the present invention provides the following technical solutions: A gas thermophysical parameter identification method based on an MEMS sensor comprises the following steps: applying a multi-frequency alternating excitation current to a heating element of the MEMS sensor, so that the heating element generates Joule heat fluctuation with double reference frequency, and the resistance value of the heating element generates common-frequency fluctuation; The method comprises the steps of detecting and extracting frequency tripling output voltage signals generated at two ends of a heating element in real time through a lock amplification circuit, decomposing the frequency tripling output voltage signals into an in-phase component signal with the same phase as an alternating current excitation current and a quadrature component signal with phase deviation with the alternating current excitation current by utilizing a phase-sensitive detection technology, calculating complex temperature rise of the heating element according to the in-phase component signal and the quadrature component signal, and constructing a complex thermal impedance model of gas to be detected by combining with the joule thermal fluctuation; calculating the heat conductivity coefficient of the gas to be measured based on the slope of the real part signal of the complex thermal impedance model along with the logarithmic change of the reference frequency; And decoupling and outputting the volumetric specific heat capacity of the gas to be detected by utilizing the heat conductivity coefficient and the thermal diffusivity and combining a correlation model, and quantitatively analyzing the component proportion of the mixed gas. Preferably, the step of applying the multi-frequency alternating current excitation current comprises the steps of generating n groups of reference sine wave signals with different preset frequencies by utilizing a digital frequency synthesizer, linearly weighting and superposing the n groups of reference sine wave signals to synthesize a composite signal containing n target reference frequency components, inputting the composite signal into a constant current driving circuit, outputting the multi-frequency alternating current excitation current to the heating element through closed loop control, adjusting the weight of