CN-121805159-B - Self-wave locking method and system based on laser photoacoustic spectrum gas detection

CN121805159BCN 121805159 BCN121805159 BCN 121805159BCN-121805159-B

Abstract

The invention provides a self-locking wave method and a self-locking wave system based on laser photoacoustic spectrum gas detection, which relate to the technical field of optical gas sensing, and are characterized in that a first state vector representing the actual performance of a current system is calculated in real time by fusing photoacoustic signals, sound field distribution, thermal deformation and other physical field sensing data, a signal-to-noise ratio, linearity and control energy consumption are simultaneously optimized by using a multi-objective optimization function as criteria, a cooperative control instruction is generated in a rolling way, excitation light modulation parameters and cavity acoustic mode parameters are accurately adjusted, dual dynamic tracking and locking of laser modulation frequency and cavity acoustic resonance frequency are realized, detection sensitivity and signal stability close to a theoretical limit can be automatically and continuously kept all the time when external conditions change, a calculated system nonlinearity index is used as an internal criterion, and a gas concentration value is calculated by intelligently switching a concentration inversion mode, so that seamless, continuous and wide dynamic range measurement from ppb level to percentage level is realized.

Inventors

JIANG YACHAO
LIU XIYIN
ZHOU MI
HUANG YANCHENG
CHEN JIARUI
HUANG MING

Assignees

武汉豪迈光电科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260306

Claims (9)

1. A self-wave locking method based on laser photoacoustic spectroscopy gas detection, the method comprising: Introducing target gas into a multi-resonant coupling intelligent photoacoustic cavity integrated with a piezoelectric actuator array, and acquiring a first photoacoustic signal generated by the action of modulated excitation light and the target gas, a first sound field signal reflecting the spatial distribution of a sound field in the cavity and a first deformation signal reflecting the local thermal deformation of the cavity; Based on the first photoacoustic signal, the first sound field signal and the first deformation signal, a preset digital twin model is combined, a first state vector comprising an effective absorption coefficient, an acousto-optic coupling efficiency factor and a system nonlinearity index is calculated, and the construction of the digital twin model comprises the following steps: in the initialization stage, introducing standard gas into the multi-resonant coupling intelligent photoacoustic cavity to perform parameter scanning, so that the excitation light modulation parameters change in a first range, and the cavity acoustic mode parameters change in a second range; In the parameter scanning process, synchronously acquiring and recording a plurality of groups of scanning parameter combinations and corresponding photoacoustic signals, sound field signals and deformation signals under each group of parameter combinations to form training data pairs; Training by using a training data pair through a machine learning algorithm to obtain a mathematical model capable of mapping the relation among input parameters, a system state and output signals as a digital twin model, wherein the input parameters refer to excitation light modulation parameters and cavity acoustic mode parameters, the system state refers to an effective absorption coefficient of a first state vector, an acousto-optic coupling efficiency factor and a system nonlinearity index, and the output signals refer to a first photoacoustic signal, a first sound field signal and a first deformation signal; Taking the first state vector as input, solving based on a preset multi-objective optimization function, and generating a first control instruction subset for adjusting excitation light modulation parameters and a second control instruction subset for adjusting cavity acoustic mode parameters; And adjusting excitation light modulation parameters according to the first control instruction subset, adjusting cavity acoustic mode parameters according to the second control instruction subset, determining a current concentration inversion mode based on the second photoacoustic signal obtained after adjustment and a system nonlinearity index in the first state vector, wherein the concentration inversion mode comprises a linear mode, a nonlinear transition mode and a depth nonlinearity mode, adopting optimal observed quantity and inversion methods under different nonlinearity degrees, and calculating an output gas concentration value.
2. The self-wave locking method based on laser photoacoustic spectroscopy gas detection of claim 1, wherein the calculating a first state vector comprising an effective absorption coefficient, an acousto-optic coupling efficiency factor, and a system nonlinearity index comprises: performing digital-to-analog conversion on the first deformation signal to obtain a background interference intensity value; Extracting the characteristics of the first photoacoustic signal, the first sound field signal and the first deformation signal which are currently acquired to obtain a first characteristic vector; acquiring excitation light modulation parameters and cavity acoustic mode parameters which are currently used, and inputting the excitation light modulation parameters and the cavity acoustic mode parameters and the first feature vectors serving as input data into a trained digital twin model; And processing the input data based on the digital twin model, and outputting an estimated value of the hidden state of the current system as a first state vector.
3. The self-locking wave method based on laser photoacoustic spectroscopy gas detection of claim 1, wherein the generating a first subset of control instructions for adjusting excitation light modulation parameters and a second subset of control instructions for adjusting cavity acoustic mode parameters comprises: the sub-items of the multi-objective optimization function comprise a concentration prediction error item, a signal quality reciprocal item, a system nonlinearity index item and a control energy consumption item; the digital twin model is taken as an internal prediction model through a prediction control algorithm, a multi-objective optimization function in a time window in the future is minimized, and rolling optimization calculation is carried out; And solving the rolling optimization calculation to obtain a group of future control sequences, and selecting an instruction of a first control period in the future control sequences as a first control instruction subset and a second control instruction subset at the current moment.
4. The self-locking wave method based on laser photoacoustic spectroscopy gas detection of claim 1, wherein the determining the current concentration inversion mode and calculating the output gas concentration value comprises: Setting a first preset threshold value and a second preset threshold value, wherein the second preset threshold value is larger than the first preset threshold value, acquiring a system nonlinearity index in the first state vector and comparing the system nonlinearity index with the preset threshold value; when the system nonlinearity index is lower than a first preset threshold value, judging a linear mode, taking a main frequency amplitude of a second photoacoustic signal subjected to phase-locked amplification processing as a main observation value, and calculating a gas concentration value; When the nonlinearity index of the system is higher than a first preset threshold value but lower than a second preset threshold value, judging the system as a nonlinear transition mode, acquiring the resonance frequency offset of the multi-resonance coupling intelligent optical acoustic cavity, taking the obtained resonance frequency offset as a main observation value after data fusion with the main frequency amplitude of a second optical acoustic signal, and calculating a gas concentration value; When the system nonlinearity index is higher than a second preset threshold, determining a depth nonlinearity mode, acquiring a core frequency parameter for maintaining a cavity resonance tracking state in a second control instruction subset, taking the core frequency parameter as a main observation value of concentration inversion, and calculating a gas concentration value.
5. The self-wave locking method based on laser photoacoustic spectroscopy gas detection of claim 2, wherein the calculating of the effective absorption coefficient comprises: After digital-to-analog conversion is carried out on the first deformation signal, a scalar value representing a non-uniform thermal deformation distribution gradient of the surface of the cavity is obtained and is recorded as a background interference intensity value; Converting the background interference intensity value into a corresponding equivalent background absorption signal amplitude value; subtracting the equivalent background absorption signal amplitude from the total absorption signal amplitude obtained by performing spectrum analysis on the first photoacoustic signal, wherein the obtained net signal amplitude is used for finally calculating an effective absorption coefficient.
6. The self-locking wave method based on laser photoacoustic spectroscopy gas detection of claim 1, wherein the adjusting the excitation light modulation parameters according to the first subset of control instructions comprises: Analyzing the contained target laser wavelength offset value, the target laser modulation frequency value and the target laser modulation depth value from the first control instruction subset; and adjusting the central wavelength of the output laser according to the target laser wavelength offset value, and adjusting the modulation frequency and the modulation depth of the laser according to the target laser modulation frequency value and the target laser modulation depth value.
7. The self-wave locking method based on laser photoacoustic spectroscopy gas detection of claim 6, wherein the adjusting the cavity acoustic mode parameter according to the second subset of control instructions comprises: The second control instruction subset comprises a group of multipath control signal parameters for driving a plurality of actuating units on the cavity, and each path of control signal parameters comprises driving amplitude, driving phase and driving frequency; generating corresponding multipath high-voltage driving signals according to the multipath control signal parameters, and respectively applying the multipath high-voltage driving signals to corresponding actuating units; The excitation cavity generates axial, radial and mixed acoustic resonance modes by setting different driving phase combinations, and the resonance frequency of the selected acoustic resonance modes is tuned by setting the driving frequency.
8. The self-wave locking method based on laser photoacoustic spectroscopy gas detection of claim 1, further comprising: In the continuous operation process of the system, periodically storing the acquired first photoacoustic signal, second photoacoustic signal, first deformation signal, first control instruction subset, second control instruction subset, excitation light modulation parameter, cavity acoustic mode parameter and first state vector as data samples into a rolling history database; Calculating average errors between the predicted signals and the real signals output by the digital twin model in all recent data samples at regular intervals; when the average error exceeds a preset error threshold, triggering an updating process, and performing one-round incremental learning and fine adjustment on the parameters of the digital twin model by using the data sample of the latest time in the rolling history database.
9. A self-locking wave system based on laser photoacoustic spectroscopy gas detection for implementing a self-locking wave method based on laser photoacoustic spectroscopy gas detection according to any one of claims 1 to 8, characterized in that the system comprises: the tunable laser excitation module is used for generating detection laser with adjustable wavelength and subjected to compound modulation; the multi-resonance coupling intelligent optical-acoustic cavity module is used for absorbing target gas and generating acoustic waves; the multi-physical-field fusion sensing module is used for acquiring a first photoacoustic signal, a first sound field signal and a first deformation signal which are generated by the action of the modulated excitation light and the target gas; The signal processing and state observing module is used for calculating a first state vector by combining a preset digital twin model based on the first photoacoustic signal, the first sound field signal and the first deformation signal; the multi-objective optimization decision and control module is used for taking the first state vector as input, solving based on a preset multi-objective optimization function, generating a first control instruction subset for adjusting the tunable laser excitation module and a second control instruction subset for adjusting the multi-resonant coupling intelligent photo-acoustic cavity module, determining a current concentration inversion mode based on the second photo-acoustic signal obtained after adjustment and a system nonlinearity index in the first state vector, and calculating an output gas concentration value.

Description

Self-wave locking method and system based on laser photoacoustic spectrum gas detection Technical Field The invention relates to the technical field of optical gas sensing, in particular to a self-wave locking method and system based on laser photoacoustic spectroscopy gas detection. Background The laser photoacoustic spectroscopy technology has become an important method for trace gas detection due to high sensitivity, wide dynamic range and good gas selectivity, and the basic principle is that gas molecules are excited by utilizing modulated laser with specific wavelength, periodic thermal disturbance is generated through non-radiative relaxation, and then detectable acoustic wave signals are excited, and when the laser photoacoustic spectroscopy technology is used, a theoretical optimal working point is determined for static optimization through precisely processing a fixed cavity structure, selecting a quartz tuning fork with specific resonant frequency or presetting laser modulation parameters. When the system is actually used, firstly, the acoustic resonance frequency of the photoacoustic cavity drifts along with the changes of the ambient temperature, the pressure and the gas components, and the laser modulation frequency is usually fixed, so that the system is easy to detune and the signal amplitude is seriously attenuated, secondly, when the gas concentration spans multiple orders of magnitude, the system response is nonlinear, the traditional photoacoustic signal can be saturated or even attenuated under high concentration, the prior art relies on manual switching of a measuring range or diluting a sample, continuous monitoring cannot be realized, and finally, invalid photo-thermal signals generated by non-target gas absorption such as window adsorption, dust scattering and the like exist in the detection process and are mixed with target signals, so that the selectivity and accuracy of detection are reduced. The existing improvement scheme focuses on optimization of a single link, such as improving the stability of a light source, designing a high-order resonant cavity or adopting differential noise suppression, and lacks an intelligent closed-loop control mechanism capable of sensing the global state of the system in real time and cooperatively regulating and controlling a plurality of degrees of freedom, so that the stability, the dynamic range and the anti-interference capability of the system under complex working conditions are insufficient. In summary, the following technical problems exist in the prior art when in use: Firstly, the existing laser photoacoustic spectrum system based on static working point optimization cannot adapt to system state drift caused by environmental fluctuation and gas concentration change in actual detection, so that continuous mismatch among laser excitation efficiency, acoustic resonance and signal detection is caused, and the system cannot maintain peak sensitivity and optimal signal to noise ratio in dynamic change; Secondly, the traditional photoacoustic spectroscopy technology faces the bottleneck of signal saturation and nonlinearity during high-concentration gas detection, and meanwhile lacks an effective means to distinguish target gas absorption from non-target interference, such as window heating, water vapor cross absorption and the like, so that the dynamic range of the traditional photoacoustic spectroscopy technology is limited, and the measurement accuracy and selectivity in a complex gas mixture or a severe environment are reduced. Disclosure of Invention The invention aims at realizing the technical scheme that the self-wave-locking method and the system based on the laser photoacoustic spectrum gas detection comprise the following steps: Introducing target gas into a multi-resonant coupling intelligent photoacoustic cavity integrated with a piezoelectric actuator array, and acquiring a first photoacoustic signal, a first sound field signal and a first deformation signal which are generated by the action of modulated excitation light and the target gas; Based on the first photoacoustic signal, the first sound field signal and the first deformation signal, a preset digital twin model is combined, and a first state vector comprising an effective absorption coefficient, an acousto-optic coupling efficiency factor and a system nonlinearity index is calculated; Taking the first state vector as input, solving based on a preset multi-objective optimization function, and generating a first control instruction subset for adjusting excitation light modulation parameters and a second control instruction subset for adjusting cavity acoustic mode parameters; And adjusting excitation light modulation parameters according to the first control instruction subset, adjusting cavity acoustic mode parameters according to the second control instruction subset, determining a current concentration inversion mode based on the second photoacoustic signal obtained after