Method for on-line monitoring of multi-component gas concentration by optical cavity ring-down spectroscopy

Abstract

The application discloses a cavity ring-down spectroscopy multi-component gas concentration online monitoring method, and belongs to the technical field of gas monitoring; based on the light path propagation direction, a target optical cavity is divided into a front end layer, a core layer and a tail end layer, and a plurality of cavity ring-down spectrometers synchronously collect decay signals of each layer at a unified data collection time point to construct a hierarchical cavity ring-down matrix; a standard gas with a preset concentration is introduced at a calibration time point, initial values of gas concentrations of each layer are calculated, and a hierarchical concentration error matrix is constructed; envelope fusion processing is performed on the decay signals of each layer to obtain fused decay signals, and the fused decay signals are uniformly corrected based on a hierarchical error offset result; hierarchical equivalent gas concentrations of each layer are calculated, and a comprehensive concentration of multi-component gas is obtained through hierarchical collaborative weighting as an online monitoring result output, which can effectively suppress the influence of systematic errors on the monitoring result, and improve the stability, consistency and engineering applicability of multi-component gas online monitoring.

Description

Technical Field

[0001] This invention relates to the field of gas monitoring technology, specifically to a method for online monitoring of multi-component gas concentrations using cavity ring-down spectroscopy. Background Technology

[0002] Cavity ring-down spectroscopy (CRDS), as a highly sensitive absorption spectroscopy detection technique, has been widely researched and applied in environmental monitoring, industrial process control, atmospheric chemical analysis, and safety production due to its advantages such as insensitivity to light source intensity fluctuations, long effective optical path, and low detection limit. With the increasing demand for multi-component gas collaborative monitoring, related technologies are gradually developing from single-component, offline detection to multi-component, continuous online monitoring. Existing research mainly focuses on the design of high-reflectivity optical cavity structures, optimization of ring-down time inversion models, and multi-wavelength scanning strategies. By improving temporal and spectral resolution, simultaneous identification and quantitative analysis of multiple gas components can be achieved. Simultaneously, to adapt to long-term operation requirements under complex conditions, some technologies introduce parallel deployment of multiple cavity ring-down spectrometers, periodic calibration, and temperature drift compensation mechanisms to improve system stability and engineering applicability. However, with the expansion of optical cavity size, non-ideal distribution of optical paths, and the collaborative operation of multiple instruments, the non-uniformity of the spatial distribution of gas within the optical cavity has gradually become an important factor affecting measurement accuracy. The traditional modeling method that treats the optical cavity as a single uniform detection zone is no longer sufficient to meet the development needs of high-precision, multi-component online monitoring.

[0003] From the perspective of existing technologies, most cavity ring-down spectroscopy gas monitoring methods still rely on the overall cavity ring-down signal or a single ring-down time parameter as the basis for concentration inversion, assuming a uniform gas concentration distribution within the optical path propagation range and ignoring the differences in gas renewal rate, flow field state, and optical loss between the front, core, and rear regions of the cavity. Furthermore, existing multi-component detection schemes often depend on unified calibration parameters or single-point calibration results, making it difficult to effectively eliminate systematic deviations between different optical round-trip intervals and between different instruments, easily leading to accumulated errors under long-term online operation. While some technologies introduce multi-instrument averaging or simple signal fusion strategies, they lack error modeling and hedging mechanisms for hierarchical differences, resulting in limited stability and consistency of the overall concentration of multi-component gases under complex operating conditions. These shortcomings are further amplified in applications requiring high sensitivity, high consistency, and real-time performance, hindering the in-depth application of cavity ring-down spectroscopy in refined, multi-level gas monitoring. Summary of the Invention

[0004] The purpose of this invention is to provide an online monitoring method for the concentration of multi-component gases in an optical cavity ring-down spectrum, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for online monitoring of multi-component gas concentration using cavity ring-down spectroscopy, comprising the following steps: Step S1: Based on the optical path propagation direction, the target cavity is divided into a front-end layer, a core layer, and a tail-end layer; based on the ring-down signals of the front-end layer, core layer, and tail-end layer acquired by the cavity ring-down spectrometer at the data acquisition time point, a cavity ring-down matrix is ​​constructed at the data acquisition time point; Step S2: A standard gas of a preset concentration is introduced, and the standard ring-down signals of the front-end layer, core layer, and tail-end layer are simultaneously acquired using the cavity ring-down spectrometer to calculate the initial gas concentration value and construct a hierarchical concentration error vector; Step S3: A front-end layer ring-down signal set, a core layer ring-down signal set, and a tail-end layer ring-down signal set are constructed; the upper envelope values ​​of the front-end layer, core layer, and tail-end layer are obtained. Step S4: Obtain the layer concentration error vector of all optical cavity ring-down spectrometers and construct the self-calibration concentration error matrix; calculate the concentration offset of each layer and construct the layer error offset matrix; based on the fusion layer ring-down matrix and the layer error offset matrix, perform consistency correction on the fusion ring-down signals of the front-end layer, core layer and tail-end layer; Step S5: based on the consistent corrected layer ring-down signals, calculate the layer equivalent gas concentration and multi-component gas comprehensive concentration of each layer at the data acquisition time point; output the multi-component gas comprehensive concentration at the data acquisition time point as the online monitoring result at the data acquisition time point.

[0006] As a preferred embodiment of the online monitoring method for multi-component gas concentration in cavity ring-down spectroscopy described in this invention, the optical path propagation direction in the target optical cavity is obtained, and based on the optical path propagation direction, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer, wherein the front-end layer, core layer, and tail-end layer constitute mutually independent optical round-trip intervals; an optical cavity ring-down spectrometer set is constructed, denoted as... ,in, Let A represent the a-th cavity ring-down spectrometer, and let A represent the total number of cavity ring-down spectrometers. Each cavity ring-down spectrometer synchronously acquires the ring-down signals of the front-end layer, the core layer, and the tail-end layer. The preset data collection time series is denoted as... ,in, Let t represent the t-th data collection time point, and T represent the total number of data collection time points. Let the data collection time points be... Lower cavity ring-down spectrometer The acquired ringback signals from the front-end, core, and tail layers are denoted as follows: and .

[0007] As a preferred embodiment of the online monitoring method for multi-component gas concentration in optical cavity ring-down spectroscopy described in this invention, based on data acquisition time points... Lower cavity ring-down spectrometer Acquired front-end layer ring-down signal Core layer fading signal and tail layer ringback signal Constructing data collection time points The cavity ringback matrix is ​​as follows: ; in, Indicates the data collection time point The cavity ringback matrix below, Indicates the data collection time point Lower cavity ring-down spectrometer The collected oscillation signal of the i-th layer, .

[0008] As a preferred embodiment of the online monitoring method for multi-component gas concentration in optical cavity ring-down spectroscopy described in this invention, a standard gas of a preset concentration is introduced within the optical round-trip intervals corresponding to the front-end layer, core layer, and tail-end layer, based on the optical path propagation direction, and based on the data acquisition time series. The calibration time point corresponding to the k-th calibration operation is denoted as . ; Under standard gas stabilization conditions, the cavity ring-down spectrometer synchronously acquires standard ring-down signals from the front-end layer, core layer, and tail-end layer at calibration time points; and records the calibration time points respectively. Below, optical cavity ring-down spectrometer The acquired front-end layer standard ring-down signal, core layer standard ring-down signal, and tail-end layer standard ring-down signal are denoted as follows: and And calculate the initial gas concentration values ​​for the front-end layer, core layer, and tail-end layer, denoted as follows: and ; Constructing an optical cavity ring-down spectrometer At the calibrated time point The hierarchical concentration error vector is denoted as... ,in, This indicates the preset concentration of the standard gas; it also indicates the total concentration of the optical cavity ring-down spectrometer at the calibration time point. The hierarchical concentration error vector is used to construct a self-calibrated concentration error matrix.

[0009] As a preferred embodiment of the online monitoring method for multi-component gas concentration in optical cavity ring-down spectroscopy described in this invention, the specific implementation process for calculating the initial gas concentration values ​​of the front-end layer, core layer, and tail-end layer includes: The initial gas concentrations for the front-end, core, and rear-end layers are calculated using the following formulas: ; in, Indicates the calibration time point Initial gas concentration in the front-end layer below, Indicates the calibration time point Initial values ​​of core layer gas concentration, Indicates the calibration time point Initial value of gas concentration in the tail layer below, and These represent the preset hierarchical response coefficients for the front-end layer, core layer, and tail layer, respectively.

[0010] As a preferred embodiment of the online monitoring method for multi-component gas concentration using optical cavity ring-down spectroscopy described in this invention, the data acquisition time points are obtained. The ring-down signals of the front-end layer, core layer, and tail-end layer were collected by the optical cavity ring-down spectrometer, and the ring-down signal sets of the front-end layer, core layer, and tail-end layer were constructed respectively. The maximum and minimum decaying signals in the front-end layer decaying signal set are used as the upper and lower envelope values ​​of the front-end layer; the maximum and minimum decaying signals in the core layer decaying signal set are used as the upper and lower envelope values ​​of the core layer; the maximum and minimum decaying signals in the tail-end layer decaying signal set are used as the upper and lower envelope values ​​of the tail-end layer; the upper and lower envelope values ​​of the i-th layer are denoted as... and ,in, ; Based on the upper envelope value of the i-th layer With lower envelope value Calculate the data collection time point The fused ringback signal of the i-th layer is calculated using the following formula: ,in, Indicates the data collection time point The fused ringback signal of the i-th layer; Obtain data collection time points respectively The fusing signals from the front-end layer, core layer, and tail-end layer are fused, and the data acquisition time points are constructed. The fusion level decay matrix below.

[0011] As a preferred embodiment of the online monitoring method for multi-component gas concentration in optical cavity ring-down spectroscopy described in this invention, the concentrations of all optical cavity ring-down spectrometers at the calibration time point are obtained. The hierarchical concentration error vectors are arranged sequentially to construct a self-calibrated concentration error matrix, denoted as . ; Based on the self-calibrated concentration error matrix Cross-instrument offsetting was performed on the front-end layer, core layer, and tail-end layer respectively, and the concentration shift of each layer was calculated using the following formula: ; in, This represents the concentration shift of the i-th layer, and A represents the total number of cavity ring-down spectrometers. This represents the initial value of the gas concentration in the i-th layer. This indicates the preset concentration of the standard gas. ; Based on the concentration offsets of the front-end, core, and tail-end layers, a hierarchical error hedging matrix is ​​constructed, denoted as... ,in, .

[0012] As a preferred embodiment of the online monitoring method for multi-component gas concentration in optical cavity ringback spectroscopy described in this invention, it is based on the fusion of hierarchical ringback matrix and hierarchical error offset matrix. Consistency correction is performed on the fused ringback signals of the front-end layer, core layer, and tail-end layer, as follows: ; in, This represents the hierarchical oscillation signal after consistency correction for the i-th layer. Indicates the data collection time point The fused ringback signal of the i-th layer, This represents the concentration offset of the i-th layer. This indicates the preset concentration of the standard gas. .

[0013] As a preferred embodiment of the online monitoring method for multi-component gas concentration in optical cavity ringback spectroscopy described in this invention, the hierarchical ringback signal based on the consistency correction of the i-th layer is used. Calculate the data collection time point The equivalent gas concentration of the i-th layer is calculated using the following formula: ; in, Indicates the data collection time point The equivalent gas concentration of the i-th layer is as follows: This represents the preset hierarchical influence factor of the i-th layer; Based on the hierarchical equivalent gas concentration of the i-th layer Calculate the data collection time point The formula for calculating the overall concentration of multi-component gases is as follows: ,in, Indicates the data collection time point The overall concentration of multi-component gases below This represents the preset hierarchical collaborative weight coefficient for the i-th layer; Data collection time point The overall concentration of multi-component gases below As the data collection time point The system outputs online monitoring results and acquires the comprehensive concentration of multi-component gases at each data acquisition time point in real time for real-time online monitoring.

[0014] An online monitoring system for multi-component gas concentration using optical cavity ring-down spectroscopy includes: an optical cavity layering and signal detection module, an error self-calibration module, a signal fusion processing module, an error offsetting and correction module, and a concentration calculation and output module. The optical cavity layering and signal detection module: Based on the optical path propagation direction, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer; Based on the ring-down signals of the front-end layer, core layer, and tail-end layer collected by the optical cavity ring-down spectrometer at the data acquisition time point, the optical cavity ring-down matrix at the data acquisition time point is constructed. The error self-calibration module introduces a standard gas of a preset concentration, uses an optical cavity ring-down spectrometer to simultaneously acquire the standard ring-down signals of the front-end layer, core layer, and tail-end layer, calculates the initial value of the gas concentration, and constructs a hierarchical concentration error vector. The signal fusion processing module: constructs a front-end layer decay signal set, a core layer decay signal set, and a tail-end layer decay signal set; obtains the upper and lower envelope values ​​of the front-end layer, core layer, and tail-end layer; calculates the fused decay signal of each layer at the data acquisition time point, and constructs a fusion-level decay matrix; The error offsetting and correction module: acquires the hierarchical concentration error vectors of all optical cavity ring-down spectrometers, constructs a self-calibrated concentration error matrix; calculates the concentration offset of each layer, and constructs a hierarchical error offsetting matrix; based on the fused hierarchical ring-down matrix and the hierarchical error offsetting matrix, performs consistency correction on the fused ring-down signals of the front-end layer, core layer and tail-end layer. The concentration calculation and output module calculates the hierarchical equivalent gas concentration and the comprehensive concentration of multi-component gases at each layer based on the hierarchical decay signal after consistency correction; and outputs the comprehensive concentration of multi-component gases at the data acquisition time as the online monitoring result at the data acquisition time.

[0015] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: The online monitoring method for multi-component gas concentration in cavity ring-down spectroscopy provided by this invention spatially divides the target cavity into a front-end layer, a core layer, and a tail-end layer based on the optical path propagation direction, and constructs mutually independent optical round-trip intervals within each layer. This allows for layered characterization of gas absorption behavior at different locations within the cavity, thereby avoiding spatial response aliasing caused by overall modeling. Furthermore, by using multiple cavity ring-down spectrometers to synchronously acquire ring-down signals from each layer at a unified data acquisition time point and constructing a cavity ring-down matrix, joint modeling of the hierarchical and instrumental dimensions is achieved, providing a structured data foundation for subsequent error analysis. Further, by introducing standard gases of preset concentrations into each layer and synchronously acquiring standard ring-down signals, the initial gas concentration values ​​for the front-end, core, and tail-end layers are calculated, and hierarchical concentration error vectors and self-calibrated concentration error matrices are constructed. This allows for the quantification of systematic deviations of different instruments at different levels. The system employs a standardized representation to provide a transferable calibration basis for error hedging in the online phase. Subsequently, by extracting and fusing the upper and lower envelope values ​​from each layer's ring-down signal set, a hierarchical fused ring-down signal is formed that reflects the stable absorption characteristics within the current sampling period, effectively reducing the impact of transient fluctuations and abnormal sampling on the monitoring results. Based on this, the concentration offset of each layer is calculated using a self-calibrated concentration error matrix, and a hierarchical error hedging matrix is ​​constructed to perform consistency correction on the fused ring-down signal, ensuring that the ring-down signals across instruments and layers maintain a unified physical reference, thus suppressing the accumulation of systematic errors from the source. Finally, the hierarchical equivalent gas concentration of each layer is calculated based on the consistent corrected hierarchical ring-down signal, and hierarchical collaborative weights are introduced to obtain the comprehensive concentration of multi-component gases, which is then output as the online monitoring result. This achieves real-time online monitoring of multi-component gas concentration with good stability, interpretability, and engineering practicality in complex optical cavity structures and multi-component gas environments. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0017] Figure 1 This is a schematic diagram of the steps of the online monitoring method for multi-component gas concentration in optical cavity ring-down spectroscopy of the present invention; Figure 2 This is a schematic diagram of the structure of the online monitoring system for multi-component gas concentration in optical cavity ring-down spectroscopy according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 In this first embodiment: a method for online monitoring of multi-component gas concentrations in optical cavity ring-down spectroscopy is provided, which includes the following steps: Step S1: Based on the direction of optical path propagation, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer; based on the ring-down signals of the front-end layer, core layer, and tail-end layer acquired by the optical cavity ring-down spectrometer at the data acquisition time point, the optical cavity ring-down matrix at the data acquisition time point is constructed.

[0020] Specifically, the optical path propagation direction in the target optical cavity is obtained, and based on the optical path propagation direction, the target optical cavity is divided into a front-end layer, a core layer, and a rear-end layer. The front-end layer, core layer, and rear-end layer constitute mutually independent optical round-trip intervals; an optical cavity ring-down spectrometer set is constructed, denoted as... ,in, Let A represent the a-th cavity ring-down spectrometer, and let A represent the total number of cavity ring-down spectrometers. Each cavity ring-down spectrometer synchronously acquires the ring-down signals of the front-end layer, the core layer, and the tail-end layer. The preset data collection time series is denoted as... ,in, Let t represent the t-th data collection time point, and T represent the total number of data collection time points. Let the data collection time points be... Lower cavity ring-down spectrometer The acquired ringback signals from the front-end, core, and tail layers are denoted as follows: and .

[0021] Furthermore, based on the data collection time point Lower cavity ring-down spectrometer Acquired front-end layer ring-down signal Core layer fading signal and tail layer ringback signal Constructing data collection time points The cavity ringback matrix is ​​as follows: ; in, Indicates the data collection time point The cavity ringback matrix below, Indicates the data collection time point Lower cavity ring-down spectrometer The collected oscillation signal of the i-th layer, .

[0022] In this invention, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer based on the direction of optical path propagation, and these layers are defined as mutually independent optical round-trip intervals. This achieves spatial decoupling modeling of the gas absorption behavior inside the optical cavity, avoiding the problem of overlapping absorption contributions at different locations in traditional overall optical cavity modeling.

[0023] Furthermore, by using multiple cavity ring-down spectrometers to synchronously acquire ring-down signals from each layer at the same data acquisition time point and constructing a cavity ring-down matrix, the following technical effects were achieved: the monitoring results at a single time point were expanded from a single signal to a two-dimensional information structure of layer × instrument; a unified data organization basis was provided for subsequent cross-instrument error offsetting and layer consistency correction; and subsequent concentration calculations no longer depended on a single instrument or a single optical path assumption, thus improving the overall system's ability to resist random errors.

[0024] Step S2: Introduce a standard gas of a preset concentration, and use a cavity ring-down spectrometer to simultaneously acquire the standard ring-down signals of the front-end layer, core layer, and tail-end layer, calculate the initial value of the gas concentration, and construct the hierarchical concentration error vector.

[0025] Specifically, within the optical round-trip intervals corresponding to the front-end layer, core layer, and tail-end layer, a standard gas of a preset concentration is introduced based on the optical path propagation direction, and based on the data acquisition time series... The calibration time point corresponding to the k-th calibration operation is denoted as . ; Under standard gas stabilization conditions, the cavity ring-down spectrometer synchronously acquires standard ring-down signals from the front-end layer, core layer, and tail-end layer at calibration time points; and records the calibration time points respectively. Below, optical cavity ring-down spectrometer The acquired front-end layer standard ring-down signal, core layer standard ring-down signal, and tail-end layer standard ring-down signal are denoted as follows: and And calculate the initial gas concentration values ​​for the front-end layer, core layer, and tail-end layer, denoted as follows: and ; Constructing an optical cavity ring-down spectrometer At the calibrated time point The hierarchical concentration error vector is denoted as... ,in, Indicates the preset concentration of the standard gas; obtains the total cavity ring-down spectrometer concentration at the calibration time point. The hierarchical concentration error vector is used to construct a self-calibrated concentration error matrix.

[0026] The specific implementation process for calculating the initial gas concentration values ​​of the front-end layer, core layer, and tail-end layer includes: The initial gas concentrations for the front-end, core, and rear-end layers are calculated using the following formulas: ; in, Indicates the calibration time point Initial gas concentration in the front-end layer below, Indicates the calibration time point Initial values ​​of core layer gas concentration, Indicates the calibration time point Initial value of gas concentration in the tail layer below, and These represent the preset hierarchical response coefficients for the front-end layer, core layer, and tail layer, respectively.

[0027] It should be noted that this formula is based on the core physical characteristics of cavity ring-down spectroscopy, namely, the positive correlation between gas concentration and the degree of ring-down signal attenuation; the ratio of the real-time ring-down signal to the standard ring-down signal reflects the difference in light absorption intensity of the gas being monitored (the ratio is subtracted by 1 to eliminate baseline shift when there is no gas absorption); the hierarchical response coefficient compensates for the optical characteristics of different layers. Due to the differences in optical path length, reflection efficiency, and gas renewal rate among the front-end, core, and tail-end layers, the same gas concentration produces different ring-down signals at different layers. and Preliminary experimental calibration ensures that the signal-concentration mapping relationship is consistent across different levels.

[0028] To address the differences in optical path length, reflection efficiency, and gas renewal rate among the front-end, core, and rear-end layers, preset parameters are used. and Personalized compensation is implemented. For example, the core layer has the longest optical path. Greater than This ensures that signal changes of the same concentration of gas at different levels can be accurately converted into concentration, solving the problem of existing technologies ignoring level differences when uniformly calibrating parameters.

[0029] CRDS technology is not sensitive to fluctuations in light source intensity, but the absolute value of a single signal is easily affected by environmental interference. The ratio of "standard signal / real-time signal" can offset common interferences such as light source intensity drift and temperature drift. Furthermore, by subtracting 1, the baseline shift when there is no gas absorption is eliminated, allowing the initial concentration value to more purely reflect the gas absorption characteristics.

[0030] In this invention, by introducing standard gases of preset concentrations into the optical round-trip intervals corresponding to the front-end layer, core layer, and tail-end layer, and synchronously acquiring the standard ring-down signals of each layer at the calibration time point, layered calibration of different spatial levels and different instrument response characteristics is achieved, rather than overall calibration in the traditional sense.

[0031] Based on this, the initial values ​​of gas concentration for each layer are calculated, and the layer concentration error vector and self-calibrated concentration error matrix are further constructed. The relationship between instrument, layer, and concentration deviation is made explicit and vectorized, so that the systematic deviation of each optical cavity ring-down spectrometer at different layers is independently characterized, providing a quantifiable and alignable source of error for subsequent error offsetting.

[0032] Step S3: Construct the front-end layer decay signal set, the core layer decay signal set, and the tail-end layer decay signal set; obtain the upper and lower envelope values ​​of the front-end layer, the core layer, and the tail-end layer; calculate the fused decay signal of each layer at the data acquisition time point, and construct the fused layer decay matrix.

[0033] Specifically, obtain the data collection time point. The ring-down signals of the front-end layer, core layer, and tail-end layer were collected by the optical cavity ring-down spectrometer, and the ring-down signal sets of the front-end layer, core layer, and tail-end layer were constructed respectively. The maximum and minimum decaying signals in the front-end layer decaying signal set are used as the upper and lower envelope values ​​of the front-end layer; the maximum and minimum decaying signals in the core layer decaying signal set are used as the upper and lower envelope values ​​of the core layer; the maximum and minimum decaying signals in the tail-end layer decaying signal set are used as the upper and lower envelope values ​​of the tail-end layer; the upper and lower envelope values ​​of the i-th layer are denoted as... and ,in, ; Based on the upper envelope value of the i-th layer With lower envelope value Calculate the data collection time point The fused ringback signal of the i-th layer is calculated using the following formula: ,in, Indicates the data collection time point The fused ringback signal of the i-th layer; It should be noted that when multiple instruments simultaneously acquire fading signals at the same level, random errors (such as instrument circuit noise and instantaneous airflow disturbances) may occur, leading to signal dispersion; upper envelope value and lower envelope value These correspond to the extreme value ranges of the signal, and averaging the two values ​​can smooth out random fluctuations and preserve the true trend of the signal (similar to noise reduction). This formula can reduce the random error of a single instrument, obtain stable decaying signals at each level, and provide reliable basic data for subsequent error correction. Specifically, when multiple instruments acquire data simultaneously, instantaneous noise (such as circuit interference or airflow disturbance) may cause signal extreme values ​​(too large or too small). Averaging the upper envelope (maximum value) and lower envelope (minimum value) can preserve the true trend of the signal and smooth out random fluctuations, making it more resistant to interference than a simple arithmetic mean—for example, when the signal of a certain instrument suddenly changes to an outlier, the envelope fusion will not be skewed, while the arithmetic mean will be affected.

[0034] Obtain data collection time points respectively The fusing signals from the front-end layer, core layer, and tail-end layer are fused, and the data acquisition time points are constructed. The fusion level decay matrix below.

[0035] In this invention, by constructing oscillation signal sets for the front-end layer, core layer, and tail-end layer respectively, and introducing upper and lower envelope values ​​to fuse and calculate the oscillation signal of each layer, the problems of transient noise, short-term fluctuations, and interference from individual abnormal sampling points on the oscillation signal are solved.

[0036] The upper and lower envelopes together reflect the signal fluctuation boundary of the same level at the current time point. The fused oscillation signal formed by the mean of the envelopes can represent the stable absorption level of the level within the current sampling period. This avoids the amplification of random deviations caused by directly selecting a single instrument or a single extreme value. It achieves robust processing of the hierarchical oscillation signal without introducing complex statistical models, providing a highly consistent input basis for subsequent error correction and concentration inversion.

[0037] Step S4: Obtain the hierarchical concentration error vectors of all optical cavity ring-down spectrometers and construct a self-calibrated concentration error matrix; calculate the concentration offset of each layer and construct a hierarchical error offset matrix; based on the fused hierarchical ring-down matrix and the hierarchical error offset matrix, perform consistency correction on the fused ring-down signals of the front-end layer, core layer and tail-end layer.

[0038] Specifically, obtain all cavity ring-down spectrometer data at the calibration time points. The hierarchical concentration error vectors are arranged sequentially to construct a self-calibrated concentration error matrix, denoted as . ; Based on the self-calibrated concentration error matrix Cross-instrument offsetting was performed on the front-end layer, core layer, and tail-end layer respectively, and the concentration shift of each layer was calculated using the following formula: ; in, This represents the concentration shift of the i-th layer, and A represents the total number of cavity ring-down spectrometers. This represents the initial value of the gas concentration in the i-th layer. This indicates the preset concentration of the standard gas. ; It should be noted that when multiple instruments collect data at the same level, there will be common systematic errors (such as instrument wavelength drift and signal offset caused by aging of the optical cavity mirror), which manifests as the difference between the initial concentration value and the standard concentration of each instrument tending to be consistent. Summing and averaging the deviations of all instruments can filter out the random errors of individual instruments and highlight the systematic offset at the level. A positive value indicates that the initial concentration values ​​of all instruments at that level are generally too high; a negative value indicates that they are generally too low.

[0039] Based on the concentration offsets of the front-end, core, and tail-end layers, a hierarchical error hedging matrix is ​​constructed, denoted as... ,in, .

[0040] Furthermore, based on the fusion of the hierarchical oscillation matrix and the hierarchical error hedging matrix... Consistency correction is performed on the fused ringback signals of the front-end layer, core layer, and tail-end layer, as follows: ; in, This represents the hierarchical oscillation signal after consistency correction for the i-th layer. Indicates the data collection time point The fused ringback signal of the i-th layer, This represents the concentration offset of the i-th layer. This indicates the preset concentration of the standard gas. .

[0041] It should be noted that the concentration offset Compared with standard concentration The ratio reflects the proportion of the system error to the standard concentration, i.e., the relative degree of signal offset; multiplying the fused signal by (1 - the relative degree of signal offset) can inversely correct the system error. If the value is positive (initial concentration is too high), the correction coefficient is less than 1, the fusion signal is suppressed, and the corresponding concentration calculation result will decrease; otherwise, it will be raised.

[0042] For example, assuming the core layer fuses the signal The corrected signal The corrected signal is closer to the true signal when there is no systematic error; In this invention, by pooling the hierarchical concentration error vectors of all optical cavity ring-down spectrometers at the calibration time point, a self-calibrated concentration error matrix is ​​constructed, and the concentration offset of each layer is calculated, thereby realizing the centralized characterization of systematic errors and cross-instrument offsetting.

[0043] Furthermore, the hierarchical error offset matrix is ​​used to perform consistency correction on the fused hierarchical decay signal. The systematic concentration deviation identified in the calibration stage is moved forward to the decay signal level for correction, avoiding post-compensation in the final concentration output stage and reducing the risk of error superposition. This ensures that the decay signals of different levels and different instruments have a unified physical reference standard at the same data acquisition time point.

[0044] Step S5: Based on the hierarchical oscillation signal after consistency correction, calculate the hierarchical equivalent gas concentration and the comprehensive concentration of multi-component gases at each data acquisition time point; output the comprehensive concentration of multi-component gases at the data acquisition time point as the online monitoring result at the data acquisition time point.

[0045] Specifically, the hierarchical oscillation signal based on the consistency correction of the i-th layer. Calculate the data collection time point The equivalent gas concentration of the i-th layer is calculated using the following formula: ; in, Indicates the data collection time point The equivalent gas concentration of the i-th layer is as follows: This represents the pre-defined hierarchical influence factor of the i-th layer, which is determined through previous experiments or expert experience. It should be noted that the numerator of this formula is the average standard signal from multiple instruments, which is more stable than the standard signal from a single instrument, thus avoiding the deviation of a single instrument's standard signal. The ratio of the average standard signal to the corrected real-time signal reflects the difference in absorption intensity of the corrected signal. The ratio is subtracted by 1 and then multiplied by the hierarchical influence factor. —— The monitoring weight is related to the layer: the core layer is the main detection area of ​​the optical cavity (with the most uniform gas distribution and the longest optical path). Maximum; rapid gas renewal in the front and rear layers. Smaller.

[0046] Based on the hierarchical equivalent gas concentration of the i-th layer Calculate the data collection time point The formula for calculating the overall concentration of multi-component gases is as follows: ,in, Indicates the data collection time point The overall concentration of multi-component gases below This represents the preset hierarchical collaborative weight coefficient for the i-th layer, which is calibrated through previous experiments or expert experience; Assuming the equivalent concentration of the front-end layer Core layer Tail end layer Then the overall concentration This result comprehensively reflects the overall concentration of the multi-component gas within the optical cavity; Data collection time point The overall concentration of multi-component gases below As the data collection time point The system outputs online monitoring results and acquires the comprehensive concentration of multi-component gases at each data acquisition time point in real time for real-time online monitoring.

[0047] Please see Figure 2 In this second embodiment: an online monitoring system for multi-component gas concentration in an optical cavity ring-down spectrum is provided. The system includes: an optical cavity layering and signal detection module, an error self-calibration module, a signal fusion processing module, an error offsetting and correction module, and a concentration calculation and output module. The optical cavity layering and signal detection module: Based on the optical path propagation direction, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer; Based on the ring-down signals of the front-end layer, core layer, and tail-end layer collected by the optical cavity ring-down spectrometer at the data acquisition time point, the optical cavity ring-down matrix at the data acquisition time point is constructed. The error self-calibration module introduces a standard gas of a preset concentration, uses an optical cavity ring-down spectrometer to simultaneously acquire the standard ring-down signals of the front-end layer, core layer, and tail-end layer, calculates the initial value of the gas concentration, and constructs a hierarchical concentration error vector. The signal fusion processing module: constructs a front-end layer decay signal set, a core layer decay signal set, and a tail-end layer decay signal set; obtains the upper and lower envelope values ​​of the front-end layer, core layer, and tail-end layer; calculates the fused decay signal of each layer at the data acquisition time point, and constructs a fusion-level decay matrix; The error offsetting and correction module: acquires the hierarchical concentration error vectors of all optical cavity ring-down spectrometers, constructs a self-calibrated concentration error matrix; calculates the concentration offset of each layer, and constructs a hierarchical error offsetting matrix; based on the fused hierarchical ring-down matrix and the hierarchical error offsetting matrix, performs consistency correction on the fused ring-down signals of the front-end layer, core layer and tail-end layer. The concentration calculation and output module calculates the hierarchical equivalent gas concentration and the comprehensive concentration of multi-component gases at each layer based on the hierarchical decay signal after consistency correction; and outputs the comprehensive concentration of multi-component gases at the data acquisition time as the online monitoring result at the data acquisition time.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for online monitoring of multi-component gas concentrations using optical cavity ring-down spectroscopy, characterized in that, The method includes the following steps: Step S1: Based on the direction of optical path propagation, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer; based on the ring-down signals of the front-end layer, core layer, and tail-end layer acquired by the optical cavity ring-down spectrometer at the data acquisition time point, the optical cavity ring-down matrix at the data acquisition time point is constructed. Step S2: Introduce standard gas at a preset concentration, and use an optical cavity ring-down spectrometer to simultaneously acquire standard ring-down signals of the front-end layer, core layer, and tail-end layer, calculate the initial value of gas concentration, and construct a hierarchical concentration error vector. Step S3: Construct the front-end layer ringback signal set, the core layer ringback signal set, and the tail-end layer ringback signal set; obtain the upper and lower envelope values ​​of the front-end layer, the core layer, and the tail-end layer; calculate the fused ringback signal of each layer at the data acquisition time point, and construct the fused layer ringback matrix. Step S4: Obtain the hierarchical concentration error vectors of all optical cavity ring-down spectrometers and construct a self-calibrated concentration error matrix; calculate the concentration offset of each layer and construct a hierarchical error offset matrix; based on the fused hierarchical ring-down matrix and the hierarchical error offset matrix, perform consistency correction on the fused ring-down signals of the front-end layer, core layer and tail-end layer. Step S5: Based on the hierarchical oscillation signal after consistency correction, calculate the hierarchical equivalent gas concentration and the comprehensive concentration of multi-component gases at each data acquisition time point; output the comprehensive concentration of multi-component gases at the data acquisition time point as the online monitoring result at the data acquisition time point.

2. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 1, characterized in that, The specific implementation process of step S1 includes: The optical path propagation direction in the target optical cavity is obtained, and based on the optical path propagation direction, the target optical cavity is divided into a front layer, a core layer, and a tail layer. The front layer, core layer, and tail layer constitute mutually independent optical round-trip intervals; an optical cavity ring-down spectrometer set is constructed, denoted as . ,in, Let A represent the a-th cavity ring-down spectrometer, and let A represent the total number of cavity ring-down spectrometers. Each cavity ring-down spectrometer synchronously acquires the ring-down signals of the front-end layer, the core layer, and the tail-end layer. The preset data collection time series is denoted as... ,in, Let t represent the t-th data collection time point, and T represent the total number of data collection time points. Let the data collection time points be... Lower cavity ring-down spectrometer The acquired ringback signals from the front-end, core, and tail layers are denoted as follows: and .

3. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 2, characterized in that, The specific implementation process of step S1 also includes: Based on data collection time points Lower cavity ring-down spectrometer Acquired front-end layer ring-down signal Core layer fading signal and tail layer ringback signal Constructing data collection time points The cavity ringback matrix is ​​as follows: ； in, Indicates the data collection time point The cavity ringback matrix below, Indicates the data collection time point Lower cavity ring-down spectrometer The collected oscillation signal of the i-th layer, .

4. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 3, characterized in that, The specific implementation process of step S2 includes: Within the optical round-trip intervals corresponding to the front-end layer, core layer, and tail-end layer, a standard gas of a preset concentration is introduced based on the optical path propagation direction, and based on the data acquisition time series... The calibration time point corresponding to the k-th calibration operation is denoted as . ; Under standard gas stabilization conditions, the cavity ring-down spectrometer synchronously acquires standard ring-down signals from the front-end layer, core layer, and tail-end layer at calibration time points; and records the calibration time points respectively. Below, optical cavity ring-down spectrometer The collected front-end layer standard ring-down signal, core layer standard ring-down signal, and tail-end layer standard ring-down signal are denoted as follows: and And calculate the initial gas concentration values ​​for the front-end layer, core layer, and tail-end layer, denoted as follows: and ; Constructing an optical cavity ring-down spectrometer At the calibrated time point The hierarchical concentration error vector is denoted as... ,in, Indicates the preset concentration of the standard gas; obtains the total cavity ring-down spectrometer concentration at the calibration time point. The hierarchical concentration error vector is used to construct a self-calibrated concentration error matrix.

5. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 4, characterized in that, The specific implementation process for calculating the initial gas concentration values ​​of the front-end layer, core layer, and tail-end layer includes: The initial gas concentrations for the front-end, core, and rear-end layers are calculated using the following formulas: ； in, Indicates the calibration time point Initial gas concentration in the front-end layer below, Indicates the calibration time point Initial values ​​of core layer gas concentration, Indicates the calibration time point Initial value of gas concentration in the tail layer below, and These represent the preset hierarchical response coefficients for the front-end layer, core layer, and tail layer, respectively.

6. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 5, characterized in that, The specific implementation process of step S3 includes: Obtain data collection time points The ring-down signals of the front-end layer, core layer, and tail-end layer were collected by the optical cavity ring-down spectrometer, and the ring-down signal sets of the front-end layer, core layer, and tail-end layer were constructed respectively. The maximum and minimum decaying signals in the front-end layer decaying signal set are used as the upper and lower envelope values ​​of the front-end layer; the maximum and minimum decaying signals in the core layer decaying signal set are used as the upper and lower envelope values ​​of the core layer; the maximum and minimum decaying signals in the tail-end layer decaying signal set are used as the upper and lower envelope values ​​of the tail-end layer; the upper and lower envelope values ​​of the i-th layer are denoted as... and ,in, ; Based on the upper envelope value of the i-th layer With lower envelope value Calculate the data collection time point The fused ringback signal of the i-th layer is calculated using the following formula: ,in, Indicates the data collection time point The fused ringback signal of the i-th layer; Obtain data collection time points respectively The fusing signals from the front-end layer, core layer, and tail-end layer are fused, and the data acquisition time points are constructed. The fusion level decay matrix below.

7. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 6, characterized in that, The specific implementation process of step S4 includes: Acquire all cavity ring-down spectrometers at the calibration time points The hierarchical concentration error vectors are arranged sequentially to construct a self-calibrated concentration error matrix, denoted as . ; Based on the self-calibrated concentration error matrix Cross-instrument offsetting was performed on the front-end layer, core layer, and tail-end layer respectively, and the concentration shift of each layer was calculated using the following formula: ； in, This represents the concentration shift of the i-th layer, and A represents the total number of cavity ring-down spectrometers. This represents the initial value of the gas concentration in the i-th layer. This indicates the preset concentration of the standard gas. ; Based on the concentration offsets of the front-end, core, and tail-end layers, a hierarchical error hedging matrix is ​​constructed, denoted as... ,in, .

8. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 6, characterized in that, The specific implementation process of step S4 also includes: Based on the fusion of hierarchical oscillation matrix and hierarchical error hedging matrix Consistency correction is performed on the fused ringback signals of the front-end layer, core layer, and tail-end layer, as follows: ； in, This represents the hierarchical oscillation signal after consistency correction for the i-th layer. Indicates the data collection time point The fused ringback signal of the i-th layer, This represents the concentration offset of the i-th layer. This indicates the preset concentration of the standard gas. .

9. The method for online monitoring of multi-component gas concentration in optical cavity ring-down spectroscopy according to claim 6, characterized in that, The specific implementation process of step S5 includes: Hierarchical fading signal based on consistency correction of layer i Calculate the data collection time point The equivalent gas concentration of the i-th layer is calculated using the following formula: ； in, Indicates the data collection time point The equivalent gas concentration of the i-th layer is as follows: This represents the preset hierarchical influence factor of the i-th layer; Based on the hierarchical equivalent gas concentration of the i-th layer Calculate the data collection time point The formula for calculating the overall concentration of multi-component gases is as follows: ,in, Indicates the data collection time point The overall concentration of multi-component gases below This represents the preset hierarchical collaborative weight coefficient for the i-th layer; Data collection time point The overall concentration of multi-component gases below As the data collection time point The system outputs online monitoring results and acquires the comprehensive concentration of multi-component gases at each data acquisition time point in real time for real-time online monitoring.

10. An online monitoring system for multi-component gas concentration using cavity ring-down spectroscopy, comprising the method for online monitoring of multi-component gas concentration using cavity ring-down spectroscopy as described in any one of claims 1-9, characterized in that, The system includes: an optical cavity layering and signal detection module, an error self-calibration module, a signal fusion processing module, an error offsetting and correction module, and a concentration calculation and output module; The optical cavity layering and signal detection module: Based on the optical path propagation direction, the target optical cavity is divided into a front-end layer, a core layer, and a tail-end layer; Based on the ring-down signals of the front-end layer, core layer, and tail-end layer collected by the optical cavity ring-down spectrometer at the data acquisition time point, the optical cavity ring-down matrix at the data acquisition time point is constructed. The error self-calibration module introduces a standard gas of a preset concentration, uses an optical cavity ring-down spectrometer to simultaneously acquire the standard ring-down signals of the front-end layer, core layer, and tail-end layer, calculates the initial value of the gas concentration, and constructs a hierarchical concentration error vector. The signal fusion processing module: constructs a front-end layer decay signal set, a core layer decay signal set, and a tail-end layer decay signal set; obtains the upper and lower envelope values ​​of the front-end layer, core layer, and tail-end layer; calculates the fused decay signal of each layer at the data acquisition time point, and constructs a fusion-level decay matrix; The error offsetting and correction module: acquires the hierarchical concentration error vectors of all optical cavity ring-down spectrometers, constructs a self-calibrated concentration error matrix; calculates the concentration offset of each layer, and constructs a hierarchical error offsetting matrix; based on the fused hierarchical ring-down matrix and the hierarchical error offsetting matrix, performs consistency correction on the fused ring-down signals of the front-end layer, core layer and tail-end layer. The concentration calculation and output module calculates the hierarchical equivalent gas concentration and the comprehensive concentration of multi-component gases at each layer based on the hierarchical decay signal after consistency correction; and outputs the comprehensive concentration of multi-component gases at the data acquisition time as the online monitoring result at the data acquisition time.

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