CN114993988A - Wavelength modulation-based gas concentration detection method and device and electronic equipment - Google Patents
Wavelength modulation-based gas concentration detection method and device and electronic equipment Download PDFInfo
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- 238000012545 processing Methods 0.000 claims abstract description 66
- 238000010521 absorption reaction Methods 0.000 claims abstract description 47
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
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- G01J3/42—Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry
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- G—PHYSICS
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/42—Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry
- G01J2003/423—Spectral arrangements using lasers, e.g. tunable
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Abstract
The invention discloses a method and a device for detecting gas concentration based on wavelength modulation and electronic equipment, wherein the method comprises the following steps: sampling the obtained absorption signal of the gas to be detected through sampling frequency, and preprocessing the sampled target signal according to modulation frequency to obtain a processed signal; generating a reference signal according to the unit amplitude, the modulation frequency and the initial phase, and performing phase measurement by combining a processing signal to obtain a synchronous phase; generating a multiple frequency reference signal according to the unit amplitude, the modulation frequency and the synchronous phase, and performing product operation with the processing signal to obtain a demodulation signal; and filtering the demodulation signal through a filter bank to obtain a concentration characteristic value of the gas to be detected. The phase measurement method adopted by the invention can quickly realize the phase synchronization between the processing signal and the reference signal, is beneficial to improving the accuracy of gas concentration detection, and simultaneously adopts a moving average method to further inhibit the noise in the demodulation signal, thereby effectively reducing the calculated amount.
Description
Technical Field
The invention relates to the technical field of gas concentration signal processing, in particular to a method and a device for detecting gas concentration based on wavelength modulation and electronic equipment.
Background
The wavelength modulation technique belongs to one of Tunable semiconductor Laser Absorption Spectroscopy (TDLAS), and specifically, in the wavelength tuning process, a modulation signal is added to a tuning signal (the tuning signal is used for scanning the Laser frequency and usually adopts a low-frequency sawtooth wave or a triangular wave), and then the Absorption signal is demodulated through signal processing, so as to obtain the related information of the gas concentration.
For the demodulation problem of the absorption signal, the most widely applied method at present adopts correlation detection, and the principle of the correlation detection is as follows: the periodically modulated signal to be measured has strong correlation with the generated reference signal with the same frequency and the same phase, and the noise signal has no correlation.
The method for processing the gas concentration signal based on the wavelength modulation technology by applying the correlation detection needs to meet the phase measurement of the reference signal and the signal to be measured, otherwise, the accuracy of the measurement is seriously influenced. At present, phase measurement of a reference signal and a signal to be measured is realized by generating two orthogonal co-frequency signals, then performing phase sensitive detection on two orthogonal reference signals and the signal to be measured to obtain projection intensities of specific frequency components of the signal to be measured in two orthogonal directions, and finally obtaining a measurement result through triangular synthesis. In addition, at present, a narrow-band low-pass filter is usually applied to filter out interference components in an absorption signal to obtain characteristic quantities related to gas concentration, and the filtering method often has the problems that the order of the filter is high and difficult to implement, the calculated quantity is large, the stability is poor and the like.
Disclosure of Invention
In view of the above, it is desirable to provide a method and an apparatus for detecting a gas concentration by wavelength modulation, and an electronic device.
In view of the above, the present invention provides a method for detecting a gas concentration based on wavelength modulation, comprising:
acquiring an absorption signal of gas to be detected, and sampling the absorption signal through a preset sampling frequency to obtain a target signal;
preprocessing the target signal according to a preset modulation frequency to obtain a processed signal;
generating a reference signal according to the unit amplitude, the preset modulation frequency and the initial phase, and performing phase measurement according to the processing signal and the reference signal to obtain a synchronous phase;
generating a multiple frequency reference signal according to the unit amplitude, the preset modulation frequency and the synchronous phase, and performing product operation on the processing signal and the multiple frequency reference signal to obtain a demodulation signal;
and after the demodulation signal is filtered through a filter bank, obtaining a concentration characteristic value of the gas to be detected.
Preferably, the preprocessing the target signal according to a preset modulation frequency to obtain a processed signal includes:
acquiring a preset modulation frequency, wherein the preset modulation frequency is smaller than the preset sampling frequency;
constructing a low-pass filter with the passband cut-off frequency being twice the preset modulation frequency;
and processing the target signal through the low-pass filter to obtain a processed signal.
Preferably, the performing phase measurement according to the processing signal and the reference signal includes:
acquiring a first data point with a preset length from the processing signal to generate a first pulse signal;
acquiring a second data point with a preset length from the reference signal to generate a second pulse signal;
taking the rising edge of the second pulse signal as a reference node, acquiring the number of points of the rising edge of the first pulse signal and the number of points of one period of the second pulse signal, and acquiring a synchronous phase through a preset phase measurement model; wherein the phase measurement model is:
wherein the content of the first and second substances,
for the synchronous phase, d1 is the number of rising edges of the first pulse signal, and d2 is the number of one cycle of the second pulse signal.
Preferably, after the filtering processing is performed on the demodulated signal by the filter bank, obtaining a concentration characteristic value of the gas to be detected includes:
constructing a filter bank; the filter bank comprises three layers of filters which are connected in sequence, wherein the first layer of filter is a cascade integral comb filter, the second layer of filter is a moving average filter, and the third layer of filter is a weighted time domain average filter;
inputting the demodulation signal into the filter bank, and performing frequency reduction processing on the demodulation signal through the cascade integration comb filter to obtain a frequency-reduced signal;
performing primary filtering processing on the frequency-reduced signal through the moving average filter to obtain a primary filtered signal;
and performing secondary filtering processing on the filtered signal through the weighted time domain average filter to obtain a concentration characteristic value of the gas to be detected.
Preferably, when the gas to be detected is dissolved gas in the transformer oil, the absorption signal of the gas to be detected is obtained, and the target signal is obtained after sampling the absorption signal by a preset sampling frequency, including:
introducing dissolved gas in transformer oil into a TDLAS system comprising an air chamber, a laser driver, a laser and a photoelectric detector, generating a scanning signal with a preset modulation frequency, sending the scanning signal into the laser driver to control the laser to emit corresponding laser, and converting an optical signal into an electric signal through the photoelectric detector after multiple reflection and absorption in the air chamber to obtain an absorption signal;
and sampling the absorption signal through an ADC (analog to digital converter) with a preset sampling frequency to obtain a signal to be detected containing multipoint data.
Based on the same inventive concept, the invention also provides a gas concentration detection device based on wavelength modulation, which comprises:
the signal acquisition module is used for acquiring an absorption signal of the gas to be detected, and acquiring a target signal after sampling the absorption signal by a preset sampling frequency;
the preprocessing module is used for preprocessing the target signal according to a preset modulation frequency to obtain a processed signal;
the synchronous processing module is used for generating a reference signal according to the unit amplitude, the preset modulation frequency and the initial phase, and carrying out phase measurement according to the processing signal and the reference signal to obtain a synchronous phase;
the signal demodulation module is used for generating a multiple frequency reference signal according to the unit amplitude, the preset modulation frequency and the synchronous phase, and performing product operation on the processing signal and the multiple frequency reference signal to obtain a demodulation signal;
and the concentration detection module is used for obtaining the concentration characteristic value of the gas to be detected after filtering processing is carried out on the demodulation signal through a filter bank.
Preferably, the preprocessing module comprises:
the frequency acquisition submodule is used for acquiring a preset modulation frequency, and the preset modulation frequency is smaller than the preset sampling frequency;
the filter construction submodule is used for constructing a low-pass filter with the passband cut-off frequency being two times the preset modulation frequency;
and the preprocessing submodule is used for processing the target signal through the low-pass filter to obtain a processed signal.
Preferably, the synchronous processing module includes:
the first pulse signal generation submodule is used for acquiring a first data point with a preset length from the processing signal and generating a first pulse signal;
the second pulse signal generation submodule is used for acquiring a second data point with a preset length from the reference signal and generating a second pulse signal;
the phase measurement submodule is used for acquiring the number of points of the rising edge of the first pulse signal and the number of points of one period of the second pulse signal by taking the rising edge of the second pulse signal as a reference node, and acquiring a synchronous phase through a preset phase measurement model; wherein the phase measurement model is:
wherein the content of the first and second substances,
for the synchronous phase, d1 is the number of rising edges of the first pulse signal, and d2 is the number of one cycle of the second pulse signal.
Based on the same inventive concept, the invention further provides an electronic device, which comprises a memory, a processor and a gas concentration detection program stored on the memory and capable of running on the processor, wherein when the processor executes the gas concentration detection program, the gas concentration detection method based on the wavelength modulation is realized.
The invention provides a gas concentration detection method, a gas concentration detection device and electronic equipment based on wavelength modulation. Compared with the existing gas concentration detection method, the phase measurement method adopted by the invention can quickly and effectively realize the phase synchronization between the processing signal and the reference signal, and is beneficial to improving the accuracy of gas concentration detection.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart of a method for detecting gas concentration based on wavelength modulation according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating a step S50 of a method for detecting a gas concentration based on wavelength modulation according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a target signal according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a processed signal and a reference signal after data truncation according to an embodiment of the present invention;
FIG. 5 is a graph illustrating characteristic signals related to ethane gas concentration in accordance with an embodiment of the present invention;
FIG. 6 is a graph showing the absorption peak area of ethane gas as a function of concentration in accordance with one embodiment of the present invention;
FIG. 7 is a block diagram of a wavelength modulation-based gas concentration detection apparatus according to an embodiment of the present invention;
fig. 8 is a schematic diagram of an electronic device according to an embodiment of the invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, a method for detecting a gas concentration based on wavelength modulation according to an embodiment of the present invention includes the following steps:
and step S10, acquiring an absorption signal of the gas to be detected, and sampling the absorption signal according to a preset sampling frequency to obtain a target signal.
In step S10, the gas to be measured is a gas dissolved in the transformer oil, including but not limited to carbon monoxide, carbon dioxide, methane, ethane, ethylene, acetylene, and the like. The absorption signal is an electrical signal obtained by converting an optical signal absorbed by the gas to be detected, and the absorption signal contains characteristic quantity related to the concentration of the gas to be detected. The target signal is a discrete signal obtained after sampling the absorption signal.
Understandably, the TDLAS system may be adopted to obtain an absorption signal of the gas to be measured, and then the ADC converter with a preset sampling frequency is adopted to sample the absorption signal, so as to obtain a target signal containing N point data, where the target signal may be represented as
Where N is the number of points (i.e., sampling points) of the target signal, K is the highest harmonic frequency, and f m For a predetermined modulation frequency, f s In order to preset the sampling frequency, the sampling frequency is set,
is the initial phase, δ, of the target signal 1 And (n) is an interference signal.
And step S20, preprocessing the target signal according to the preset modulation frequency to obtain a processed signal.
In step S20, the preset modulation frequency is a frequency applied to the laser scanning signal, and the preset modulation frequency is smaller than the preset sampling frequency. The processing signal is a discrete signal obtained by preprocessing the target signal, and the number of points of the processing signal is the same as that of the target signal.
It can be understood that the target signal obtained in step S10 has a higher harmonic component, and in order to reduce the interference of the higher harmonic component, a modulation frequency smaller than the sampling frequency may be generated by the function generator, and the target signal is preprocessed according to the modulation frequency, so as to obtain a processed signal containing only the lower harmonic component.
In a preferred embodiment, in order to filter the interference above the 2 nd harmonic component in the target signal, step S20 may include the following steps: firstly, acquiring a preset modulation frequency, then constructing a low-pass filter with a passband cut-off frequency being twice the preset modulation frequency, and finally processing a target signal through the low-pass filter to obtain the target signalA processed signal which may be represented as
Wherein, delta 2 And (n) is the interference signal after preprocessing. Alternatively, the low pass filter includes, but is not limited to, a butterworth low pass filter, a chebyshev low pass filter, and the like.
And step S30, generating a reference signal according to the unit amplitude, the preset modulation frequency and the initial phase, and performing phase measurement according to the processing signal and the reference signal to obtain a synchronous phase.
In step S30, the number of points of the reference signal and the processed signal is the same.
That is, to achieve frequency synchronization, a reference signal having a unit amplitude, a preset modulation frequency, and an initial phase (preferably, an initial phase of 0) is first generated, and may be expressed as
Further, in order to achieve phase synchronization, the processing signal x may be obtained according to step S20 2 (n) and the reference signal S obtained in step S30 1 And (n) carrying out phase measurement to obtain a synchronous phase.
In an alternative embodiment, in order to reduce the amount of calculation of phase synchronization and reduce the cost, it is necessary to measure the phase difference between the processing signal and the reference signal, and the phase measurement performed in step S30 according to the processing signal and the reference signal may include the following steps:
step S301, a first data point with a preset length is obtained from the processed signal, and a first pulse signal is generated.
Wherein, the preset length M is more than or equal to the quotient of two times of the preset sampling frequency and the preset modulation frequency and less than the number of sampling points, that is
I.e. separately from the processed signal x 2 (n) selecting a first data point of length M to obtainProcessing signal x containing M-point data 2 (m) and will process the signal x 2 (m) is converted into a first pulse signal ε 1 (m) wherein the first pulse signal ε 1 (m) can be expressed as:
from the above formula, if the first data point x 2 (m) is greater than 0, the first pulse signal ε 1 (m) has an amplitude of all first data points x 2 (m) maximum value, otherwise, first pulse signal ε 1 The amplitude of (m) is 0.
Step S302, a second data point with a preset length is obtained from the reference signal, and a second pulse signal is generated.
I.e. from the reference signal s 1 (n) selecting a second data point of length M to obtain a reference s containing the data of M points 1 (M), wherein M is a, a +1, …, a + M-1, a is the selected data point number, and a should satisfy the following selection conditions: first data point s with index (a + M-1) 1 And (a + M-1) is data before the absorption peak of the gas to be detected.
Further, a reference signal s containing the M point data 1 (m) into a second pulse signal ε 2 (m) wherein the second pulse signal ε 2 (m) may be expressed as:
from the above formula, if the second data point s 1 (m) is greater than 0, the second pulse signal ε 2 (m) corresponds to an amplitude of 1, otherwise, the second pulse signal ε 2 The amplitude of (m) is 0.
Optionally, the first pulse signal ε 1 (m) and a second pulse signal ε 2 And (m) are all rectangular pulse signals. Step S301 and step S302 may be executed simultaneously, or a certain step may be executed preferentially over another step.
Step S303, using the rising edge of the second pulse signal as a reference node, acquiring the number of points of the rising edge of the first pulse signal and the number of points of one period of the second pulse signal, and acquiring the synchronization phase through a preset phase measurement model.
That is, two rectangular pulse signals ε are obtained 1 (m)、ε 2 (m) then, setting a reference node, and acquiring a first pulse signal epsilon 1 (m) number of rising edges and second pulse signal ε 2 (m) the number of points in one period, and then inputting the two parameters into a preset phase measurement model, and acquiring a phase value output by the phase measurement model. Preferably, the phase measurement model is:
wherein the content of the first and second substances,
for synchronization, d1 is the number of rising edges of the first pulse signal, and d2 is the number of rising edges of the second pulse signal.
Step S40, generating a multiple frequency reference signal according to the unit amplitude, the preset modulation frequency and the synchronization phase, and performing product operation on the processed signal and the multiple frequency reference signal to obtain a demodulated signal.
In step S40, the multiple frequency reference signal is a double frequency reference signal, which can be expressed as
Generating a double-frequency reference signal s with unit amplitude, twice preset modulation frequency and synchronous phase 2 (n) processing the signal x 2 (n) and a double frequency reference signal s 2 (N) performing a product operation to obtain a demodulation signal containing the N-point data, where the demodulation signal can be expressed as:
and step S50, processing the demodulation signal through the filter bank to obtain the concentration characteristic value of the gas to be measured.
In step S50, the demodulated signal x is filtered through a pre-constructed filter bank group including multi-layer filters d (n) processing, filtering out high frequency multiplication components and noise interference generated by the product operation in the step S40, so as to obtain a direct current component y, and obtaining a concentration characteristic value of the gas to be measured according to an absorption peak area or a peak-to-valley difference (a difference between a peak value and a valley value) in the direct current component y.
Further, a linear function associated with the gas to be detected can be called, the concentration characteristic value of the gas to be detected is input into the linear function, and the standard concentration value of the gas to be detected is obtained through solving. The linear function can reflect the corresponding relation between the standard concentration value and the concentration characteristic value of the gas to be detected.
In an alternative embodiment, in order to reduce the amount of calculation, the demodulated signal is processed by constructing a filter bank including a moving average filter, and in this case, as shown in fig. 2, step S50 may include the following steps:
step S501, constructing a filter bank; the filter bank comprises three layers of filters which are connected in sequence, wherein the first layer of filter is a cascade integral comb filter, the second layer of filter is a moving average filter, and the third layer of filter is a weighted time domain average filter;
step S502, inputting each demodulation signal of the demodulation signals into a filter bank, and performing frequency reduction processing on the demodulation signals through a cascade integral comb filter to obtain frequency-reduced signals;
step S503, carrying out primary filtering processing on the frequency-reduced signal through a moving average filter to obtain a primary filtered signal;
and step S504, performing secondary filtering processing on the filtered signal through a weighted time domain average filter to obtain a concentration characteristic value of the gas to be detected.
Understandably, a mediation signal x is obtained d After (n) the step of (c),firstly, the frequency reduction treatment is carried out through a cascade integral comb filter of a filter bank to obtain a signal x after frequency reduction uc (i) Wherein i is 0,1,2, …, M/D, D is the total decimation factor of the cascade integrator comb filter, and M is the selection length of the modulation signal; then the signal x after frequency reduction is carried out by a moving average filter with an average filter window uc (i) Performing primary filtering processing to obtain a primary filtered signal x ma (j) The first-stage filtered signal x ma (j) Can be expressed as:
l, L1, respectively, the window length and the sliding step length of the sliding average filtering window; j is the number of slips, and
floor () is a floor function; k1 and k2 are variables.
Finally, a weighted time domain average filter is adopted to carry out primary filtering on the signal x ma (j) And performing secondary filtering processing to further reduce the noise interference of the signal and obtain a direct current component y. Optionally, the weighted time domain averaging filter includes, but is not limited to, a Savitzky-Golay filter.
In an alternative embodiment, when the gas to be measured is a gas dissolved in transformer oil, step S10 may include the following steps:
step S101, introducing gas dissolved in transformer oil into a TDLAS system comprising an air chamber, a laser driver, a laser and a photoelectric detector, generating a scanning signal with preset modulation frequency, sending the scanning signal into the laser driver to control the laser to emit corresponding laser, reflecting and absorbing for multiple times in the air chamber, and converting an optical signal into an electric signal through the photoelectric detector to obtain an absorption signal;
step S102, sampling the absorption signal through an ADC (analog to digital converter) with a preset sampling frequency to obtain a signal to be detected containing multipoint data.
The TDLAS system comprises an air chamber, a laser, a photoelectric detector and a laser driver connected with the laser; the laser and the photoelectric detector are respectively arranged at two ends of the air chamber. The corresponding relation that the preset sampling frequency and the preset modulation frequency should meet is as follows: when a signal with twice preset modulation frequency is used as a concentration characteristic signal of dissolved gas in transformer oil, the preset sampling frequency is at least greater than four times of the preset modulation frequency.
Understandably, after the dissolved gas in the transformer oil is introduced into the gas chamber of the TDLAS system, scanning signals with preset modulation frequency are generated and sent to the laser driver to control the laser device arranged at one end of the gas chamber to emit corresponding modulation laser, the modulation laser is absorbed by the dissolved gas in the transformer oil after being reflected for multiple times in the gas chamber, and the acquired optical signals are converted into electric signals through the photoelectric detector arranged at the other end of the gas chamber to be output, so that absorption signals related to the concentration of the dissolved gas in the transformer oil are obtained. Further, when the absorption signal characterized as the electric signal is obtained, the ADC performs sampling on the absorption according to a preset sampling frequency to obtain a target signal containing N-point data.
In an alternative embodiment, taking the gas to be detected as ethane gas as an example, the method for detecting the gas concentration based on the wavelength modulation technology may include the following steps:
step one, ethane gas with the concentration of 100ppm is introduced into a gas chamber with the optical path of 10 meters, laser which can scan in a certain range is emitted through a laser, and the modulation frequency (f) of the laser m ) Set to 10KHz, and simultaneously receive the signal to be measured (the signal to be measured is an optical signal) absorbed by ethane gas through a photoelectric detector, and then pass through the sampling frequency (f) s ) The ADC converter of 4MHz performs analog-to-digital conversion on the output signal of the photodetector (the output signal is an electrical signal obtained by photoelectrically converting the signal to be measured), and obtains a target signal x including 400000 points of data 1 (n) as shown in FIG. 3.
Step two, the target signal x is processed by a Butterworth low-pass filter with the cut-off frequency of 20KHz 1 (n) after processing, obtaining a processed signal x 2 (n)；
Step three, generating the amplitude as unit amplitude, the frequency as 10KHz and the phaseReference signal s of 0 containing 400000 points of data 1 (n) and selecting the processing signals x respectively 2 (n) and a reference signal s 1 (n) from 2000 th to 3000 th point to obtain the processed signal s after data interception 1 (m) and a reference signal s 1 (m) as shown in FIG. 4, the data in FIG. 4 is intercepted to obtain a processed signal s 1 (m) and a reference signal s 1 (m) are converted into rectangular pulse signals ε, respectively 1 (m)、ε 2 (m)。
With a second pulse signal e 2 (m) the rising edge is used as a reference node to obtain a first pulse signal epsilon 1 (m) the number of rising edges d1 ═ 35, and a second pulse signal ε 2 (m) the number of points d2 in one cycle is 400, and the synchronous phase is obtained through a phase measurement model
Step four, generating a double-frequency reference signal s with unit amplitude, frequency of 20KHz and phase of 0.5498 2 (n) dividing the frequency doubled reference signal s 2 (n) and the processing signal x 2 (n) performing a product operation to obtain a demodulated signal x d (n)。
Step five, after the total decimation factor of the cascaded integrator comb filters in the filter bank is set to be D-20, the length of a window in the moving average filter is set to be L-1000 and the sliding step length is set to be L1-20, the moving average method is applied to the demodulated signal x d (n) processing was performed to obtain a characteristic signal related to the concentration of ethane gas, as shown in FIG. 5.
And step five, acquiring a trough and a peak of an ethane gas absorption peak from the characteristic signal, and calculating the area of the absorption peak to obtain a concentration characteristic value of the ethane gas. By applying the above method, the absorption peak area calculation under different ethane gas concentrations of 0-500 ppm can be realized, and a relation curve between the absorption peak area and the concentration of ethane gas can be obtained, as shown in fig. 6.
Linearity of the fitted curve (i.e., R) according to FIG. 6 2 Value) can reach 0.9972, effectively verifying the accuracy of the invention.
In summary, in the gas concentration detection method based on wavelength modulation provided in this embodiment, first, an absorption signal of a gas to be detected is sampled according to a sampling frequency, a target signal obtained by sampling is preprocessed according to the modulation frequency to obtain a processed signal, then, reference signals of a unit amplitude, a modulation frequency and an initial phase are generated, phase measurement is performed according to the processed signal and the reference signal to obtain a synchronous phase, then, a multiple-frequency reference signal of the unit amplitude, the multiple-frequency modulation frequency and the synchronous phase is generated, product operation is performed on the processed signal and the multiple-frequency reference signal, and finally, a demodulated signal obtained by the product operation is processed through a filter bank to obtain a concentration characteristic value of the gas to be detected. Compared with the existing gas concentration detection method, the phase measurement method adopted by the embodiment can quickly and effectively realize phase synchronization between the processing signal and the reference signal, and is beneficial to improving the accuracy of gas concentration detection. In addition, the method for detecting the gas concentration based on the wavelength modulation is convenient to realize in an embedded mode.
As shown in fig. 7, based on the same inventive concept, corresponding to any of the above-mentioned embodiments, an embodiment of the present invention further provides a wavelength modulation-based gas concentration detection apparatus, which includes a signal acquisition module 110, a preprocessing module 120, a synchronization processing module 130, a signal demodulation module 140, and a concentration detection module 150, where details of each functional module are as follows:
the signal acquisition module 110 is configured to acquire an absorption signal of a gas to be detected, and sample the absorption signal by using a preset sampling frequency to obtain a target signal;
the preprocessing module 120 is configured to preprocess the target signal according to a preset modulation frequency to obtain a processed signal;
a synchronous processing module 130, configured to generate a reference signal according to the unit amplitude, the preset modulation frequency, and the initial phase, and perform phase measurement according to the processing signal and the reference signal to obtain a synchronous phase;
the signal demodulation module 140 is configured to generate a multiple frequency reference signal according to the unit amplitude, the preset modulation frequency, and the synchronous phase, and perform product operation on the processed signal and the multiple frequency reference signal to obtain a demodulated signal;
and the concentration detection module 150 is configured to obtain a concentration characteristic value of the gas to be detected after filtering the demodulated signal through the filter bank.
In an alternative embodiment, the signal obtaining module 110 includes the following sub-modules, and the detailed description of each functional sub-module is as follows:
the absorption signal acquisition submodule is used for introducing dissolved gas in the transformer oil into a TDLAS system comprising an air chamber, a laser driver, a laser and a photoelectric detector, generating a scanning signal with preset modulation frequency, sending the scanning signal into the laser driver to control the laser to emit corresponding laser, reflecting and absorbing for many times in the air chamber, and converting an optical signal into an electric signal through the photoelectric detector to obtain an absorption signal;
and the sampling submodule is used for sampling the absorption signal through an ADC (analog to digital converter) with a preset sampling frequency to obtain a signal to be detected containing multipoint data.
In an alternative embodiment, the preprocessing module 120 includes the following sub-modules, and the detailed description of each functional sub-module is as follows:
and the frequency acquisition submodule is used for acquiring a preset modulation frequency, and the preset modulation frequency is smaller than the preset sampling frequency.
The filter construction submodule is used for constructing a low-pass filter with the passband cut-off frequency being two times of the preset modulation frequency;
and the preprocessing submodule is used for processing the target signal through a low-pass filter to obtain a processed signal.
In an alternative embodiment, the synchronization processing module 130 includes the following sub-modules, and the detailed description of each functional sub-module is as follows:
the first pulse signal generation submodule is used for acquiring a first data point with a preset length from the processing signal and generating a first pulse signal;
the second pulse signal generation submodule is used for acquiring a second data point with a preset length from the reference signal and generating a second pulse signal;
the phase measurement submodule is used for acquiring the number of points of the rising edge of the first pulse signal and the number of points of one period of the second pulse signal by taking the rising edge of the second pulse signal as a reference node, and acquiring a synchronous phase through a preset phase measurement model; wherein, the phase measurement model is as follows:
wherein, the first and the second end of the pipe are connected with each other,
for the synchronization phase, d1 is the number of rising edges of the first pulse signal, and d2 is the number of points of one cycle of the second pulse signal.
In an alternative embodiment, the concentration detection module 150 includes the following sub-modules, and the detailed description of each functional sub-module is as follows:
the filter bank constructing submodule is used for constructing a filter bank; the filter bank comprises three layers of filters which are connected in sequence, wherein the first layer of filter is a cascade integral comb filter, the second layer of filter is a moving average filter, and the third layer of filter is a weighted time domain average filter;
the frequency reduction submodule is used for inputting the demodulation signal into the filter bank and performing frequency reduction processing on the demodulation signal through the cascade integration comb filter to obtain a frequency-reduced signal;
the first-stage filtering submodule is used for carrying out first-stage filtering processing on the frequency-reduced signal through a moving average filter to obtain a first-stage filtered signal;
and the secondary filtering submodule is used for carrying out secondary filtering processing on the filtered signals through the weighted time domain average filter to obtain the concentration characteristic value of the gas to be detected.
The apparatus of the foregoing embodiment is used to implement the corresponding method in the foregoing embodiment, and has the beneficial effects of the corresponding method embodiment, which are not described herein again.
Based on the same inventive concept, corresponding to any of the above-mentioned embodiments, an embodiment of the present invention further provides an electronic device, which includes a memory, a processor, and a gas concentration detection program stored in the memory and executable on the processor, wherein the processor implements the wavelength modulation-based gas concentration detection method according to any of the above-mentioned embodiments when executing the gas concentration detection program.
Fig. 8 shows a more specific hardware diagram of an electronic device provided in this embodiment, where the device may include: a processor 100, a memory 200, an input/output interface 300, a communication interface 400, and a bus 500. Wherein the processor 100, the memory 200, the input/output interface 300 and the communication interface 400, the bus 500 enable a communication connection within the device between each other.
The processor 100 may be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits, and is configured to execute related programs to implement the technical solution provided by the embodiment of the present invention.
The Memory 200 may be implemented in the form of a ROM (Read Only Memory), a RAM (random access Memory), a static storage device, a dynamic storage device, or the like. The memory 200 may store an operating system and other application programs, and when the technical solution provided by the embodiment of the present invention is implemented by software or firmware, the relevant program codes are stored in the memory 200 and called to be executed by the processor 100.
The input/output interface 300 is used for connecting an input/output module to realize information input and output. The i/o module may be configured as a component within the device (not shown) or may be external to the device to provide corresponding functionality. The input devices may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output devices may include a display, a speaker, a vibrator, an indicator light, etc.
The communication interface 400 is used for connecting a communication module (not shown in the figure) to realize the communication interaction between the device and other devices. The communication module can realize communication in a wired mode (such as USB, network cable and the like) and also can realize communication in a wireless mode (such as mobile network, WIFI, Bluetooth and the like).
It should be noted that although the above-mentioned device only shows the processor 100, the memory 200, the input/output interface 300, the communication interface 400 and the bus 500, in a specific implementation, the device may also include other components necessary for normal operation. In addition, those skilled in the art will appreciate that the above-described apparatus may also include only those components necessary to implement the embodiments of the present description, and not necessarily all of the components shown in the figures.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is merely exemplary in nature, and is not intended to suggest that the scope of the invention is limited to these examples; within the idea of the invention, also features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity.
The present embodiments are intended to embrace all such alterations, modifications and variations that fall within the broad scope of the present invention. Therefore, any omissions, modifications, substitutions, improvements and the like that may be made without departing from the spirit or scope of the embodiments of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. A gas concentration detection method based on wavelength modulation is characterized by comprising the following steps:
acquiring an absorption signal of gas to be detected, and sampling the absorption signal through a preset sampling frequency to obtain a target signal;
preprocessing the target signal according to a preset modulation frequency to obtain a processed signal;
generating a reference signal according to the unit amplitude, the preset modulation frequency and the initial phase, and performing phase measurement according to the processing signal and the reference signal to obtain a synchronous phase;
generating a multiple frequency reference signal according to the unit amplitude, the preset modulation frequency and the synchronous phase, and performing product operation on the processing signal and the multiple frequency reference signal to obtain a demodulation signal;
and after the demodulation signal is filtered through a filter bank, obtaining a concentration characteristic value of the gas to be detected.
2. The method for detecting the gas concentration based on the wavelength modulation according to claim 1, wherein the preprocessing the target signal according to a preset modulation frequency to obtain a processed signal comprises:
acquiring a preset modulation frequency, wherein the preset modulation frequency is smaller than the preset sampling frequency;
constructing a low-pass filter with the passband cut-off frequency being twice the preset modulation frequency;
and processing the target signal through the low-pass filter to obtain a processed signal.
3. The method of claim 1, wherein the performing phase measurements based on the processed signal and the reference signal comprises:
acquiring a first data point with a preset length from the processing signal to generate a first pulse signal;
acquiring a second data point with a preset length from the reference signal to generate a second pulse signal;
taking the rising edge of the second pulse signal as a reference node, acquiring the number of points of the rising edge of the first pulse signal and the number of points of one period of the second pulse signal, and acquiring a synchronous phase through a preset phase measurement model; wherein the phase measurement model is:
wherein the content of the first and second substances,
for the synchronous phase, d1 is the number of rising edges of the first pulse signal, and d2 is the number of one cycle of the second pulse signal.
4. The method for detecting the gas concentration based on the wavelength modulation according to claim 1, wherein the obtaining the characteristic value of the concentration of the gas to be detected after filtering the demodulated signal by a filter bank comprises:
constructing a filter bank; the filter bank comprises three layers of filters which are connected in sequence, wherein the first layer of filter is a cascade integral comb filter, the second layer of filter is a moving average filter, and the third layer of filter is a weighted time domain average filter;
inputting the demodulation signal into the filter bank, and performing frequency reduction processing on the demodulation signal through the cascade integration comb filter to obtain a frequency-reduced signal;
performing primary filtering processing on the frequency-reduced signal through the moving average filter to obtain a primary filtered signal;
and performing secondary filtering processing on the filtered signal through the weighted time domain average filter to obtain a concentration characteristic value of the gas to be detected.
5. The method for detecting the gas concentration based on the wavelength modulation according to any one of claims 1 to 4, wherein the gas to be detected is a gas dissolved in transformer oil; the method comprises the following steps of obtaining an absorption signal of gas to be detected, sampling the absorption signal through a preset sampling frequency, and then obtaining a target signal, wherein the method comprises the following steps:
introducing dissolved gas in transformer oil into a TDLAS system comprising an air chamber, a laser driver, a laser and a photoelectric detector, generating a scanning signal with a preset modulation frequency, sending the scanning signal into the laser driver to control the laser to emit corresponding laser, and converting an optical signal into an electric signal through the photoelectric detector after multiple reflection and absorption in the air chamber to obtain an absorption signal;
and sampling the absorption signal through an ADC (analog to digital converter) with a preset sampling frequency to obtain a signal to be detected containing multipoint data.
6. A gas concentration detection apparatus based on wavelength modulation, comprising:
the signal acquisition module is used for acquiring an absorption signal of the gas to be detected, and acquiring a target signal after sampling the absorption signal by a preset sampling frequency;
the preprocessing module is used for preprocessing the target signal according to a preset modulation frequency to obtain a processed signal;
the synchronous processing module is used for generating a reference signal according to the unit amplitude, the preset modulation frequency and the initial phase, and carrying out phase measurement according to the processing signal and the reference signal to obtain a synchronous phase;
the signal demodulation module is used for generating a multiple frequency reference signal according to the unit amplitude, the preset modulation frequency and the synchronous phase, and performing product operation on the processing signal and the multiple frequency reference signal to obtain a demodulation signal;
and the concentration detection module is used for obtaining the concentration characteristic value of the gas to be detected after filtering the demodulation signal through a filter bank.
7. The wavelength modulation based gas concentration detection apparatus according to claim 6, wherein the preprocessing module comprises:
the frequency acquisition submodule is used for acquiring a preset modulation frequency, and the preset modulation frequency is smaller than the preset sampling frequency;
the filter construction submodule is used for constructing a low-pass filter with the passband cut-off frequency being twice the preset modulation frequency;
and the preprocessing submodule is used for processing the target signal through the low-pass filter to obtain a processed signal.
8. The wavelength modulation based gas concentration detection apparatus according to claim 6, wherein the synchronous processing module comprises:
the first pulse signal generation submodule is used for acquiring a first data point with a preset length from the processing signal and generating a first pulse signal;
the second pulse signal generation submodule is used for acquiring a second data point with a preset length from the reference signal and generating a second pulse signal;
the phase measurement submodule is used for acquiring the number of points of the rising edge of the first pulse signal and the number of points of one period of the second pulse signal by taking the rising edge of the second pulse signal as a reference node, and acquiring a synchronous phase through a preset phase measurement model; wherein the phase measurement model is:
wherein, the first and the second end of the pipe are connected with each other,
for the synchronization phase, d1 is the number of rising edges of the first pulse signal, and d2 is the number of points of one cycle of the second pulse signal.
9. An electronic device comprising a memory, a processor, and a gas concentration detection program stored on the memory and executable on the processor, wherein the processor implements the wavelength modulation-based gas concentration detection method according to any one of claims 1 to 5 when executing the gas concentration detection program.
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