CN1987376A - Burning flame signal processing system - Google Patents
Burning flame signal processing system Download PDFInfo
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- CN1987376A CN1987376A CN 200610147774 CN200610147774A CN1987376A CN 1987376 A CN1987376 A CN 1987376A CN 200610147774 CN200610147774 CN 200610147774 CN 200610147774 A CN200610147774 A CN 200610147774A CN 1987376 A CN1987376 A CN 1987376A
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Abstract
The system includes signal acquisition module, digital filtering module, and analyzing process module. In finite time domain and frequency domain, the signal acquisition module collects signals in time domain, signals in frequency domain continuously in equal interval as well as collects intensity signals corresponding to signals in time domain. Using digital filtering module filters out not needed interference signal from the colleted frequency signals. Analyzing process module carries out frequency analysis for frequency signals with interference being removed. Using FFT calculates intensity value of signal under corresponding frequency. Since state of burning flame is detected through characteristic frequency of burning flame, the detected result is more true and accurate.
Description
Technical field
The present invention relates to a kind of burning flame signal processing system, be specially adapted to the analysis of boiler internal combustion flame situation.
Background technology
It is the pulsation of brightness and the brightness of flame root that flame is given the intuition of human eye.According to theoretical analysis and verification experimental verification, the flicker of flame or pulsation, its frequency is relevant with fuel type.Because the flame characteristic frequency difference during different types of fuel combustion, the intensity of the flame under every kind of frequency is also different, therefore accurately detects, the flame situation during the control fuel combustion is not easy very much.Especially in large-scale boiler, the flame situation during fuel combustion is complicated more.Yet during traditional flame detector observation flame combustion, mainly be after converting the light intensity signal of the combustion flame that receives to voltage signal by photoelectric commutator, carry out simply amplitude relatively after, just flame is had or not distinguishing of fire, and the analysis of combustion position.Such measurement, it has ignored the frequecy characteristic of flare up fire, also just is difficult to flame detection situation exactly.Special in the large-sized boiler control system of a plurality of burners, owing to multilayer flame is arranged in burning, with in the layer a plurality of flare points being arranged again, tradition fire inspection calculates and is difficult to identification that the main flame and the background flame of burner are effectively distinguished, thereby this just is easy to cause that false judgment to flame causes the misoperation of controlling.
Summary of the invention
The objective of the invention is to flame light intensity signal in the effective frequency section is carried out sampling analysis, by digital filter sampled data is carried out pre-service, remove undesired signal (HFS), and the data after handling are carried out spectrum analysis, promptly signal is handled in the frequency domain scope, and then provide the component value of the intensity and the frequency of flame, thereby realize the discriminating exactly relatively of combustion flame situation.
To achieve the above object, the technical scheme taked of the present invention is:
A kind of burning flame signal processing system is provided, and it comprises signal acquisition module and analysis and processing module, the digital filtering module between signal acquisition module and analysis and processing module;
Described signal acquisition module is used to gather the digital signal (digital signal that has been converted to by simulating signal) of combustion flame, this digital signal be included in time-limited time domain and the frequency domain uniformly-spaced the time-domain signal of continuous sampling and frequency signal and with the corresponding flame intensity signal of time-domain signal;
Described digital filtering module is that the employing iir digital filter filters (frequency) undesired signal in the combustion flame frequency signal of being gathered by above-mentioned signal acquisition module;
Described analysis and processing module is used for adopting fast fourier transform to carrying out spectrum analysis through the frequency signal behind the above-mentioned digital filtering module filtering interference signals, calculates the signal strength values under the respective frequencies, in order to show the situation of flame combustion.
The effect of burning flame signal processing system of the present invention is remarkable.
● in the disposal system of the present invention, because comprise frequency signal in the digital signal of combustion flame that signal acquisition module is gathered, therefore, disposal system of the present invention can be by the frequecy characteristic of flame, exactly the situation of flame detection burning;
● in the disposal system of the present invention, because comprise digital filtering module between signal acquisition module and analysis and processing module, unwanted undesired signal can be filtered, make that the characteristic frequency that detects is more accurate, the flame situation that is detected is truer;
● in the disposal system of the present invention, because comprise that analysis and processing module is to carrying out spectrum analysis through filtered frequency signal, and the employing fast Fourier transform (FFT) calculates the intensity level under the respective frequencies, to obtain the frequency and the intensity values corresponding of combustion flame, thereby, can be comprehensive and more accurate demonstrate the situation of flame combustion.
Description of drawings
Fig. 1 is the structural representation of burning flame signal processing system of the present invention;
Fig. 2 is the structural representation of an embodiment of digital signal input source 1 among Fig. 1;
Fig. 3 is the effect curve figure (horizontal ordinate is frequency Hz, and ordinate is an intensity) of the matlab digital filtering in the digital filtering module of the present invention;
Fig. 4 be an embodiment frequency and with the curve map of its respective intensities value;
Fig. 5 is the curve map after the curve among Fig. 4 embodiment adds digital filtering module;
Fig. 6 be another embodiment frequency and with the curve map of its respective intensities value;
Fig. 7 is the curve map after the curve among Fig. 6 embodiment adds digital filtering module;
In above-mentioned Fig. 4,5,6,7 the curve map, horizontal ordinate is that frequency～unit quantity is that lattice are counted X * 3Hz, and for example: lattice are counted X=7, and then corresponding frequency is 7 * 3Hz=21Hz; Ordinate is intensity～power P (k) value;
Fig. 8 is the process flow diagram that analysis and processing module intermediate frequency spectrum of the present invention is analyzed the FFT computing.
Embodiment
Further specify the architectural feature of disposal system of the present invention below in conjunction with accompanying drawing.
As shown in Figure 1, burning flame signal processing system of the present invention, it comprises the signal acquisition module 2 that is connected with digital signal input source 1, the digital filtering module 3 that is connected with signal acquisition module 2, the analysis and processing module 4 that is connected with digital filtering module 3.In the present embodiment, disposal system of the present invention is to place in the dsp processor TMS320C5402, and operating system software is CCS ' 5000.
Fig. 2 is the structural representation of an embodiment of digital signal input source 1.In the present embodiment, as shown in Figure 2, in digital signal input source 1, comprise by photodetector (being infrared or UV photodetector) 102 and survey flare up fire (or boiler internal combustion flare up fire) 101, through pre-process circuit 103 its flare up fire is amplified, filtering and isolation processing, the flame simulating signal after the processing are gathered by the signal acquisition module in the disposal system of the present invention 2 after through A/D converter 104 its analog signal conversion being become digital signal.If the flare up fire of gathering is the flare up fire in the boiler, because the light intensity signal of flame is a mixed signal of different frequency signals in the boiler, so, will import the flare up fire of different frequency in the following embodiments and simulate the interior flare up fire of boiler.
As shown in Figure 2, the simulating signal of the flame of input carries out every value (direct current component in the signal of place to go), filtering, processing and amplifying weak one being converted to useful electric signal to signal by pre-process circuit; Become digital signal to be input in the interior signal acquisition module of disposal system of the present invention this analog signal conversion through A/D converter (in the present embodiment, the conversion accuracy of converter is 16, and precision can reach 0.076mV);
As shown in Figure 1, the signal that signal acquisition module is gathered is the digital signal by 1 input of digital signal input source, and in the present embodiment, its operation clock frequency is 100MHZ.To for guaranteeing the continuity of data, adopt the principle of first in first out that sampled data is upgraded every the 1.3ms once sampling; Every 20ms sampled data is carried out computing; By iir digital filter filtering undesired signal useless, carry out the FFT computing more earlier, signal is converted to frequency domain by time domain, calculate the energy value of signal in each frequency band part.If the flame of boiler internal combustion, when boiler combustion, exist main flame and background flame in the burner hearth, there is very big difference in the frequency of main flame and the flicker of background flame burning, by the furnace flame signal frequency-domain is analyzed, main flame and the energy value of background flame on different frequency bands are very different, so flicker frequency by the main flame of locking, move burning flame signal processing system of the present invention main flame is carried out signal analysis, the background flare up fire that is different from main flame flicking frequency can be removed effectively, the disconnected problem of the erroneous judgement of flame detector in burner hearth detects can be solved preferably.
Structure as shown in Figure 1, described signal acquisition module 2 is used to gather the digital signal that the simulating signal of combustion flame has converted to, this digital signal as mentioned above, should be included in time-limited time domain and the frequency domain the uniformly-spaced time-domain signal of continuous sampling and frequency signal, and the flame intensity signal relative with time-domain signal.The embodiment of digital signal input source 1 as shown in Figure 2, wherein the combustion flame signal is the flare up fire of boiler internal combustion, in order to obtain the discrete spectrum distribution character of boiler flame signal, at first be that time-domain signal is carried out uniformly-spaced continuous sampling, on time domain, flare up fire carried out discretize.Time-domain signal is the magnitude of voltage of flame light intensity through obtaining after the opto-electronic conversion, and its size is proportional to the radiation light intensity.When the flare up fire time series was sampled, can obtain a group length was the flame intensity signal of N, but had two important parameters to determine in this process: the selection of sample frequency and data length size.According to Shannon's sampling theorem, if the highest frequency of flame flicking signal is f
t, for preventing mixing, selected sampling frequency f
s〉=2f
t, reality in the present embodiment, the sample frequency f of selection
sBe 768Hz, so after by the sample frequency of 768Hz data being sampled,, can in the frequency domain scope, recover the frequency signal below the 384Hz through the digital signal processing that time domain is changeed frequency domain.Because there is data to show: the flicker frequency of boiler flame is no more than 250Hz, so such sample frequency is enough for the application of actual boiler flame.After sample frequency was determined, the resolution Δ f of frequency was just decided by the data length size, promptly has:
Δf＝f
s/N；
Although Δ f is the smaller the better, Δ f is more little to be that the interior resolution of frequency range is high more, makes N big more, and calculated amount and memory space are also increased thereupon.In the present embodiment, be the FFT computing of decimation in time (DIF) base 2 what do the DFT employing.So it is 256 that N gets 2 whole power, promptly the resolution ax/f of frequency is 3Hz.Through experimental verification, find with the size of different data lengths under same sample frequency: the change of N can't make the criterion of identification of flame change, promptly as long as stable sample frequency, data length size with the unstable period flare up fire is consistent, the difference of each operating mode low frequency component amplitude size still has distinct comparability so.Here, the resolution of frequency does not have too much influence to the pattern-recognition of flame.
Described digital filtering module 3 is to be used for filtering flame frequency signal not wish the interfering frequency signal that exists in processing procedure.
Embodiment as Fig. 2, because the flame more complicated of boiler combustion, add that site environment is more abominable, so flare up fire is in the undesired signal that may be had some high frequencies by analog quantity in A/D converts the process of digital quantity to, influenced the pure property of flare up fire, so before the computing of sampled signal being carried out time domain commentaries on classics frequency domain, will carry out digital filtering, the undesired signal of filtering high frequency (as the signal that is higher than 200Hz of above-mentioned embodiment).In the present embodiment, employing be the IIR lowpass digital filter, according to the actual samples frequency of the foregoing description and the requirement of system, the performance of IIR lowpass digital filter should be that passband is 0Hz～200Hz.
In the present embodiment, the specific targets of IIR lowpass digital filter are:
Cut-off frequecy of passband Wp:200Hz; Stopband cutoff frequency Ws:350Hz;
Pass band damping Rp:0.5db; Stopband attenuation Rs:20db; Sample frequency Fs:768Hz.
Actual filter coefficient is drawn by matlab emulation:
By calling the matlab function:
[n, wn]=buttord (Wp/ (Fs/2), Ws/ (Fs/2), Rp, Rs) and [b, a]=butter (n, wn)
The filter coefficient a, the b that calculate:
a1＝1； a2＝0.88492； a3＝0.31357
b1＝0.54962； b2＝1.0992； b3＝0.54962
The difference equation of wave filter is:
y(n)＝0.54962*x(n)+1.0992*x(n-1)+0.54962*x(n-2)-0.88492*y(n-1)-0.31357*y(n-2)；
Fig. 3 is the relatively more typical filter curve of IIR lowpass digital filter that is adopted in the above-mentioned present embodiment, as can be seen from Figure 3, when≤200Hz, the intensity level of signal is maximum, be cut-off frequecy of passband Wp be 200Hz, when the 350Hz, intensity level is less than 0.1, and being stopband cutoff frequency Ws is 350Hz.
Fig. 4, Fig. 5 be an embodiment frequency and with the curve of its respective intensities value.In the present embodiment, incoming frequency is 20Hz, and amplitude is the sine wave of 2V.Fig. 4 is the curve that does not pass through digital filtering module filtering, horizontal ordinate 7 (* 3Hz) located a kurtosis; Fig. 5 is through the filtered curve of digital filtering module; Because in the present embodiment, what adopted in the digital filtering module is the IIR lowpass digital filter, and as above-mentioned, its cut-off frequecy of passband WP is 200Hz, and kurtosis is in lower passband.So Fig. 5 is identical with the kurtosis of Fig. 4, show that thus service data is consistent with desired value (theory).
Fig. 6, Fig. 7 be another embodiment frequency with its corresponding intensity level not by and two sets of curves by digital filtering module filtering.In the present embodiment, incoming frequency is 360Hz, amplitude is the sine wave of 2V.
The curve of Fig. 6 is the filtering of not passing through the IIR lowpass digital filter, and as can be seen from Figure 6 horizontal ordinate is that 120 place has a kurtosis, and peak value is about 1843;
Fig. 7 is through after the filtering of IIR lowpass digital filter portion, as can be seen from Figure 7 horizontal ordinate is that 120 place has a kurtosis, but peak value is about 92, attenuation amplitude is DB=1843/92=20.03, illustrate and pass through the signal that the later effectively filtering of IIR lowpass digital filter is higher than 200Hz, reached the requirement of expection.
Described analysis and processing module 4 is used for the frequency signal through above-mentioned digital filtering module 3 filtering interference signals is carried out spectrum analysis, and employing FFT calculates the intensity level under the respective frequencies, finishes the situation that detects boiler internal combustion flame.As above-mentioned, be to calculate the intensity level of boiler combustion flame under characteristic frequency in the present embodiment, carry out spectrum analysis to sampled data x (n).Adopted the fast fourier transform of decimation in time (DIF) base 2 in the present embodiment.According to the discrete Fourier transform (DFT) on the signal Processing, this group signal x (n) is done the DFT computing just can obtain the correspondence of this time-domain signal on frequency domain and represent that the conversion formula that is adopted is:
Wherein x (n) be row long for N (n=0,1 ... list entries N-1), X (k) is the discrete Fourier transform (DFT) of the sequence x (n) of N for the limit for length is arranged, W
N=e
-j (2 π/N), N=256 in the present embodiment
Because X (k) is a plural number, then can converts thereof into power spectrum P (k) and be:
P(k)＝|X(k)|
2/N，k＝0～(N-1)
N=256 in the present embodiment
Formula operation above the utilization, finish signal Spectrum Analysis, calculate the signal intensity under the respective frequencies, coupling system is to the flame characteristic frequency and have or not the default definite value of fiery threshold value, realizes the accurate judgement to the flame combustion state of the boiler of single burner or multi-combustor.
Fig. 8 is the process flow diagram of above-mentioned FFT computing.The part on the left side is finished the bit reversed order operation on Fig. 8 drawing, and in the FFT computing, N is 2 integral number power, and X (k) is a natural order, but calculates in order to adapt to original position, should carry out inverted order to sequence x (n) earlier before computing.The rule of inverted order is exactly that the binary digit of Ser.No. is inverted, and can obtain the inverted order value.The inverted order number is to add one in M bit most significant digit, meets 2 carries to the right.For, the weights of M bit most significant digit are N/2, and from left to right the weights of binary digit are followed successively by power N/4, N/8 ..., 2,1.Therefore, most significant digit adds one and is equivalent to decimal arithmetic J+N/2.(J represents the decimal system numerical value of current inverted order number);
The part on the right is finished the computing of FFT on Fig. 8 drawing, according to base two decomposition methods of DFT, can find that (L represents computing progression from left to right at L, L=1,2,3 ... M) in the level, (wherein N is 2 integral number power to two input data of each butterfly, js=Log
2N, Imn[] the butterfly coefficient imaginary part, Ren[] the butterfly coefficient real part) at a distance of the individual point of B=2^ (L-1), same twiddle factor correspondence the individual butterfly of 2^ (M-L) that is spaced apart 2^L and orders.From input end, carry out step by step, carry out the computing of M level altogether.When carrying out the computing of L level, obtain a different twiddle factor of 2^ (L-1) successively, whenever obtain a twiddle factor, just calculated the individual butterfly of all 2^ (M-L) of its correspondence.Therefore, can realize the FFT conversion with triple loop programs.In one-level, two of each butterfly input data are only useful to this butterfly, and the input of each butterfly, output data node coexist again on the horizontal line, so output data can deposit the shared storage unit of former input data immediately in., this method can be described as the former address and calculates, and can save a large amount of storage unit.
As the embodiment of Fig. 4, Fig. 5, incoming frequency is 20Hz, and amplitude is the light signal of the sine wave of 2V.Sample frequency with 768Hz is sampled to signal, and sample sequence x (n) length is 256, uses above-mentioned FFT formula and flow process, and the value that calculates the power spectrum P (k) under the respective frequencies is a table 1, curve such as Fig. 4; Horizontal ordinate is that 7 place has a kurtosis among Fig. 4, and other frequency components are all very little, can ignore.
Table 1:
| Horizontal ordinate: frequency | 5 | 6 | 7 | 8 | 18 | 33 | 72 | 87 | 105 |
| Ordinate P (k) | 423 | 1001 | 1938 | 465 | 176 | 101 | 180 | 52 | 21 |
Before carrying out the FFT computing, behind digital filtering module elimination high-frequency interferencing signal, carry out the FFT computing again, result of calculation is as shown in table 2, and its curve is as shown in Figure 5;
Horizontal ordinate is that 7 place exists a kurtosis too as can be seen from Figure 5, and the data of table 2 are also identical with table 1, and other frequency components are all very little equally; Data by Fig. 4 and Fig. 5 show that service data conforms to desired theoretical value.(annotate: because in the present embodiment, the sampling period is 1/3 second, so the resolution of FFT computing frequency is 3Hz, therefore, horizontal ordinate is that the frequency of 7 correspondences is 21Hz).
Table 2:
| Horizontal ordinate: frequency | 5 | 6 | 7 | 8 | 18 | 33 | 72 | 87 | 105 |
| Ordinate P (k) | 428 | 1006 | 1933 | 460 | 185 | 89 | 60 | 34 | 15 |
As the embodiment of Fig. 6, Fig. 7, incoming frequency is 360Hz, and amplitude is the light signal of the sine wave of 2V.Sample frequency with 768Hz is sampled to signal, and sample sequence x (n) length is 256, uses above-mentioned FFT formula and flow process computing, calculates the value of the power P (k) under the respective frequencies
A) be in operation and do not add the IIR lowpass digital filter, calculate the data of power spectrum P (k) value under respective frequencies curve as shown in table 3 as shown in Figure 6.As can be seen from Figure 6 horizontal ordinate is that 120 place has a kurtosis, and other frequency components are all very little, can ignore, and these data conform to desired theoretical value.
Table 3:
| Horizontal ordinate: frequency | 21 | 33 | 85 | 102 | 104 | 119 | 120 | 121 | 122 |
| Ordinate P (k) | 8 | 7 | 17 | 9 | 126 | 220 | 1843 | 287 | 154 |
B) behind the increase IIR lowpass digital filter in service, calculate power P (k) value under the respective frequencies, as shown in table 4, curve as shown in Figure 7.Horizontal ordinate is that 120 place has a kurtosis, and other frequency components are all very little, can ignore.But the size of kurtosis is about 92, with attenuation amplitude in the table 3 be DB=1843/92=20.03, illustrating increases after the IIR lowpass digital filter signal that effectively filtering is higher than 200Hz, has reached the requirement of expecting.
Table 4:
| Horizontal ordinate: frequency | 72 | 77 | 87 | 102 | 103 | 119 | 120 | 121 | 122 |
| Ordinate P (k) | 29 | 7 | 30 | 9 | 77 | 9 | 92 | 7 | 6 |
Claims (3)
1. a burning flame signal processing system comprises signal acquisition module and analysis and processing module, it is characterized in that comprising the digital filtering module between signal acquisition module and analysis and processing module;
Described signal acquisition module is used to gather the digital signal of combustion flame, this digital signal be included in time-limited time domain and the frequency domain uniformly-spaced the time-domain signal of continuous sampling and frequency signal and with the corresponding flame intensity signal of time-domain signal;
Described digital filtering module is that the employing iir digital filter filters the undesired signal in the combustion flame frequency signal of being gathered by above-mentioned signal acquisition module;
Described analysis and processing module is used for adopting fast fourier transform to carrying out spectrum analysis through the frequency signal behind the above-mentioned digital filtering module filtering interference signals, calculates the signal strength values under the respective frequencies, in order to show the situation of flame combustion.
2. burning flame signal processing system according to claim 1 is characterized in that the iir digital filter that is adopted in the described digital filtering module is that passband is the IIR lowpass digital filter of 0Hz～200Hz.
3. burning flame signal processing system according to claim 1 is characterized in that the fast fourier transform that described analysis and processing module adopts is the fast fourier transform of decimation in time base 2.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105092924A (en) * | 2009-03-13 | 2015-11-25 | 特克特朗尼克公司 | Occupancy measurement and triggering in frequency domain bitmaps |
| CN111486950A (en) * | 2020-04-20 | 2020-08-04 | Oppo广东移动通信有限公司 | Ambient light detection method, ambient light detection device, electronic apparatus, and storage medium |
-
2006
- 2006-12-22 CN CN 200610147774 patent/CN1987376A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105092924A (en) * | 2009-03-13 | 2015-11-25 | 特克特朗尼克公司 | Occupancy measurement and triggering in frequency domain bitmaps |
| CN111486950A (en) * | 2020-04-20 | 2020-08-04 | Oppo广东移动通信有限公司 | Ambient light detection method, ambient light detection device, electronic apparatus, and storage medium |
| CN111486950B (en) * | 2020-04-20 | 2022-04-19 | Oppo广东移动通信有限公司 | Ambient light detection method, ambient light detection device, electronic apparatus, and storage medium |
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