Detection method of dual-wavelength photoelectric smoke detector

Abstract

The invention discloses a detection method of a dual-wavelength photoelectric smoke detector, which is characterized in that the scattered light intensity is related to the particle diameter d, the incident light wavelength lambda, the particle medium refractive index m, the scattering angle theta and the distance R from particles to a receiving point, and when the particle size of the particles is far smaller than the incident light wavelength lambda, the scattering condition is in a Rayleigh scattering region; when the particle size of the particles is close to the incident light wavelength lambda, the scattering condition is in a Mie scattering region; selecting blue light and infrared light as incident light sources, analyzing the intensity of approximate scattered light by using the Rayleigh theory, and calculating the ratio of the scattering intensity of the blue light to the scattering intensity of the infrared light of the fire particles in a Rayleigh scattering region; performing double-machine calibration of air calibration and smoke calibration, simulating the response of a blue light detector and an infrared light detector to aerosols with different particle sizes, acquiring data, calculating the ratio of the data, performing smoothing processing, and finally determining an alarm point; and judging the particle size range of the aerosol. According to the invention, the false alarm rate of the detector can be reduced, and real fire signals can be effectively detected.

Description

Technical Field

[0001] The invention relates to a dual-wavelength photoelectric smoke detector detection method. Background Art

[0002] Fire particles and interference particles have different light scattering abilities. The scattered light signal received by the fire detector contains information about the particulate matter. Studying the difference in the scattered light signals of fire particles and interference particles can reduce false alarms caused by interference particles such as water vapor and dust. There is a large difference in the particle size of fire particles and interference particles. The particle size of most fire particles is 1μm or less, while the particle size of interference particles such as water vapor and dust is much larger than 1μm. Infrared light and blue light have different response sensitivities to aerosols of different particle sizes, and change with the change of aerosol particle size. Therefore, how to reduce the false alarms of high-sensitivity detectors caused by large particle interference aerosols and effectively detect real fire signals is a technical problem that needs to be solved urgently. Summary of the invention

[0003] In order to overcome the above disadvantages, the purpose of the present invention is to provide a dual-wavelength photoelectric smoke detector detection method that reduces the false alarm rate of the detector and can effectively detect real fire signals.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present invention is: a dual-wavelength photoelectric smoke detector detection method, according to the Mie scattering model, the scattered light intensity is related to the particle diameter d, the incident light wavelength λ, the particle medium refractive index m, the scattering angle θ, and the distance R from the particle to the receiving point. When the particle size is much smaller than the incident light wavelength λ, the scattering condition is in the Rayleigh scattering region, and when the particle size is close to the incident light wavelength λ, the scattering condition is in the Mie scattering region; blue light and infrared light are selected as the incident light sources, the particle medium refractive index m changes slightly with the incident light wavelength λ, and for the two wavelengths of the light source are approximately equal, the scattering angle θ is unchanged and the same, the particle size of the fire particle is 1μm or less, the Rayleigh theory is used to analyze the approximate scattered light intensity, and the ratio of the blue light scattering intensity and the infrared light scattering intensity of the fire particle in the Rayleigh scattering region is calculated. When the fire particles are in the Mie scattering area, the wavelength of infrared light is long, and small particles scatter infrared light weakly, but small particles have strong scattering of blue light with a shorter wavelength. At this time, the scattered light intensity of blue light and infrared light is greater than the ratio of the blue light scattering intensity to the infrared light scattered intensity; the particle size of the interfering particles is much larger than the wavelength of the incident light, and they are in the Fraunhofer diffraction area, and have a strong scattering effect on both infrared light and blue light. The ratio of the infrared light and blue light scattered light intensity is approximately 1, and it is considered that the scattered light intensity is independent of the wavelength; the air calibration machine and the smoke calibration machine are calibrated, and the response of the blue light and infrared light detectors to aerosols of different particle sizes is simulated. Data is collected and their ratio is calculated. All data simulation values ​​are smoothed by fitting with the 31-bit least squares estimation method. The simulated values ​​of the infrared light and blue light data are recorded as: S after smoothing. r and S b During dual-machine calibration, the calibration value is stored and read in the IC, and the calibration values ​​of infrared light and blue light are calculated and processed separately to finally determine the alarm point; the aerosol particle size range is judged by the ratio of the dual-wavelength output responses of the detector. When the ratio of blue light to infrared light is set to be greater than a fixed value, it is judged to be dust, otherwise it is fire smoke particles.

[0005] Preferably, when the scattering condition is in the Rayleigh scattering region, the approximate scattered light intensity is:

[0006]

[0007] Where I is the total scattered light intensity, I0 is the natural light intensity. It can be seen from formula (1) that the scattered light intensity is inversely proportional to the fourth power of the wavelength of the incident light and is directly proportional to the sixth power of the particle size.

[0008] Preferably, blue light with a wavelength of 450 nm and infrared light with a wavelength of 940 nm are selected as the incident light sources.

[0009] Preferably, the ratio of the blue light scattering intensity to the infrared light scattering intensity of the fire particles in the Rayleigh scattering region is as shown in formula (2):

[0010] R1=I B1 / I R1 =(1 / 450 4 )×(1 / 940 4 ) -1 ≈19 (2)

[0011] Where: I B1 is the blue light scattering intensity in the Rayleigh scattering region, I R1 is the infrared light scattering intensity in the Rayleigh scattering region, and R1 is the ratio of the blue light scattering intensity to the infrared light scattering intensity in the Rayleigh scattering region.

[0012] Preferably, the aerosols of different particle sizes include wood, cotton rope, polyurethane, n-heptane, and decalin.

[0013] Preferably, during the dual-machine calibration, the calibration values ​​are stored and read in the IC, and the calibration values ​​of infrared light and blue light are respectively processed and synthesized:

[0014] APR′=116-0.0055*R rHcal150 (3)

[0015] APB′=106+0.00096*R Bcal150 (4)

[0016] AP'=APR'+APB' (5)

[0017] AP=0.75*AP'+0.55*((Sr 25 -Sr1)+(Sb 25 -Sb1)) (6)

[0018] In formula (3) and formula (4), R rHcal150 , R Bcal150 are the standard calibration values ​​of infrared light and blue light stored during smoke calibration. APR′ and APB′ are the threshold values ​​of infrared light and blue light when they reach the alarm point based on the calibration values. Formula (5) and (6) are comprehensive treatments of the degree of scattering of particulate matter by infrared light and blue light. Formula (6) refers to the difference between 25 valid S values ​​of infrared light and blue light after sensing smoke based on the alarm threshold value determined by the calibration value, and finally determines the alarm point.

[0019] The beneficial effects of the dual-wavelength photoelectric smoke detector detection method of the present invention are: combining the output responses of the detector blue light and infrared light can effectively identify fire and non-fire aerosols, avoiding false alarms of high-sensitivity detectors caused by large particles interfering with the aerosol, and reducing the false alarm rate; on this basis, a composite fire detection device of a dual-wavelength photoelectric smoke sensor is built, and the fire detection system software is designed, and then true and false fire source tests are carried out to collect the changing characteristic parameters of smoke, temperature, and gas during the fire; big data is integrated, and an artificial neural network algorithm is used to integrate and analyze the collected data, and a complex network is formed by widely connecting a large number of simple processing units to perform high self-learning, self-organization, and self-adaptation with large-scale parallelism, redundancy, fault tolerance, and nonlinear mapping, and various environmental characteristic parameters detected by multiple sensors are intelligently processed to effectively detect real fire signals. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0021] This embodiment discloses a dual-wavelength photoelectric smoke detector. According to the Mie scattering model, the scattered light intensity is related to the particle diameter d, the incident light wavelength λ, the particle medium refractive index m and the scattering angle θ, and the distance R from the particle to the receiving point. When the particle diameter is much smaller than the incident light wavelength, the scattering is in the Rayleigh scattering region; when the particle diameter is close to the incident light wavelength, the scattering is in the Mie scattering region.

[0022] When the scattering situation is in the Rayleigh scattering region, the approximate scattered light intensity is:

[0023]

[0024] Where I is the total scattered light intensity, I0 is the natural light intensity. It can be seen from formula (1) that the scattered light intensity is inversely proportional to the fourth power of the wavelength of the incident light and is proportional to the sixth power of the particle size.

[0025] Blue light with a wavelength of 450nm and infrared light with a wavelength of 940nm are selected as the incident light sources. Since the refractive index m of the granular medium changes little with the wavelength λ of the incident light, it can be approximately equal for the two wavelengths of the light source; at the same time, the scattering angle θ is unchanged and the same, so m and θ in formula (1) can be regarded as constants. Because the particle size of most fire particles is 1μm or less, the Rayleigh theory is applicable to analyze the approximate scattered light intensity. The ratio of the blue light scattering intensity and the infrared light scattering intensity of fire particles in the Rayleigh scattering area is shown in formula (2):

[0026] R1=I B1 / IR1 =(1 / 450 4 )×(1 / 940 4 ) -1 ≈19 (2)

[0027] Where I B1 is the blue light scattering intensity in the Rayleigh scattering region, I R1 is the infrared light scattering intensity in the Rayleigh scattering zone, and R1 is the ratio of the blue light scattering intensity to the infrared light scattering intensity in the Rayleigh scattering zone. When the fire particles are in the Mie scattering zone, the wavelength of infrared light is relatively long, and small particles scatter infrared light weakly, but small particles scatter blue light with a shorter wavelength more strongly. At this time, the scattered light intensity of blue light and infrared light is greater than the corresponding value 19 of formula (2). It can be seen that fire particles of different particle sizes are either in the Rayleigh scattering zone or in the Mie scattering zone, and the scattering intensity of blue light and infrared light is quite different. The particle size of the interfering particles is much larger than the wavelength of the incident light, and they are in the Fraunhofer diffraction zone. They have a strong scattering effect on both infrared light and blue light. The ratio of the scattered light intensity of infrared light and blue light is approximately 1. It can be considered that the scattered light intensity is independent of the wavelength.

[0028] Perform air calibration and smoke calibration, simulate blue light and infrared light detectors for wood

[0029] The responses of aerosols of different particle sizes such as cotton rope, polyurethane, n-heptane, and decalin were collected and their ratios were calculated. For ease of comparison, all data simulation values ​​were smoothed by fitting with the 31-bit least squares estimation method. The simulated values ​​of infrared light and blue light data after smoothing are recorded as: S r and S b When calibrating two machines, the calibration values ​​are stored and read in the IC, and the calibration values ​​of infrared light and blue light are processed separately and then synthesized:

[0030] APR′=116-0.0055*R rHcal150 (3)

[0031] APB′=106+0.00096*R Bcal150 (4)

[0032] AP'=APR'+APB' (5)

[0033] AP=0.75*AP'+0.55*((Sr 25 -Sr1)+(Sb 25 -Sb1)) (6)

[0034] In formula (3) and formula (4), R rHcal150 , R Bcal150is the standard calibration value of infrared light and blue light stored during smoke calibration, APR′ and APB′ are the threshold values ​​of infrared light and blue light when they reach the alarm point (Alarm Point) based on the calibration value. Formula (5) and Formula (6) are comprehensive processing of the degree of scattering of particles by infrared light and blue light. Formula (6) not only considers the possible differences of the smoke alarm itself based on the alarm threshold value determined by the calibration value, but also refers to the difference of 25 valid S values ​​after infrared light and blue light sense smoke to eliminate the difference, and finally determines the alarm point.

[0035] The particle size range of aerosols is determined by the ratio of the detector's dual-wavelength output responses. When the ratio of blue light to infrared light is set to be greater than a fixed value, it is determined to be dust, otherwise it is fire smoke particles. Therefore, combining the detector's blue light and infrared light output responses can effectively identify fire and non-fire aerosols, avoiding false alarms of high-sensitivity detectors caused by large particles interfering with aerosols, and reducing the false alarm rate.

[0036] On this basis, a composite fire detection device with dual-wavelength photoelectric smoke sensors was built, and the fire detection system software was designed. Then, true and false fire source tests were conducted to collect the characteristic parameters of smoke, temperature, and gas changes during the fire. Integrating big data, artificial neural network algorithms were used to integrate and analyze the collected data. A large number of simple processing units were widely connected to form a complex network, which was highly self-learning, self-organizing, and self-adaptive with large-scale parallelism, redundancy, fault tolerance, and nonlinear mapping. Various environmental characteristic parameters detected by multiple sensors were intelligently processed to effectively detect real fire signals.

[0037] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual-wavelength photoelectric smoke detector detection method, characterized in that: According to the Mie scattering model, the intensity of scattered light is related to the particle diameter d, the wavelength λ of the incident light, the refractive index m of the particle medium, the scattering angle θ, and the distance R from the particle to the receiving point. When the particle size is much smaller than the wavelength λ of the incident light, the scattering is in the Rayleigh scattering region. When the particle size is close to the wavelength λ of the incident light, the scattering is in the Mie scattering region. Blue light and infrared light are selected as incident light sources. The refractive index m of the particle medium changes slightly with the wavelength λ of the incident light. It is approximately equal to the light sources of the two wavelengths. The scattering angle θ is constant and the same. The particle size of the fire particles is 1μm or less. The Rayleigh theory is used to analyze the approximate scattered light intensity. The ratio of the blue light scattering intensity and the infrared light scattering intensity of the fire particles in the Rayleigh scattering area is calculated. When the fire particles are in the Mie scattering area, the wavelength of the infrared light is longer, and the small particles scatter the infrared light weakly. However, the small particles have a stronger scattering of the blue light with a shorter wavelength. At this time, the scattered light intensity of the blue light and the infrared light is greater than the ratio of the blue light scattering intensity to the infrared light scattering intensity. The particle size of the interfering particles is much larger than the wavelength of the incident light. They are in the Fraunhofer diffraction area and have a strong scattering effect on both infrared and blue light. The ratio of the scattered light intensity of infrared light and blue light is approximately 1, so it is considered that the scattered light intensity has nothing to do with the wavelength. The air calibration machine and the smoke calibration machine were calibrated to simulate the response of the blue light and infrared light detectors to aerosols of different particle sizes. Data were collected and their ratios were calculated. All simulated data values ​​were smoothed by fitting with the 31-bit least squares estimation method. The simulated values ​​of infrared light and blue light data were recorded as: S r and S b When calibrating the two machines, the calibration values ​​are stored and read in the IC, and the calibration values ​​of infrared light and blue light are processed separately to finally determine the alarm point; The particle size range of the aerosol is determined by the ratio of the dual-wavelength output responses of the detector. When the ratio of blue light to infrared light is greater than a fixed value, it is judged to be dust, otherwise it is fire smoke particles.

2. The dual-wavelength photoelectric smoke detector according to claim 1, characterized in that: When the scattering situation is in the Rayleigh scattering region, the approximate scattered light intensity is: Where I is the total scattered light intensity, I0 is the natural light intensity. It can be seen from formula (1) that the scattered light intensity is inversely proportional to the fourth power of the wavelength of the incident light and is directly proportional to the sixth power of the particle size.

3. The dual-wavelength photoelectric smoke detector according to claim 1, characterized in that: Blue light with a wavelength of 450nm and infrared light with a wavelength of 940nm are selected as the incident light sources.

4. The dual-wavelength photoelectric smoke detector according to claim 3, characterized in that: The ratio of the blue light scattering intensity and the infrared light scattering intensity of fire particles in the Rayleigh scattering region is shown in formula (2): R1=I B1 / I R1 =(1 / 450 4 )×(1 / 940 4 ) -1 ≈19 (2) Where: I B1 is the blue light scattering intensity in the Rayleigh scattering region, I R1 is the infrared light scattering intensity in the Rayleigh scattering region, and R1 is the ratio of the blue light scattering intensity to the infrared light scattering intensity in the Rayleigh scattering region.

5. The dual-wavelength photoelectric smoke detector according to claim 1, characterized in that: Aerosols of different particle sizes included wood, cotton rope, polyurethane, n-heptane, and decalin.

6. The dual-wavelength photoelectric smoke detector according to claim 1, characterized in that: During dual-machine calibration, the calibration values ​​are stored and read in the IC, and the calibration values ​​of infrared light and blue light are processed separately and then synthesized: APR′=116-0.0055*R rHcal150 (3) APB′=106+0.00096*R Bcal150 (4) AP'=APR'+APB' (5) AP=0.75*AP'+0.55*((Sr 25 -Sr1)+(Sb 25 -Sb1)) (6) In formula (3) and formula (4), R rHcal150 , R Bcal150 are the standard calibration values ​​of infrared light and blue light stored during smoke calibration. APR′ and APB′ are the threshold values ​​of infrared light and blue light when they reach the alarm point based on the calibration values. Formula (5) and (6) are comprehensive treatments of the degree of scattering of particulate matter by infrared light and blue light. Formula (6) refers to the difference between 25 valid S values ​​of infrared light and blue light after sensing smoke based on the alarm threshold value determined by the calibration value, and finally determines the alarm point.

Images