Fire smoke detection method and system based on dual wavelengths

Abstract

The invention provides a smoke concentration detection method and system based on dual wavelengths, and the method comprises the steps: a smoke information collection step: transmitting two optical signals with different wavelengths, respectively collecting the light intensity of smoke scattering, and obtaining smoke information corresponding to the two wavelengths; and a smog information processing step: calculating cumulative sums of the two smog information by using a CUSUM algorithm, judging the type of smog according to the ratio of the two cumulative sums, and sending alarm information when the cumulative sums of the two wavelengths exceed a threshold value and meet the alarm smog type. According to the invention, two kinds of light with different wavelengths are adopted to identify smoke, the accuracy and reliability are greatly improved, and when a voltage signal with one kind of wavelength is interfered by an external environment, a false alarm is not generated; water mist interference signals can be distinguished through the detection signals of the two wavelengths.

Description

Technical Field

[0001] The present invention relates to the technical field of fire smoke detection, and in particular to a dual-wavelength-based fire smoke detection method and system. Background Art

[0002] Smoke alarms can be divided into ion smoke alarms and photoelectric smoke alarms based on the sensors they use. Photoelectric smoke alarms are equipped with infrared tubes. When there is no smoke, the infrared receiving tube cannot receive the infrared light emitted by the infrared transmitting tube. When smoke enters, the receiving tube receives the infrared light through refraction and reflection. The intelligent alarm circuit determines whether the threshold is exceeded, and if so, an alarm is sounded.

[0003] In a Chinese patent document with publication number CN107797159A, a smoke detector is disclosed, which includes a circuit board and also includes: an integrated chip, which is arranged on the circuit board, the integrated chip integrates an infrared receiving tube and a microcontroller, and the integrated chip is provided with an infrared receiving window for transmitting infrared signals; an optical darkroom cover, the cover is arranged on the circuit board and encloses the circuit board to form an optical darkroom, and a breathable structure is formed on the optical darkroom cover; and an infrared generating device, which is used to generate infrared light; the infrared generating device is arranged in the optical darkroom.

[0004] Traditional single-wavelength smoke detectors have a single detection signal and are unable to identify interfering particles, which can easily cause the detector to report a false alarm. Summary of the invention

[0005] In view of the defects in the prior art, an object of the present invention is to provide a fire smoke detection method and system based on dual wavelengths.

[0006] A dual-wavelength smoke concentration detection method provided by the present invention includes:

[0007] Smoke information collection steps: emit two light signals of different wavelengths, respectively collect the light intensity scattered by the smoke, and obtain the smoke information corresponding to the two wavelengths;

[0008] Smoke information processing steps: Use the CUSUM algorithm to calculate the cumulative sum of the two types of smoke information respectively, and judge the type of smoke based on the ratio of the two cumulative sums. When the cumulative sum of the two wavelengths exceeds the threshold and meets the alarm smoke type, an alarm message is issued.

[0009] Preferably, in the smoke information collection step, 470 mm wavelength blue light and 940 mm wavelength infrared light are used to detect smoke respectively.

[0010] Preferably, the smoke information collection step includes: emitting two optical signals of different wavelengths in time-sharing manner, collecting the intensity of smoke scattered light through a photodiode, and converting the voltage signal generated by the photodiode into digital information using an ADC, and generating smoke information according to the digital signal.

[0011] Preferably, the smoke information processing step further includes: filtering the two types of smoke information;

[0012] The filtering process includes: using two arrays with a length of 5 to store smoke information of two wavelengths, storing each new value collected at the first position of the array, assigning the data originally at the first position to the second position, and recursively; after each data collection, judging the second position data, if the second position data is much larger than the first position data and much smaller than the third position data, or if the second position data is much smaller than the first position data and much larger than the third position data, then changing the second position data to the average of the first position data and the third position data; outputting the average of the third, fourth, and fifth position data after removing the abnormal value as the filtered data;

[0013] The CUSUM algorithm is used to calculate the cumulative sum of the two types of smoke information after filtering.

[0014] Preferably, the smoke information processing step comprises: substituting the smoke information corresponding to the two wavelengths into the formula:

[0015] C i =max[0,q*C i-1 +x i -K]

[0016] Among them, C i is the CUSUM statistic of the i-th test value, C i-1 is the CUSUM statistic of the i-1th detection value, the initial C0=0; q is the forgetting coefficient, x i is the smoke data of the ith detection; K is the reference value;

[0017] When Ci is greater than the alarm threshold, the type of smoke is determined by the ratio of the cumulative sums of different wavelengths, and an alarm is issued or not according to the type of smoke.

[0018] Preferably, the reference value is adjusted periodically, and the reference value adjustment method includes:

[0019] At regular intervals, the average of several seconds of smoke data is collected as the detection benchmark value. The detection benchmark value is subtracted from the current benchmark value. If the absolute value of the difference is less than a, the benchmark offset value is equal to the difference between the detection benchmark value and the current benchmark value; if the absolute value of the difference is greater than or equal to a, the benchmark offset value is equal to a; the new benchmark value = current benchmark value ± benchmark offset value; the value of a is user-defined.

[0020] Preferably, the method further comprises a fault reminder step: when a fault occurs in the dual-wavelength optical signal transmitter or collector or the reference offset value is greater than a set value, a fault reminder message is issued;

[0021] If a fault reminder message and an alarm message are issued at the same time, the alarm message will be issued first.

[0022] A smoke concentration detection system based on dual wavelengths provided by the present invention comprises:

[0023] Smoke information collection module: emits two light signals of different wavelengths, respectively collects the light intensity scattered by the smoke, and obtains the smoke information corresponding to the two wavelengths;

[0024] Smoke information processing module: Use the CUSUM algorithm to calculate the cumulative sum of the two types of smoke information respectively, and judge the type of smoke based on the ratio of the two cumulative sums. When the cumulative sum of the two wavelengths exceeds the threshold and meets the alarm smoke type, an alarm message is issued.

[0025] According to a dual-wavelength smoke detector provided by the present invention, the dual-wavelength smoke detector executes the dual-wavelength smoke concentration detection method when in operation.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses two different wavelengths of light to identify smoke, which greatly improves accuracy and reliability. When a voltage signal of one wavelength is interfered by the external environment, no false alarm will be generated; the water mist interference signal can be distinguished by the detection signals of the two wavelengths.

[0028] 2. The present invention uses the CUSUM algorithm to amplify the collected abnormal signals, making the fire alarm more timely.

[0029] 3. The present invention adopts an automatic compensation algorithm to reduce the impact of detector differences and environmental changes and improve the reliability of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 It is the hardware flow chart of the dual wavelength fire smoke detection method;

[0032] Figure 2 It is the main function flow chart of the dual-wavelength fire smoke detection method;

[0033] Figure 3It is a flow chart of interruption function of dual wavelength fire smoke detection method;

[0034] Figure 4 This is the effect diagram of the dual-wavelength fire smoke detection method. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0036] The present invention provides a smoke concentration detection method based on dual wavelengths, which can quickly identify different smoke types according to the particle size of the smoke. Compared with the traditional single-wavelength smoke detection method, it has higher reliability and sensitivity. The method has an automatic compensation algorithm that can continuously update the reference value to cope with the influence of factors such as environmental changes, component differences, and original aging.

[0037] Reference Figure 1-Figure 3 As shown, the present invention uses 470nm wavelength blue light and 940nm wavelength infrared to detect smoke particles, and outputs an alarm when the smoke concentration exceeds the alarm threshold. Switch closing signal Specifically, the dual-wavelength fire smoke detection and identification method provided by the present invention comprises the following steps:

[0038] Initialization steps: Initialize the MCU IO port, serial communication, ADC sampling, timer, Flash, watchdog timer and other peripherals, and enable the timer interrupt; substitute the infrared light reference value, blue light reference value, infrared light alarm threshold and blue light alarm threshold; initialize the CUSUM algorithm variables.

[0039] Smoke information collection step: turn on the blue light and infrared light emitting diodes successively, use the photosensitive diodes in the light-shielded smoke chamber to collect the intensity of the scattered light from the smoke, use the ADC to convert the voltage signal generated by the photosensitive diodes into digital information and hand it over to the single-chip microcomputer for processing. In a preferred embodiment, the dual-wavelength light emitting diode is not limited to the above-mentioned specific wavelength lengths, and all wavelength lengths that can be differentiated by different smoke are within the protection scope of this application. The single-chip microcomputer uses the HC32L190 domestically produced low-power single-chip microcomputer as the main control chip.

[0040] In a specific implementation, the collection of smoke information is controlled by executing an interrupt function, such as Figure 3As shown. The program starts the timer interrupt and executes the interrupt function to sample data every 1 second. After the sampling function activates the operational amplifier circuit, it delays for 1ms to wait for the operational amplifier circuit to stabilize. The IO controls the lighting of the 470nm blue LED, delays for 100us to wait for the LED to light up steadily, and starts the ADC conversion to collect the voltage value of the photosensitive diode corresponding to the blue light. After the ADC conversion is completed, the blue LED is turned off and the delay is 1ms again. The IO controls the lighting of the 940nm infrared LED, delays for 100us to wait for the LED to light up steadily, and starts the ADC conversion to collect the voltage value of the photosensitive diode corresponding to the infrared light. After the ADC conversion is completed, the infrared LED is turned off and the operation method circuit is closed.

[0041] Smoke information processing steps: Use the CUSUM algorithm to process the collected smoke information. After filtering the smoke information, calculate the cumulative sum of the smoke information of the two wavelengths separately. Use the ratio of the cumulative sum of the two wavelengths as the distinguishing condition for judging the type of smoke. When the cumulative sum of the two wavelengths exceeds the threshold and meets the alarm smoke type, the alarm flag is set.

[0042] In a specific implementation, the specific method of smoke information filtering is:

[0043] Due to the influence of the external environment, the sampled values ​​may produce jitter or individual abnormal values. The method uses two arrays of length 5, blue[5] and ir[5], to store the data collected at two wavelengths. Each new value collected is stored in the first position of the array, and the data originally in the first position is assigned to the second position. This is repeated recursively to store the data sampling values ​​of the last five times. The second-bit data is judged. If the second-bit data is much larger than the first-bit data and much smaller than the third-bit data, or the second-bit data is much smaller than the first-bit data and much larger than the third-bit data, the second-bit data is changed to the average of the first-bit data and the third-bit data. The average of the 3rd, 4th, and 5th-bit data after removing the abnormal values ​​is output as the filtered data.

[0044] The specific method of using the CUSUM algorithm to determine the type of smoke is:

[0045] Substitute the filtered infrared and blue light smoke data into the formula respectively:

[0046] C i =max[0,q*C i-1 +x i -K]

[0047] Among them, C i is the CUSUM statistic of the i-th test value, C i-1 is the CUSUM statistic of the i-1th detection value, the initial C0=0; q is the forgetting coefficient, x iis the smoke data of the ith detection; K is the reference value.

[0048] The cumulative sum calculation results are as follows Figure 3 As shown, if Ci is greater than the alarm threshold, the detector alarm flag is set. The alarm thresholds for different wavelengths are different. Figure 3 As shown in the figure, when the cumulative sums are greater than 0, the ratio of the blue light cumulative sum to the infrared cumulative sum is used to distinguish the types of smoke. The ratio of blue light to infrared light of fire smoke is greater than that of water vapor.

[0049] Benchmark value compensation steps: Due to factors such as day and night temperature difference, component differences, and component aging, different detectors have certain differences. In the CUSUM smoke recognition detection algorithm, the detection value needs to be subtracted from the benchmark value, and its change is used as the algorithm input. This method compares the difference between the current benchmark value and the detection benchmark value at regular intervals, and stores the difference in the MCU Flash to prevent data loss due to power failure of the detector.

[0050] When the detection data reaches about 1 hour, record 10 seconds of smoke data and take the average as the detection reference value. Subtract the detection reference value from the current reference value. If the absolute value of the difference is less than 5, the reference offset value bias is equal to the difference between the detection reference value and the current reference value. If the detection reference value is greater than the current reference value by more than 5, the reference offset value = current reference value + 5; if the detection reference value is less than the current reference value by more than 5, the reference offset value = current reference value - 5. Initially, bias is 0.

[0051] Alarm output steps: When the detector is in normal operation, the green indicator light flashes, and the detector base does not output a closed conduction signal. When the alarm mark is in position, the red alarm indicator light flashes and the switch closed conduction signal is output.

[0052] The present invention detects three kinds of fault conditions:

[0053] Insufficient power supply voltage for the LED: If the LED voltage value collected through ADC conversion is less than 1.2V, the power supply voltage for the LED is insufficient and the fault flag is set.

[0054] The photodiode detection value is too low: if the ADC conversion value of the photodiode receiving blue light is less than 20 or the ADC conversion value of the photodiode receiving infrared light is less than 50, the fault flag is set.

[0055] The reference value offset is too large: If the upper and lower offsets of the reference value exceed 120, the fault flag is set.

[0056] When the smoke detector is operating normally, the status indicator light flashes green for 50ms every 5s and the detector base pin is disconnected.

[0057] When the alarm flag is in position, the status indicator light changes from a green indicator light flashing 50ms every 5s to a red indicator light flashing 50ms every 1s. The microcontroller controls the IO to output a high level to the detector base, so that the base pin is closed and turned on.

[0058] When the fault flag is set, the status indicator light changes from a green indicator light flashing 50ms every 5s to a yellow indicator light flashing 50ms every 1s. The yellow indicator light is formed by the red indicator light and the green indicator light lighting up at the same time.

[0059] The present invention gives priority to alarms. When the fault flag and the alarm flag are set at the same time, the alarm flag setting program is executed.

[0060] Figure 4 This is the effect diagram of the method. Figure 4 (a) is the blue light filtering effect diagram. Figure 4 (b) is the infrared filtering effect diagram. The solid line is the original sampling data obtained by the interrupt function executing the sampling function, and the dotted line is the data after filtering. By comparison, it can be found that the jitter of the data has been significantly improved, which is conducive to the stable judgment of the smoke alarm.

[0061] Figure 4 (c) is the blue light cumulative sum diagram, Figure 4 (d) is the infrared cumulative sum diagram. The solid line is the input data after filtering, and the dotted line is the output data after CUSUM algorithm calculation. By comparing the numerical values, it can be found that the algorithm amplifies the range of numerical changes after filtering, making the detector more sensitive to smoke changes.

[0062] Figure 4 (e) is the water mist accumulation and comparison diagram. Figure 4 (f) is the cumulative sum comparison of cotton rope smoke. The solid line is the cumulative sum value of blue light, and the dotted line is the cumulative sum value of infrared. It can be found that when the concentration of water mist increases, the cumulative sum value of infrared is higher than the cumulative sum value of blue light. When the concentration of cotton rope smoke increases, the cumulative sum value of infrared is lower than the cumulative sum value of blue light. After calculating the cumulative sum of red and blue light, the ratio of the cumulative sum of red and blue light can be used to distinguish water mist from cotton rope smoke.

[0063] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0064] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0065] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A smoke concentration detection method based on dual wavelengths, characterized in that: include: Smoke information collection steps: emit two light signals of different wavelengths, respectively collect the light intensity scattered by the smoke, and obtain the smoke information corresponding to the two wavelengths; Smoke information processing steps: Use the CUSUM algorithm to calculate the cumulative sum of the two types of smoke information respectively, and judge the type of smoke based on the ratio of the two cumulative sums. When the cumulative sum of the two wavelengths exceeds the threshold and meets the alarm smoke type, an alarm message is issued.

2. The smoke concentration detection method based on dual wavelength according to claim 1 is characterized in that: In the smoke information collection step, 470mm wavelength blue light and 940mm wavelength infrared light are used to detect smoke respectively.

3. The smoke concentration detection method based on dual wavelengths according to claim 1 is characterized in that: The smoke information collection step includes: emitting two optical signals of different wavelengths in time division, collecting the intensity of smoke scattered light through a photodiode, converting the voltage signal generated by the photodiode into digital information through ADC conversion, and generating smoke information according to the digital signal.

4. The smoke concentration detection method based on dual wavelengths according to claim 1 is characterized in that: The smoke information processing step further includes: filtering the two types of smoke information; The filtering process includes: using two arrays with a length of 5 to store smoke information of two wavelengths, storing each new value collected at the first position of the array, assigning the data originally at the first position to the second position, and recursively; after each data collection, judging the second position data, if the second position data is much larger than the first position data and much smaller than the third position data, or if the second position data is much smaller than the first position data and much larger than the third position data, then changing the second position data to the average of the first position data and the third position data; outputting the average of the third, fourth, and fifth position data after removing the abnormal value as the filtered data; The CUSUM algorithm is used to calculate the cumulative sum of the two types of smoke information after filtering.

5. The smoke concentration detection method based on dual wavelengths according to claim 1 is characterized in that: The smoke information processing step includes: respectively substituting the smoke information corresponding to the two wavelengths into the formula: C i =max[0,q*C i-1 +x i -K] Among them, C i is the CUSUM statistic of the i-th test value, C i-1 is the CUSUM statistic of the i-1th detection value, the initial C0=0; q is the forgetting coefficient, x i is the smoke data of the ith detection; K is the reference value; When Ci is greater than the alarm threshold, the type of smoke is determined by the ratio of the cumulative sums of different wavelengths, and an alarm is issued or not according to the type of smoke.

6. The smoke concentration detection method based on dual wavelengths according to claim 5 is characterized in that: The reference value is adjusted regularly, and the reference value adjustment method includes: At regular intervals, the average of several seconds of smoke data is collected as the detection benchmark value. The detection benchmark value is subtracted from the current benchmark value. If the absolute value of the difference is less than a, the benchmark offset value is equal to the difference between the detection benchmark value and the current benchmark value; if the absolute value of the difference is greater than or equal to a, the benchmark offset value is equal to a; the new benchmark value = current benchmark value ± benchmark offset value; the value of a is user-defined.

7. The smoke concentration detection method based on dual wavelengths according to claim 6 is characterized in that: It also includes a fault reminder step: when a fault occurs in the dual-wavelength optical signal transmitter or collector or the reference offset value is greater than a set value, a fault reminder message is issued; If a fault reminder message and an alarm message are issued at the same time, the alarm message will be issued first.

8. A smoke concentration detection system based on dual wavelengths, characterized in that: include: smoke Information collection module: emits two optical signals of different wavelengths, respectively collects the light intensity scattered by smoke, and obtains smoke information corresponding to the two wavelengths; Smoke information processing module: Use the CUSUM algorithm to calculate the cumulative sum of the two types of smoke information respectively, and judge the type of smoke based on the ratio of the two cumulative sums. When the cumulative sum of the two wavelengths exceeds the threshold and meets the alarm smoke type, an alarm message is issued.

9. A smoke detector based on dual wavelengths, wherein the smoke detector performs the smoke concentration detection method based on dual wavelengths as claimed in any one of claims 1 to 7 when in operation.

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