A method to improve the alarm reliability of smoke detectors

Abstract

This invention discloses a method and system for improving the alarm reliability of smoke detectors. The method includes the following steps: S1, setting a background update threshold, an alarm threshold, and an aerosol type threshold. S2, initializing the background value of the smoke detector. S3, periodically updating the detection value. S4, periodically updating the long-cycle background value. S5, updating the short-cycle background value using a threshold method. S6, identifying the aerosol type. S7, alarming for fire smoke. S8, alarming for interfering substances. This invention separates the background value for calculating the aerosol scattered light power ratio from the background value for alarm decision, referring to them as the short-cycle background value and the long-cycle background value, respectively. Different background value update mechanisms are used to adapt to the influence of rapidly changing and slowly changing factors, respectively. Compared to existing methods that rely on the same background value to calculate the aerosol scattered light power ratio and alarm decision, this method can calculate the aerosol scattered light power ratio more accurately.

Description

Technical Field

[0001] This invention relates to the field of fire alarm technology, and specifically to a method for improving the alarm reliability of smoke detectors. Background Technology

[0002] In automatic fire alarm systems, photoelectric smoke detectors are the most widely used fire triggering devices. The basic principle of a photoelectric smoke detector is that when smoke particles in the air enter the detector's maze, the detection light within the maze is scattered and illuminates the phototube, generating an electrical signal. Interfering substances such as water mist, dust, and cooking fumes entering the detector maze can also cause scattering of the detection light, leading to false alarms. To address this problem, the current mainstream solution is to use bidirectional scattering or dual-spectrum detection technology to identify interfering substances and then implement anti-false alarm strategies such as increasing the number of detection cycles and raising the alarm threshold.

[0003] Generally, smoke detectors record a background value, which is the detection value under smoke-free conditions. Aerosol scattered light power can be characterized by the difference between the detector's real-time detection value and the background value. Because the detector's true background value changes slowly due to factors such as dust accumulation in the maze and photocell attenuation, the detector typically updates its background value periodically. To detect slowly developing fires, the background value update frequency should not be too high; a typical update method is once every 4 hours, with the real-time detection value weighted at each update, and an overall update cycle of 32 hours. However, this update method is relatively slow. In scenarios where temperature and humidity change rapidly, such as when air conditioning is on or windows are open for ventilation, the detector's background value will be significantly distorted, leading to large errors in calculating aerosol scattered light power and reducing the reliability of the detector alarm.

[0004] To accurately calculate the aerosol scattered light power ratio, invention patent application CN202110423292.X proposes a smoke detection method with a low false alarm rate. First, a sliding window differentiation method is used to calculate the unit average increment, and then the aerosol scattered light power ratio is calculated using the unit average increment. Essentially, it uses the detection value at a certain time before the current sampling point as the benchmark for calculating the difference. The problem with this method is that when the smoke concentration changes slowly, the small unit average increment can easily lead to large errors. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for improving the alarm reliability of smoke detectors.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for improving the alarm reliability of smoke detectors, applied to smoke detectors with dual-spectrum or bidirectional scattering design, includes the following steps:

[0008] S1. Set the background update threshold, alarm threshold, and aerosol type threshold. The background update threshold includes the long-period background update thresholds for detection optical path A and detection optical path B, respectively denoted as... and and the short-period baseline update threshold, respectively marked as and Alarm thresholds include fire and smoke alarm thresholds. Alarm thresholds for interfering substances Aerosol type thresholds include the scattering power ratio threshold Th for distinguishing aerosol types. r .

[0009] S2. Initialize the background value of the smoke detector.

[0010] S3. Update detection values ​​periodically.

[0011] S4. Update the long-term baseline value periodically.

[0012] S5. Update the short-period background value using the threshold method. Determine the real-time detection value V of the two detection optical paths. A and V B and their respective short-cycle background values and Is the absolute difference greater than the corresponding short-period background update threshold? and If yes, proceed to step S6. Otherwise, update the short-period baseline value. and Then return to step S3.

[0013] S6. Identify the aerosol type. Calculate the aerosol scattered light power ratio 'a' and determine if 'a' is less than Th. r If yes, the aerosol type is identified as fire smoke, proceed to S7. Otherwise, the aerosol type is identified as interfering substance, proceed to S8.

[0014] S7. Fire and smoke alarm. Determine the real-time detection value V of the detection optical path A. A With long-term background update threshold Is the difference greater than the fire smoke alarm threshold? If so, continue to determine the real-time detection value V of the detection optical path B. B Is it greater than the long-term baseline update threshold? If yes, an alarm will be triggered. Otherwise, proceed to S8.

[0015] S8. Alarm for interfering substances. Determine the real-time detection value V of detection optical path A. AWith long-cycle update threshold Is the difference greater than the alarm threshold for interfering substances? If so, an alarm will be triggered.

[0016] As a further aspect of the present invention: step S3 includes: the smoke detector periodically acquiring the photoelectric signal intensity of detection optical path A and detection optical path B, converting them into numerical values, and labeling them as V respectively. A and V B .

[0017] As a further aspect of the present invention: Step S4 includes: periodically acquiring the real-time detection value of the detection optical path, and using the real-time detection value and the historical background value to perform a weighted summation, with the real-time detection value having a weight of 1 / 8 and the historical background value having a weight of 7 / 8.

[0018] As a further aspect of the present invention: in step S6, the calculation formula for a is as follows:

[0019]

[0020] As a further aspect of the present invention: In step S7, if the real-time detection value V of the detection optical path A is... A With long-term background update threshold The difference is not greater than the fire smoke alarm threshold. Then return to step S3.

[0021] As a further aspect of the present invention: In step S8, if the real-time detection value V of the detection optical path A is... A With long-cycle update threshold Is the difference greater than the alarm threshold for interfering substances? Then return to step S3.

[0022] The present invention also discloses a system for improving the alarm reliability of smoke detectors, including a threshold setting module, an initialization module, a detection module, a background value update module, an aerosol identification module, and an alarm module.

[0023] The threshold setting module is used to set the background update threshold, alarm threshold, and aerosol type threshold.

[0024] The initialization module is used to initialize the baseline value.

[0025] The detection module is used to update the detection values ​​periodically.

[0026] The background value update module is used to update long-period background values ​​and short-period background values.

[0027] Aerosol identification module, which is used to identify aerosol types.

[0028] The alarm module is used to issue alarms for fire smoke and interfering substances.

[0029] This invention has at least one of the following beneficial effects:

[0030] (1) The method described in this invention separates the background value for calculating the aerosol scattered light power ratio from the background value for decision alarm, which are referred to as the short-cycle background value and the long-cycle background value, respectively. Different background value update mechanisms are adopted to adapt to the influence of rapidly changing factors and slowly changing factors, respectively. Compared with the existing method that relies on the same background value to calculate the aerosol scattered light power ratio and decision alarm, the method can calculate the aerosol scattered light power ratio more accurately and the identification result is more reliable.

[0031] (2) The method described in this invention adopts a short-period background value update method based on threshold judgment. Compared with existing methods such as sliding window differentiation, it occupies less storage space and can accurately calculate the aerosol scattered light power ratio for slow-developing fire smoke, resulting in higher reliability of the identification results.

[0032] (3) The method described in this invention takes into account the signal strength change trend of the two detection optical paths of the detector when making fire alarm decisions. When the change trends of the two detection values ​​are inconsistent, the alarm threshold is increased and alarm is triggered according to the interfering substance. This can effectively reduce the false fire alarms caused by condensation inside the maze. Attached Figure Description

[0033] The invention will now be further described with reference to the accompanying drawings.

[0034] Figure 1 This is a flowchart illustrating the method for improving the alarm reliability of smoke detectors according to the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Please see Figure 1 As shown, the present invention is a method for improving the alarm reliability of smoke detectors, which is applied to smoke detectors with dual-spectrum or bidirectional scattering design. Specifically, the smoke detector includes two detection optical paths. The detection optical path with smaller changes in detection value under smoke-free conditions when ambient temperature, humidity and other conditions change is marked as A, and the other detection optical path is marked as B.

[0037] The method includes the following steps:

[0038] S1. Set the background update threshold, alarm threshold, and aerosol type threshold. The background update threshold includes the long-period background update thresholds for detection optical path A and detection optical path B, respectively denoted as... and and the short-period baseline update threshold, respectively marked as and Alarm thresholds include fire and smoke alarm thresholds. Alarm thresholds for interfering substances Aerosol type thresholds include the scattering power ratio threshold Th for distinguishing aerosol types. r .

[0039] S2. Initialize the background value of the smoke detector. The initialized background value includes the long-period background value of detection optical path A and detection optical path B, denoted as... and And the short-cycle background value, marked as and The method for initializing the background value can be to use the detection value stored in the smoke detector under smoke-free conditions as the initial value.

[0040] S3. Periodically update the detection values. The updated detection values ​​refer to the periodic acquisition of photoelectric signal intensity from detection optical paths A and B by the smoke detector, converting it into numerical values, and labeling them as V. A and V B .

[0041] S4. Periodically update the long-period background value. The long-period background value includes the long-period background value of the detection optical path A. The long-period background value of detection optical path B The long-term baseline value is updated at a low frequency and with a small magnitude. The typical update method is to update it once every 4 hours. The real-time detection value and the historical baseline value are weighted and summed, with the real-time detection value having a weight of 1 / 8 and the historical baseline value having a weight of 7 / 8.

[0042] S5. Update the short-period background value using the threshold method. Determine the real-time detection value V of the two detection optical paths. A and V B and their respective short-cycle background values and Is the absolute difference greater than the corresponding short-period background update threshold? and If yes, proceed to step S6. Otherwise, update the short-period baseline value. and Then return to step S3.

[0043] S6. Identify the aerosol type. Calculate the aerosol scattered light power ratio 'a' and determine if 'a' is less than Th.r If yes, the aerosol type is identified as fire smoke, proceed to S7. Otherwise, the aerosol type is identified as interfering substance, proceed to S8. The formula for calculating 'a' is as follows:

[0044]

[0045] S7. Fire and smoke alarm. Determine the real-time detection value V of the detection optical path A. A With long-term background update threshold Is the difference greater than the fire smoke alarm threshold? If so, continue to determine the real-time detection value V of the detection optical path B. B Is it greater than the long-term baseline update threshold? If yes, an alarm will sound. Otherwise, proceed to step S8. If the real-time detection value V of optical path A is detected... A With long-term background update threshold The difference is not greater than the fire smoke alarm threshold. Then return to step S3.

[0046] S8. Alarm for interfering substances. Determine the real-time detection value V of detection optical path A. A With long-cycle update threshold Is the difference greater than the alarm threshold for interfering substances? If so, an alarm will be triggered. If the real-time detection value V of optical path A is detected... A With long-cycle update threshold Is the difference greater than the alarm threshold for interfering substances? Then return to step S3.

[0047] The method described in this invention separates the background value for calculating the aerosol scattered light power ratio from the background value for decision alarm, referring to them as the short-period background value and the long-period background value, respectively. Different background value update mechanisms are used to adapt to the influence of rapidly changing factors and slowly changing factors, respectively. Compared with the existing method that relies on the same background value to calculate the aerosol scattered light power ratio and decision alarm, this method can calculate the aerosol scattered light power ratio more accurately and the identification results are more reliable.

[0048] The method described in this invention adopts a short-period background value update method based on threshold judgment. Compared with existing methods such as sliding window differentiation, it occupies less storage space and can accurately calculate the aerosol scattered light power ratio for slow-developing fire smoke, resulting in higher reliability of the identification results.

[0049] The method described in this invention takes into account the signal strength change trends of the two detection optical paths of the detector when making fire alarm decisions. When the change trends of the two detection values ​​are inconsistent, the alarm threshold is increased and alarm is triggered according to the interference substance, which can effectively reduce false fire alarms caused by condensation inside the maze.

[0050] The present invention also discloses a system for improving the alarm reliability of smoke detectors, including a threshold setting module, an initialization module, a detection module, a background value update module, an aerosol identification module, and an alarm module.

[0051] The threshold setting module is used to set the background update threshold, alarm threshold, and aerosol type threshold.

[0052] The initialization module is used to initialize the baseline value.

[0053] The detection module is used to update the detection values ​​periodically.

[0054] The background value update module is used to update long-period background values ​​and short-period background values.

[0055] Aerosol identification module, which is used to identify aerosol types.

[0056] The alarm module is used to issue alarms for fire smoke and interfering substances.

[0057] This system has the same beneficial effects as the methods described above, and will not be elaborated further here.

[0058] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for improving the alarm reliability of a smoke detector, applied to a smoke detector of dual-spectrum or dual-scattering design, characterized in that, The method comprises the following steps: S1, setting a background update threshold, an alarm threshold and an aerosol type threshold; the background update threshold includes long-period background update thresholds of detection light path A and detection light path B, respectively marked as and , and short-period background update thresholds, respectively marked as and ; the alarm threshold includes a fire smoke alarm threshold and an alarm threshold of interfering substances ; the aerosol type threshold includes a scattering power ratio threshold for distinguishing aerosol categories ; S2, initializing the background value of the smoke detector; S3, periodically updating the detection value; S4, periodically updating the long-period background value; S5, updating the short period background value according to threshold method; judging whether the absolute difference between the real-time detection values of the two detection light paths is greater than the corresponding short period background updating threshold and and the corresponding short period background value and of each other and If yes, entering step S6; otherwise, updating the short period background value and and returning to step S3; S6, identify the aerosol type; calculate the aerosol scattering light power ratio a, and determine whether a is less than If yes, identify the aerosol type as fire smoke, and enter S7; otherwise, identify the aerosol type as an interfering substance, and enter S8; S7, alarming the fire smoke; Determine the real-time detection value of detection optical path A. With long-term background update threshold Is the difference greater than the fire smoke alarm threshold? If so, continue to determine the real-time detection value of detection optical path B. Is it greater than the long-term baseline update threshold? If yes, an alarm will be triggered; otherwise, proceed to S8. S8, alarm of the interfering substance; judging the real-time detection value of the detection light path A whether the difference between the long-period update threshold value and the short-period update threshold value is greater than the alarm threshold value of the interfering substance is, alarm.

2. The method of claim 1, wherein the method further comprises: In step S2, the detection value of the smoke detector in the smoke-free state is stored as an initial background value; wherein the initial background value includes long-period background values of the initialization detection light path A and the detection light path B, respectively marked as and , and short-period background values, respectively marked as and .

3. The method of claim 1, wherein the method further comprises: The process of step S3 includes: the smoke detector regularly collects the photoelectric signal intensity of the detection light path A and the detection light path B, and converts it into a numerical value, respectively marked as and .

4. The method of claim 1, wherein the method further comprises: The process of step S4 comprises: periodically acquiring the real-time detection value of the detection light path, and performing weighted summation on the real-time detection value and the historical background value, wherein the weight of the real-time detection value is 1 / 8, and the weight of the historical background value is 7 / 8.

5. The method of claim 1, wherein the method further comprises: In step S6, the calculation formula of a is as follows: 。 6. The method of claim 1, wherein the method further comprises: In step S7, if the real-time detection value of the detection light path A is not greater than the difference between the long-period background update threshold value and the fire smoke alarm threshold value by a value not greater than the fire smoke alarm threshold value , then return to step S3. .

7. The method of claim 1, wherein the method further comprises: In step S8, if the real-time detection value of the detection light path A is not greater than the difference between the long-period update threshold value and the alarm threshold value of the interfering substance , the process returns to step S3. ​​ 8. A system for improving the alarm reliability of a smoke fire detector as claimed in claim 1, wherein, The method comprises the following steps: a threshold setting module for setting a background update threshold, an alarm threshold and an aerosol type threshold; an initialization module for initializing the background value; a detection module for periodically updating the detection value; a background value updating module for updating the long-period background value and the short-period background value; an aerosol identification module for identifying the aerosol type; and an alarm module for alarming the fire smoke and the interfering substance.

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