A method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotational characteristics

Abstract

This invention discloses a method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotational characteristics, belonging to the field of intelligent monitoring of fire protection facilities. The invention employs an intelligent fire hydrant cover that can directly replace the original cover. An initial attitude calibration is performed to obtain a baseline attitude. The device intermittently samples in a low-power mode. When the attitude change exceeds a preset threshold, an interrupt is triggered to wake the CPU, switching to high-frequency sampling to extract continuous rotational characteristics such as angle changes between adjacent sampling points, consistency of rotation direction, number of effective changes, cumulative attitude offset, and attitude stability. After interference elimination confirms illegal dismantling, an alarm is triggered, and GPS / BeiDou positioning and three-axis attitude characteristics are uploaded to the cloud via 4G / NB-IoT. Once reverse rotation is detected and the attitude returns to the baseline and stabilizes, a recovery event is generated to complete the closed loop. This invention achieves accurate alarms with low false alarm rate, low power consumption, and support for recovery confirmation through continuous rotational feature recognition and low-power high-frequency tracking, and is easy to install.

Description

Technical Field

[0001] This invention relates to the field of intelligent monitoring technology for fire protection facilities, and in particular to a method for identifying illegal dismantling of fire hydrants based on the continuous rotation characteristics of three-axis attitude. Background Technology

[0002] Fire hydrants are core infrastructure for urban public fire safety. Their proper installation and normal operation are key prerequisites for emergency water supply during fires. Illegal dismantling and unauthorized use of fire hydrants not only cause the loss of public water resources, but also lead to the failure of fire-fighting facilities. In the event of a sudden fire, they will be unable to supply water normally, which can easily lead to major safety accidents. Therefore, monitoring and accurate alarm for illegal dismantling of fire hydrants has become an important part of the operation and maintenance management of urban fire-fighting facilities.

[0003] Currently, various existing technical solutions have been developed in the field of fire hydrant anti-theft and anti-dismantling monitoring. Some solutions use mechanical switches and displacement switches as monitoring triggers to determine whether the hydrant is being opened or disassembled based on the on / off status of the components. Other solutions rely on a single tilt angle threshold and instantaneous vibration intensity to achieve anomaly detection. Still others combine IoT communication technologies such as NB-IoT and 4G with positioning modules to achieve remote uploading of alarm information and location tracking. Although the above-mentioned existing technologies can achieve basic functions such as alarms for opening, tilting, and impact, as well as remote reporting, they have many technical drawbacks that are difficult to overcome in practical applications.

[0004] Most existing monitoring solutions rely solely on instantaneous state parameters or single threshold exceedances as alarm criteria, lacking the ability to identify the sequential characteristics of continuous, unidirectional, and progressive rotational movements unique to illegal fire hydrant dismantling. This makes it difficult to effectively distinguish between genuine dismantling activities and short-term environmental disturbances such as vehicle collisions, construction vibrations, water flow impacts, and ground subsidence, leading to high false alarm rates and significant missed alarm risks. Furthermore, existing equipment generally employs long-term, high-frequency sampling and continuous communication, resulting in high overall power consumption, making it unsuitable for battery-powered, long-term unattended outdoor deployments. This also limits equipment lifespan and large-scale application. In addition, traditional monitoring solutions often require additional drilling, wiring, or structural modifications to the fire hydrant itself, leading to complex installation processes, inconvenient maintenance, and high modification costs, hindering rapid adaptation to the large-scale upgrade and deployment needs of existing fire hydrants. Moreover, existing equipment can only upload basic anomaly information after an alarm, lacking complete three-axis attitude feature data and precise positioning information. It does not support event verification, on-site tracking, or full-process platform management, failing to meet the actual needs of intelligent supervision of modern fire protection facilities. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for identifying illegal dismantling of fire hydrants based on the continuous rotation characteristics of three-axis attitude, which solves the problems of existing technologies being unable to identify the real dismantling process from a time series, high risk of false alarms and missed alarms, lack of multi-stage confirmation mechanism, and high power consumption.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics is provided, including the following steps:

[0008] S1. After replacing the intelligent fire hydrant cap with the fire hydrant cap, send an attitude calibration command to the device, collect the three-axis attitude data of the device in a static state, and use it as the reference attitude.

[0009] S2. The device samples intermittently in low-power mode. The three-axis attitude sensor monitors attitude changes in real time. When the attitude change exceeds the preset interrupt threshold, the attitude sensor triggers an interrupt and wakes up the CPU control unit.

[0010] S3. After the CPU is woken up, it determines that the current attitude change meets the valid attitude change conditions, and then enters the suspected disassembly tracking state, switches low-frequency sampling to high-frequency sampling, and continuously collects three-axis attitude data.

[0011] S4. Under high-frequency sampling, extract the angle change of adjacent sampling points, the consistency of rotation direction, the number of effective attitude changes, and the cumulative attitude offset, and make a final attitude stability judgment.

[0012] S5. Based on the continuous rotation feature, interference is eliminated. If the disassembly judgment condition is met, illegal disassembly is confirmed and an alarm is triggered.

[0013] S6. After the alarm is triggered, the positioning module is activated to obtain location information and the alarm data, three-axis attitude characteristics and positioning information are uploaded to the cloud platform through the Internet of Things network.

[0014] S7. Continuously monitor attitude data. Once reverse rotation is detected and the attitude is restored to the reference attitude and maintained stably, a recovery event is generated and uploaded to the cloud.

[0015] Preferably, the preset interruption threshold in step S2 is: the acceleration change of any axis exceeds 0.15g to 0.30g, or the comprehensive attitude angle change obtained by converting the three-axis acceleration exceeds 8° to 15°.

[0016] Preferably, the sampling period in the low-power mode in step S2 is 2 seconds; the sampling period in the high-frequency sampling in step S3 is 200 milliseconds; the preset tracking window for the suspected disassembly tracking state is 5 to 30 seconds. If the continuous rotation condition is not met within the preset tracking window, the high-frequency sampling is exited and the low-frequency sampling in the low-power mode is restored.

[0017] Preferably, in step S4, a three-dimensional coordinate system O-XYZ is established with the center of the fire hydrant cap or the center of the cap tail as the origin O; wherein the X-axis is set radially along the cap, the Y-axis is set tangentially along the cap, and the Z-axis is set axially along the cap and perpendicular to the cap mounting plane; the three-axis attitude sensor coordinate system is fixedly corresponding to the cap coordinate system, or a coordinate transformation relationship is established through initial calibration.

[0018] Preferably, in step S4, the pitch angle P and roll angle R are calculated using triaxial acceleration data, and the calculation formula is as follows:

[0019]

[0020]

[0021] in, The acceleration data are for the X, Y, and Z axes, respectively; and the pitch angle change dP and roll angle change dR between adjacent sampling points are calculated, along with the combined angle change. Overall attitude offset , This represents the offset of the pitch angle relative to the reference attitude. This represents the offset of the roll angle relative to the reference attitude.

[0022] Preferably, the rules for determining effective attitude changes and effective rotational actions in step S4 are as follows: θ ≥ 5° is recorded as an effective attitude change; θ ≥ 20° or the cumulative angle change within a number of consecutive sampling points ≥ 20° is recorded as an effective rotational action; and the main change axis is determined by the larger component of |dP| and |dR|; when the angle change direction of the main change axis is consistent with the first effective attitude change direction, it is recorded as a change in the same direction, and when they are opposite, it is recorded as a change in the opposite direction; an angle change less than the effective change threshold is an invalid change.

[0023] Preferably, the disassembly determination conditions in step S5 include: within a preset sampling window, the number of unidirectional changes is ≥3 times, the total number of effective posture changes is ≥4 times, the number of reverse changes is ≤1 time or the proportion of reverse changes is less than 40%, and the comprehensive posture offset φ is ≥35°, confirming that the fire hydrant cover has the characteristic of continuous rotational disassembly; and, the stability of the cumulative posture offset of the most recent 8 sampling data is judged, and when the fluctuation range is less than 5° and the posture has not recovered to the reference posture, it is finally confirmed that illegal disassembly has occurred.

[0024] Preferably, the interference elimination rule in step S5 is as follows: in the suspected disassembly tracking state, if the three-axis attitude change is manifested as short-term impact, random drastic change, excessive reverse change or insufficient cumulative rotation, it is determined to be environmental interference, the suspected disassembly state is canceled and the tracking cache is cleared, and the false alarm information is filtered.

[0025] Preferably, in step S6, the positioning module is a GPS or Beidou positioning module, and the Internet of Things network is a 4G or NB-IoT network; the uploaded data includes device number, alarm type, alarm time, maximum rotation amplitude, number of same-direction changes, number of reverse-direction changes, battery voltage, and positioning information.

[0026] Preferably, the three-axis attitude sensor is any one of a three-axis accelerometer, a six-axis IMU, or a nine-axis IMU; when a six-axis IMU or a nine-axis IMU is used, the Z-axis rotation change is included in the main change axis judgment; the disassembly recovery confirmation condition in step S7 is: a rotational change opposite to the disassembly process is detected, and within a preset time window, the device attitude is continuously and stably maintained within the allowable error range of the reference attitude multiple times.

[0027] The beneficial effects of this invention are:

[0028] This invention provides a method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics. Through an intelligent cover device with a built-in three-axis attitude sensor, it significantly reduces device power consumption and extends battery life by combining low-power interrupt wake-up with high-frequency tracking of suspected dismantling. By extracting multi-dimensional continuous rotation characteristics such as angle changes between adjacent sampling points, rotation direction consistency, effective attitude change counts, cumulative attitude offset, and final attitude stability, and combining these with the same / opposite direction change counts, cumulative rotation window, and multi-stage stability judgment, it can accurately distinguish between genuine dismantling behavior and environmental interference such as vehicle collisions, construction vibrations, and water flow impacts, effectively overcoming the shortcomings of existing technologies with high false alarm rates and high risk of missed alarms. Simultaneously, it achieves alarm information and attitude characteristic reporting via network and pioneers a closed-loop recovery confirmation mechanism based on reverse rotation detection and baseline attitude recovery, realizing intelligent management of the entire process from dismantling alarm and on-site tracking to reinstallation confirmation. Attached Figure Description

[0029] Figure 1 This is a flowchart of a method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation features, according to the present invention.

[0030] Figure 2 This is a physical image of the intelligent fire hydrant cover of the present invention. Detailed Implementation

[0031] 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.

[0032] The fire hydrant illegal dismantling identification method based on three-axis attitude continuous rotation characteristics described in this invention is achieved through an intelligent fire hydrant cap device that can directly replace the original fire hydrant cap. This device has a built-in three-axis attitude sensor, CPU control unit, positioning module, communication module and battery power supply module. It does not require drilling, wiring or structural modification of the fire hydrant and can be directly replaced and installed, making it suitable for large-scale deployment of existing fire hydrants.

[0033] Example 1

[0034] Combined with appendix Figure 1 The specific steps of the fire hydrant illegal dismantling identification method based on three-axis attitude continuous rotation characteristics in this embodiment are as follows:

[0035] S1, Initial Attitude Calibration

[0036] The intelligent fire hydrant cap is replaced and installed at the standard fire hydrant interface. After the device is stationary and stable, an attitude calibration command is sent to the device via the cloud platform, Bluetooth near-field communication, or local debugging port. The device collects the raw triaxial acceleration data in the current stationary state, calculates the pitch angle and roll angle, and sets the attitude data as the reference attitude for subsequent attitude changes and disassembly behavior.

[0037] S2, Low-power intermittent attitude sampling

[0038] Under normal conditions, the device operates in a low-power mode. The three-axis attitude sensor maintains a low-power monitoring state, performing low-frequency intermittent sampling with a 2-second cycle. When the attitude change exceeds a preset interrupt threshold, the attitude sensor triggers an interrupt and wakes up the CPU control unit. In this embodiment, the preset interrupt threshold is: the change in acceleration of any axis exceeds 0.2g (selectable range 0.15g~0.30g), or the change in the overall attitude angle converted from the three-axis acceleration exceeds 10° (selectable range 8°~15°). When the attitude change exceeds the above threshold, the three-axis accelerometer outputs an external interrupt signal through the input / output port to wake up the CPU control unit. Small attitude changes are judged as slight vibrations, water flow impacts, and other environmental interferences, which are directly filtered out, allowing the device to maintain a low-power state for a long time. In low-power mode, the device performs low-frequency intermittent sampling with a 2-second cycle.

[0039] S3, Suspected disassembly tracking and sampling frequency switching

[0040] During normal operation, the device samples the attitude data of the three-axis attitude sensor at a low-frequency 2-second sampling period. When the CPU control unit receives an interrupt request triggered by the attitude sensor, the device first determines whether the current attitude change meets the valid attitude change conditions. When the comprehensive angle change reaches a preset threshold, it enters a suspected disassembly tracking state. After the CPU control unit enters the suspected disassembly tracking state, the low-frequency sampling period will be temporarily switched from the original 2-second sampling period to a 200ms high-frequency sampling period (i.e., 5 times of three-axis attitude data are collected per second) for continuous sampling and tracking of rotation direction, angle change, and attitude stability during the disassembly process. At the same time, a preset tracking window timer is started, which is set to 10 seconds in this embodiment (selectable range 5 seconds to 30 seconds). If the continuous rotation condition is not met within the preset tracking window, the device exits the high-frequency sampling state and returns to the low-frequency 2-second sampling or low-power interrupt monitoring state.

[0041] S4. Continuous Rotation Feature Sampling Extraction

[0042] Under suspected disassembly tracking conditions, the device continuously collects triaxial acceleration and attitude data at a high-frequency sampling period of 200ms, and establishes a three-dimensional coordinate system O-XYZ with the center of the fire hydrant cover or the center of the cover tail as the coordinate origin O; wherein the X-axis is set along the radial direction of the cover, the Y-axis is set along the tangential direction of the cover, and the Z-axis is along the axial direction of the cover and perpendicular to the cover mounting plane; the triaxial attitude sensor is fixedly installed inside the cover, and its sensor coordinate system maintains a fixed correspondence with the cover coordinate system, or a coordinate transformation relationship is established through initial calibration;

[0043] Acceleration data collected at each sampling point t ( The real-time attitude angle is calculated using triaxial acceleration data. The calculation formula is as follows:

[0044]

[0045]

[0046] The offset of the pitch angle relative to the reference attitude: The offset of the roll angle relative to the reference attitude: Change in pitch angle between adjacent sampling points: The change in roll angle between adjacent sampling points: d Comprehensive angle change Overall attitude offset ,in, These are the acceleration data for the X, Y, and Z axes, respectively.

[0047] when A change of ≥5° is considered a valid attitude change; A rotation is defined as an action with a change of ≥20° or a cumulative angle change of ≥20° within a series of consecutive sampling points; and is defined as follows: and The larger component determines the principal change axis; when the direction of the angle change of the principal change axis is consistent with the direction of the first effective attitude change, it is recorded as a change in the same direction, and when they are opposite, it is recorded as a change in the opposite direction. An angle change amount less than the effective change threshold is recorded as an invalid change.

[0048] Within the preset sampling window, if the number of unidirectional changes is ≥3, the total number of effective attitude changes is ≥4, the number of reverse changes is ≤1 or the proportion of reverse changes is less than 40%, and the comprehensive attitude offset φ is ≥35°, it is confirmed that the fire hydrant cap has the characteristic of continuous rotational disassembly. Furthermore, the stability of the cumulative attitude offset of the most recent 8 sampling data is judged. When the fluctuation range is less than 5° and the attitude has not recovered to the vicinity of the reference attitude, the final attitude is considered stable, and it is confirmed that an illegal disassembly event has occurred in the fire hydrant.

[0049] S5. Interference Elimination and Final Confirmation

[0050] During suspected disassembly tracking, if the three-axis attitude changes manifest as short-term impacts, random and drastic changes, excessive reverse changes (e.g., reverse changes account for ≥40%), or insufficient cumulative rotation (…), the following situations should be noted: If the anomaly is detected, it is determined that the anomaly may be caused by factors such as vehicle collision, construction vibration, water flow impact, or ground subsidence. The equipment is deactivated from the suspected disassembly status, the tracking cache is cleared, and the false alarm information is filtered out.

[0051] When the number of changes in the same direction, the total number of effective changes, the maximum angular offset, and the final attitude stability all meet the preset conditions, the equipment determines that an illegal disassembly event has occurred in the fire hydrant and generates a disassembly alarm.

[0052] S6, Location and Communication Reporting

[0053] After the alarm is triggered, the device generates an alarm event and simultaneously activates the GPS / BeiDou positioning module to obtain the current location. It then uploads the device number, alarm type, alarm time, three-axis attitude data, maximum rotation amplitude, number of same-direction changes, number of reverse-direction changes, battery voltage, and location information to the cloud platform via a 4G or NB-IoT network.

[0054] S7. Disassembly, alarm recovery, and reinstallation confirmation

[0055] Even after the equipment triggers an illegal disassembly alarm, it will still monitor the three-axis attitude data. When a rotational change in the opposite direction to the disassembly process is detected, and the current three-axis attitude gradually recovers to near the initial calibrated reference attitude, the equipment enters the recovery confirmation state.

[0056] If the device's attitude remains consistently within the allowable error range of the baseline attitude for multiple consecutive times within a preset time window, it is determined that the fire hydrant cover device has been reinstalled or the disassembly alarm has been cleared, and a disassembly recovery event is generated. The device uploads the recovery time, the recovered three-axis attitude data, battery voltage, and positioning information to the cloud platform via a 4G or NB-IoT network, achieving closed-loop management of alarm triggering, recovery confirmation, and platform recording.

[0057] It should be noted that in alternative implementations using a six-axis or nine-axis IMU, the yaw angle change dY around the Z-axis can be further calculated and incorporated into the main change axis determination. When When the component with the largest change and the continuous change direction are consistent, it can be directly determined that there is a rotational feature around the Z-axis in the same direction.

[0058] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotational characteristics, characterized in that, Includes the following steps: S1. After replacing the intelligent fire hydrant cap with the fire hydrant cap, send an attitude calibration command to the device, collect the three-axis attitude data of the device in a static state, and use it as the reference attitude. S2. The device samples intermittently in low-power mode. The three-axis attitude sensor monitors attitude changes in real time. When the attitude change exceeds the preset interrupt threshold, the attitude sensor triggers an interrupt and wakes up the CPU control unit. S3. After the CPU is woken up, it determines that the current attitude change meets the valid attitude change conditions, and then enters the suspected disassembly tracking state, switches low-frequency sampling to high-frequency sampling, and continuously collects three-axis attitude data. S4. Under high-frequency sampling, extract the angle change of adjacent sampling points, the consistency of rotation direction, the number of effective attitude changes, and the cumulative attitude offset, and make a final attitude stability judgment. S5. Based on the continuous rotation feature, interference is eliminated. If the disassembly judgment condition is met, illegal disassembly is confirmed and an alarm is triggered. S6. After the alarm is triggered, the positioning module is activated to obtain location information and the alarm data, three-axis attitude characteristics and positioning information are uploaded to the cloud platform through the Internet of Things network. S7. Continuously monitor attitude data. Once reverse rotation is detected and the attitude is restored to the reference attitude and maintained stably, a recovery event is generated and uploaded to the cloud.

2. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 1, characterized in that, The preset interruption threshold in step S2 is: the acceleration change of any axis exceeds 0.15g to 0.30g, or the comprehensive attitude angle change calculated from the three-axis acceleration exceeds 8° to 15°.

3. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 1, characterized in that, In step S2, the sampling period in low-power mode is 2 seconds; in step S3, the sampling period in high-frequency sampling is 200 milliseconds; the preset tracking window for the suspected disassembly tracking state is 5 to 30 seconds. If the continuous rotation condition is not met within the preset tracking window, high-frequency sampling is exited and low-frequency sampling in low-power mode is restored.

4. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 1, characterized in that, In step S4, a three-dimensional coordinate system O-XYZ is established with the center of the fire hydrant cover or the center of the cover tail as the coordinate origin O; wherein the X-axis is set along the radial direction of the cover, the Y-axis is set along the tangential direction of the cover, and the Z-axis is set along the axial direction of the cover and perpendicular to the cover mounting plane; the three-axis attitude sensor coordinate system is fixedly corresponding to the cover coordinate system, or the coordinate transformation relationship is established through initial calibration.

5. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 4, characterized in that, In step S4, the pitch angle P and roll angle R are calculated using triaxial acceleration data. The calculation formula is as follows: in, The acceleration data are for the X, Y, and Z axes, respectively; and the pitch angle change dP and roll angle change dR between adjacent sampling points are calculated, along with the combined angle change. Overall attitude offset , This represents the offset of the pitch angle relative to the reference attitude. This represents the offset of the roll angle relative to the reference attitude.

6. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 5, characterized in that, The rules for determining effective attitude changes and effective rotational movements in step S4 are as follows: This is recorded as one effective attitude change; Or, a cumulative angle change of ≥20° within a series of consecutive sampling points is recorded as one valid rotation action; and is... and The larger component determines the principal change axis; when the angle change direction of the principal change axis is consistent with the first effective attitude change direction, it is recorded as a change in the same direction, and when they are opposite, it is recorded as a change in the opposite direction. An angle change amount less than the effective change threshold is an invalid change.

7. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 6, characterized in that: The disassembly determination criteria in step S5 include: within a preset sampling window, the number of unidirectional changes is ≥3, the total number of effective attitude changes is ≥4, the number of reverse changes is ≤1 or the proportion of reverse changes is less than 40%, and the overall attitude offset is... ≥35°, confirming that the fire hydrant cap has the characteristic of continuous rotational disassembly; and, the stability of the cumulative attitude deviation of the most recent 8 sampling data is judged. When the fluctuation range is less than 5° and the attitude has not returned to the reference attitude, it is finally confirmed that illegal disassembly has occurred.

8. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 1, characterized in that: The interference elimination rule in step S5 is as follows: in the suspected disassembly tracking state, if the three-axis attitude change is manifested as short-term impact, random drastic change, excessive reverse change or insufficient cumulative rotation, it is determined to be environmental interference, the suspected disassembly state is canceled and the tracking cache is cleared, and the false alarm information is filtered.

9. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 1, characterized in that: In step S6, the positioning module is a GPS or Beidou positioning module, and the Internet of Things network is a 4G or NB-IoT network; the uploaded data includes device number, alarm type, alarm time, maximum rotation amplitude, number of same-direction changes, number of reverse-direction changes, battery voltage, and positioning information.

10. The method for identifying illegal dismantling of fire hydrants based on three-axis continuous rotation characteristics as described in claim 1, characterized in that: The three-axis attitude sensor can be any one of a three-axis accelerometer, a six-axis IMU, or a nine-axis IMU. When a six-axis IMU or a nine-axis IMU is used, the Z-axis rotation change is included in the main change axis judgment. The disassembly recovery confirmation condition in step S7 is: a rotational change opposite to the disassembly process is detected, and within a preset time window, the device attitude is continuously and stably maintained within the allowable error range of the reference attitude multiple times.

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