A manhole cover state monitoring method based on hall effect and non-contact distance measurement

Abstract

This invention provides a method for monitoring the status of manhole covers based on the Hall effect and non-contact ranging. The method includes controlling the monitoring device of the manhole cover to enter standby mode, sensing changes in the magnetic field strength of a magnet on the manhole cover through a Hall effect switch element; when the switching state of the Hall effect switch element changes, controlling the monitoring device to switch to wake-up mode, determining whether the wake-up event of the Hall effect switch element is a valid event; if the wake-up event is valid, controlling the monitoring device to switch to ranging mode, measuring the distance between the monitoring device and the signal reflector of the manhole cover through a ranging element on the monitoring device, and determining the status of the manhole cover based on the measured distance; if the wake-up event is invalid, controlling the monitoring device to switch back to standby mode. The advantages of this invention are: it can effectively reduce the occurrence of false alarms and missed alarms, and can reduce unnecessary power consumption, thereby extending the service life of the monitoring device.

Description

[Technical Field]

[0001] This invention relates to the field of manhole cover technology, and in particular to a method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging. [Background Technology]

[0002] Manhole covers are used to cover deep wells in roads or homes to prevent people or objects from accidentally falling in. To ensure the safety of manhole covers, monitoring devices are usually installed on them so that alarm information can be generated and reported in a timely manner in case of loss or movement of the manhole cover.

[0003] Traditional manhole cover monitoring devices typically use gyroscopes and magnetic door switches as sensors to identify the manhole cover's status (open, closed, etc.). For example, Chinese utility model patent application CN202123353778.5 discloses an intelligent manhole cover with a gyroscope inside the cover's cavity; another example is Chinese utility model patent application CN202121006616.1, which uses a magnetic door switch to implement an alarm function. However, in actual operation, manhole cover monitoring devices operate in harsh environments (such as high temperature, high humidity, large temperature differences between day and night, vibration from passing vehicles, crushing, and acid / alkali corrosion). After several years of use, the magnetic field strength of the magnetic component that detects the manhole cover's status using magnetic induction weakens. Combined with vibrations from passing vehicles, this increases the likelihood of false alarms (e.g., incorrectly identifying the manhole cover as open and reporting an alarm), leading to unnecessary inspections. Monitoring devices that use gyroscopes as sensors also have a high probability of false alarms. Due to the significant interference on the road surface, the time it takes for a manhole cover to rise and fall is very short (usually around 0.5 seconds). If the tilt angle sensitivity setting of the gyroscope is too high, it will cause frequent alarm triggering; if the tilt angle sensitivity setting is too low, it is very likely that the gyroscope will fail to wake up the device, resulting in the alarm for the change in the manhole cover status not being reported correctly.

[0004] Meanwhile, existing manhole cover monitoring devices typically use lithium-ion batteries for power, and these devices need to operate for extended periods (generally 3-5 years or more). Therefore, the power consumption of the equipment must be rigorously designed to maintain a low-power operating mode to the greatest extent possible. However, existing manhole cover monitoring devices are prone to false alarms, which often leads to accidental wake-up calls, making it difficult to achieve low power consumption. In view of the above-mentioned problems, the inventors of this case conducted in-depth research on this issue, resulting in this invention. [Summary of the Invention]

[0005] The technical problem to be solved by the present invention is to provide a method for monitoring the status of manhole covers based on the Hall effect and non-contact ranging, so as to solve the problems that existing manhole cover monitoring devices are prone to false alarms and missed alarms and cannot truly achieve low power consumption.

[0006] This invention is implemented as follows: a method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging, the monitoring method comprising the following steps:

[0007] The monitoring device for controlling the manhole cover enters standby mode, and the Hall switch element of the monitoring device senses the change in the magnetic field strength of the magnet on the manhole cover;

[0008] When the switching state of the Hall switch element changes, the control and monitoring device switches to wake-up mode and determines whether the wake-up event of the Hall switch element is a valid event.

[0009] If the wake-up event is valid, the control monitoring device switches to ranging mode, measures the distance between the monitoring device and the signal reflector of the manhole cover through the ranging element on the monitoring device, and determines the state of the manhole cover based on the measured distance.

[0010] If the wake-up event is invalid, the control monitoring device switches back to standby mode.

[0011] Furthermore, before determining whether the wake-up event of the Hall switch element is a valid event in wake-up mode, the method further includes:

[0012] After the monitoring device switches to wake-up mode, it acquires the current time and the time of the last switch to wake-up mode, determines whether the time difference between the last switch to wake-up mode and the current time is greater than the preset frequent wake-up interval. If the time difference is less than or equal to the frequent wake-up interval, it marks this wake-up as an interference wake-up, increments the count value of interference wake-up by 1, and controls the monitoring device to switch to status inspection mode.

[0013] If the time difference is greater than the interval between frequent wake-ups, then this wake-up is marked as a normal wake-up, the count value of the interfering wake-up is cleared to zero, and the monitoring device is controlled to switch to de-jitter mode.

[0014] Furthermore, the step of determining whether the wake-up event of the Hall switch element is a valid event in wake-up mode specifically includes:

[0015] When the monitoring device switches to the status inspection mode, the monitoring device is in a shallow sleep state. After the first internal timer sets a first preset time, the monitoring device is woken up. The device checks whether the switching state of the Hall switch element has changed. If the switching state of the Hall switch element has changed, the wake-up event is determined to be a valid event. If the switching state of the Hall switch element has not changed, the wake-up event is determined to be an invalid event.

[0016] When the monitoring device switches to debounce mode, it is in a shallow sleep state. After a second preset time is set by the second internal timer, the monitoring device is woken up. The device then checks whether the switching state of the Hall switch element has changed. If the switching state of the Hall switch element has changed, the wake-up event is determined to be a valid event. If the switching state of the Hall switch element has not changed, the wake-up event is determined to be an invalid event.

[0017] Furthermore, the second preset time is set to different values ​​depending on the type of manhole cover.

[0018] Furthermore, the measurement of the distance between the monitoring device and the signal reflector of the manhole cover using the ranging element on the monitoring device specifically includes:

[0019] The distance between the monitoring device and the signal reflector of the manhole cover is measured multiple times by the ranging element on the monitoring device. The maximum and minimum distance values ​​are removed, and the average value of the remaining distance values ​​is calculated. The average value is then used as the final measurement result.

[0020] Furthermore, determining the state of the manhole cover based on the measured distance specifically includes:

[0021] Determine whether the measured distance is greater than a preset distance threshold. If the measured distance is greater than the preset distance threshold, determine that the manhole cover is in the open state, control the monitoring device to switch to alarm mode, report alarm information through the communication module of the monitoring device, and control the monitoring device to switch back to standby mode after the alarm information is reported.

[0022] If the measured distance is less than or equal to the preset distance threshold, it is determined that the manhole cover is in a closed state, and the control monitoring device switches back to standby mode.

[0023] Furthermore, the manhole cover includes a base and a cover body; a first cavity is formed on the inner wall of the base, and the monitoring device is disposed in the first cavity; the magnet and the signal reflector are disposed at the bottom of the cover body, and the magnet is disposed at the position of the corresponding Hall switch element, and the signal reflector is disposed at the position of the corresponding ranging element.

[0024] Furthermore, the distance between the Hall switch element and the magnet is less than or equal to 5 cm.

[0025] Furthermore, the ranging element is any one of a wireless ranging sensor, a laser ranging sensor, an infrared ranging sensor, or an acoustic ranging sensor.

[0026] This invention uses a Hall effect switch element to sense changes in the magnetic field strength of a magnet on a manhole cover in standby mode, thereby initially identifying the state of the manhole cover and controlling the monitoring device to switch to wake-up mode. Then, it determines whether the wake-up event of the Hall effect switch element is a valid event. Only when the wake-up event is valid is the distance between the monitoring device and the signal reflector of the manhole cover measured using a ranging element, and the state of the manhole cover is determined based on the measured distance. If the wake-up event is invalid, the monitoring device is directly controlled to switch back to standby mode. Therefore, by adopting the technical solution of this invention, at least the following beneficial effects are achieved:

[0027] 1. First, use Hall effect switching elements for preliminary identification, and then use ranging elements for distance measurement and determination. Through the cooperation of Hall effect switching elements and ranging elements, the occurrence of false alarms and missed alarms can be effectively reduced, thereby effectively improving the problems of unnecessary inspections caused by false alarms and safety hazards caused by missed alarms.

[0028] 2. By combining the Hall effect switch element and the ranging element with the validity judgment of the wake-up event, the occurrence of false alarms and missed alarms can be effectively reduced. The monitoring device can be woken up due to false alarms, thus reducing unnecessary power consumption and extending the service life of the monitoring device. [Attached Image Description]

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Figure 1 This is an execution flowchart of a manhole cover status monitoring method based on the Hall effect and non-contact ranging according to the present invention.

[0031] Figure 2 This is a block diagram illustrating the monitoring principle of the monitoring device in this invention;

[0032] Figure 3 This is one of the structural schematic diagrams of the manhole cover in this invention;

[0033] Figure 4 This is the second schematic diagram of the structure of the manhole cover in this invention;

[0034] Figure 5 This is a structural diagram of the cover body in this invention;

[0035] Figure 6 This is a structural diagram of the base in this invention;

[0036] Figure 7 This is a cross-sectional view of the base in this invention.

[0037] Explanation of reference numerals in the attached figures:

[0038] Manhole cover 100;

[0039] Monitoring device 1, control motherboard 11, battery 12;

[0040] Hall switch element 2;

[0041] Magnet 3;

[0042] Distance measuring element 4;

[0043] Signal reflection part 5;

[0044] Communication module 6;

[0045] Base 7, first cavity 71;

[0046] Cover 8, support block 81, second cavity 811.

Detailed Implementation Methods

[0047] To better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] It should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used solely for the convenience of describing these embodiments and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0049] Example 1

[0050] Please see Figures 1 to 7 As shown, this invention discloses a method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging. The monitoring method includes the following steps:

[0051] Step S1: The monitoring device 1 of the control manhole cover 100 enters standby mode. StandbyIn this standby mode, the entire monitoring device 1 is in a deep sleep state, and its power consumption is at its lowest. At this time, only the Hall switch element 2 inside the monitoring device 1 is in normal working condition. The Hall switch element 2 of the monitoring device 1 senses the change in the magnetic field strength of the magnet 3 on the manhole cover 100. When the Hall switch element 2 senses a change in magnetic field strength exceeding a set magnetic field strength threshold, the switching state of the Hall switch element 2 will change. In practical operation, when the manhole cover 100 is closed, the magnet 3 on the manhole cover 100 approaches the monitoring device 1, and the Hall switch element 2 of the monitoring device 1 generates a current due to the Hall effect. When the manhole cover 100 is open, the magnet 3 on the manhole cover 100 moves away from the monitoring device 1, and the current generated by the Hall switch element 2 of the monitoring device 1 also decreases or disappears due to the weakening or disappearance of the magnetic field. Therefore, the state of the manhole cover 100 can be initially identified by the state change of the Hall switch element 2. For example, when the manhole cover 100 is closed, the initial switching state of the Hall switch element 2 is on. Then, when the Hall switch element 2 senses that the change in the magnetic field strength of the magnet 3 exceeds the set magnetic field strength threshold, the switching state of the Hall switch element 2 will change from the initial on to off. At this time, it can be initially identified that the manhole cover 100 is in the open state. The magnetic field strength threshold can be set according to actual needs.

[0052] Before step S1, the process includes: after installing the monitoring device 1 onto the manhole cover 100, powering on the monitoring device 1, and after the monitoring device 1 completes initialization and self-test operations, proceeding to step S1.

[0053] Step S2: When the switching state of Hall switch element 2 changes, the control monitoring device 1 switches to wake-up mode. Wakeup In wake-up mode, determine whether the wake-up event of Hall switch element 2 is a valid event;

[0054] If the wake-up event is valid, control monitoring device 1 to switch to ranging mode. Measure The distance between the monitoring device 1 and the signal reflector 5 of the manhole cover 100 is measured by the ranging element 4 on the monitoring device 1, and the state of the manhole cover 100 is determined according to the measured distance, so as to decide whether to report the alarm information based on the state of the manhole cover 100.

[0055] If the wake-up event is invalid, control monitoring device 1 switches back to standby mode. Standby To achieve low power consumption.

[0056] This invention uses a Hall effect switch element 2 to sense changes in the magnetic field strength of the magnet 3 on the manhole cover 100 in standby mode, thereby initially identifying the state of the manhole cover 100 and controlling the monitoring device 1 to switch to wake-up mode. Then, it determines whether the wake-up event of the Hall effect switch element 2 is a valid event. Only when the wake-up event is valid is the distance between the monitoring device 1 and the signal reflection part 5 of the manhole cover 100 measured by the ranging element 4, and the state of the manhole cover 100 is determined based on the measured distance. If the wake-up event is invalid, the monitoring device 1 is directly controlled to switch back to standby mode. Therefore, by adopting the technical solution of this invention, at least the following beneficial effects are achieved:

[0057] 1. First, Hall switch element 2 is used for preliminary identification, and then distance measurement element 4 is used for distance determination. Through the cooperation of Hall switch element 2 and distance measurement element 4, the occurrence of false alarms and missed alarms can be effectively reduced, thereby effectively improving the problems of unnecessary inspections caused by false alarms and safety hazards caused by missed alarms.

[0058] 2. Due to the cooperation between Hall switch element 2 and ranging element 4, the occurrence of false alarms and missed alarms can be effectively reduced, and the monitoring device 1 can be less likely to be woken up due to false alarms. Therefore, unnecessary power consumption can be reduced, thereby extending the service life of the monitoring device 1.

[0059] In a preferred embodiment of the present invention, before determining whether the wake-up event of the Hall switch element 2 is a valid event in the wake-up mode, the method further includes:

[0060] When monitoring device 1 switches to wake-up mode Wakeup After that, obtain the current time and the time of the last switch to wake-up mode, and determine whether the time difference T0 between the last switch to wake-up mode and the current time is greater than the preset frequent wake-up interval T. Interference If the time difference T0 is less than or equal to the frequent wake-up interval T Interference If this wake-up is marked as a disruptive wake-up (i.e., Hall switch event A in the diagram), the counter value of the disruptive wake-up will be set. Interference Add 1, and control monitoring device 1 to switch to status inspection mode. Review );

[0061] If the time difference T0 is greater than the frequent wake-up interval T Interference If the event occurs, mark this wake-up as a normal wake-up (i.e., Hall switch event B in the diagram), and reset the counter value for interfering wake-ups. Interference Reset to zero and control monitoring device 1 to switch to de-jitter mode. Debounce ).

[0062] In this invention, by judging the time difference between the last time the monitoring device 1 switched to the wake-up mode and the current time after switching to the wake-up mode, it is possible to preliminarily determine whether the current wake-up is an interference wake-up or a normal wake-up, thereby providing a certain auxiliary basis for judging the validity of the wake-up event.

[0063] In a preferred embodiment of the present invention, determining whether the wake-up event of the Hall switch element 2 is a valid event in wake-up mode specifically includes:

[0064] When monitoring device 1 switches to status inspection mode (Mode) Review When the monitoring device 1 is in a shallow sleep state, it is used to reduce power consumption. After the first preset time is set by the first internal timer, the monitoring device 1 is woken up. The monitoring device 1 is woken up to check whether the switching state of the Hall switch element 2 has changed. If the switching state of the Hall switch element 2 has changed, the wake-up event is determined to be a valid event. If the switching state of the Hall switch element 2 has not changed, the wake-up event is determined to be an invalid event.

[0065] Because monitoring device 1 is switched to status inspection mode (Mode) Review The current state inspection mode corresponds to interference wake-up, so the wake-up event can be initially determined to be invalid. If the manhole cover 100 is slightly lifted due to vibrations from passing vehicles, it will automatically fall back into place after a few seconds, and the Hall switch element 2 will remain in its initial on state. However, if the manhole cover 100 is opened due to human intervention, it will not automatically return to its original position after a few seconds, and the Hall switch element 2 will be in its off state. Therefore, to further determine the validity of the wake-up event and avoid problems caused by misjudgment, this invention uses a first internal timer for timing, and wakes up the monitoring device 1 after a first preset time (which can be set according to actual needs). The switch state of the Hall switch element 2 is checked again. If the Hall switch element 2 remains in its initial on state, the wake-up event is determined to be invalid; if the Hall switch element 2 is in its off state, the wake-up event is determined to be valid.

[0066] When monitoring device 1 switches to de-shake mode (Mode) Debounce When the monitoring device 1 is in a shallow sleep state, it is used to reduce power consumption. After the second internal timer sets a second preset time, the monitoring device 1 is woken up. The monitoring device 1 is woken up to check whether the switching state of the Hall switch element 2 has changed. If the switching state of the Hall switch element 2 has changed, the wake-up event is determined to be a valid event. If the switching state of the Hall switch element 2 has not changed, the wake-up event is determined to be an invalid event.

[0067] The purpose of using a second internal timer to set a second preset time is to reduce vibration. This second preset time is set to different values ​​depending on the type of manhole cover. For example, in a ductile iron manhole cover 100, because the opening process takes a relatively long time, if the second preset time is set too short, the monitoring device 1 will likely be activated at the initial stage of prying the cast iron manhole cover, and the entire time required for the manhole cover to be fully opened from prying is approximately between 10 and 50 seconds (in the case of manual opening). In contrast, in a composite resin manhole cover 100, the entire opening process takes relatively short time (approximately 1 to 3 seconds). Because the monitoring device 1 is switched to the vibration reduction mode... Debounce The debounce mode corresponds to normal wake-up, so the wake-up event can be initially determined to be a valid event. Similarly, in order to further determine the validity of the wake-up event and avoid problems caused by misjudgment or incorrect judgment, the present invention uses a second internal timer for timing, and wakes up the monitoring device 1 again after timing a second preset time, and detects the switching state of the Hall switch element 2 again. If the switching state of the Hall switch element 2 remains in the initial on state, the wake-up event can be determined to be an invalid event; if the switching state of the Hall switch element 2 is in the off state, the wake-up event can be determined to be a valid event.

[0068] In a preferred embodiment of the present invention, in order to reduce the problems of misjudgment and incorrect judgment caused by measurement errors, the measurement of the distance between the monitoring device 1 and the signal reflection part 5 of the manhole cover 100 by the ranging element 4 on the monitoring device 1 specifically includes:

[0069] The distance between the monitoring device 1 and the signal reflector 5 of the manhole cover 100 is measured multiple times by the ranging element 4 on the monitoring device 1. The maximum and minimum distance values ​​are removed, and the average value of the remaining distance values ​​is calculated. Average and the average Distance Average As the final measurement result, this final measurement result will be used as the basis for determining the state of manhole cover 100.

[0070] In a preferred embodiment of the present invention, determining the state of the manhole cover 100 based on the measured distance specifically includes:

[0071] Determine whether the measured distance is greater than the preset distance threshold. Alert If the measured distance is greater than the preset distance threshold Distance Alert If the manhole cover 100 is determined to be open, the monitoring device 1 will switch to alarm mode. AlertThe alarm information is reported through the communication module 6 of the monitoring device 1, and after the alarm information is reported, the monitoring device 1 is controlled to switch back to standby mode to achieve low power consumption.

[0072] If the measured distance is less than or equal to the preset distance threshold Distance Alert If the manhole cover 100 is determined to be in a closed state, the monitoring device 1 is controlled to switch back to standby mode in order to achieve low power consumption.

[0073] In a preferred embodiment of the present invention, the distance threshold Distance Alert The value needs to be greater than the distance between the monitoring device 1 and the signal reflector 5 of the manhole cover 100, and less than the radius of the manhole.

[0074] In a preferred embodiment of the present invention, the communication module 6 may be a 4G wireless communication module, a 5G wireless communication module, a LoRa wireless communication module, etc., and the communication module 6 is mainly used to report alarm information to the platform.

[0075] For a preferred embodiment of the present invention, please refer to the following: Figures 3-7 As shown, the manhole cover 100 includes a base 7 and a cover body 8; a first cavity 71 is formed on the inner wall of the base 7, and the monitoring device 1 is disposed in the first cavity 71. This not only protects the monitoring device 1, but also does not affect the installation of the cover body 8, and also prevents personnel from touching the monitoring device 1 when entering or leaving the manhole; the magnet 3 and the signal reflector 5 are disposed at the bottom of the cover body 8, and the magnet 3 is disposed at the position corresponding to the Hall switch element 2, and the signal reflector 5 is disposed at the position corresponding to the ranging element 4, so that the Hall switch element 2 can cooperate with the magnet 3 to achieve preliminary identification and judgment, and the ranging element 4 can cooperate with the signal reflector 5 to achieve distance measurement.

[0076] In a preferred embodiment of the present invention, the distance between the Hall switch element 2 and the magnet is less than or equal to 5 cm. Because if the distance between the Hall switch element 2 and the magnet 3 is set too large, the magnetic field strength sensed by the Hall switch element 2 will be weak, which may easily lead to misjudgment. Therefore, in order to ensure that the magnetic field strength sensed by the Hall switch element 2 is significantly different when the cover 8 is closed and open, the present invention designs the distance between the Hall switch element 2 and the magnet 3 to be less than or equal to 5 cm. Preferably, the distance between the Hall switch element 2 and the magnet 3 is greater than 1 cm and less than 3 cm.

[0077] In a preferred embodiment of the present invention, the ranging element 4 is any one of a wireless ranging sensor, a laser ranging sensor, an infrared ranging sensor, or an acoustic ranging sensor. However, the present invention is not limited to this; other types of non-contact ranging sensors may also be used in specific implementations.

[0078] In a preferred embodiment of the present invention, the magnet 3 is a rubidium magnet.

[0079] In a preferred embodiment of the present invention, the intelligent monitoring device 1 further includes a control motherboard 11 and a battery 12, wherein the Hall switch element 2, the ranging element 4, the communication module 6 and the battery 12 are all electrically connected to the control motherboard 11; the battery 12 is used to power the operation of the entire intelligent monitoring device 1, and the battery 12 may be a lithium-ion battery.

[0080] In a preferred embodiment of the present invention, a support block 81 extends downward from the bottom edge of the cover 8. The magnet 3 and the signal reflector 5 are both mounted on the support block 81. This satisfies the support requirements of the magnet 3 and the signal reflector 5 without affecting the installation of the cover 8 and the base 7. Preferably, the support block 81 has a second cavity 811 on the side facing the Hall switch element 2, and the magnet 3 is installed within the second cavity 811.

[0081] In one specific embodiment of the present invention, the signal reflecting part 5 is a reflective plane formed on the support block 81, and the signal transmitting end of the ranging element 4 is aligned with the reflective plane, thereby realizing the measurement of the distance between the intelligent monitoring device 1 and the signal reflecting part 5.

[0082] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for monitoring the state of a well lid based on the Hall effect and non-contact distance measurement, characterized in that: The monitoring method includes the following steps: The monitoring device for controlling the manhole cover enters standby mode, and the Hall switch element of the monitoring device senses the change in the magnetic field strength of the magnet on the manhole cover; When the switching state of the Hall effect switch element changes, the control monitoring device switches to wake-up mode. In wake-up mode, it determines whether the wake-up event of the Hall effect switch element is a valid event. Specifically, this includes: when the monitoring device switches to status inspection mode, the monitoring device is in a shallow sleep state. After a first preset time is set by the first internal timer, the monitoring device is woken up; it checks whether the switching state of the Hall effect switch element has changed. If the switching state of the Hall effect switch element has changed, the wake-up event is determined to be a valid event; if the switching state of the Hall effect switch element has not changed, the wake-up event is determined to be an invalid event. When the monitoring device switches to debouncing mode, the monitoring device is in a shallow sleep state. After a second preset time is set by the second internal timer, the monitoring device is woken up; it checks whether the switching state of the Hall effect switch element has changed. If the switching state of the Hall effect switch element has changed, the wake-up event is determined to be a valid event; if the switching state of the Hall effect switch element has not changed, the wake-up event is determined to be an invalid event. If the wake-up event is valid, the control monitoring device switches to ranging mode, measures the distance between the monitoring device and the signal reflector of the manhole cover through the ranging element on the monitoring device, and determines the state of the manhole cover based on the measured distance. If the wake-up event is invalid, the control monitoring device switches back to standby mode; Before determining whether the wake-up event of the Hall switch element is a valid event in wake-up mode, the method further includes: after the monitoring device switches to wake-up mode, obtaining the current time and the time of the last switch to wake-up mode, determining whether the time difference between the last switch to wake-up mode and the current time is greater than the preset frequent wake-up time interval, and if the time difference is less than or equal to the frequent wake-up time interval, marking this wake-up as an interference wake-up, incrementing the count value of interference wake-up by 1, and controlling the monitoring device to switch to status inspection mode. If the time difference is greater than the interval between frequent wake-ups, then this wake-up is marked as a normal wake-up, the count value of the interfering wake-up is cleared to zero, and the monitoring device is controlled to switch to de-jitter mode.

2. The method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in claim 1, characterized in that: The second preset time is set to different values ​​depending on the type of manhole cover.

3. The method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in claim 1, characterized in that: The measurement of the distance between the monitoring device and the signal reflector of the manhole cover using a ranging element on the monitoring device specifically includes: The distance between the monitoring device and the signal reflector of the manhole cover is measured multiple times by the ranging element on the monitoring device. The maximum and minimum distance values ​​are removed, and the average value of the remaining distance values ​​is calculated. The average value is then used as the final measurement result.

4. The method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in claim 1, characterized in that: The determination of the state of the manhole cover based on the measured distance specifically includes: Determine whether the measured distance is greater than a preset distance threshold. If the measured distance is greater than the preset distance threshold, determine that the manhole cover is in the open state, control the monitoring device to switch to alarm mode, report alarm information through the communication module of the monitoring device, and control the monitoring device to switch back to standby mode after the alarm information is reported. If the measured distance is less than or equal to the preset distance threshold, it is determined that the manhole cover is in a closed state, and the control monitoring device switches back to standby mode.

5. A method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in any one of claims 1-4, characterized in that: The manhole cover includes a base and a cover body; a first cavity is formed on the inner wall of the base, and the monitoring device is disposed in the first cavity; the magnet and the signal reflector are disposed at the bottom of the cover body, and the magnet is disposed at the position of the corresponding Hall switch element, and the signal reflector is disposed at the position of the corresponding ranging element.

6. The method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in claim 5, characterized in that: The distance between the Hall switch element and the magnet is less than or equal to 5 cm.

7. The method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in claim 1, characterized in that: The ranging element is a wireless ranging sensor.

8. The method for monitoring the condition of manhole covers based on the Hall effect and non-contact ranging as described in claim 1, characterized in that: The ranging element is any one of a laser ranging sensor, an infrared ranging sensor, or an acoustic ranging sensor.

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