A four-channel tunnel roof separation monitoring device based on magnetic encoder

Abstract

The present invention relates to the technical field of coal mine roadway roof safety monitoring, and in particular to a four-channel roadway roof separation monitoring device based on a magnetic encoder, comprising an anchoring assembly, a transmission assembly, a shell assembly and a signal assembly; the shell assembly comprises a bottom shell, an upper cover and an anchor tube; the anchoring assembly comprises four groups of anchoring units fixed in sequence to different layers of the roof rock stratum along the depth direction of the borehole. The transmission assembly comprises a winding drum, a reduction gear set and a magnetic encoder, and the winding drum is supported on the lower end of the anchor tube by a deep groove ball bearing. The signal assembly comprises an aerial plug mounted on the side of the upper cover, and the aerial plug is connected to the magnetic encoder signal conditioning circuit through a wire. The present invention can fix the rock strata at different depths of the roof through four groups of anchoring units, and the measurement system composed of the magnetic encoder and the reduction gear set can accurately capture the displacement changes of each layer. At the same time, the winding spring automatically compensates for the slack of the wire rope and the temperature compensation module corrects the environmental influence, thereby ensuring the stability of long-term monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine roadway roof safety monitoring, and in particular to a four-channel roadway roof separation monitoring device based on a magnetic encoder. Background Art

[0002] Tunnel roof delamination is a common geological hazard during coal mining. This refers to the relative displacement of different layers of the roof rock under stress. Without timely monitoring and early warning, it can lead to safety accidents such as roof collapse. Therefore, real-time, high-precision monitoring of delamination displacement at different depths in the roof is a key technical measure to ensure safe coal mine production.

[0003] The existing roof separation monitoring device has the following technical limitations:

[0004] Traditional devices, mostly single- or dual-channel designs, can only monitor displacement changes in the shallow roof or a single layer, and are unable to simultaneously capture relative delamination trends in rock layers at different depths. Due to the complex structure of coal mine roof strata and significant differences in stability at different layers, single-dimensional monitoring data cannot fully reflect the overall delamination risk of the roof, which can easily lead to delayed warnings or misjudgments.

[0005] Existing devices mostly use optical encoders or mechanical encoders. Optical encoders are easily affected by dust and water vapor underground, resulting in signal attenuation, which increases measurement errors. Mechanical encoders suffer from contact wear and significantly reduce their accuracy after long-term use. The minimum measurable displacement is usually only 0.1mm or more, which makes it difficult to meet the needs of submillimeter delamination monitoring. In addition, the temperature fluctuation range underground is large, and the temperature drift of the encoder will further amplify the measurement error, affecting data reliability.

[0006] The wire rope tensioning of traditional devices relies on regular manual adjustment. If the wire rope is loose, it will directly cause inaccurate displacement measurement. In addition, there is a lack of an effective temperature compensation mechanism. Changes in ambient temperature can easily cause deformation of mechanical components, further exacerbating errors.

[0007] Most existing devices work in independent modes and lack standardized networking interfaces, making it difficult to implement cascade monitoring of multiple devices. For long-distance tunnels or complex geological areas, it is impossible to centrally collect and analyze roof abscission data across the entire region, which is not conducive to a systematic assessment of roof stability.

[0008] Therefore, how to provide a four-channel tunnel roof separation monitoring device based on a magnetic encoder is a problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0009] One purpose of the present invention is to propose a four-channel tunnel roof delamination monitoring device based on a magnetic encoder. The present invention can fix rock layers of different depths on the roof through four sets of anchoring units. The measurement system composed of a magnetic encoder and a reduction gear set can accurately capture the displacement changes of each layer. At the same time, the winding spring automatically compensates for the slack of the wire rope and the temperature compensation module corrects the environmental influence to ensure the stability of long-term monitoring. It also supports cascade networking of 32 devices to realize the centralized collection and analysis of multi-region delamination data, providing comprehensive and reliable technical support for roof safety early warning.

[0010] According to an embodiment of the present invention, a four-channel roadway roof separation monitoring device based on a magnetic encoder includes an anchoring assembly, a transmission assembly, a housing assembly, and a signal assembly;

[0011] The housing assembly includes a bottom shell, an upper cover and an anchor tube. The anchor tube is vertically embedded in a hole in the roof. The bottom shell is connected to the lower end of the anchor tube through a thread, and a bearing is installed on the inner bottom surface. The upper end of the bottom shell is sealed and fixed to the upper cover by bolts, and the side of the bottom shell is fixed to the tunnel roof by expansion bolts.

[0012] The anchor assembly comprises four groups of anchor units which are sequentially fixed to different layers of the roof rock along the depth direction of the borehole. Each group of anchor units comprises a hollow tubular anchor head, an expandable anchor claw and a circular anchor plate. The four groups of anchor units are led out of the borehole by galvanized steel wire ropes and pass parallel to the cross-shaped anchor pipe grid holes inside the anchor rod pipe.

[0013] There are four groups of transmission components, which are distributed and installed around the inner center of the bottom shell. The transmission components include a winding reel, a spring seat, a reduction gear group and a magnetic encoder. The reduction gear group consists of an input gear, an intermediate gear and an output gear. The input gear is coaxially fixed with the winding reel, and the output gear shaft end is connected to the rotating shaft of the magnetic encoder through a flat key. The spring seat is located below the winding reel and has a built-in scroll spring. One end of the spring is fixed to the inner wall of the shell assembly, and the other end is connected to the shaft pin of the winding reel.

[0014] Furthermore, four sets of anchor claws are connected to the end of the anchor head, and the anchoring force between the anchor claws and the rock formation after expansion is ≥ kN. The anchor plate is sleeved on the outside of the anchor head and fixed to the borehole mouth by a nut. The galvanized steel wire rope is 7×19 strands of galvanized steel stranded wire with a breaking tensile force ≥ 15 kN. The surface of the anchor assembly is coated with a molybdenum disulfide lubricating layer, and the friction coefficient with the winding reel groove is ≤ 0.15.

[0015] Furthermore, the winding drum is supported at the lower end of the anchor tube by a deep groove ball bearing, and a spiral groove is opened on the surface. The wire rope is wound in the groove. The total reduction ratio of the reduction gear set is 15:1. The reduction gear set is processed by carburizing and quenching process. The resolution of the magnetic encoder is 0.01°, and it has a built-in AMR magnetoresistive sensor and Schmidt trigger shaping circuit to output a standard TTL level signal.

[0016] Furthermore, the magnetic encoder measures the rotation angle of the reduction gear set through non-contact magnetic resistance induction , and by the formula Converted to displacement distance, where L is the displacement distance of the rock formation, D is the diameter of the reel, i is the total reduction ratio of the reduction gear set, and the formula is In the figure, when the reel diameter D = 60mm and the reduction ratio i = 15:1, the magnetic encoder detects a rotation angle change of 0.01°, which corresponds to a rock displacement distance L = 0.01mm, that is, the minimum measurable displacement of the device is 0.01mm.

[0017] Furthermore, the pre-tightening torque of the coil spring in the coil spring seat is 0.2-0.3N·m. When the slack of the wire rope reaches 5mm, the coil spring automatically releases energy to cause the winding drum to rotate in the opposite direction, compensating for the slack length error of the wire rope ≤±0.5mm.

[0018] Furthermore, the exposed length of the anchor rod tube is 80-100mm, and the gap between the anchor rod tube and the drill hole is filled with fast-hardening cement slurry. An annular sealing groove is provided at the bolt connection between the bottom shell and the upper cover. An O-ring is embedded in the annular sealing groove, and the compression rate after embedding is 25%-30%. There is no leakage inside the shell assembly under an air pressure of 0.1MPa, and the surface is hot-dip galvanized.

[0019] Furthermore, the signal component includes an aviation plug installed on the side of the upper cover, which is connected to the magnetic encoder signal conditioning circuit through a wire. The interface includes four RS485 differential signal lines and a power line. A metal armored cable sealing joint is provided at the connection between the aviation plug and the shell. The signal component can set the device ID of 1-32 through the address dip switch, supports cascade networking of up to 32 devices, and displays the displacement curve of each channel in real time through ground monitoring software. The historical data storage period can be ≥1 year.

[0020] Furthermore, the anchor pipe grid inside the anchor pipe is fixed to the middle section of the anchor pipe by four sets of M4 countersunk screws, and the distance from the hole mouth is 1 / 2 of the exposed length, which can ensure that the vertical section length of the wire rope in the drilled hole is ≥500mm and the parallelism error is ≤2mm / m.

[0021] Furthermore, a temperature compensation module is included, which includes a temperature sensor and a microprocessor. The microprocessor calculates the angle measurement value based on the ambient temperature T collected by the temperature sensor and the temperature drift characteristic curve of the magnetic encoder in the range of -20℃ to 60℃. Correction, the corrected angle value satisfy ,in is the temperature drift coefficient, The reference temperature is ≤ ±0.02 mm.

[0022] Furthermore, the overall installation verticality error of the device must be ≤1°, and the parallelism error of the steel wire ropes of the four groups of anchoring components in the drilled hole must be ≤2mm / m to ensure that the steel wire ropes are not skewed or stuck during displacement measurement.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention uses four groups of anchoring units to be fixed in sequence at different roof layers along the depth of the borehole, and uses a reel design with independent spiral grooves to achieve simultaneous and independent monitoring of the delamination displacement of four key roof layers. Combined with the guiding constraint of the wire rope by the cross-shaped anchor pipe grid, the displacement signals of each channel are ensured to be transmitted without interference, and the relative delamination patterns between rock layers can be accurately identified, providing multi-dimensional data support for roof stability early warning, which significantly improves the ability to predict roof stratification damage under complex geological conditions. This design is not seen in similar monitoring devices in the existing technology and has outstanding substantive characteristics.

[0025] 2. The present invention adopts a combination of a non-contact magnetic encoder and a reduction gear set. The tiny displacement of the winding reel is amplified 15 times by the reduction gear set and then transmitted to the magnetic encoder. Combined with the formula conversion, the minimum measurable displacement of 0.01mm is achieved, which is more than 10 times the accuracy of traditional devices. At the same time, the magnetic encoder has a built-in AMR magnetoresistive sensor and Schmidt trigger shaping circuit, which can work stably in dusty and humid environments, solving the constraints of the harsh underground environment on high-precision measurement. Its combination of accuracy and environmental adaptability achieves technical effects that are difficult to achieve with existing technologies.

[0026] 3. The present invention designs a scroll spring pre-tightening and automatic compensation structure. When the wire rope slackens by 5mm, the spring automatically releases energy to drive the winding drum to rotate in the opposite direction, and the compensation error is ≤±0.5mm, which solves the disadvantage that traditional devices require manual periodic tensioning, ensuring that the wire rope is always in a tensioned state during long-term monitoring. A temperature compensation module is also added. The temperature sensor collects the ambient temperature of -20℃-60℃ in real time. Combined with the temperature drift characteristic curve of the magnetic encoder, the microprocessor dynamically corrects the angle measurement value, and controls the displacement error caused by temperature within ±0.02mm, overcoming the interference of drastic changes in underground temperature on measurement accuracy. The synergistic effect of the above two mechanisms significantly improves the measurement stability of the device in long-term and complex environments compared with traditional technologies, breaking through the technical bottlenecks of environmental interference and accuracy attenuation.

[0027] 4. The signal component of the present invention supports cascading networking of 32 devices through address dial switches. Combining RS485 differential signal transmission with real-time curve display and ≥1 year historical data storage functions of ground monitoring software, it realizes the centralized collection and analysis of roof separation data in a single area and a large range, overcomes the limitations of traditional single-device isolated monitoring, and provides systematic data support for the overall stability assessment of the tunnel roof. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is a schematic diagram of the overall structure of a four-channel tunnel roof separation monitoring device based on a magnetic encoder proposed in the present invention;

[0030] Figure 2 This is a schematic diagram of the disassembled structure of a four-channel tunnel roof separation monitoring device based on a magnetic encoder proposed in the present invention;

[0031] Figure 3 This is a disassembled structural diagram of the spring seat, winding drum, reduction gear set and magnetic encoder of a four-channel tunnel roof separation monitoring device based on a magnetic encoder proposed in the present invention.

[0032] In the figure: 1. bottom shell; 2. upper cover; 3. anchor rod pipe; 4. anchor pipe grille; 5. anchor head; 6. anchor plate; 7. magnetic encoder; 8. winding spring seat; 9. winding reel; 10. reduction gear set; 11. navigation plug; 12. anchor claw. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0035] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0036] Based on the above, reference Figure 1-3 As shown in , the present disclosure provides a four-channel tunnel roof delamination monitoring device based on a magnetic encoder, including: an anchoring assembly, a transmission assembly, a shell assembly and a signal assembly, which can realize real-time and high-precision monitoring of the delamination displacement of different layers of the roof.

[0037] The shell assembly serves as the support and protection structure of the entire device. Its design rationality directly affects the stability and service life of the device. The shell assembly includes the bottom shell 1, the upper cover 2 and the anchor pipe 3. The structure and installation requirements of each part are as follows:

[0038] The anchor tube 3 is a key component connecting the shell and the top plate, and its installation quality is crucial to the stability of the entire device. When installing the anchor tube 3, it is necessary to first drill a hole of appropriate size on the tunnel top plate. The diameter of the hole should match the outer diameter of the anchor tube 3 to ensure that the anchor tube 3 can be embedded vertically. After the anchor tube 3 is embedded in the borehole, its exposed length must be strictly controlled within the range of 80-100mm. If the exposed part is too short, it may affect the connection strength with the bottom shell 1, and if it is too long, it may cause the overall stability of the device to decrease. In order to ensure a firm connection between the anchor tube 3 and the borehole, the gap between the two needs to be filled with fast-hardening cement slurry. The fast-hardening cement slurry should have the characteristics of fast setting speed and high early strength, and can achieve the fixation of the anchor tube 3 in a short time.

[0039] The bottom shell 1 serves as the installation base for the internal components of the device, and its structural design must meet the dual requirements of support and protection. The bottom shell 1 is connected to the lower end of the anchor pipe 3 through threads. This connection method is not only convenient for installation and disassembly, but also ensures the tightness of the connection. A bearing is installed on the bottom surface of the bottom shell 1. The bearing is used to support the reel 9 in the transmission assembly to ensure that the reel 9 can rotate flexibly. The upper end of the bottom shell 1 is sealed and fixed to the upper cover 2 by bolts. To ensure the sealing performance of the shell, an O-type rubber sealing ring is provided on the joint surface between the bottom shell 1 and the upper cover 2. At the same time, an annular sealing groove is opened at the bolt connection between the bottom shell 1 and the upper cover 2. After the O-type sealing ring is embedded in the annular sealing groove, its compression rate needs to be controlled between 25% and 30%. This compression rate range has been verified by multiple tests and can effectively ensure that the shell assembly is leak-free under an air pressure of 0.1MPa, thereby preventing dust, water vapor, etc. from entering the shell from underground coal mines and damaging internal components. In addition, the side of the bottom shell 1 is fixed to the tunnel roof by expansion bolts. The number and specifications of the expansion bolts should be selected according to the size and weight of the bottom shell 1 to ensure that the bottom shell 1 can be firmly fixed to the tunnel roof to avoid loosening of the device due to factors such as vibration.

[0040] The upper cover 2 and bottom shell 1 form a closed housing space, protecting the internal components. The upper cover 2 is connected to the bottom shell 1 with bolts. During installation, the bolts must be tightened evenly to ensure that the joint surface between the upper cover 2 and the bottom shell 1 is evenly stressed to avoid seal failure due to excessive local stress.

[0041] To enhance the housing's corrosion resistance in the harsh underground coal mine environment, the bottom shell 1, upper cover 2, and anchor tube 3 are all hot-dip galvanized. This galvanized coating offers excellent corrosion resistance, effectively protecting the housing from the damp, dusty, and corrosive environments of underground coal mines, extending the device's service life.

[0042] The anchor assembly is one of the core components for monitoring the displacement of different layers of the roof. Its function is to transmit the displacement of different rock layers to the transmission assembly. The anchor assembly consists of four groups of anchor units fixed in sequence to different layers of the roof rock along the depth direction of the drill hole. The structure and working principle of each group of anchor units are as follows:

[0043] Each anchoring unit includes a hollow tubular anchor head 5, expandable anchor claws 12 and a circular anchor plate 6. The anchor head 5 adopts a hollow tubular structure to facilitate the passage and arrangement of the wire rope. Four groups of anchor claws 12 are connected to the end of the anchor head 5. The anchor claws 12 are the key components for fixing the anchor unit to the rock formation. When installing the anchor unit, after the anchor head 5 is sent to the predetermined depth of the borehole, the anchor claws 12 are expanded by a specific tool. The expanded anchor claws 12 are in close contact with the rock formation, generating sufficient anchoring force. According to tests, the anchoring force between the expanded anchor claws 12 and the rock formation is ≥5kN. This anchoring force can ensure that the anchor unit will not slide relative to the rock formation when the rock formation is displaced, ensuring that the displacement information of the rock formation can be accurately transmitted.

[0044] A circular anchor disc 6 is placed over the anchor head 5 and secured to the borehole opening via a nut. The function of the anchor disc 6 is to limit the axial displacement of the anchor head 5, preventing it from being dislodged from the borehole due to rock formation displacement. The diameter of the anchor disc 6 should be larger than the diameter of the borehole to ensure a secure fixation. The tightening force of the nut should be moderate to ensure that the anchor disc 6 is securely fixed while avoiding deformation of the anchor head 5 due to overtightening.

[0045] Four sets of anchoring units are fixed to different layers of the roof rock stratum, and the displacement information of each layer is transmitted to the transmission component via galvanized steel wire rope. The galvanized steel wire rope used is a 7×19-strand structure. This type of steel wire rope has high strength and toughness, with a breaking force of ≥15kN, which can meet the strength requirements for transmitting rock stratum displacement. To reduce the frictional resistance between the steel wire rope and the reel 9, the steel wire rope surface is coated with a molybdenum disulfide lubricating layer. After testing, the friction coefficient between the steel wire rope and the reel 9 groove after the molybdenum disulfide lubricating layer is ≤0.15, effectively reducing the energy loss and wire rope wear caused by friction.

[0046] After the wire ropes of the four anchoring units emerge from the drilled hole, they must be threaded parallel to the holes in the cross-shaped anchor grid 4 inside the anchor tube 3. The anchor grid 4 is secured to the middle section of the anchor tube 3 with four sets of M4 countersunk screws, at a distance from the hole opening that is half the exposed length of the anchor tube 3. This installation method ensures that the vertical length of the wire rope within the drilled hole is ≥500mm and that the parallelism error of the wire rope is ≤2mm / m. A sufficiently long vertical section and high parallelism prevent the wire rope from deflecting or jamming during movement, ensuring accurate displacement transmission.

[0047] The transmission assembly is a key component that converts the linear displacement transmitted by the anchor assembly into an angular signal recognizable by the magnetic encoder 7. Its performance directly affects the device's measurement accuracy. There are four transmission assemblies, equidistantly spaced around the inner center of the bottom shell 1. The transmission assembly includes a cable reel 9, a reduction gear set 10, and a magnetic encoder 7. The structure and operating principle of each component are as follows:

[0048] The wire reel 9 is a core component of the transmission assembly. Its primary function is to wind the wire rope and convert its linear displacement into rotational motion. The reel 9 is supported at the lower end of the anchor tube 3 by a deep-groove ball bearing. These bearings offer low friction, high speed, and high precision, ensuring flexible rotation and minimizing measurement errors caused by friction. The reel 9 features spiral grooves on its surface, through which the wire rope is wound. The precise dimensions and spacing of the grooves ensure uniform winding of the wire rope, preventing problems such as skipping and overlapping windings.

[0049] The function of the reduction gear set 10 is to reduce the rotational motion of the cable reel 9 and transmit it to the magnetic encoder 7. Its total reduction ratio is 15:1. The reduction gear set 10 consists of an input gear, an intermediate gear, and an output gear. The input gear is fixed coaxially with the cable reel 9. When the cable reel 9 rotates, the input gear rotates synchronously with it, and through gear meshing, it drives the intermediate gear, which in turn drives the output gear. The output gear shaft is connected to the rotating shaft of the magnetic encoder 7 via a flat key, transmitting the reduced rotational motion to the magnetic encoder 7. The three-stage spur gear reduction design converts the high-speed rotation of the cable reel 9 into the appropriate speed required by the magnetic encoder 7, while also improving the accuracy and stability of the transmission.

[0050] The magnetic encoder 7 is a key component for angle measurement. It measures the rotation angle of the reduction gear set 10 through non-contact magnetic resistance sensing. It features high resolution, fast response, and strong anti-interference capabilities. Its resolution is 0.01°, meeting the requirements for high-precision measurement. The magnetic encoder 7 incorporates an AMR magnetoresistive sensor and a Schmidt trigger shaping circuit. The AMR magnetoresistive sensor converts changes in the rotation angle into changes in an electrical signal. The Schmidt trigger shaping circuit shapes and amplifies the electrical signal, outputting a standard TTL level signal for subsequent signal processing.

[0051] To achieve the conversion from angle signal to displacement distance, a corresponding conversion formula needs to be established. According to the geometric relationship, the relationship between the displacement distance L and the winding drum diameter D, the reduction ratio i and the angle θ measured by the magnetic encoder 7 is: Where L is the rock displacement distance, D is the cable drum diameter, and i is the total reduction ratio of the reduction gear set. For a cable drum diameter of 60 mm and a reduction ratio of 15, substituting this into the formula yields that every 0.01° rotation angle change detected by the magnetic encoder 7 corresponds to a rock displacement distance L of 0.01 mm. This conversion relationship ensures that the device's measurement accuracy meets the requirements for roof separation monitoring in coal mines.

[0052] Below the wire reel 9 is a coil spring seat 8, which houses a spiral spring. One end of the spring is fixed to the inner wall of the housing assembly, and the other end is connected to the axis pin of the wire reel 9. The spring has a preload torque of 0.2-0.3 N·m. During operation, the spring constantly applies a certain tension to the wire reel 9, keeping the wire rope taut. If the wire rope slackens due to rock formation displacement and the slack reaches 5mm, the spring automatically releases energy, causing the wire reel 9 to rotate in the opposite direction, compensating for the slack. The compensation error is ≤±0.5mm. This design effectively avoids measurement errors caused by wire rope slack, ensuring measurement accuracy.

[0053] In order to eliminate the influence of temperature change on the measurement accuracy, the transmission component also includes a temperature compensation module. The temperature compensation module includes a temperature sensor and a microprocessor. The temperature sensor can collect the temperature T of the working environment of the device in real time. The temperature range is -20℃~60℃. The microprocessor uses the collected temperature T and the temperature drift characteristic curve of the magnetic encoder 7 in this temperature range to calculate the angle measurement value. Correction, the corrected angle value satisfy ,in is the temperature drift coefficient, is the base temperature.

[0054] The corrected angle value can effectively reduce the impact of temperature changes on the measurement results, making the displacement measurement error caused by temperature ≤±0.02mm.

[0055] The signal assembly is crucial for data transmission and power supply between the device and external devices. Its performance directly impacts the device's communication quality and operational stability. The signal assembly includes an aerial connector 11 mounted on the side of the upper cover 2. This connector connects to the signal conditioning circuit of the magnetic encoder 7 via wires. Its interface includes four RS485 differential signal lines and a power cable.

[0056] RS485 differential signal lines offer long transmission distances and strong anti-interference capabilities, making them suitable for the complex electromagnetic environments of underground coal mines. Four RS485 differential signal lines correspond to four channels of measurement signals, enabling independent transmission of data from each channel. The power line provides power to the device's internal electronic components, such as the magnetic encoder 7 and microprocessor, ensuring proper operation.

[0057] A metal armored cable sealing joint is provided at the connection between the aerial plug 11 and the shell. The metal armored cable sealing joint has good sealing and protection performance, which can effectively prevent dust, water vapor, etc. from entering the shell, while protecting the cable from mechanical damage.

[0058] The signal component supports setting device IDs from 1 to 32 via address dip switches. This design enables cascade networking of multiple devices, supporting up to 32 devices connected to the same network simultaneously. Through cascade networking, centralized monitoring of the delamination conditions in different areas of the tunnel roof can be achieved. The data measured by the device is processed by the edge computing node and transmitted to the digital twin linkage platform. The ground monitoring software can display the displacement curves of each channel in real time, allowing staff to promptly grasp the dynamic changes in the roof delamination. At the same time, the historical data storage period is ≥1 year, providing sufficient data support for roof stability analysis and prediction.

[0059] Working principle:

[0060] Before installing the device, sufficient preparations must be made, including site surveys, equipment inspections, and tool preparation. Site surveys primarily determine the location and depth of the drill hole. The drill hole location should be selected in a relatively stable and representative area of ​​the tunnel roof rock layer. The drill hole depth should be determined based on monitoring requirements to ensure that the rock layer to be monitored is covered. Equipment inspections primarily check whether the various components of the device are intact, including the sealing of the housing assembly, the anchoring force of the anchor assembly, the flexibility of the transmission assembly, the communication performance of the signal assembly, etc., to ensure that the equipment can operate normally. Tool preparation includes drilling equipment, installation tools, measuring tools, such as drilling rigs, wrenches, and levels. During installation, first drill a deep hole in the tunnel roof, install four sets of anchor units in sequence along the depth direction of the drill hole, make the anchor claw 12 expand and fix at different layers, fix the anchor plate 6 at the hole mouth, lead out the wire rope and pass it through the anchor pipe grid 4, then vertically embed the anchor pipe 3 into the drill hole with an exposed length of 80-100mm, and fill the gap with fast-hardening cement slurry; after the cement slurry solidifies, connect the bottom shell 1 and the anchor pipe 3, fix the bottom shell 1 to the tunnel roof, install the upper cover 2 and ensure it is sealed, then wind the wire rope around the independent wire groove of the winding drum 9, adjust the preload of the coil spring to ensure that the wire rope Tensioning; check the connection between the reduction gear set 10 and the magnetic encoder 7 to ensure smooth transmission, and finally connect the power line and the signal line through the aviation plug 11, set the device ID, connect to the monitoring platform, and complete the temperature compensation module calibration. When the roof rock layer delaminates, the anchoring unit of the corresponding layer drives the wire rope to move, driving the winding drum 9 to rotate, and transmits it to the magnetic encoder 7 through the reduction gear set 10. The magnetic encoder 7 converts the angle signal into displacement data, which is transmitted to the monitoring platform through the signal component after temperature compensation, realizing real-time and high-precision monitoring of four-channel delamination displacement.

[0061] It should be noted that the verticality error of the entire device must be ≤1°, and the parallelism error of the four sets of wire ropes in the drilled hole must be ≤2mm / m to ensure measurement accuracy. In addition, the components are detachable and connected to facilitate later maintenance and replacement.

[0062] Once the device is installed, it's ready for operation. Ground-based monitoring software displays real-time displacement curves for each channel, allowing personnel to monitor the delamination conditions at different levels of the tunnel roof. When the displacement exceeds a preset threshold, the system issues an alarm, prompting personnel to take immediate action.

[0063] To ensure long-term stable operation, the device requires regular maintenance. This includes: checking the sealing of the housing assembly to ensure there are no leaks; checking the anchoring of the anchor assembly to ensure the anchor unit is secure; checking the flexibility of the transmission assembly and cleaning any dust and debris from the transmission components; checking the communication performance of the signal assembly to ensure smooth data transmission; and regularly calibrating the magnetic encoder 7 and temperature compensation module to ensure measurement accuracy.

[0064] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A four-channel roadway roof separation monitoring device based on a magnetic encoder, characterized in that: It includes an anchoring assembly, a transmission assembly, a housing assembly, and a signal assembly; The shell assembly comprises a bottom shell (1), an upper cover (2) and an anchor rod tube (3), wherein the anchor rod tube (3) is vertically embedded in a hole drilled in the top plate, the bottom shell (1) is connected to the lower end of the anchor rod tube (3) through a thread, and a bearing is installed on the inner bottom surface, the upper end of the bottom shell (1) is sealed and fixed to the upper cover (2) by bolts, and the side of the bottom shell (1) is fixed to the tunnel top plate by expansion bolts; The anchoring assembly comprises four groups of anchoring units which are fixed in sequence at different layers of the top rock layer along the depth direction of the borehole, each group of the anchoring units comprising a hollow tubular anchor head (5), an expandable anchor claw (12) and a circular anchor plate (6), and the four groups of the anchoring units are drawn out of the borehole by galvanized steel wire ropes and then pass through the cross-shaped anchor pipe grid (4) holes inside the anchor rod pipe (3) in parallel; The number of the transmission components is four, and the four transmission components are distributed and installed around the inner center of the bottom shell (1). The transmission components include a winding drum (9), a coil spring seat (8), a reduction gear set (10) and a magnetic encoder (7). The reduction gear set (10) is composed of an input gear, an intermediate gear and an output gear, and the input gear is fixed coaxially with the winding drum (9). The output gear shaft end is connected to the rotating shaft of the magnetic encoder (7) through a flat key. The coil spring seat (8) is located below the winding drum (9) and has a built-in scroll spring. One end of the coil spring is fixed to the inner wall of the shell assembly, and the other end is connected to the shaft pin of the winding drum (9).

2. A four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1, characterized in that: The end of the anchor head (5) is connected to four groups of anchor claws (12), and the anchoring force between the anchor claws (12) and the rock formation after expansion is ≥5kN. The anchor plate (6) is sleeved on the outside of the anchor head (5) and fixed to the borehole through a nut. The galvanized steel wire rope is a 7×19-strand galvanized steel strand with a breaking tensile force ≥15kN. The surface of the anchor assembly is coated with a molybdenum disulfide lubricating layer, and the friction coefficient with the wire groove of the winding drum (9) is ≤0.

15.

3. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The winding drum (9) is supported on the lower end of the anchor rod tube (3) through a deep groove ball bearing, and a spiral groove is provided on the surface. The wire rope is wound in the groove. The total reduction ratio of the reduction gear set (10) is 15:

1. The reduction gear set (10) is processed by a carburizing and quenching process. The magnetic encoder (7) has a resolution of 0.01° and is equipped with an AMR magnetoresistive sensor and a Schmidt trigger shaping circuit, and outputs a standard TTL level signal.

4. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The magnetic encoder (7) measures the rotation angle of the reduction gear set through non-contact magnetic resistance induction , and by the formula Converted to displacement distance, where L is the displacement distance of the rock formation, D is the diameter of the reel, i is the total reduction ratio of the reduction gear set, and the formula is In the figure, when the diameter of the winding drum is D=60mm and the reduction ratio i=15:1, the magnetic encoder (7) detects a rotation angle change of 0.01°, which corresponds to a rock displacement distance L=0.01mm, that is, the minimum measurable displacement of the device is 0.01mm.

5. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The pre-tightening torque of the coil spring in the coil spring seat (8) is 0.2-0.3N·m. When the slack of the wire rope reaches 5mm, the coil spring automatically releases energy to cause the winding drum (9) to rotate in the opposite direction, compensating for the slack length error of the wire rope ≤±0.5mm.

6. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The exposed length of the anchor rod tube (3) is 80-100 mm, and the gap between the anchor rod tube and the drill hole is filled with fast-hardening cement slurry. An annular sealing groove is provided at the bolt connection between the bottom shell (1) and the upper cover (2). An O-ring is embedded in the annular sealing groove, and the compression rate after embedding is 25%-30%. There is no leakage inside the shell assembly under an air pressure of 0.1 MPa, and the surface is hot-dip galvanized.

7. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The signal component includes an aviation plug (11) installed on the side of the upper cover (2), the aviation plug (11) is connected to the signal conditioning circuit of the magnetic encoder (7) through a wire, the interface includes four RS485 differential signal lines and a power line, and a metal armored cable sealing joint is provided at the connection between the aviation plug (11) and the shell. The signal component can set the device ID of 1-32 through the address dial switch, supports a cascade network of up to 32 devices, and displays the displacement curve of each channel in real time through the ground monitoring software. The historical data storage period can be ≥1 year.

8. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The anchor pipe grid (4) inside the anchor pipe (3) is fixed to the middle section of the anchor pipe (3) by four sets of M4 countersunk screws, and the distance from the hole opening is 1 / 2 of the exposed length, which can ensure that the vertical section length of the wire rope in the drilled hole is ≥500mm and the parallelism error is ≤2mm / m.

9. The four-channel roadway roof separation monitoring device based on a magnetic encoder according to claim 1 is characterized in that: The invention also includes a temperature compensation module, which includes a temperature sensor and a microprocessor. The microprocessor adjusts the angle measurement value according to the ambient temperature T collected by the temperature sensor and the temperature drift characteristic curve of the magnetic encoder (7) in the range of -20℃ to 60℃. Correction, the corrected angle value satisfy ,in is the temperature drift coefficient, The reference temperature is ≤ ±0.02 mm.

10. A four-channel roadway roof separation monitoring device based on a magnetic encoder according to any one of claims 1 to 9, characterized in that: The overall installation verticality error of the device must be ≤1°, and the parallelism error of the steel wire ropes of the four sets of anchoring components in the drilled hole must be ≤2mm / m to ensure that the steel wire ropes are not skewed or stuck during displacement measurement.

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