Coal face gas unmanned wireless inspection method

Abstract

The invention relates to a coal face gas unmanned wireless inspection method in the technical field of gas disaster monitoring. The coal face gas unmanned wireless inspection method mainly comprises the steps of S1, data acquisition, S2, local display and jump transmission and S3, data verification and uploading, and gas unmanned inspection and inspection data informatization management are achieved. According to the coal face gas unmanned wireless inspection method, the problem of the last kilometer of manual gas inspection is solved, unmanned inspection of the coal face working face can still be achieved even if people work, it is guaranteed that the inspection process is reliable, the inspection result is accurate, and possibility is brought to termination of the manual gas inspection mode.

Description

Technical Field

[0001] This invention relates to the field of gas disaster monitoring technology, and in particular to a method for unmanned wireless inspection of gas in coal mining faces. Background Technology

[0002] Manual gas inspection and coal mine safety monitoring inspection have formed two routes and two systems for coal mine safety inspection in my country, each with its own technical approach, management regulations, and standard system. Both adhere to the principle of "division of responsibilities, mutual supervision, and joint safety assurance," constructing a collaborative "two-lock" mechanism for gas safety management.

[0003] However, manual gas inspection has faced numerous challenges in recent years: the high labor intensity for gas inspectors leads to low employee well-being; the aging of gas inspectors results in labor shortages; and the large number of gas inspectors leads to high labor costs… Based on this, the “Coal Mine Safety Regulations” (2025 edition) requires: Locations where gas may accumulate or where the concentration may exceed limits, such as the main return airway, the return airway of the mining area, the intake airway of the mining face, the electromechanical material chamber, the coal and rock breaking operation point, the return airway with in-use non-intrinsically safe electromechanical equipment, outside the sealed wall of the goaf, outside the fence of the ventilation stop point, and high gas rise points with a rise height exceeding 0.5m, should be included in the scope of monitoring by manual (robot) or safety monitoring systems. The content, method, and frequency of inspection or monitoring shall be determined by the technical person in charge of the coal mining enterprise.

[0004] In other words, most gas inspection points no longer need to be manually inspected after being included in the safety monitoring system. This policy change has significantly reduced the workload of gas inspectors, reduced the number of gas inspectors, improved their happiness index, and reduced the cost of safe production in coal mines.

[0005] However, the "Coal Mine Safety Regulations" (2025 edition) also require: All manned coal mining faces (excluding the intake airway) must undergo manual checks for methane and carbon dioxide, with the following frequency: 1. Low-gas mines, at least once per shift.

[0006] 2. High-gas mines, at least twice per shift.

[0007] 3. For mining faces with outburst coal seams, risks of gas eruption, or significant and abnormal gas outbursts, at least 3 times per shift.

[0008] In other words, manual gas checks are still necessary even in manned coal mining faces. From a safety perspective, coal mining faces are high-risk work sites, and manual gas checks inevitably pose certain safety risks, which contradicts the safety development philosophy of "less manned, safer; no manned, safer." From a technical perspective, manual gas checks involve gas inspectors using portable optical methane detectors to detect methane and carbon dioxide gases at designated locations. After the check, the results are recorded in a gas manual and on a whiteboard displayed on-site, and the results are communicated to the site. Throughout this process, gas check data is recorded manually, making the data prone to loss and contamination, and hindering effective analysis and utilization. Summary of the Invention

[0009] The purpose of this invention is to provide a method for unmanned wireless inspection of gas in coal mining faces, which can realize unmanned gas inspection and information management of inspection data, truly practicing the safety production concept of "less manpower, more safety".

[0010] To address the above problems, this invention provides a method for unmanned wireless inspection of gas in coal mining faces, comprising the following steps: S1 Data Acquisition: Real-time monitoring of methane and carbon dioxide data via sensors, with all sensors detecting synchronously and set to the same transmission cycle; S2 Local Display and Data Transfer: Set up n displays. Display 1 refreshes its local display content and sends the data to display 2. Display 2 simultaneously refreshes its local display content and packages [Data 1] + [Data 2] and sends it to display 3. Display 3 simultaneously refreshes its local display content and packages [Data 1] + [Data 2] + [Data 3] and sends it to display 4, and so on, until display n sends all the integrated data to the monitoring substation. S3 Data Verification and Upload: After verifying the data, the monitoring substation uploads the data to the monitoring platform via Ethernet or RS485.

[0011] To ensure the accuracy and integrity of the data, in step S2, each display node performs the following operations after receiving the upstream data packet: Verification and parsing: Verifying the integrity of data packets; Data fusion: Integrating the sensor dataset from the upstream data packet with its own latest sensor readings to generate a new, larger data packet; Caching and waiting: Newly generated data packets are cached and forwarded to the next node when their dedicated sending slot arrives.

[0012] The present invention also includes an acknowledgment and retransmission mechanism: after each upstream data packet is sent, the downstream receiver replies with an acknowledgment signal. If the sender does not receive the acknowledgment signal, it will automatically retransmit the data in the next time window.

[0013] This invention also designs a Mesh redundancy path: each display screen can communicate with the two nodes before and after it. When a display screen fails, the system will automatically activate the display screen after the failed display screen to bypass the failure point.

[0014] To ensure stability and fundamentally avoid data packet conflicts, in step S3, the monitoring substation completes clock offset correction with each node through bidirectional signaling, requiring the local clock of all display screen nodes to be highly synchronized with the master clock; the monitoring substation statically or dynamically allocates one or more dedicated time slots to each display screen node.

[0015] Furthermore, the dedicated time slot includes a transmission time slot, a reception time slot, and a sleep period; When a node's dedicated transmission slot arrives, the transmission slot is awakened, and the cached data is packaged and sent to the designated downstream node. During the transmission time slot of the upstream node, the reception time slot remains in the receiving state, listening for and receiving data packets; During non-transmit and non-receive time slots, nodes can put their wireless communication modules and processors into deep sleep mode.

[0016] In summary, compared with the prior art, the present invention has the following technical advantages and beneficial effects: The unmanned wireless inspection method for coal mining faces of the present invention solves the "last mile" problem of manual gas inspection. Even in coal mining faces where people are working, unmanned inspection can still be achieved, and the inspection process is reliable and the inspection results are accurate, bringing the possibility of ending the "manual gas inspection mode". Attached Figure Description

[0017] Figure 1 This is a flowchart of the unmanned wireless inspection method for gas in coal mining faces according to the present invention; Figure 2 This is a schematic diagram of the structure of the fully mechanized longwall mining face for high-gas thick coal seams according to the present invention; Figure 3 yes Figure 2 A sectional view along the AA direction. Detailed Implementation

[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] like Figure 1The method for unmanned wireless inspection of gas in coal mining faces shown mainly includes: S1 data acquisition, S2 local display and data transmission, and S3 data verification and uploading, to realize unmanned gas inspection and information management of inspection data.

[0020] The core architecture of this invention is a chain network of "sensor → local display screen → display screen network → substation". Integrated measurement points are deployed at equal intervals. Each measurement point includes a methane sensor and a low-power display screen unit. Through the quadruple design of "LoRa long-distance communication + time synchronization scheduling + Mesh network redundancy + wired backup", the absolute stability of data transmission is ensured.

[0021] The sensor in this invention can detect methane and carbon dioxide concentrations, and has built-in temperature compensation, device self-diagnosis, and battery voltage detection. It also features alarms for excessive concentration and low battery levels. It communicates wirelessly with a nearby display unit via Bluetooth 5.0 with extremely short range and low power consumption, actively sending data to the display. The transmission cycle can be customized, with a setting range of (1~28800) s, which is from 1 second to 8 hours. The power supply uses a mining-specific lithium battery pack, which is removable and has a battery life of at least 1 year (continuous operation).

[0022] The display screen in this invention is an e-ink screen, clearly visible under strong light, with zero power consumption for static display; it can display the real-time methane and carbon dioxide concentrations at the current measuring point, while simultaneously displaying the average and maximum values ​​of methane and carbon dioxide from the previous shift; it can also display the device's battery level, signal strength, and alarm information; the display screen has communication and routing functions, receiving data from sensors at the same location via Bluetooth; it has a built-in industrial-grade LoRa module, acting as a network node, receiving data from the previous node, integrating it, and sending it to the next node; it has a reserved RS485 wired interface as a final backup communication channel; the power supply uses a dedicated lithium battery pack, the battery is removable, and the battery life is at least one year (in continuous working mode).

[0023] In this invention, the monitoring substation receives the final data packet from a nearby display screen, which integrates the measurement data of the entire working face; the substation periodically monitors the heartbeat through the last display screen to confirm the online status of all display screens; in the Mesh network, it dynamically directs the data to follow the optimal path; it accurately locates nodes where communication is interrupted and reports them to the platform; the substation uploads the data to the monitoring platform via Ethernet / RS485 through the underground ring network.

[0024] The method of the present invention will be described in detail below.

[0025] S1 Data Acquisition: The sensors monitor methane and carbon dioxide data in real time, with all sensors detecting synchronously and set to the same transmission cycle.

[0026] S2 Local Display and Transfer: Set up n displays. Display screen 1 refreshes its local display content and sends the data to display screen 2. Display screen 2 simultaneously refreshes its local display content and packages [data from display screen 1] + [data from display screen 2] and sends it to display screen 3. Display screen 3 simultaneously refreshes its local display content and packages [data from display screen 1] + [data from display screen 2] + [data from display screen 3] and sends it to display screen 4, and so on, until display screen n sends all the integrated data to the monitoring substation. S3 Data Validation and Upload: After verifying the data, the monitoring substation uploads the data to the monitoring platform via Ethernet or RS485.

[0027] To ensure the stability of data transmission, each display node performs the following operations upon receiving an upstream data packet: Verification and parsing: Verify the integrity of the data packet (CRC check); Data fusion: Integrating the sensor dataset from the upstream data packet with its own latest sensor readings to generate a new, larger data packet; Caching and waiting: Newly generated data packets are cached and forwarded to the next node when their dedicated sending slot arrives.

[0028] After each data packet is sent, the receiver must reply with an "ACK" acknowledgment signal. If the sender does not receive an ACK, it will automatically retransmit in the next time window, retrying a maximum of 3 times. ACK stands for Acknowledgment, a feedback mechanism in data communication protocols. For example: Display screen 2 sends a data packet to display screen 3 within its dedicated time slot, then starts a retransmission timer and waits for the ACK signal. After successfully receiving the data packet, display screen 3 performs a CRC check. If the check passes, the data packet is considered error-free, and it immediately sends an ACK signal back to display screen 2. If display screen 2 receives the ACK before its timer expires, it considers the transmission successful. It clears the copy of the data packet from its buffer and prepares for the next transmission. If display screen 2's timer expires without receiving an ACK, it assumes the data packet or ACK was lost during transmission. Therefore, display screen 2 will retransmit a copy of the data packet at the next available time (the same time slot of the next superframe).

[0029] Each display screen can communicate with both the preceding and following nodes. When display screen number 3 fails, the system automatically activates a backup path: number 2 → number 4, bypassing the faulty point. This mechanism is particularly important at bends in the road.

[0030] The substation provides time synchronization for the entire network, and each display screen sends and receives data within a designated, non-overlapping time window, fundamentally avoiding data packet collisions. If eight measurement points are deployed at the back-mining face, the time synchronization skipping method is as follows: ①Time synchronization: The substation completes clock offset correction with each node through bidirectional signaling; it is required that the local clock of all display nodes be highly synchronized with the master clock (usually the error is controlled within the millisecond level).

[0031] ② Time Division Multiple Access (TDMA) Scheduling: System communication time is divided into periodic "superframes," each superframe representing a complete data acquisition and transmission cycle; within each superframe, it is further divided into several fixed-length, non-overlapping "time slots." Substations statically or dynamically allocate one or more dedicated time slots to each display node.

[0032] ③ Communication timing planning ④ Deterministic hop routing Sending slot: When a node's dedicated sending slot arrives, it is awakened, packages the cached data (including its own data and forwarded upstream data), and sends it to the designated downstream node.

[0033] Receive slot: During the transmit slot of its upstream node, it must remain in the receive state, listening for and receiving data packets.

[0034] Sleep period: During non-transmitting and non-receiving time slots, nodes can put their wireless communication modules and processors into deep sleep mode.

[0035] The following is combined Figure 2 , Figure 3 Provide specific examples.

[0036] (1) Layout of measuring points This working face is a high-gas, thick coal seam fully mechanized longwall mining face. The working face dip length is 170m, the strike length is 1600m, the length already mined is 800m, and the remaining length is 800m. The coal thickness of the working face is 8m, the coal cutting height is 3m, the coal release height is 5m, and the mining depth is 625m. It belongs to a high-gas mine. Gas drainage has been carried out before mining. According to on-site monitoring, during the mining period, the highest methane concentration of the working face was 0.38%, and the lowest methane concentration was 0.15%. The methane concentration increases in a stepwise manner from the lower corner to the upper corner. According to the requirements of the "Coal Mine Safety Regulations" (2025 edition), all manned coal mining faces (except for the intake airway) must be manually checked for methane and carbon dioxide concentrations, and the number of checks should be at least 2 times per shift. The deployment method of unmanned methane inspection in the coal mining face is shown in the figure below. As shown in the figure, the longwall face has a dip length of 170m and is equipped with 3 measuring points, each containing 1 sensor and 1 display screen. These points are located at the lower corner, middle, and upper corner, respectively, with a sensor spacing of 85m. The measuring points are named A1, A2, and A3. The return airway has a strike length of 800m and is equipped with 8 measuring points, each including 1 sensor and 1 display screen. These points are evenly spaced at 100m intervals and are named A4 to A5. 10 .

[0037] (2) Monitoring process S1: Sensor to Display. The sensor is powered by an internal battery pack, which can last for one year under continuous operation. It can detect methane and carbon dioxide concentrations in real time. By setting a patrol cycle, for example, a patrol cycle of 60 seconds, the sensor transmits the methane and carbon dioxide concentrations wirelessly to a nearby display via Bluetooth every 60 seconds. After receiving the data, the display immediately shows the detection results. In this way, each measuring point completes the detection and local display of methane and carbon dioxide concentrations. At the same time, the sensor buffers the data, waiting for the transmission slot.

[0038] S2: Inter-display transfer.

[0039] S21: Network time synchronization. The substation periodically (every 10 minutes) completes clock offset correction with each node through bidirectional signaling, and the clocks of all displays are synchronized to the millisecond level.

[0040] S22: Superframe Structure Design The system employs a fixed superframe structure, with each superframe period lasting 60 seconds, aligned with the sensor sampling period. S23: Detailed process of time synchronization jump. The complete workflow, taking display screen A3 as an example: Reception phase (time slot 1: 5-10 seconds): Display A3 remains in receiving mode during this time slot, listening for data packets from display A2. After receiving a data packet, it performs a CRC check. If the check passes, it replies with an ACK confirmation frame and integrates the received data (J1+J2) with the local buffered data (J3). Transmission phase (slot 2: 10-15 seconds): Display screen A3 switches to sending mode in this time slot, sending the integrated data packet (J1+J2+J3) to display screen A4, starting a retransmission timer (default 3 seconds), and waiting for ACK confirmation from display screen A4. Success: Upon receiving ACK from display screen A4, the sending buffer is cleared, and the device enters sleep mode. Failure: If the timer expires without receiving ACK, the device retransmits in the same time slot of the next superframe. Hibernation phase (other time slots): Turn off the LoRa transmitter and enter low power mode, keeping only Bluetooth reception (listening for sensor data) and RTC running.

[0041] S3: Substation Data Aggregation S31 Data Reception: Substation receives data from display screen A in time slot 9. 10 The complete data packet; S32 Data Validation: Verifies data integrity and timeliness; S33 Protocol Conversion: Converts LoRa data packets to the platform protocol; S34 Platform Upload: Upload to the monitoring platform via Ethernet / RS485.

[0042] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape, principle and application direction of this application should be covered within the scope of protection of this application.

Claims

1. A method for unmanned wireless inspection of gas in coal mining faces, characterized in that, Includes the following steps: S1 Data Acquisition: Real-time monitoring of methane and carbon dioxide data via sensors, with all sensors detecting synchronously and set to the same transmission cycle; S2 Local Display and Data Transfer: Set up n displays. Display 1 refreshes its local display content and sends the data to display 2. Display 2 simultaneously refreshes its local display content and packages the data from display 1 and display 2 together and sends it to display 3. Display 3 simultaneously refreshes its local display content and packages the data from display 1, display 2, and display 3 together and sends it to display 4. And so on, until display n sends all the integrated data to the monitoring substation. S3 Data Verification and Upload: After verifying the data, the monitoring substation uploads the data to the monitoring platform via Ethernet or RS485.

2. The unmanned wireless inspection method for gas in coal mining faces according to claim 1, characterized in that, In step S2, each display node performs the following operations after receiving the upstream data packet: Verification and parsing: Verifying the integrity of data packets; Data fusion: Integrating the sensor dataset from the upstream data packet with its own latest sensor readings to generate a new, larger data packet; Caching and waiting: Newly generated data packets are cached and forwarded to the next node when their dedicated sending slot arrives.

3. The unmanned wireless inspection method for gas in coal mining faces according to claim 2, characterized in that, After each upstream data packet is sent, the downstream receiver replies with an acknowledgment signal. If the sender does not receive an acknowledgment signal, it will automatically retransmit in the next time window.

4. The unmanned wireless inspection method for gas in coal mining faces according to claim 3, characterized in that, Each display screen can communicate with the nodes before and after it. When a display screen fails, the system will automatically activate the next display screen after the failed display screen to bypass the fault point.

5. The unmanned wireless inspection method for gas in coal mining faces according to claim 4, characterized in that, In step S3, the monitoring substation completes clock offset correction with each node through bidirectional signaling, requiring the local clock of all display screen nodes to be highly synchronized with the master clock; the monitoring substation statically or dynamically allocates one or more dedicated time slots to each display screen node.

6. The unmanned wireless inspection method for gas in coal mining faces according to claim 5, characterized in that, The dedicated time slot includes a transmission time slot, a reception time slot, and a sleep period; When a node's dedicated transmission slot arrives, the transmission slot is awakened, and the cached data is packaged and sent to the designated downstream node. During the transmission time slot of the upstream node, the reception time slot remains in the receiving state, listening for and receiving data packets; During non-transmit and non-receive time slots, nodes can put their wireless communication modules and processors into deep sleep mode.

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