Underground coal mine accurate positioning card reader direction identification method

Abstract

The invention relates to a coal mine underground accurate positioning card reader direction identification method, and belongs to the technical field of wireless communication and accurate positioning. In order to solve the problems of low direction identification precision and direction jump caused by dense metal supports, complex electromagnetic environment and serious multipath reflection in a coal mine in the prior art, a multi-source information fusion solution is provided. The method comprises the following steps: initiating a time of flight (TOF) ranging request through an identification card; based on the TOF distance difference interval gradient distribution weight point number, RSSI intensity difference interval differential weighting and CIR characteristic value peak-to-average ratio delay spread multipath component number, analyzing signal quality weighting, and combining historical direction information to dynamically compensate the weight point number; and finally determining the direction of the identification card by comparing the total weight points of the left and right antennas. According to the method, the direction identification accuracy in a complex mine environment is remarkably improved, the multi-path interference and signal fluctuation influence are effectively inhibited, the system anti-attenuation capability is enhanced, and the continuous stability of moving target direction tracking is guaranteed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wireless communication and precise positioning, and relates to a coal mine underground precise positioning card reader direction identification method. BACKGROUND

[0002] In recent years, coal mine underground precise positioning technology has been gradually promoted, but the existing system mainly relies on the traditional direction judgment method of time of flight (TOF) and received signal strength indication (RSSI). In the actual working conditions of the mine metal support dense environment, complex electromagnetic interference scene and serious signal refraction and reflection, such traditional technology exposes significant limitations. Especially in the key areas such as mining working face, multipath propagation effect, dynamic signal fluctuation and strong electromagnetic interference can greatly reduce the positioning accuracy, leading to continuous accumulation of positioning error, and serious decline of system reliability and stability.

[0003] Specifically, although the TOF ranging technology can calculate the distance by the signal transmission time, it is easily disturbed by the multipath effect in the non-line of sight (NLOS) environment, causing distance measurement deviation; the RSSI technology relies on the signal attenuation degree to judge the position, but the reflection and absorption of electromagnetic waves by the underground metal structure will cause abnormal fluctuation of signal strength, further amplifying the risk of direction misjudgment. When the two types of technology are applied alone, it is difficult to overcome the technical bottleneck of the changeable signal propagation path and frequent transient interference in the complex mine environment, ultimately causing systematic defects such as direction recognition jump and trajectory break.

[0004] The direction identification method by fusing multi-source information can effectively break through the above technical bottlenecks. This method integrates the TOF ranging difference, RSSI signal strength difference, channel impulse response (CIR) characteristic value and historical direction data, and uses the multi-dimensional parameter complementary mechanism to improve the discrimination robustness. Among them, the CIR characteristic value accurately identifies the non-line of sight interference by analyzing the peak-to-average ratio, delay spread and number of multipath components and other time domain parameters; the historical data provides direction continuity constraint to suppress the misjudgment caused by transient interference. This fusion strategy significantly improves the anti-interference ability and result stability of direction identification in the mine scene with complex tunnel structure and strong electromagnetic noise. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a coal mine underground precise positioning card reader direction identification method.

[0006] To achieve the above purpose, the present application provides the following technical scheme:

[0007] …

[0008] The beneficial effects of this invention are as follows:

[0009] (1) By integrating the time-of-flight ranging difference, the received signal strength indication signal strength difference, the channel impulse response characteristic value, and historical directional data into a multi-source information dynamic weight model, the multipath reflection interference and electromagnetic noise effects in densely packed metal support areas of mines can be effectively overcome. Joint analysis of the peak-to-average power ratio, delay spread, and number of multipath components of the channel impulse response can accurately identify non-line-of-sight propagation interference sources and significantly suppress the risk of misjudgment caused by signal distortion.

[0010] (2) A gradient weighting mechanism is adopted:

[0011] The time-of-flight ranging difference is dynamically weighted according to the distance difference interval to optimize the near-range direction identification capability;

[0012] Differential weighting of received signal strength indicators enhances sensitivity to signal attenuation over long distances.

[0013] The channel impulse response eigenvalues ​​are independently weighted to quantify the non-line-of-sight propagation suppression effect.

[0014] The multi-dimensional weight complementarity mechanism significantly reduces the negative impact of factors such as roadway obstruction and equipment interference on positioning accuracy.

[0015] (3) A dynamic smoothing compensation mechanism based on historical direction data is introduced, and additional weights are adaptively allocated based on the threshold difference in historical weights. When the continuous direction judgment results are consistent, the stability of the current round of judgment is enhanced; when encountering instantaneous signal changes, the direction jump phenomenon is reduced through historical trajectory constraints. This method significantly improves the trajectory continuity of moving targets in dynamic scenarios such as mining faces.

[0016] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0018] Figure 1 Diagram showing the installation of a card reader;

[0019] Figure 2 This is a schematic diagram for card reader orientation identification.

[0020] Figure 3 Flowchart for card reader orientation recognition. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0022] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0023] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and 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. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0024] 1. System Design

[0025] To ensure the accuracy of direction recognition in underground coal mine positioning systems, the installation of the card reader must strictly adhere to a series of technical requirements. This card reader is equipped with independent left and right UWB radio frequency circuits, and several key points require special attention during installation. First, the antennas must be installed horizontally to ensure that the signal reception directions of the left and right antennas are consistent, thus laying the foundation for accurate direction determination. Second, the antenna spacing should be greater than 3 meters. This will produce a significant signal difference when performing distance measurements and RSSI determination, optimizing the accuracy of direction recognition. Furthermore, the antenna bracket should extend appropriately to avoid signal obstruction by other equipment or obstacles in the mine tunnel, reducing interference from physical obstructions. Finally, the card reader should be placed in a suitable location in the coal mine roadway, ensuring that the front of the antenna faces the main traffic direction to maximize signal reception and improve the accuracy of positioning and direction recognition. Simultaneously, the surrounding environment should be kept away from strong electromagnetic interference to ensure that the stability of the radio frequency signal is not affected. Figure 1 As shown.

[0026] In terms of direction recognition, this method employs multi-dimensional feature fusion, combining Time-of-Flight (TOF) ranging, distance difference, RSSI signal strength difference, CIR eigenvalues ​​(including peak-to-average power ratio, delay spread, and number of multipath components), and historical direction information to achieve accurate identification of the tag's direction. First, the tag actively initiates a TOF ranging request, simultaneously performing TOF ranging with the left and right antennas of the reader. This means that ranging between the tag and the left and right antennas is completed in a single ranging process. During the ranging process, the reader records the RSSI signal strength received by the left and right antennas from the tag, as well as the CIR eigenvalues ​​of the received signals. Next, based on the distance difference, different weighting points are assigned to the left and right antennas, with the closer antenna receiving more weighting points. By analyzing the RSSI signal strength difference, the relative direction of the tag is further determined. Especially when the tag is far away, the signal strength of the front antenna is usually significantly greater than that of the back antenna; therefore, the antenna with the stronger signal receives more weighting points. Subsequently, signal quality is further analyzed using CIR eigenvalues ​​(such as peak-to-average power ratio, delay spread, and number of multipath components). These characteristics help determine which side's signal is less affected by multipath interference, and the antenna with better signal quality will receive more weight points. Finally, combining historical direction information, if the previous direction identification result indicates that the marker card is located on a certain side, that side will receive additional weight points, thereby enhancing the stability and continuity of direction determination. By comprehensively considering the above factors, the weight points of the left and right antennas are compared to determine the direction of the marker card, thus completing accurate direction identification in the coal mine. Figure 2 As shown.

[0027] 2. Direction recognition method integrating multi-source information

[0028] After the UWB reader completes distance measurement with the identification card, it determines the card's exact location based on the weighted values ​​of the left and right antennas, thus determining whether it is on the left or right. This determination process integrates multiple factors, including the TOF distance difference, RSSI signal strength difference, CIR characteristic value, and historical direction information. Each factor affects the weighted values ​​of the left and right antennas, ultimately helping the reader accurately determine the card's location. First, the reader compares the distance measurement results of the left and right antennas. The side with the shorter distance indicates that the identification card is closer to that antenna, and therefore that antenna receives a weighted value. Specifically, if the distance difference is less than 1 meter, it is assigned 1 weighted value; if the distance difference is between 1 and 3 meters, it is assigned 2 weighted values; and if the distance difference is greater than 3 meters, it is assigned 3 weighted values. This rule helps the reader more accurately assess the relative distance between the identification card and each antenna, thus providing support for subsequent direction determination.

[0029] Secondly, the card reader further determines the direction based on the RSSI signal strength difference. The side with a stronger signal usually means the card is closer to the antenna, and therefore receives a corresponding weight. The specific assignment rule is as follows: if the signal strength difference is less than 3dBm, it is assigned 1 weight; if the signal strength difference is between 3dBm and 6dBm, it is assigned 2 weights; if the signal strength difference is between 6dBm and 10dBm, it is assigned 3 weights; and if the signal strength difference is greater than 10dBm, it is assigned 5 weights. In particular, in long-distance scenarios, the RSSI signal strength difference becomes more significant, so this rule assigns more weights in long-distance situations to improve the accuracy of direction determination.

[0030] Finally, the reader analyzes the eigenvalues ​​in the CIR data to further improve the accuracy of direction determination. CIR eigenvalues ​​mainly include Peak-to-Average Power Ratio (PAPR), Delay Spread, and Multipath Component Count. These three indicators provide supplementary NLOS (Non-Line-of-Sight) identification criteria from the perspectives of signal amplitude distribution, time spread, and propagation path complexity, respectively. Specifically, PAPR reflects the ratio of extreme to average signal power, which is usually higher in NLOS environments; Delay Spread describes the time delay distribution of multipath signals, which typically increases in NLOS environments due to path diffraction and reflection; Multipath Component Count indicates the complexity of the propagation path, and in NLOS scenarios, more paths are resolved due to reflections from obstacles. By comparing the CIR eigenvalues ​​of the left and right antennas, the side less affected by non-line-of-sight signals usually indicates better signal quality and thus receives one weighted score. Each eigenvalue is calculated separately, providing an independent weighted score for each antenna. Finally, to enhance the continuity of direction determination, the reader references historical weighted scores for direction determination. If the weighted score on one side was more than 4 points higher than the other side in the previous round, the direction determination in the current round will be increased by 2 weighted scores; otherwise, only 1 weighted score will be increased. Finally, all weighted scores will be aggregated, and the side with the higher score will be the direction indicated on the card, thus achieving a more accurate direction determination. The direction recognition weight allocation rules are shown in Table 1.

[0031] Table 1

[0032]

[0033]

[0034] process:

[0035] The precise positioning and direction identification method described in this invention combines multiple technologies, integrating multi-dimensional information based on UWB ranging technology to achieve accurate direction determination. The core of the method involves a card reader working in conjunction with two directional antennas, utilizing UWB technology for high-precision Time-of-Flight (TOF) ranging to calculate the accurate distance between the identification card and the reader. In addition, the system simultaneously collects RSSI signal strength and CIR channel impulse response characteristic data. TOF ranging provides absolute distance information, while RSSI indirectly infers the relative position of the identification card by reflecting signal propagation attenuation. CIR characteristics provide signal time-domain features, helping to analyze interference factors such as multipath effects and signal attenuation. Next, the system performs direction determination based on this multi-dimensional data, further calculating the relative direction and position of the identification card by analyzing the distance difference and signal strength difference between the left and right antennas. Simultaneously, CIR characteristics, such as peak-to-average power ratio (PAPR), delay spread, and number of multipath components, are used to evaluate signal quality and propagation stability, suppress multipath interference, and optimize direction determination. Finally, by combining historical direction data, the continuity of direction determination is optimized through algorithms to avoid misjudgments caused by signal fluctuations and ensure the stability and reliability of direction determination.

[0036] By fusing multi-dimensional information, the system enhances the accuracy and stability of direction determination in complex environments. By combining Time-of-Flight (TOF) ranging differences, RSSI signal strength differences, CIR feature data, and historical trajectory data, the system employs a dynamic weighted fusion strategy. This strategy adjusts the weights of each data point in real time based on different environments and actual conditions to address various interference factors and improve the accuracy of direction determination. Specifically, the system optimizes antenna spacing to improve the discriminative power of TOF ranging differences, reducing the limitations imposed by antenna layout on ranging accuracy. Directional antenna technology enhances the directivity of the RSSI signal, effectively reducing environmental noise interference and optimizing the impact of signal strength on position determination. Regarding CIR features, the system deeply analyzes parameters such as peak-to-average power ratio (PAPR), delay spread, and the number of multipath components to suppress multipath effects and improve positioning accuracy. Finally, historical trajectory data is smoothed using a smoothing algorithm to reduce the impact of instantaneous signal fluctuations on positioning results. Especially in complex environments such as mines with dense metal supports and severe electromagnetic interference, the system can ensure stable and efficient direction determination by dynamically adjusting the fusion strategy. This approach, combining multidimensional data and adaptive adjustment strategies, enables the system to consistently output high-precision positioning information in changing environments, providing strong support for accurate navigation and safety monitoring in complex environments. For example... Figure 3 As shown.

[0037] Example 1: Standard Tunnel Environmental Direction Identification

[0038] The main roadway of the coal mine is relatively open, the density of metal supports is moderate, and the identification cards are statically installed on the top of the mine cars.

[0039] Workflow

[0040] 1. Ranging Trigger

[0041] The identification card actively initiates a Time of Flight (TOF) ranging request to the card reader.

[0042] The horizontal distance between the left and right antennas of the card reader is 3.5 meters, and the front faces the direction of the mine car's movement.

[0043] 2. Synchronous acquisition of multi-source data

[0044] Left antenna ranging value: 5.2 meters, right antenna ranging value: 3.8 meters → distance difference 1.4 meters

[0045] Left antenna Received Signal Strength Indication (RSSI): -65dBm, Right antenna RSSI: -58dBm → Strength difference of 7dBm

[0046] Left antenna channel impulse response (CIR): Peak-to-average power ratio 3.2, delay spread 28 ns, number of multipath components 4.

[0047] Right antenna CIR: Peak-to-average power ratio 2.1, delay spread 15ns, number of multipath components 2

[0048] 3. Dynamic weight allocation

[0049] TOF distance difference weighting: 1.4 meters (1-3 meters range) distance difference → right antenna + 2 points

[0050] RSSI strength difference weighting: Strength difference 7dBm (6-10dBm range) → right antenna + 3 points

[0051] CIR feature weights:

[0052] Peak-to-average power ratio: Lower for right antenna (better line-of-sight propagation) → Right antenna +1 point

[0053] Delay spread: smaller right antenna (weaker multipath interference) → right antenna +1 point

[0054] Number of multipath components: fewer on the right antenna (simpler path) → +1 point on the right antenna

[0055] Historical data weighting: Initial identification with no historical data → no additional points

[0056] 4. Direction determination

[0057] Total score for right antenna: 2 + 3 + 1 + 1 + 1 = 8 points; Total score for left antenna: 0 points.

[0058] The identification card is located on the right side of the card reader.

[0059] Example 2: Dynamic Target Tracking in Dense Metal Support Areas

[0060] The mining face has dense metal supports and strong electromagnetic interference, so identification cards are worn on the safety helmets of mobile miners.

[0061] Workflow

[0062] 1. Continuous ranging trigger

[0063] The identification card initiates a TOF ranging request every 2 seconds.

[0064] Historical record: The direction determined in the previous cycle was to the right (weight difference of 6 points).

[0065] 2. Multi-source data acquisition

[0066] Left antenna ranging value: 7.1 meters, right antenna ranging value: 8.3 meters → distance difference 1.2 meters; Left antenna RSSI: -72 dBm, right antenna RSSI: -80 dBm → intensity difference 8 dBm

[0067] Left antenna CIR: Peak-to-average power ratio 4.8, delay spread 42ns, number of multipath components 7

[0068] Right antenna CIR: Peak-to-average power ratio 5.1, delay spread 50 ns, number of multipath components 9

[0069] 3. Dynamic weight allocation

[0070] TOF distance difference weighting: 1.2 meters distance difference → left antenna + 2 points

[0071] RSSI intensity difference weighting: Intensity difference 8dBm → Left antenna + 3 points

[0072] CIR feature weights:

[0073] Peak-to-average power ratio (PAPR): High on both sides (strong non-line-of-sight interference) → Unweighted

[0074] Delay spread: Left antenna smaller → Left antenna +1 point

[0075] Multipath component count: fewer on the left antenna → +1 on the left antenna

[0076] Historical data weighting: If the difference in weights from the previous round is 6 points or more (≥ 4 points), then add 2 points to the right side.

[0077] 4. Direction determination

[0078] Total score for left antenna: 2 + 3 + 1 + 1 = 7 points; Total score for right antenna: 2 points (historical weight).

[0079] The judgment indicator card is located on the left (historical compensation has not changed the direction).

[0080] Example 3: Verification of Long-Distance Electromagnetic Interference Environment

[0081] The ventilation tunnel is over 50 meters long and is subject to electromagnetic interference from the frequency converter. Identification cards are installed on the inspection robot.

[0082] Workflow

[0083] 1. Ranging Trigger and Installation Verification

[0084] The card reader antennas are installed horizontally with a spacing of 4.0 meters to avoid sources of cable interference.

[0085] The identification card initiates a TOF ranging request.

[0086] 2. Multi-source data acquisition

[0087] Left antenna ranging value: 32.5 meters, right antenna ranging value: 35.7 meters → distance difference 3.2 meters; Left antenna RSSI: -85 dBm, right antenna RSSI: -78 dBm → intensity difference 7 dBm

[0088] Left antenna CIR: Peak-to-average power ratio 3.0, delay spread 35ns, number of multipath components 5

[0089] Right antenna CIR: Peak-to-average power ratio 2.5, delay spread 22ns, number of multipath components 3

[0090] 3. Dynamic weight allocation

[0091] TOF distance difference weighting: Distance difference 3.2 meters > 3 meters → Left antenna + 3 points

[0092] RSSI strength difference weighting: Strength difference 7dBm (6-10dBm) → right antenna + 3 points

[0093] CIR feature weights:

[0094] Peak-to-average power ratio: Right antenna is better → Right antenna +1 point

[0095] Delay spread: Right antenna is better → Right antenna +1 point

[0096] Multipath component count: Right antenna is better → Right antenna +1 point

[0097] Historical data weighting: If the difference in weights from the previous round is 3 points < 4 points, then add 1 point to the right side.

[0098] 4. Direction determination

[0099] Total points for left antenna: 3; Total points for right antenna: 3 + 1 + 1 + 1 + 1 = 7.

[0100] The determination card is located on the right (RSSI and CIR weights overcome long-distance attenuation).

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for direction identification of a precise positioning card reader in underground coal mines, characterized in that: Includes the following steps: S101: The identification card initiates a Time-of-Flight (TOF) ranging request; S102: The card reader performs TOF ranging simultaneously through the left and right antennas to obtain the distance between the identification card and the left and right antennas, and records the received signal strength indicator RSSI signal strength and the channel impulse response CIR characteristic value received by the left and right antennas. S103: Based on the TOF ranging distance difference, assign weight points to the antenna on the side with the closer distance; S104: Based on the RSSI signal strength difference, assign weight points to the antenna with the stronger signal strength; S105: Based on the CIR characteristic value, analyze the signal quality and assign weight points to the antenna with better signal quality; S106: Based on historical direction information, assign weight points to the antenna corresponding to the previous direction identification result; S107: Compare the total weight points of the left and right antennas to determine the orientation of the identification card; Among them, the weight allocation steps from S102 to S106 are executed in parallel, and S107 determines the execution direction based on the output of S103 to S106.

2. The method for orientation identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The weighting of points based on the distance difference in TOF ranging in S103 includes: assigning 1 weight when the distance difference is between 0 meters and 1 meter, assigning 2 weights when the distance difference is between 1 meter and 3 meters, and assigning 3 weights when the distance difference is greater than 3 meters.

3. The method for orientation identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The weight allocation based on RSSI signal strength difference in S104 includes: 1 weight allocated when the strength difference is between 0dBm and 3dBm, 2 weights allocated when the strength difference is between 3dBm and 6dBm, 3 weights allocated when the strength difference is between 6dBm and 10dBm, and 5 weights allocated when the strength difference is greater than 10dBm.

4. The method for orientation identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The weighting of the antenna in S105 based on CIR eigenvalues ​​includes: CIR eigenvalues ​​include peak-to-average power ratio, delay spread, and number of multipath components; when analyzing signal quality, the weighting is assigned to the antenna less affected by non-line-of-sight (NLOS).

5. The method for orientation identification of a precise positioning card reader in coal mines according to claim 4, characterized in that: In S105, a weighting point is assigned separately to each CIR feature value, with 1 point weight assigned to each of the peak-to-average power ratio, delay spread, and multipath component number.

6. The method for direction identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The weight allocation based on historical direction information in S106 includes: if the difference in weights in the previous direction identification is greater than or equal to 4 points, then 2 additional weights are allocated to that side; otherwise, 1 additional weight is allocated.

7. The method for orientation identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The method further includes a pre-installation S100: when installing the card reader, the distance between the left and right antennas is set to be greater than 3 meters, and the antennas are installed horizontally to optimize the signal reception direction; wherein, the pre-installation S100 is executed before S101.

8. The method for direction identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The signal quality analysis in S105 includes: suppressing multipath interference using CIR eigenvalues, wherein the side with better signal quality is the side with better line-of-sight propagation.

9. The method for orientation identification of a precise positioning card reader in coal mines according to claim 1, characterized in that: The direction determination of the identification card in S107 includes: dynamically fusing the weights of TOF ranging difference, RSSI signal strength difference, CIR characteristic value and historical direction information to cope with complex electromagnetic environments.

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