Coal mine underground three-dimensional accurate positioning method and positioning system

Abstract

The application discloses a kind of coal mine underground three-dimensional accurate positioning method, positioning system, and positioning method includes the following steps: S1, the optimal number N of positioning base station for a to-be-measured label is determined based on improved GDOP model;S2, the geometric model of N positioning base station is constructed;S3, in N positioning base station, determine one as service base station, the rest several are adjacent base station, set the coordinates of to-be-measured label as P (x,y,z), the distance d1 between to-be-measured label and N positioning base station is calculated ~d n , the initial value of the coordinates of to-be-measured label is solved using least square method;S4, the initial value of the coordinates of to-be-measured label is iteratively updated, when meeting iteration termination condition, finally with the solution obtained by iteration as the final coordinates of to-be-measured label.The application can improve the accuracy of underground three-dimensional positioning.

Description

Technical Field

[0001] The present invention relates to the field of underground positioning technology, and in particular to a three-dimensional precise positioning method and positioning system for underground coal mines. Background Art

[0002] Mine environments are complex and ever-changing, with narrow, closed tunnels and harsh production conditions. Consequently, the safety of underground workers is often threatened by accidents such as roof collapse, water inrush, poor ventilation, and gas explosions. In the event of an accident, if there are blind spots or large positioning errors underground, ground dispatchers will be unable to obtain accurate and timely information about the underground personnel, significantly complicating rescue efforts and preventing the effective protection of underground workers. Therefore, research on precise positioning technology for underground personnel in coal mines is not only crucial to individual safety but also a crucial means of ensuring safe production in coal mines.

[0003] With the increasing mechanization and automation of coal mines, a large number of mechanized and automated equipment, robots, and production safety and environmental monitoring sensors have been deployed underground. These devices and sensors require precise location information to function during operation and monitoring. In the context of smart mine development, the application of intelligent decision-making algorithms, intelligent equipment such as drones and robots, and the need for coordinated production across the mine are placing higher demands on the location information of underground personnel, equipment, and environmental monitoring. Furthermore, the widespread application of advanced technologies such as the Internet of Things and artificial intelligence in coal mine safety production, such as intelligent mining, unmanned locomotives, and automated robotic inspections, is raising the bar for the accuracy and real-time performance of underground positioning.

[0004] However, due to the unique spatial characteristics of coal mines, current positioning services primarily rely on one-dimensional positioning services, whose accuracy and real-time performance cannot meet the demands of current technological innovation. One-dimensional positioning services cannot provide detailed location information for people and objects, nor can they support intelligent applications in complex scenarios. Therefore, developing a method for precise three-dimensional positioning in coal mines is not only an innovation in existing technology, but also a significant boost to coal mine safety and intelligent development. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a three-dimensional precise positioning method and positioning system for underground coal mines.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a three-dimensional precise positioning method for underground coal mines, comprising the following steps:

[0007] S1. Determine the optimal number N of positioning base stations for a tag to be tested based on the improved GDOP model;

[0008] S2. Construct a geometric model of N positioning base stations;

[0009] S3. Determine one of the N positioning base stations as the serving base station and the remaining ones as neighboring base stations. Assume that the coordinates of the tag to be tested are P(x, y, z). Calculate the distances d1 to d2 between the tag to be tested and the N positioning base stations. n , using the least squares method to solve the initial value of the coordinates of the tag to be tested;

[0010] S4. Iteratively update the initial value of the coordinate of the tag to be measured. When the iteration termination condition is met, the solution obtained by the iteration is finally used as the final coordinate of the tag to be measured.

[0011] Furthermore, the formula of the improved GDOP model is:

[0012]

[0013] Among them, H represents the observation matrix, R represents the covariance matrix of the observation matrix, ω space represents the spatial weight matrix, ω signal represents the signal propagation weight matrix;

[0014] The optimal number of positioning base stations N=6 determined according to the improved GDOP model.

[0015] Furthermore, the geometric models of the six positioning base stations are constructed, including:

[0016] Select four positioning base stations to form a rectangular plane, and the four positioning base stations are located at the four vertices of the rectangular plane;

[0017] The remaining two positioning base stations form a straight line, which is located above the rectangular plane.

[0018] Furthermore, the optimal distance between the positioning base stations located at the four vertices of the rectangular plane is determined by the following formula:

[0019]

[0020] Among them, L represents the optimal distance between two positioning base stations on the long side of the rectangular plane, W represents the optimal distance between two positioning base stations on the short side of the rectangular plane, and L base Represents the current distance between the two positioning base stations on the long side of the rectangular plane, W base Indicates the current distance between the two positioning base stations on the short side of the rectangular plane, L exp 、W exp Respectively represent the length and width of the tunnel experimental model, L tunnel 、W tunnelThey represent the actual length and width of the tunnel respectively, and α and β are adjustment coefficients.

[0021] Furthermore, the distance between the two positioning base stations on the straight line is the same as L, and the optimal vertical distance H between the straight line and the rectangular plane is determined as:

[0022]

[0023] Among them, H base Represents the current vertical distance between the line and the rectangular plane, H exp Indicates the height of the tunnel test model, H tunnel It represents the actual height of the roadway, and γ is the adjustment coefficient.

[0024] Furthermore, in step S3, the process of solving the initial value of the coordinates of the tag to be measured includes:

[0025] S31. Establish a three-dimensional coordinate system, where the coordinates of the serving base station are set to A(x1, y1, z1), and the coordinates of the other five adjacent base stations are set to B(x2, y2, z2), C(x3, y3, z3), D(x4, y4, z4), E(x5, y5, z5), and F(x6, y6, z6);

[0026] S32, respectively calculating the distances d1, d2, d3, d4, d5, and d6 between the tag to be tested P(x, y, z) and six positioning base stations;

[0027] S33, let the matrix

[0028]

[0029] S34, let AX = B, then the error vector when When it approaches infinity, we can find the optimal solution of AX=B. Taking the derivative of f(X) and setting the result equal to zero gives: When A Τ When A is a non-singular matrix, f(X) has a unique solution X=(A Τ A) -1 A Τ B, thereby determining the initial value of the tag to be tested.

[0030] Furthermore, the initial value of the coordinates of the tag to be measured is iteratively updated, including:

[0031] Introducing a spatial correction factor in each iteration i represents the i-th positioning base station, and k represents the k-th iteration;

[0032] Assume that the solution outputted by the kth iteration is (x k ,y k ,z k ),

[0033] The residual is

[0034] Assume that the iteration step is λ, then the solution of the k+1th iteration (x k+1 ,y k+1 ,z k+1 )for:

[0035]

[0036] ω i represents the weight factor of the i-th positioning base station.

[0037] Furthermore, the iteration termination conditions include: the number of iterations reaches a maximum number of iterations, the residual is less than a set residual value threshold, and the change in the solution is less than a set threshold.

[0038] The present invention also provides a positioning system for an underground coal mine, comprising:

[0039] A positioning antenna, the positioning antenna being installed in the tunnel, and the positioning antenna using the three-dimensional precise positioning method for underground coal mines according to any one of claims 1 to 8 to locate the tag to be tested;

[0040] An underground industrial Ethernet ring network, which is communicatively connected to the positioning antenna and is used to transmit the positioning results monitored by the positioning antenna;

[0041] The surface industrial Ethernet is connected to the underground industrial Ethernet ring network.

[0042] Furthermore, the installation positions of the positioning antenna include: straight sections of lanes, lane intersections, and lane branch points.

[0043] The beneficial effect of the present invention is that, based on the actual conditions and positioning requirements of coal mines, the present invention determines the optimal number of nodes by establishing an improved GDOP model. This not only ensures the accuracy and stability of the positioning system, but also avoids the problems of increased cost and complexity caused by too many nodes. The present invention designs a special geometric model that fully considers the spatial characteristics of coal mines, which can effectively reduce signal blind spots, improve the effectiveness and stability of signal propagation, and enhance positioning accuracy. By improving the positioning algorithm and introducing a variety of different types of parameters, the present invention can improve the accuracy and precision of the output results and reduce power consumption and calculation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the accompanying drawings and examples.

[0045] Figure 1 It is a flow chart of the three-dimensional precise positioning method for underground coal mines of the present invention.

[0046] Figure 2 This is a curve showing the relationship between the output value of the improved GDOP model of the present invention and the number of base stations.

[0047] Figure 3 It is a schematic diagram of the geometric model of the six positioning base stations of the present invention.

[0048] Figure 4 It is a schematic diagram of three-dimensional positioning of the present invention.

[0049] Figure 5 Schematic diagram of the positioning system of the present invention.

[0050] Figure 6 It is a schematic diagram of the results of the simulation test of the present invention.

[0051] Figure 7 This is a deployment diagram of two different positioning methods.

[0052] Figure 8 Schematic diagram comparing the positioning paths of the present invention and the prior art. DETAILED DESCRIPTION

[0053] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0054] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying 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, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0055] In the description of the present invention, 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 may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0056] like Figure 1 As shown, the three-dimensional precise positioning method for coal mines of the present invention includes the following steps: S1, based on the improved GDOP model, determine the optimal number N of positioning base stations for a tag to be measured. S2, construct a geometric model of N positioning base stations. S3, determine one of the N positioning base stations as a service base station and the remaining several as adjacent base stations, set the coordinates of the tag to be measured as P (x, y, z), and calculate the distance d1~d between the tag to be measured and the N positioning base stations. n , use the least squares method to solve the initial value of the coordinates of the tag to be measured. S4, iteratively update the initial value of the coordinates of the tag to be measured, and when the iteration termination condition is met, finally use the solution obtained by this iteration as the final coordinates of the tag to be measured.

[0057] It should be noted that due to the complexity and unique characteristics of the underground environment, wireless signals are subject to interference and influence from various factors during transmission, resulting in rapid signal attenuation. To ensure positioning accuracy and stability, it is often necessary to increase the number of positioning base stations to compensate for the effects of signal attenuation. However, increasing the number of positioning base stations also increases the cost and maintenance difficulty of the positioning system. First, increasing the number of base stations requires more hardware and personnel for deployment and maintenance. This not only includes the purchase cost of the base stations, but also a series of subsequent expenses such as installation, commissioning, and maintenance. Furthermore, due to the harsh underground environment and limited space, the deployment and maintenance of base stations require specialized technicians, further increasing labor costs. Second, the presence of a large number of base stations can also lead to communication interference and channel contention. Given limited wireless spectrum resources, the simultaneous operation of a large number of base stations can cause signal interference and conflict, impacting positioning accuracy and stability. Furthermore, as the number of base stations increases, the burden of data processing and transmission increases accordingly, placing higher demands on system performance and stability. Based on this, the present invention employs an improved GDOP model to determine the optimal number of positioning base stations to balance positioning accuracy and cost.

[0058] Considering the narrow and confined space characteristics of coal mine tunnels, the conventional GDOP model cannot be directly applied in the present invention. Therefore, the present invention proposes an improved GDOP model. The formula of the improved GDOP model is: Among them, H represents the observation matrix, R represents the covariance matrix of the observation matrix, ω space represents the spatial weight matrix, ω signal Represents the signal propagation weight matrix. In a narrow and long space, the positioning accuracy requirements of different positions may vary due to factors such as the layout of the work surface and the flow of personnel. Therefore, the present invention introduces the spatial weight matrix ω space , this matrix can be assigned different weights according to different spatial positions to reflect the different requirements of different areas for positioning accuracy. Factors such as terrain undulations and obstacle distribution in narrow and long spaces will affect the propagation and reception of signals. In order to more accurately evaluate the impact of these factors on positioning accuracy, the present invention introduces an observation matrix H, which contains relevant parameters of terrain and obstacles to reflect their impact on the relative position relationship between the base station and the target to be measured. In the narrow and long space of a coal mine, the non-line-of-sight propagation phenomenon is particularly prominent, and considering the possible electromagnetic interference and signal attenuation problems in the coal mine environment, the covariance matrix R of the observation matrix is ​​introduced in the present invention to more accurately describe the propagation characteristics of the signal such as reflection, refraction and scattering between obstacles. The signal propagation weight matrix ω is introduced signal , to reflect the impact of signal propagation characteristics and attenuation on positioning accuracy.

[0059] In other words, the observation matrix H is a matrix that describes the relative position relationship between the positioning base station and the target to be measured. Each row of it usually represents the observation information of a positioning base station relative to the target to be measured. The observation matrix H contains the spatial layout information of the positioning base stations. The covariance matrix R of the observation matrix is ​​an N×N symmetric positive definite matrix that reflects the noise statistical characteristics of the observation values ​​of each positioning base station. The spatial weight matrix ω space Used to reflect the different requirements of different locations for positioning accuracy. Signal propagation weight matrix ω signal Used to reflect the impact of signal propagation characteristics and attenuation on positioning accuracy.

[0060] As the number of positioning base stations N increases, the dimension of the observation matrix H increases, which can theoretically provide more positioning information. However, through simulation experiments and theoretical analysis (such as Figure 2 As shown in Figure 2, it was found that when N increases to 6, the decreasing trend of the GDOP value begins to flatten out, meaning that the improvement in positioning accuracy brought about by each additional base station becomes limited. Therefore, based on a comprehensive consideration of cost and accuracy, the present invention determines N = 6 as the optimal number of positioning base stations.

[0061] In the three-dimensional positioning method for underground coal mines, the layout of the positioning base stations is a crucial link. As the core reference of the location service, the layout of the positioning base stations has a decisive influence on the accuracy and stability of the positioning results. In the layout scheme of the positioning base stations, it is necessary to ensure that the height difference between the positioning base stations is large enough to avoid them being in the same height plane. If the horizontal height difference between the base stations is too small, it will cause great interference to the positioning accuracy of the tag to be tested on the Z axis. The layout position of each positioning base station must be accurate to ensure that they can provide stable and reliable reference signals. In addition, the layout method between the base stations also needs to be carefully designed and planned to minimize signal interference and errors. Therefore, in order to improve the accuracy and reliability of the three-dimensional positioning method for underground coal mines, the layout of the positioning base stations needs to be optimized. Based on this, the present invention constructs a special geometric model for six positioning base stations.

[0062] Specifically, constructing a geometric model of six positioning base stations includes: selecting four positioning base stations to form a rectangular plane, and the four positioning base stations are respectively located at the four vertices of the rectangular plane; the remaining two positioning base stations form a straight line, and the straight line is located above the rectangular plane. The geometric model needs to consider the following aspects: First, the positions of the positioning base stations should be distributed as evenly as possible within the entire underground space to ensure that the signal can be fully covered; second, the distance between the positioning base stations should be as large as possible to reduce the impact of errors on positioning accuracy; third, the stability and safety of the geometric model also need to be considered. Based on this, the present invention designs a special bracket structure, which has a rectangular bottom and a beam at the top, and the ends of the beam form a triangular support with the short sides of the rectangle. Among the six positioning base stations, four are arranged at the four vertices of the rectangle, and the remaining two are arranged at the two end points of the beam (such as Figure 3 (As shown). The four base stations at the bottom of the rectangle form a stable planar positioning framework, while the base stations at each end of the top crossbar provide additional vertical positioning information. This layout ensures a stable geometric structure in three-dimensional space, facilitating the precise calculation of the target object's three-dimensional coordinates through signal interaction and time difference measurement.

[0063] After determining the geometric model, factors such as the size and shape of the tunnels and the technical parameters of the base stations in the coal mine environment will affect the base station layout. Therefore, it is necessary to determine the distance between the four base stations at the bottom and the distance between the plane where the base stations are located and the crossbeam. Specifically, the optimal distance between the positioning base stations located at the four vertices of the rectangular plane is determined by the following formula: Among them, L represents the optimal distance between two positioning base stations on the long side of the rectangular plane, W represents the optimal distance between two positioning base stations on the short side of the rectangular plane, and L baseRepresents the current distance between the two positioning base stations on the long side of the rectangular plane, W base Indicates the current distance between the two positioning base stations on the short side of the rectangular plane, L exp 、W exp Respectively represent the length and width of the tunnel experimental model, L tunnel 、W tunnel α and β represent the actual length and width of the tunnel, respectively. α and β are adjustment coefficients. α is determined based on the tunnel dimensions and base station signal coverage, with 1 < α < 2. β is determined based on the tunnel height and base station signal coverage, with 0.5 < β < 1. The specific values ​​of the adjustment coefficients can be adjusted based on tunnel dimensions, base station technical parameters, and positioning accuracy requirements.

[0064] The distance between two positioning base stations on a straight line is the same as L. The optimal vertical distance H between the straight line and the rectangular plane is determined as: Among them, H base Indicates the current vertical distance between the line and the rectangular plane, H exp Indicates the height of the tunnel test model, H tunnel represents the actual roadway height, and γ is the adjustment coefficient. γ is determined based on the roadway height and the base station's signal transmission capability, with 0.25 < γ < 0.5. The specific value of the adjustment coefficient can be adjusted based on the roadway height, base station technical parameters, and positioning accuracy requirements.

[0065] The geometric structure designed by the present invention fully considers the narrow and confined space characteristics of coal mines, making the base stations more evenly distributed and able to cover a wider area. At the same time, this geometry also helps to reduce the GDOP value, thereby improving positioning accuracy.

[0066] In underground coal mines, algorithm accuracy is crucial for achieving efficient and reliable three-dimensional positioning. Currently, the most widely used three-dimensional positioning algorithm in coal mines is the conventional least squares method. However, in the unique environment of underground coal mines, this algorithm faces numerous challenges, making it difficult to achieve positioning accuracy that meets practical requirements. The confined space underground in coal mines means the communication distance between base stations and tags is relatively short, and signal transmission is easily interfered with by various obstacles. In this environment, signal attenuation is rapid, and signal quality is unstable, presenting significant challenges for positioning algorithms. The wireless communication environment underground in coal mines is harsh, making communication interference and channel contention highly likely to occur between nodes. Because a large number of nodes are distributed within underground tunnels, communication signals between them interfere with each other, resulting in signal quality degradation and reduced positioning accuracy. Furthermore, transmission delays underground are highly random, making it impossible to model the ever-changing transmission delays using a specific distribution pattern. This uncertainty further increases the difficulty and complexity of positioning algorithms. Under these circumstances, conventional least squares methods are difficult to adapt to the actual environment of underground coal mines, and their positioning accuracy falls short of practical requirements. Therefore, given the unique environment of coal mines, positioning methods should fully consider the complexity of the underground environment and effectively compensate and correct for factors such as signal attenuation, communication interference, and transmission delay to improve positioning accuracy and stability. Based on this, the present invention uses the least squares method to first solve the initial coordinates of the tag to be tested, and then updates and iterates these initial coordinates to determine the optimal solution.

[0067] like Figure 4 As shown, the process of solving the initial value of the coordinates of the tag to be measured includes:

[0068] S31. Establish a three-dimensional coordinate system. The coordinates of the serving base station are set to A(x1, y1, z1). The coordinates of the other five adjacent base stations are B(x2, y2, z2), C(x3, y3, z3), D(x4, y4, z4), E(x5, y5, z5), and F(x6, y6, z6).

[0069] S32, respectively calculating the distances d1, d2, d3, d4, d5, and d6 between the tag to be tested P(x, y, z) and the six positioning base stations;

[0070]

[0071] Expanding the above formula yields:

[0072]

[0073] In the expanded formula, the following formula is subtracted from the above formula to obtain:

[0074]

[0075] S33, let the matrix

[0076] (x, y, z) is the coordinate of the tag to be tested.

[0077] S34, let AX = B, then the error vector when When it approaches infinity, we can find the optimal solution of AX=B. Taking the derivative of f(X) and setting the result equal to zero gives: When A Τ When A is a non-singular matrix, f(X) has a unique solution X=(A Τ A) -1 A Τ B, thereby determining the initial value of the tag to be tested.

[0078] After obtaining the initial coordinates of the tag to be measured, the initial values ​​of the coordinates of the tag to be measured are iteratively updated, including: introducing a spatial correction factor in each iteration i represents the i-th positioning base station, and k represents the k-th iteration. Let the solution output by the k-th iteration be (x k ,y k ,z k ), the residual is Assume that the iteration step is λ, then the solution of the k+1th iteration (x k+1 ,y k+1 ,z k+1 )for:

[0079]

[0080]

[0081] ω i The weight factor of the i-th positioning base station can be set according to factors such as the distance between the positioning base station and the tag to be measured and the signal strength. Used to correct the influence of non-line-of-sight effects, obstacles on signal interference and other factors, spatial correction factor The value of can be set in combination with factors such as the spatial structure of the coal mine and the distribution of obstacles. For example, if a positioning base station is located at the corner of a narrow space and the signal propagation is subject to greater interference, then the spatial correction factor Set the value to a larger value.

[0082] During the iteration process, the coordinates of the tag being tested are continuously updated until the termination criteria are met. For example, the termination criteria can be set as follows: the number of iterations reaches the maximum number of iterations, the residual is less than a set residual threshold, or the change in the solution is less than a set threshold. When the iteration terminates, the last output solution is used as the final solution for the tag being tested.

[0083] Because IoT sensing nodes in underground coal mines are typically battery-powered and have limited energy, the power consumption and time consumption of positioning methods are also indicators of their performance. This method first solves the initial coordinates of the tag to be measured and then iteratively updates these initial coordinates to obtain the final positioning coordinates. Compared with conventional positioning algorithms, this method consumes less time and energy.

[0084] like Figure 5 As shown, the present invention also provides a positioning system for an underground coal mine, including: a positioning antenna, which is installed in a tunnel and adopts a three-dimensional precise positioning method in an underground coal mine to locate the tag to be tested; an underground industrial Ethernet ring network, which is communicatively connected to the positioning antenna and is used to transmit the positioning results monitored by the positioning antenna; an above-ground industrial Ethernet, which is communicatively connected to the underground industrial Ethernet ring network.

[0085] It should be noted that one positioning antenna includes six positioning base stations, and the six positioning base stations adopt the aforementioned geometric structure. Figure 6 As shown in the figure, in order to verify the effectiveness of this method, three positioning antennas are installed in the tunnel, one every 10 meters, and 50 positions are randomly selected as test points for testing. By comparing the errors between the measured values ​​and the actual values, it can be found that the total average positioning error is within 0.8m, which has a high positioning accuracy.

[0086] In addition, in order to compare the positioning antenna structure of the present invention (the distribution of the 6 positioning base stations is fixed) with the positioning effect of the common positioning base stations in a distributed manner, as shown in FIG. Figure 7 As shown in the figure, a common positioning base station and the positioning antenna of the present invention are equipped in a simulated tunnel. The common positioning base stations are grouped every 6 meters, with 3 positioning base stations in each group and 3 positioning antennas in the present invention. Data from 100 locations along the tunnel are collected for comparison. Figure 8As shown, when the positioning method of the present invention is compared with the positioning method of a distributed ordinary positioning base station, the positioning path of the present invention is closer to the actual walking path of the target. The comparative analysis of the two positioning results shows that the fixed antenna positioning has significant advantages in multiple key indicators. Specifically, the maximum error of the fixed antenna positioning is 0.78m, while the maximum error of the ordinary distributed positioning base station is 2.51m. The present invention has higher positioning accuracy stability. At the same time, the minimum error of the fixed antenna positioning is only 0.02m, which is much lower than the 0.14m of the ordinary distributed positioning, indicating that the positioning accuracy of the present invention is higher under the best conditions. From the perspective of average error, the average error of the fixed antenna positioning is 0.25m, which is also significantly lower than the 0.89m of the ordinary positioning base station, which further proves the stability of the overall positioning performance of the present invention. In addition, the standard deviation of the fixed antenna positioning is 0.16m, which is lower than the 0.44m of the ordinary positioning module, indicating that the positioning result of the present invention is less discrete and more reliable. Finally, from the perspective of the root mean square error, a comprehensive indicator of positioning accuracy, the RMSE of fixed antenna positioning is 0.29m, which is also much lower than the 0.99m of ordinary positioning modules.

[0087] Table 1

[0088]

[0089] Positioning base stations communicate with each other using the CAN bus, and data transmission is carried out through the main base station connected to the substation. In coal mine tunnels, the number and distance of positioning antennas installed need to be determined by specific quantitative indicators to ensure stable signal coverage and accurate positioning.

[0090] (1) Determination of the number of positioning antennas to be installed

[0091] Signal coverage: Setting a target signal coverage rate, such as 95% or higher, means that 95% of the roadway area will receive a signal strength sufficient for positioning. Based on the roadway's specific dimensions (e.g., length, width, height) and the signal propagation model, the minimum number of antennas required can be calculated.

[0092] Redundancy design indicator: To cope with possible antenna failures or signal interference, the proportion of redundant antennas is set at 10% to 20% of the total number of antennas. This way, even if some antennas fail, sufficient signal coverage can be maintained.

[0093] Cost-benefit analysis: Based on budget constraints, conduct a cost-benefit analysis to determine the upper limit of the number of antennas that can be tolerated while ensuring signal coverage and positioning accuracy.

[0094] (2) Quantitative planning of positioning antenna installation distance

[0095] Signal attenuation distance: Due to the attenuation characteristics of wireless signals, in coal mine tunnels, signal strength will attenuate to a certain extent after a certain distance (e.g., 50 to 100 meters). Therefore, the installation distance between adjacent antennas should be less than this attenuation distance to ensure continuous signal transmission.

[0096] Obstacle distance: Measure the distance between major obstacles in the tunnel, such as brackets, pipes, etc. The antenna installation distance should be greater than the distance between these obstacles to avoid continuous signal obstruction.

[0097] Curved sections: For curved sections in lanes, the antenna installation position and spacing need to be adjusted based on the radius and angle of the bend. Generally speaking, the antenna density should be increased in curved sections to ensure stable signal coverage.

[0098] Based on the above indicators, a specific antenna installation plan is developed. For example, in a coal mine tunnel 1000 meters long and 4 meters wide, based on calculations of signal coverage and attenuation distance, 20 antennas may be required, one every 50 meters. Furthermore, for redundancy and cost-effectiveness, two additional backup antennas can be installed. In curved sections of the tunnel, the antenna spacing may need to be shortened or the number of antennas increased to ensure continuous signal coverage. This quantitative planning allows for more precise determination of the number and spacing of antennas, ensuring optimal signal coverage and positioning accuracy within the coal mine tunnel.

[0099] When installing on site, refer to the following method:

[0100] (1) Layout planning

[0101] Before deploying antennas, a comprehensive survey and planning of the coal mine tunnels is required. First, the tunnel's orientation, branches, and key nodes must be clearly defined to determine the areas and number of antennas required. Next, based on the tunnel's width and height, the antenna installation locations and spacing must be calculated to ensure signal coverage throughout the tunnel. Finally, a detailed deployment plan must be developed, including the antenna model, number, and installation locations.

[0102] (2) Installation location selection

[0103] The antenna's installation location is crucial for signal propagation and positioning accuracy. When selecting installation locations, prioritize straight sections of the roadway and key nodes, such as intersections and branch points. Avoid installing antennas near obstacles or in areas with high humidity or dust concentrations to minimize signal attenuation and interference. Furthermore, to ensure signal continuity and stability, maintain appropriate spacing and overlap between adjacent antennas.

[0104] (3) Installation method

[0105] The antenna installation method should be selected based on the specific conditions of the tunnel and the antenna type. Generally, either wall-mounted or suspended installation methods are acceptable. For wall-mounted installation, the antenna can be fixed to the tunnel's sidewall, using the wall as support. For suspended installation, the antenna can be suspended from the tunnel's ceiling using a wire rope or chain. Regardless of the installation method, ensure that the antenna is securely and stably mounted, and not susceptible to external forces.

[0106] (4) Debugging and optimization

[0107] After the antenna is installed, commissioning and optimization are required. First, field testing verifies the antenna's signal coverage and positioning accuracy to ensure they meet actual requirements. Second, based on the test results, the antenna's installation position and angle are adjusted to optimize signal propagation. Finally, a regular maintenance and inspection mechanism is established to ensure proper antenna operation and signal stability.

[0108] In summary, the three-dimensional precise positioning method and positioning system for underground coal mines of the present invention have the following advantages:

[0109] 1. Regarding the number of positioning base stations, this paper establishes an improved GDOP model based on the actual conditions and positioning requirements of coal mines to determine the optimal number of nodes. This ensures the accuracy and stability of the positioning system while avoiding the increased cost and complexity associated with too many nodes.

[0110] 2. In terms of positioning base station layout, the present invention designs a special geometric model that fully considers the spatial characteristics of underground coal mines, which can effectively reduce signal blind spots, improve the effectiveness and stability of signal propagation, and improve positioning accuracy.

[0111] 3. In terms of positioning algorithm, the present invention introduces a variety of different types of parameters through improvement, which can improve the accuracy and precision of output results and reduce power consumption and calculation time.

[0112] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical spirit of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A three-dimensional precise positioning method for underground coal mines, characterized in that: The following steps are involved: S1. Determine the optimal number N of positioning base stations for a tag to be tested based on the improved GDOP model; S2. Construct a geometric model of N positioning base stations; S3. Determine one of the N positioning base stations as the serving base station and the remaining ones as neighboring base stations. Assume that the coordinates of the tag to be tested are P(x, y, z). Calculate the distances d1 to d2 between the tag to be tested and the N positioning base stations. n , using the least squares method to solve the initial value of the coordinates of the tag to be tested; S4, iteratively updating the initial value of the coordinate of the tag to be measured, and when the iteration termination condition is met, finally using the solution obtained by the iteration as the final coordinate of the tag to be measured; The formula of the improved GDOP model is: Among them, H represents the observation matrix, R represents the covariance matrix of the observation matrix, ω space represents the spatial weight matrix, ω signal represents the signal propagation weight matrix; The optimal number of positioning base stations N=6 determined by the improved GDOP model; Construct geometric models of six positioning base stations, including: Select four positioning base stations to form a rectangular plane, and the four positioning base stations are located at the four vertices of the rectangular plane; The remaining two positioning base stations form a straight line, which is located above the rectangular plane.

2. The three-dimensional precise positioning method for underground coal mines according to claim 1, characterized in that: The optimal distance between the positioning base stations located at the four vertices of the rectangular plane is determined by the following formula; Among them, L represents the optimal distance between two positioning base stations on the long side of the rectangular plane, W represents the optimal distance between two positioning base stations on the short side of the rectangular plane, and L base Represents the current distance between the two positioning base stations on the long side of the rectangular plane, W base Indicates the current distance between the two positioning base stations on the short side of the rectangular plane, L exp 、W exp Respectively represent the length and width of the tunnel experimental model, L tunnel 、W tunnel They represent the actual length and width of the tunnel respectively, and α and β are adjustment coefficients.

3. The three-dimensional precise positioning method for underground coal mines according to claim 2, characterized in that: The distance between two positioning base stations located on a straight line is the same as L. The optimal vertical distance H between the straight line and the rectangular plane is determined as: Among them, H base Represents the current vertical distance between the line and the rectangular plane, H exp Indicates the height of the tunnel test model, H tunnel It represents the actual height of the roadway, and γ is the adjustment coefficient.

4. The three-dimensional precise positioning method for underground coal mines according to claim 3, characterized in that: In step S3, the process of solving the initial value of the coordinates of the tag to be measured includes: S31. Establish a three-dimensional coordinate system, where the coordinates of the serving base station are set to A(x1, y1, z1), and the coordinates of the other five adjacent base stations are set to B(x2, y2, z2), C(x3, y3, z3), D(x4, y4, z4), E(x5, y5, z5), and F(x6, y6, z6); S32, respectively calculating the distances d1, d2, d3, d4, d5, and d6 between the tag to be tested P(x, y, z) and six positioning base stations; S33, let the matrix S34, let AX = B, then the error vector when When it approaches infinity, we can find the optimal solution of AX=B. Taking the derivative of f(X) and setting the result equal to zero gives: When A Τ When A is a non-singular matrix, f(X) has a unique solution X=(A Τ A) -1 A Τ B, thereby determining the initial value of the tag to be tested.

5. The three-dimensional precise positioning method for underground coal mines according to claim 4, characterized in that: Iteratively updating the initial value of the coordinates of the tag to be measured includes: Introducing a spatial correction factor in each iteration i represents the i-th positioning base station, and k represents the k-th iteration; Assume that the solution outputted by the kth iteration is (x k ,y k ,z k ), The residual is Assume that the iteration step is λ, then the solution of the k+1th iteration (x k+1 ,y k+1 ,z k+1 )for: ω i represents the weight factor of the i-th positioning base station.

6. The three-dimensional precise positioning method for underground coal mines according to claim 5, characterized in that: The iteration termination conditions include: the number of iterations reaches the maximum number of iterations, the residual is less than a set residual value threshold, and the change in the solution is less than a set threshold.

7. A positioning system for an underground coal mine, characterized in that: include: A positioning antenna, the positioning antenna being installed in the tunnel, and the positioning antenna using the three-dimensional precise positioning method for underground coal mines according to any one of claims 1 to 6 to locate the tag to be tested; An underground industrial Ethernet ring network, which is communicatively connected to the positioning antenna and is used to transmit the positioning results monitored by the positioning antenna; The surface industrial Ethernet is connected to the underground industrial Ethernet ring network.

8. The positioning system according to claim 7, wherein: The installation positions of the positioning antenna include: straight sections of lanes, lane intersections, and lane branch points.

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