Coal mine underground vehicle anti-approaching monitoring and early warning method

Abstract

The invention discloses a coal mine underground vehicle anti-approaching monitoring and early warning method, which comprises the following steps: S1, acquiring original data of an identification card worn by an underground worker through a card reading substation installed on a vehicle, and arranging a first antenna A, a second antenna B and a third antenna C on the card reading substation, the central points of the first antenna A, the second antenna B and the third antenna C are arranged in an equilateral triangle form, and a coordinate point set of the identification card is calculated according to the original data of the identification card acquired by the first antenna A, the second antenna B and the third antenna C. According to the coal mine underground vehicle anti-approaching monitoring and early warning method provided by the invention, by processing the coordinates of the identification card, the distance between an underground worker and the vehicle is monitored in real time, the situation that the worker approaches the vehicle is warned in advance, the risk that the underground worker is collided by the vehicle is reduced, and the safety of coal mine underground operation is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a coal mine underground vehicle anti-access monitoring and early warning method, and belongs to the technical field of coal mine safety. BACKGROUND

[0002] At present, in the coal mine underground operation environment, vehicles move frequently, and the safety distance monitoring between underground workers and moving vehicles is crucial. Due to the narrow space and complex environment underground, there are problems such as personnel, vehicle equipment interference, etc. The traditional personnel access monitoring method cannot accurately and timely determine the relative position of personnel and vehicles, resulting in a high risk of collision between personnel and vehicles, which seriously threatens the life safety of underground operation personnel.

[0003] At present, the anti-access monitoring research for underground personnel and vehicles is relatively less, and some existing monitoring methods mainly rely on manual observation or simple sensor monitoring, which has the defects of limited monitoring range, poor real-time performance, and large environmental interference. For example, some monitoring methods based on sensors are prone to false alarms or omissions in complex environments, and it is difficult to achieve accurate positioning of personnel position. With the advancement of intelligent mining of coal mines, there is an urgent need for an anti-access monitoring method and system that can adapt to the complex underground environment, accurately locate the position of personnel and provide real-time warning. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a coal mine underground vehicle anti-access monitoring and early warning method. By processing the coordinates of the identification card, the distance between the underground workers and the vehicle is monitored in real time, the situation of personnel approaching the vehicle is warned in advance, the risk of collision between the underground operation personnel and the vehicle is reduced, and the safety of the coal mine underground operation is improved.

[0005] To solve the above technical problems, the technical scheme of the present application is:

[0006] A coal mine underground vehicle anti-access monitoring and early warning method, comprising the following steps:

[0007] Step S1, obtaining the original data of the identification card worn by the underground personnel through the card reading substation installed on the vehicle, the card reading substation is provided with a first antenna A, a second antenna B and a third antenna C, the center points of the first antenna A, the second antenna B and the third antenna C are arranged in the form of an equilateral triangle, and the coordinates of the identification card are calculated according to the original data of the identification card obtained by the first antenna A, the second antenna B and the third antenna C;

[0008] Step S2, unifying the coordinate system of any two antennas among the first antenna A, the second antenna B and the third antenna C through rotation of the coordinate system;

[0009] Step S3, according to the point selection rule, two coordinate points in the coordinate point set are selected to form a candidate point pair, a plurality of candidate point pairs are obtained, then the point pair distance between the two coordinate points in each candidate point pair is calculated, three smallest point pair distances are selected, the average value of the three coordinate points corresponding to the three smallest point pair distances is calculated, and the average value of the coordinate is taken as the preliminary point position of the identification card;

[0010] Step S4, according to the identification card distance measured by the card reading substation, the real point position coordinate of the identification card is calculated, and the abnormal correction is carried out;

[0011] Step S5, according to the real point position coordinate of the identification card and the size of the vehicle, it is judged whether the identification card enters the dangerous range, and a warning is given when the identification card enters the dangerous range.

[0012] Further, the step S1 specifically comprises the following steps:

[0013] Any two antennas are arranged in the same coordinate system, and a coordinate point of the identification card is calculated based on the PDoA algorithm through the coordinate system of any two antennas;

[0014] According to the PDoA algorithm, another coordinate point in the opposite direction of the identification card is obtained through axis symmetry, two coordinate points of the identification card are obtained through the coordinate system of any two antennas, and finally six coordinate points of the identification card are obtained by the first antenna A, the second antenna B and the third antenna C, which form a coordinate point set.

[0015] Further, the step S3 specifically comprises the following steps:

[0016] Step S31, one coordinate point is selected from the two symmetrical coordinate points obtained from the coordinate system of the first antenna A and the second antenna B, and one coordinate point is selected from the two symmetrical coordinate points obtained from the coordinate system of the second antenna B and the third antenna C or from the two symmetrical coordinate points obtained from the coordinate system of the third antenna C and the first antenna A, which are combined into a candidate point pair (p n ,p m ), the two coordinate points p n and p m in each candidate point pair cannot be two symmetrical coordinate points in the same coordinate; in this way, all coordinate points in the coordinate point set are selected and combined into a plurality of point pairs;

[0017] Step S32, the Euclidean distance of the two coordinate points in each candidate point pair is calculated, and the calculation formula of the Euclidean distance is as follows:

[0018]

[0019] Wherein, x n and yn coordinates of the coordinate point p n x m and y m coordinates of the coordinate point p m ;

[0020] Compare the Euclidean distances of each candidate point pair, select the three smallest Euclidean distances, and record the three coordinate points corresponding to the three smallest Euclidean distances;

[0021] Step S33, calculate the coordinate average ((avg x ,avg y ) according to the three coordinate points corresponding to the three smallest Euclidean distances, and the calculation formula of the coordinate average ((avg x ,avg y ) is as follows:

[0022]

[0023] Wherein, x1 and y1, x2 and y2, x3 and y3 are the coordinate values of the three coordinate points;

[0024] Step S34, take the coordinate average as the preliminary point position of the identification card.

[0025] Further, the step S4 specifically includes the following steps;

[0026] Step S41, according to the distance r of the identification card measured by the card reading substation each time, using the inverse tangent function, calculate the angle α between the preliminary point position of the identification card and the x-axis of the pre-defined real coordinate system, and recalculate the real point position coordinates (x r ,y r ) of the identification card, and the calculation formula of the real point position coordinates (x r ,y r ) of the identification card is as follows:

[0027] x r = rcos(α);

[0028] y r = rsin(α);

[0029] According to the order, calculate each piece of data of the identification card received by the card reading substation, and obtain a series of real point position changes of the identification card;

[0030] Step S42, in the normal moving process of the identification card, the front and rear point positions of the identification card change slowly, but part of the point positions will appear jump phenomenon, set threshold value D, judge the distance d(P i-1 and P i ) between adjacent two point positions P i-1 and Pi Whether the threshold D is exceeded is determined by the following conditions:

[0031] If d(P) i-1 ,P i If )≤D, then P i For normal positioning, retain point P. i Proceed to step S44;

[0032] If d(P) i-1 ,P i If )>D, then perform an update operation on the identifier card coordinates;

[0033] Step S43: Based on historical data, limit the range of change in the point position. The current point P in the historical data... i The first three points are represented as P i-1 P i-2 and P i-3 The judgment process is as follows:

[0034] When there are fewer than three historical data points, use the previous data point P directly. i-1 The value replaces the current point P i ;

[0035] When the historical data exceeds three points, determine whether P is satisfied. i-1 The coordinates of the point = P i-2 The coordinates of the point = P i-3 The coordinates of the point; if they are satisfied, then the point P is considered to be... i This is a normal location; retain location P. i If the condition is not met, then point P is considered to be... i It's a transition point, using the previous point P. i-1 Replace the current point P i ;

[0036] Step S44: Perform extended Kalman filtering for smoothing.

[0037] Furthermore, step S5 specifically includes the following steps:

[0038] Set the vehicle's width to 'a' and its length to 'b'.

[0039] The distance between the card reader station and the side of the vehicle along its length is set to a / 2, and the distance between the card reader station and the side of the vehicle along its width is set to b / 3. The center of the card reader station is taken as the origin of the real coordinate system, and the distance between the outer edge of the danger zone and the side of the vehicle is set to 1.

[0040] The coordinate range (x) of the outer boundary of the danger zone c y c ) is represented as:

[0041]

[0042] According to the real point position coordinates (m, n) of the identification card, whether the identification card is in a dangerous range is judged, and the judgment condition is as follows:

[0043] And

[0044] If the judgment condition is met, it is determined that the real point position coordinates of the identification card are in the dangerous range, and a warning is issued; if the judgment condition is not met, it is determined that the real point position coordinates of the identification card are outside the dangerous range.

[0045] The above technical scheme is adopted, the identification card coordinates are obtained by using the equilateral triangle arrangement of three antennas based on coordinate processing transformation, the coordinates are calculated by phase difference, and a series of processing such as conversion, solution and correction are carried out, the accurate calculation of the position of the underground worker is realized, the warning range is set in combination with the size of the vehicle, the problems existing in the traditional monitoring method can be effectively solved, and a reliable technical scheme is provided for the safety distance monitoring of the coal mine underground personnel and vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 A flow chart of the coal mine underground vehicle anti-approaching monitoring and early warning method of the present application;

[0047] Figure 2 A coordinate system schematic diagram of the present application taking the first antenna A and the second antenna B as an example;

[0048] Figure 3 A coordinate system rotation schematic diagram of the present application taking the third antenna C and the first antenna A as an example;

[0049] Figure 4 A coordinate system schematic diagram of the vehicle and the dangerous range of the present application. DETAILED DESCRIPTION

[0050] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments and in combination with the drawings.

[0051] As Figure 1 shown, the present embodiment provides a coal mine underground vehicle anti-approaching monitoring and early warning method, which comprises the following steps:

[0052] Step S1, obtaining original data of an identification card worn by a person in a mine through a card reading substation installed on a vehicle, the card reading substation being provided with a first antenna A, a second antenna B and a third antenna C, center points of the first antenna A, the second antenna B and the third antenna C being arranged in the form of an equilateral triangle, the original data including an identification card distance, a phase difference and identification card coordinates; a coordinate point set of the identification card being calculated according to the original data of the identification card obtained by the first antenna A, the second antenna B and the third antenna C. Specifically,

[0053] Any two antennas are arranged in the same coordinate system, and a coordinate point of the identification card is calculated through the coordinate system of the two antennas based on the PDoA algorithm.

[0054] According to the PDoA algorithm, the coordinate point of the identification card calculated by the coordinate system of the two antennas also has a result in a relative direction, so that another coordinate point in the opposite direction of the identification card is obtained through axis symmetry, and two coordinate points of the identification card can be obtained by the coordinate system of the two antennas, and finally six coordinate points of the identification card can be obtained by the first antenna A, the second antenna B and the third antenna C, and a coordinate point set is formed.

[0055] As shown in Figure 2 , taking the first antenna A and the second antenna B as an example, a coordinate system of the first antenna A and the second antenna B is drawn. The coordinate system of the second antenna B and the third antenna C and the coordinate system of the third antenna C and the first antenna A are drawn in the same way, with the line between the two antennas as the x-axis and the line perpendicular to the upward direction as the y-axis.

[0056] The angle range of the original PDoA measurement is 0°-180°, which can only measure the angle in one direction, and the coordinate calculated by any two antennas may have a result in a relative direction. Therefore, the opposite direction coordinate point corresponding to the current coordinate point is obtained through the y-axis symmetry, and six coordinate points can be obtained by the three antennas.

[0057] PDoA is Phase Difference of Arrival, an indoor positioning algorithm. This algorithm determines the location of a signal source by measuring the phase difference between the arrival of a signal at various receivers. PDoA is based on the principle that the speed of sound, radio waves or other types of signals propagating in space is constant, and uses the arrival time and phase difference of the signal received by different receivers to calculate the geometric position of the signal source. Specifically, the PDoA algorithm usually uses at least two receivers to measure the phase difference. When the signal arrives at the two receivers, the phase difference between them depends on the distance of the signal source between the two receivers and the propagation speed of the signal in space. By combining this phase difference with the frequency and propagation speed of the signal, the distance of the signal source between the two receivers can be calculated. If there are more receivers, such calculations can be made multiple times, so that a more specific position of the signal source can be determined.

[0058] Step S2, by rotating the coordinate system, the coordinate system of any two of the first antenna A, the second antenna B and the third antenna C is unified. Specifically:

[0059] The arrangement of the three antennas is an equilateral triangle. According to the rotation of the coordinate system, the coordinate system of the second antenna B and the third antenna C and the coordinate system of the third antenna C and the first antenna A are unified and rotated to the coordinate system of the first antenna A and the second antenna B.

[0060] As shown in Figure 3 , taking the coordinate system of the third antenna C and the first antenna A as an example, the coordinate system of the third antenna C and the first antenna A is converted to the coordinate system of the first antenna A and the second antenna B by a clockwise rotation matrix. The rotation formula is:

[0061]

[0062] Taking the coordinate system of the second antenna B and the third antenna C as an example, the coordinate system of the second antenna B and the third antenna C is converted to the coordinate system of the first antenna A and the second antenna B by a counterclockwise rotation matrix. The rotation formula is:

[0063]

[0064] Step S3, according to the selection rule, two coordinate points in the coordinate point set are combined as a candidate point pair to obtain a plurality of candidate point pairs, then the point pair distance between the two coordinate points in each candidate point pair is calculated, the three smallest point pair distances are selected, and the coordinate average value of the three coordinate points corresponding to the three smallest point pair distances is calculated. The coordinate average value is taken as the preliminary point position of the identification card. Specifically:

[0065] Step S31, select one coordinate point from the two symmetrical coordinate points obtained from the coordinate system of the first antenna A and the second antenna B, select one coordinate point from the two symmetrical coordinate points obtained from the coordinate system of the second antenna B and the third antenna C, or select one coordinate point from the two symmetrical coordinate points obtained from the coordinate system of the third antenna C and the first antenna A, and combine them into a group of candidate point pairs (p n ,p m ). The two coordinate points p n and p m in each group of candidate point pairs cannot be two symmetrical coordinate points in the same coordinate; in this way, all coordinate points in the coordinate point set are selected and combined into several groups of point pairs.

[0066] Step S32, calculate the Euclidean distance of the two coordinate points in each group of candidate point pairs. The calculation formula of the Euclidean distance is as follows:

[0067]

[0068] Wherein, x n and y n are the coordinates of the coordinate point p n , and x m and y m are the coordinates of the coordinate point p m .

[0069] Compare the Euclidean distances of each group of candidate point pairs, select the three smallest Euclidean distances, and record the three coordinate points corresponding to the three smallest Euclidean distances.

[0070] Step S33, calculate the coordinate average ((avg x ,avg y ) from the three coordinate points corresponding to the three smallest Euclidean distances. The calculation formula of the coordinate average ((avg x ,avg y ) is as follows:

[0071]

[0072] Wherein, x1 and y1, x2 and y2, x3 and y3 are the coordinate values of the three coordinate points.

[0073] Step S34, take the coordinate average as the preliminary point position of the identification card.

[0074] Step S4, calculate the real point position coordinates of the identification card according to the identification card distance measured by the card reading substation, and perform abnormal correction. Specifically:

[0075] Step S41, according to the distance r of the identification card measured by the card reading substation each time, the angle a of the preliminary point of the identification card with the x-axis of the predefined real coordinate system is calculated by using the inverse tangent function, and the real point coordinate (x r ,y r ) of the identification card is recalculated, and the calculation formula of the real point coordinate (x r ,y r ) of the identification card is as follows:

[0076] x r =rcos(α);

[0077] y r =rsin(α);

[0078] According to the order, each piece of data of the identification card received by the card reading substation is solved, and a series of real point changes of the identification card are obtained.

[0079] Step S42, in the normal moving process of the identification card, the front and rear points of the identification card change slowly, but part of the points will appear jump phenomenon (such as the appearance of the shielding object in the walking direction of the underground personnel), which leads to the large distance difference between the front and rear points. A threshold value D is set, and whether the distance d(P i-1 and P i between the adjacent two points P i-1 and P i of the identification card in the normal moving process exceeds the threshold value D is judged in turn, and the judgment condition is as follows:

[0080] If d(P i-1 ,P i )≤D, P i is normal positioning, the point P i is retained, and step S44 is entered;

[0081] If d(P i-1 ,P i )>D, the identification card coordinate updating operation is performed.

[0082] Step S43, the change range of the point is limited by the historical data, the previous three points of the current point P i in the historical data are represented as P i-1 , P i-2 and P i-3 , and the judgment process is as follows:

[0083] When the historical data is less than three points, the value of the previous point P i-1 is directly used instead of the current point P i ;

[0084] When the historical data is more than three points, whether P i-1The real point coordinate of the point P is P i-2 The real point coordinate of the point P is P i-3 The real point coordinate of the point P is P i If the condition is satisfied, the point P i is considered as a normal point, and the point P i is retained. i-1 If the condition is not satisfied, the point P i is considered as a jump point, and the previous point P c is used to replace the current point P c .

[0085] Step S44, Kalman filter smoothing processing is performed. In order to further ensure the stability of the calculated point, the two-dimensional coordinates, radians, angles, etc. are smoothed by using the extended Kalman filter algorithm, so as to reduce the point with large change in the change process. The core idea is to approximate linearization of the nonlinear system through Taylor expansion, so as to apply Kalman filter for state estimation, and the steps are divided into state space modeling, initialization parameter, prediction and update.

[0086] Step S5, whether the identification card enters the dangerous range is judged according to the real point coordinate of the identification card and the size of the vehicle, and a warning is given when the identification card enters the dangerous range. Specifically:

[0087] The width of the vehicle is set as a, and the length of the vehicle is set as b.

[0088] As shown in Figure 4 , the distance between the card reading station and the side of the vehicle in the length direction is set as a / 2, the distance between the card reading station and the side of the vehicle in the width direction is set as b / 3, the center position of the card reading station is set as the origin in the real coordinate system, and the distance between the outer frame of the dangerous range and the side of the vehicle is set as 1. When the real point coordinate of the identification card enters the dangerous range, a warning is given.

[0089] The coordinate range (x c , y c ) of the outer frame of the dangerous range is represented as:

[0090]

[0091] Whether the identification card is in the dangerous range is judged according to the real point coordinate (m, n) of the identification card, and the judgment condition is as follows:

[0092] and

[0093] If the judgment condition is satisfied, it is determined that the real point coordinate of the identification card is in the dangerous range, and a warning is given. If the judgment condition is not satisfied, it is determined that the real point coordinate of the identification card is outside the dangerous range, and the underground personnel is in a safe position.

[0094] The above-described specific embodiments further illustrate the technical problems solved by the present application, technical solutions and beneficial effects, and it should be understood that the above-described are only specific embodiments of the present application and are not intended to limit the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for monitoring and early warning of vehicle approach prevention in coal mines, characterized in that, It includes the following steps: Step S1: Obtain the raw data of the identification cards worn by the personnel underground through the card reading substation installed on the vehicle. The card reading substation is equipped with a first antenna A, a second antenna B and a third antenna C. The center points of the first antenna A, the second antenna B and the third antenna C are arranged in the form of an equilateral triangle. Calculate the set of coordinate points of the identification card based on the raw data of the identification card obtained by the first antenna A, the second antenna B and the third antenna C. Step S2: By rotating the coordinate system, unify the coordinate systems of any two antennas among the first antenna A, the second antenna B, and the third antenna C; Step S3: According to the point selection rules, select two coordinate points from the set of coordinate points to form a candidate point pair, and obtain several candidate point pairs. Then, calculate the point-to-point distance between the two coordinate points in each candidate point pair, select the three smallest point-to-point distances, and calculate the average coordinate value based on the three coordinate points corresponding to the three smallest point-to-point distances. Use the average coordinate value as the initial point position of the identification card. Step S4: Calculate the true coordinates of the identification card based on the distance measured by the card reader substation, and perform anomaly correction; Step S5: Based on the actual location coordinates of the sign and the size of the vehicle, determine whether the sign has entered the danger zone, and issue a warning when the sign enters the danger zone.

2. The method for monitoring and early warning of approach prevention of vehicles in coal mines according to claim 1, characterized in that, Step S1 specifically includes the following steps: By placing any two antennas in the same coordinate system, the PDoA algorithm is used to calculate a coordinate point of the identification card using the coordinate system of any two antennas. According to the PDoA algorithm, another coordinate point in the opposite direction of the identification card is obtained through axisymmetry. The coordinate systems of any two antennas are used to obtain two coordinate points of the identification card. Finally, the first antenna A, the second antenna B, and the third antenna C obtain six coordinate points of the identification card, forming a set of coordinate points.

3. The method for monitoring and early warning of approach to vehicles in coal mines according to claim 1, characterized in that, Step S3 specifically includes the following steps: Step S31: First, select one coordinate point from the two symmetrical coordinate points obtained in the coordinate system of the first antenna A and the second antenna B. Then, select one coordinate point from the two symmetrical coordinate points obtained in the coordinate system of the second antenna B and the third antenna C, or select one coordinate point from the two symmetrical coordinate points obtained in the coordinate system of the third antenna C and the first antenna A, and combine them into a set of candidate point pairs (p). n ,p m ), the two coordinate points p in each candidate point pair n and p m They cannot be two symmetrical coordinate points under the same coordinate system; and so on, all coordinate points in the set of coordinate points are selected and combined into several pairs of points; Step S32: Calculate the Euclidean distance between the two coordinate points in each candidate point pair. The formula for calculating the Euclidean distance is as follows: Where, x n and y n Let p be the coordinate point n The coordinates, x m and y m Let p be the coordinate point m The coordinates; Compare the Euclidean distances of each pair of candidate points, select the three smallest Euclidean distances, and record the three coordinate points corresponding to the three smallest Euclidean distances. Step S33: Calculate the average coordinates ((avg) of the three coordinate points corresponding to the three smallest Euclidean distances. x ,avg y The average value of the coordinates ((avg) x ,avg y The calculation formula for ) is as follows: Where x1 and y1, x2 and y2, and x3 and y3 are the coordinate values ​​of the three coordinate points, respectively; Step S34: Use the average coordinates as the initial points on the marker card.

4. The method for monitoring and early warning of vehicle approach prevention in coal mines according to claim 1, characterized in that, Step S4 specifically includes the following steps; Step S41: Based on the distance r of the identification card obtained from each measurement at the card reader substation, use the arctangent function to calculate the angle α between the initial position of the identification card and the x-axis of the predefined real coordinate system, and recalculate the true position coordinates (x-axis and y-axis) of the identification card. r ,y r The actual location coordinates (x, y) of the identification card r ,y r The calculation formula for ) is as follows: x r =rcos(α); y r =rsin(α); By sequentially processing each piece of data received by the identification card from the card reader substation, a series of real location changes of the identification cards can be obtained; Step S42: During the normal movement of the marker card, the positions of the marker card change slowly, but some positions will jump. Set a threshold D, and sequentially judge the positions of two adjacent points P during the normal movement of the marker card. i-1 and P i The distance d(P) between them i-1 ,P i Whether the threshold D is exceeded is determined by the following conditions: If d(P) i-1 ,P i If )≤D, then P i For normal positioning, retain point P. i Proceed to step S44; If d(P) i-1 ,P i If )>D, then perform an update operation on the identifier card coordinates; Step S43: Based on historical data, limit the range of change in the point position. The current point P in the historical data... i The first three points are represented as P i-1 P i-2 and P i-3 The judgment process is as follows: When there are fewer than three historical data points, use the previous data point P directly. i-1 The value replaces the current point P i ; When the historical data exceeds three points, determine whether P is satisfied. i-1 The coordinates of the point = P i-2 The coordinates of the point = P i-3 The coordinates of the point; if they are satisfied, then the point P is considered to be... i This is a normal location; retain location P. i If the condition is not met, then point P is considered to be... i It's a transition point, using the previous point P. i-1 Replace the current point P i ; Step S44: Perform extended Kalman filtering for smoothing.

5. The method for monitoring and early warning of vehicle approach prevention in coal mines according to claim 1, characterized in that, Step S5 specifically includes the following steps: Set the vehicle's width to 'a' and its length to 'b'. The distance between the card reader station and the side of the vehicle along its length is set to a / 2, and the distance between the card reader station and the side of the vehicle along its width is set to b / 3. The center of the card reader station is taken as the origin of the real coordinate system, and the distance between the outer edge of the danger zone and the side of the vehicle is 1. The coordinate range (x) of the outer boundary of the danger zone c y c ) is represented as: Determine whether the sign is within a danger zone based on its actual location coordinates (m, n). The determination criteria are as follows: and If the judgment condition is met, the actual location coordinates of the marker card are determined to be within the danger zone, and a warning is issued; if the judgment condition is not met, the actual location coordinates of the marker card are determined to be outside the danger zone.

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