Tunnel positioning method based on RFID

Abstract

The invention discloses a tunnel positioning method based on RFID, and the method comprises the steps: (1), uniformly arranging a plurality of RFID readers in a tunnel, and installing an RFID electronic tag on a target device; (2) measuring and recording the coordinates of the plurality of RFID reader-writers; (3) measuring information intensity values of the electronic tag and the two adjacent RFID reader-writers at different distances to calculate the relationship between the information intensity values at different distances and the equipment distance; and (4) estimating the actual distance between the target equipment and each tag through a method of detecting the signal intensity of the RFID electronic tag entering the range by the corresponding RFID reader-writer, and estimating the position of the target equipment through a geometric mode. According to the invention, the number of the RFID reader-writers is reduced, and the cost is reduced. Therefore, transmission of synchronizing signals among the RFID reader-writers through a wired line is avoided, and the economic and labor cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel positioning, and more specifically to a tunnel positioning method based on RFID. Background Art

[0002] Tunnels are usually long, and satellite signals are blocked by obstacles in tunnels, making space monitoring difficult and difficult to effectively locate. A self-built positioning system is used to locate and monitor designated targets in a specific area. Tunnel positioning technologies also include infrared technology and ultrasonic technology, but the signal needs line-of-sight transmission, and the positioning range is relatively limited. Existing indoor positioning technologies are expensive and require a large number of devices. Summary of the invention

[0003] In order to overcome the above defects of the prior art, the present invention provides a tunnel positioning method based on RFID. The position of the positioning tag is plotted according to the information strength value of the tag read by two adjacent base stations, and the moving speed is calculated. For indoor positioning, the signal will experience reflection and refraction of obstacles during the propagation process, resulting in multiple propagation paths of the signal. In the case of severe multipath, the positioning accuracy of this positioning method is greatly reduced.

[0004] The technical solution of the present invention is as follows:

[0005] The RFID-based tunnel positioning method includes:

[0006] (1) Multiple RFID readers are evenly arranged in the tunnel, and RFID tags are installed on the target equipment;

[0007] (2) Measure the coordinates of multiple RFID readers and record them;

[0008] (3) Measure the information strength values ​​between the electronic tag and two adjacent RFID readers at different distances to deduce the relationship between the information strength value and the device distance at different distances;

[0009] (4) The signal strength of the RFID electronic tags within the range is detected by the corresponding RFID reader / writer, and the actual distance between the target device and each tag is estimated, and then the position of the target device is estimated by geometric method.

[0010] Furthermore, the distance between the two RFID readers A and B is fixed; when the electronic tag C enters the detection range of the two adjacent RFID readers A and B, the two RFID readers A and B receive the information strength value returned by the electronic tag C, and calculate the distance between the electronic tag C and the RFID readers A and B; measure the relative coordinates of the readers AB, and then calculate the coordinates of the electronic tag C based on the distance between the electronic tag C and the RFID readers A and B.

[0011] Furthermore, the specific calculation method of the geometric method is: define AB as two RFID readers, C as an electronic tag, ABC forms a triangle, the installation position coordinates of ab can be measured, the distance between the two RFID readers AB and the electronic tag C is detected, and the coordinates of the electronic tag C are calculated. The coordinates of RFID reader A are A(x1, y1) and the coordinates of reader B are B(x2, y2). The principle is to use the relationship between azimuth and trigonometric functions to calculate the coordinates C(x, y)

[0012] Calculate the angle between sides AC and AB = arccos((b 2 +c 2 -a 2 ) / 2ab)

[0013] Calculate the angle between side AB and the x-axis according to the general formula of azimuth

[0014] α=180°-90°sgn(ΔY)-artan(ΔX / ΔY), sgn is the sign function, x>0then sgn(x)=1; x<0then sgn(x)=-1; x=0then sgn(y)=0. Its function is to return the positive or negative status of a number, that is, to determine whether a number is positive, zero or negative.

[0015] Furthermore, the coordinate increment range is:

[0016] △Y≠0, if △Y=0, then let △Y be equal to an infinitesimal quantity, and the formula value range is [0°,360°].

[0017] Programming calculation:

[0018] if ΔY=0then ΔY=1E -20

[0019] α=pi-pi*sgn(ΔY) / 2-atan(ΔX / ΔY)

[0020] Endif

[0021] So the angle between side AB and the x-axis is α AB :

[0022] α AC =pi-pi*sgn(ΔY AB ) / 2-atan(ΔX AB / ΔY AB )

[0023] Calculate the azimuth of the AC side:

[0024]

[0025] According to the projection of the edge to the coordinate, calculate the coordinate of point C, that is:

[0026]

[0027] Continuously record the coordinates of the electronic tag C and its running trajectory.

[0028] Furthermore, the RFID reader is arranged on the same side close to the tunnel side wall to prevent the calculated coordinates from being located outside the tunnel.

[0029] Furthermore, the calculated coordinate results are screened in the following method: when RFID readers are arranged in the tunnel, the coordinates of each RFID reader are measured; the distance between the RFID reader and the other side of the tunnel is fixed; two adjacent RFID readers form a closed quadrilateral with the other side of the tunnel, and the calculated coordinates of point C are considered valid if they are within the closed quadrilateral area, and are considered invalid if they are outside the closed quadrilateral area.

[0030] Technical effects and advantages of the present invention:

[0031] Reduce the number of RFID readers and writers, and reduce costs. In a positioning system where multiple RFID readers and writers transmit synchronization signals, by having multiple RFID readers and writers send synchronization signals alternately, when the RFID readers and writers are distributed over a wide range and the terrain of the area to be positioned is relatively complex, each RFID reader and writer in the positioning system can also receive the synchronization signal, thereby achieving synchronization with other RFID readers and writers. This avoids the transmission of synchronization signals between RFID readers and writers through wired lines, saving economic and labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the reader signal strength;

[0033] Figure 2 This is a schematic diagram of tunnel base station deployment;

[0034] Figure 3 is a coordinate diagram;

[0035] Figure 4 This is a schematic diagram of electronic tag coordinate determination. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Embodiment 1

[0038] RFID is a contactless identification technology that uses radio frequency signals to read and transmit the information stored in RFID tags. According to the specific conditions of the site, auxiliary readers are evenly deployed as needed. The distance between the electronic tag and the RFID reader is indicated by detecting the signal strength of the electronic tag.

[0039] The antenna of the RFID reader is circularly polarized. The farther away from the reader, the lower the signal strength. Figure 1 shown.

[0040] The energy layer at which the electronic tag is read by the RFID reader / writer indicates the distance between the electronic tag and the RFID reader / writer. The smaller the energy layer data, the closer the electronic tag is to the RFID reader / writer; the larger the energy layer data, the farther the electronic tag is from the RFID reader / writer. The reader / writer sends a signal, and the RFID electronic tag receives the signal and then feeds back the signal to the reader / writer. The signal strength is different.

[0041] The delay between the RFID reader sending a signal and reading the tag information indicates the distance between the tag and the RFID reader. The shorter the delay, the closer the tag is to the RFID reader; the longer the delay, the farther the tag is from the RFID reader.

[0042] The location of the tag is determined based on the information strength value of the tag read by two adjacent RFID reader-writer base stations. The RFID-based tunnel positioning method is to locate the tag through a reader-writer with a known position. By detecting the signal strength of the RFID tag, the actual distance between the target device and each tag is estimated, and then the location of the target device is estimated by geometric method.

[0043] Embodiment 2

[0044] The information strength value and time difference data of the electronic tag and the RFID reader at different distances are measured and recorded to deduce the relationship between the information strength value and the device distance at different distances.

[0045] RFID readers are evenly arranged on one side of the tunnel. At this time, the distance between two adjacent RFID readers AB is fixed. When the electronic tag C enters the detection range of the two adjacent RFID readers AB, the two RFID readers AB receive the information strength value returned by the electronic tag C and calculate the distance between the electronic tag C and the RFID reader A and RFID reader B.

[0046] The relative coordinates of the reader AB are measured, and then the coordinates of the electronic tag C are calculated based on the distances between the electronic tag C and the RFID reader A and the RFID reader B.

[0047] like Figure 3 As shown, AB are two RFID readers, C is an electronic tag, ABC forms a triangle, the installation position coordinates of ab can be measured, the two RFID readers AB detect the distance of electronic tag C, and calculate the coordinates of electronic tag C. The coordinates of RFID reader A are A(x1,y1) and the coordinates of reader b are B(x2,y2). The principle is to use the relationship between azimuth and trigonometric function to calculate the coordinates C(x,y)

[0048] Calculate the angle between sides AC and AB = arccos((b 2 +c 2 -a 2 ) / 2ab)

[0049] Calculate the angle between side AB and the x-axis according to the general formula of azimuth

[0050] α=180°-90°sgn(ΔY)-artan(ΔX / ΔY), sgn is the sign function, x>0then sgn(x)=1; x<0then sgn(x)=-1; x=0then sgn(y)=0. Its function is to return the positive or negative status of a number, that is, to determine whether a number is positive, zero or negative.

[0051] Coordinate increment range:

[0052] △Y≠0, if △Y=0, then let △Y be equal to an infinitesimal quantity, and the formula value range is [0°,360°].

[0053] Programming calculation:

[0054] if ΔY=0then ΔY=1E -20

[0055] α=pi-pi*sgn(ΔY) / 2-atan(ΔX / ΔY)

[0056] Endif

[0057] So the angle between side AB and the x-axis is α AB :

[0058] α AC =pi-pi*sgn(ΔY AB ) / 2-atan(ΔX AB / ΔY AB )

[0059] Calculate the azimuth of the AC side:

[0060]

[0061] According to the projection of the edge to the coordinate, calculate the coordinate of point C, that is:

[0062]

[0063] Continuously record the coordinates of the electronic tag C and its running trajectory.

[0064] Embodiment 3

[0065] The RFID reader is placed close to the inner wall of the tunnel to prevent the calculated coordinates from being located outside the tunnel. Figure 2 As shown. Filter the calculated coordinate results.

[0066] The method is to measure the coordinates of each RFID reader when arranging RFID readers in the tunnel; the distance between the RFID reader and the other side of the tunnel is fixed. Two adjacent RFID readers and the other side of the tunnel form a closed quadrilateral. The calculated coordinates of point C are considered valid if they are within the closed quadrilateral area, and invalid if they are outside the closed quadrilateral area.

[0067] like Figure 4 As shown, the coordinates of the base station are A(1,1)B(9,1), and the coordinates corresponding to the tunnel side are A1(1,7)B1(9,7), X range: 1---9, X range: 1---9, the calculated coordinates are C(6,5), and the value range of C is: 1 <Cx<9,1<Cy<7。

[0068] When point C runs into the detection area of ​​A\A1\B\B1, the base stations in the adjacent areas continue to calculate the position of point C in their areas.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The tunnel positioning method based on RFID is characterized by: include: (1) Multiple RFID readers are evenly arranged in the tunnel, and RFID tags are installed on the target equipment; (2) Measure the coordinates of multiple RFID readers and record them; (3) Measure the information strength values ​​between the electronic tag and two adjacent RFID readers at different distances to deduce the relationship between the information strength value and the device distance at different distances; (4) The signal strength of the RFID electronic tags within the range is detected by the corresponding RFID reader / writer, and the actual distance between the target device and each tag is estimated, and then the position of the target device is estimated by geometric method.

2. The RFID-based tunnel positioning method according to claim 1, characterized in that: The distance between two RFID readers A and B is fixed; when electronic tag C enters the detection range of two adjacent RFID readers A and B, the two RFID readers A and B receive the information strength value returned by electronic tag C and calculate the distance between electronic tag C and RFID reader A and RFID reader B; measure the relative coordinates of reader AB, and then calculate the coordinates of electronic tag C based on the distance between electronic tag C and RFID reader A and RFID reader B.

3. The RFID-based tunnel positioning method according to claim 1, characterized in that: The specific calculation method of the geometric method is as follows: define AB as two RFID readers, C as an electronic tag, ABC forms a triangle, the installation position coordinates of ab can be measured, the two RFID readers AB detect the distance of the electronic tag C, and calculate the coordinates of the electronic tag C; the coordinates of RFID reader A are A(x1, y1) and the coordinates of reader B are B(x2, y2). The principle is to use the relationship between azimuth and trigonometric functions to calculate the coordinates C(x, y); Calculate the angle between sides AC and AB = arccos((b 2 +c 2 -a 2 ) / 2ab); Calculate the angle between side AB and the x-axis according to the general formula for azimuth; α=180°-90°sgn(ΔY)-artan(ΔX / ΔY), sgn is the sign function, x>0then sgn(x)=1; x<0then sgn(x)=-1; x=0then sgn(y)=0. Its function is to return the positive or negative status of a number, that is, to determine whether a number is positive, zero or negative.

4. The RFID-based tunnel positioning method according to claim 3, characterized in that: Coordinate increment range: △Y≠0, if △Y=0, let △Y equal to an infinitesimal quantity, the formula range is [0°,360°] programming calculation: ifΔY=0thenΔY=1E -20 α=pi-pi*sgn(ΔY) / 2-atan(ΔX / ΔY) Endif So the angle between side AB and the x-axis is α AB : α AC =pi-pi*sgn(ΔY AB ) / 2-atan(ΔX AB / ΔY AB ) Calculate the azimuth of the AC side: According to the projection of the edge to the coordinate, calculate the coordinate of point C, that is: Continuously record the coordinates of the electronic tag C and its running trajectory.

5. The RFID-based tunnel positioning method according to claim 1, characterized in that: The RFID readers are arranged on the same side close to the tunnel side wall to prevent the calculated coordinates from being located outside the tunnel.

6. The RFID-based tunnel positioning method according to claim 5, characterized in that: The calculated coordinate results are screened in the following way: when RFID readers are arranged in the tunnel, the coordinates of each RFID reader are measured; the distance between the RFID reader and the other side of the tunnel is fixed; two adjacent RFID readers form a closed quadrilateral with the other side of the tunnel, and the calculated coordinates of point C are considered valid if they are within the closed quadrilateral area, and invalid if they are outside the closed quadrilateral area.

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