UWB-based 3D positioning method for tunnel safety monitoring

Abstract

The present invention discloses a three-dimensional positioning method based on UWB for tunnel safety monitoring. An antenna array consisting of multiple pairs of antennas is set on an anchor node. Only one DS-TWR communication is required. The node to be measured is a ranging initiator, and a ranging request frame is sent according to a set period. The anchor node is a ranging responder. In the antenna array, an antenna that first receives the request frame is used as a response antenna, and the remaining antennas are non-response antennas. The anchor node calculates the distance between each antenna and the node to be measured according to the difference in receiving timestamps of the node to be measured, the response antenna, and the non-response antenna. The coordinates of the node to be measured for rough positioning and the coordinates of multiple candidate nodes to be measured for precise positioning are obtained based on the distance and PDOA data. The coordinates of the node to be measured with the smallest distance from the coordinates of the node to be measured for rough positioning are selected from the multiple candidate node coordinates for the node to be measured as the final positioning result of the node to be measured. The present invention can effectively meet the demand for precise positioning in scenes such as subway tunnels.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel safety monitoring, and in particular to a UWB-based three-dimensional positioning method for tunnel safety monitoring. Background Art

[0002] During the construction and production process of subway tunnels, coal mine tunnels and other environments, personnel warning and traffic control rely on the positioning information of personnel and equipment; when an accident occurs, command and rescue decisions also rely on this positioning information. Therefore, the precise location of personnel, production equipment (such as shield machines, trolleys, etc.) and transportation equipment (such as small trains) in the tunnel is very important for safe production. There are no satellite positioning signals in the tunnel, and generally no public mobile communication signals. Ground-based positioning systems such as GPS or Beidou and positioning systems based on mobile communications cannot be used. Indoor positioning systems often use ultra-wideband (UWB) positioning methods. UWB-based positioning methods can achieve centimeter-level positioning accuracy. Common UWB ranging methods are achieved by calculating the time of flight (TOF), among which Doubleside two-way ranging (DS-TWR) is a commonly used ranging algorithm. The ranging initiator and responder of the DS-TWR method send their respective receiving and sending timestamps to each other, and finally calculate the flight time of the communication frame between the nodes based on the timestamp data, and finally multiply it by the corrected light speed in the environment to obtain the ranging result.

[0003] In the positioning based on ranging, the located node needs to perform distance measurement with multiple anchor nodes (whose positions are known) to calculate the position of the located node. This requires relatively dense anchor nodes, and the number of ranging communications is relatively large, which is difficult to be suitable for applications in narrow and long tunnels. In addition to the distance information between the node to be located and the positioning anchor node, if the angle between the node to be located and the antenna plane of the positioning anchor node can also be measured, the number of anchor nodes and the number of communications required for positioning can be greatly reduced. The PDOA (Phase-Difference-of-Arrival) method is a typical method for measuring the relative angle information between the node to be located and the positioning anchor node. The specific method is to install two antennas on the anchor node, and the distance d between the antennas is less than λ / 2 (λ is the wavelength of UWB). Since the distance between the node to be measured and the two antennas is different, the phases of the signals received by the two antennas are different. The relative angle value between the anchor node and the signal source can be calculated through the phase difference. The two antennas of the anchor node can only measure the angle between the node to be measured and the anchor node antenna in the same plane (or projected on the plane). Therefore, in order to obtain the three-dimensional positioning data of the node to be measured in the case of a single anchor node, multiple groups of non-parallel antennas need to be set up.

[0004] In the common three-antenna array with half-wavelength spacing, the angle measurement error is generally 3-5°. In scenes such as subway tunnels and coal mine tunnels, the construction site is similar to a long and narrow corridor, and anchor nodes are generally laid at intervals of 300-500 meters. Assuming that the person to be measured is 200 meters away from the anchor node, the angle measurement error is 4°, and the distance error is approximately 14 meters in the direction perpendicular to the tunnel. The error value has exceeded the width of construction sites such as subway tunnels, the measurement error is too large, and the availability is poor. In the positioning of multiple anchor nodes, multiple two-way ranging is often required. In the two-way bilateral ranging method, each node needs to wait for a certain time before sending a frame after receiving it. Each additional ranging will increase the waiting time multiple times, which will reduce the real-time performance of the system. Excessive positioning time also reduces the maximum number of nodes that the anchor node can measure in real time. These shortcomings are very obvious when a large number of personnel and equipment are required or when personnel and equipment are moving at high speed. In order to improve the accuracy of three-dimensional positioning in tunnels and the number of positioning nodes, it is necessary to improve the accuracy of PDOA angle measurement and reduce the number of communications. Summary of the invention

[0005] The purpose of the present invention is to overcome the large position error caused by angle measurement error in long-distance scenarios, and to provide a UWB-based three-dimensional positioning method for tunnel safety monitoring, which can effectively meet the needs of precise positioning in scenarios such as subway tunnels.

[0006] To achieve the above purpose, the technical solution provided by the present invention is: a three-dimensional positioning method based on UWB for tunnel safety monitoring, comprising:

[0007] An antenna array consisting of multiple pairs of antennas is set on the anchor node. The antenna array is placed to achieve high-precision angle measurement in the hemispherical direction with angle information redundancy.

[0008] Only one DS-TWR communication is required. In DS-TWR communication, the node to be measured is also a tag node. It is the initiator of ranging and sends a ranging request frame, namely, a Poll frame, according to a set period. After receiving the Poll frame, the anchor node sends a response frame, namely, a Resp frame, after a delay. After receiving the Resp frame, the node to be measured sends the last frame of a ranging, namely, a Final frame, after a delay. After receiving the Final frame, the anchor node completes a DS-TWR communication. The antenna array of the anchor node can obtain the arrival phase difference data of the Poll frame and the Final frame sent by the node to be measured, namely, PDOA data. The anchor node is the ranging responder. In the antenna array, an antenna that first receives the request frame is used as the responding antenna, and the remaining antennas are non-responding antennas. Both the responding antenna and the non-responding antenna perform ranging with the node to be measured.

[0009] The anchor node calculates the distance between each antenna and the node to be measured based on the difference in the receiving timestamps of the node to be measured, the responding antenna and the non-responding antenna, and then obtains the roughly positioned coordinates of the node to be measured and the precisely positioned coordinates of multiple candidate nodes to be measured based on the calculated distance and PDOA data. Finally, the coordinates of the multiple candidate nodes to be measured with the shortest distance to the roughly positioned coordinates of the node to be measured are selected as the final positioning result of the node to be measured.

[0010] Furthermore, the antenna array uses three pairs of antennas, namely, antenna No. 1 and antenna No. 2 form a pair, antenna No. 3 and antenna No. 4 form a pair, and antenna No. 5 and antenna No. 6 form a pair; the antenna array is arranged in an equilateral triangle as a whole, including two inner and outer equilateral triangles, wherein antenna No. 1, antenna No. 4 and antenna No. 6 form an outer equilateral triangle, and antenna No. 2, antenna No. 3 and antenna No. 5 form an inner equilateral triangle, the side length of the outer equilateral triangle is twice the wavelength of UWB, the distance between the two antennas in each pair of antennas is less than half the wavelength of UWB, and the connecting line of each pair of antennas is perpendicular to the opposite sides of the inner and outer equilateral triangles.

[0011] Further, the specific process of the DS-TWR communication is as follows:

[0012] The node to be measured sends a ranging request frame, namely a Poll frame, at a set period and adds the sending timestamp of the Poll frame to the frame;

[0013] The antenna array of the anchor node receives the Poll frame of the node to be tested, and the responding antenna generates a Poll frame reception timestamp and actively delays After a delay, the Resp frame is sent to reply to the node under test. At the same time, the antenna array can obtain the PDOA data of the Poll frame sent by the node under test. During this time, the remaining non-responding antennas in the antenna array receive the Poll frame in turn, and each antenna generates a corresponding Poll frame reception timestamp, and records the difference between the Poll frame reception timestamp of each non-responding antenna and the Poll frame reception timestamp of the responding antenna. ;

[0014] The node under test receives the Resp frame, generates a Resp frame receiving timestamp, and the node under test actively delays The Final frame is sent after the time, where the Final frame contains the receiving timestamp of the Resp frame of the node to be tested and the sending timestamp data of the Final frame;

[0015] The response antenna receives the Final frame, generates a Final frame reception timestamp, and calculates , , , The four time difference data have the following ranging formula:

[0016] (1);

[0017] In the formula, is the calculated value of the flight time of the frame between the response antenna and the tag node, is the calculated value of the distance between the response antenna and the tag node, The time difference between the time when the node to be tested sends the Poll frame and receives the Resp frame. The time difference between the anchor node sending the Resp frame and receiving the Final frame. Preset the delay time for the node to be tested. Preset delay time for anchor nodes, C is the speed of light in air;

[0018] The non-responding antennas of the anchor node then receive the Final frame in turn and generate corresponding receiving timestamps. At the same time, the antenna array of the anchor node can obtain the PDOA data of the Final frame sent by the node under test and calculate the difference between the Final frame receiving timestamp of each non-responding antenna and the Final frame receiving timestamp of the responding antenna. , the non-responding antenna obtains the ranging result according to the following formula (2):

[0019] (2);

[0020] In the formula, is the calculated value of the flight time of the frame between the non-responding antenna and the tag node, is the calculated value of the distance between the non-responsive antenna and the tag node; according to the above formula (2), the distance from each non-responsive antenna to the node to be measured is calculated in turn, and the distance from each of the six antennas to the node to be measured is obtained.

[0021] Furthermore, when the ranging process communication between the node to be measured and the anchor node is completed, that is, a DS-TWR communication is completed, the ranging node can enter the sleep state in time to save energy; the six antennas of the anchor node will receive the UWB signals of the Poll frame and the Final frame in a DS-TWR communication with the node to be measured, so that each pair of antennas obtains two PDOA phase differences, one for the Poll frame and one for the Final frame, and the average of the two PDOA phase differences of each pair of antennas is taken as the receiving phase difference of the pair of antennas in this DS-TWR communication;

[0022] Assume that the antenna plane of the anchor node is placed plane, with the center of gravity of the equilateral triangle as the coordinate origin, and the side length of the triangle is , is the wavelength of UWB, the distance between the two antennas in each pair of antennas is a, and the three-dimensional coordinates of the node to be measured are , then there are 6 distance relationships for the three pairs of antennas:

[0023] (3);

[0024] In the formula, , , , , , are the distances from the node to be tested to antennas 1, 2, 3, 4, 5, and 6 respectively; for Antenna number, for Antenna number, , is the average distance from the two antennas in each pair of antennas to the node to be measured, for Antenna and The phase difference of the signal received by the antenna is expressed in radians, as shown in the following formula (4):

[0025] (4);

[0026] The coordinates of the node to be measured for rough positioning are obtained by formulas (3) and (4): , expressed as:

[0027] (5).

[0028] Furthermore, based on the phase difference between antenna No. 1, antenna No. 4 and antenna No. 6, the distance formula of the three antennas is:

[0029] (6);

[0030] According to the same solution method as the above formula (4), we have:

[0031] (7);

[0032] (8);

[0033] In the formula, The spacing is Candidate value of the true phase difference between two distant antennas, is the phase difference between two long-distance antennas measured by the UWB chip, The true value of The measured values ​​differ , , thus obtaining the coordinates of the node to be measured in precise positioning Three candidate values ​​for .

[0034] Furthermore, based on the three candidate values ​​of coarse positioning and fine positioning, the final precise positioning coordinates are obtained according to the following formula: for:

[0035] (9);

[0036] In the formula, for Vector coordinate representation, for The vector coordinates of the node are expressed as follows, that is, the coordinates of the node with the smallest distance between the coarse positioning and the fine positioning are selected as the final positioning result of the node to be measured.

[0037] Furthermore, the anchor node accurately locates the coordinates of the node to be measured. Sent to the security monitoring system.

[0038] Furthermore, each antenna in the antenna array is equipped with the same chip, all chips are clocked by the same crystal oscillator, and the distance from the crystal oscillator to each chip is equal.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] 1. The antenna array of the present invention has hemispherical angle measurement capability and high angle measurement accuracy, realizes high-precision three-dimensional positioning of a single anchor point, and meets the precise positioning requirements in scenes such as subway tunnels.

[0041] 2. The ranging method proposed in the present invention can measure the distance between each antenna of the anchor node and the node to be measured, without assuming that the distances between the node to be measured and all antennas of the anchor node are approximately equal, thereby improving the positioning accuracy at close distances.

[0042] 3. In the double side two-way ranging (DS-TWR) method used in the present invention, the non-responsive antenna of the anchor node does not need to send communication frames. The entire ranging process only requires one two-way bilateral ranging communication, which will not increase the number of communications and improves the density of ranging personnel and equipment.

[0043] 4. The bilateral two-way ranging data frame used in the present invention is optimized for battery-powered tag nodes, which reduces the number of reception times of the tag nodes and the amount of computation of the tag nodes, thereby extending the usable time of the battery-powered tag nodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the antenna array of the anchor node.

[0045] Figure 2Schematic diagram of bilateral two-way ranging for the response antenna.

[0046] Figure 3 Schematic diagram of bilateral two-way ranging for non-responsive antennas.

[0047] Figure 4 Flow chart of the method of the present invention.

[0048] Figure 5 This is a schematic diagram of the rough positioning range.

[0049] Figure 6 This is a schematic diagram of the precise positioning range. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0051] This embodiment discloses a UWB-based three-dimensional positioning method for tunnel safety monitoring, the details of which are as follows:

[0052] An antenna array consisting of three pairs of antennas is set on the anchor node. The position of the antenna array is used to achieve high-precision angle measurement in the hemispherical direction, with a certain angle information redundancy to improve accuracy and robustness.

[0053] like Figure 1 As shown, the antenna array uses three pairs of antennas, namely, antenna No. 1 and antenna No. 2 form a pair, antenna No. 3 and antenna No. 4 form a pair, and antenna No. 5 and antenna No. 6 form a pair; the antenna array is arranged in an equilateral triangle as a whole, including two inner and outer equilateral triangles, wherein antenna No. 1, antenna No. 4 and antenna No. 6 form an outer equilateral triangle, and antenna No. 2, antenna No. 3 and antenna No. 5 form an inner equilateral triangle, the side length of the outer equilateral triangle is twice the wavelength of UWB, the distance between the two antennas in each pair of antennas is slightly less than half the wavelength of UWB, and the connection line of each pair of antennas is perpendicular to the opposite sides of the two inner and outer equilateral triangles.

[0054] In this example, the DW1000 chip is used as the receiving chip of the antenna. Each antenna in the antenna array needs to be equipped with a DW1000 chip, for a total of 6 chips; all DW1000 chips are clocked by the same crystal oscillator, and the distance from the crystal oscillator to each DW1000 chip is equal. STM32H750VBT6 is used as the main control chip, and the SPI interface is used to communicate with the DW1000 chip; the main control chip is responsible for the control of the ranging process and the data calculation of the positioning algorithm. DW1000 receives the sending and receiving commands of the main control chip through the SPI interface, sends the ranging frame or receives the ranging frame at the time specified in the command and generates a high-precision receiving timestamp and receiving phase value. After receiving, it notifies the main control chip to read the data.

[0055] Figure 2 and Figure 3 This is the bilateral two-way ranging (DS-TWR) process between the node to be measured X and the anchor node A. The node to be measured (also the tag node) is the initiator of ranging and sends ranging request frames, namely Poll frames, according to the set period. After the anchor node receives the Poll frame, it delays for a period of time and then sends a response frame, namely Resp frame. After the node to be measured receives the Resp frame, it delays for a period of time and then sends the last frame of ranging, namely Final frame. After the anchor node receives the Final frame, a DS-TWR ranging is completed. The entire communication frame consists of Poll frames, Resp frames and Final frames. The positioning method flow of this example is as follows: Figure 4 As shown, the details are as follows:

[0056] Step 401 (start positioning communication): the node to be measured sends a ranging request frame, namely a Poll frame, at a certain period, and adds the sending timestamp of this Poll frame to the frame.

[0057] Step 402 (Complete positioning communication): The antenna array of the anchor node receives the Poll frame of the node to be measured. The first antenna that receives the Poll frame becomes the response antenna of the anchor node, and the other antennas are non-response antennas. The response antenna of the anchor node generates a Poll frame reception timestamp. Active delay of the response antenna After a certain time, a Resp frame is sent to reply to the node under test; at the same time, the antenna array of the anchor node can obtain the PDOA (Phase Difference of Arrival) data of the Poll frame sent by the node under test.

[0058] The response antenna is delayed During this time, the remaining non-responding antennas in the antenna array of the anchor node receive the Poll frame in turn, and each antenna generates a corresponding Poll frame reception timestamp. The difference between the Poll frame reception timestamp of each non-responding antenna and the Poll frame reception timestamp of the responding antenna is recorded. ,like Figure 3 shown.

[0059] The node under test receives the Resp frame, generates a Resp frame receiving timestamp, and the node under test actively delays The Final frame is sent after the time. The Final frame contains the receiving timestamp of the Resp frame of the node to be tested and the sending timestamp data of the Final frame.

[0060] Step 403 (obtaining distance and phase difference data): The response antenna of the anchor node receives the Final frame and generates a Final frame reception timestamp. Figure 2 In , , , The four time difference data have the following ranging formula:

[0061] (1);

[0062] In the formula, is the calculated value of the flight time of the frame between the response antenna and the tag node, is the calculated value of the distance between the responding antenna and the tag node (frame flight time multiplied by the speed of light), The time difference between the time when the node to be tested sends the Poll frame and receives the Resp frame. The time difference between the anchor node sending the Resp frame and receiving the Final frame. Preset the delay time for the node to be tested. Preset delay time for anchor nodes, C is the speed of light in air.

[0063] The non-responsive antenna ranging process of the anchor node is as follows: Figure 3 As shown in the figure, the non-responding antennas of the anchor node then receive the Final frame in turn and generate corresponding receiving timestamps. At the same time, the antenna array of the anchor node can obtain the PDOA (Phase Difference of Arrival) data of the Final frame sent by the node under test. Calculate the difference between the Final frame receiving timestamp of each non-responding antenna and the Final frame receiving timestamp of the responding antenna. , the non-responding antenna obtains the ranging result according to the following formula:

[0064] (2);

[0065] In the formula, is the calculated value of the flight time of the frame between the non-responding antenna and the tag node, is the calculated value of the distance between the non-responsive antenna and the tag node (flight time multiplied by the speed of light). According to the above formula (2), the distance from each non-responsive antenna to the node to be tested is calculated in turn, and the distance from each of the six antennas to the node to be tested is obtained.

[0066] Step 404 (coarse positioning): After the ranging process between the node to be measured and the anchor node is completed, the ranging node can enter the sleep state in time to save energy; the six antennas of the anchor node will receive the UWB signals of the Poll frame and the Final frame in a DS-TWR communication with the node to be measured, so that each pair of antennas obtains two PDOA phase differences, including one Poll frame and one Final frame, and the average of the two PDOA phase differences of each pair of antennas is taken as the receiving phase difference of the pair of antennas in this DS-TWR communication.

[0067] Assume that the anchor node antenna plane is placed plane, with the center of gravity of the equilateral triangle as the coordinate origin, and the side length of the triangle is , is the wavelength of UWB, and the distance between each pair of antennas is a. Assume that the three-dimensional coordinates of the node to be measured are There are 6 distance relationships between the three pairs of antennas:

[0068] (3);

[0069] In the formula, , , , , , are the distances from the node to be tested to antennas 1, 2, 3, 4, 5, and 6 respectively; for Antenna number, for Antenna number, , is the average distance from the two antennas in each pair of antennas to the node to be measured, for Antenna and The phase difference (expressed in radians) of the signal received by the antenna is shown in equation (4):

[0070] (4);

[0071] The coordinates of the node to be measured for rough positioning are obtained by formulas (3) and (4): , expressed as:

[0072] (5);

[0073] Step 405 (precise positioning): Based on the phase difference between antenna No. 1, antenna No. 4 and antenna No. 6, the distance formula of the three antennas is:

[0074] (6);

[0075] According to the same solution method as the above formula (4), we have:

[0076] (7);

[0077] (8);

[0078] In the formula, are two long-distance antennas (i.e., the distance between them is The candidate value of the true phase difference between the two antennas) is is the phase difference between two long-distance antennas measured by the UWB chip, The true value of The measured values ​​differ , , thus obtaining the coordinates of the node to be measured in precise positioning Three candidate values ​​for .

[0079] Step 406: (Precise coordinate positioning): Based on the three candidate values ​​of coarse positioning and fine positioning, the final precise positioning coordinates are obtained according to the following formula: for:

[0080] (9);

[0081] In the formula, for Vector coordinate representation, for The vector coordinates of the node are expressed as follows, that is, the coordinates of the node with the smallest distance between the coarse positioning and the fine positioning are selected as the final positioning result of the node to be measured.

[0082] Finally, the anchor node accurately locates the coordinates of the node to be measured Sent to the security monitoring system.

[0083] Figure 5 The rough positioning range effect diagram is given. If the node to be measured (a device to be positioned) is located on the upper track. Although the UWB ranging accuracy is about 30cm, which is much smaller than the track width, the node to be measured may be located at any point on the arc with the anchor node as the center, the ranging result as the radius, and the angle measurement error as the angle range. The positioning method using a general small-pitch antenna array (i.e. relying only on Figure 2 The DS-TWR and the corresponding PDOA coarse positioning method) have large angle errors. At long distances, the positioning result of the device will produce large position errors, making it impossible to determine whether the device is located on the upper track or the lower track. Figure 6 The precise positioning result of the present invention is given. Since the angle measurement error is reduced to within a quarter of the rough positioning angle error, the positioning accuracy is greatly improved and no misjudgment error will occur.

[0084] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A UWB-based three-dimensional positioning method for tunnel safety monitoring, characterized in that: include: An antenna array consisting of multiple pairs of antennas is set on the anchor node. The antenna array is placed to achieve high-precision angle measurement in the hemispherical direction with angle information redundancy. Only one DS-TWR communication is required. In DS-TWR communication, the node to be measured is also a tag node. It is the initiator of ranging and sends a ranging request frame, namely, a Poll frame, according to a set period. After receiving the Poll frame, the anchor node sends a response frame, namely, a Resp frame, after a delay. After receiving the Resp frame, the node to be measured sends the last frame of a ranging, namely, a Final frame, after a delay. After receiving the Final frame, the anchor node completes a DS-TWR communication. The antenna array of the anchor node can obtain the arrival phase difference data of the Poll frame and the Final frame sent by the node to be measured, namely, PDOA data. The anchor node is the ranging responder. In the antenna array, an antenna that first receives the request frame is used as the responding antenna, and the remaining antennas are non-responding antennas. Both the responding antenna and the non-responding antenna perform ranging with the node to be measured. The anchor node calculates the distance between each antenna and the node to be measured based on the difference in the receiving timestamps of the node to be measured, the responding antenna, and the non-responding antenna, and then obtains the roughly positioned coordinates of the node to be measured and the precisely positioned coordinates of multiple candidate nodes to be measured based on the calculated distance and PDOA data. Finally, the coordinates of the candidate nodes to be measured with the smallest distance to the roughly positioned coordinates of the node to be measured are selected from the multiple candidate node coordinates as the final positioning result of the node to be measured. The antenna array uses three pairs of antennas, namely, antenna No. 1 and antenna No. 2 form a pair, antenna No. 3 and antenna No. 4 form a pair, and antenna No. 5 and antenna No. 6 form a pair; the antenna array is arranged as an equilateral triangle as a whole, including two inner and outer equilateral triangles, wherein antenna No. 1, antenna No. 4 and antenna No. 6 form an outer equilateral triangle, and antenna No. 2, antenna No. 3 and antenna No. 5 form an inner equilateral triangle, the side length of the outer equilateral triangle is twice the wavelength of UWB, the distance between the two antennas in each pair of antennas is less than half the wavelength of UWB, and the connection line of each pair of antennas is perpendicular to the opposite sides of the inner and outer equilateral triangles; When the distance measurement process between the node to be measured and the anchor node is completed, that is, a DS-TWR communication is completed, the node to be measured can enter the sleep state in time to save energy; the six antennas of the anchor node will receive the UWB signals of the Poll frame and the Final frame in a DS-TWR communication with the node to be measured, so that each pair of antennas obtains two PDOA phase differences, including one Poll frame and one Final frame, and the average of the two PDOA phase differences of each pair of antennas is taken as the receiving phase difference of the pair of antennas in this DS-TWR communication; Assume that the antenna plane of the anchor node is placed plane, with the center of gravity of the equilateral triangle as the coordinate origin, and the side length of the triangle is , is the wavelength of UWB, the distance between the two antennas in each pair of antennas is a, and the three-dimensional coordinates of the node to be measured are , then there are 6 distance relationships for the three pairs of antennas: （3）； In the formula, , , , , , are the distances from the node to be tested to antennas 1, 2, 3, 4, 5, and 6 respectively; for Antenna number, for Antenna number, , is the average distance from the two antennas in each pair of antennas to the node to be measured, for Antenna and The phase difference of the signal received by the antenna is expressed in radians, as shown in the following formula (4): （4）； The coordinates of the node to be measured for rough positioning are obtained by formulas (3) and (4): , expressed as: （5）； Based on the phase difference between antenna No. 1, antenna No. 4 and antenna No. 6, the distance formula of the three antennas is: （6）； According to the same solution method as the above formula, we have: （7）； （8）； In the formula, The spacing is Candidate value of the true phase difference between two distant antennas, is the phase difference between two long-distance antennas measured by the UWB chip, The true value of The measured values ​​differ , , thus obtaining the coordinates of the node to be measured in precise positioning Three candidate values ​​for ; According to the three candidate values ​​of coarse positioning and fine positioning, the final precise positioning coordinates are obtained according to the following formula: for: （9）； In the formula, for Vector coordinate representation, for The vector coordinates of the node are expressed as follows, that is, the coordinates of the node with the smallest distance between the coarse positioning and the fine positioning are selected as the final positioning result of the node to be measured.

2. The UWB-based three-dimensional positioning method for tunnel safety monitoring according to claim 1 is characterized in that: The specific process of the DS-TWR communication is as follows: The node to be measured sends a ranging request frame, namely a Poll frame, at a set period and adds the sending timestamp of the Poll frame to the frame; The antenna array of the anchor node receives the Poll frame of the node to be tested, and the responding antenna generates a Poll frame reception timestamp and actively delays After a delay, the Resp frame is sent to reply to the node under test. At the same time, the antenna array can obtain the PDOA data of the Poll frame sent by the node under test. During this time, the remaining non-responding antennas in the antenna array receive the Poll frame in turn, and each antenna generates a corresponding Poll frame reception timestamp, and records the difference between the Poll frame reception timestamp of each non-responding antenna and the Poll frame reception timestamp of the responding antenna. ; The node under test receives the Resp frame, generates a Resp frame receiving timestamp, and the node under test actively delays The Final frame is sent after the time, where the Final frame contains the receiving timestamp of the Resp frame of the node to be tested and the sending timestamp data of the Final frame; The response antenna receives the Final frame, generates a Final frame reception timestamp, and calculates , , , The four time difference data have the following ranging formula: （1）； In the formula, is the calculated value of the flight time of the frame between the response antenna and the tag node, is the calculated value of the distance between the response antenna and the tag node, The time difference between the time when the node to be tested sends the Poll frame and receives the Resp frame. The time difference between the anchor node sending the Resp frame and receiving the Final frame. Preset the delay time for the node to be tested. Preset delay time for anchor nodes, C is the speed of light in air; The non-responding antennas of the anchor node then receive the Final frame in turn and generate corresponding receiving timestamps. At the same time, the antenna array of the anchor node can obtain the PDOA data of the Final frame sent by the node under test and calculate the difference between the Final frame receiving timestamp of each non-responding antenna and the Final frame receiving timestamp of the responding antenna. , the non-responding antenna obtains the ranging result according to the following formula (2): （2）； In the formula, is the calculated value of the flight time of the frame between the non-responding antenna and the tag node, is the calculated value of the distance between the non-responsive antenna and the tag node; according to the above formula (2), the distance from each non-responsive antenna to the node to be measured is calculated in turn, and the distance from each of the six antennas to the node to be measured is obtained.

3. The UWB-based three-dimensional positioning method for tunnel safety monitoring according to claim 2 is characterized in that: The anchor node accurately locates the coordinates of the node to be measured. Sent to the security monitoring system.

4. The UWB-based three-dimensional positioning method for tunnel safety monitoring according to claim 3 is characterized in that: Each antenna in the antenna array is equipped with the same chip, and all chips are clocked by the same crystal oscillator, and the distance from the crystal oscillator to each chip is equal.

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