Underground positioning method and system based on UWB

Abstract

The invention belongs to the technical field of positioning detection, and particularly relates to a UWB-based underground positioning method and system. The beacons broadcast and send UWB positioning signals according to the arrangement position sequence, and after the beacons receive the UWB positioning signals sent by the previous beacons, the beacons broadcast and send the UWB positioning signals of the beacons themselves; the beacons are arranged in an underground roadway covering a fully-mechanized face at intervals and located on the same side, and the position of each beacon is known; the positioning card receives UWB positioning signals sent by the beacons in a broadcast mode, the positioning card judges based on the received UWB positioning signals sent by the two adjacent beacons, and if the product of the time difference of the received two adjacent UWB positioning signals and the electromagnetic wave propagation speed of the UWB positioning signals is larger than 0 and smaller than twice the distance between the two adjacent beacons, the positioning card sends the UWB positioning signals to the positioning card. If not, the position of the positioning card is determined based on the time difference of the received two adjacent UWB positioning signals and the position of the beacon, so that high-precision and low-cost underground positioning is realized at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of positioning detection, and in particular relates to a UWB-based underground positioning method and system. Background Art

[0002] The advancement of automation and intelligent technology in fully mechanized mining faces, while improving production efficiency, also presents safety risks for fully mechanized mining face operators and production team members. Therefore, it is necessary to develop a comprehensive underground coal mine personnel positioning system with advanced technology, stable performance, and high positioning accuracy to accurately monitor the dynamic distribution of underground personnel and the number of personnel on the mining face. The primary function of underground positioning is to provide safe positioning of personnel, vehicles, and other equipment to meet production and manufacturing needs, so the number of connected users is also a factor to consider. As a consumer product, it still has the attributes of a commodity. While ensuring positioning accuracy, users must consider cost. Due to the hazardous conditions of underground mines and the lack of space for infrastructure deployment, low space costs are required, as well as minimal hardware and maintenance costs. Low resource costs will allow for the large-scale implementation of these systems, and low maintenance costs will ensure the continuous operation of the positioning system. Therefore, a high-precision and low-cost underground positioning method is urgently needed.

[0003] Currently, the commonly used methods for wireless positioning of underground personnel include Received Signal Strength Indication (RSSI), Time of Arrival (TOA), and Time Difference of Arrival (TDOA). Commonly used wireless technologies include Radio Frequency Identification (RFID), Bluetooth low energy (BLE), and ZigBee.

[0004] RSSI is the superposition of multipath signals with rapidly varying phases. RSSI decreases monotonically with distance. Theoretically, average path loss strictly adheres to this trend, and a log-normal distance path loss model is commonly used to calculate distance. However, underground mines, due to the underground environment and complex mechanical equipment, experience extensive multipath fading and temporal dynamics. Due to random shadowing, the underground multipath environment causes RSSI to fluctuate on the order of the signal wavelength. Slight variations in certain multipath components can lead to significant constructive or destructive phase shifts, ultimately resulting in significant RSSI fluctuations. Large deviations from multipath shadowing obscure the monotonic trend, ultimately resulting in lower RSSI positioning accuracy. Time-of-arrival (TOA) estimates the distance to a node by calculating the broadcast time of a radio signal. In line-of-sight conditions, at least three base stations are required to achieve high levels of positioning accuracy. TOA also requires strict time synchronization between positioning cards and base stations, and between base stations. Therefore, optimization methods are required for accurate positioning, which is costly. TDOA estimates distance by using the time difference between positioning cards in the same packet, eliminating the need for time synchronization between positioning cards and base stations. However, strict time synchronization between base stations is still required, and at least three base stations must be deployed. This places extremely high demands on system time synchronization and crystal oscillator stability, resulting in high positioning costs. Existing time synchronization methods, such as hierarchical or virtual time technologies, increase system complexity and hinder system design and implementation. Furthermore, deploying multiple base stations in confined environments such as mines is extremely difficult, posing significant challenges to the implementation of TOA and TDOA.

[0005] RFID uses radio waves to store and retrieve data. It consists of two main components: the RFID reader and the RFID tag. RFID readers use a predefined protocol to obtain information stored in RFID tags. Therefore, accuracy is limited by the distribution and density of readers and writers, making high-precision positioning impossible. RFID is also limited by its read and write speed in multi-concurrency mode, making it unable to handle multiple people simultaneously and prone to missed reads. RFID also has a short communication range and limited coverage. BLE, based on the IEEE 802.15 standard, uses less power and is less expensive than traditional Bluetooth. Its compact size and ease of deployment make it widely used for positioning. However, its power consumption limits BLE's coverage. Furthermore, BLE positioning relies heavily on RSSI input, which results in lower positioning accuracy. ZigBee is a short-range wireless communication technology based on the IEEE 802.15.4 standard. Currently, ZigBee technology in China offers a wider range than both BLE and RFID, sharing the advantages of BLE's low power consumption and low cost. However, its accuracy is limited to 2 meters. ZigBee mainly uses the 2.4G frequency in the ISM band. Due to the physical limitations of the frequency band, the signal interference is severe, the diffraction ability is weak, the wall penetration ability is weak, and the positioning accuracy is easily affected by environmental interference, resulting in unstable positioning performance. In actual environments, a wall or a door will greatly reduce the signal, and this phenomenon is particularly obvious in mines.

[0006] To improve RSSI positioning accuracy, Chinese patent application publication number CN104316902A discloses a downhole positioning method. Positioning readers are installed at regular intervals within an underground tunnel. A positioning card transmits wireless positioning request data at regular intervals. The nth and n+1th positioning readers closest to the positioning card read the RSSI values of the positioning request data and transmit these values to an uphole control center. The control center calculates the distance between the two positioning readers based on the two RSSI values and the signal propagation index, and determines the position of the positioning card based on the proportional relationship between the two distances. While this method improves positioning accuracy, it still relies on RSSI to infer distance, and due to interference from the downhole multipath environment, positioning accuracy remains fundamentally low. Summary of the Invention

[0007] The object of the present invention is to provide a UWB-based downhole positioning method and system for achieving both high-precision and low-cost downhole positioning.

[0008] In order to solve the above technical problems, the present invention provides an underground positioning method based on UWB, comprising: beacons broadcasting UWB positioning signals in the order of their layout positions, and when a beacon receives the UWB positioning signal sent by the previous beacon, it broadcasts its own UWB positioning signal; each beacon is arranged at intervals in an underground tunnel covering a fully mechanized mining surface and is on the same side, and the position of each beacon is known; a positioning card receives the UWB positioning signal broadcast by the beacon, and the positioning card makes a judgment based on the UWB positioning signals received from two adjacent beacons. If the product of the time difference of receiving the two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, the position of the positioning card is determined based on the time difference of receiving the two adjacent UWB positioning signals and the beacon position.

[0009] Furthermore, the intervals between adjacent beacons are the same.

[0010] Furthermore, the process of determining the position of the positioning card based on the time difference between the two adjacent UWB positioning signals and the beacon position is as follows: according to the relationship between the time difference between the two adjacent UWB positioning signals and the distance of the positioning card relative to the beacon, the distance of the positioning card relative to the beacon corresponding to the time difference between the two adjacent UWB positioning signals is determined, and then the position of the positioning card is determined according to the distance of the positioning card relative to the beacon and the corresponding beacon position; the relationship between the time difference between the two UWB positioning signals and the distance of the positioning card relative to the beacon is obtained according to experiments.

[0011] Furthermore, when the positioning card receives the UWB positioning signals sent by all beacons and the product of the time difference between two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, it means that the positioning card is not within the positioning range of all beacons.

[0012] Furthermore, the method further comprises: after determining the position of the positioning card, sending the position of the positioning card to the uphole general control system or the downhole hydraulic support control system via the base station.

[0013] The beneficial effects of the above-mentioned technical solution are as follows: This invention is a pioneering creation that leverages the high resolution, high transmission speed, and large bandwidth of UWB signals for positioning in complex environments. By broadcasting UWB signals in the order of beacons' placement and receiving them in a single reception by a positioning card, the time difference between the UWB positioning signals received from two adjacent beacons is calculated. The positioning card directly determines its own position based on the reception time difference, signal propagation speed, and beacon spacing. Compared to RSSI downhole positioning, this solution offers higher positioning accuracy, capable of achieving sub-meter positioning accuracy. Furthermore, compared to TODA and TOA systems that utilize multiple base stations as reference points for downhole positioning, this solution uses small, easy-to-install beacons instead of traditional base stations. Both the beacons and the positioning card can be implemented using commercial chips. While achieving high-precision positioning, this solution significantly reduces hardware costs and is applicable to more restricted environments, reducing space costs. In terms of maintenance costs, both the beacons and the positioning card operate with low power consumption, resulting in low maintenance costs.

[0014] In order to solve the above technical problems, the present invention also provides an underground positioning system based on UWB, including a positioning card and a beacon, wherein the beacons are arranged at intervals in the underground tunnel covering the comprehensive mining face and on the same side, and the position of each beacon is known; the beacon is provided with a UWB signal sending module for broadcasting and sending UWB positioning signals in the order of arrangement positions, and when the beacon receives the UWB positioning signal sent by the previous beacon, it broadcasts and sends its own UWB positioning signal; the positioning card includes a UWB signal receiving module and a calculation module, the UWB signal receiving module is used to receive the UWB positioning signal broadcast by the beacon, and the calculation module is used to make a judgment based on the UWB positioning signals sent by two adjacent beacons, if the product of the time difference of receiving the two adjacent UWB positioning signals and the electromagnetic wave propagation speed of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, then the position of the positioning card is determined based on the time difference of receiving the two adjacent UWB positioning signals and the beacon position.

[0015] Furthermore, the intervals between the beacons are the same.

[0016] Furthermore, the calculation module determines the position of the positioning card based on the time difference between the two adjacent UWB positioning signals and the beacon position. The process is as follows: according to the relationship between the time difference between the two adjacent UWB positioning signals and the distance of the positioning card relative to the beacon, the positioning card relative beacon distance corresponding to the time difference between the two adjacent UWB positioning signals is determined, and then the positioning card position is determined according to the positioning card relative beacon distance and the corresponding beacon position; the relationship between the time difference between the two UWB positioning signals and the distance of the positioning card relative to the beacon is obtained according to experiments.

[0017] Furthermore, when the positioning card receives the UWB positioning signals sent by all beacons and the product of the time difference between two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, it means that the positioning card is not within the positioning range of all beacons.

[0018] Furthermore, the system also includes a base station, which is used to send the position of the positioning card to the uphole general control system or the downhole hydraulic support control system.

[0019] The beneficial effects of the above-mentioned technical solution are as follows: This invention is a pioneering creation that leverages the high resolution, high transmission speed, and large bandwidth of UWB signals for positioning in complex environments. By broadcasting UWB signals in the order of beacons' placement and receiving them in a single reception by a positioning card, the time difference between the UWB positioning signals received from two adjacent beacons is calculated. The positioning card directly determines its own position based on the reception time difference, signal propagation speed, and beacon spacing. Compared to RSSI downhole positioning, this solution offers higher positioning accuracy, capable of achieving sub-meter positioning accuracy. Furthermore, compared to TODA and TOA systems that utilize multiple base stations as reference points for downhole positioning, this solution uses small, easy-to-install beacons instead of traditional base stations. Both the beacons and the positioning card can be implemented using commercial chips. While achieving high-precision positioning, this solution significantly reduces hardware costs and is applicable to more restricted environments, reducing space costs. In terms of maintenance costs, both the beacons and the positioning card operate with low power consumption, resulting in low maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the principle of a UWB-based downhole positioning system according to an embodiment of the present invention;

[0021] Figure 2 This is a flowchart of downhole positioning based on UWB in the embodiment of the system of the present invention;

[0022] Figure 3 This is a diagram showing the relationship between the time difference between two UWB positioning signals and the distance between the positioning card and the beacon in the system implementation mode of the present invention. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear, the specific embodiments of the present invention are further described below with reference to the accompanying drawings.

[0024] The present invention adopts UWB signals for communication, and uses the time difference of the broadcast UWB signals received by the positioning card and the beacon spacing to determine the position of the positioning card, thereby achieving high-precision and low-cost underground positioning.

[0025] System Implementation

[0026] The present invention provides a UWB-based underground positioning system for positioning underground personnel in coal mines, metal mines, and non-metal mines. Figure 1 As shown, the system includes beacons and positioning cards. The beacons are arranged at intervals in the underground tunnel covering the fully mechanized mining surface and are on the same side, and the position of each beacon is known. The height of the beacon is not necessarily the same as the height at which the positioning card is worn, and may not be at the same height. Preferably, in order to further improve the positioning accuracy, the height of the beacon is the same as the height at which the positioning card is worn. Since underground tunnels in coal mines, metal and non-metallic mines are generally long and narrow, and the distance between the beacon and the positioning card is much smaller than the set spacing between the beacons, the underground tunnel can be regarded as a one-dimensional linear space, and the positioning card and the beacon are on a straight line. In addition, when used, the present invention measures the distance of the positioning card relative to the beacon and the time difference of the corresponding two UWB positioning signals in advance at different beacon spacings, and uses software algorithms to perform corresponding calculation optimization, which can ensure the accuracy of the positioning data when the distance difference between the beacon and the positioning card is too large.

[0027] When hydraulic supports are deployed in underground tunnels, beacons are placed below or on one side of the hydraulic support device in the underground tunnel covering the fully mechanized mining face (based on the actual installation position) to confirm the relative distance between underground personnel and the hydraulic support, and avoid the hydraulic support moving when personnel are near the hydraulic support, causing personnel to be squeezed and injured, thereby achieving proximity protection for underground personnel.

[0028] The beacon includes a UWB signal transmission module for broadcasting a UWB positioning signal. This UWB positioning signal includes a beacon identifier, which can be used to determine the beacon's location. A positioning card is a personal positioning card worn by underground workers. This card stores personal work information and features a UWB signal reception module and a calculation module. The UWB signal reception module receives the UWB positioning signal transmitted by the beacon, while the calculation module determines the underground worker's own position based on the received UWB positioning signal.

[0029] Ultra Wide Band (UWB) is a precise carrier-free communication technology. UWB signals are signals with extremely short pulses, very wide frequency bands, and very low power spectral density. It directly modulates extremely short time pulses with steep rising and falling edges, so that the signal has a bandwidth of the order of GHz and sub-meter positioning accuracy. Such characteristics enable UWB signals to effectively pass through some physical obstacles and have strong penetration; high bandwidth enables UWB to have higher resolution and strong anti-multipath capabilities in restricted environments such as multipath, and high bandwidth also provides high data throughput for communication and supports multi-user access; UWB signals can complete transmission at the nanosecond level and have high time resolution, which enables UWB to support high-precision positioning, and the hardware structure is simple. Therefore, the present invention uses UWB signals to complete high-precision positioning in special environments such as factories and mines. This system is used to implement a UWB-based underground positioning method, and the specific process is as follows: Figure 2 As shown, the following steps are included:

[0030] 1. Broadcast and send UWB positioning signals in the order of deployment positions. When a beacon receives the UWB positioning signal sent by the previous beacon, it broadcasts its own UWB positioning signal.

[0031] According to the beacon layout position, the UWB positioning signal can be broadcast from the first beacon (starting beacon) in the underground tunnel. After receiving the UWB positioning signal broadcast by the first beacon, the second beacon broadcasts the UWB positioning signal of the second beacon, and a round of positioning is completed after the nth beacon broadcasts its own UWB positioning signal. n is the total number of beacons laid out in the underground tunnel covering the fully mechanized mining face.

[0032] The intervals between beacons may be different. As a preferred embodiment, the intervals between beacons are the same, that is, the beacons are arranged at equal intervals.

[0033] 2. The positioning card starts receiving, and the UWB signal receiving module receives the UWB positioning signal broadcast by the beacon. The positioning card makes a judgment based on the UWB positioning signals sent by two adjacent beacons. If the product of the time difference between the two adjacent UWB positioning signals and the electromagnetic wave propagation speed of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, the positioning card position is determined based on the time difference between the two adjacent UWB positioning signals and the beacon position.

[0034] The beacons are numbered in the order of deployment. The time when the positioning card receives the UWB positioning signals sent by two adjacent beacons is t i , t i+1 , i≤n-1; t i Indicates the time when the UWB positioning signal broadcast by the i-th beacon is received, t i+1The time when the UWB positioning signal broadcast by the i+1th beacon is received, and the time difference between the two UWB positioning signals received is Δt=t i+1 -t i Assume that the electromagnetic wave propagation speed of the UWB positioning signal is c, the beacon spacing is d, and determine c(t i+1 -t i ) and d, we can get three relationships:

[0035]

[0036] When c(t i+1 -t i )=2d, it means that the positioning card may be at the border of the i-th beacon (or on the side away from the i+1-th beacon with the i-th beacon as the center). The positioning card is at t i The UWB positioning signal broadcast by the i-th beacon is received. After a period of propagation, the UWB positioning signal is received by the i+1-th beacon. The propagation distance is d. Then the i+1-th beacon broadcasts the UWB positioning signal. After a period of propagation, it is received by the i+1-th beacon at t i+1 It is received by the positioning card at the boundary of the i-th beacon, and the propagation distance is also d.

[0037] When c(t i+1 -t i )=0, it means that the time difference between the two adjacent UWB positioning signals received is 0, and the positioning card may be at the boundary of the i+1th beacon (or on the side away from the i-th beacon with the i+1th beacon as the center). The positioning card and the i+1th beacon are at t i At the same time, the UWB positioning signal broadcast by the i-th beacon is received, and the i+1-th beacon immediately sends the UWB positioning signal time at this time, so that t i+1 =t i .

[0038] When 0<c(t i+1 -t i )<2d, it means that the positioning card is between the i-th beacon and the i+1-th beacon.

[0039] If it is determined that the product of the time difference between the two UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is 0 or equal to twice the distance between the two adjacent beacons, the UWB positioning signal sent by the beacon will continue to be received.

[0040] When the positioning card receives the UWB positioning signals sent by all beacons and the product of the time difference between two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, it means that the positioning card is not within the positioning range of all beacons.

[0041] The process of determining the position of the positioning card based on the time difference of receiving the two UWB positioning signals and the beacon position is as follows: the process of determining the position of the positioning card based on the time difference of receiving the two adjacent UWB positioning signals and the beacon position is as follows: according to the relationship between the time difference of the two UWB positioning signals and the distance of the positioning card relative to the beacon, the relative distance of the positioning card corresponding to the time difference of receiving the two adjacent UWB positioning signals is determined, and then the position of the positioning card is determined according to the relative distance of the positioning card to the beacon and the corresponding beacon position; the relationship between the time difference of the two UWB positioning signals and the distance of the positioning card relative to the beacon is obtained according to experiments.

[0042] After experimental verification, it was found that only when 0<c(t i+1 -t i )<2d, that is, when the positioning card is between two adjacent beacons, the position of the positioning card can be accurately calculated according to the time difference Δt of the two received UWB positioning signals. Figure 3 This is the relationship between Δt and the distance of the positioning card relative to the beacon when the beacon spacing is 20m. -10 represents the position of the i-th beacon, 10 represents the position of the i+1-th beacon, (-10, 10) represents that the positioning card is between two beacons, [-20, -10] represents that the positioning card is at the boundary or left of the i-th beacon, and [10, 20] represents that the positioning card is at the boundary or right of the i+1-th beacon. It can be seen that only when the positioning card is at (-10, 10), Δt and the distance of the positioning card relative to the beacon are linearly related. The distance of the positioning card relative to the beacon can be determined based on Δt, and then the position of the positioning card, that is, the location information of the underground personnel, can be determined based on the distance of the positioning card relative to the beacon and the corresponding beacon position.

[0043] The positioning card also features a signal transmission module, which, after determining its location, transmits it to a remote base station or underground hydraulic support control system. The base station receives the location information of underground personnel at the fully-mechanized mining face and uploads it to the surface control system. This system shares the positioning card's location, enabling real-time monitoring and protection of underground personnel at the fully-mechanized mining face. In a preferred embodiment, the wireless signal transmission module is a LoRa module.

[0044] Method implementation

[0045] A UWB-based downhole positioning method of the present invention comprises the following steps:

[0046] S1: Beacons broadcast UWB positioning signals in the order of their placement. When a beacon receives the UWB positioning signal sent by the previous beacon, it broadcasts its own UWB positioning signal. Each beacon is placed at intervals in the underground tunnel covering the fully mechanized mining face and on the same side. The position of each beacon is known.

[0047] The spacing between the beacons can vary. As a preferred embodiment, the spacing between the beacons is the same, that is, the beacons are arranged at equal intervals. The beacon height is not necessarily the same as the height at which the positioning card is worn, and may not be at the same height. Preferably, to further improve positioning accuracy, the beacon height is the same as the height at which the positioning card is worn.

[0048] S2: The positioning card receives the UWB positioning signal broadcast by the beacon. The positioning card makes a judgment based on the UWB positioning signals sent by two adjacent beacons. If the product of the time difference of receiving the two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, the positioning card position is determined based on the time difference of receiving the two adjacent UWB positioning signals and the beacon position.

[0049] The time when the positioning card receives two adjacent UWB positioning signals is t i , t i+1 , i≤n-1; t i Indicates the time when the UWB positioning signal broadcast by the i-th beacon is received, t i+1 It represents the time when the UWB positioning signal broadcast by the i+1th beacon is received, and the time difference between two adjacent UWB positioning signals received is Δt=t i+1 -t i Assume that the electromagnetic wave propagation speed of the UWB positioning signal is c, the beacon spacing is d, and determine c(t i+1 -t i ) and d, we can get three relationships:

[0050]

[0051] When 0<c(t i+1 -t i ) < 2d, it indicates that the positioning card is between the i-th beacon and the (i+1)-th beacon. At this time, based on the relationship between the time difference between the two UWB positioning signals and the distance of the positioning card relative to the beacon, the positioning card's relative distance to the beacon corresponding to the time difference in receiving the two adjacent UWB positioning signals is determined. Then, the positioning card's position is determined based on the distance of the positioning card relative to the beacon and the corresponding beacon position. The relationship between the time difference between the two UWB positioning signals and the distance of the positioning card relative to the beacon is obtained through experiments. If it is determined that the product of the time difference in receiving the two UWB positioning signals and the propagation speed of the UWB positioning signal electromagnetic wave is 0 or equal to twice the distance between the two adjacent beacons, then continue to receive UWB positioning signals sent by the beacon.

[0052] When the positioning card receives the UWB positioning signals sent by all beacons and the product of the time difference between two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, it means that the positioning card is not within the positioning range of all beacons.

[0053] S3: After the position of the positioning card is determined, the position of the positioning card is sent to the uphole general control system or the downhole hydraulic support control system through the base station.

[0054] There are two base stations, one at each end of the fully mechanized mining face.

[0055] This invention cleverly utilizes the concept of TDOA, leveraging the high resolution, high transmission speed, and wide bandwidth of UWB signals in complex environments within UWB coverage. The system calculates the time difference between the sequential broadcast of UWB signals by beacons and the single reception of UWB signals by positioning cards. The positioning card then directly determines its own position based on the time difference, signal propagation speed, and beacon spacing. Compared to RSSI-based downhole positioning, this system offers higher positioning accuracy, achieving sub-meter accuracy. Furthermore, compared to TODA and TOA systems that utilize multiple base stations as reference points for downhole positioning, this system uses small, easy-to-install beacons instead of traditional base station deployments. Both the beacons and positioning cards can be implemented using commercial chips. While achieving high-precision positioning, this system significantly reduces hardware costs, making it applicable to more restricted environments and reducing space costs. Furthermore, the low power consumption of both the beacon and positioning card ensures low maintenance costs. The intrinsically safe design ensures the system maintains high robustness and long-term stable operation. The system achieves positioning through a single positioning signal broadcast. Leveraging the long-range coverage of LoRa communication, it enables the transmission and sharing of positioning information over long distances (5-15 km) with low power consumption. The underground positioning system operates with extremely low power consumption, ensuring long-term battery-powered operation. Regarding access personnel, since broadcast positioning eliminates the need for responses and interactions, an unlimited number of users can access the system during the positioning period, eliminating contention issues caused by positioning communications. The final number of access users is determined by communication between the remote base station and the positioning card, avoiding limitations on access due to positioning. The system also operates independently and is easily embedded in various underground positioning systems.

Claims

1. A downhole positioning method based on UWB, characterized in that: include: Beacons broadcast UWB positioning signals in the order of their placement. When a beacon receives a UWB positioning signal from the previous beacon, it broadcasts its own UWB positioning signal. Each beacon is placed at intervals in the underground tunnel covering the fully mechanized mining face and on the same side. The position of each beacon is known. The positioning card receives the UWB positioning signal broadcast by the beacon. The positioning card makes a judgment based on the UWB positioning signals sent by two adjacent beacons. If the product of the time difference between the two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, the positioning card position is determined based on the time difference between the two adjacent UWB positioning signals and the beacon position.

2. The UWB-based downhole positioning method according to claim 1, characterized in that: The intervals between adjacent beacons are the same.

3. The UWB-based downhole positioning method according to claim 1 or 2, characterized in that: The process of determining the position of the positioning card based on the time difference between the two adjacent UWB positioning signals and the beacon position is as follows: according to the relationship between the time difference between the two adjacent UWB positioning signals and the distance of the positioning card relative to the beacon, the relative distance of the positioning card corresponding to the time difference between the two adjacent UWB positioning signals is determined, and then the position of the positioning card is determined according to the relative distance of the positioning card to the beacon and the corresponding beacon position; the relationship between the time difference between the two UWB positioning signals and the distance of the positioning card relative to the beacon is obtained based on experiments.

4. The UWB-based downhole positioning method according to claim 1, characterized in that: When the positioning card receives the UWB positioning signals sent by all beacons and the product of the time difference between two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, it means that the positioning card is not within the positioning range of all beacons.

5. The UWB-based downhole positioning method according to claim 1, characterized in that: The method further comprises: after determining the position of the positioning card, sending the position of the positioning card to an uphole general control system or an underground hydraulic support control system via a base station.

6. A UWB-based downhole positioning system, including a positioning card, characterized in that: It also includes beacons, which are arranged at intervals in the underground tunnel covering the fully mechanized mining surface and on the same side, and the position of each beacon is known; the beacon is provided with a UWB signal sending module, which is used to broadcast and send UWB positioning signals in the order of the arrangement positions. When the beacon receives the UWB positioning signal sent by the previous beacon, it broadcasts and sends its own UWB positioning signal; the positioning card includes a UWB signal receiving module and a calculation module. The UWB signal receiving module is used to receive the UWB positioning signal broadcast by the beacon, and the calculation module is used to make a judgment based on the UWB positioning signals sent by two adjacent beacons. If the product of the time difference of receiving two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, the position of the positioning card is determined based on the time difference of receiving the two adjacent UWB positioning signals and the beacon position.

7. The UWB-based downhole positioning system according to claim 6, characterized in that: The intervals between each beacon are the same.

8. The UWB-based downhole positioning system according to claim 6 or 7, characterized in that: The calculation module determines the position of the positioning card based on the time difference of receiving the two adjacent UWB positioning signals and the beacon position. The process is as follows: according to the relationship between the time difference of the two adjacent UWB positioning signals and the distance of the positioning card relative to the beacon, the positioning card relative beacon distance corresponding to the time difference of receiving the two adjacent UWB positioning signals is determined, and then the positioning card position is determined according to the positioning card relative beacon distance and the corresponding beacon position; the relationship between the time difference of the two UWB positioning signals and the distance of the positioning card relative beacon is obtained based on experiments.

9. The UWB-based downhole positioning system according to claim 6, characterized in that: When the positioning card receives the UWB positioning signals sent by all beacons and the product of the time difference between two adjacent UWB positioning signals and the propagation speed of the electromagnetic wave of the UWB positioning signal is greater than 0 and less than twice the distance between the two adjacent beacons, it means that the positioning card is not within the positioning range of all beacons.

10. The UWB-based downhole positioning system according to claim 6, characterized in that: The system also includes a base station, which is used to send the position of the positioning card to the uphole general control system or the downhole hydraulic support control system.

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