A monorail crane vehicle high-precision positioning and position calibration system

Abstract

The application discloses a monorail crane vehicle high-precision positioning and position calibration system and belongs to the technical field of mine intelligent transportation. The system adopts a reverse base station deployment mode: the vehicle base station is arranged at the head / tail of the monorail crane vehicle and is connected to the existing Wi-Fi 6 network of the vehicle, and the positioning base station is arranged near / above the track and only needs power supply and no communication and network connection between each other. The system further comprises a calibration base station modified from the positioning base station, the passive trigger module of the calibration base station is triggered through the active trigger arm on the vehicle, and the pre-allocated absolute physical position calibration encoder is used to accumulate the error; a plurality of groups of equidistant calibration base stations are used to realize accurate parking; and the anti-collision base station arranged at the tail / head of the vehicle is used to realize the cascade positioning and anti-collision early warning of the vehicles on the same track. The application has low deployment difficulty, low cost and flexible on-demand deployment, the positioning precision can reach the centimeter level, and is suitable for the full-scene positioning and safety management and control of the monorail crane vehicle in a coal mine.

Description

Technical Field

[0001] This invention relates to the field of intelligent transportation technology in mines, specifically to a high-precision positioning and position calibration system for a monorail crane. Background Technology

[0002] Monorail locomotives are crucial auxiliary transportation equipment in underground coal mines, widely used for transporting personnel, materials, and equipment. With the advancement of intelligent coal mine construction, the unmanned driving and intelligent scheduling of monorail locomotives place increasingly higher demands on their positioning accuracy.

[0003] While existing personnel positioning networks in the mining sector can be attempted for positioning monorail cranes, they suffer from the following prominent issues: (1) Difficult network line deployment: Traditional positioning systems must use network communication lines (such as RS485, fiber optic, LoRa) to connect various positioning base stations. The underground working space is limited, and the wiring construction needs to be coordinated with the mine production plan. The construction window is limited, the deployment cycle is long and the cost is high.

[0004] (2) Poor expansion flexibility: Once the network is built, adding a new base station means rewiring or adding relay equipment, which is difficult to implement and cannot flexibly adjust the location of the base station according to changes in production layout.

[0005] (3) Low fault tolerance: Traditional positioning systems use chain or bus network structures. A single base station failure may cause all downstream nodes to be paralyzed. Troubleshooting requires network investigation, and there are cable faults that make it difficult to locate quickly.

[0006] (4) High maintenance costs: Complex network lines require high technical skills from maintenance personnel, cables are at risk of damage, maintenance work affects production, and the later maintenance costs are huge.

[0007] (5) Insufficient positioning accuracy: Traditional positioning methods mostly use RSSI signal strength ranging or simple TOF ranging, which are greatly affected by underground multipath effect and non-line-of-sight propagation. The positioning accuracy is usually in the meter range, which cannot meet the centimeter-level accuracy requirements of precise positioning and parking and collision warning of monorail cranes.

[0008] (6) Lack of position calibration mechanism: Monorail cranes are usually equipped with encoders for odometer positioning, but long-term operation will generate cumulative errors. The existing system lacks effective external reference calibration means, which leads to the accumulation of positioning errors as the running distance increases.

[0009] In recent years, UWB (Ultra-Wideband) technology has achieved centimeter-level positioning accuracy in indoor positioning due to its nanosecond-level pulse signals and high temporal resolution. DS-TWR (Dual-Sided Two-Way Ranging) algorithm is a commonly used ranging method in UWB positioning; however, traditional DS-TWR algorithms typically employ a three-way handshake and require time synchronization or network connectivity between positioning base stations, making them unsuitable for deployment scenarios underground without dedicated network support. Therefore, there is an urgent need for a monorail crane positioning system that is simple to deploy, low-cost, highly accurate, and possesses position calibration capabilities. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-precision positioning and position calibration system for monorail cranes. This system solves the problems of traditional positioning systems, such as difficult deployment, high cost, inflexible expansion, insufficient positioning accuracy, and lack of position calibration. It enables centimeter-level high-precision positioning of monorail cranes, encoder cumulative error calibration, precise point-to-point parking, and collision avoidance for monorail cranes.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a high-precision positioning and position calibration system for a monorail crane locomotive, comprising a locomotive base station, several positioning base stations, and a host computer; The locomotive base station is deployed at the head or tail of the monorail locomotive and connects to the existing Wi-Fi 6 network of the monorail locomotive via an RJ45 interface. It communicates with the host computer or dispatch center through the existing network of the locomotive. The positioning base stations are deployed near or on the monorail locomotive track. Each positioning base station does not need to communicate with each other or connect to a network, and only needs to be powered. The directional antennas of the positioning base stations are installed opposite to the directional antennas of the locomotive base stations, so that the locomotive base stations and positioning base stations are always within line of sight during locomotive operation. The locomotive base station and the positioning base station obtain timestamps through four-way handshake message exchange based on UWB technology, and calculate the distance between the locomotive base station and the positioning base station according to the improved DS-TWR bilateral bidirectional ranging algorithm. The locomotive base station uploads distance information to the host computer via the locomotive's existing network. The host computer uses the TDOA algorithm to determine the location coordinates of the monorail locomotive and displays them on the vector map. The system also includes a calibration base station, which is modified from a positioning base station and equipped with a passive triggering module. An active triggering arm is installed on the monorail locomotive. When the active triggering arm triggers the passive triggering module, the calibration base station sends the equipment number to the locomotive base station. The host computer calibrates the cumulative error of the locomotive encoder according to the pre-assigned absolute physical position.

[0012] Preferably, the four-way handshake message exchange between the locomotive base station and the positioning base station includes: First handshake: The locomotive base station broadcasts a POLL message and records the sending timestamp t1; Second handshake: The positioning base station receives the POLL message and records the receiving timestamp t2, and after a delay, returns the RESP message and records the sending timestamp t3; The third handshake: The locomotive base station receives the RESP message and records the reception timestamp t4, then sends the FINAL message after a delay and records the sending timestamp t5; Fourth handshake: The positioning base station receives the FINAL message and records the receiving timestamp t6, and returns the LAST message, which carries the timestamps t2, t3, and t6 recorded by the positioning base station. After receiving the LAST message, the locomotive base station calculates the flight time and distance using the following formula; Preferably, the distance calculation formula of the improved DS-TWR bilateral two-way ranging algorithm is as follows: Tof_dtu=[((t4 t1)×(t6 t3)) ((t5 t4)×(t3 t2))] / (t6+t5 t1 t2) Tof = Tof_dtu × (1 / 499.2e6 / 128) distance = Tof × c Where t1 is the timestamp of the locomotive base station sending the POLL message, t2 is the timestamp of the positioning base station receiving the POLL message, t3 is the timestamp of the positioning base station sending the RESP message, t4 is the timestamp of the locomotive base station receiving the RESP message, t5 is the timestamp of the locomotive base station sending the FINAL message, t6 is the timestamp of the positioning base station receiving the FINAL message, 1 / 499.2e6 / 128 is a time constant approximately equal to 15.65 ps, c is the speed of light 299702547 m / s, and distance is in centimeters.

[0013] Preferably, the system supports three modes: linear positioning, planar positioning, and spatial positioning. In linear positioning mode, the locomotive base station only performs four handshake distance measurements with a single positioning base station encountered during operation, and determines the linear position of the locomotive on the track based on the distance and track topology. In planar positioning mode, the locomotive base station needs to complete four handshake ranging with at least three positioning base stations simultaneously, and upload the three distance information to the host computer. The host computer uses the TDOA algorithm to calculate the locomotive's planar coordinates. In spatial positioning mode, the locomotive base station needs to complete four handshake distance measurements with at least four positioning base stations simultaneously, and upload the four distance information to the host computer. The host computer uses the TDOA algorithm to calculate the locomotive's spatial coordinates. In planar and spatial positioning, after receiving the POLL message, each positioning base station sends RESP messages in a time-sharing manner according to its own preset different delay time. The locomotive base station cyclically receives the RESP messages and LAST messages from each positioning base station until the required number of positioning base station data is collected or the timeout occurs and the system exits.

[0014] Preferably, the passive triggering module of the calibration base station is a mechanical triggering switch or an infrared sensing triggering module, and the active triggering arm is installed on the side or top of the monorail locomotive. Its extension length and angle are adjusted according to the installation position of the calibration base station. Each calibration base station has a unique absolute physical position coordinate pre-assigned in the host computer. When the locomotive passes the calibration base station and the active triggering arm triggers the passive triggering module, the locomotive base station receives the equipment number of the calibration base station and uploads it to the host computer. The host computer uses the absolute physical position as the reference value of the current position of the locomotive and clears or corrects the position error accumulated by the locomotive encoder.

[0015] Preferably, in the specific area where the monorail locomotive needs to stop at a fixed point, multiple sets of equally spaced calibration base stations are deployed along the track direction, with the spacing between adjacent calibration base stations being a preset fixed value d. When the locomotive triggers each calibration base station in sequence, the host computer calculates the actual travel speed of the locomotive v=d / Δt based on the time interval Δt between two adjacent triggers and the spacing d. Combining this with the locomotive braking distance model and the target position for stopping at a fixed point, the host computer sends deceleration and braking commands to the locomotive control system to achieve precise stopping at a fixed point. The absolute physical position of each set of calibration base stations is used to calibrate the locomotive position in real time, eliminating the influence of encoder cumulative error on the accuracy of stopping at a fixed point.

[0016] Preferably, an anti-collision base station is deployed at the rear or front of the monorail crane vehicle, and the anti-collision base station is composed of a positioning base station; When two locomotives traveling on the same track approach each other, the locomotive base station of the locomotive in front measures the distance with the positioning base station on the track, and the locomotive base station of the following locomotive measures the distance with the anti-collision base station of the locomotive in front. The locomotive base station prioritizes processing the distance information of the anti-collision base station. The host computer calculates the actual position of the following vehicle based on the distance between the preceding vehicle and the positioning base station, the length of the locomotive itself, and the distance between the following vehicle and the anti-collision base station, thus realizing the cascade positioning of locomotives on the same track. When the distance between the two vehicles is less than the safety threshold, the system issues an anti-collision warning signal and triggers emergency braking.

[0017] Preferably, the positioning base station includes two types: active positioning base station and passive positioning base station. Active positioning base stations are powered by AC power and are suitable for areas near the track where there is a power supply; passive positioning base stations are powered by their own built-in batteries and are suitable for areas where there is no power supply, with a battery life of no less than 6 months. The positioning base station is installed using a bracket fixing method, and the installation position can be adjusted at any time according to changes in the production layout, without the need for large-scale construction in conjunction with the mine's production plan.

[0018] Preferably, the specific process by which the host computer uses the TDOA algorithm to calculate the vehicle's position coordinates is as follows: The host computer receives distance information from multiple positioning base stations uploaded by the locomotive base station. It constructs multiple spherical equations with the known coordinates of each positioning base station as the center and the corresponding distance measurement value as the radius. The three-dimensional coordinates of the locomotive base station are then solved using the least squares method. For linear positioning scenarios, the host computer maps the ranging results to the mileage coordinates of the track centerline based on the track topology data. The host computer overlays the locomotive's real-time location onto the tunnel vector map, supporting functions such as location history trajectory playback, overspeed alarm, and boundary crossing alarm.

[0019] Preferably, the system has a single point of failure tolerance mechanism: Each positioning base station operates independently. When a single positioning base station fails, it does not affect the normal operation of other positioning base stations. The system automatically skips the failed base station and uses the data from the remaining normal base stations for positioning calculation. When any one of the four handshakes between the locomotive base station and the positioning base station fails, the locomotive base station re-initiates the ranging process. If the ranging fails three times in a row, the positioning base station is marked as faulty and reported to the host computer. Replacing a fault location base station does not require checking the network lines; it only requires checking the power supply and replacing the equipment. Ordinary electricians can complete the maintenance operation.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. Simple deployment and low cost: The reverse base station deployment method is adopted. The positioning base station only needs power supply and does not need network, avoiding the construction of underground dedicated network cabling. The deployment cost is reduced by more than 60%, and it can be quickly deployed during production breaks.

[0021] 2. Flexible expansion: The positioning base station works independently and its location can be added, removed, or adjusted at any time according to changes in the production layout, without the need for large-scale engineering modifications to match the production plan.

[0022] 3. High positioning accuracy: Based on UWB technology and the improved DS-TWR four-way handshake ranging algorithm, the positioning accuracy can reach the centimeter level, meeting the requirements of precise positioning and parking and collision avoidance warning for monorail cranes.

[0023] 4. Possesses position calibration capability: Provides an absolute physical position reference through a passively triggered calibration base station, and calibrates the cumulative error of the encoder in real time to ensure positioning accuracy during long-term operation.

[0024] 5. Complete functions: It integrates linear positioning, planar positioning, spatial positioning, position calibration, fixed-point parking and same-track collision avoidance, covering the positioning and safety management needs of monorail cranes in all scenarios.

[0025] 6. Easy maintenance: Single point of failure does not affect system operation, and troubleshooting does not require checking network lines. Ordinary electricians can replace positioning base stations, which greatly reduces maintenance costs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall execution flow of the system of the present invention.

[0027] Figure 2 This is a schematic diagram of the installation and deployment of the positioning base station of the present invention.

[0028] Figure 3 This is a timing diagram of the linear positioning message interaction of the present invention.

[0029] Figure 4 This is a sequence diagram of spatial positioning message interaction in this invention.

[0030] Figure 5 This is a schematic diagram of the calibration base station structure based on the modification of a positioning base station according to the present invention.

[0031] Figure 6 This is a schematic diagram of the installation and deployment of the calibration base station for this invention.

[0032] Figure 7 This is a schematic diagram of the installation and deployment of the fixed-point parking base station of the present invention.

[0033] Figure 8 This is a schematic diagram of the installation and deployment of the anti-collision base station and locomotive base station of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] Please see Figures 1 to 8 A high-precision positioning and position calibration system for a monorail crane locomotive includes a locomotive base station, several positioning base stations, and a host computer. The locomotive base station is deployed at the head or tail of the monorail locomotive and connects to the existing Wi-Fi 6 network of the monorail locomotive via the RJ45 interface. It communicates with the host computer or dispatch center through the existing network of the locomotive. The positioning base stations are deployed near or on the monorail locomotive track. The positioning base stations do not need to communicate with each other or connect to a network, and only need to be powered. The directional antennas of the positioning base stations are installed opposite to the directional antennas of the locomotive base stations, so that the locomotive base stations and the positioning base stations are always within line of sight during locomotive operation. The locomotive base station and the positioning base station obtain timestamps through four-way handshake message exchange based on UWB technology, and calculate the distance between the locomotive base station and the positioning base station according to the improved DS-TWR bilateral bidirectional ranging algorithm. The locomotive base station uploads distance information to the host computer via the locomotive's existing network. The host computer uses the TDOA algorithm to determine the location coordinates of the monorail locomotive and displays them on the vector map. The system also includes a calibration base station, which is modified from a positioning base station and equipped with a passive triggering module. An active triggering arm is installed on the monorail locomotive. When the active triggering arm triggers the passive triggering module, the calibration base station sends the equipment number to the locomotive base station. The host computer calibrates the cumulative error of the locomotive encoder according to the pre-assigned absolute physical position.

[0036] The four-way handshake message exchange between the locomotive base station and the positioning base station includes: First handshake: The locomotive base station broadcasts a POLL message and records the sending timestamp t1; Second handshake: The positioning base station receives the POLL message and records the receiving timestamp t2, and after a delay, returns the RESP message and records the sending timestamp t3; The third handshake: The locomotive base station receives the RESP message and records the reception timestamp t4, then sends the FINAL message after a delay and records the sending timestamp t5; Fourth handshake: The positioning base station receives the FINAL message and records the receiving timestamp t6, and returns the LAST message, which carries the timestamps t2, t3, and t6 recorded by the positioning base station. After receiving the LAST message, the locomotive base station calculates the flight time and distance using the following formula: The distance calculation formula for the improved DS-TWR two-way bidirectional ranging algorithm is as follows: Tof_dtu=[((t4 t1)×(t6 t3)) ((t5 t4)×(t3 t2))] / (t6+t5 t1 t2) Tof = Tof_dtu × (1 / 499.2e6 / 128) distance = Tof × c Where t1 is the timestamp of the locomotive base station sending the POLL message, t2 is the timestamp of the positioning base station receiving the POLL message, t3 is the timestamp of the positioning base station sending the RESP message, t4 is the timestamp of the locomotive base station receiving the RESP message, t5 is the timestamp of the locomotive base station sending the FINAL message, t6 is the timestamp of the positioning base station receiving the FINAL message, 1 / 499.2e6 / 128 is a time constant approximately equal to 15.65 ps, c is the speed of light 299702547 m / s, and distance is in centimeters.

[0037] The system supports three modes: linear positioning, planar positioning, and spatial positioning. In linear positioning mode, the locomotive base station only performs four handshake distance measurements with a single positioning base station encountered during operation, and determines the linear position of the locomotive on the track based on the distance and track topology. In planar positioning mode, the locomotive base station needs to complete four handshake ranging with at least three positioning base stations simultaneously, and upload the three distance information to the host computer. The host computer uses the TDOA algorithm to calculate the locomotive's planar coordinates. In spatial positioning mode, the locomotive base station needs to complete four handshake distance measurements with at least four positioning base stations simultaneously, and upload the four distance information to the host computer. The host computer uses the TDOA algorithm to calculate the locomotive's spatial coordinates. In planar and spatial positioning, after receiving the POLL message, each positioning base station sends RESP messages in a time-sharing manner according to its own preset different delay time. The locomotive base station cyclically receives the RESP messages and LAST messages from each positioning base station until the required number of positioning base station data is collected or the timeout occurs and the system exits.

[0038] The passive triggering module of the calibration base station is a mechanical triggering switch or an infrared sensing triggering module. The active triggering arm is installed on the side or top of the monorail locomotive, and its extension length and angle are adjusted according to the installation position of the calibration base station. Each calibration base station has a unique absolute physical position coordinate pre-assigned by the host computer. When the locomotive passes the calibration base station and the active triggering arm triggers the passive triggering module, the locomotive base station receives the equipment number of the calibration base station and uploads it to the host computer. The host computer uses this absolute physical position as the reference value of the locomotive's current position and clears or corrects the position error accumulated by the locomotive encoder.

[0039] In a specific area where a monorail locomotive needs to stop at a fixed point, multiple sets of equally spaced calibration base stations are deployed along the track direction, with the spacing between adjacent calibration base stations being a preset fixed value d. When the locomotive triggers each calibration base station in sequence, the host computer calculates the actual travel speed of the locomotive v=d / Δt based on the time interval Δt between two adjacent triggers and the spacing d. Combining this with the locomotive braking distance model and the target position for stopping at the fixed point, the host computer sends deceleration and braking commands to the locomotive control system to achieve precise stopping at the fixed point. The absolute physical position of each set of calibration base stations is used to calibrate the locomotive position in real time, eliminating the influence of the cumulative encoder error on the accuracy of stopping at the fixed point.

[0040] A collision avoidance base station is deployed at the rear or front of the monorail crane vehicle. The collision avoidance base station consists of a positioning base station. When two locomotives traveling on the same track approach each other, the locomotive base station of the locomotive in front measures the distance with the positioning base station on the track, and the locomotive base station of the following locomotive measures the distance with the anti-collision base station of the locomotive in front. The locomotive base station prioritizes processing the distance information of the anti-collision base station. The host computer calculates the actual position of the following vehicle based on the distance between the preceding vehicle and the positioning base station, the length of the locomotive itself, and the distance between the following vehicle and the anti-collision base station, thus realizing the cascade positioning of locomotives on the same track. When the distance between the two vehicles is less than the safety threshold, the system issues an anti-collision warning signal and triggers emergency braking.

[0041] Positioning base stations include two types: active positioning base stations and passive positioning base stations. Active positioning base stations are powered by AC power and are suitable for areas near the track where there is a power supply; passive positioning base stations are powered by their own built-in batteries and are suitable for areas where there is no power supply, with a battery life of no less than 6 months. The positioning base station is installed using a bracket fixing method, and the installation position can be adjusted at any time according to changes in the production layout, without the need for large-scale construction in conjunction with the mine's production plan.

[0042] The specific process by which the host computer uses the TDOA algorithm to calculate the vehicle's position coordinates is as follows: The host computer receives distance information from multiple positioning base stations uploaded by the locomotive base station. It constructs multiple spherical equations with the known coordinates of each positioning base station as the center and the corresponding distance measurement value as the radius. The three-dimensional coordinates of the locomotive base station are then solved using the least squares method. For linear positioning scenarios, the host computer maps the ranging results to the mileage coordinates of the track centerline based on the track topology data. The host computer overlays the locomotive's real-time location onto the tunnel vector map, supporting functions such as location history trajectory playback, overspeed alarm, and boundary crossing alarm.

[0043] The system has a single point of failure tolerance mechanism: Each positioning base station operates independently. When a single positioning base station fails, it does not affect the normal operation of other positioning base stations. The system automatically skips the failed base station and uses the data from the remaining normal base stations for positioning calculation. When any one of the four handshakes between the locomotive base station and the positioning base station fails, the locomotive base station re-initiates the ranging process. If the ranging fails three times in a row, the positioning base station is marked as faulty and reported to the host computer. Replacing a fault location base station does not require checking the network lines; it only requires checking the power supply and replacing the equipment. Ordinary electricians can complete the maintenance operation.

[0044] Example 1: Linear positioning and position calibration of a monorail crane in an underground coal mine This embodiment uses the linear positioning of a monorail crane in an underground auxiliary transport roadway of a coal mine as an example to illustrate the specific implementation process of the present invention. The roadway is 2800 meters long, with monorail tracks laid, and two monorail cranes are in operation, mainly responsible for the transportation of materials and equipment.

[0045] (1) System deployment: One base station is installed at the head of the monorail locomotive. The base station connects to the locomotive's existing Wi-Fi 6 network module via an RJ45 cable, with its directional antenna facing forward. Fourteen positioning base stations are deployed along the track, one every 200 meters. These stations are fixed to the track above the sidewall of the tunnel using brackets, with their directional antennas facing the track (opposite to the locomotive base station antenna). The positioning base stations are actively powered, drawing power from the existing lighting supply in the tunnel. No communication lines are connected between the positioning base stations; they only require a power supply to operate.

[0046] One calibration base station is deployed at each of the five key locations in the tunnel (tunnel entrance, junction, loading point, unloading point, and tunnel end). The calibration base stations are modified from positioning base stations, with a mechanically triggered passive trigger module added to the original positioning base station. An active trigger arm is installed on the left side of the monorail crane. The active trigger arm uses a spring-reset structure and extends 300mm. When the crane passes the calibration base station, the active trigger arm makes physical contact with the passive trigger module on the calibration base station and triggers the connection.

[0047] (2) Linear positioning and ranging process: When the monorail crane is running in the tunnel, the locomotive's base station continuously broadcasts UWB signals. When the locomotive enters the communication range of a positioning base station, the locomotive's base station and the positioning base station complete a four-way handshake ranging: First handshake: The locomotive base station broadcasts a POLL message and records the sending timestamp t1=1256000 clock cycles.

[0048] Second handshake: The positioning base station receives the POLL message, records the receiving timestamp t2=1258320 clock cycles, and returns the RESP message after a 2ms delay, recording the sending timestamp t3=1268320 clock cycles.

[0049] The third handshake: The locomotive base station receives the RESP message, records the reception timestamp t4 = 1270650 clock cycles, and sends the FINAL message after a 1ms delay, recording the sending timestamp t5 = 1275650 clock cycles.

[0050] Fourth handshake: The positioning base station receives the FINAL message, records the received timestamp t6=1277970 clock cycles, and then returns the LAST message, which carries three timestamps t2=1258320, t3=1268320, and t6=1277970.

[0051] After receiving the LAST message, the locomotive base station substitutes the values ​​into the formula for calculation: Tof_dtu=[((1270650 1256000)×(1277970 1268320)) ((1275650 1270650)×(1268320 1258320))] / (1277970+1275650 1256000 1258320)=[14650×9650 [5000×10000] / 39300=(141372500) 50000000) / 39300=91372500 / 39300≈2325.0 Tof=2325.0×15.65ps≈36386ps≈3.6386×10 -8 s distance = 3.6386 × 10 -8 s×299702547m / s≈10.91m That is, the distance between the locomotive base station and the positioning base station is approximately 10.91 meters. The locomotive base station uploads this distance information to the host computer via the locomotive's Wi-Fi 6 network. The host computer maps the distance to the mileage coordinates of the track centerline based on the known coordinates of the positioning base station and the track topology data, thus determining the linear position of the locomotive in the tunnel.

[0052] (3) Position calibration process: Monorail cranes are equipped with wheel encoders, which calculate the mileage of the crane based on the number of wheel rotations. Due to factors such as wheel slippage and wear, the encoders accumulate errors over long periods of operation, and the error can reach several meters after several kilometers of continuous operation.

[0053] When the locomotive reaches the calibration base station, the active triggering arm on the locomotive makes physical contact with the passive triggering module of the calibration base station. Upon activation of the passive triggering module, the calibration base station immediately sends a UWB message containing its own device number to the locomotive base station. The locomotive base station receives this message and uploads it to the host computer via the Wi-Fi 6 network. The host computer pre-stores the absolute physical location (track mileage coordinates) corresponding to each calibration base station device number; for example, the absolute mileage of the loading point calibration base station is K1+250.000m. When the host computer receives the message that the calibration base station has been triggered, it directly sets the locomotive's current position to K1+250.000m and simultaneously corrects the encoder's cumulative mileage value to the corresponding value, achieving zero-accumulation calibration of the cumulative error.

[0054] In this embodiment, five calibration base stations divide the 2,800-meter tunnel into six positioning sections, each with a maximum length of approximately 500 meters. The cumulative error of the encoder within the 500-meter range does not exceed 0.3 meters. Combined with the centimeter-level accuracy of UWB ranging, the overall positioning accuracy of the system is better than ±0.5 meters, meeting the requirements for intelligent scheduling of monorail cranes.

[0055] Example 2: Spatial positioning of monorail crane locomotive yard area This embodiment takes the spatial positioning of a monorail crane in a coal mine's underground yard as an example. The yard area has multiple rail branches and intersections, and linear positioning cannot meet the requirements, so planar / spatial positioning is needed.

[0056] (1) System deployment: Positioning base stations A, B, C, and D are deployed at four different locations within the parking lot area. The coordinates of the four base stations are known and they are not coplanar, forming an anchor node array for spatial positioning. The positioning base stations are mounted on the roof of the parking lot using brackets, 3.5 meters above the track surface, with directional antennas pointing downwards to cover the entire parking lot area.

[0057] (2) Spatial positioning and ranging process: After the locomotive base station enters the depot area, it initiates a spatial positioning process: First handshake: The locomotive base station broadcasts a POLL message and records the sending timestamp t1. The four positioning base stations A, B, C, and D all receive the POLL message and record the receiving timestamps t2A, t2B, t2C, and t2D, respectively.

[0058] The second handshake: The four positioning base stations send RESP messages in a time-sharing manner according to their respective preset delay times (base station A delay 0ms, base station B delay 1ms, base station C delay 2ms, base station D delay 3ms), and record the sending timestamps t3A, t3B, t3C, and t3D respectively. Time-sharing transmission avoids signal conflicts caused by multiple base stations sending messages simultaneously.

[0059] The third handshake: The locomotive base station enters the receiving state and cyclically receives RESP messages from each positioning base station, recording the receiving timestamps t4A, t4B, t4C, and t4D respectively. After receiving RESP messages from four base stations, the locomotive base station sends FINAL messages to the four base stations in the receiving order, recording the sending timestamps t5A, t5B, t5C, and t5D respectively.

[0060] The fourth handshake: Each of the four positioning base stations receives a FINAL message directed to itself (FINAL messages from other base stations are ignored), records the received timestamps t6A, t6B, t6C, and t6D, and then returns a LAST message according to a preset delay. The LAST message carries the timestamps t2, t3, and t6 of each base station. The locomotive base station receives the four LAST messages in a loop.

[0061] After obtaining four sets of timestamps, the locomotive base station calculates the distances dA, dB, dC, and dD from the locomotive base station to the four positioning base stations by substituting them into the improved DS-TWR formula. Then, the four distance values ​​are uploaded to the host computer via the Wi-Fi 6 network.

[0062] (3) TDOA coordinate calculation: The host computer establishes a system of spherical equations with the known three-dimensional coordinates (xA, yA, zA), (xB, yB, zB), (xC, yC, zC), and (xD, yD, zD) of the four positioning base stations as the center of the sphere and the corresponding ranging values ​​dA, dB, dC, and dD as the radii: (x xA)² + (y yA)² + (z zA)² = dA²(4) (x xB)² + (y yB)² + (z zB)² = dB²(5) (x xC)² + (y yC)² + (z zC)² = dC²(6) (x xD)² + (y yD)² + (z zD)² = dD²(7) The host computer uses the least squares method to solve the above overdetermined equations to obtain the three-dimensional coordinates (x, y, z) of the locomotive base station, which is the spatial position of the monorail locomotive in the depot area. The positioning update frequency is 10Hz, and the positioning accuracy is better than ±10cm.

[0063] The host computer overlays the real-time locomotive location onto the yard vector map, allowing dispatchers to intuitively see the location and operating status of each locomotive. It also supports playback of historical location trajectories, facilitating post-event analysis and dispatch optimization.

[0064] Example 3: Precise Point-to-Point Parking of Monorail Crane This embodiment takes the precise stopping of a monorail crane at a loading station as an example. The loading station requires the crane's stopping position error to be no more than ±5cm to ensure that the automatic loading equipment can be accurately positioned.

[0065] (1) Calibration base station deployment: Five calibration base stations, numbered C1, C2, C3, C4, and C5, are deployed along the track direction in the loading station area, with a spacing d = 2.0 meters between adjacent calibration base stations. The absolute physical locations (track mileage) of the five calibration base stations are: C1: K0+092.000m, C2: K0+094.000m, C3: K0+096.000m, C4: K0+098.000m, and C5: K0+100.000m. The target parking position is K0+100.000m (i.e., position C5).

[0066] (2) Speed ​​calculation and parking control: The monorail crane travels towards the loading station at a speed of 2 m / s. When the crane's active trigger arm triggers C1, C2, C3, and C4 sequentially, the host computer records the trigger time of each calibration base station. Assume the trigger time of C1 is τ1, the trigger time of C2 is τ2, the trigger time of C3 is τ3, and the trigger time of C4 is τ4.

[0067] The host computer calculates the real-time speed of the vehicle based on the distance d=2.0m between adjacent calibration base stations and the trigger time interval. v1 = d / (τ2) τ1)(8) v2 = d / (τ3) τ2)(9) v3 = d / (τ4) τ3)(10) Take the most recent speed v3 as the locomotive's current speed. Assume τ4. τ3 = 1.05s, then v3 = 2.0 / 1.05 ≈ 1.90m / s.

[0068] The host computer calculates the braking distance based on the locomotive's current speed v3, the target stopping position (C5, 2.0m from C4), and the locomotive braking distance model (braking deceleration a = 0.5m / s²). S_brake = v3² / (2a) =1.90² / (2×0.5)=3.61m (11) Since the braking distance of 3.61m is greater than the distance of 2.0m from C4 to the target position C5, the host computer immediately sends a braking command to the locomotive control system when the locomotive triggers C4. The locomotive begins to decelerate, and when C5 is triggered, the locomotive speed has dropped below 0.1m / s. The control system executes precise stopping, and the final stopping position deviates from the target position K0+100.000m by +3cm, meeting the accuracy requirement of ±5cm.

[0069] Throughout the parking process, each time a calibration base station is triggered, the host computer uses the absolute physical position of that calibration base station to calibrate the locomotive encoder once, ensuring the accuracy of speed calculation and position judgment, and eliminating the impact of cumulative encoder error on fixed-point parking.

[0070] Example 4: Collision avoidance and cascade positioning of monorail cranes on the same track This embodiment uses the collision avoidance of two monorail cranes running on the same track as an example. The front crane is equipped with a locomotive base station (front) and a collision avoidance base station (rear), while the rear crane is equipped with a locomotive base station (front).

[0071] (1) Deployment of anti-collision base stations: One anti-collision base station is deployed at the rear of the leading vehicle (opposite to the locomotive base station). The anti-collision base station consists of a positioning base station with its directional antenna facing backward (towards oncoming vehicles). The directional antenna of the locomotive base station of the leading vehicle faces forward, while the directional antenna of the anti-collision base station faces backward, with their coverage directions being opposite.

[0072] (2) Cascaded positioning process: When two trains are traveling on the same track and are close together, the locomotive base station of the following train and the anti-collision base station at the rear of the preceding train perform UWB ranging to measure the direct distance d_rear between the two trains. At the same time, the locomotive base station of the preceding train measures the distance d_front from the preceding train to the positioning base station on the track. Combined with the known coordinates of the positioning base station, the precise position P_front of the preceding train is determined.

[0073] The host computer calculates the actual position of the following vehicle based on the position of the preceding vehicle P_front, the length of the locomotive itself L (e.g., 12m), and the distance d_rear between the following vehicle and the anti-collision base station: P_rear = P_front L d_rear(12) Where P_front is the position of the front vehicle's front end, L is the length of the front vehicle, and d_rear is the distance from the front of the rear vehicle to the rear of the front vehicle. Through this cascaded positioning method, even if the rear vehicle is in the signal blind zone of the track positioning base station (obstructed by the front vehicle), it can still indirectly obtain a precise position through the front vehicle's anti-collision base station.

[0074] (3) Collision avoidance warning: The locomotive base station prioritizes processing distance information from the anti-collision base station. When d_rear is less than the first-level safety threshold (e.g., 20m), the system sends an audible and visual warning signal to the following vehicle to remind the driver to slow down; when d_rear is less than the second-level safety threshold (e.g., 10m), the system automatically triggers the following vehicle to brake urgently to prevent a rear-end collision.

[0075] In this embodiment, when the following vehicle is unable to communicate directly with the track positioning base station due to obstruction by the preceding vehicle, cascade positioning can still provide a relative position accuracy better than ±15cm, effectively ensuring the safety of multiple vehicles operating on the same track.

[0076] Example 5: Application of passive positioning base stations in areas without power supply This embodiment takes the deployment of positioning base stations in an area without power supply in the extension section of the tunnel as an example. This area is a newly excavated tunnel, and power supply lines have not yet been laid, but temporary positioning base stations need to be deployed to support monorail crane transportation.

[0077] Five passive positioning base stations are deployed in the area. Each passive positioning base station has a built-in high-capacity lithium battery pack (20Ah capacity). With the help of a low-power sleep mechanism, the battery life can reach more than 8 months. The passive positioning base station is normally in a low-power listening state. When it detects a POLL message from the locomotive base station, it immediately wakes up and completes the ranging response. After the response is completed, it returns to the low-power state.

[0078] The passive positioning base station uses an explosion-proof shell, meeting the explosion-proof requirements of underground coal mines. During installation, it only needs to be fixed to a bracket, requiring no wiring, and deployment time is no more than 10 minutes per unit. When the battery power is below 20%, the positioning base station carries a low battery indicator in the LAST message. Upon receiving this message, the host computer generates a maintenance reminder, notifying maintenance personnel to replace or recharge the battery during production breaks.

[0079] This embodiment verifies the feasibility of passive positioning base stations in areas without power supply, enabling the system to be deployed synchronously during tunnel excavation without waiting for power lines to be laid, thus greatly improving the flexibility and timeliness of system deployment.

[0080] The five embodiments above comprehensively verify the effectiveness and versatility of this invention in high-precision positioning and position calibration scenarios for monorail cranes from five dimensions: linear positioning, spatial positioning, fixed-point parking, same-track collision avoidance, and passive deployment. This invention constructs a simple, low-cost, high-precision, and fully functional monorail crane positioning system through reverse base station deployment, improved DS-TWR four-way handshake ranging, passively triggered position calibration, and multi-scenario functional expansion. This system has significant application value for intelligent transportation in coal mines.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision positioning and position calibration system for a monorail crane locomotive, characterized in that, This includes a locomotive base station, several positioning base stations, and a host computer; The locomotive base station is deployed at the head or tail of the monorail locomotive and connects to the existing Wi-Fi 6 network of the monorail locomotive via an RJ45 interface. It communicates with the host computer or dispatch center through the existing network of the locomotive. The positioning base stations are deployed near or on the monorail locomotive track. Each positioning base station does not need to communicate with each other or connect to a network; it only needs to be powered. The directional antenna of the positioning base station is installed opposite to the directional antenna of the locomotive base station, so that the locomotive base station and the positioning base station are always within line of sight during locomotive operation; The locomotive base station and the positioning base station obtain timestamps through four-way handshake message exchange based on UWB technology, and calculate the distance between the locomotive base station and the positioning base station according to the improved DS-TWR bilateral bidirectional ranging algorithm. The locomotive base station uploads distance information to the host computer via the locomotive's existing network. The host computer uses the TDOA algorithm to determine the location coordinates of the monorail locomotive and displays them on the vector map. The system also includes a calibration base station, which is modified from a positioning base station and equipped with a passive triggering module. An active triggering arm is installed on the monorail locomotive. When the active triggering arm triggers the passive triggering module, the calibration base station sends the equipment number to the locomotive base station. The host computer calibrates the cumulative error of the locomotive encoder according to the pre-assigned absolute physical position.

2. The system according to claim 1, characterized in that, The four-way handshake message exchange between the locomotive base station and the positioning base station includes: First handshake: The locomotive base station broadcasts a POLL message and records the sending timestamp t1; Second handshake: The positioning base station receives the POLL message and records the receiving timestamp t2, and after a delay, returns the RESP message and records the sending timestamp t3; The third handshake: The locomotive base station receives the RESP message and records the reception timestamp t4, then sends the FINAL message after a delay and records the sending timestamp t5; Fourth handshake: The positioning base station receives the FINAL message and records the receiving timestamp t6, and returns the LAST message, which carries the timestamps t2, t3, and t6 recorded by the positioning base station. After receiving the LAST message, the locomotive base station calculates the flight time and distance using the following formula.

3. The system according to claim 2, characterized in that, The distance calculation formula for the improved DS-TWR bilateral two-way ranging algorithm is as follows: Tof_dtu=[((t4 t1)×(t6 t3)) ((t5 t4)×(t3 t2))] / (t6+t5 t1 t2) Tof = Tof_dtu × (1 / 499.2e6 / 128) distance = Tof × c Where t1 is the timestamp of the locomotive base station sending the POLL message, t2 is the timestamp of the positioning base station receiving the POLL message, t3 is the timestamp of the positioning base station sending the RESP message, t4 is the timestamp of the locomotive base station receiving the RESP message, t5 is the timestamp of the locomotive base station sending the FINAL message, t6 is the timestamp of the positioning base station receiving the FINAL message, 1 / 499.2e6 / 128 is a time constant, c is the speed of light 299702547 m / s, and distance is in centimeters.

4. The system according to claim 1, characterized in that, The system supports three modes: linear positioning, planar positioning, and spatial positioning. In linear positioning mode, the locomotive base station only performs four handshake distance measurements with a single positioning base station encountered during operation, and determines the linear position of the locomotive on the track based on the distance and track topology. In planar positioning mode, the locomotive base station needs to complete four handshake ranging with at least three positioning base stations simultaneously, and upload the three distance information to the host computer. The host computer uses the TDOA algorithm to calculate the locomotive's planar coordinates. In spatial positioning mode, the locomotive base station needs to complete four handshake distance measurements with at least four positioning base stations simultaneously, and upload the four distance information to the host computer. The host computer uses the TDOA algorithm to calculate the locomotive's spatial coordinates. In planar and spatial positioning, after receiving the POLL message, each positioning base station sends RESP messages in a time-sharing manner according to its own preset different delay time. The locomotive base station cyclically receives the RESP messages and LAST messages from each positioning base station until the required number of positioning base station data is collected or the timeout occurs and the system exits.

5. The system according to claim 1, characterized in that, The passive triggering module of the calibration base station is a mechanical triggering switch or an infrared sensing triggering module. The active triggering arm is installed on the side or top of the monorail locomotive, and its extension length and angle are adjusted according to the installation position of the calibration base station. Each calibration base station has a unique absolute physical position coordinate pre-assigned in the host computer. When the locomotive passes the calibration base station and the active triggering arm triggers the passive triggering module, the locomotive base station receives the equipment number of the calibration base station and uploads it to the host computer. The host computer uses the absolute physical position as the reference value of the locomotive's current position and clears or corrects the position error accumulated by the locomotive encoder.

6. The system according to claim 5, characterized in that, In a specific area where a monorail locomotive needs to stop at a fixed point, multiple sets of equally spaced calibration base stations are deployed along the track direction, with the spacing between adjacent calibration base stations being a preset fixed value d. When the locomotive triggers each calibration base station in sequence, the host computer calculates the actual travel speed of the locomotive v=d / Δt based on the time interval Δt between two adjacent triggers and the spacing d. Combining this with the locomotive braking distance model and the target position for stopping at the fixed point, the host computer sends deceleration and braking commands to the locomotive control system to achieve precise stopping at the fixed point. The absolute physical position of each set of calibration base stations is used to calibrate the locomotive position in real time, eliminating the influence of the cumulative encoder error on the accuracy of stopping at the fixed point.

7. The system according to claim 1, characterized in that, An anti-collision base station is deployed at the rear or front of the monorail crane vehicle, and the anti-collision base station is composed of a positioning base station; When two locomotives traveling on the same track approach each other, the locomotive base station of the locomotive in front measures the distance with the positioning base station on the track, and the locomotive base station of the following locomotive measures the distance with the anti-collision base station of the locomotive in front. The locomotive base station prioritizes processing the distance information of the anti-collision base station. The host computer calculates the actual position of the following vehicle based on the distance between the preceding vehicle and the positioning base station, the length of the locomotive itself, and the distance between the following vehicle and the anti-collision base station, thus realizing the cascade positioning of locomotives on the same track. When the distance between the two vehicles is less than the safety threshold, the system issues an anti-collision warning signal and triggers emergency braking.

8. The system according to claim 1, characterized in that, The positioning base stations include two types: active positioning base stations and passive positioning base stations. Active positioning base stations are powered by AC power and are suitable for areas near the track where there is a power supply. Passive positioning base stations rely on their own built-in batteries for power supply and are suitable for areas without power access. The battery life is no less than 6 months. The positioning base station is installed using a bracket fixing method, and the installation position can be adjusted at any time according to changes in the production layout, without the need for large-scale construction in conjunction with the mine's production plan.

9. The system according to claim 1, characterized in that, The specific process by which the host computer uses the TDOA algorithm to calculate the vehicle's position coordinates is as follows: The host computer receives distance information from multiple positioning base stations uploaded by the locomotive base station. It constructs multiple spherical equations with the known coordinates of each positioning base station as the center and the corresponding distance measurement value as the radius. The three-dimensional coordinates of the locomotive base station are then solved using the least squares method. For linear positioning scenarios, the host computer maps the ranging results to the mileage coordinates of the track centerline based on the track topology data. The host computer overlays the locomotive's real-time location onto the tunnel vector map, supporting functions such as location history trajectory playback, overspeed alarm, and boundary crossing alarm.

10. The system according to claim 1, characterized in that, The system has a single point of failure tolerance mechanism: Each positioning base station operates independently. When a single positioning base station fails, it does not affect the normal operation of other positioning base stations. The system automatically skips the failed base station and uses the data from the remaining normal base stations for positioning calculation. When any one of the four handshakes between the locomotive base station and the positioning base station fails, the locomotive base station re-initiates the ranging process. If the ranging fails three times in a row, the positioning base station is marked as faulty and reported to the host computer. Replacing a fault location base station does not require checking the network lines; it only requires checking the power supply and replacing the equipment. Ordinary electricians can complete the maintenance operation.

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