Railway vehicle accurate positioning system based on track board electronic tag and satellite positioning

Abstract

The invention relates to the technical field of track traffic positioning and navigation, in particular to a railway vehicle accurate positioning system based on track board electronic tags and satellite positioning. The system comprises a data acquisition module used for continuously receiving and evaluating the precision of satellite positioning data; the positioning module is used for selecting a satellite positioning result as a credible reference or switching to inertial navigation positioning according to precision judgment; the tag coordinate acquisition module is used for reading the electronic tag of the track plate and acquiring the corresponding accurate geographic coordinate and moment; and the track tracing correction module is used for tracing to the last credible positioning moment when the electronic tag is read, and performing smooth correction and reconstruction on the middle track by taking the accurate displacement between the two points as a reference and combining inertial navigation data. Accumulated errors generated by inertial navigation during the period of poor satellite signals are intelligently traced and corrected, and high-precision positioning of railway vehicles is achieved.

Description

Technical Field

[0001] This invention relates to the field of rail transit positioning and navigation technology, and in particular to a precise positioning system for railway vehicles based on electronic tags on track slabs and satellite positioning. Background Technology

[0002] Real-time, high-precision positioning of railway vehicles is a key technology for ensuring train operation safety and realizing intelligent scheduling and automatic driving. Currently, the mainstream positioning solutions mainly rely on a combination of Global Navigation Satellite System (GNSS) and Inertial Navigation System (INS). GNSS can provide absolute geographic coordinates, but in environments such as tunnels, valleys, densely populated urban areas, and large stations along railway lines, satellite signals are easily blocked or interfered with by reflections, leading to decreased positioning accuracy or even failure. INS autonomously calculates position based on inertial sensors, without relying on external signals, and has high accuracy in the short term, but its errors accumulate and diverge over time, failing to meet the accuracy requirements for long-term independent operation.

[0003] Chinese Patent Publication No. CN107284474A discloses a method for precise and real-time positioning of locomotives and rolling stock in a metallurgical railway system. The method involves two steps: First, the locomotive's position is determined by reading RFID tags on the track surface using an RFID reader on the locomotive. The information from the locomotive's odometer is then used to correct the information between the ground RFID tags, thus displaying the locomotive's active positioning. Second, the locomotive's vehicle detachment / coupling is determined by reading the vehicle's RFID tags using an RFID reader on the locomotive. Simultaneously, based on the movement of the locomotive following the vehicle after detachment, real-time positioning of the vehicles is achieved through the locomotive's positioning. This invention enables precise positioning of locomotives and rolling stock in metallurgical railways.

[0004] However, existing technologies still have the following problems: By performing instantaneous position correction at the tag points, the cumulative trajectory error generated by inertial navigation during the satellite signal failure period could not be globally traced, modeled, and smoothly corrected, resulting in jumps in the vehicle positioning trajectory and insufficient overall accuracy. Summary of the Invention

[0005] To address this issue, the present invention provides a railway vehicle precise positioning system based on track slab electronic tags and satellite positioning, which overcomes the problem in the prior art that, by performing instantaneous position correction at tag points, fails to globally trace, model, and smoothly correct the cumulative trajectory error generated by inertial navigation during satellite signal failure, resulting in jumps in vehicle positioning trajectory and insufficient overall accuracy.

[0006] To achieve the above objectives, the present invention provides a railway vehicle precise positioning system based on track slab electronic tags and satellite positioning, comprising: The data acquisition module is used to continuously receive satellite positioning data and inertial navigation positioning data, and determine the positioning accuracy of the satellite positioning data based on the number of available satellites in the satellite positioning data and the signal quality of the satellite positioning data. The positioning module, which is connected to the data acquisition module, is used to determine whether to use satellite positioning data as the current position of the vehicle and record the time as a reliable positioning time, or to use inertial navigation positioning data as the current position of the vehicle, based on whether the positioning accuracy of the satellite positioning data meets the preset positioning accuracy requirements. The tag coordinate acquisition module is used to acquire the electronic tag information of the track slab and determine the geographical coordinates and corresponding time of the railway vehicle based on the electronic tag information of the track slab. A trajectory tracing and correction module, which is connected to the data acquisition module, the positioning module, and the tag coordinate acquisition module respectively, includes: The trajectory reference determination unit is used to determine the current time when the electronic tag is acquired, and before the current time, to determine the nearest reliable positioning time and the corresponding current vehicle position. The displacement vector calculation unit is used to determine the vehicle's displacement reference vector based on the time difference between the reliable positioning time and the current time, and the distance between the vehicle's current position and the vehicle position in the electronic tag information of the track board. The trajectory reconstruction unit is used to correct the vehicle trajectory from the reliable positioning time to the current time based on the displacement reference vector and the inertial navigation positioning data, so as to obtain the corrected vehicle position at the current time.

[0007] Furthermore, the data acquisition module determines the positioning accuracy of the satellite positioning data based on a weighted sum of the ratio of the number of available satellites in the satellite positioning data to the preset number of available satellites and the ratio of the signal quality of the satellite positioning data to the preset signal quality.

[0008] Furthermore, the positioning module determines whether to use satellite positioning data as the vehicle's current position and record that moment as a reliable positioning moment, based on whether the positioning accuracy of the satellite positioning data meets a preset positioning accuracy requirement, or to use inertial navigation positioning data as the vehicle's current position. If the positioning accuracy of the satellite positioning data is greater than the preset positioning accuracy, it is determined that the positioning accuracy of the satellite positioning data meets the preset positioning accuracy requirement. The positioning module uses the satellite positioning data as the current position of the vehicle and records the time as the reliable positioning time. If the positioning accuracy of the satellite positioning data is less than or equal to the preset positioning accuracy, it is determined that the positioning accuracy of the satellite positioning data does not meet the preset positioning accuracy requirement, and the positioning module uses inertial navigation positioning data as the vehicle's current position.

[0009] Furthermore, the data acquisition module determines the signal quality of the satellite positioning data based on at least one of the signal-to-noise ratio of the satellite signal, the multipath effect index, and the carrier phase cycle slip count in the satellite positioning data.

[0010] Furthermore, the positioning module uses inertial navigation positioning data as the vehicle's current position, wherein, The positioning module uses the vehicle position corresponding to the last determined reliable positioning time before the positioning accuracy of the satellite positioning data fails to meet the preset positioning accuracy requirement as the integration starting point. The acceleration and angular velocity measurements in the subsequently received inertial navigation positioning data are integrated over time to determine the relative displacement of the vehicle relative to the integration start point from the time of the reliable positioning. The relative displacement is vector-superimposed with the coordinates of the integration starting point to obtain the vehicle's current position when using inertial navigation positioning data.

[0011] Furthermore, the displacement vector calculation unit determines the vehicle's displacement reference vector based on the time difference between the reliable positioning time and the current time, and the distance between the vehicle's current position and the vehicle's position in the electronic tag information of the track slab. Using the vehicle's current position at the trusted positioning time as the starting point of the vector and the vehicle's position corresponding to the electronic tag information on the track board at the current time as the ending point of the vector, a total displacement vector is calculated. Divide the magnitude of the total displacement vector by the time difference to obtain an average velocity vector; The average velocity vector is multiplied by the time difference to obtain the vehicle's displacement reference vector.

[0012] Furthermore, the trajectory reconstruction unit, based on the displacement reference vector and combined with the inertial navigation positioning data, corrects the vehicle trajectory from the reliable positioning time to the current time to obtain the corrected vehicle position at the current time, wherein... Based on the inertial navigation positioning data from the trusted positioning time to the current time, extract the displacement increment sequence that characterizes the displacement change of the vehicle within a continuous time interval; Starting from the vehicle position at the reliable positioning time, the displacement increment sequence is accumulated to obtain the inertial navigation calculated trajectory; Determine the difference vector between the displacement reference vector and the total displacement vector of the inertial navigation calculated trajectory; The difference vector is allocated and superimposed on each displacement increment of the inertial navigation calculated trajectory according to a preset ratio to generate a smoothed and corrected continuous trajectory. The endpoint of the continuous trajectory is taken as the corrected vehicle position at the current moment.

[0013] Furthermore, the displacement vector calculation unit extracts a sequence of displacement increments characterizing the vehicle's displacement changes over continuous time intervals, based on the inertial navigation positioning data from the reliable positioning time to the current time. Obtain acceleration and angular velocity measurements at consecutive timestamps from inertial navigation and positioning data; By integrating the acceleration and angular velocity measurements over time, the three-dimensional displacement change of the vehicle between adjacent time points is obtained. All the obtained three-dimensional displacement changes are arranged in chronological order to form the displacement increment sequence.

[0014] Furthermore, the trajectory reconstruction unit distributes and superimposes the difference vector onto each displacement increment of the inertial navigation calculated trajectory according to a preset ratio, generating a smoothed and corrected continuous trajectory, wherein... Obtain the complete time interval from the trusted positioning time to the current time, and the time corresponding to each displacement increment in the displacement increment sequence; Based on the relative position of the time corresponding to each displacement increment within the complete time interval, determine the linear allocation weight coefficient corresponding to each displacement increment; Multiply the difference vector by the linear weighting coefficient corresponding to each displacement increment to obtain the correction vector assigned to each displacement increment; Each displacement increment is superimposed with its corresponding correction subvector to form a corrected displacement increment. All corrected displacement increments are then accumulated in chronological order to generate a smoothed, corrected continuous trajectory.

[0015] Furthermore, the tag coordinate acquisition module determines the geographical coordinates and corresponding time of the railway vehicle based on the electronic tag information on the track slab, wherein... The tag coordinate acquisition module reads the electronic tag embedded in the track slab, parses the unique tag identification code stored in the electronic tag, and queries the geographic coordinates corresponding to the unique tag identification code stored in the electronic tag (or directly uses the geographic coordinates stored in the electronic tag) according to the preset mapping relationship database between tag identification codes and geographic coordinates. At the same time, it records the timestamp when the electronic tag is read, and associates the geographic coordinates with the timestamp for output.

[0016] Compared with existing technologies, the advantages of this invention lie in its ability to achieve continuous and high-precision determination of vehicle position in complex railway environments with intermittent satellite signals by integrating satellite positioning, inertial navigation, and electronic tag information from track slabs, and introducing trajectory tracing and smoothing correction mechanisms. Specifically, the system intelligently switches to inertial navigation in real time to maintain positioning continuity by evaluating satellite positioning accuracy. Utilizing the absolute position reference provided by the electronic tags, the system not only corrects the instantaneous position when reading the tags, but more importantly, it performs error modeling and smoothing reconstruction of the entire inertial navigation-calculated trajectory since the last reliable positioning point. This effectively suppresses the accumulation of errors in inertial navigation, eliminates trajectory jumps, and ultimately outputs a seamless vehicle trajectory with significantly improved global accuracy across the entire railway section, greatly enhancing the robustness and reliability of the positioning system.

[0017] Furthermore, this invention effectively solves the long-standing positioning problem of railway vehicles in areas with poor satellite signals by introducing a trajectory tracing and correction mechanism based on track slab electronic tags. The system utilizes the absolute coordinates provided by the electronic tags to form a high-precision "displacement reference" with the previous reliable satellite positioning point. It models the cumulative trajectory error calculated by inertial navigation during signal interruptions as a global deviation. By smoothing and correcting this deviation over time, it not only accurately calibrates the vehicle position to the tag point, but more importantly, reconstructs a globally continuous, non-abrupt historical trajectory that strictly matches the known absolute position. This significantly improves the continuity, smoothness, and overall reliability of the positioning system, providing a solid position reference for intelligent train operation control.

[0018] Furthermore, this invention establishes a precise error analysis object for subsequent trajectory correction by accurately extracting and constructing a complete inertial navigation displacement increment sequence from the previous trusted point to the current tag point. This sequence fully preserves the continuity and dynamic details of the inertial navigation calculated trajectory. By comparing it with the "displacement reference vector" determined by two absolute position points (the trusted point and the tag point), the total displacement error vector accumulated by the inertial navigation during that time period can be accurately calculated. This allows the overall error to be accurately distributed to each local segment of the trajectory, thereby generating a globally continuous and physically meaningful optimized trajectory while ensuring absolute accuracy at the start and end points. Ultimately, this achieves effective suppression and correction of accumulated inertial navigation errors.

[0019] Furthermore, this invention utilizes a time-linear weighted difference vector allocation and superposition algorithm to intelligently and smoothly distribute the total displacement error accumulated by inertial navigation during satellite signal failure into each historical segment of the trajectory. This method not only ensures that the start and end points of the corrected trajectory perfectly match the known absolute reference points (trusted satellite positioning points and electronic tag points), but more importantly, by performing a linear allocation of errors that conforms to time continuity, the reconstructed intermediate trajectory transitions naturally in shape, effectively avoiding the trajectory jump problem caused by traditional "hard correction" methods. This generates a globally continuous, smooth vehicle operation history trajectory with significantly improved overall accuracy, achieving an optimized upgrade from discrete absolute position points to continuous high-precision trajectories. Attached Figure Description

[0020] Figure 1 This is a structural block diagram of the railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to the present invention; Figure 2 This is a flowchart illustrating the process of determining the current position of a vehicle according to the present invention. Detailed Implementation

[0021] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0022] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] Please see Figures 1-2 As shown, Figure 1 This is a structural block diagram of the railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to the present invention; Figure 2 This is a flowchart illustrating the process of determining the current position of a vehicle according to the present invention.

[0024] This invention relates to a railway vehicle precise positioning system based on track slab electronic tags and satellite positioning, comprising: The data acquisition module is used to continuously receive satellite positioning data and inertial navigation positioning data, and determine the positioning accuracy of the satellite positioning data based on the number of available satellites in the satellite positioning data and the signal quality of the satellite positioning data. The positioning module, which is connected to the data acquisition module, is used to determine whether to use satellite positioning data as the current position of the vehicle and record the time as a reliable positioning time, or to use inertial navigation positioning data as the current position of the vehicle, based on whether the positioning accuracy of the satellite positioning data meets the preset positioning accuracy requirements. The tag coordinate acquisition module is used to acquire the electronic tag information of the track slab and determine the geographical coordinates and corresponding time of the railway vehicle based on the electronic tag information of the track slab. A trajectory tracing and correction module, which is connected to the data acquisition module, the positioning module, and the tag coordinate acquisition module respectively, includes: The trajectory reference determination unit is used to determine the current time when the electronic tag is acquired, and before the current time, to determine the nearest reliable positioning time and the corresponding current vehicle position. The displacement vector calculation unit is used to determine the vehicle's displacement reference vector based on the time difference between the reliable positioning time and the current time, and the distance between the vehicle's current position and the vehicle position in the electronic tag information of the track board. The trajectory reconstruction unit is used to correct the vehicle trajectory from the reliable positioning time to the current time based on the displacement reference vector and the inertial navigation positioning data, so as to obtain the corrected vehicle position at the current time.

[0025] In this embodiment of the invention, the satellite positioning data includes, but is not limited to, pseudorange, carrier phase, Doppler shift, satellite ephemeris, and time information from global navigation satellite systems such as GPS, BeiDou, GLONASS, and Galileo, as well as the latitude, longitude, elevation, velocity, and direction calculated therefrom. The inertial navigation positioning data includes, but is not limited to, specific force / acceleration data measured by a three-axis accelerometer from an inertial measurement unit (IMU), and angular velocity / angular increment data measured by a three-axis gyroscope. By integrating these data, the vehicle's attitude (roll, pitch, heading), velocity, and position changes can be calculated.

[0026] Specifically, the data acquisition module determines the positioning accuracy of the satellite positioning data based on a weighted sum of the ratio of the number of available satellites in the satellite positioning data to the preset number of available satellites and the ratio of the signal quality of the satellite positioning data to the preset signal quality.

[0027] In this embodiment of the invention, the preset number of available satellites is determined based on typical satellite visibility analysis of the railway line area. Using historical satellite ephemeris data or satellite visibility simulation software, the number of satellites and signal-to-noise ratio (SNR) that the system can stably receive for most of the time (e.g., more than 95% of the time) are analyzed, and this number and SNR are used as a benchmark. For example, if the analysis shows that the area can typically receive stable signals from more than 8 satellites simultaneously with a SNR of 85, then the preset number of satellites can be set to 8, and the preset SNR to 85. The preset signal quality is determined based on the typical performance indicators of the selected satellite positioning receiver in an open, unobstructed, and interference-free environment. In a standard test environment (e.g., a standard test field), the stable values ​​or average values ​​of the receiver's output signal quality parameters (such as SNR) are recorded and statistically analyzed over a long period. For example, if the statistically determined stable signal quality metric is approximately 85 (assuming a normalized value) under excellent conditions, then this preset value can be set to 85.

[0028] In this embodiment of the invention, the preset positioning accuracy threshold is determined based on the specific accuracy requirements of the railway vehicle positioning application scenario. It comprehensively considers the maximum allowable position error for needs such as train control, safety warnings, or mileage calibration. For example, if the application requires satellite positioning to have a horizontal positioning error better than 2.5 meters when used alone (which can be converted or correspond to an internal evaluation score), this requirement is converted into a score under the system's internal evaluation scale, for example, setting the preset value to 80 (assuming a percentage system). This threshold is used to determine whether to use the satellite positioning result. The weighting coefficients in the weighted sum calculation are based on the relative importance of the number of satellites and signal quality to the final positioning accuracy, and are determined through experimental calibration or empirical allocation. For example, the contribution ratio of the two is determined by comparing the changes in actual positioning error under different combinations of satellite numbers and signal quality. A simple empirical setting is: sufficiency of the number of satellites is considered fundamental, while signal quality is key to accuracy; therefore, a higher weight is given to signal quality. For example, the weight of the satellite number ratio is set to 0.4, and the weight of the signal quality ratio is set to 0.6.

[0029] Specifically, the positioning module determines whether to use satellite positioning data as the vehicle's current position and record that moment as a reliable positioning moment, based on whether the positioning accuracy of the satellite positioning data meets a preset positioning accuracy requirement, or to use inertial navigation positioning data as the vehicle's current position. If the positioning accuracy of the satellite positioning data is greater than the preset positioning accuracy, it is determined that the positioning accuracy of the satellite positioning data meets the preset positioning accuracy requirement. The positioning module uses the satellite positioning data as the current position of the vehicle and records the time as the reliable positioning time. If the positioning accuracy of the satellite positioning data is less than or equal to the preset positioning accuracy, it is determined that the positioning accuracy of the satellite positioning data does not meet the preset positioning accuracy requirement, and the positioning module uses inertial navigation positioning data as the vehicle's current position.

[0030] In this embodiment of the invention, the preset positioning accuracy threshold is determined based on the maximum acceptable error for satellite positioning in railway vehicle applications. It is determined by statistically analyzing the deviation distribution between the satellite positioning calculation results and higher-precision benchmarks (such as differential reference stations and high-precision electronic tag points) on typical application sections (including scenarios with slight obstruction but not complete failure). For example, analysis shows that when the satellite positioning evaluation value is higher than 80 points (assuming a percentage system), there is a 95% probability that the actual positioning error is less than the application-allowed 2.5 meters. Therefore, the preset positioning accuracy threshold can be set to 80. If the current evaluation value is greater than 80 (e.g., a calculated value of 85), the satellite positioning data is deemed to meet the accuracy requirements. At this time, the positioning module directly uses the latitude, longitude, and elevation calculated from the current satellite positioning data as the vehicle's current position. Simultaneously, the system marks and stores this moment as a "reliable positioning moment" and synchronously records the corresponding precise position coordinates. This "reliable positioning moment" and its position will serve as the starting point for subsequent inertial navigation integration or the reference point for trajectory tracing. If the current evaluation value is less than or equal to 80 (for example, a calculated value of 75 or lower), the satellite positioning data is deemed insufficient to meet accuracy requirements. In this case, the positioning module will not use the current satellite positioning data as its output. Instead, it will initiate or continue using inertial navigation positioning data, calculating and outputting the vehicle's current position through integration. The system will not record this moment as a "reliable positioning moment."

[0031] Specifically, the data acquisition module determines the signal quality of the satellite positioning data based on at least one of the signal-to-noise ratio of the satellite signal, the multipath effect index, and the carrier phase cycle slip count in the satellite positioning data.

[0032] In this embodiment of the invention, the positioning module comprehensively evaluates signal quality based on the analysis of raw satellite observation data. Specifically, it quantifies the signal quality through three dimensions: signal-to-noise ratio (SNR), multipath effect index, and carrier phase cycle slip count. Each dimension has a judgment threshold, and a final overall signal quality assessment value is synthesized. In specific implementation, the preset parameters involved and their simple determination methods are as follows: Excellent SNR threshold: Determined based on the typical performance of the satellite navigation receiver under unobstructed open sky conditions. A stable high value is taken as a benchmark by long-term collection of SNR data for satellite signals at various frequencies under excellent conditions. Multipath effect impact threshold: Based on the receiver's output multipath error estimate (such as the multipath index calculated based on pseudorange and carrier phase combination), its noise level is statistically analyzed under a non-reflective environment, considering the acceptable interference level in railway scenarios. For example, statistical analysis shows that this index is usually less than 0.3 meters under good conditions, while the positioning error increases significantly when it exceeds 0.6 meters. Therefore, this threshold can be set to 0.6 meters. Carrier phase cycle slip count tolerance: Determined based on the performance of the receiver's carrier phase tracking loop and the application's requirement for continuity. In static or low-speed, stable scenarios, the number of natural cycle slips occurring per unit time is used as the basis for testing. For example, tests show that under good conditions, a single satellite experiences very few cycle slips per minute, typically less than one. Considering the dynamic stress of vehicle operation, this tolerance can be appropriately relaxed, setting the cycle slip count tolerance at three times per minute.

[0033] In this embodiment of the invention, the positioning module performs the following analyses on the observation data of each available satellite: Signal-to-noise ratio (SNR) evaluation: Calculate the ratio of the current SNR to the SNR good threshold (45dB-Hz). If the current value is higher than the threshold, the score for this item is high. Multipath effect evaluation: Calculate the comparison value between the current multipath index and the multipath effect impact threshold (0.6 meters) (e.g., threshold divided by the current value). If the current value is lower than the threshold, the score for this item is high. Cycle slip evaluation: Count the number of cycle slips in the current minute and compare it with the cycle slip count tolerance (3 times). If the number is lower than the tolerance, the score for this item is high. Subsequently, the module integrates the above scores for all available satellites (e.g., taking the average or weighted average), and then weights and fuses the integrated scores of the three dimensions again (e.g., SNR weight 0.5, multipath weight 0.3, cycle slip weight 0.2), finally generating a normalized signal quality evaluation value (e.g., a value between 0 and 100). This value will be provided to the data acquisition module for the overall satellite positioning accuracy evaluation calculation described above.

[0034] Specifically, the positioning module uses inertial navigation positioning data as the vehicle's current position, wherein... The positioning module uses the vehicle position corresponding to the last determined reliable positioning time before the positioning accuracy of the satellite positioning data fails to meet the preset positioning accuracy requirement as the integration starting point. The acceleration and angular velocity measurements in the subsequently received inertial navigation positioning data are integrated over time to determine the relative displacement of the vehicle relative to the integration start point from the time of the reliable positioning. The relative displacement is vector-superimposed with the coordinates of the integration starting point to obtain the vehicle's current position when using inertial navigation positioning data.

[0035] In this embodiment of the invention, when the positioning module determines that inertial navigation positioning data is required, it executes the following positioning calculation process: First, the system immediately locks and retrieves the last successfully recorded reliable positioning time and its corresponding precise geographic coordinates (latitude, longitude, and elevation) before the satellite positioning accuracy fails to meet the requirements, and sets this coordinate as the integration starting point for inertial navigation calculation. Subsequently, the positioning module continuously receives raw data from the inertial measurement unit, including specific force information (acceleration measurement value) measured by the three-axis accelerometer and angular velocity information (angular velocity measurement value) measured by the three-axis gyroscope. By performing time integration on the angular velocity measurement value, the vehicle's attitude angles (roll, pitch, and heading) are calculated and updated in real time. Based on this, the acceleration measurement value is transformed from the vehicle coordinate system to the navigation coordinate system using the current attitude, and a second time integration is performed on the transformed acceleration, thereby continuously calculating the relative displacement vector of the vehicle relative to the integration starting point in three-dimensional space from the reliable positioning time. Finally, the positioning module superimposes the real-time calculated relative displacement vector with the reliable position coordinates used as the integration starting point to obtain and output the vehicle's current position coordinates calculated from the inertial navigation data. This process continues until the satellite positioning accuracy meets the requirements again.

[0036] This invention achieves continuous and high-precision vehicle position determination in complex railway environments with intermittent satellite signals by integrating satellite positioning, inertial navigation, and electronic tag information from track slabs, and by introducing trajectory tracing and smoothing correction mechanisms. Specifically, the system intelligently switches to inertial navigation in real time to maintain positioning continuity by evaluating satellite positioning accuracy. Utilizing the absolute position reference provided by the electronic tags, the system not only corrects the instantaneous position when reading the tags, but more importantly, it performs error modeling and smoothing reconstruction of the entire inertial navigation-calculated trajectory since the last reliable positioning point. This effectively suppresses the accumulation of errors in inertial navigation, eliminates trajectory jumps, and ultimately outputs a seamless vehicle trajectory with significantly improved global accuracy across the entire railway section, greatly enhancing the robustness and reliability of the positioning system.

[0037] Specifically, the displacement vector calculation unit determines the vehicle's displacement reference vector based on the time difference between the reliable positioning time and the current time, and the distance between the vehicle's current position and the vehicle's position in the electronic tag information of the track slab. Using the vehicle's current position at the trusted positioning time as the starting point of the vector and the vehicle's position corresponding to the electronic tag information on the track board at the current time as the ending point of the vector, a total displacement vector is calculated. Divide the magnitude of the total displacement vector by the time difference to obtain an average velocity vector; The average velocity vector is multiplied by the time difference to obtain the vehicle's displacement reference vector.

[0038] In this embodiment of the invention, firstly, the unit acquires two precise spatial reference points and their corresponding times: one is the precise vehicle position corresponding to the "reliable positioning time" closest to the current time, determined and recorded by the system, denoted as point A (including latitude, longitude, and elevation); the other is the precise vehicle position provided by the tag coordinate acquisition module at the current time, parsed from the electronic tag on the track board, denoted as point B (also including latitude, longitude, and elevation). Simultaneously, the unit records the time difference between these two event points, denoted as Δt. Next, the unit performs vector calculations: Calculating the total displacement vector: with point A as the starting point and point B as the ending point, calculate the three-dimensional spatial vector AB in the geographic coordinate system. This vector is the total displacement from the previous reliable position to the current tag position. Calculating the average velocity vector: calculate the magnitude of the total displacement vector AB (i.e., the straight-line distance between points A and B), and then divide it by the time difference Δt to obtain a scalar value, namely the average velocity magnitude v_avg. Simultaneously, the unit vector u_AB in the direction of the total displacement vector AB is acquired. Multiplying the average speed magnitude v_avg by the unit direction vector u_AB yields the average speed vector V_avg. This vector represents the average speed magnitude and direction of the vehicle's movement from point A to point B. Determining the displacement reference vector: Perform a scalar multiplication operation between the average speed vector V_avg and the time difference Δt, i.e., V_avg × Δt. Physically, the average speed vector multiplied by time equals the displacement. Since V_avg = v_avg × u_AB, and v_avg = |AB| / Δt, therefore V_avg × Δt = (|AB| / Δt) × u_AB × Δt = |AB| × u_AB = vector AB. Therefore, the final determined "vehicle displacement reference vector" is the total displacement vector AB itself.

[0039] This invention effectively solves the long-standing positioning problem of railway vehicles in areas with poor satellite signals by introducing a trajectory tracing and correction mechanism based on electronic tags on track slabs. The system utilizes the absolute coordinates provided by the electronic tags to form a high-precision "displacement reference" with the previous reliable satellite positioning point. It models the cumulative trajectory error calculated by inertial navigation during signal interruptions as a global deviation. By smoothing and correcting this deviation over time, it not only accurately calibrates the vehicle position to the tag point, but more importantly, reconstructs a globally continuous, non-abrupt historical trajectory that strictly matches the known absolute position. This significantly improves the continuity, smoothness, and overall reliability of the positioning system, providing a solid position reference for intelligent train operation control.

[0040] Specifically, the trajectory reconstruction unit, based on the displacement reference vector and combined with the inertial navigation positioning data, corrects the vehicle trajectory from the reliable positioning time to the current time to obtain the corrected vehicle position at the current time. Based on the inertial navigation positioning data from the trusted positioning time to the current time, extract the displacement increment sequence that characterizes the displacement change of the vehicle within a continuous time interval; Starting from the vehicle position at the reliable positioning time, the displacement increment sequence is accumulated to obtain the inertial navigation calculated trajectory; Determine the difference vector between the displacement reference vector and the total displacement vector of the inertial navigation calculated trajectory; The difference vector is allocated and superimposed on each displacement increment of the inertial navigation calculated trajectory according to a preset ratio to generate a smoothed and corrected continuous trajectory. The endpoint of the continuous trajectory is taken as the corrected vehicle position at the current moment.

[0041] In this embodiment of the invention, the trajectory reconstruction unit uses the precise vehicle position (point A) at the reliable positioning time as the trajectory starting point, and calculates the displacement increment sequence provided by the displacement vector calculation unit. Vectors are accumulated sequentially over time. The coordinates P_k of the k-th accumulation point can be calculated using the formula P_k=A+Σ_{i=1}^{k}Δs_i. By connecting all these accumulation points, a complete inertial navigation calculated trajectory is obtained, and its endpoint (i.e., the sum of all displacement increments plus the starting point A) is denoted as point P_end. The vector pointing from the starting point A to this calculated endpoint P_end is calculated to obtain the total displacement vector AP_end calculated by inertial navigation. Next, the element calculates the difference vector E between the displacement reference vector (denoted as vector AB, pointing from point A to tag point B) and the total displacement vector AP_end calculated by inertial navigation. That is, the difference vector E=AB-AP_end. This difference vector E represents the total displacement error accumulated by inertial navigation during this time period.

[0042] Subsequently, the unit performs the core smoothing correction process. It decomposes the total difference vector E according to a preset scaling rule (e.g., a time-based linear scaling) and distributes it to each displacement increment Δs_i. Specifically, it calculates a corresponding correction vector c_i for each displacement increment Δs_i in the sequence, satisfying Σ_{i=1}^{n}c_i=E. Then, it superimposes each displacement increment Δs_i with its corresponding correction vector c_i to obtain the corrected displacement increment Δs'_i=Δs_i+c_i. Finally, the unit uses the starting point A as a reference to process the corrected displacement increment sequence... The data is re-accumulated chronologically to generate a smoothed, corrected continuous trajectory. The endpoint B' of this new trajectory is calculated using the formula B'=A+Σ{i=1}^{n}Δs'_i. Since the correction process ensures that the total error vector is fully distributed (Σc_i=E), and A+ΣΔs_i=P_end, it can be deduced that B'=A+Σ(Δs_i+c_i)=P_end+E=(A+AP_end)+(AB-AP_end)=A+AB=B. This means that the endpoint B' of the corrected trajectory is strictly equal to the precise location B of the electronic tag. The trajectory reconstruction unit outputs this endpoint B' as the corrected vehicle position at the current moment. Simultaneously, the entire corrected continuous trajectory [P'_1,P'_2,...,P'_n,B'] is updated to the authoritative trajectory record of the system within that time period.

[0043] Specifically, the displacement vector calculation unit extracts a sequence of displacement increments characterizing the vehicle's displacement changes over continuous time intervals, based on the inertial navigation positioning data from the reliable positioning time to the current time. Obtain acceleration and angular velocity measurements at consecutive timestamps from inertial navigation and positioning data; By integrating the acceleration and angular velocity measurements over time, the three-dimensional displacement change of the vehicle between adjacent time points is obtained. All the obtained three-dimensional displacement changes are arranged in chronological order to form the displacement increment sequence.

[0044] In this embodiment of the invention, the displacement vector calculation unit reads all the raw inertial navigation positioning data recorded in chronological order from the data storage area during the time from the trusted positioning time to the current time when the electronic tag is read. This data includes a series of measurements with precise timestamps, primarily including triaxial acceleration measurements from a triaxial accelerometer and triaxial angular velocity measurements from a triaxial gyroscope. Then, for each pair of adjacent timestamps (e.g., time t_k and the next time t_{k+1}), the unit performs standard inertial navigation calculations using the inertial measurement data within that time interval. Specifically: using the angular velocity data measured by the gyroscope, the attitude change of the vehicle from time t_k to t_{k+1} (i.e., the rotation of the vehicle coordinate system relative to the navigation coordinate system) is calculated through integration. Then, using the calculated attitude change, the specific force information measured by the accelerometer in the vehicle coordinate system is converted to the navigation coordinate system (e.g., the northeast-northeast geographic coordinate system). Finally, the acceleration information in the navigation coordinate system is integrally processed over time to calculate the three-dimensional displacement change Δs_k of the vehicle between adjacent timestamps (i.e., within the time interval Δt_k = t_{k+1} - t_k). This displacement change is a three-dimensional vector representing the vehicle's displacement components in the east, north, and sky directions within this small time interval. This process is repeated for each consecutive small time interval from the reliable positioning time to the current time, sequentially calculating the three-dimensional displacement change Δs_1, Δs_2, ..., Δs_n for each time interval. Finally, the displacement vector calculation unit sequentially arranges and combines all the three-dimensional displacement changes Δs_1, Δs_2, ..., Δs_n calculated in chronological order to form a complete sequence, namely the displacement increment sequence. This sequence fully records every minute displacement of the vehicle's continuous trajectory from the reliable positioning time to the current time, calculated by the inertial navigation system. It serves as the foundational data for subsequent trajectory comparison and error correction.

[0045] This invention establishes a precise error analysis object for subsequent trajectory correction by accurately extracting and constructing a complete sequence of inertial navigation displacement increments from the previous reliable point to the current tag point. This sequence fully preserves the continuity and dynamic details of the inertial navigation trajectory. By comparing it with the "displacement reference vector" determined by two absolute position points (the reliable point and the tag point), the total displacement error vector accumulated by the inertial navigation during that time period can be accurately calculated. This allows for the precise allocation of the overall error to each local segment of the trajectory, thereby generating a globally continuous and physically meaningful optimized trajectory while ensuring absolute accuracy at the start and end points. Ultimately, this effectively suppresses and corrects the accumulated error of the inertial navigation.

[0046] Specifically, the trajectory reconstruction unit distributes and superimposes the difference vector onto each displacement increment of the inertial navigation calculated trajectory according to a preset ratio, generating a smoothed and corrected continuous trajectory, wherein... Obtain the complete time interval from the trusted positioning time to the current time, and the time corresponding to each displacement increment in the displacement increment sequence; Based on the relative position of the time corresponding to each displacement increment within the complete time interval, determine the linear allocation weight coefficient corresponding to each displacement increment; Multiply the difference vector by the linear weighting coefficient corresponding to each displacement increment to obtain the correction vector assigned to each displacement increment; Each displacement increment is superimposed with its corresponding correction subvector to form a corrected displacement increment. All corrected displacement increments are then accumulated in chronological order to generate a smoothed, corrected continuous trajectory.

[0047] In this embodiment of the invention, the trajectory reconstruction unit distributes and superimposes the difference vector onto each displacement increment of the inertial navigation calculated trajectory according to a preset ratio to generate a smoothed and corrected continuous trajectory. The specific implementation steps are as follows: First, the trajectory reconstruction unit acquires the complete time interval from the reliable positioning time (denoted as time T_start) to the current time of reading the electronic tag (denoted as time T_end), with a total duration ΔT = T_end - T_start. Simultaneously, the unit acquires the displacement increment sequence. The precise time interval corresponding to each displacement increment Δs_i in the sequence is determined (e.g., from time t_i to time t_{i+1}). To simplify the calculation, the midpoint time T_i of the time interval corresponding to each displacement increment is usually taken as its representative time.

[0048] Next, the element calculates a linear weighting coefficient w_i for each displacement increment Δs_i. This coefficient is determined based on the relative position of its representative moment T_i within the total time interval [T_start, T_end]. The specific calculation formula is: w_i = (T_i - T_start) / ΔT. This formula ensures that the weighting coefficient w_i is uniformly distributed between 0 and 1 (when i increases from 1 to n), and the sum of all weighting coefficients Σw_i is theoretically equal to n / 2 (when the increments are uniformly distributed). To ensure that all error corrections are fully allocated, the weights need to be normalized, i.e., the final weighting coefficient k_i = w_i / (Σ_{j=1}^{n}w_j) for each increment is calculated. After normalization, the sum of all k_i is strictly equal to 1.

[0049] Then, the unit performs a scalar multiplication of the total difference vector E with the normalized weighting coefficient k_i corresponding to each displacement increment, obtaining a correction vector c_i specifically assigned to that displacement increment Δs_i. That is: c_i = k_i × E. Since Σk_i = 1, the sum of all correction vectors Σc_i is strictly equal to the total difference vector E, ensuring that the error is fully distributed.

[0050] Finally, the unit performs vector superposition and trajectory reconstruction. Each original displacement increment Δs_i is added to its corresponding correction sub-vector c_i to obtain the corrected displacement increment Δs'_i = Δs_i + c_i. Then, starting from the vehicle position (point A) at the reliable positioning time, the corrected displacement increment sequence is... Vector accumulation is performed strictly in chronological order to obtain a series of intermediate correction points, culminating in the endpoint. Connecting all these points generates a smoothed, corrected, continuous trajectory. This trajectory starts at a precise point A and ends precisely at the electronic tag's location point B. Furthermore, the intermediate trajectory shape is linearly and smoothly transitioned over time based on the trajectory calculated by inertial navigation, eliminating trajectory jumps.

[0051] This invention utilizes a time-linear weighted difference vector allocation and superposition algorithm to intelligently and smoothly distribute the total displacement error accumulated by inertial navigation during satellite signal failures across each historical segment of the trajectory. This method not only ensures that the start and end points of the corrected trajectory perfectly align with known absolute reference points (reliable satellite positioning points and electronic tag points), but more importantly, by applying a time-continuous linear distribution of the error, the reconstructed intermediate trajectory exhibits a natural transition in form. This effectively avoids the trajectory jump problems associated with traditional "hard correction" methods, thereby generating a globally continuous, smooth vehicle operation history trajectory with significantly improved overall accuracy. This represents an optimized upgrade from discrete absolute position points to continuous high-precision trajectories.

[0052] Specifically, the tag coordinate acquisition module determines the geographical coordinates and corresponding time of the railway vehicle based on the electronic tag information on the track slab, wherein... The tag coordinate acquisition module reads the electronic tag embedded in the track slab, parses the unique tag identification code stored in the electronic tag, and queries the geographic coordinates corresponding to the unique tag identification code stored in the electronic tag (or directly uses the geographic coordinates stored in the electronic tag) according to the preset mapping relationship database between tag identification codes and geographic coordinates. At the same time, it records the timestamp when the electronic tag is read, and associates the geographic coordinates with the timestamp for output.

[0053] In this embodiment of the invention, firstly, when an RFID reader or other dedicated reading device installed on the bottom of the vehicle enters the effective reading range of an electronic tag (such as a passive UHF RFID tag) pre-embedded in the track slab as the vehicle moves, the tag coordinate acquisition module drives the reader to activate and read the electronic tag. Next, the module receives and parses the response data from the electronic tag from the reader, extracting the unique tag identification code stored in the tag chip. This identification code is typically a globally unique string of numbers or characters, serving as a digital "identity card" for that specific track slab location. Then, the module accesses a pre-built or remotely connected database of tag identification codes and geographic coordinate mappings (or directly uses the geographic coordinates stored in the electronic tag). This database is established before system deployment, where each record is precisely associated with a tag identification code and its corresponding three-dimensional geographic coordinates (longitude, latitude, and elevation) in the absolute coordinate system of the railway line (such as the national geodetic coordinate system). The module uses the read identification code as a query keyword to initiate a query to the database and receives the returned high-precision geographic coordinate value precisely bound to the identification code. Simultaneously, upon successfully reading the tag, the module precisely records the timestamp of the event. This timestamp originates from a high-precision clock source synchronized with the entire positioning system. Finally, the module associates and encapsulates the retrieved geographic coordinates with the recorded precise timestamp, outputting a complete data packet (containing "location-time" pairs) for use by the trajectory tracing and correction module. This output provides the system with a discrete absolute position reference point at a specific absolute moment, with decimeter-level or higher precision, serving as a crucial trigger input and accuracy anchor for the entire trajectory tracing and correction process.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A railway vehicle precise positioning system based on track slab electronic tags and satellite positioning, characterized in that, include: The data acquisition module is used to continuously receive satellite positioning data and inertial navigation positioning data, and determine the positioning accuracy of the satellite positioning data based on the number of available satellites in the satellite positioning data and the signal quality of the satellite positioning data. The positioning module, which is connected to the data acquisition module, is used to determine whether to use satellite positioning data as the current position of the vehicle and record the time as a reliable positioning time, or to use inertial navigation positioning data as the current position of the vehicle, based on whether the positioning accuracy of the satellite positioning data meets the preset positioning accuracy requirements. The tag coordinate acquisition module is used to acquire the electronic tag information of the track slab and determine the geographical coordinates and corresponding time of the railway vehicle based on the electronic tag information of the track slab. A trajectory tracing and correction module, which is connected to the data acquisition module, the positioning module, and the tag coordinate acquisition module respectively, includes: The trajectory reference determination unit is used to determine the current time when the electronic tag is acquired, and before the current time, to determine the nearest reliable positioning time and the corresponding current vehicle position. The displacement vector calculation unit is used to determine the vehicle's displacement reference vector based on the time difference between the reliable positioning time and the current time, and the distance between the vehicle's current position and the vehicle position in the electronic tag information of the track board. The trajectory reconstruction unit is used to correct the vehicle trajectory from the reliable positioning time to the current time based on the displacement reference vector and the inertial navigation positioning data, so as to obtain the corrected vehicle position at the current time.

2. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 1, characterized in that, The data acquisition module determines the positioning accuracy of the satellite positioning data based on a weighted sum of the ratio of the number of available satellites in the satellite positioning data to the preset number of available satellites and the ratio of the signal quality of the satellite positioning data to the preset signal quality.

3. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 1, characterized in that, The positioning module determines whether to use satellite positioning data as the vehicle's current position and record that moment as a reliable positioning moment, based on whether the positioning accuracy of the satellite positioning data meets a preset positioning accuracy requirement, or to use inertial navigation positioning data as the vehicle's current position. If the positioning accuracy of the satellite positioning data is greater than the preset positioning accuracy, it is determined that the positioning accuracy of the satellite positioning data meets the preset positioning accuracy requirement. The positioning module uses the satellite positioning data as the current position of the vehicle and records the time as the reliable positioning time. If the positioning accuracy of the satellite positioning data is less than or equal to the preset positioning accuracy, it is determined that the positioning accuracy of the satellite positioning data does not meet the preset positioning accuracy requirement, and the positioning module uses inertial navigation positioning data as the vehicle's current position.

4. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 3, characterized in that, The data acquisition module determines the signal quality of the satellite positioning data based on at least one of the signal-to-noise ratio of the satellite signal, the multipath effect index, and the carrier phase cycle slip count in the satellite positioning data.

5. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 3, characterized in that, The positioning module uses inertial navigation positioning data as the vehicle's current position, wherein... The positioning module uses the vehicle position corresponding to the last determined reliable positioning time before the positioning accuracy of the satellite positioning data fails to meet the preset positioning accuracy requirement as the integration starting point. The acceleration and angular velocity measurements in the subsequently received inertial navigation positioning data are integrated over time to determine the relative displacement of the vehicle relative to the integration start point from the time of the reliable positioning. The relative displacement is vector-superimposed with the coordinates of the integration starting point to obtain the vehicle's current position when using inertial navigation positioning data.

6. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 1, characterized in that, The displacement vector calculation unit determines the vehicle's displacement reference vector based on the time difference between the reliable positioning time and the current time, and the distance between the vehicle's current position and the vehicle's position in the electronic tag information of the track slab. Using the vehicle's current position at the trusted positioning time as the starting point of the vector and the vehicle's position corresponding to the electronic tag information on the track board at the current time as the ending point of the vector, a total displacement vector is calculated. Divide the magnitude of the total displacement vector by the time difference to obtain an average velocity vector; The average velocity vector is multiplied by the time difference to obtain the vehicle's displacement reference vector.

7. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 1, characterized in that, The trajectory reconstruction unit, based on the displacement reference vector and combined with the inertial navigation positioning data, corrects the vehicle trajectory from the reliable positioning time to the current time, thereby obtaining the corrected vehicle position at the current time. Based on the inertial navigation positioning data from the trusted positioning time to the current time, extract the displacement increment sequence that characterizes the displacement change of the vehicle within a continuous time interval; Starting from the vehicle position at the reliable positioning time, the displacement increment sequence is accumulated to obtain the inertial navigation calculated trajectory; Determine the difference vector between the displacement reference vector and the total displacement vector of the inertial navigation calculated trajectory; The difference vector is allocated and superimposed on each displacement increment of the inertial navigation calculated trajectory according to a preset ratio to generate a smoothed and corrected continuous trajectory. The endpoint of the continuous trajectory is taken as the corrected vehicle position at the current moment.

8. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 7, characterized in that, The displacement vector calculation unit extracts a sequence of displacement increments characterizing the vehicle's displacement changes over continuous time intervals, based on the inertial navigation positioning data from the reliable positioning time to the current time. Obtain acceleration and angular velocity measurements at consecutive timestamps from inertial navigation and positioning data; By integrating the acceleration and angular velocity measurements over time, the three-dimensional displacement change of the vehicle between adjacent time points is obtained. All the obtained three-dimensional displacement changes are arranged in chronological order to form the displacement increment sequence.

9. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 7, characterized in that, The trajectory reconstruction unit distributes and superimposes the difference vector according to a preset ratio onto each displacement increment of the inertial navigation calculated trajectory, generating a smoothed and corrected continuous trajectory, wherein... Obtain the complete time interval from the trusted positioning time to the current time, and the time corresponding to each displacement increment in the displacement increment sequence; Based on the relative position of the time corresponding to each displacement increment within the complete time interval, determine the linear allocation weight coefficient corresponding to each displacement increment; Multiply the difference vector by the linear weighting coefficient corresponding to each displacement increment to obtain the correction vector assigned to each displacement increment; Each displacement increment is superimposed with its corresponding correction subvector to form a corrected displacement increment. All corrected displacement increments are then accumulated in chronological order to generate a smoothed, corrected continuous trajectory.

10. The railway vehicle precise positioning system based on track slab electronic tags and satellite positioning according to claim 1, characterized in that, The tag coordinate acquisition module determines the geographical coordinates and corresponding time of the railway vehicle based on the electronic tag information on the track slab. The tag coordinate acquisition module reads the electronic tag embedded in the track slab, parses the unique tag identification code stored in the electronic tag, and queries the geographic coordinates corresponding to the unique tag identification code stored in the electronic tag according to the preset mapping relationship database between tag identification codes and geographic coordinates, or directly uses only the geographic coordinates stored in the electronic tag; at the same time, it records the timestamp when the electronic tag is read, and associates the geographic coordinates with the timestamp for output.

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