Multi-algorithm cooperative positioning method for Beidou single-mode terminal of railway locomotive

Abstract

The invention provides a multi-algorithm cooperative positioning method for a Beidou single-mode terminal of a railway locomotive, which belongs to the technical field of railway communication and positioning, and comprises the following steps: firstly, receiving a positioning signal flow which is sent by a Beidou satellite and contains a propagation path identifier, and carrying out shunt processing on a satellite signal unit; a direct signal is imported into a basic positioning algorithm module, a reflected signal is imported into an auxiliary positioning algorithm module, an initial positioning result and path correction information are obtained, then the initial positioning result and the path correction information are subjected to correlation verification, intermediate positioning data are generated, the intermediate positioning data are subjected to constraint adaptation based on railway line track feature information, and a constraint positioning result is obtained. Finally, the signal processing priority of the algorithm module is dynamically adjusted according to the constraint positioning result, final positioning information is generated and sent to a locomotive monitoring terminal, and therefore the accuracy and reliability of railway locomotive positioning can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of railway communication and positioning technology, in particular to a multi-algorithm cooperative positioning method for a railway locomotive Beidou single-mode terminal. BACKGROUND

[0002] In the field of railway transportation, accurate locomotive positioning is a key factor for ensuring train safety, improving transportation efficiency, and realizing intelligent dispatching management. Currently, railway locomotive positioning mainly relies on the Global Navigation Satellite System (GNSS), among which the Beidou satellite navigation system has been widely used in the railway industry due to its advantages of self-control and high precision.

[0003] However, the existing railway locomotive Beidou positioning technology faces many challenges in practical application. On the one hand, the railway operating environment is complex, and during the operation of the locomotive, the Beidou satellite signal is easily blocked and reflected by the surrounding topography, buildings, and the structure of the locomotive itself, resulting in a large amount of reflected signals in the received signal. These reflected signals interfere with the direct signal, making it difficult for traditional single positioning algorithms to accurately analyze the real position of the locomotive, resulting in positioning errors and affecting train safety. On the other hand, the existing positioning methods mostly use fixed algorithm modes, which cannot dynamically adjust algorithm strategies according to different signal environments and positioning needs. In the face of complex and variable railway operating scenarios, the fixed algorithm mode cannot fully utilize the advantages of different algorithms, resulting in poor positioning accuracy and stability. In addition, railway lines have specific track characteristics, such as the direction and radius of curvature of the track, but the existing positioning methods do not fully consider these track characteristic information when generating positioning results, which may result in positioning results that exceed the actual range of the track, further reducing the accuracy and reliability of the positioning. SUMMARY

[0004] In view of the above-mentioned problems, in combination with the first aspect of the present application, the embodiments of the present application provide a multi-algorithm cooperative positioning method for a railway locomotive Beidou single-mode terminal, which comprises: receiving a positioning signal stream sent by a Beidou satellite, the positioning signal stream containing multiple groups of satellite signal units with propagation path identifiers, the propagation path identifiers being used to distinguish between direct signals and reflected signals; performing shunt processing on the satellite signal units, directing direct signal units into a basic positioning algorithm module and reflected signal units into an auxiliary positioning algorithm module according to the propagation path identifiers, to obtain an initial positioning result output by the basic positioning algorithm module and path correction information output by the auxiliary positioning algorithm module; performing correlation verification processing on the initial positioning result and the path correction information, correcting the position offset in the initial positioning result through the propagation time difference of the reflected signal units, and generating intermediate positioning data; Constraining and adapting the intermediate positioning data based on preset track feature information of the railway line, eliminating abnormal positioning points beyond the limited range of the track feature information, and obtaining a constrained positioning result; According to the constrained positioning result, dynamically adjusting the signal processing priority of the basic positioning algorithm module and the auxiliary positioning algorithm module, generating final positioning information, and sending the final positioning information to the locomotive monitoring terminal.

[0005] In another aspect, the embodiment of the present application also provides a multi-algorithm cooperative positioning system of a railway locomotive Beidou single-mode terminal, which comprises a processor and a machine-readable storage medium.

[0006] Based on the above aspects, the embodiment of the present application can clearly distinguish direct signals and reflected signals by receiving a Beidou satellite positioning signal stream containing a propagation path identifier, and can perform branch processing on the satellite signal unit, guide the direct signals into the basic positioning algorithm module, and guide the reflected signals into the auxiliary positioning algorithm module. The advantages of different algorithms in processing different types of signals are fully utilized. The basic positioning algorithm module outputs an initial positioning result, and the auxiliary positioning algorithm module outputs path correction information, thereby realizing targeted processing of signals. The initial positioning result and the path correction information are associated and checked, the position offset in the initial positioning result is corrected by using the propagation time difference of the reflected signal unit, the positioning error caused by the reflected signal interference is effectively reduced, more accurate intermediate positioning data is generated, the intermediate positioning data is constrained and adapted based on the preset track feature information of the railway line, the abnormal positioning points beyond the limited range of the track feature information are eliminated, the fitting degree of the positioning result and the actual track of the railway is further improved, the reliability of positioning is ensured, and finally the signal processing priority of the basic positioning algorithm module and the auxiliary positioning algorithm module is dynamically adjusted according to the constrained positioning result. The positioning system can adaptively optimize the algorithm strategy according to the actual signal environment and the positioning effect, and the final positioning information generated and sent to the locomotive monitoring terminal has higher precision and stability. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is an execution flow diagram of the multi-algorithm cooperative positioning method of the railway locomotive Beidou single-mode terminal provided by the embodiment of the present application.

[0008] Figure 2 is a schematic diagram of exemplary hardware and software components of the multi-algorithm cooperative positioning system of the railway locomotive Beidou single-mode terminal provided by the embodiment of the present application. DETAILED DESCRIPTION

[0009] The application will be described in detail below with reference to the accompanying drawings, Figure 1 is a flowchart of a multi-algorithm cooperative positioning method of a Beidou single-mode terminal of a railway locomotive provided by an embodiment of the application, and the multi-algorithm cooperative positioning method of the Beidou single-mode terminal of the railway locomotive will be described in detail below.

[0010] In step S110, a positioning signal stream transmitted by a Beidou satellite is received, and the positioning signal stream contains a plurality of satellite signal units with propagation path identifiers, which are used to distinguish direct signals from reflected signals.

[0011] This embodiment takes the running process of a railway locomotive on a certain complex mountainous railway section as an example to describe the multi-algorithm cooperative positioning method of the Beidou single-mode terminal of the railway locomotive in detail. In this scenario, the locomotive needs to rely on the Beidou single-mode terminal to obtain accurate positioning information in real time to ensure train operation safety and scheduling efficiency. As a core device for receiving and processing Beidou satellite signals, the primary task of the Beidou single-mode terminal is to receive the positioning signal stream transmitted by the Beidou satellite.

[0012] Due to the complex terrain of the mountainous area, there are various topographies such as mountains, tunnels, and bridges, and the signals transmitted by the Beidou satellite will have different propagation paths during propagation. Part of the signals can directly reach the Beidou single-mode terminal of the locomotive, which are direct signals; and another part of the signals will be reflected by mountains, buildings, etc. before reaching the terminal, which are reflected signals. In order to distinguish and process these two types of signals subsequently, the satellite signal unit contains a propagation path identifier, by which it can be determined whether the signal is a direct signal or a reflected signal.

[0013] In step S111, the signal receiving channel of the Beidou single-mode terminal is opened, and the radio frequency signals transmitted by the Beidou satellite constellation are captured, and the radio frequency signals are converted into digital signal units.

[0014] When working, the Beidou single-mode terminal first needs to open its signal receiving channel. The signal receiving channel is specially designed for receiving the radio frequency signals transmitted by the Beidou satellite constellation, has specific frequency response and bandwidth characteristics, and can accurately capture the radio frequency signals transmitted by the Beidou satellite.

[0015] When the radio frequency signals are captured by the signal receiving channel, the radio frequency front-end module inside the terminal will process them. The radio frequency front-end module contains components such as low-noise amplifiers and mixers, the low-noise amplifiers will amplify the weak radio frequency signals to improve the signal-to-noise ratio of the signals, and the mixers will convert the radio frequency signals into intermediate frequency signals for subsequent processing.

[0016] Subsequently, the intermediate frequency signal is sent to an analog-to-digital converter, which samples the intermediate frequency signal at a set sampling frequency to convert the analog intermediate frequency signal into a digital signal unit. The converted digital signal unit retains the information in the original radio frequency signal, including the pseudo code sequence and the navigation message, but in a digital form, which is more suitable for transmission and processing in a digital circuit.

[0017] In step S112, the carrier stripping processing is performed on the digital signal unit to extract the pseudo code sequence and the navigation message information, and the pseudo code sequence contains the satellite identification code and the propagation path identification field.

[0018] The digital signal unit contains a carrier signal, which is a carrier of information, and the pseudo code sequence and the navigation message information are modulated on the carrier signal. Therefore, carrier stripping processing is needed to extract the pseudo code sequence and the navigation message information.

[0019] The carrier stripping processing is realized through a carrier tracking loop, which includes a carrier phase detector, a loop filter, a numerically controlled oscillator, and the like. The carrier phase detector compares the input digital signal unit with a local carrier signal generated by the numerically controlled oscillator to obtain a phase error signal. The loop filter filters the phase error signal to remove high-frequency components and noise. The filtered error signal controls the numerically controlled oscillator to adjust the frequency and phase of the local carrier signal, so that the local carrier signal is synchronized with the carrier signal in the input digital signal unit.

[0020] When the local carrier signal is synchronized with the carrier signal in the input signal, the carrier stripping is realized through correlation operation, and at this time the pseudo code sequence and the navigation message information can be extracted from the digital signal unit. The pseudo code sequence is a coding sequence with good autocorrelation and cross-correlation, and the satellite identification code is contained in the pseudo code sequence. Different satellites correspond to different pseudo code sequences, and the satellite sending the signal can be determined by identifying the pseudo code sequence. Meanwhile, the pseudo code sequence also contains a propagation path identification field, which is used to identify whether the signal propagation path is direct or reflected.

[0021] In step S113, the ephemeris data in the navigation message information is parsed to determine the orbit plane and the satellite number of the satellite sending the signal, and the corresponding relationship between the satellite signal unit and the satellite orbit plane is established.

[0022] The navigation message information is the data sent by the Beidou satellite to the user about the satellite's own state, time system, and orbit parameters. The ephemeris data describes the position and motion state of the satellite in space in detail. When parsing the ephemeris data, the format specification of the Beidou navigation message should be followed.

[0023] The ephemeris data contains the orbit parameters of the satellite, such as semi-major axis, eccentricity, and argument of perigee. Through these orbit parameters, the spatial position of the satellite at different times can be calculated. At the same time, the ephemeris data also contains the orbit plane information of the satellite and the satellite number. The orbit plane refers to the orbit plane in which the satellite runs, and different orbit planes have different orbit inclination parameters.

[0024] After determining the orbit plane and satellite number to which the satellite belongs, the correspondence between the satellite signal unit and the satellite orbit plane can be established. That is, each satellite signal unit corresponds to a specific satellite on a specific orbit plane, so that in subsequent processing, the satellite signal unit can be traced back to the satellite from which it originates and the orbit plane in which it is located.

[0025] Step S114, according to the propagation path identification field in the pseudo code sequence, the digital signal unit is marked as a direct signal unit or a reflected signal unit, wherein the propagation path identification field of the direct signal unit is a preset first identification value, and the propagation path identification field of the reflected signal unit is a preset second identification value.

[0026] The propagation path identification field in the pseudo code sequence is the key to distinguishing the signal propagation path. In the Beidou satellite system, two identification values are pre-set to represent direct signals and reflected signals, namely the first identification value and the second identification value.

[0027] When the propagation path identification field in the pseudo code sequence is parsed, the value of the field is compared with the preset first identification value and the second identification value. If the value of the field is consistent with the first identification value, it means that the digital signal unit comes through a direct path, and it is marked as a direct signal unit; if the value of the field is consistent with the second identification value, it means that the digital signal unit is propagated after reflection, and it is marked as a reflected signal unit.

[0028] Through the above marking method, the signal units of different propagation paths can be clearly distinguished, and they are prepared for subsequent introduction into different algorithm modules for processing.

[0029] Step S115, the marked direct signal unit and reflected signal unit are combined in the order of receiving time to form a positioning signal stream containing a propagation path identification, and the time interval between adjacent signal units in the positioning signal stream is consistent with the transmission period of the satellite signal.

[0030] After the digital signal unit is marked, it needs to be combined in the order of receiving time by the Beidou single-mode terminal. The receiving time can be recorded by the internal clock module of the terminal, and each signal unit corresponds to a unique receiving time point.

[0031] These marked signal units are arranged in order of reception time from earliest to latest, forming a continuous signal sequence, known as the positioning signal stream. Because Beidou satellites transmit signals at a set period, the time interval between adjacent signal units in the positioning signal stream is consistent with the satellite signal transmission period.

[0032] The positioning signal stream formed in this way not only contains the propagation path identification information of the signal unit, but also maintains the time sequence of signal reception, which facilitates subsequent branch processing and positioning calculation.

[0033] In step S120, the satellite signal units are branched, and the direct signal units are imported into the basic positioning algorithm module according to the propagation path identifier, and the reflected signal units are imported into the auxiliary positioning algorithm module to obtain the initial positioning result output by the basic positioning algorithm module and the path correction information output by the auxiliary positioning algorithm module.

[0034] After obtaining the positioning signal stream containing the propagation path identifier, the satellite signal units in it need to be split. The purpose of splitting is to import the signal units of different propagation paths into the corresponding algorithm modules for processing, so as to fully utilize the characteristics of different signals for positioning calculation.

[0035] For each satellite signal unit in the positioning signal stream, its propagation path identifier is used to determine whether it is a direct signal unit or a reflected signal unit. If it is a direct signal unit, it is imported into the basic positioning algorithm module; if it is a reflected signal unit, it is imported into the auxiliary positioning algorithm module.

[0036] The basic positioning algorithm module mainly uses the direct signal unit to perform positioning calculations and outputs the initial positioning results; the auxiliary positioning algorithm module analyzes and processes the reflected signal unit and outputs path correction information, which is used to correct the initial positioning results and improve positioning accuracy.

[0037] Step S121: construct a signal branch switching module, wherein the signal branch switching module includes a first signal channel connected to the basic positioning algorithm module and a second signal channel connected to the auxiliary positioning algorithm module.

[0038] The signal branch switching module is the core component for realizing satellite signal unit branch processing, and contains two independent signal channels, namely the first signal channel and the second signal channel.

[0039] One end of the first signal channel is connected to the input end of the signal branch switching module, and the other end is connected to the basic positioning algorithm module, which is specifically used to transmit the direct signal unit; the second signal channel also has one end connected to the input end of the signal branch switching module, and the other end connected to the auxiliary positioning algorithm module, which is used to transmit the reflected signal unit.

[0040] The signal branching switch module further comprises a control logic circuit, which can control the flow direction of the signals according to the propagation path identification of the satellite signal units. When a satellite signal unit is received, the control logic circuit reads the propagation path identification of the satellite signal unit, and then controls the corresponding channel switch to open, so that the satellite signal unit can be transmitted to the target algorithm module through the corresponding channel.

[0041] In step S122, the signal branching switch module reads the propagation path identification of the satellite signal unit, and when the first identification value is identified, the corresponding direct signal unit is introduced into the first signal channel, and when the second identification value is identified, the corresponding reflected signal unit is introduced into the second signal channel.

[0042] When working, the signal branching switch module can process the input satellite signal units one by one. For each satellite signal unit, the signal branching switch module first reads the value of the propagation path identification field.

[0043] When the read identification value is the first identification value, the control logic circuit in the signal branching switch module triggers the closing of the first signal channel switch, while keeping the second signal channel switch open, so that the direct signal unit can be successfully transmitted to the basic positioning algorithm module through the first signal channel.

[0044] When the read identification value is the second identification value, the control logic circuit triggers the closing of the second signal channel switch and the opening of the first signal channel switch, and the reflected signal unit is transmitted to the auxiliary positioning algorithm module through the second signal channel.

[0045] In the above manner, the accurate branching of direct signal units and reflected signal units is realized, ensuring that different types of signals can be processed by corresponding algorithm modules.

[0046] In step S123, the basic positioning algorithm module receives the direct signal units transmitted by the first signal channel, extracts the propagation time parameter and carrier phase parameter in the direct signal units, and calculates the three-dimensional coordinate data of the computer vehicle based on the preset single-point positioning model as the initial positioning result.

[0047] After the basic positioning algorithm module receives the direct signal units transmitted by the first signal channel, it first needs to extract the key parameters for positioning calculation, i.e. the propagation time parameter and the carrier phase parameter, from these signal units.

[0048] The propagation time parameter refers to the time experienced by a signal from being transmitted by a satellite to being received by a BeiDou single-mode terminal of a locomotive. When the propagation time parameter is extracted, the time difference between the arrival time of a pseudo-code sequence and the time at which the satellite transmits the pseudo-code sequence is measured to obtain the propagation time parameter. Because the pseudo-code sequence has accurate time synchronization characteristics, the arrival time of the pseudo-code sequence can be determined through correlation operation, and the propagation time parameter can be calculated in combination with the time at which the satellite transmits the pseudo-code sequence.

[0049] The carrier phase parameter refers to the phase difference between a received carrier signal and a local reference carrier signal. The phase change of the carrier signal can be continuously tracked through a carrier tracking loop, so that a carrier phase observation value, i.e., the carrier phase parameter, is obtained.

[0050] After the propagation time parameter and the carrier phase parameter are extracted, the basic positioning algorithm module calculates based on a preset single-point positioning model. The single-point positioning model is a model for positioning by using a single receiver to receive satellite signals. The basic principle is to measure the distances from the receiver to multiple satellites, establish a distance equation, and then solve the equation to obtain the three-dimensional coordinates of the receiver.

[0051] In this embodiment, the pseudo-distances from the locomotive to the satellites are calculated by using the extracted propagation time parameter, and the pseudo-distance observation equation is established in combination with the position information of the satellites (obtained from navigation messages). The pseudo-distance observation equation is optimized in combination with the carrier phase parameter, the equation is solved through a corresponding algorithm, and the longitude, latitude and elevation data of the locomotive are obtained, which together constitute the initial positioning result.

[0052] In step S1231, the basic positioning algorithm module performs pseudo-distance measurement processing on the received direct signal unit, calculates the pseudo-distance value from the satellite to the locomotive as the propagation time parameter according to the time difference between the arrival time of the pseudo-code sequence and the transmission time.

[0053] When the basic positioning algorithm module processes the received direct signal unit, the pseudo-distance measurement processing is performed first. The basis of the pseudo-distance measurement is the time difference calculation of the pseudo-code sequence.

[0054] For each direct signal unit, a pseudo-code sequence is extracted therefrom. The BeiDou single-mode terminal generates a local pseudo-code sequence that is the same as the pseudo-code sequence transmitted by the satellite. By performing correlation operation on the received pseudo-code sequence and the local pseudo-code sequence, the time at which the correlation between the two is the strongest is found, and this time is the arrival time of the pseudo-code sequence.

[0055] At the same time, the transmission time of the pseudo-code sequence can be obtained from the navigation message information. The difference between the arrival time and the transmission time is calculated to obtain the propagation time of the signal. Since the propagation speed of the signal in the vacuum is known (close to the speed of light), multiplying the propagation time by the propagation speed can obtain the distance from the satellite to the train. However, due to the satellite clock error, the receiver clock error, the ionospheric delay, and other error factors, the distance is not the true geometric distance, so it is called the pseudo-range value, which is the propagation time parameter.

[0056] In step S1232, phase measurement is performed on the carrier signal of the direct signal unit to obtain a carrier phase observation value. By comparing the carrier phase observation value with the pseudo-range value, the influence of the ionospheric delay error on the propagation time parameter is eliminated.

[0057] At the same time of the pseudo-range measurement, the basic positioning algorithm module performs phase measurement on the carrier signal of the direct signal unit. The phase measurement of the carrier signal is realized through a carrier tracking loop. As described in step S112, when the local carrier signal is synchronized with the received carrier signal, the phase difference between them can be obtained, which is the carrier phase observation value.

[0058] The carrier phase observation value has high accuracy, but it is a relative value and has the problem of integer ambiguity. By comparing the carrier phase observation value with the pseudo-range value, the different response characteristics of the two to the ionospheric delay error can be used to eliminate the influence of the ionospheric delay error on the propagation time parameter.

[0059] The ionospheric delay error has similar influence on the pseudo-range value and the carrier phase observation value, but the signs are opposite. By setting a combination mode, such as combining the pseudo-range value and the carrier phase observation value in a certain proportion, the influence of the ionospheric delay error can be offset, thereby obtaining a more accurate propagation time parameter.

[0060] In step S1233, the satellite position parameters in the navigation message information are read, and the propagation time parameter is combined to construct a pseudo-range observation equation, which includes satellite coordinates, train coordinates, and clock error parameters.

[0061] The navigation message information contains the position parameters of the satellite, which describe the three-dimensional coordinates of the satellite in space. The basic positioning algorithm module reads these satellite position parameters, including the longitude, latitude, and altitude of the satellite.

[0062] Combined with the previously obtained propagation time parameter (pseudo-range value), a pseudo-range observation equation can be constructed. The basic form of the pseudo-range observation equation is: the pseudo-range value from the satellite to the train is equal to the geometric distance between the satellite coordinates and the train coordinates plus various error terms, in which the main error terms include clock error parameters such as satellite clock error and receiver clock error.

[0063] Specifically, for each satellite, the pseudo-range observation equation can be expressed as: the pseudo-range value is equal to the spatial distance between the satellite and the vehicle plus the distance deviation caused by the satellite clock error, the distance deviation caused by the receiver clock error, and other residual errors. In this way, for multiple satellites, multiple pseudo-range observation equations can be established to form an equation set.

[0064] In step S1234, the least squares method is used to solve the pseudo-range observation equation to obtain the longitude, latitude and elevation data of the vehicle to form a three-dimensional coordinate data.

[0065] The pseudo-range observation equation set is a nonlinear equation set containing multiple unknowns, including the longitude, latitude, elevation of the vehicle, and the receiver clock error. The least squares method is a commonly used method for solving such equation sets.

[0066] The basic idea of the least squares method is to adjust the values of the unknowns so that the sum of the squared deviations between the observed values and the calculated values is minimized. In the solving process, the nonlinear pseudo-range observation equation needs to be linearized first, and through Taylor series expansion, it is approximated as a linear equation.

[0067] Then, according to the linearized equation set, the normal equation is constructed, and the correction number of the unknowns is obtained by solving the normal equation. After multiple iterations, until the size of the correction number meets the preset accuracy requirement, the value of the unknowns obtained at this time is the longitude, latitude, and elevation data of the vehicle, as well as the receiver clock error and other parameters. Among them, the longitude, latitude, and elevation data together form the three-dimensional coordinate data of the vehicle.

[0068] In step S1235, the sliding window smoothing processing is performed on the continuous multiple sets of three-dimensional coordinate data to eliminate the jumping coordinate points caused by signal mutations, and the continuous initial positioning result is generated.

[0069] Due to the interference of external environment to the satellite signal, such as instantaneous electromagnetic interference and signal shielding, etc., the calculated three-dimensional coordinate data may have mutations, i.e., jumping coordinate points. These jumping coordinate points will affect the continuity and accuracy of the positioning result, and therefore need to be smoothed.

[0070] The sliding window smoothing processing is a commonly used time series data processing method. In this embodiment, a fixed size sliding window is set, and the window contains continuous multiple sets of three-dimensional coordinate data. For each window, the average value of all three-dimensional coordinate data in the window is calculated, and the average value is taken as the positioning data at the center time of the window.

[0071] When the window slides along the time axis, the average value in the new window is calculated continuously, and a series of smoothed coordinate data is obtained. During the calculation process, by comparing the deviation of each coordinate point in the window from the average value, if the deviation of a certain coordinate point exceeds the preset threshold, it is judged that the coordinate point is a jump coordinate point, which is excluded from the window, and the average value in the window is recalculated.

[0072] Through the above sliding window smoothing processing, the jump coordinate points can be excluded, and a continuous and smooth three-dimensional coordinate data sequence is obtained, which is the initial positioning result.

[0073] Step S124, receiving the reflected signal unit transmitted by the second signal channel by the auxiliary positioning algorithm module, analyzing the propagation path characteristics of the reflected signal unit, and determining the position information of the terrain reflection point passed by the reflected signal.

[0074] After the auxiliary positioning algorithm module receives the reflected signal unit transmitted by the second signal channel, it needs to analyze the propagation path characteristics thereof. The propagation path of the reflected signal is different from that of the direct signal, as it has been reflected by the terrain surface, and thus the propagation path characteristics thereof contain information of the reflection point.

[0075] The propagation path characteristics can be described by the parameters such as the angle of arrival, propagation time, and signal strength of the reflected signal. By analyzing these parameters, the propagation trajectory of the reflected signal can be inferred, and thus the position information of the terrain reflection point passed by the reflected signal can be determined.

[0076] The terrain reflection point refers to the point on the terrain surface, such as the top of a mountain, the top of a building, or the edge of a tunnel entrance, at which the reflected signal is reflected during propagation.

[0077] Step S1241, performing signal strength analysis on the reflected signal unit by the auxiliary positioning algorithm module, extracting the amplitude attenuation parameter of the reflected signal, and determining the reflection times passed by the reflected signal according to the amplitude attenuation parameter.

[0078] After receiving the reflected signal unit, the auxiliary positioning algorithm module first analyzes the signal strength of the reflected signal. The signal strength analysis is achieved by detecting the amplitude of the reflected signal unit, which is an important indicator of signal strength. Since the reflected signal is reflected by the terrain surface during propagation, its amplitude will be attenuated, and different reflection times will result in different degrees of amplitude attenuation.

[0079] When extracting the amplitude attenuation parameter of the reflected signal, the amplitude of the reflected signal needs to be compared with the amplitude of the direct signal under the same conditions, and the difference or ratio thereof is calculated as the amplitude attenuation parameter. Generally speaking, the more the reflection times, the greater the energy loss of the signal during propagation, and the greater the value of the amplitude attenuation parameter.

[0080] According to the preset amplitude attenuation threshold range, the number of reflections of the reflected signal can be determined. For example, when the amplitude attenuation parameter is within the first preset threshold range, it is determined that the reflected signal has undergone single reflection; when the amplitude attenuation parameter is within the second preset threshold range, it is determined that the reflected signal has undergone multiple reflections. Through the above-mentioned manner, effective reflected signals can be preliminarily screened out.

[0081] Step S1242, when the number of reflections is single reflection, the terrain feature matching the propagation direction of the reflected signal is matched in combination with the terrain database along the railway, and the terrain feature includes the spatial position parameters of mountains, buildings or track facilities.

[0082] When it is determined that the number of reflections of the reflected signal is single reflection, the reflected signal has higher utilization value, because the propagation path of single reflection is relatively simple, and the position of the terrain reflection point can be accurately inferred. At this time, the auxiliary positioning algorithm module calls the terrain database along the railway.

[0083] The terrain database stores detailed information of various terrain features along the railway, including the spatial position parameters of mountains, buildings, track facilities and the like, which are usually represented in the form of three-dimensional coordinates. The propagation direction of the reflected signal can be determined by the angle of arrival, which refers to the angle between the reflected signal entering the Beidou single-mode terminal and the terminal antenna axis.

[0084] The auxiliary positioning algorithm module searches and matches in the terrain database according to the propagation direction of the reflected signal, and finds out the terrain feature matching the propagation direction. Specifically, it is determined whether the direction indicated by the spatial position parameters of the terrain feature is consistent or close to the propagation direction of the reflected signal, and the terrain feature meeting the condition is selected as the terrain target where the candidate reflection point is located.

[0085] Step S1243, based on the difference between the angle of arrival of the reflected signal and the angle of arrival of the direct signal, the propagation path deflection angle of the reflected signal is calculated, and a reflection path geometric model is constructed in combination with the spatial position parameters of the terrain feature.

[0086] The angle of arrival of the reflected signal and the angle of arrival of the direct signal have a certain difference, and the difference can reflect the deflection degree of the propagation path of the reflected signal. The auxiliary positioning algorithm module calculates the angle difference, and takes it as the propagation path deflection angle of the reflected signal.

[0087] The propagation path deflection angle reflects the deviation degree of the reflected signal relative to the direct signal in the propagation direction, and is an important parameter for constructing the reflection path geometric model. In combination with the spatial position parameters of the terrain feature matched in the foregoing, the possible propagation path range of the reflected signal can be determined.

[0088] The reflection path geometry model is a mathematical model based on geometric principles, which is used to describe the propagation trajectory of the reflected signal from the satellite, through the terrain reflection point, to the BeiDou single-mode terminal of the locomotive. In constructing the model, the satellite position, the possible position range of the terrain reflection point, the locomotive position (initial positioning result), and the propagation path deflection angle are taken into consideration to form a model framework that can reflect the geometric relationship between the parameters.

[0089] In step S1244, the three-dimensional spatial coordinates of the reflection point are determined as the terrain reflection point position information by backtracking the propagation trajectory of the reflected signal from the satellite to the reflection point and then to the locomotive through the reflection path geometry model.

[0090] After the reflection path geometry model is constructed, the auxiliary positioning algorithm module will use the model to backtrace the propagation trajectory of the reflected signal. The backtracking process is based on the geometric relationship between the parameters in the model, and by using the known satellite position, the initial positioning result of the locomotive, and the propagation path deflection angle, the possible range of the reflection point is gradually narrowed down.

[0091] In the backtracking process, the assumed position of the reflection point can be continuously adjusted, and it is calculated whether the propagation trajectory corresponding to the assumed position is consistent with the actual propagation characteristics (such as propagation time, arrival angle, etc.) of the reflected signal. When the deviation between the propagation trajectory corresponding to the assumed position and the actual characteristics is within a preset range, the assumed position is the three-dimensional spatial coordinates of the reflection point, which is determined as the terrain reflection point position information.

[0092] For example, in step S12441, the arrival angle of the reflected signal unit and the arrival angle of the direct signal unit are obtained, the angle difference between the arrival angle of the reflected signal unit and the arrival angle of the direct signal unit is calculated as the path deflection angle, and the propagation time of the reflected signal and the propagation time of the direct signal are extracted, and the time difference between the propagation time of the reflected signal and the propagation time of the direct signal is calculated as the path time delay difference.

[0093] In order to more accurately backtrace, the arrival angles and propagation times of the reflected signal unit and the direct signal unit need to be obtained. The arrival angle can be measured by the antenna array of the BeiDou single-mode terminal. Different directions of incident signals will produce different phase differences on the antenna array, and by analyzing the phase differences, the arrival angle of the signal can be determined.

[0094] The angle difference between the arrival angle of the reflected signal and the arrival angle of the direct signal is calculated, which is the path deflection angle. The larger the path deflection angle, the more the propagation direction of the reflected signal deviates from the propagation direction of the direct signal.

[0095] Meanwhile, the propagation time of the reflected signal and the direct signal is extracted, and the propagation time is acquired in a similar manner as in the pseudo-range measurement in step S1231. The time difference between the two is calculated to obtain the path delay difference. The path delay difference reflects the additional propagation time of the reflected signal compared to the direct signal, and is closely related to the length of the reflection path.

[0096] In step S12442, the path deflection angle and the path delay difference are input into the reflection path geometry model, and the spatial angle formed by the reflection signal propagation path and the direct signal propagation path, and the spatial length difference of the reflection signal propagation path and the direct signal propagation path are derived by the reflection path geometry model.

[0097] The path deflection angle and the path delay difference are input into the reflection path geometry model, and the model will derive according to the geometric relationship. First, the spatial angle between the reflection signal propagation path and the direct signal propagation path is derived according to the path deflection angle. The spatial angle is an angle in three-dimensional space, which can more comprehensively reflect the deviation of the two paths.

[0098] Secondly, according to the path delay difference and the signal propagation speed, the spatial length difference of the reflection signal propagation path and the direct signal propagation path can be calculated. Because the path delay difference multiplied by the signal propagation speed is equal to the length difference of the two paths, this difference is one of the key parameters to determine the position of the reflection point.

[0099] In step S12443, based on the spatial angle and the length difference, combined with the position parameters of the satellite and the three-dimensional coordinate data in the initial positioning result of the locomotive, the spatial direction vector of the reflection signal propagation path and the coordinate range of the starting point and the ending point are determined. The position parameters of the satellite come from the ephemeris data in the navigation message, and the three-dimensional coordinate data in the initial positioning result of the locomotive come from the output of the basic positioning algorithm module.

[0100] After the spatial angle and the length difference are determined, combined with the position parameters of the satellite (obtained from the ephemeris data of the navigation message) and the three-dimensional coordinate data of the initial positioning of the locomotive, the characteristics of the reflection signal propagation path can be further determined. The spatial direction vector is used to describe the direction of the reflection signal propagation path in three-dimensional space, which can be calculated by the spatial angle and the direction of the direct path from the satellite to the locomotive.

[0101] The coordinate range of the starting point and the ending point is determined according to the satellite position and the initial positioning coordinate of the locomotive, combined with the length difference. This range can narrow the search space of the reflection point, and improve the efficiency and accuracy of the subsequent matching.

[0102] Step S12444, call the terrain feature point three-dimensional coordinate data in the railway along the terrain database, match the terrain feature point three-dimensional coordinate data with the spatial direction vector of the reflected signal propagation path, and screen out the candidate terrain feature points located in the coordinate range and consistent with the direction vector. The terrain feature point three-dimensional coordinate data includes the three-dimensional spatial coordinates of mountains, buildings or track facilities.

[0103] The railway along the terrain database stores a large amount of terrain feature point three-dimensional coordinate data, which covers the specific positions of mountains, buildings, track facilities and other terrain targets. The auxiliary positioning algorithm module calls these data and matches them with the spatial direction vector of the reflected signal propagation path.

[0104] In the matching process, first, it is judged whether the terrain feature point is located in the coordinate range determined in the front. For terrain feature points not in the range, they are directly eliminated. Then, it is analyzed whether the spatial position of the remaining terrain feature points is consistent with the spatial direction vector of the reflected signal propagation path, i.e. whether the terrain feature point is located on the possible propagation path of the reflected signal. In this way, the candidate terrain feature points that meet the conditions are screened out.

[0105] Step S12445, calculate the sum of the spatial distances of the candidate terrain feature points to the satellite position and the locomotive position respectively, compare the sum of the distances with the spatial length of the reflected signal propagation path, select the candidate terrain feature point with the smallest difference between the sum of the distances and the spatial length, and determine its three-dimensional coordinates as the terrain reflection point position information. The satellite position is the coordinate corresponding to the position parameter of the satellite, and the locomotive position is the coordinate corresponding to the three-dimensional coordinate data in the initial positioning result of the locomotive.

[0106] For the selected candidate terrain feature points, it is necessary to further accurately determine which point is the actual terrain reflection point. The spatial distance of each candidate terrain feature point to the satellite position and the spatial distance to the locomotive position are calculated, and the sum of the two distances is obtained.

[0107] The spatial length of the reflected signal propagation path can be obtained by adding the spatial length of the direct signal propagation path and the length difference obtained in the front. Compare the distance sum of each candidate terrain feature point with the spatial length of the reflected signal propagation path, and calculate the difference between the two.

[0108] Select the candidate terrain feature point with the smallest difference. This candidate terrain feature point is the terrain reflection point closest to the actual reflection path, and its three-dimensional coordinates are determined as the terrain reflection point position information.

[0109] Step S1245, when the number of reflections is multiple reflections, mark the reflected signal unit as an invalid signal, and generate path correction information containing only invalid identification.

[0110] When the number of reflections of the reflected signal is determined to be multiple reflections, it is difficult to accurately determine the position of the terrain reflection point due to the complex and changeable propagation path of the reflected signal, and positioning correction using the reflected signal can introduce a large error. Therefore, the auxiliary positioning algorithm module will mark the reflected signal unit as an invalid signal.

[0111] At the same time, path correction information is generated, which only contains an invalid identifier, indicating that the reflected signal unit cannot be used for positioning correction. In this way, in the subsequent correlation verification process, the invalid path correction information can be identified to avoid adversely affecting the initial positioning result.

[0112] Step S125, according to the terrain reflection point position information and the propagation path difference of the direct signal, calculate the positioning error compensation value caused by the reflected signal, combine the positioning error compensation value with the reflection point position information to generate the path correction information.

[0113] After determining the terrain reflection point position information, the auxiliary positioning algorithm module will calculate the propagation path difference between the reflected signal and the direct signal. The propagation path difference refers to the difference between the spatial length of the reflected signal propagation path and the spatial length of the direct signal propagation path. The difference can be calculated by the relevant parameters obtained in the previous steps.

[0114] Due to the existence of the propagation path difference, the positioning calculation based on the reflected signal can introduce errors, which need to be corrected by the positioning error compensation value. The calculation of the positioning error compensation value is based on the propagation path difference and the signal propagation speed, and also needs to consider the influence of the position of the terrain reflection point on the error direction, and decompose it into three directions of longitude, latitude and altitude.

[0115] Finally, the calculated positioning error compensation value and the terrain reflection point position information are combined to form complete path correction information, which is used for subsequent correction of the initial positioning result.

[0116] Step S130, correlation verification processing is performed on the initial positioning result and the path correction information, and the position offset in the initial positioning result is corrected by the propagation time difference of the reflected signal unit to generate intermediate positioning data.

[0117] The initial positioning result is calculated based on the direct signal unit, but there may be some errors, and the path correction information contains relevant data for correcting the errors. In order to ensure the effectiveness and accuracy of the correction, the initial positioning result and the path correction information need to be subjected to correlation verification processing.

[0118] The purpose of the correlation verification is to determine whether the path correction information is related to the initial positioning result. Only the path correction information related to the initial positioning result can be used to correct the initial positioning result. After the correlation verification passes, the position offset is calculated using the propagation time difference of the reflection signal unit, and the initial positioning result is corrected to generate intermediate positioning data.

[0119] In step S131, three-dimensional coordinate data in the initial positioning result and positioning error compensation values and terrain reflection point position information in the path correction information are extracted.

[0120] The correlation verification process first needs to extract the three-dimensional coordinate data of the locomotive from the initial positioning result, including longitude, latitude and elevation information. At the same time, the positioning error compensation values and the terrain reflection point position information are extracted from the path correction information. The positioning error compensation values include compensation values in three directions, and the terrain reflection point position information is in the form of three-dimensional coordinates.

[0121] These extracted data are the basis for correlation verification and subsequent correction processing, and ensuring the accuracy and integrity of the data is crucial to the entire processing process.

[0122] In step S132, the spatial distance between the initial positioning result and the terrain reflection point position information is calculated. When the spatial distance is less than a predetermined correlation threshold, it is determined that the initial positioning result and the path correction information have a correlation relationship.

[0123] The spatial distance between the three-dimensional coordinate data in the initial positioning result and the terrain reflection point position information is calculated. The calculation of the spatial distance uses the calculation method of the distance between two points in three-dimensional space, that is, the difference between the longitude, latitude and elevation is calculated through the corresponding geometric formula.

[0124] The predetermined correlation threshold is an empirical value set according to the accuracy requirements of the railway locomotive positioning and the actual terrain environment. When the calculated spatial distance is less than the correlation threshold, it means that the terrain reflection point is located within a reasonable range near the locomotive, and the path correction information is related to the initial positioning result and can be used for correction.

[0125] In step S133, when there is a correlation relationship, the positioning error compensation values are decomposed into longitude direction compensation, latitude direction compensation and elevation direction compensation.

[0126] When it is determined that the initial positioning result and the path correction information have a correlation relationship, the positioning error compensation values need to be decomposed. The positioning error compensation values are a comprehensive compensation value, which needs to be decomposed according to the longitude, latitude and elevation in three directions to obtain the specific compensation value in each direction.

[0127] The decomposition process is based on the relative positional relationship between the position of the terrain reflection point and the initial positioning position of the locomotive, ensuring that the compensation amount in each direction accurately reflects the positioning error in that direction.

[0128] In step S134, the longitude data in the initial positioning result is superimposed with the longitude direction compensation amount, the latitude data is superimposed with the latitude direction compensation amount, and the elevation data is superimposed with the elevation direction compensation amount to obtain the corrected coordinate data.

[0129] After obtaining the compensation amounts in the three directions, the longitude data in the initial positioning result is added to the longitude direction compensation amount, the latitude data is added to the latitude direction compensation amount, and the elevation data is added to the elevation direction compensation amount. Through the above superimposition processing, the error in the initial positioning result is corrected to obtain the corrected coordinate data.

[0130] The corrected coordinate data has higher accuracy than the initial positioning result and better reflects the actual position of the locomotive.

[0131] In step S135, when the spatial distance is greater than or equal to the association threshold, it is determined that the path correction information is invalid, and the initial positioning result is directly used as the intermediate positioning data. At the same time, the number of invalid path correction information and the corresponding reflection signal unit identifier are recorded.

[0132] When the spatial distance between the calculated initial positioning result and the terrain reflection point position information is greater than or equal to the association threshold, it indicates that the path correction information is not related to the initial positioning result, and using this path correction information for correction may result in a larger deviation in the positioning result. Therefore, it is determined that the path correction information is invalid.

[0133] At this time, the initial positioning result is directly used as the intermediate positioning data. At the same time, the number of invalid path correction information and the corresponding reflection signal unit identifier are recorded for subsequent analysis and evaluation of signal reception and processing.

[0134] In step S140, the intermediate positioning data is constrained and adapted based on the preset track feature information of the railway line to eliminate abnormal positioning points that exceed the limit range of the track feature information, and a constrained positioning result is obtained.

[0135] Although the intermediate positioning data has been corrected, it may still contain some abnormal positioning points that do not conform to the actual railway line conditions, which may be caused by signal interference, complex reflection path, etc. In order to further improve the reliability of the positioning result, it is necessary to constrain and adapt the intermediate positioning data based on the preset track feature information of the railway line.

[0136] The track feature information defines the possible running range of the locomotive, and by comparing the intermediate positioning data with the track feature information, abnormal positioning points exceeding the defined range are eliminated to obtain a constrained positioning result conforming to the actual track condition.

[0137] In step S141, track feature information in the railway line database is called, and the track feature information includes a three-dimensional coordinate sequence of a line center line, a track width parameter, and a line curve radius parameter.

[0138] The railway line database stores detailed track feature information of the railway line, and the constraint adaptation process first needs to call these information. The track feature information mainly includes a three-dimensional coordinate sequence of a line center line, a track width parameter, and a line curve radius parameter.

[0139] The three-dimensional coordinate sequence of the line center line is composed of a series of three-dimensional coordinate points arranged in order of mileage, reflecting the direction and position of the railway line; the track width parameter refers to the distance between the two rails on the track, used to determine the allowed range of the locomotive in the lateral direction; and the line curve radius parameter describes the degree of curvature of the railway line, including the relevant parameters of straight line segments, circular curve segments, and transition curve segments.

[0140] In step S1411, the Beidou single-mode terminal connects the database server of the railway line through the communication interface, and sends a track feature request instruction containing the current locomotive number.

[0141] The Beidou single-mode terminal establishes a connection with the database server of the railway line through the communication interface (such as an Ethernet interface, a wireless communication module, etc.) equipped. After the connection is established, the terminal generates a track feature request instruction, and the track feature request instruction contains the number of the current locomotive.

[0142] The locomotive number is unique information identifying the identity of the locomotive, and the database server can determine the current possible running railway line segment of the locomotive by identifying the number, thereby providing the corresponding track feature information.

[0143] In step S1412, the track feature data packet returned by the database server is received, the line identification information in the track feature data packet is parsed, and the track feature subset corresponding to the current running line of the locomotive is matched.

[0144] After receiving the track feature request instruction, the database server queries the current running line information of the locomotive according to the locomotive number in the track feature request instruction, and packs the corresponding track feature data into a track feature data packet and returns it to the Beidou single-mode terminal.

[0145] After receiving the track feature data packet, the Beidou single-mode terminal parses the packet and extracts the line identification information in the packet. The line identification information is used to uniquely identify different sections of the railway line. By matching the identification information with the line information stored in the terminal, the track feature subset corresponding to the current running line of the locomotive can be determined.

[0146] In step S1413, a three-dimensional coordinate sequence of the line center line is extracted from the track feature subset. The three-dimensional coordinate sequence is composed of a plurality of coordinate points arranged in ascending order of mileage, and each coordinate point contains a longitude value, a latitude value and an elevation value.

[0147] After determining the corresponding track feature subset, a three-dimensional coordinate sequence of the line center line is extracted from the subset. The coordinate points in the three-dimensional coordinate sequence are arranged in ascending order of the mileage of the railway line, and each coordinate point contains a longitude value, a latitude value and an elevation value, which accurately describes the spatial position of the line center line.

[0148] These coordinate points are important reference for determining whether the intermediate positioning data is within the track range.

[0149] In step S1414, the track width parameter in the track feature subset is extracted. The track width parameter is the distance between the inner sides of the rails on both sides of the track.

[0150] Meanwhile, the track width parameter is extracted from the track feature subset. The track width parameter is a fixed value, which refers to the distance between the inner sides of the rails on both sides of the track, and determines the maximum allowed deviation range of the locomotive relative to the line center line in the lateral direction. In this embodiment, the track width parameter is pre-set according to the design standard of the railway line, and its value is stored in the track feature subset in the form of a clear parameter. When extracting the parameter, the auxiliary positioning algorithm module can locate the field storing the track width parameter according to the parsing rules of the track feature data packet, read the value corresponding to the field, and use it as an important basis for determining whether the intermediate positioning data is within the track range.

[0151] In step S1415, the line curve radius parameter is extracted, which includes a straight line segment identification, a circular curve segment radius value and a transition curve segment parameter for describing the transition characteristics from a straight line segment to a circular curve segment.

[0152] The line curve radius parameter is a key parameter reflecting the direction and bending degree of the railway line, and plays an important role in determining the validity of the intermediate positioning data. When extracting the line curve radius parameter from the track feature subset, the straight line segment identification, the circular curve segment radius value and the transition curve segment parameter contained therein need to be extracted respectively.

[0153] The straight segment identifier is used to identify a straight segment in a railway line, usually represented by a specific code or mark, and when the identifier is detected, it indicates that the current locomotive is running on a straight segment. The circular curve segment radius value represents the degree of curvature of the curve segment, and the smaller the radius value, the more curved the curve; the larger the radius value, the flatter the curve.

[0154] The easement curve segment parameter is used to describe the transition characteristics from the straight segment to the circular curve segment, including the length of the easement curve, the curvature of the starting point and the ending point, and other parameters. Through the above parameters, the change process of the line from the straight line to the curve can be accurately grasped. When extracting these parameters, the auxiliary positioning algorithm module can read them one by one according to the storage format and position of each parameter in the track feature subset, and store them according to the corresponding type for subsequent constraint adaptation processing.

[0155] Step S150, dynamically adjusting the signal processing priority of the basic positioning algorithm module and the auxiliary positioning algorithm module according to the constraint positioning result, generating the final positioning information and sending it to the locomotive monitoring terminal.

[0156] After obtaining the constraint positioning result, the signal processing priority of the basic positioning algorithm module and the auxiliary positioning algorithm module needs to be dynamically adjusted according to the result. This is because in different driving environments and positioning states, the role and accuracy of the two algorithm modules will be different, and by adjusting the priority, the positioning system can always maintain high positioning performance.

[0157] When the constraint positioning result shows high stability and accuracy, it means that the current working state of the basic positioning algorithm module is good, and at this time, the signal processing priority can be appropriately increased, and the processing resource occupation of the auxiliary positioning algorithm module can be reduced; on the contrary, when the stability of the constraint positioning result is poor, the priority of the auxiliary positioning algorithm module needs to be increased, so that it can play a more full role in correcting the initial positioning result.

[0158] After adjusting the priority, the constraint positioning result and the algorithm priority adjustment information are integrated to generate the final positioning information. The final positioning information contains the accurate position of the locomotive, the time mark, and the working state of the algorithm, etc., and then it is sent to the locomotive monitoring terminal through the output interface of the Beidou single-mode terminal.

[0159] Step S151, counting the number of consecutive valid positioning points in the constraint positioning result, and calculating the time interval stability parameter of the valid positioning points.

[0160] First, the consecutive valid positioning points in the constraint positioning result are counted. The consecutive valid positioning points refer to the positioning points that continuously meet the track feature information limited range within a period of time, and the number of which can reflect the stable running time length of the current positioning system.

[0161] Based on the statistical number of valid positioning points, the time interval stability parameter is calculated. This parameter measures the stability of the time intervals between adjacent valid positioning points. During the calculation, the time stamp of each valid positioning point is first extracted, and then the time stamp difference between two adjacent valid positioning points is calculated to obtain multiple time interval values.

[0162] Afterwards, these time interval values ​​are processed, such as calculating their standard deviation or coefficient of variation, to indicate the degree of dispersion of the time interval. The smaller the dispersion, the more stable the time interval and the higher the corresponding time interval stability parameter value; otherwise, it means that the time interval stability is poor.

[0163] Step S1511 traverses the valid positioning points in the constrained positioning result, extracts the time stamp of each valid positioning point, calculates the time stamp difference between two adjacent valid positioning points, and obtains multiple time interval values.

[0164] Traverse all valid positioning points in the constrained positioning result and extract the time stamp of each valid positioning point in chronological order. The time stamp is the reception time corresponding to each positioning point, usually recorded with millisecond or microsecond accuracy.

[0165] For the extracted time stamps, the difference between two adjacent time stamps is calculated in order, that is, the time stamp of the latter valid positioning point minus the time stamp of the previous valid positioning point. The result is the time interval value between the two adjacent valid positioning points.

[0166] Through the above calculation, a series of time interval values ​​can be obtained, which reflect the distribution of valid positioning points in the time dimension.

[0167] Step S1512: sort the time interval values, remove the maximum and minimum values, and calculate the arithmetic mean of the remaining time interval values ​​as the average time interval.

[0168] The obtained multiple time interval values ​​are sorted and arranged in ascending order or descending order. After the sorting is completed, the maximum and minimum values ​​are removed. This is to eliminate the influence of extreme values ​​on the calculation results, so that the average time interval can better reflect the overall time interval level.

[0169] The remaining time intervals are then averaged. This is done by adding the remaining time intervals and dividing them by the number of remaining time intervals. The average time interval reflects the average frequency of valid positioning points per unit time and is an important intermediate variable for calculating the time interval stability parameter.

[0170] Step S1513, calculate the normalized variance value of each time interval value relative to the average time interval as the time interval stability parameter.

[0171] The difference between each time interval value and the average time interval is calculated based on the average time interval, and then the difference is squared to eliminate the influence of positive and negative signs. Then, the arithmetic mean of the squared difference values is calculated to obtain the variance value.

[0172] The variance value is divided by the square of the average time interval to obtain the normalized variance value. The normalized variance value eliminates the influence of the dimension, and can more objectively reflect the dispersion degree of the time interval value relative to the average time interval, so it is used as the time interval stability parameter.

[0173] The smaller the normalized variance value, the more concentrated the time interval value around the average time interval, and the better the time interval stability; otherwise, the worse the time interval stability.

[0174] Step S1514, when the number of valid positioning points is less than the preset statistical threshold, a preset default stability parameter is used as the time interval stability parameter.

[0175] The preset statistical threshold is set according to the performance requirements of the positioning system and the actual application scenario, which represents the minimum number of valid positioning points required for effective statistical analysis. When the number of valid positioning points in the constrained positioning result is less than the statistical threshold, it means that the amount of data available for calculating the time interval stability parameter is insufficient, and if the above method is still used to calculate, the result may have a large error and cannot accurately reflect the actual time interval stability.

[0176] Therefore, in the above case, a preset default stability parameter is used as the time interval stability parameter. The default stability parameter is preset according to a large amount of historical data and experimental results, which can provide a reasonable reference for subsequent priority adjustment when the amount of data is insufficient.

[0177] Step S1515, compare the time interval stability parameter with a preset stability threshold to generate a judgment basis for adjusting the algorithm priority, and the judgment basis includes the stability parameter value and the corresponding priority adjustment direction.

[0178] The preset stability threshold is a critical value for judging whether the time interval stability meets the requirements, which is determined according to the design goals of the positioning system and the actual running experience. The calculated time interval stability parameter is compared with the stability threshold.

[0179] If the time interval stability parameter is higher than the stability threshold, it indicates that the time interval stability of the current effective positioning point is better, and the corresponding judgment basis is to increase the signal processing priority of the basic positioning algorithm module and reduce the signal processing priority of the auxiliary positioning algorithm module; if the time interval stability parameter is lower than or equal to the stability threshold, it indicates that the time interval stability is poor, and the judgment basis is to reduce the priority of the basic positioning algorithm module and increase the priority of the auxiliary positioning algorithm module. The judgment basis includes the stability parameter value and the corresponding priority adjustment direction.

[0180] Step S152, when the time interval stability parameter is higher than the preset stability threshold, the signal processing priority of the basic positioning algorithm module is increased, the signal processing priority of the auxiliary positioning algorithm module is reduced, and the processing frequency of the reflected signal unit is reduced.

[0181] When the time interval stability parameter is higher than the preset stability threshold, it indicates that the current positioning system is in a relatively stable state, and the basic positioning algorithm module can output a more reliable initial positioning result. At this time, increasing the signal processing priority of the basic positioning algorithm module means that more processing time and computing resources are allocated to the basic positioning algorithm module in system resource allocation, so that it can process the direct signal unit more quickly and accurately and output the initial positioning result.

[0182] At the same time, the signal processing priority of the auxiliary positioning algorithm module is reduced, and the processing frequency of the reflected signal unit is reduced. This is because in the stable state, the correction effect of the reflected signal unit on the positioning result is relatively small, and reducing the processing frequency can save system resources and improve the overall processing efficiency. Specifically, the reduction of the processing frequency can be realized by adjusting the bandwidth and processing time proportion of the second signal channel in the signal branching switch module.

[0183] Step S153, when the time interval stability parameter is lower than or equal to the stability threshold, the signal processing priority of the basic positioning algorithm module is reduced, the signal processing priority of the auxiliary positioning algorithm module is increased, and the processing frequency of the reflected signal unit is increased.

[0184] When the time interval stability parameter is lower than or equal to the stability threshold, it indicates that the stability of the current positioning system is poor, and the initial positioning result output by the basic positioning algorithm module may have large errors or fluctuations. At this time, the signal processing priority of the basic positioning algorithm module needs to be reduced to reduce the system resources occupied by it.

[0185] Accordingly, the signal processing priority of the auxiliary positioning algorithm module is improved, and the processing frequency of the reflected signal unit is increased. By processing the reflected signal unit more frequently, the auxiliary positioning algorithm module can more timely analyze the propagation path characteristics of the reflected signal, calculate the positioning error compensation value, and correct the initial positioning result, thereby improving the overall positioning accuracy and stability. The increase in the processing frequency of the reflected signal unit can be achieved by increasing the bandwidth and processing time proportion of the second signal channel.

[0186] In step S154, the channel bandwidth allocation proportion of the signal shunt switching module is reconfigured according to the adjusted priority, and algorithm priority adjustment information is obtained.

[0187] The channel bandwidth allocation proportion of the signal shunt switching module directly affects the signal processing capability of the two algorithm modules. According to the adjusted signal processing priorities of the basic positioning algorithm module and the auxiliary positioning algorithm module, the bandwidth allocation proportions of the first signal channel and the second signal channel are reconfigured.

[0188] When the priority of the basic positioning algorithm module is improved, the bandwidth proportion of the first signal channel is increased, and the bandwidth proportion of the second signal channel is reduced; when the priority of the auxiliary positioning algorithm module is improved, the bandwidth proportion of the second signal channel is increased, and the bandwidth proportion of the first signal channel is reduced.

[0189] The reconfiguration of the above bandwidth allocation proportion is recorded in the form of parameters to form algorithm priority adjustment information. The algorithm priority adjustment information reflects the processing resource allocation of the two algorithm modules and is an important part of the final positioning information.

[0190] In step S155, the constraint positioning result and the algorithm priority adjustment information are combined to generate final positioning information containing positioning coordinates, time markers, and algorithm state identifiers, which are sent to the locomotive monitoring terminal through the output interface of the Beidou single-mode terminal.

[0191] The constraint positioning result contains the locomotive positioning coordinates and corresponding time markers after being constrained by the track feature information, and the algorithm priority adjustment information reflects the priority state of the two algorithm modules. Combining these two parts of information forms the final positioning information.

[0192] In addition to containing positioning coordinates and time markers, the final positioning information also contains algorithm state identifiers, which are used to indicate the current working state and priority of the basic positioning algorithm module and the auxiliary positioning algorithm module. For example, a specific code can be used to indicate that the basic positioning algorithm module is in a high priority state and the auxiliary positioning algorithm module is in a low priority state, or vice versa.

[0193] After the combination is completed, the Beidou single-mode terminal sends the final positioning information to the locomotive monitoring terminal through its output interface. The output interface can be a wired interface (such as an Ethernet interface, an RS485 interface, etc.) or a wireless interface (such as Bluetooth, Wi-Fi, etc.), and the specific interface to be used is determined according to the design of the locomotive monitoring system. After receiving the final positioning information, the locomotive monitoring terminal can display and store it, providing real-time locomotive position information for the locomotive driver and the dispatch center, and ensuring the safety and efficient operation of railway transportation.

[0194] Figure 2 A schematic diagram of exemplary hardware and software components of the railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning system 100 provided by some embodiments of the present application is shown. For example, the processor 120 can be used in the railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning system 100 and used to execute the functions in the present application.

[0195] The railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning system 100 can be a general-purpose server or a special-purpose server, both of which can be used to implement the railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning method of the present application. Although only one server is shown in the present application, for the sake of convenience, the functions described in the present application can be implemented in a distributed manner on multiple similar platforms to balance the processing load.

[0196] For example, the railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning system 100 can include a network port 110 connected to a network, one or more processors 120 for executing program instructions, a communication bus 130, and different forms of storage media 140, such as a disk, a ROM, or a RAM, or any combination thereof. Exemplarily, the railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning system 100 can also include program instructions stored in a ROM, a RAM, or other types of non-transitory storage media, or any combination thereof. The method of the present application can be implemented according to these program instructions. The railway locomotive Beidou single-mode terminal multi-algorithm cooperative positioning system 100 also includes an I / O interface 150 between the computer and other input / output devices.

[0197] For the convenience of description, only one processor is described in the railway locomotive Beidou single mode terminal multi-algorithm cooperative positioning system 100. However, it should be noted that the railway locomotive Beidou single mode terminal multi-algorithm cooperative positioning system 100 in the present application can also include multiple processors, and thus the steps performed by one processor described in the present application can also be jointly performed by multiple processors or individually performed. For example, if the processor of the railway locomotive Beidou single mode terminal multi-algorithm cooperative positioning system 100 performs steps A and B, it should be understood that steps A and B can also be jointly performed by two different processors or individually performed in one processor. For example, a first processor performs step A, a second processor performs step B, or the first processor and the second processor jointly perform steps A and B.

[0198] In addition, the embodiment of the present application further provides a readable storage medium, wherein computer executable instructions are preset, and when a processor executes the computer executable instructions, the railway locomotive Beidou single mode terminal multi-algorithm cooperative positioning method is realized.

[0199] It should be noted that, in order to simplify the description of the present application and help understand one or more embodiments of the present application, in the foregoing description of the embodiments of the present application, various features are sometimes combined into one embodiment, figure or description thereof.

Claims

1. A multi-algorithm collaborative positioning method for a Beidou single-mode terminal on a railway locomotive, characterized in that: The method comprises: Receive a positioning signal stream sent by a Beidou satellite, wherein the positioning signal stream includes multiple groups of satellite signal units with propagation path identifiers, wherein the propagation path identifiers are used to distinguish direct signals from reflected signals; The satellite signal units are split and processed, and the direct signal units are introduced into the basic positioning algorithm module and the reflected signal units are introduced into the auxiliary positioning algorithm module according to the propagation path identifier, so as to obtain the initial positioning result output by the basic positioning algorithm module and the path correction information output by the auxiliary positioning algorithm module; Performing correlation verification processing on the initial positioning result and the path correction information, correcting the position offset in the initial positioning result by the propagation time difference of the reflected signal unit, and generating intermediate positioning data; Based on the preset track feature information of the railway line, the intermediate positioning data is constrained and adapted to eliminate abnormal positioning points that exceed the limited range of the track feature information to obtain the constrained positioning result; The signal processing priorities of the basic positioning algorithm module and the auxiliary positioning algorithm module are dynamically adjusted according to the constraint positioning results, and the final positioning information is generated and sent to the locomotive monitoring terminal.

2. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 1, characterized in that: The receiving of the positioning signal stream sent by the Beidou satellite includes: Open the signal receiving channel of the Beidou single-mode terminal, capture the radio frequency signal sent by the Beidou satellite constellation, and convert the radio frequency signal into a digital signal unit; Carrier stripping is performed on the digital signal unit to extract the pseudo code sequence and navigation message information therein, wherein the pseudo code sequence includes a satellite identification code and a propagation path identification field; Parse the ephemeris data in the navigation message, determine the orbital plane and satellite number of the satellite sending the signal, and establish the correspondence between the satellite signal unit and the satellite orbital plane; Marking the digital signal unit as a direct signal unit or a reflected signal unit according to a propagation path identification field in the pseudocode sequence, wherein the propagation path identification field of the direct signal unit is a preset first identification value, and the propagation path identification field of the reflected signal unit is a preset second identification value; The marked direct signal units and reflected signal units are combined in the order of receiving time to form a positioning signal stream containing a propagation path identifier, and the time interval between adjacent signal units in the positioning signal stream is consistent with the sending period of the satellite signal.

3. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 2, characterized in that: The branching process of the satellite signal unit, importing the direct signal unit into the basic positioning algorithm module according to the propagation path identifier, importing the reflected signal unit into the auxiliary positioning algorithm module, and obtaining the initial positioning result output by the basic positioning algorithm module and the path correction information output by the auxiliary positioning algorithm module, includes: Constructing a signal branch switching module, wherein the signal branch switching module includes a first signal channel connected to the basic positioning algorithm module and a second signal channel connected to the auxiliary positioning algorithm module; The signal branch switching module reads the propagation path identifier of the satellite signal unit, and when a first identifier value is identified, the corresponding direct signal unit is directed to the first signal channel; when a second identifier value is identified, the corresponding reflected signal unit is directed to the second signal channel; Utilizing the basic positioning algorithm module to receive the direct signal unit transmitted by the first signal channel, extracting the propagation time parameter and the carrier phase parameter in the direct signal unit, and calculating the three-dimensional coordinate data of the rover as an initial positioning result based on a preset single-point positioning model; Utilizing the auxiliary positioning algorithm module to receive the reflected signal unit transmitted by the second signal channel, analyzing the propagation path characteristics of the reflected signal unit, and determining the position information of the terrain reflection point through which the reflected signal passes; According to the propagation path difference between the terrain reflection point position information and the direct signal, a positioning error compensation value caused by the reflected signal is calculated, and the positioning error compensation value is combined with the reflection point position information to generate path correction information.

4. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 3, characterized in that: The method of using the basic positioning algorithm module to receive the direct signal unit transmitted by the first signal channel, extracting the propagation time parameter and the carrier phase parameter in the direct signal unit, and calculating the three-dimensional coordinate data of the vehicle as the initial positioning result based on a preset single-point positioning model includes: Perform pseudo-range measurement processing on the received direct signal unit using the basic positioning algorithm module, and calculate the pseudo-range value from the satellite to the locomotive according to the arrival time and sending time difference of the pseudo-code sequence as the propagation time parameter; The phase of the carrier signal of the direct signal unit is measured to obtain the carrier phase observation value. By comparing the carrier phase observation value with the pseudorange value, the influence of the ionospheric delay error on the propagation time parameters is eliminated. Read the satellite position parameters in the navigation message information and construct a pseudo-range observation equation based on the propagation time parameters. The pseudo-range observation equation includes satellite coordinates, locomotive coordinates and clock error parameters. The pseudo-range observation equation is solved using the least squares method to obtain the three-dimensional coordinate data consisting of the longitude, latitude and elevation data of the locomotive; Sliding window smoothing is performed on multiple sets of continuous three-dimensional coordinate data to eliminate jump coordinate points caused by signal mutations and generate continuous initial positioning results.

5. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 3, characterized in that: The method of using the auxiliary positioning algorithm module to receive the reflected signal unit transmitted by the second signal channel, analyzing the propagation path characteristics of the reflected signal unit, and determining the position information of the terrain reflection point through which the reflected signal passes includes: Utilizing the auxiliary positioning algorithm module to perform signal strength analysis on the reflected signal unit, extracting an amplitude attenuation parameter of the reflected signal, and determining the number of reflections of the reflected signal according to the amplitude attenuation parameter; When the number of reflections is a single reflection, the terrain features that are consistent with the propagation direction of the reflected signal are matched in combination with the terrain database along the railway, where the terrain features include spatial position parameters of mountains, buildings or track facilities; Based on the difference between the arrival angle of the reflected signal and the arrival angle of the direct signal, the deflection angle of the propagation path of the reflected signal is calculated, and the reflection path geometric model is constructed in combination with the spatial position parameters of the terrain features; The propagation trajectory of the reflected signal from the satellite to the reflection point and then to the locomotive is inferred through the reflection path geometric model, and the three-dimensional spatial coordinates of the reflection point are determined as the position information of the terrain reflection point; When the number of reflections is multiple reflections, the reflection signal unit is marked as an invalid signal, and path correction information containing only an invalid flag is generated.

6. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 1, characterized in that: The correlating verification process is performed on the initial positioning result and the path correction information, and the position offset in the initial positioning result is corrected by the propagation time difference of the reflected signal unit to generate the intermediate positioning data, including: Extracting the three-dimensional coordinate data in the initial positioning result and the positioning error compensation value and the terrain reflection point position information in the path correction information; Calculating the spatial distance between the initial positioning result and the position information of the terrain reflection point; when the spatial distance is less than a preset correlation threshold, determining that the initial positioning result and the path correction information are correlated; In the case of a correlation relationship, the positioning error compensation value is decomposed into longitude direction compensation, latitude direction compensation and elevation direction compensation; The longitude data in the initial positioning result is superimposed with the longitude compensation amount, the latitude data is superimposed with the latitude compensation amount, and the elevation data is superimposed with the elevation compensation amount to obtain the corrected coordinate data; When the spatial distance is greater than or equal to the association threshold, the path correction information is determined to be invalid, and the initial positioning result is directly used as the intermediate positioning data. At the same time, the number of invalid path correction information and the corresponding reflection signal unit identifier are recorded.

7. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 1, characterized in that: The intermediate positioning data is subjected to constraint adaptation processing based on the preset track characteristic information of the railway line, and abnormal positioning points that exceed the limited range of the track characteristic information are eliminated to obtain the constrained positioning result, including: Calling track feature information from a railway line database, the track feature information including a three-dimensional coordinate sequence of a line centerline, a track width parameter, and a line curve radius parameter; Calculate the vertical distance between the three-dimensional coordinates in the intermediate positioning data and the three-dimensional coordinate sequence of the track centerline to obtain the offline distance value; When the offline distance value is less than or equal to half of the track width parameter, the intermediate positioning data is determined to be a valid positioning point and the three-dimensional coordinate is retained; When the offline distance value is greater than half of the track width parameter, the allowable lateral offset of the current section is calculated according to the line curve radius parameter. If the offline distance value exceeds the allowable lateral offset, it is marked as an abnormal point. Otherwise, it is retained after smoothing correction to obtain a retained valid positioning point. The retained valid positioning points are arranged in time sequence to generate a constrained positioning result containing a time stamp, wherein the time stamp is synchronized with the reception time of the positioning signal stream.

8. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 7, characterized in that: The calling of the track feature information in the railway line database includes: Connect to the railway database server through the communication interface of the Beidou single-mode terminal and send a track feature request instruction containing the current locomotive number; receiving a track feature data packet returned by the database server, parsing the line identification information in the track feature data packet, and matching a track feature subset corresponding to the line currently being run by the locomotive; Extracting a three-dimensional coordinate sequence of a line centerline from the track feature subset, wherein the three-dimensional coordinate sequence is composed of a plurality of coordinate points arranged in ascending order of mileage, each coordinate point including a longitude value, a latitude value, and an elevation value; Extracting a track width parameter from the track feature subset, where the track width parameter is the distance between inner sides of rails on both sides of the track; Extract line curve radius parameters, which include a straight line segment identifier, a circular curve segment radius value, and a transition curve segment parameter. The transition curve segment parameter is used to describe the transition characteristics from the straight line segment to the circular curve segment.

9. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 1, characterized in that: The method of dynamically adjusting the signal processing priorities of the basic positioning algorithm module and the auxiliary positioning algorithm module according to the constraint positioning result, generating final positioning information and sending it to the locomotive monitoring terminal includes: Counting the number of consecutive valid positioning points in the constrained positioning result, and calculating a time interval stability parameter of the valid positioning points; When the time interval stability parameter is higher than the preset stability threshold, the signal processing priority of the basic positioning algorithm module is increased, the signal processing priority of the auxiliary positioning algorithm module is reduced, and the processing frequency of the reflection signal unit is reduced; When the time interval stability parameter is lower than or equal to the stability threshold, the signal processing priority of the basic positioning algorithm module is reduced, the signal processing priority of the auxiliary positioning algorithm module is increased, and the processing frequency of the reflection signal unit is increased; Reconfigure the channel bandwidth allocation ratio of the signal branch switching module according to the adjusted priority to obtain algorithm priority adjustment information; The constrained positioning results are combined with the algorithm priority adjustment information to generate the final positioning information containing the positioning coordinates, time stamp and algorithm status identifier, and sent to the locomotive monitoring terminal through the output interface of the Beidou single-mode terminal.

10. The multi-algorithm collaborative positioning method for a BeiDou single-mode terminal on a railway locomotive according to claim 9, characterized in that: The counting of the number of consecutive valid positioning points in the constrained positioning result and calculating the time interval stability parameter of the valid positioning points includes: Traverse the valid positioning points in the constrained positioning result, extract the time stamp of each valid positioning point, calculate the time stamp difference between two adjacent valid positioning points, and obtain multiple time interval values; Sort the time interval values, remove the maximum and minimum values, and calculate the arithmetic mean of the remaining time interval values ​​as the average time interval; Calculate the normalized variance value of each time interval value relative to the average time interval as the time interval stability parameter; When the number of valid positioning points is less than the preset statistical threshold, the preset default stability parameter is used as the time interval stability parameter; The time interval stability parameter is compared with a preset stability threshold to generate a judgment basis for adjusting the algorithm priority, wherein the judgment basis includes the stability parameter value and the corresponding priority adjustment direction.

Images