CN115166798A - Ambiguity fixing method and device in rail transit scene and train positioning terminal - Google Patents
Ambiguity fixing method and device in rail transit scene and train positioning terminal Download PDFInfo
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- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
- G01S19/44—Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
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- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/50—Determining position whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks
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Abstract
The application provides a method and a device for fixing ambiguity in a rail transit scene and a train positioning terminal, wherein the method comprises the following steps: determining a current reference station replacement threshold interval and an ambiguity fixed threshold interval of the train based on receiving Doppler offsets corresponding to positioning signals sent by base stations distributed on two sides of a train running track and located in an observable range; and determining the current target reference station of the train in each base station positioned in the observable range according to the reference station replacement threshold interval, and fixing the ambiguity by adopting an ambiguity fixing algorithm and an ambiguity fixing threshold interval based on the target reference station. The method and the device can effectively reduce the frequency of changing the reference station in the operation of the rail train, further can provide observation data for a long time for the ambiguity fixing process, are particularly suitable for rail transit scenes, can effectively improve the ambiguity fixing efficiency and stability, and can meet the requirements of real-time performance and reliability of train positioning under the rail transit scenes.
Description
Technical Field
The application relates to the technical field of ambiguity fixing, in particular to an ambiguity fixing method and device in a rail transit scene and a train positioning terminal.
Background
In a rail traffic scene, a 5G traffic fusion system is adopted to perform carrier phase positioning of a rail train, and compared with a traditional train positioning method, the method has the advantages of no need of additional positioning equipment, low construction and maintenance cost and the like. Because the carrier phase positioning technology needs to consider the problem of ambiguity, the traditional ambiguity fixing method mainly aims at a satellite carrier phase positioning system and is not suitable for the scenes of dense base station distribution and high-speed movement of a positioning terminal.
Ambiguity fixing is one of the core problems of the carrier phase positioning technology, and the theory and method thereof are mainly developed around the carrier phase differential positioning technology of Global Navigation Satellite System (GNSS). The fixing of the ambiguity usually needs to select a reference station, construct a differential observation equation, eliminate common errors, solve by adopting a least square method or Kalman filtering to obtain an ambiguity floating solution, and then search according to an ambiguity floating solution covariance matrix to obtain an ambiguity fixed solution, thereby achieving the purpose of improving the positioning accuracy and stability.
Compared with a satellite positioning system, the 5G communication fusion system has a small coverage area, a train terminal has a high running speed, base stations in a visual range are changed continuously, and a reference base station for carrier phase positioning needs to be replaced continuously to meet the requirement of ambiguity fixing, but frequent replacement of the reference station not only can increase extra operation burden, but also can reduce the fixing efficiency and stability of ambiguity, and cannot meet the requirements of real-time performance and reliability of train positioning.
Disclosure of Invention
In view of this, embodiments of the present application provide a method and an apparatus for ambiguity fixing in a rail transit scene, and a train positioning terminal, so as to eliminate or improve one or more defects in the prior art.
One aspect of the present application provides a method for fixing ambiguity in a rail transit scene, including:
determining a current reference station replacement threshold interval and an ambiguity fixed threshold interval of the train based on receiving Doppler offsets corresponding to positioning signals sent by base stations distributed on two sides of a train running track and located in an observable range;
and determining the current target reference station of the train in each base station positioned in an observable range according to the reference station replacement threshold interval, and based on the target reference station, performing ambiguity fixing by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval.
In some embodiments of the present application, the determining, based on doppler offsets corresponding to positioning signals received from base stations distributed on both sides of a train track and located within an observable range, a current reference station replacement threshold interval and an ambiguity fixing threshold interval of the train includes:
receiving Doppler offsets corresponding to positioning signals respectively sent by base stations which are distributed on two sides of a train running track and located in an observable range;
normalizing each Doppler offset to obtain a corresponding normalized Doppler offset;
and respectively generating a reference station replacement threshold interval and an ambiguity fixed threshold interval corresponding to the current train according to the normalized Doppler shift and the total number of the base stations located in the observable range.
In some embodiments of the present application, said determining a current target reference station of the train in each of the base stations located within an observable range according to the reference station replacement threshold interval comprises:
if the reference station corresponding to the train exists currently, judging whether the reference station is in the reference station replacement threshold interval, and if so, determining the reference station as a target reference station;
and if the reference station corresponding to the train currently exists and the reference station is not in the reference station replacement threshold interval, or if the reference station corresponding to the train currently does not exist, selecting one base station in the reference station replacement threshold interval from the base stations in the observable range as a target reference station.
In some embodiments of the present application, selecting, as a target reference station, one of the base stations within the observable range that is within the reference station replacement threshold interval includes:
and selecting one base station with the Doppler shift smaller than an upper limit value in the replacement threshold interval of the reference station and the minimum difference value with the upper limit value from the base stations in the observable range as a target reference station.
In some embodiments of the present application, the fixing the ambiguity based on the target reference station by using an ambiguity fixing algorithm and the ambiguity fixing threshold interval includes:
constructing a double-difference observation equation corresponding to the target reference station;
based on the double-difference observation equation, determining a covariance matrix corresponding to the ambiguity floating point solution and the position parameter by using algorithms such as a least square method or Kalman filtering;
deleting the marked ambiguity floating solutions which are positioned outside the ambiguity fixed threshold interval in the covariance matrix, and taking the undeleted ambiguity floating solutions as target ambiguity floating solutions;
carrying out ambiguity fixing on each target ambiguity floating solution by adopting an ambiguity fixing algorithm to obtain a corresponding ambiguity fixed solution;
if the ambiguity fixed solution passes the fixed check, outputting the ambiguity fixed solution;
if the ambiguity fixed solution does not pass the fixed inspection, judging whether the ambiguity fixed solution is in the ambiguity fixed threshold interval, if so, outputting the ambiguity fixed solution; if not, outputting the ambiguity floating point solution and marking.
In some embodiments of the present application, after the determining the current reference station replacement threshold interval and the ambiguity fixing threshold interval of the train, the method further includes:
and if the total number of the base stations in the observable range changes, dynamically adjusting the replacement threshold interval of the reference station according to the changed total number of the base stations.
In some embodiments of the present application, after the determining the current reference station replacement threshold interval and the ambiguity fixing threshold interval of the train, the method further includes:
and dynamically adjusting the ambiguity fixed threshold interval according to the historical ambiguity fixed success rate counted in advance.
Another aspect of the present application provides an ambiguity fixing device in a rail transit scene, including:
the threshold interval setting module is used for determining a current reference station replacement threshold interval and an ambiguity fixing threshold interval of the train based on receiving Doppler offsets corresponding to positioning signals sent by all base stations which are distributed on two sides of a train running track and located in an observable range;
and the ambiguity fixing module is used for determining the current target reference station of the train in each base station positioned in an observable range according to the reference station replacement threshold interval and fixing the ambiguity by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval on the basis of the target reference station.
Another aspect of the present application provides a train positioning terminal, which is disposed on a train, and includes a memory, a processor, and a computer program stored in the memory and operable on the processor, where the processor implements the ambiguity fixing method in a track traffic scene when executing the computer program.
Another aspect of the present application provides a computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, implements the method for ambiguity fixing in a rail transit scenario.
The ambiguity fixing method under the rail transit scene determines a current reference station replacement threshold interval and an ambiguity fixing threshold interval of a train based on receiving Doppler offsets corresponding to positioning signals sent by base stations distributed on two sides of a train running track and located in an observable range; determining a current target reference station of the train in each base station positioned in an observable range according to the reference station replacement threshold interval, and based on the target reference station, performing ambiguity fixing by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval; the method comprises the steps that a reference station replacement threshold interval and an ambiguity fixing threshold interval are determined by obtaining Doppler frequency offset of base stations in an observable range, and a suitable reference station is selected in a large range of the reference station replacement threshold interval, so that the phenomenon that a nearest base station is continuously and quickly changed to be the reference station in the process that a train quickly runs on a track is avoided, the replacement frequency of the reference station in the running process of the track train can be effectively reduced, further, long-time observation data can be provided for the ambiguity fixing process, and the method is particularly suitable for track traffic scenes; meanwhile, ambiguity fixing is carried out according to an ambiguity fixing threshold value interval, the ambiguity fixing efficiency and stability can be effectively improved, and the requirements of real-time performance and reliability of train positioning in a rail transit scene can be met.
Additional advantages, objects, and features of the application will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present application are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present application will be more clearly understood from the detailed description that follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application, are incorporated in and constitute a part of this application, and are not intended to limit the application. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the application. For purposes of illustrating and describing certain portions of the present application, the drawings may have been enlarged, i.e., may be larger, relative to other features of the exemplary devices actually made in accordance with the present application. In the drawings:
fig. 1 is a general flowchart of an ambiguity fixing method in a rail transit scene according to an embodiment of the present application.
Fig. 2 is a schematic specific flowchart of a method for fixing ambiguity in a rail transit scene in an embodiment of the present application.
Fig. 3 is a schematic structural diagram of an ambiguity fixing device in a rail transit scene according to another embodiment of the present application.
Fig. 4 is a schematic diagram of relative distribution of a base station and a train provided in an example of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present application are provided to explain the present application and not to limit the present application.
Here, it should be further noted that, in order to avoid obscuring the present application with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present application are shown in the drawings, and other details not so related to the present application are omitted.
It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.
It is also noted that, unless otherwise specified, the term "coupled" is used herein to refer not only to a direct connection, but also to an indirect connection with an intermediate.
Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar components, or the same or similar steps.
If the traditional ambiguity fixing method is directly applied to a rail transit scene, a 5G communication fusion system is adopted to carry out carrier phase positioning aiming at a rail train positioning scene, a reference station is selected, and a double-difference observation equation is constructed to carry out ambiguity fixing. Examples are as follows:
first, the pseudorange and carrier phase observation equations may be expressed as:
in the formula (I), the compound is shown in the specification,
represents the geometric distance from the base station b to the positioning terminal u, c is the speed of light, delta t u For locating the clock difference of the terminals, δ t b Is the clock error at the base station end, lambda is the carrier wavelength,
is the carrier phase ambiguity between base station b and the positioning terminal.
Then, selecting a reference station r, and constructing a differential observation equation:
differentiating again can result in:
in the above formula, the double-difference pseudorange observation only contains a geometric distance term and a noise term, and the double-difference carrier phase observation only contains a geometric distance term, a double-difference ambiguity term and a noise term.
And finally, estimating according to an observation equation to obtain a double-difference carrier phase ambiguity floating solution and a covariance matrix, constructing an ambiguity search space, and outputting an ambiguity fixed solution after passing the inspection.
If the base station closest to the train is selected as the reference station, the reference station is continuously changed due to high-speed movement of the train, a difference observation equation needs to be reconstructed to estimate the ambiguity floating solution, and then the ambiguity is fixed according to the floating solution and the covariance matrix thereof. The speed of fixing the ambiguity and the success rate are limited to different degrees when the reference stations are frequently changed and the base stations within the visibility range are constantly changing.
Therefore, the scheme that the traditional ambiguity fixing method is directly applied to the rail transit scene only selects the base station closest to the terminal as the reference station, but in the positioning scene of the rail train, because the train has a high moving speed, the closest base station can be rapidly changed, and long-time observation data cannot be provided for ambiguity fixing, so that the ambiguity fixing in the rail scene is difficult to realize.
In order to solve the problems that a rail train runs fast, positioning base stations are distributed densely, reference base stations selected by ambiguity fixing can be frequently switched and the like, the embodiment of the application provides a method for quickly fixing ambiguity in a rail traffic scene, a device for quickly fixing ambiguity in the rail traffic scene, a train positioning terminal, a computer readable storage medium and the like, can effectively reduce the frequency of changing the reference stations in the operation of the rail train, can provide observation data for a longer time in the ambiguity fixing process, is particularly suitable for the rail traffic scene, can effectively improve the efficiency and stability of ambiguity fixing, and can meet the requirements of real-time performance and reliability of train positioning in the rail traffic scene
Based on this, an embodiment of the present application provides an ambiguity fixing method in a rail transit scene, and referring to fig. 1, the ambiguity fixing method in the rail transit scene specifically includes the following contents:
step 100: and determining a current reference station replacement threshold interval and an ambiguity fixed threshold interval of the train based on receiving Doppler offsets corresponding to positioning signals sent by all base stations distributed on two sides of a train running track and positioned in an observable range.
It can be understood that in a track scene, base stations are usually alternately arranged on two sides of a track, and when a train positioning terminal stably tracks positioning signals of all base stations in a visible range, a reference station replacement threshold interval and an ambiguity fixed threshold interval are divided according to Doppler shift conditions of different base stations. Because the base station position is fixed, the doppler offset of the signals transmitted by different base stations received by the train terminal is mainly determined by the train speed and the relative position of the train and the base station, that is, although the train position is unknown, the relative distance between the base station trains can be judged by the doppler offset of the received signals.
In one or more embodiments of the present application, the visible range or the observable range means that the positioning signal transmitted by the base station can meet the capturing and tracking requirements of the train positioning terminal when reaching the train positioning terminal, that is, the terminal can successfully receive the signal transmitted by the base station and resolve the signal by positioning.
Step 200: and determining the current target reference station of the train in each base station positioned in an observable range according to the reference station replacement threshold interval, and based on the target reference station, performing ambiguity fixing by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval.
In step 200, a suitable reference station is selected according to the reference station threshold interval and the reference station replacement threshold interval, whether the reference station needs to be replaced or not can be judged, the frequency of replacing the reference station is reduced, and meanwhile, the ambiguity is fixed according to the ambiguity fixed threshold interval, and the ambiguity fixing efficiency and stability are improved.
As can be seen from the above description, in the ambiguity fixing method in the rail transit scene provided in the embodiment of the present application, the doppler frequency offset of the base station in the observable range is obtained to determine the reference station change threshold interval and the ambiguity fixing threshold interval, so as to select a suitable reference station in a larger range of the reference station change threshold interval, thereby avoiding that the nearest base station is continuously and quickly changed to be the reference station in the process of fast train operation on the rail, effectively reducing the change frequency of the reference station in the rail train operation, and further providing long-time observation data for the ambiguity fixing process, and being particularly suitable for the rail transit scene; meanwhile, ambiguity fixing is carried out according to an ambiguity fixing threshold value interval, the ambiguity fixing efficiency and stability can be effectively improved, and the requirements of real-time performance and reliability of train positioning in a rail transit scene can be met.
In order to further improve the accuracy and effectiveness of forming the reference station replacement threshold interval and the ambiguity fixing threshold interval, in an ambiguity fixing method in a rail transit scene provided in an embodiment of the present application, referring to fig. 2, step 100 in the ambiguity fixing method in a rail transit scene further includes the following contents:
step 110: and receiving Doppler offsets corresponding to positioning signals respectively sent by all base stations which are distributed at two sides of a train running track and located in an observable range.
Step 120: and carrying out normalization processing on each Doppler offset to obtain a corresponding normalized Doppler offset.
Step 130: and respectively generating a reference station replacement threshold interval and an ambiguity fixed threshold interval corresponding to the current train according to the normalized Doppler shift and the total number of the base stations located in the observable range.
Specifically, the doppler shift is expressed as:
wherein i is the base station number, v is the train running speed, and theta i Is the included angle between the base station i and the train connecting line and the train running direction.
The above equation shows that the doppler shift has a maximum value when θ =0
When theta = pi, the Doppler shift has a minimum value
Because the base stations are uniformly distributed on the two sides of the track, the corresponding Doppler offsets are approximately symmetrically distributed, namely the Doppler offsets reflect the distance and the direction of the base stations relative to the train to a certain extent.
If the Doppler shift of N base stations is { f }respectively 0 ，f 1 ，...，f N Due to the fact that the running speed of the train changes, the corresponding Doppler offset fluctuates. Therefore, it needs to be normalized to obtain:
according to the number of base stations in a visible range and the Doppler relative offset, determining that the replacement threshold interval of the reference station is [ -f ] rep ，f rep ]. When the number of the base stations changes, the size of the interval is dynamically adjusted, and most stable observed values are contained in the interval.
As can be seen from the above description, according to the ambiguity fixing method in a rail transit scene provided in the embodiment of the present application, since the running speed of a train changes and the corresponding doppler shift amount fluctuates, the accuracy and effectiveness of forming the replacement threshold interval of the reference station and the ambiguity fixing threshold interval can be effectively improved by performing normalization processing on each pair of doppler shift amounts, and thus the accuracy and reliability of ambiguity fixing can be further improved.
In order to further reduce the frequency of replacing a reference station in the operation of a rail train, in a method for fixing the ambiguity in a rail transit scene provided in an embodiment of the present application, referring to fig. 2, a step 200 in the method for fixing the ambiguity in the rail transit scene specifically includes the following contents:
step 210: and if the reference station corresponding to the train exists currently, judging whether the reference station is in the reference station replacement threshold interval, and if so, determining the reference station as a target reference station.
Step 220: and if the reference station corresponding to the train currently exists and the reference station is not in the reference station replacement threshold interval, or if the reference station corresponding to the train currently does not exist, selecting one base station in the reference station replacement threshold interval from the base stations in the observable range as a target reference station.
Step 230: and based on the target reference station, carrying out ambiguity fixing by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval.
As can be seen from the above description, in the ambiguity fixing method in a rail transit scene provided in the embodiment of the present application, the current target reference station of the train is determined in each base station in the observable range according to the situation of the reference station replacement threshold interval, so that the practicality and effectiveness of determining the target reference station can be effectively improved, frequent replacement of the reference station is avoided, the frequency of replacing the reference station during rail train operation can be further reduced, and further, long-time observation data can be provided for the ambiguity fixing process.
In order to further reduce the frequency of replacing reference stations in the operation of a rail train, in the ambiguity fixing method in a rail transit scene provided in the embodiment of the present application, the process of selecting one base station located in the replacement threshold interval of the reference station from the base stations in the observable range in step 220 in the ambiguity fixing method in the rail transit scene as a target reference station specifically includes the following steps:
step 221: and selecting one base station with the Doppler shift smaller than an upper limit value in the replacement threshold interval of the reference station and the minimum difference value with the upper limit value from the base stations in the observable range as a target reference station.
Specifically, when the reference station is replaced by the reference station, the replacement threshold interval is [ -f [ ] rep ，f rep ]Then, selecting the Doppler shift amount just smaller than the right value of the interval, namely f rep The corresponding base station is the reference station when the reference stationIs less than the left value of the threshold interval, i.e. -f rep When the Doppler shift is smaller than the interval right value, f is changed to the next Doppler shift rep The corresponding base station.
As can be seen from the above description, in the ambiguity fixing method in a rail transit scene provided in the embodiment of the present application, by selecting, as a target reference station, a base station whose doppler offset is smaller than an upper limit value in a replacement threshold interval of the reference station and whose difference with the upper limit value is the smallest, the application duration of the target base station can be effectively increased, the replacement frequency of the reference station during operation of a rail train is further reduced, and thus, long-time observation data can be provided for the ambiguity fixing process.
In order to further improve the efficiency and stability of ambiguity fixing, in the ambiguity fixing method in a rail transit scene provided in the embodiment of the present application, step 230 in the ambiguity fixing method in a rail transit scene further includes the following contents:
step 231: and constructing a double-difference observation equation corresponding to the target reference station.
Step 232: and determining the covariance matrix corresponding to the ambiguity floating point solution and the position parameter by using algorithms such as a least square method or Kalman filtering and the like based on the double-difference observation equation.
Step 233: and deleting the marked ambiguity floating solutions which are positioned outside the ambiguity fixed threshold interval in the covariance matrix, and taking the undeleted ambiguity floating solutions as target ambiguity floating solutions.
Step 234: and carrying out ambiguity fixing on each target ambiguity floating solution by adopting an ambiguity fixing algorithm to obtain a corresponding ambiguity fixing solution.
Step 235: and if the ambiguity fixed solution passes the fixed check, outputting the ambiguity fixed solution. Step 236: if the ambiguity fixed solution does not pass the fixed inspection, judging whether the ambiguity fixed solution is in the ambiguity fixed threshold interval, if so, outputting the ambiguity fixed solution; if not, the ambiguity floating solution is output and marked.
It can be understood that the train positioning terminal can output pseudo range, carrier wave and Doppler observed value by capturing and tracking the signal transmitted by the base station. The observation equations corresponding to the pseudo range, the carrier wave and the Doppler are as follows:
if the selected reference station is r, constructing a double-difference observation equation:
according to an observation equation, obtaining a covariance matrix Q corresponding to the position parameters and the ambiguity floating point solution parameters by adopting least square method or Kalman filtering and other algorithms for estimation yy Namely:
wherein Q is aa To solve the covariance matrix, Q, in floating point xx As a position covariance matrix, Q xa And Q ax The ambiguity float solution and the position parameter covariance matrix.
Excluding the labeled ambiguity floating solutions outside the ambiguity fixed threshold interval according to the floating solution covariance matrix Q aa And fixing the ambiguity, if the fixed check is passed, outputting a ambiguity fixed solution, otherwise, marking the ambiguity outside the threshold interval and outputting an ambiguity floating solution.
As can be seen from the above description, in the ambiguity fixing method in the rail transit scene provided in the embodiment of the present application, by deleting the labeled ambiguity floating solutions outside the ambiguity fixed threshold interval in the covariance matrix, taking the ambiguity floating solutions that are not deleted as the target ambiguity floating solutions, and performing ambiguity fixing on each target ambiguity floating solution by using an ambiguity fixing algorithm, etc., the ambiguity fixing efficiency and stability can be further improved, and the requirements of real-time performance and reliability of train positioning in the rail transit scene can be met.
In order to further ensure the validity, i.e. reliability, of the ambiguity fixing in the rail transit scene, in the ambiguity fixing method in the rail transit scene provided in the embodiment of the present application, referring to fig. 2, the following contents are also specifically included after step 100 or step 130 in the ambiguity fixing method in the rail transit scene:
step 300: and if the total number of the base stations in the observable range changes, dynamically adjusting the replacement threshold interval of the reference station according to the changed total number of the base stations.
From the above description, the ambiguity fixing method in the rail transit scene provided in the embodiment of the present application can effectively improve the application reliability and effectiveness of the replacement threshold interval of the reference station by dynamically adjusting the replacement threshold interval of the reference station, and further can further ensure the effectiveness, i.e., reliability, of ambiguity fixing in the rail transit scene.
In order to further ensure the validity, i.e. reliability, of the ambiguity fixing in the rail transit scene, in the ambiguity fixing method in the rail transit scene provided in the embodiment of the present application, referring to fig. 2, the following contents are also specifically included after step 100 or step 130 in the ambiguity fixing method in the rail transit scene:
step 400: and dynamically adjusting the ambiguity fixing threshold interval according to the historical ambiguity fixing success rate counted in advance.
From the above description, the ambiguity fixing method in the rail transit scene provided in the embodiment of the present application can effectively improve the application reliability and effectiveness of the ambiguity fixing threshold interval by dynamically adjusting the ambiguity fixing threshold interval, and further can further ensure the effectiveness, i.e., reliability, of ambiguity fixing in the rail transit scene.
From the aspect of software, the present application further provides an ambiguity fixing device for a rail transit scene, which is used for executing all or part of the ambiguity fixing method in the rail transit scene, and referring to fig. 3, the ambiguity fixing device in the rail transit scene specifically includes the following contents:
the threshold interval setting module 10 is configured to determine a change threshold interval and an ambiguity fixed threshold interval of a current reference station of the train based on receiving doppler offsets corresponding to positioning signals sent by base stations distributed on two sides of a train running track and located within an observable range.
And an ambiguity fixing module 20, configured to determine a current target reference station of the train in each base station located in an observable range according to the reference station replacement threshold interval, and perform ambiguity fixing by using an ambiguity fixing algorithm and the ambiguity fixing threshold interval based on the target reference station.
The embodiment of the ambiguity fixing device in the rail transit scene provided by the present application may be specifically used to execute the processing procedure of the embodiment of the ambiguity fixing method in the rail transit scene in the above embodiments, and the functions thereof are not described herein again, and reference may be made to the detailed description of the embodiment of the ambiguity fixing method in the rail transit scene.
The ambiguity fixing device in the rail transit scene can be executed in the server, and in another practical application situation, all the operations can be completed in the client device. The selection may be specifically performed according to the processing capability of the client device, the limitation of the user usage scenario, and the like. This is not a limitation of the present application. If all the operations are completed in the client device, the client device may further include a processor for performing specific processing of ambiguity fixing in a rail transit scene.
The client device may have a communication module (i.e., a communication unit) and may be communicatively connected to a remote server to implement data transmission with the server. The server may include a server on the task scheduling center side, and in other implementation scenarios, the server may also include a server on an intermediate platform, for example, a server on a third-party server platform that is communicatively linked to the task scheduling center server. The server may include a single computer device, or may include a server cluster formed by a plurality of servers, or a server structure of a distributed apparatus.
The server and the client device may communicate using any suitable network protocol, including a network protocol that has not been developed at the filing date of the present application. The network protocol may include, for example, a TCP/IP protocol, a UDP/IP protocol, an HTTP protocol, an HTTPS protocol, or the like. Of course, the network Protocol may also include, for example, an RPC Protocol (Remote Procedure Call Protocol), a REST Protocol (Representational State Transfer Protocol), and the like used above the above Protocol.
As can be seen from the above description, the ambiguity fixing device in the rail transit scene provided in the embodiment of the present application determines the reference station change threshold interval and the ambiguity fixing threshold interval by obtaining the doppler frequency offset of the base station in the observable range, so as to select a suitable reference station in a larger range of the reference station change threshold interval, thereby avoiding that the nearest base station is continuously and quickly changed as the reference station in the process of fast train operation on the rail, effectively reducing the change frequency of the reference station in the rail train operation, and further providing long-time observation data for the ambiguity fixing process, and is particularly suitable for the rail transit scene; meanwhile, ambiguity fixing is carried out according to an ambiguity fixing threshold interval, the ambiguity fixing efficiency and stability can be effectively improved, and the requirements of real-time performance and reliability of train positioning in a rail transit scene can be met.
The embodiment of the present application further provides a train positioning terminal (i.e., an electronic device), where the train positioning terminal may include a processor, a memory, a receiver, and a transmitter, and the processor is configured to execute the method for fixing ambiguity in a rail transit scenario mentioned in the foregoing embodiment, where the processor and the memory may be connected by a bus or in another manner, for example, connected by a bus. The receiver can be connected with the processor and the memory in a wired or wireless mode. The train positioning terminal can receive real-time motion data from a sensor in the wireless multimedia sensor network and receive an original video sequence from the video acquisition device.
The processor may be a Central Processing Unit (CPU). The Processor may also be other general purpose processors, digital Signal Processors (DSPs), application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components, or a combination thereof.
The memory, which is a non-transitory computer readable storage medium, may be used to store non-transitory software programs, non-transitory computer executable programs, and modules, such as program instructions/modules corresponding to the ambiguity fixing method in the track traffic scenario in the embodiments of the present application. The processor executes various functional applications and data processing of the processor by running the non-transitory software program, instructions and modules stored in the memory, that is, the method for fixing the ambiguity in the rail transit scene in the above method embodiment is implemented.
The memory may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created by the processor, and the like. Further, the memory may include high speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid state storage device. In some embodiments, the memory optionally includes memory located remotely from the processor, and such remote memory may be coupled to the processor via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The one or more modules are stored in the memory and, when executed by the processor, perform a method of ambiguity fixing in a rail transit scenario, in an embodiment.
In some embodiments of the present application, the user equipment may include a processor, a memory, and a transceiver unit, the transceiver unit may include a receiver and a transmitter, the processor, the memory, the receiver, and the transmitter may be connected by a bus system, the memory is configured to store computer instructions, and the processor is configured to execute the computer instructions stored in the memory to control the transceiver unit to transceive signals.
As an implementation manner, the functions of the receiver and the transmitter in this application may be considered to be implemented by a transceiving circuit or a transceiving dedicated chip, and the processor may be considered to be implemented by a dedicated processing chip, a processing circuit or a general-purpose chip.
As another implementation manner, a manner of using a general-purpose computer to implement the server provided in the embodiment of the present application may be considered. That is, program code that implements the functions of the processor, receiver, and transmitter is stored in the memory, and a general-purpose processor implements the functions of the processor, receiver, and transmitter by executing the code in the memory.
The embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor to implement the steps of the method for fixing the ambiguity in the track traffic scene. The computer readable storage medium may be a tangible storage medium such as Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, floppy disks, hard disks, removable storage disks, CD-ROMs, or any other form of storage medium known in the art.
In order to further explain the scheme, the application also provides a specific application example of the ambiguity fixing method in a rail transit scene, and the method comprises the following steps of firstly, determining a reference station replacement threshold interval and an ambiguity fixing threshold interval according to the Doppler offset of a rail train received signal; secondly, ambiguity fixing is carried out by adopting an ambiguity fixing algorithm such as LAMBDA (label analysis and data acquisition) algorithm, if the ambiguity fixing inspection is passed, an ambiguity fixing solution is output, if the ambiguity fixing inspection is failed, and the Doppler offset of the ambiguity corresponding signal exceeds an ambiguity fixing threshold value, a floating solution is output, and meanwhile, the ambiguity is not searched and fixed at the next epoch observation time. By adopting the method, the search efficiency and stability of the ambiguity can be improved.
The ambiguity fixing method in the rail transit scene provided by the application example of the application example specifically comprises the following contents:
dividing threshold interval according to Doppler relative offset
In a track traffic scene, base stations are usually alternately arranged on two sides of a track, and when a train positioning terminal stably tracks positioning signals of all base stations in a visible range, a reference station replacement threshold interval and an ambiguity fixed threshold interval are divided according to Doppler shift conditions of different base stations. Because the base station position is fixed, the doppler offset of the signals transmitted by different base stations received by the train terminal is mainly determined by the train speed and the relative position of the train and the base station, that is, although the train position is unknown, the relative distance between the base station trains can be judged by the doppler offset of the received signals.
The doppler shift is expressed as:
wherein i is the base station number, v is the train running speed, and theta i The included angle between the base station i and the train connecting line and the train running direction is shown.
The above equation shows that the doppler shift has a maximum value when θ =0
When theta = pi, the Doppler shift has a minimum value
Because the base stations are uniformly distributed on the two sides of the track, the corresponding Doppler offsets are approximately symmetrically distributed, namely the Doppler offsets reflect the distance and the direction of the base stations relative to the train to a certain extent.
If the Doppler shift of N base stations is { f } 0 ，f 1 ，...，f N Due to the fact that the running speed of the train changes, the corresponding Doppler offset fluctuates. Therefore, it needs to be normalized to obtain:
according to the number of base stations in a visible range and the Doppler relative offset, determining that the replacement threshold interval of the reference station is [ -f ] rep ，f rep ]. When the number of the base stations changes, the size of the interval is dynamically adjusted, and most stable observed values are contained in the interval.
Determining a fixed threshold interval of ambiguity [ -f [ ] fix ，f fix ]And preferentially fixing the base station ambiguity of the Doppler offset in the range of the ambiguity fixed threshold interval, and dynamically adjusting the size of the threshold interval according to the ambiguity fixed success rate in a plurality of observation epochs.
(II) selecting reference station and fixing ambiguity according to threshold interval
The train positioning terminal can output pseudo range, carrier wave and Doppler observed value by capturing and tracking signals transmitted by the base station. The observation equations corresponding to the pseudo range, the carrier wave and the Doppler are as follows:
when the replacement threshold interval of the reference station is [ -f ] rep ，f rep ]Then, selecting the value f when the Doppler shift is just smaller than the right value of the interval rep The corresponding base station is a reference station, and when the Doppler shift amount of the reference station is smaller than the left value of the threshold interval, the base station is the value-f rep When the Doppler shift is smaller than the interval right value, f is used as the reference station rep The corresponding base station. If the selected reference station is r, constructing a double-difference observation equation:
according to an observation equation, obtaining a covariance matrix Q corresponding to the position parameters and the ambiguity floating point solution parameters by adopting least square method or Kalman filtering and other algorithms for estimation yy Namely:
wherein Q is aa To solve the covariance matrix, Q, in floating point xx As a position covariance matrix, Q xa And Q ax The ambiguity float solution and the position parameter covariance matrix.
Excluding the labeled ambiguity floating solutions outside the ambiguity fixed threshold interval according to the floating solution covariance matrix Q aa And fixing the ambiguity, if the fixed check is passed, outputting a ambiguity fixed solution, otherwise, marking the ambiguity outside the threshold interval and outputting an ambiguity floating solution.
The specific process is as follows:
(1) Firstly, determining a replacement threshold interval of a reference station and a fixed threshold interval of ambiguity according to the normalized Doppler shift and the number of observable base stations; specifically, the doppler shift f of the base station in the visible range can be determined i Calculating the corresponding normalized Doppler shift
And to the absolute value of the normalized Doppler shift
Sorting to select near theta i =15 ° and θ i Normalized doppler shift amount corresponding to =30 ° as reference station replacement threshold value f rep And a threshold value f for replacing the degree of ambiguity fix And f is rep As an upper limit value of the replacement threshold interval of the reference station, -f rep As a lower limit value of the reference station replacement threshold interval, f fix Upper limit value as a threshold interval for fixed ambiguity, -f fix As a degree of ambiguityThe lower limit value of the threshold interval is fixed.
It can be understood that θ i Taking 15 ° and 30 ° as just one reference illustration, it is used to show the proportional relationship of the normalized doppler shift in the visible range to the reference station change threshold interval and the ambiguity fix threshold interval. In practical application, θ i The value can be specifically set according to the actual application condition.
(2) Then, if the reference station is determined, detecting whether the reference station is in a reference station replacement threshold interval, if the reference station is beyond the interval range, re-selecting a proper reference station according to the reference station replacement threshold interval, otherwise, constructing a double-difference observation equation and outputting a ambiguity floating point solution;
(3) And then, excluding the marked ambiguity floating solutions outside the ambiguity fixed interval, and fixing the rest ambiguity floating solutions by adopting an ambiguity fixing algorithm.
(4) If the detection is successful, outputting a ambiguity fixed solution, otherwise, judging whether the ambiguity fixed solution is in an ambiguity fixed threshold range, if the ambiguity fixed solution exceeds the range, outputting an ambiguity floating solution and marking, otherwise, outputting the ambiguity floating solution.
The ambiguity fixing method in the rail transit scene provided by the application example can reduce the influence of frequent replacement of the reference station on ambiguity fixing, and improve the reliability and usability of ambiguity fixing in the rail transit scene.
In a specific example, the ambiguity fixing method in the rail transit scene can be used for fixing the carrier phase positioning ambiguity of the traffic fusion system in the rail transit scene, and a reference station replacement threshold interval and an ambiguity fixing threshold interval are determined according to the Doppler offset of a rail train receiving signal, so that the replacement frequency of the reference station is effectively reduced, and the ambiguity searching and fixing efficiency is improved.
Referring to the relative distribution diagram of the base stations and the train shown in FIG. 4, assuming that the base stations are uniformly arranged on both sides of the track, the adjacent base stations are spaced by 100M, and the running speed v of the rail train M is 100M 0 ＝100km/h,t 0 The observable base station corresponding to the observation time is { A } 0 ，A 1 ，...，A 8 The corresponding Doppler shift amounts are { f } respectively 0 ，f 1 ，...，f 8 Normalized Doppler shift of
Determining a reference station replacement threshold value as
The ambiguity fixed threshold is
With the movement of the train, the reference base station A 4 The corresponding Doppler shift amount is gradually reduced at t 1 Observing time, if referring to base station A 4 Corresponding Doppler shift amount
Just less than the left value-f of the reference station replacement threshold interval rep Replacing the reference station, and selecting a right value f of the interval that the Doppler offset at the current moment is just smaller than the replacement threshold value of the reference station rep The corresponding base station serves as a new reference station. Whether the reference station is adjusted or not is judged through the replacement threshold interval of the reference station, the replacement frequency of the reference station can be effectively reduced, and the stability of subsequent ambiguity fixing is improved.
According to t 0 Pseudo range, carrier phase and Doppler observed quantity of received signals at observation time, constructing a double-difference observation equation, obtaining ambiguity floating point solution estimated quantity by adopting algorithms such as least square method or Kalman filtering, fixing ambiguity, and if the ambiguity is outside a fixed threshold interval, obtaining a base station A by using the ambiguity floating point solution estimated quantity 7 And A 8 The corresponding ambiguity fixed solution is not checked, ambiguity floating solution is output and marked, and the next observation epoch base station A 7 Still outside the ambiguity fixed threshold interval and marked, and directly outputting ambiguity floating solution without performing ambiguity fixed operation, and the base station A 8 And within the ambiguity fixed threshold interval, fixing the ambiguity. By passingThe threshold interval is fixed by the ambiguity to judge whether the ambiguity is fixed or not, so that the ambiguity fixing efficiency and the ambiguity fixing success rate can be improved.
In summary, the application example of the application provides an ambiguity fixing method for a rail transit scene, and a reference station replacement threshold interval and an ambiguity fixing threshold interval are determined according to the number of base stations in an observable range and corresponding normalized doppler frequency offset; and selecting a proper reference station according to the reference station replacement threshold interval, judging whether the reference station needs to be replaced, reducing the frequency of replacing the reference station, and fixing the ambiguity according to the ambiguity fixed threshold interval to improve the ambiguity fixing efficiency and stability.
Those of ordinary skill in the art will appreciate that the various illustrative components, systems, and methods described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations thereof. Whether this is done in hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the present application are the programs or code segments used to perform the required tasks. The program or code segments can be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link.
It is to be understood that the present application is not limited to the particular arrangements and instrumentalities described above and shown in the attached drawings. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present application are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps, after comprehending the spirit of the present application.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made to the embodiment of the present application by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. A method for fixing ambiguity in a rail transit scene is characterized by comprising the following steps:
determining a current reference station replacement threshold interval and an ambiguity fixed threshold interval of the train based on Doppler offsets corresponding to positioning signals sent by base stations which are distributed on two sides of a train running track and located in an observable range;
and determining the current target reference station of the train in each base station positioned in an observable range according to the reference station replacement threshold interval, and based on the target reference station, performing ambiguity fixing by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval.
2. The method for fixing the ambiguity in the rail transit scene according to claim 1, wherein the determining the current reference station replacement threshold interval and the ambiguity fixing threshold interval of the train based on the doppler offsets corresponding to the positioning signals sent by the base stations distributed at two sides of the train running track and located in the observable range includes:
receiving Doppler offsets corresponding to positioning signals respectively sent by base stations which are distributed on two sides of a train running track and located in an observable range;
normalizing each Doppler offset to obtain a corresponding normalized Doppler offset;
and respectively generating a reference station replacement threshold interval and an ambiguity fixed threshold interval corresponding to the current train according to the normalized Doppler shift and the total number of the base stations located in the observable range.
3. The method for fixing the ambiguity in the rail transit scenario according to claim 1, wherein the determining the current target reference station of the train in each base station located in an observable range according to the reference station replacement threshold interval comprises:
if the reference station corresponding to the train exists currently, judging whether the reference station is in the reference station replacement threshold interval, and if so, determining the reference station as a target reference station;
and if the reference station corresponding to the train currently exists and the reference station is not in the reference station replacement threshold interval, or if the reference station corresponding to the train currently does not exist, selecting one base station in the reference station replacement threshold interval from the base stations in the observable range as a target reference station.
4. The method as claimed in claim 3, wherein the selecting one of the base stations in the observable range that is within the replacement threshold interval of the reference station as the target reference station comprises:
and selecting one base station with the Doppler shift amount smaller than an upper limit value in the replacement threshold interval of the reference station and the minimum difference value with the upper limit value as a target reference station from the base stations in the observable range.
5. The method for fixing the ambiguity in the rail transit scene according to claim 1, wherein the ambiguity fixing is performed by using an ambiguity fixing algorithm and the ambiguity fixing threshold interval based on the target reference station, and the method comprises:
constructing a double-difference observation equation corresponding to the target reference station;
based on the double-difference observation equation, determining a covariance matrix corresponding to the ambiguity floating point solution and the position parameter by using algorithms such as a least square method or Kalman filtering;
deleting the marked ambiguity floating solutions outside the ambiguity fixed threshold interval in the covariance matrix, and taking the undeleted ambiguity floating solutions as target ambiguity floating solutions;
carrying out ambiguity fixing on each target ambiguity floating solution by adopting an ambiguity fixing algorithm to obtain a corresponding ambiguity fixing solution;
if the ambiguity fixed solution passes the fixed check, outputting the ambiguity fixed solution;
if the ambiguity fixed solution does not pass the fixed inspection, judging whether the ambiguity fixed solution is in the ambiguity fixed threshold interval, if so, outputting the ambiguity fixed solution; if not, the ambiguity floating solution is output and marked.
6. The method for fixing the ambiguity in the rail transit scenario according to any one of claims 2, wherein after the determining the current reference station replacement threshold interval and the ambiguity fixing threshold interval of the train, the method further comprises:
and if the total number of the base stations in the observable range changes, dynamically adjusting the replacement threshold interval of the reference station according to the changed total number of the base stations.
7. The method for fixing the ambiguity under the rail transit scenario according to any one of claims 1 to 5, further comprising, after the determining the current reference station replacement threshold interval and ambiguity fixing threshold interval of the train:
and dynamically adjusting the ambiguity fixing threshold interval according to the historical ambiguity fixing success rate counted in advance.
8. An ambiguity fixing device under a rail transit scene is characterized by comprising:
the threshold interval setting module is used for determining a current reference station replacement threshold interval and an ambiguity fixing threshold interval of the train based on receiving Doppler offsets corresponding to positioning signals sent by all base stations which are distributed on two sides of a train running track and located in an observable range;
and the ambiguity fixing module is used for determining the current target reference station of the train in each base station positioned in an observable range according to the reference station replacement threshold interval and fixing the ambiguity by adopting an ambiguity fixing algorithm and the ambiguity fixing threshold interval on the basis of the target reference station.
9. A train positioning terminal, which is disposed on a train and includes a memory, a processor and a computer program stored on the memory and running on the processor, wherein the processor executes the computer program to implement the ambiguity fixing method in a rail transit scenario according to any one of claims 1 to 7.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, implements the method for fixing the ambiguity in a rail transit scenario according to any one of claims 1 to 7.
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