JP6017983B2 - Vehicle position measuring method and vehicle position measuring system - Google Patents

Description

  The present invention relates to a vehicle position measurement method for measuring the position of a vehicle.

Understanding the location of trains is essential for the safe operation of railways.
As the position detection method, for example, a method using a track circuit, a method using a speed generator (for example, Patent Document 1), a method using positioning information by GPS (Global Positioning System) (for example, Patent Document 2, Patent Document) 3) etc. are known.

JP 2012-20734 A Japanese Patent Laid-Open No. 2006-240478 JP 2002-335607 A

  The measurement of the vehicle position that does not require or minimizes ground facilities such as track circuits is highly demanded, for example, in a quiet line area. When using GPS positioning information instead of the track circuit, it is important to reduce the measurement error. As one of GPS measurement errors, “multipath” is known. Multipath is an error that occurs when a signal reflected from the ground surface, a tree, a building, or the like arrives from outside a straight path from a GPS satellite and interferes with a signal that has reached the straight path. Note that there is a problem of multipath even when a satellite positioning system other than GPS satellites is used. Moreover, vehicles other than trains, such as a motor vehicle, have this problem.

  An object of the present invention is to reduce the influence of multipath when measuring a vehicle position using a satellite positioning system.

A first invention for solving the above problems is a vehicle position measuring method for measuring the position of a vehicle based on a satellite signal received from a satellite, and a capturing step (for example, capturing a satellite signal of each candidate satellite) , Step S2) of FIG.
A pseudo distance calculating step (for example, step S8 in FIG. 7) for calculating a pseudo distance related to the captured satellite signal;
A Doppler shift frequency calculating step (for example, Step S10 in FIG. 7) for calculating a Doppler shift frequency related to the captured satellite signal;
For each of the candidate satellites, a deviation amount calculating step for calculating a deviation amount between the pseudo distance change based on the calculated pseudo distance and a relative movement amount between the candidate satellite and the vehicle based on the calculated Doppler shift frequency ( For example, step S24) in FIG.
A satellite selection step (for example, step S40 in FIG. 7) for selecting a satellite to be used for positioning from the candidate satellites using the calculated deviation amount;
And a positioning step (for example, step S46 in FIG. 7) for positioning based on the satellite signal of the selected satellite.

In another embodiment, the vehicle position measurement system measures the position of the vehicle based on the satellite signal received from the satellite, and includes a capturing unit that captures the satellite signal of each candidate satellite (for example, the CPU 24 in FIG. 3, baseband processing). Unit 30, capture unit 301, step S2) of FIG.
A pseudo distance calculation unit (for example, the CPU 24 in FIG. 3, the baseband processing unit 30, the pseudo distance calculation unit 303, and step S8 in FIG. 7) that calculates a pseudo distance related to the captured satellite signal;
A Doppler shift frequency calculation unit for calculating a Doppler shift frequency related to the captured satellite signal (for example, the CPU 24 in FIG. 3, the baseband processing unit 30, the Doppler shift frequency calculation unit 305, Step S10 in FIG. 7);
For each of the candidate satellites, a deviation amount calculation unit that calculates a deviation amount between the pseudo distance change based on the calculated pseudo distance and a relative movement amount between the candidate satellite and the vehicle based on the calculated Doppler shift frequency ( For example, the CPU 24 in FIG. 3, the divergence amount calculation unit 32, step S24 in FIG.
A satellite selection unit (for example, CPU 24 in FIG. 3, satellite selection unit 36, step S40 in FIG. 7) for selecting a satellite to be used for positioning from the candidate satellites using the calculated deviation amount;
A vehicle position measurement system including a positioning unit (for example, the CPU 24, the positioning calculation unit 38, and step S46 in FIG. 7) that performs positioning based on the satellite signal of the selected satellite can be configured.

  According to the first invention and the like, the position of the vehicle can be measured using the satellite signal. In the position measurement, for each candidate satellite, a deviation amount between the pseudo distance change based on the pseudo distance and the relative movement amount between the candidate satellite and the vehicle based on the Doppler shift frequency can be calculated. The pseudo-range change amount is easily affected by multipath in principle, but the Doppler shift frequency is hardly affected by multipath. Therefore, the amount of divergence, which is the difference between the two, can be said to be an index indicating the degree of multipath influence. Therefore, the influence of multipath can be reduced by selecting a satellite to be used for positioning from the candidate satellites using the calculated deviation amount.

More specifically, as the second invention, the divergence amount calculating step calculates the pseudo distance change amount from a difference between the pseudo distance calculated in the first epoch and the pseudo distance calculated in the second epoch. (For example, step S12 in FIG. 7);
The relative movement using the Doppler shift frequency calculated in the first epoch, the average frequency of the Doppler shift frequency calculated in the second epoch, and the time interval between the first epoch and the second epoch. The vehicle position measuring method according to the first aspect of the present invention can include the step of calculating the quantity (for example, step S20 in FIG. 7).

  Then, if the first invention and the second invention are applied to a railway, as the third invention, the vehicle is a train traveling on a track, and the deviation amount determined for each area along the track The method further includes a determination reference value selection step (for example, step S26 in FIG. 7) for selecting a determination reference value corresponding to the positioning result from the determination reference values for determination, and the satellite selection step includes the selection. The vehicle position measurement method according to the first or second aspect of the invention may be configured such that the determined reference value is compared with the calculated divergence amount and the satellite used for positioning is selected based on the comparison result. .

  According to the third invention, the same effect as the first or second invention is obtained, and the trajectory in which the influence of the multipath changes depending on the location by using the criterion value for each area along the trajectory. Even so, the effects of multipath can be reduced appropriately. For example, in an area where the influence of multipath is relatively high, if the criterion value is set larger than that in other regions, the criterion becomes too strict, resulting in a limited number of satellites that can be used for positioning. While avoiding the inability to perform positioning, it is possible to avoid the use of satellites that are highly affected by multipath.

The figure which shows the structural example of a vehicle position measurement system. The principle diagram in which a vehicle position measurement system reduces the influence of multipath. The functional block diagram which shows the function structural example of a vehicle position measurement system. The figure which shows an example of the data structure of determination reference value setting data. The figure which shows an example of a data structure of pseudo distance history data. The figure which shows an example of a data structure of Doppler shift frequency historical data. The flowchart for demonstrating the flow of the process for performing positioning once. The figure which shows an example of a data structure of deviation | shift amount log | history data. The flowchart for demonstrating the flow of the process for performing positioning once in the modification.

[First Embodiment]
A vehicle position measurement system to which the present invention is applied will be described. In the present embodiment, the GPS is described as being used, but can be appropriately replaced with another satellite positioning system. In addition, the measurement timing of the vehicle position is hereinafter referred to as “epoch”.

[Description of system configuration]
FIG. 1 is a diagram illustrating a configuration example of a vehicle position measurement system in the present embodiment. In addition, the description about the circuit etc. which supply electric power to the vehicle position measurement system 2 is abbreviate | omitted.

The vehicle position measurement system 2 of the present embodiment is a system that measures the position of a train 4 that is a vehicle traveling on a track 3 and is mounted on the train 4.
The vehicle position measurement system 2 includes a GPS antenna 21 that receives a satellite signal 7 transmitted from a GPS satellite 6, an RF (Radio Frequency) receiver 22, a CPU (Central Processing Unit) 24, an IC memory 26, an RTC (Real Time Clock) 27 and a communication I / F (Interface) 28. The RF receiver 22, the CPU 24, the IC memory 26, the RTC 27, and the communication I / F 28 are connected via a bus 29 so that data can be transmitted and received.

The GPS antenna 21 converts a radio wave transmitted from the GPS satellite 6 into an electrical signal and outputs the electrical signal to the RF receiving unit 22.
The RF receiver 22 converts the signal input from the GPS antenna 21 into an intermediate frequency, converts it into a digital signal, and outputs it as a digital IF signal. For example, the RF receiving unit 22 digitally converts various down-converted IF signals into down-converters that convert to IF signals (IF: Intermediate Frequency) in addition to various filter circuits and low-noise amplifiers (LNA). An A / D converter that converts the signal into a signal is included. The RF receiver 22 can use a well-known GPS front-end analog circuit or front-end IC.

  The CPU 24 (1) captures and tracks satellite signals based on the digital IF signal input from the RF receiver 22, calculates pseudoranges, decodes navigation messages such as Almanac and Ephemeris, etc. In other words, so-called baseband processing, (2) positioning calculation processing, and (3) external output control processing for outputting position coordinates as positioning results to the communication I / F 28 can be executed.

  The IC memory 26 is an information storage medium that temporarily or nonvolatilely stores programs and data necessary for arithmetic processing by the CPU 24. It is realized by RAM or ROM. Moreover, it is good also as providing a hard disk as an alternative memory | storage part.

  The RTC 27 outputs a reference time in the vehicle position measurement system 2. The configuration may be appropriately connected to a battery (not shown).

  The communication I / F 28 realizes data communication with a device outside the measurement system. A so-called interface IC, communication terminal, wireless device, or the like can be appropriately used. For example, vehicle position information (in this embodiment, a GPS coordinate value) or the like can be output outside the measurement system.

  The CPU 24 and the IC memory 26 may be realized as a one-chip system LSI. Moreover, the structure implement | achieved as one module further including the GPS antenna 21 and RF receiving part 22 may be sufficient.

[Description of Principle]
FIG. 2 is a diagram for explaining the principle that the vehicle position measurement system 2 reduces the influence of multipath. The vehicle position measurement system 2 receives the satellite signal 7 (7a) from the GPS satellite 6 (6a) with the GPS antenna 21 at the epoch t1. At this time, based on the received satellite signal 7 (7a), the pseudo distance L1 from the GPS satellite star 6 (6a) to the train 4 (4a) and the Doppler shift frequency fd1 related to the relative movement of both are obtained. it can.

  Similarly, at the epoch t2 after the time interval Δt, the vehicle position measurement system 2 receives the satellite signal 7 (7b) from the GPS satellite 6 (6b) moved during the time interval Δt. Based on the satellite signal received at this time, the pseudo distance L2 from the GPS satellite 6 (6b) to the train 4 (4b) and the Doppler shift frequency fd2 based on the relative moving speed of both can be obtained.

  Here, two parameters are considered in relation to the moving distance of the train 4 moved during the time interval Δt. 1) pseudo-range change ΔL, and 2) relative movement ΔD between the GPS satellite 6 and the train 4.

  The pseudo distance change amount ΔL is obtained from the difference between the pseudo distance L2 in the latest epoch t2 (second epoch) and the pseudo distance L1 in the past epoch t1 (first epoch) closest in time (first epoch) ( Formula A) in FIG.

  The relative movement distance ΔD is a) the average value of the Doppler shift frequency fd2 at the latest epoch t2 (second epoch) and the Doppler shift frequency fd1 at the past epoch t1 (first epoch) closest in time. B) Obtain the product of the carrier wave wavelength λ of the satellite signal and c) the time interval Δt of the epoch from the latest epoch t2 to the nearest epoch t1 in time, and reverse the sign (Formula B in FIG. 2).

  If the Doppler shift frequency fdi (i = 1, 2,...) Is in principle less susceptible to multipath than the pseudorange Li (i = 1, 2,...). Assuming that there is no error and other error factors are not taken into account, the pseudo distance change amount ΔL and the relative movement amount ΔD should match. On the other hand, if it is affected by the multipath, the difference between the pseudo distance change amount ΔL and the relative movement amount ΔD becomes large.

In order to calculate the position coordinates, at least four GPS satellites are necessary. If the number is large, the position coordinates can be calculated with high accuracy and high speed. Since four or more GPS satellites are always arranged in the sky, it is possible to select a GPS satellite to be used for positioning.
Therefore, in the present embodiment, the difference between the pseudo distance change amount ΔL and the relative movement amount ΔD, that is, the deviation amount Qe (formula C in FIG. 2) is obtained for each candidate GPS satellite (candidate satellite). The influence of multipath is reduced by selecting a satellite to be used for positioning using the deviation amount Qe. Specifically, in this embodiment, “determination reference value k” is set as the upper limit of an allowable error including multipath error, and if the deviation amount Qe is larger than the determination reference value k, it is strongly influenced by multipath. Therefore, it is excluded from the satellite candidates used for positioning.

  The first epoch and the second epoch can reduce the influence of the multipath with the highest accuracy when the difference is one epoch.

[Description of functional configuration]
FIG. 3 is a block diagram illustrating a functional configuration example of the vehicle position measurement system 2 according to the present embodiment. The CPU 24 of the vehicle position measurement system 2 includes a baseband processing unit 30, a deviation amount calculation unit 32, a determination reference value selection unit 34, a satellite selection unit 36, and a positioning calculation unit 38.

  The baseband processing unit 30 captures and tracks satellite signals and decodes navigation messages. The baseband processing unit 30 includes a capturing unit 301, a pseudo distance calculating unit 303, and a Doppler shift frequency calculating unit 305. The decoded navigation message is stored in the IC memory 26 (navigation message 44).

  The capturing unit 301 captures satellite signals of GPS satellites (candidate satellites) that are candidates for use in positioning. For example, the position of each GPS satellite is predicted and calculated based on the acquired navigation message 44, a C / A code (replica code) of the GPS satellite within the visible range is generated, and the correlation value with the digital IF signal is a peak. The C / A code phase control is performed as follows.

  The pseudo distance calculation unit 303 calculates a pseudo distance Li (i = 1, 2,...) For each GPS satellite that has been captured. The calculation method of the pseudo distance is the same as a conventionally known method. For example, the pseudo distance may be obtained from the difference between the transmission time indicated in the received GPS satellite signal and the reception time based on the time measured by the RTC 27. The calculated pseudo distance Li (i = 1, 2,...) Is identified in the pseudo distance history data 48 of the IC memory 26 by the satellite ID and the epoch ID (for example, the time indicated by the epoch or the serial number from the start. Information) and stored.

  The Doppler shift frequency calculation unit 305 calculates a Doppler shift frequency fdi (i = 1, 2,...) For each GPS satellite that has been captured. The calculation method of the Doppler shift frequency is the same as a conventionally known method. For example, the carrier frequency (1.57542 [GHz]) may be subtracted from the reception frequency of the captured satellite signal. The calculated Doppler shift frequency fdi (i = 1, 2,...) Is stored in the Doppler shift frequency history data 50 of the IC memory 26 in association with the satellite ID and the epoch ID.

  In this embodiment, the baseband processing unit 30 is configured to be realized by arithmetic processing of the CPU 24. However, hardware such as a known baseband processing IC is used, and the baseband processing unit 30 is a processor independent of the CPU 24. Can also be realized.

  The divergence amount calculation unit 32 includes (1) a pseudo distance change amount ΔL based on the calculated pseudo distance Li (i = 1, 2,...) And (2) a calculated Doppler shift for each captured GPS satellite. A deviation amount Qe which is a difference between the relative movement amount ΔD between the GPS satellite and the vehicle based on the frequency fdi (i = 1, 2,...) And (3) the pseudo-range change amount ΔL and the relative movement amount ΔD. And are calculated.

  The determination reference value selection unit 34 selects a determination reference value from among the determination reference values for determining the deviation amount Qe. In the present embodiment, the train 4 traveling on the track 3 is cited as an example of the vehicle. Therefore, a “zone” is determined in advance along the trajectory 3, and judgment reference value setting data 42 that defines a judgment reference value k for each zone is stored in the IC memory 26. Then, the determination reference value selection unit 34 selects, from the determination reference value setting data 42, the determination reference value k of the area corresponding to the position coordinate of the train 4 calculated last.

The satellite selection unit 36 selects a satellite to be used for positioning from GPS satellites (candidate satellites) that can be captured using the deviation amount Qe. Specifically, the deviation amount Qe obtained for each candidate satellite is compared with the determination reference value k selected by the determination reference value selection unit 34, and a candidate satellite having the deviation amount Qe equal to or larger than the determination reference value k is not selected. .
More specifically, in this embodiment, the satellite IDs of candidate satellites whose divergence amount Qe is equal to or greater than the determination reference value k are registered in the excluded satellite list 60. On the other hand, when the satellite ID of the candidate satellite having the deviation amount Qe less than the determination reference value k is registered in the excluded satellite list 60, the registration is deleted. The satellite selection unit 36 selects satellites to be used for positioning excluding candidate satellites registered in the excluded satellite list 60.

  The positioning calculation unit 38 calculates position coordinates from the satellite signals of the GPS satellites selected as the satellites used for positioning by the satellite selection unit 36 and stores the position coordinates 62 in the IC memory 26.

  The IC memory 26 can be realized by a volatile and non-volatile IC memory. The IC memory 26 of the present embodiment includes a positioning program 40, determination reference value setting data 42, navigation message 44, pseudorange history data 48, Doppler shift frequency history data 50, excluded satellite list 60, position coordinates. 62 is stored.

  The positioning program 40 is read and executed by the CPU 24, thereby realizing functions as a baseband processing unit 30, a deviation amount calculation unit 32, a determination reference value selection unit 34, a satellite selection unit 36, and a positioning calculation unit 38. It is a program. In the case where the baseband processing unit 30 is configured as a hardware circuit, the positioning program 40 functions as a deviation amount calculation unit 32, a determination reference value selection unit 34, a satellite selection unit 36, and a positioning calculation unit 38. Can be realized as a program for realizing the above, or as a dedicated circuit.

  The determination reference value setting data 42 defines a determination reference value for determining the deviation amount Qe. For example, as shown in FIG. 4, the satellite azimuth condition 423 and the determination reference value 425 are stored in association with each area 421. The area 421 defines, for example, a distance from a certain station (α station) and a range of position coordinates. The satellite azimuth condition 423 may be defined as an azimuth range (for example, −30 ° to + 30 °) based on the traveling direction of the vehicle, or may be defined based on east, west, south, and north.

  The navigation message 44 is data obtained by decoding the received GPS satellite signal, and includes satellite orbit information of each GPS satellite. In addition, it is good also as acquiring the initial navigation message 44 before starting a positioning, or only the satellite orbit information included in it from the exterior via communication I / F28.

  The pseudo distance history data 48 stores the history of the pseudo distance L for each GPS satellite. For example, as shown in FIG. 5, the satellite ID 481 and the pseudo distance value 485 associated with the epoch ID 483 are stored. For the epoch ID 483, for example, a measurement time can be used.

  The Doppler shift frequency history data 50 stores the history of the Doppler shift frequency fd for each GPS satellite. For example, as shown in FIG. 6, the satellite ID 501 and the Doppler shift frequency value 505 associated with the epoch ID 503 are stored.

The excluded satellite list 60 registers satellite IDs determined to be unsuitable for use in positioning.
In the present embodiment, the divergence amount Qe and the determination reference value k are compared for each GPS satellite, and if it is equal to or greater than the determination reference value k, the satellite ID of the GPS satellite is registered. If it is less than the criterion value k, the registration is deleted. Note that the satellite ID may be registered when the determination reference value k is exceeded, and the satellite ID registration may be deleted when the determination reference value k or less. The point is that the criterion value k is a threshold value.

The position coordinates 62 are position coordinates of the vehicle (the train 4 in this embodiment).
In addition, it is assumed that the IC memory 26 can store various information necessary for baseband processing.

[Description of operation]
Next, as a description of the operation of the vehicle position measurement system 2 in the present embodiment, the flow of positioning related processing in the CPU 24 will be described. The decoding / updating of the navigation message 44 can be realized in the same manner as a known positioning technique using GPS, and therefore the description thereof is omitted here. In addition, immediately after the power is turned on, the navigation message 44 is reacquired, the position of the visible GPS satellite 6 is predicted, and a search for a satellite signal from the satellite is performed. Since it is realizable, explanation is omitted.

  FIG. 7 is a flowchart for explaining the flow of processing for performing positioning once in the CPU 24, and is repeatedly executed at the same cycle as the epoch time difference while the vehicle position measurement system 2 is activated. .

  In the process, the CPU 24 first executes a GPS satellite 6 capturing process (step S2). For example, when the correlation between the digital IF signal (received signal) input from the RF receiver 22 and the replica code is performed while changing the replica code determined for each GPS satellite, and the correlation is obtained, the corresponding GPS It is determined that the satellite signal has been captured.

Next, the CPU 24 executes a loop A for each captured GPS satellite 6 (steps S4 to S36).
In the loop A, first, the pseudo distance L at the current epoch of the GPS satellite 6 to be processed is calculated and stored in the pseudo distance history data 48 (step S8; see FIG. 5). Next, the Doppler shift frequency fd in the current epoch of the GPS satellite 6 to be processed is calculated and stored in the Doppler shift frequency history data 50 (step S10; see FIG. 6).

Next, the pseudo distance change amount ΔL is calculated (step S12).
2, the pseudo distance L newly calculated in step S8 is referred to as “pseudo distance L2” in the second epoch, and the “temporal distance” registered in the pseudo distance history data 48 is changed. The pseudo distance change ΔL is calculated by setting the pseudo distance value 485 in the “nearest past epoch” as the “pseudo distance L1” in the first epoch.

  If the pseudo distance can be calculated in the immediately preceding epoch, the pseudo distance change ΔL is calculated based on the pseudo distance in the immediately preceding epoch. Even if the GPS satellite could not be captured temporarily, such as when passing through the overpass in the previous epoch, if the pseudorange can be calculated in the epoch in the past, the pseudorange change amount ΔL can be calculated. However, there is a case where there is no pseudo distance 485 corresponding to “the past epoch closest in time” immediately after exiting from a situation where the GPS satellite 6 cannot be captured for a long time, such as during a cold start or through a long tunnel. . In this case, the pseudo distance change amount ΔL cannot be calculated in step S12. Therefore, if the pseudo distance change amount ΔL cannot be calculated (NO in step S14), the satellite ID of the GPS satellite 6 to be processed is registered in the excluded satellite list 60 (step S16), and the loop A is terminated (step S16). S36).

If the pseudo distance change amount ΔL can be calculated in step S12 (YES in step S14), the CPU 24 then calculates the relative movement amount ΔD (step S20).
2, the Doppler shift frequency fd newly calculated in Step S10 is set to “Doppler shift frequency fd2” in the second epoch, and is registered in the Doppler shift frequency history data 50. The Doppler shift frequency value 505 in the past epoch closest in time is set as the “Doppler shift frequency fd1” in the first epoch, and the epoch time difference Δt is set as the time difference between the current epoch and the past epoch closest in time. The relative movement distance ΔD is calculated.

  If the relative movement distance ΔD cannot be calculated for the same reason as the calculation of the pseudo distance change ΔL (NO in step S22), the CPU 24 adds the satellite ID of the GPS satellite 6 to be processed to the excluded satellite list 60. Registration is performed (step S16), and loop A is terminated (step S36).

  If the relative movement distance ΔD can be calculated (YES in step S22), the CPU 24 next calculates a deviation amount Qe for the GPS satellite 6 to be processed (step S24; see formula C in FIG. 2). .

Next, referring to the determination reference value setting data 42, the corresponding area 421 is determined from the position coordinate 62 calculated last, and the direction of the GPS satellite 6 to be processed is determined based on the satellite orbit information included in the navigation message 44. A corresponding satellite orientation condition 423 is selected. Then, the selected determination reference value 425 is set as a determination reference value k used for the current determination (step S26; see FIG. 4).
Then, the determination reference value k is compared with the deviation amount Qe. If the deviation amount Qe is equal to or larger than the determination reference value k (YES in step S28), the CPU 24 excludes the satellite ID of the GPS satellite 6 to be processed as an excluded satellite. It registers in the list 60 (step S16) and ends the loop A (step S36). If the deviation amount Qe is less than the determination reference value k (NO in step S28), the CPU 24 deregisters the satellite ID of the GPS satellite 6 to be processed from the excluded satellite list 60 (step S30), and loops A. The process ends (step S36).

  If the loop A is executed for all the GPS satellites 6 acquired in step S2, the CPU 24 excludes the satellites registered in the excluded satellite list 60 from the acquired GPS satellites 6, and then the predetermined number. A satellite to be used for positioning is selected (step S40). If a predetermined number of satellites necessary for positioning cannot be selected here (NO in step S44), the process returns to step S2 without performing positioning calculation. If a predetermined number of satellites can be selected (YES in step S44), the position calculation in the current epoch is calculated by using the selected satellites and stored in the IC memory 26 in the position coordinates 62. (Step S46).

  As described above, according to the present embodiment, the influence of the multipath is obtained from the divergence between the pseudo distance change amount that is easily affected by the multipath and the relative movement amount based on the Doppler shift frequency that is not easily affected by the multipath. It is possible to test whether or not you have received

Further, in the present embodiment, since the history data of the pseudo distance and the Doppler shift frequency is held, the pseudo distance change ΔL is set to the pseudo distance in the latest epoch and the pseudo epoch in the past epoch closest to the epoch. It can be calculated from the distance. Further, the relative movement amount ΔD can be calculated by acquiring the Doppler shift frequency in the past epoch.
Therefore, it is possible to accurately test the influence of multipath based on the pseudorange and Doppler shift frequency between epochs that are continuous in time. Even if there are epochs that were temporarily unable to receive radio waves from GPS satellites singly or multiple times, such as when passing through an overpass, the pseudo- Since the relative movement distance ΔD can be calculated based on the time difference Δt up to the past epoch with reference to the Doppler shift frequency, it is possible to continuously realize the multipath effect test.

[Modification]
As described above, the embodiment to which the present invention is applied has been described. However, the embodiment of the present invention is not limited to this, and additions, omissions, and changes of components can be appropriately made.

[Part 1]
For example, in the above-described embodiment, the satellites that are not used for the positioning calculation are screened out by comparing the deviation amount Qe with the determination reference value k. However, the setting of the determination reference value k may be omitted. For example, the divergence amount calculation unit 32 may be configured to store the divergence amount Qe calculated for each GPS satellite in the IC memory 26, and may be configured to select satellites used for positioning calculation in order from the smaller stored divergence amount Qe. It is.

  Specifically, the divergence amount calculation calculation unit 32 stores the divergence amount history data 64 for each satellite in the IC memory 26 as shown in FIG. The divergence amount history data 64 stores the epoch ID 643 and the divergence amount value 645 calculated in the epoch in association with each satellite ID 641.

  As shown in FIG. 9, instead of steps S16 and S26 to S30, (1) the deviation amount Qe calculated in step S24 is stored in the deviation amount history data 64 corresponding to the GPS satellite to be processed in loop A. (2) When a negative determination is made at step S14 and when a negative determination is made at step S22, a predetermined value (for example, NULL) is set in the deviation amount history data 64 corresponding to the processing target GPS satellite in loop A. Step S34 of storing is executed.

Next, after the processing of loop A, the GPS satellites of a predetermined number (four or more, for example, five or four) may be used in order from the smallest divergence amount Qe in the latest (current) epoch. Is selected (step S42). Then, the position coordinates are calculated using the satellite signal of the selected GPS satellite (step S46).
In this case, the deviation amount Qe is an index value indicating whether or not to select a GPS satellite.

[Part 2]
In the above-described embodiment, the GPS has been described as an example of the satellite positioning system. However, the present invention can be applied to a satellite positioning system other than the GPS.
Moreover, although the vehicle is a train, it can also be applied to an automobile.

2 ... Vehicle position measurement system 3 ... Track 4 ... Train 6 ... GPS satellite 7 ... Satellite signal 21 ... GPS antenna 22 ... RF receiver 24 ... CPU
26 ... IC memory 28 ... Communication I / F
DESCRIPTION OF SYMBOLS 30 ... Baseband process part 301 ... Acquisition part 303 ... Pseudo distance calculation part 305 ... Doppler shift frequency calculation part 32 ... Deviation amount calculation part 34 ... Judgment reference value selection part 36 ... Satellite selection part 38 ... Positioning calculation part 40 ... Positioning program 42 ... Determination reference value setting data 44 ... Navigation message 48 ... Pseudo-range history data 50 ... Doppler shift frequency history data 60 ... Excluded satellite list 62 ... Position coordinates 64 ... Deviation amount history data

Claims (2)

A vehicle position measurement method for measuring the position of a vehicle based on a satellite signal received from a satellite,
A capture step for capturing satellite signals of each candidate satellite;
A pseudorange calculating step for calculating a pseudorange related to the captured satellite signal;
A Doppler shift frequency calculating step for calculating a Doppler shift frequency related to the captured satellite signal;
For each of the candidate satellites, 1) calculating the pseudorange variation from the difference between the pseudorange calculated in the first epoch and the pseudorange calculated in the second epoch, and 2) in the first epoch Using the calculated Doppler shift frequency, the average frequency of the Doppler shift frequency calculated in the second epoch, and the time interval between the first epoch and the second epoch, the candidate satellite and the vehicle A divergence amount calculating step of performing a calculation of a relative movement amount, and 3) calculating a divergence amount that is a difference between the pseudo distance change amount and the relative movement amount ;
A satellite selection step of selecting a predetermined number of the candidate satellites as satellites to be used for positioning from the candidate satellites in ascending order of the deviation amount ;
A positioning step of positioning based on the satellite signal of the selected satellite;
A vehicle position measuring method including: A vehicle position measurement system that measures the position of a vehicle based on a satellite signal received from a satellite,
A capture unit for capturing satellite signals of each candidate satellite;
A pseudorange calculator for calculating a pseudorange related to the captured satellite signal;
A Doppler shift frequency calculation unit for calculating a Doppler shift frequency related to the captured satellite signal;
For each of the candidate satellites, 1) calculating the pseudorange variation from the difference between the pseudorange calculated in the first epoch and the pseudorange calculated in the second epoch, and 2) in the first epoch Using the calculated Doppler shift frequency, the average frequency of the Doppler shift frequency calculated in the second epoch, and the time interval between the first epoch and the second epoch, the candidate satellite and the vehicle A divergence amount calculation unit that executes the following: 3) calculating a relative movement amount; and 3) calculating a divergence amount that is a difference between the pseudo distance change amount and the relative movement amount ;
A satellite selecting unit that selects a satellite to be used for positioning a predetermined number of said candidate satellites in the ascending order of the deviation amount from among the candidate satellites,
A positioning unit for positioning based on the satellite signal of the selected satellite;
A vehicle position measurement system.

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