JPH04364491A - Position of driver's own vehicle recognizing apparatus - Google Patents

Abstract

PURPOSE:To utilize the range of GPS position measurement precision effectively and to detect the current position of a vehicle with improved correctness. CONSTITUTION:A GPS receiver 10 is provided with a DOP specifying element 11 for specifying the GPS position measurement precision, a satellite combination determining element 12 and a satellite combination specifying element 13 for selecting satellites of specified DOP, and a satellite signal receiving element 14 and an absolute position calculating element 15 for calculating the absolute position of a vehicle by utilizing radio wave signals received from the selected satellites. On the other hand, a driver's own vehicle position determining element 20 is provided with a current place estimating element 21 having an azimuth sensor 31 and a distance sensor 32 connected therefor and realizing dead reckoning, a GPS use determining element 23 and a DOP specifying element 24 for relaxing the specification of DOP when the combination of the satellites of the specified DOP is not present, and a comparing element 22 for comparing GPS for which the specification of the DOP is relaxed with the dead reckoning and selecting the one having a smaller error.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is mounted on a vehicle and detects the current position of the vehicle using radio wave signals received from each of three or more satellites out of a plurality of satellites orbiting the earth. The present invention relates to a self-vehicle position recognition device.

0002

[Prior Art] Japanese Patent Application Laid-open No. 61-209316 states:
2. Description of the Related Art A route guidance device for a vehicle is disclosed that can accurately detect the point in time when a vehicle passes through each intersection by accumulating the distance traveled starting from each intersection. This guidance device utilizes a navigation method that detects a relative position from a reference point, that is, a navigation method called dead reckoning navigation or autonomous navigation. However, when only dead reckoning navigation is used to recognize the vehicle's position, large cumulative errors are unavoidable. Therefore, a method of navigation that detects the absolute position of the vehicle using radio signals from multiple satellites launched into orbit around the earth, namely satellite navigation (Global Position Navigation).
ning System: Abbreviated as GPS. ) has already been used to correct the estimated position by dead reckoning.

[0003] When the GPS system is completed, there will be six circular orbits (orbital radius of about 26,600 km) with different ascending nodes and right ascension.
A total of 24 satellites will be placed, 4 at the top, so that four or more satellites are always within sight anywhere on the earth. The period of each satellite orbiting the earth is approximately 11 hours and 58 minutes.

[0004] Each satellite transmits to the ground a radio wave signal containing the latest orbit information and extremely accurate transmission time information based on an atomic clock. There are 4 GPS receivers installed in the vehicle.
It receives the radio wave signals of each satellite and calculates the three-dimensional position of each satellite at that moment from the orbit information. The time required for the signal to arrive, that is, the pseudo distance between each satellite and the vehicle's position (at this stage, it is not an accurate distance value, so it is called a pseudo distance) is determined. Then, four spherical surfaces are set with each satellite as the center and each pseudo distance from the center as the radius. However, the internal clock of the GPS receiver does not perfectly match the satellite's atomic clock, so the four spherical surfaces do not intersect at one point. Therefore, by correcting the internal clock so that the four spherical surfaces intersect at one point, the pseudo distance is corrected, and at the same time the internal clock is adjusted, the intersection point of the four spherical surfaces, that is, the absolute position of the vehicle is calculated. be. However, since the vehicle is located on the earth, positioning can be performed using radio signals from only three satellites.

[0005] The above-described GPS positioning results include some errors, and the positioning errors vary depending on the placement in the sky of the satellites used for position detection. For example, if satellites are unevenly distributed in a particular direction in the sky, positioning accuracy will deteriorate. Therefore, with GPS, DO
P (Dilution of Precision
) is defined as a measure of how much influence the placement of satellites has on positioning accuracy. The combination of satellites that minimizes the DOP value is adopted.

FIG. 4 is a time chart showing actually measured data of changes in DOP value over time. Since the arrangement of satellites changes from moment to moment, the DOP value also changes accordingly. When a vehicle goes behind a mountain or a building, radio signals from satellites at low altitudes that could be received are blocked, which limits the usable range of the satellites and changes the DOP value. A situation in which positioning cannot be determined may also occur.

[0007] DOP is an amount that can be determined by a GPS receiver from the geometrical arrangement of available satellites, but there is also SVACC (Spac) in the radio signal transmitted by each satellite.
It includes information that is a measure of positioning accuracy called eVehicle Accuracy. If the value of SVACC is N (0<N<15), the positioning error e (unit:
m) is determined by the following formula in combination with the DOP value.

[0008] e=DOP・X However, when 0<N<6, X=2(1+N/2)
, when 6≦N<15, X=2(N-2).

For example, when the DOP value is 4 and the SVACC value is 6, e=4×2(6-2)=4×16=64, and 64
It turns out that there is a positioning error of m. SVACC value is 4
~5, the positioning error will be about 40 m when the DOP value is 4, about 100 m when the DOP value is 10, and about 200 m when the DOP value is 20.

[0010] Conventionally, due to the relationship with so-called map matching technology, the actual situation was that GPS was used only when the DOP value was 4 or less and the SVACC value was 8 or less, and the position was determined based on these values. Three or more satellites that enable position detection with accuracy higher than the positioning accuracy are selected, and the current position of the vehicle is calculated using radio signals received from each of the selected satellites.

[0011]

[Problems to be Solved by the Invention] As mentioned above, in the conventional vehicle position recognition device, the DOP value is 4 or less and the SVACC
Since GPS was used only when the condition that the value was 8 or less was satisfied, only dead reckoning navigation was used during the time period when GPS was not used. In dead reckoning, the relative position of the vehicle is estimated based on a direction sensor such as a geomagnetic sensor and a distance sensor such as a wheel speed sensor.

FIG. 5 shows the CRT when only dead navigation is used because the conditions of DOP value being 4 or less and SVACC value being 8 or less are not satisfied in a conventional vehicle position recognition system.
FIG. 3 is a plan view showing an example of a travel trajectory displayed on a map screen of a monitor. This vehicle position recognition device momentarily displays the current location and direction of the vehicle as an arrow-shaped current location mark 52 on a map screen including a road display 51, and sequentially displays the travel trajectory as a trajectory mark 53. It is something. However, the estimated position by dead reckoning usually has an error of 5 to 10%. When passing through a tunnel with large geomagnetic disturbances or traveling on a streetcar line, the vehicle body may become magnetized and the direction sensor may go awry, and the position detection error due to dead reckoning may exceed 10%. 10%
As shown in the figure, if there is an error of
The current location mark 52 will be displayed as if it is 1 km away from 4.

On the other hand, reference numeral 55 in the figure is a circle with a constant DOP value representing a positioning error when absolute position detection by GPS is assumed, that is, a DOP area.
The case where the positioning accuracy of S is lowered and the DOP upper limit value is set to 20 is shown. The radius of this DOP area 55 is 200m
, the current location mark 5 obtained only by dead reckoning
2 has gone outside the DOP area 55. In other words, even though using GPS with DOP20 would have provided more accurate position detection than dead reckoning, even in such cases, until now the conditions of DOP value of 4 or less and SVACC value of 8 or less were met, GPS was not used.

[0014] An object of the present invention is to make effective use of GPS and to more accurately detect the current position of a vehicle.

[0015]

[Means for Solving the Problems] In order to achieve the above object, the present invention actively utilizes the positioning accuracy range of GPS, which has not been utilized in the past.

[0016] To explain specifically, the invention of claim 1 is as follows:
This vehicle position recognition device is mounted on a vehicle and detects the current position of the vehicle using radio signals received from each of three or more satellites out of multiple satellites orbiting the earth. Accuracy specification means for specifying the positioning accuracy when detecting the current position of the vehicle, and a position having an accuracy higher than the specified positioning accuracy among the plurality of satellites in orbit around the earth. satellite selection means for selecting three or more satellites that enable detection; position calculation means for calculating the current position of the vehicle using radio signals received from each of the selected satellites; The present invention employs a configuration including accuracy correction means for lowering the positioning accuracy designation of the accuracy designation means when there is no satellite selected by the selection means.

[0017] The invention according to claim 2 also includes a dead reckoning means for estimating the current position of the vehicle without using radio signals from the satellite; If the current position of the vehicle estimated by the dead reckoning means is within the error range of the lowered positioning accuracy, the current position of the vehicle estimated by the dead reckoning means is outside the lowered error range of the positioning accuracy. In this case, a configuration is adopted which further includes recognition result selection means for selecting the current position of the vehicle calculated based on the lowered positioning accuracy.

[0018]

[Operation] According to the invention of claim 1, the current position of the vehicle is recognized by selecting three or more satellites whose positioning accuracy is higher than a predetermined positioning accuracy, and the satellites whose positioning accuracy is higher than the predetermined positioning accuracy are selected. If a combination does not exist, the current position of the vehicle is calculated based on a combination of satellites with lower positioning accuracy. By switching the positioning accuracy to two levels in this way, it is possible to effectively utilize GPS while maintaining consistency with map matching technology.

Further, according to the invention of claim 2, when there is no combination of satellites that achieves a predetermined positioning accuracy or higher, the satellite navigation comprising the accuracy designation means, the satellite selection means, the position calculation means, and the accuracy correction means. The lowered positioning accuracy of the means and the position estimation accuracy of the dead reckoning means are compared, and the current position of the vehicle determined by the satellite navigation means and the current position of the vehicle estimated by the dead reckoning means are calculated based on the lowered positioning accuracy. The one closest to the true vehicle position is selected.

[0020]

Embodiment FIG. 1 is a block diagram showing the configuration of a vehicle position recognition device according to an embodiment of the present invention. As shown in the figure, this vehicle position recognition device includes a GPS receiver 10 and a vehicle position determining section 20.

[0021] The GPS receiver 10 includes a DOP designation section 11,
It includes a satellite combination determination section 12, a satellite combination instruction section 13, a satellite signal reception section 14, and an absolute position calculation section 15. DOP
The specifying unit 11 constitutes an accuracy specifying means for specifying the positioning accuracy when detecting the current position of the vehicle, and normally sets the DOP upper limit to 4, for example. The satellite combination determination unit 12 and the satellite combination instruction unit 13 select three or more satellites that enable position detection with accuracy that satisfies the DOP conditions specified by the DOP specification unit 11 from among the plurality of satellites in orbit around the earth. A satellite selection means for selection is configured. Satellite signal receiver 1
4 and the absolute position calculation unit 15 constitute a position calculation means for calculating the current absolute position of the vehicle using radio signals received from each of the selected satellites.

[0022] The own vehicle position determination unit 20 includes a current location estimation unit 21
, a comparison section 22, a GPS use determination section 23, and a DOP instruction section 24. A direction sensor (a geomagnetic sensor, a wheel rotation sensor attached to each of the left and right wheels, a switch for distinguishing between forward and backward directions) 31 and a distance sensor (wheel speed sensor) 32 are connected to the current location estimating unit 21. A dead reckoning means for relatively estimating the current position of a vehicle without using radio signals from a satellite is configured. The GPS use determination unit 23 and the DOP instruction unit 24 determine the DOP specification unit 11 when there is no combination of satellites with a DOP value of 4 or less.
Precision correction means is configured to change the OP upper limit setting from 4 to 20, for example. The comparison unit 22 compares the positioning accuracy of the GPS absolute position calculation result obtained by the absolute position calculation unit 15 and the estimation accuracy of the relative position estimation result obtained by the current location estimation unit 21, and selects the true one of both results. A recognition result selection means is configured to select the one closer to the own vehicle position. This comparison section 22 includes a display section 33 consisting of a CRT monitor.
is connected, and the display unit 33 displays the current location of the own vehicle on the map screen from time to time based on the output of the comparison unit 22.

FIG. 2 is a flowchart showing the operation of the vehicle position recognition device according to the present embodiment described above. The operation of the vehicle position recognition device shown in FIG. 1 will be sequentially explained with reference to the same figure.

As shown in FIG. 2, in step S1, it is checked whether the output of the absolute position calculation section 15 of the GPS receiver 10, which has the normal value 4 as the DOP upper limit value, has been used. GPS
If you are using , continue the operation. If GPS is not used, set the DOP upper limit to 4 in step S2.
Find out if it is a time when you can use GPS. D
If it is not the time zone in which GPS can be used in OP4, the process advances to step S4 and the designation of the DOP upper limit value is changed to 20. However, even during times when GPS can be used in DOP4, there are cases where the vehicle is behind mountains or buildings and the radio signals from satellites at low altitudes that should be received are blocked. After confirming that the GPS has not been used within the time, the DOP upper limit value is changed to 20 in step S4.

When switching to the DOP 20 as described above, first, in step S5, it is checked whether the current location displayed based on the output of the current location estimating section 21 is within the DOP area. D
As mentioned above, the OP area is a circle with a constant DOP value representing the positioning error by GPS, and is considered to be a circle with a radius of 200 m corresponding to a DOP of 20. Current location estimation part 2
If the current location display based on the output of step 1 is within the DOP area, step S6 is skipped and the process proceeds to step S7. On the other hand, if the current location display based on the output of the current location estimating unit 21 goes outside the DOP area as in the case shown in FIG. After changing to the output of the unit 15, that is, the GPS position, the process proceeds to step S7. In step S7, the DOP4 checks again whether or not it is a time zone in which GPS can be used, and if the time zone has not returned yet, the operations of the DOP20 in steps S5 and S6 are continued. If the time has returned to the time zone in which GPS can be used with DOP4, the DOP designation is returned to 4 in step S8, and the process returns to step S1.

According to the vehicle position recognition device according to the present embodiment described above, the current position of the vehicle is recognized by selecting three or more satellites whose DOP value is 4 or less, and the DOP value is If there is no combination of satellites that is 4 or less, DOP
The current position of the vehicle is calculated based on the combination of satellites with the lower limit value changed to 20. By switching the positioning accuracy to two levels in this way, it is possible to effectively utilize GPS while maintaining consistency with map matching technology. In addition, if there is no combination of satellites with a DOP value of 4 or less, the DOP lower limit value is changed to 20, and if the current location display based on the output of the current location estimation unit 21 is within the DOP area, the corresponding When the current location display is selected and the current location display goes outside the DOP area, the output of the absolute position calculation unit 15 based on GPS is used as the accurate current location display, so DOP4 to 20, which were not used in the past, are used.
This makes it possible to effectively utilize the GPS positioning accuracy range of , and to detect the current position of the vehicle more accurately.

[0027] In the above explanation, the case where the DOP upper limit value is changed to two levels, 4 and 20, has been explained.
It may be set to other values. GP constituting accuracy correction means
The S use determination section 23 and the DOP instruction section 24 may be built into the GPS receiver 10.

[0028] Furthermore, the upper limit value of SVACC may be switched together with the upper limit value of DOP or alone. When changing the SVACC upper limit value, use GPS for SVACC.
Since the time period during which SVACC can be used is not determined by the satellite configuration, it is necessary to check whether or not you have used GPS with a predetermined normal value as the upper limit of SVACC.
After confirming that SVACC is not being used, increase the SVACC upper limit. After lowering the GPS positioning accuracy by changing the SVACC upper limit in this way, the DOP
As in the case of changing the upper limit, the lowered positioning accuracy of GPS is compared with the position estimation accuracy by dead reckoning navigation, and the absolute position of the vehicle determined by GPS is estimated by dead reckoning based on the lowered positioning accuracy. The relative position of the vehicle is selected which is closer to the true position of the vehicle. However, the changed SVA will remain unchanged until the power of the own vehicle position recognition device is turned off.
Maintain CC upper limit.

[0029]In order for the driver to recognize the position of his/her own vehicle, information on the route the driver has taken so far is very effective. FIG. 3 is a plan view showing an example of a travel trajectory displayed on a map screen on the display unit 33 of the own vehicle position recognition device.

FIG. 3A shows a case where the display of the vehicle's position by dead reckoning navigation is corrected based on the detection results of the vehicle's absolute position by GPS at fixed time intervals. In this vehicle position recognition device, the current location and direction of the vehicle are displayed moment by moment as an arrow-shaped current location mark 42 on a map screen including a road display 41, and the travel trajectory is sequentially displayed as a trajectory mark 43. be done. Coordinates (X, Y) on the map screen in the same figure
are coordinates corrected using GPS, and are located exactly on the road display 41. However, this coordinate (X,
As a result of position detection error by dead reckoning based on Y),
Although the vehicle is actually traveling on the road, the trajectory mark 43 is off the road display 41 until it reaches the coordinates (X1, Y1), and the vehicle is actually traveling on the road.
) will be changed to the coordinates (X
2, Y2), the trajectory mark 43 returns to the top of the road display 41. As a result of this process, even though the vehicle is actually traveling straight on the road, the display of the travel trajectory becomes zigzag, which may even confuse the driver's recognition of the vehicle's position.

On the other hand, FIG. 6(b) shows a case where the vehicle position display is corrected and at the same time, the travel trajectory display within a certain range is also corrected. When correcting coordinates (X1, Y1) based on dead reckoning to accurate coordinates (X2, Y2) using GPS, the coordinates (X, Y) related to the previous GPS use are
From the coordinates (X, Y) to the coordinates (X1, Y
1) By rotating the travel trajectory based on dead reckoning navigation, the display position of the trajectory mark 44 is moved onto the road display 41. As a result, trajectory mark 4
4 are lined up on a straight line corresponding to the actual travel locus.

[0032]

[Effects of the Invention] As explained above, according to the invention of claim 1, the positioning accuracy is switched to two stages and the current position of the vehicle is detected using the radio signal from the selected satellite. , effective use of GPS can be achieved.

Further, according to the invention of claim 2, when there is no combination of satellites that achieves a predetermined accuracy or higher, the positioning accuracy of the satellite navigation means is lowered, and the position detection accuracy of the satellite navigation means and the dead reckoning means is lowered. Since a configuration is adopted in which the better one is selected, the current position of the vehicle can be detected more accurately by actively utilizing the GPS positioning accuracy range that has not been used in the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a vehicle position recognition device according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the own vehicle position recognition device of FIG. 1;

FIG. 3 is a plan view showing an example of a driving trajectory displayed on the map screen of the display unit in FIG. (b)
1 and 2 respectively show cases in which the traveling locus display within a certain range is also corrected at the same time as the correction.

FIG. 4 is a time chart diagram showing actually measured data of temporal changes in DOP values in GPS.

FIG. 5 is a plan view showing an example of a travel trajectory displayed on a map screen to explain the cumulative error in displaying the vehicle's position when only dead reckoning navigation is used.

[Explanation of symbols]

10...GPS receiver 11...DOP specifying section (accuracy specifying means) 12...Satellite combination determining section (satellite selecting means) 13...Satellite combination instructing section (satellite selecting means) 14...Satellite signal receiving section (position calculating means) 15... Absolute position calculation unit (position calculation means) 2
0...Vehicle position determination section 21...Current location estimation section (dead navigation means) 22...Comparison section (recognition result selection means) 23...GPS use determination section (accuracy correction means) 24...DOP
Indicator (accuracy correction means) 31... Orientation sensor (dead-reckoning means) 32... Distance sensor (dead-reckoning means) 33... Display parts 41, 51... Road display 42, 52... Current location mark 43, 44, 53... Trajectory mark 54 …True vehicle position 55…DOP area

Claims (2)

[Claims] Claim 1: Vehicle position recognition installed on a vehicle to detect the current position of the vehicle using radio signals received from each of three or more satellites out of a plurality of satellites in earth orbit. The device includes an accuracy specifying means for specifying the positioning accuracy when detecting the current position of the vehicle, and a position detecting means for specifying the positioning accuracy of the plurality of satellites in the earth orbit with an accuracy higher than the specified positioning accuracy. a satellite selection means for selecting three or more satellites to be enabled; a position calculation means for calculating the current position of the vehicle using radio signals received from each of the selected satellites; A self-vehicle position recognition device comprising: accuracy correction means for lowering the positioning accuracy designation of the accuracy designation means when there is no satellite selected by the selection means. 2. The own vehicle position recognition device according to claim 1, further comprising a dead reckoning means for estimating the current position of the vehicle without using the radio signal, and a dead reckoning means for estimating the current position of the vehicle without using the radio signal; If the position is within the error range of the lowered positioning accuracy, the current position of the vehicle estimated by the dead reckoning means is selected, and the current position of the vehicle estimated by the dead reckoning means is changed to the lowered positioning accuracy. An own vehicle position recognition device, further comprising recognition result selection means for selecting the current position of the vehicle calculated based on the lowered positioning accuracy when the positioning accuracy is outside the error range.