JP3859743B2 - Current position calculation device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a current position calculation device that is mounted on a moving body such as a vehicle and measures a travel distance, a traveling direction, and the like of the moving body, thereby calculating a current position of the moving body.
[0002]
[Prior art]
Conventionally, in a current position calculation device that calculates a current position of a vehicle traveling on a road, the current position of the vehicle is measured by a traveling direction of a vehicle measured by an orientation sensor such as a gyro and a vehicle speed sensor or a distance sensor. It is calculated based on the travel distance of the vehicle.
[0003]
The vehicle travel distance is generally measured by measuring the output shaft of the transmission or the rotation speed of the tire, and multiplying the rotation speed by the distance coefficient that is the distance the vehicle travels per rotation of the tire. It is demanded by.
[0004]
Further, in order to correct the error of the current position obtained from the traveling direction and the travel distance of the vehicle in this way, as described in JP-A-63-148115, the vehicle obtained so as to be matched with the road A so-called map matching technique for correcting the current position of the current position is known, and the accuracy of the current position calculation can be improved by this map mapping technique.
[0005]
[Problems to be solved by the invention]
However, it is necessary to execute a process for searching all roads located within a predetermined range with respect to the virtual current position of the vehicle, and the time required for this is the density of roads located within the predetermined range. In particular, when the road exists in an urban area, the processing time is remarkably increased. Furthermore, the processing time required to calculate the reliability of the current position candidate point on the road also becomes longer.
[0006]
The processing time for searching the road and the processing time for calculating the reliability are significantly increased, so that other processing to be performed by the device, for example, reading of direction sensor data, speed sensor or distance sensor There has been a problem in that it may not be possible to appropriately read data, or calculate the travel distance of a vehicle based on data from a vehicle speed sensor or a distance sensor.
[0007]
An object of the present invention is to provide a current position calculation device that can reduce the processing load without impairing the accuracy of map matching.
[0008]
[Means for solving the problems]
An object of the present invention is a current position calculation device that is mounted on a vehicle and calculates the current position of the vehicle,
Direction detection means for detecting the traveling direction of the vehicle;
A distance calculating means for calculating a travel distance of the vehicle;
Road data storage means for storing road data;
Based on the relative displacement obtained based on the travel direction and the travel distance, the current position of the vehicle is estimated as a virtual current position, the virtual current position is compared with the road data in the road data storage means, And a map matching means for calculating a candidate point of the current position together with a reliability indicating its credibility, and certifying the candidate point with the highest reliability as the current position,
The map matching means also performs estimation of the next virtual current position for candidate points other than the candidate point with the highest reliability and calculation of the candidate point associated therewith, from the position of the candidate point with the highest reliability. This is achieved by a current position calculation device that deletes candidate points that are separated by a predetermined distance or more.
[0009]
In this apparatus, the map matching means calculates the reliability of the candidate point obtained on the road based on the distance to the road around the virtual current position and the direction difference between the road direction and the vehicle direction. Can do.
[0010]
Whether or not the map matching means deletes a candidate point outside the road by using the virtual current position outside the road as a candidate point when a candidate point on the road corresponding to the virtual current position outside the road is not found It is also possible to set the predetermined distance used when determining whether or not to be smaller than a candidate point on the road.
[0011]
[Action]
In the map matching process, in principle, a virtual current position is calculated based on the newly calculated relative travel distance and traveling direction with respect to the current position of the vehicle, and the virtual current position is calculated as the road data in the vicinity. In contrast, a position on the road that is determined to be the most likely (highest reliability) is obtained, and this is recognized as the current position. However, in order to prevent erroneous recognition due to errors, the candidate point data other than the candidate point at the current position determined to be the most probable are not immediately discarded, and a new candidate point based on that candidate point is also calculated. Among these candidate points, the most likely candidate point is recognized as the current position.
[0012]
If data of candidate points other than the most probable candidate points is also held and new candidate points are obtained from these, there is a possibility that the data to be held increases considerably. This may impose an excessive processing load on the processor in executing the map matching process to be processed in real time. This problem is particularly noticeable in areas where roads are dense, such as urban areas. In the present invention, the distance from the candidate point having the highest reliability indicating the credibility given to the candidate point to the other candidate point is inspected, and when the distance is a predetermined amount or more, the other candidate point is determined. delete.
[0013]
As a result, while maintaining the reliability of the map matching process, it is possible to reduce the number of processing targets in the process, that is, the processing load, and reduce the time required for the process execution.
[0014]
In addition, in the map matching process, when a candidate point on the road corresponding to the virtual current position outside the road is not found, the virtual current position outside the road may be used as a candidate point (a candidate point in a free state). . The candidate point obtained from the virtual current position obtained next based on such a candidate point may be far away from the candidate point (display candidate point) having the highest reliability. The present invention is useful for reducing the processing load by deleting such candidate points.
[0015]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0016]
FIG. 1 is a block diagram showing a configuration of a current position calculation apparatus according to an embodiment of the present invention. As shown in FIG. 1, the current position calculation device 10 includes an angular velocity sensor 11 that detects a change in traveling azimuth by detecting a yaw rate of the vehicle, and a geomagnetic sensor 12 that detects a traveling azimuth of the vehicle by detecting geomagnetism. And a vehicle speed sensor 13 that outputs pulses at time intervals proportional to the rotation of the output shaft of the vehicle transmission.
[0017]
In addition, a display 17 that displays a map around the current position, a mark indicating the current position, and the like, a switch 14 that receives a command to switch the scale of the map displayed on the display 17 from a user (driver), and digital map data are stored. A CD-ROM 15 to be stored, and a driver 16 for reading map data from the CD-ROM 15 are provided. Moreover, the controller 18 which controls operation | movement of each peripheral apparatus shown above is provided. In the present embodiment, the digital map data described above includes road data composed of coordinates indicating the end portions of a plurality of line segments, road width data indicating the road width of the road, and roads that are expressways or general roads. An expressway flag indicating whether or not there is included.
[0018]
The controller 18 includes an A / D converter 19 that converts a signal (analog) of the angular velocity sensor 11 into a digital signal, an A / D converter 20 that converts a signal (analog) of the geomagnetic sensor 12 into a digital signal, and a vehicle speed sensor. A counter 26 that counts the number of pulses output every 13 seconds, a parallel I / O 21 that inputs whether or not the switch 14 is pressed, and a DMA that transfers map data read from the CD-ROM 15 ( (Direct Memory Access) controller 22 and display processor 23 for displaying a map image on display 17.
[0019]
The controller 18 further includes a microprocessor 24 and a memory 25. The microprocessor 24 outputs a signal from the angular velocity sensor 11 obtained through the A / D converter 19, a signal from the geomagnetic sensor 12 obtained through the A / D converter 20, and an output pulse from the vehicle speed sensor 13 counted by the counter 26. Number, whether or not the switch 14 is input via the parallel I / O 21, the map data from the CD-ROM 15 obtained via the DMA controller 22 is received, and processing based on these signals is performed. The current position is calculated and displayed on the display 17 via the display processor 23. As shown in FIG. 2, the vehicle position is displayed by superimposing an arrow mark or the like on a map already displayed on the display 17. Thereby, the user can know the current position of the vehicle on the map. The memory 25 includes a ROM that stores a program that defines the contents of processing (to be described later) for realizing such an operation, and a RAM that is used as a work area when the microprocessor 24 performs processing. Yes.
[0020]
Hereinafter, the operation of the current position calculation device 10 configured as described above will be described.
[0021]
The operation of the apparatus 10 generally includes processing for calculating the traveling direction and distance of the vehicle, processing for determining the current position of the vehicle from the calculated traveling direction and distance, and displaying the obtained vehicle position and direction. Since these can be divided into three processes, i.e., the process to be performed, these will be described in turn.
[0022]
FIG. 3 illustrates the flow of processing for calculating the traveling direction and travel distance of the vehicle.
[0023]
This process is a routine of the microprocessor 24 that is activated and executed at a constant cycle, for example, every 100 ms.
[0024]
In this routine, first, the output value of the angular velocity sensor 11 is read from the A / D converter 19 (step 301). Since an azimuth change is output as the output value of the angular velocity sensor 11, only a relative value in the traveling direction of the vehicle can be detected. Therefore, next, the output value of the geomagnetic sensor 12 is read from the A / D converter 20 (step 302), and the absolute azimuth calculated from the output value of the geomagnetic sensor 12 and the azimuth change output from the angular velocity sensor 11 ( The estimated azimuth of the vehicle is determined using (angular velocity output) (step 303).
[0025]
For example, when the vehicle speed is low for a long time, the angular velocity sensor has a large error. Therefore, when the vehicle speed is low for a certain time or more, the direction is determined by using only the geomagnetic sensor direction.
[0026]
Next, the number of pulses output from the vehicle speed sensor 13 is counted by the counter 26 every 0.1 second, and the counted value is read (step 304). By multiplying this read value by a distance coefficient, a distance advanced in 0.1 seconds is obtained (step 305).
[0027]
Next, the travel distance value per 0.1 second thus determined is added to the previously obtained value to check whether the travel distance of the vehicle has reached 20 m (step 306). If not satisfied (No in step 306), the current process is terminated and a new process is started.
[0028]
As a result of the travel distance calculation process, when the accumulated travel distance becomes a certain distance, for example, 20 m (Yes in Step 306), the traveling direction and the travel distance (20 m) at that time are output (Step S306). 307). In step 307, the accumulated distance is further initialized, and accumulation of the travel distance is newly started.
[0029]
Next, a process of calculating a virtual current position of the vehicle based on the calculated traveling direction and travel distance and obtaining a candidate point of the vehicle based on the calculated virtual current position will be described.
[0030]
FIG. 4 shows the flow of this process.
[0031]
This process is a routine of the microprocessor 24 that is activated and executed in response to the output of the traveling direction and travel distance from FIG. That is, this process is started every time the vehicle travels 20 meters.
[0032]
In this process, first, the sensor data output in the previous step 307, that is, the traveling direction and the travel distance are read (step 41).
[0033]
Next, map matching processing is performed (step 42). This includes a calculation process of the reliability of the candidate points, as will be described in detail later.
[0034]
Next, the position of the display candidate point which is the candidate point with the highest reliability obtained by this map matching process is set to variables X0 and Y0 (step 43).
[0035]
Therefore, one candidate point other than the display candidate points is taken out, and its position is set to variables X and Y (step 44). Next, a linear distance between the position (X0, Y0) and the position (X, Y) is obtained, and this value is set as the distance L (step 45). This distance L is compared with a predetermined threshold value Lth (step 46). This distance L is a value in the range of several kilometers to several hundred kilometers, for example. The value of L may be switched depending on whether a candidate point to which this is applied is a matching state or a free state described later. In this case, the L value for the free state candidate point is set lower than the L value for the candidate point in the matching state so that the free state candidate point is more easily deleted. This is because the reliability of the free state candidate points is low. Alternatively, it is possible to use different threshold values depending on the reliability of the candidate points (using a calculation formula or a conversion table) regardless of whether or not the free state is set.
[0036]
In step 46, if the distance L is less than or equal to the threshold value Lth, the process proceeds to step 48, and if greater than Lth, the process proceeds to step 47. In step 47, the candidate (and various information described later) is deleted from the memory. By this deletion, a process for obtaining a new candidate point from this candidate point in the next map matching process is omitted, and the processing load can be reduced.
[0037]
For all candidate points other than the display candidate points, the processing from step 44 is repeated, and this processing is terminated (step 48).
[0038]
FIG. 5 shows details of the map matching process.
[0039]
In the map matching process, first, the movement amount of the vehicle is obtained separately in the latitude and longitude directions. Furthermore, the movement amount in each direction is added to the position of the candidate point of the vehicle obtained in the process for obtaining the candidate point of the previous vehicle, and the virtual current position (the position where the current vehicle is estimated to exist) A) is obtained (step 421). Details of the candidate points will be described later. If there is no candidate point obtained by the process of obtaining the previous candidate point of the vehicle, such as immediately after the start of the device, the virtual current position is set using the position set separately as the position of the previously obtained candidate point. The position (A) is obtained.
[0040]
Next, the road data of the map around the obtained virtual current position (A) is read from the CD-ROM 15 via the driver 16 and the DMA controller 23 (step 422). At this time, if the candidate point used to obtain the virtual current position (A) is a candidate point on a road, it is a line segment representing the road or a line segment connected thereto, and from the virtual current position (A). A line segment within the distance search range D is selected. In the case of a candidate point that is not a candidate point on the road (a candidate point in a free state), a line segment within the distance search range D is selected from the virtual current position (A). At this time, the road search range D may be variable based on the reliability (corrected last time) regarding the candidate points used to obtain the virtual current position. That is, for a virtual current position obtained from a candidate point with high reliability, a line segment included in a narrower range is selected, and conversely, for a virtual current position obtained from a candidate point with low reliability, a wider range is selected. Select the line segment included in. The reason for making the search range variable based on the reliability is that if the reliability is low, the credibility of the accuracy of the current position obtained last time is considered to be low, so search the road by searching a wider range. This is because it is more suitable for obtaining the correct current position.
[0041]
As described above, in this embodiment, the road data is approximated by a plurality of line segments 51 to 55 connecting two points as shown in FIG. 6, and these line segments are represented by the start point and the end point. The one represented by coordinates is used. For example, the line segment 53 is represented by its start point (x3, y3) and end point (x4, y4).
[0042]
Next, from the line segments extracted in step 422, select only the line segment whose direction is within the predetermined traveling direction and the predetermined direction (step 423), and further extract the line segment. For all the n line segments, a perpendicular line is taken from the virtual current position (A), and the length of the perpendicular line L (n) is obtained (step 424).
[0043]
Next, an error cost value ec (n) defined by the following equation is calculated for all the line segments selected in step 423 based on the lengths of these perpendicular lines.
[0044]
ec (n) = α × | θcar−θ (n) | + β | L (n) |
Here, θcar is the vehicle direction at the virtual current position (A), θ (n) is the direction of the line segment, and L (n) is the distance from the virtual current position (A) to the line segment, that is, the length of the perpendicular line. , Α and β are weighting factors. The values of these weighting factors may be changed depending on whether the shift in the traveling direction or the direction of the road or the shift in the current position or the road is emphasized in selecting the road to which the current position belongs. For example, when importance is attached to a road whose direction is close to the traveling direction, α is increased.
[0045]
Here, explanation is added for each candidate point. In an initial state such as immediately after the start of the device, the virtual current position (A) is uniquely determined by the user (driver) inputting predetermined information using the switch 14 and the like. Is located on the line corresponding to the road. However, after the vehicle travels, the virtual current position (A) may not exist in the line segment corresponding to the road due to an error of a sensor such as a gyro. As a result, for example, as shown in FIG. 7, when the road is branched, that is, when two line segments 64 and 65 appear from the node 68 of the line segment 61 corresponding to the road, In many cases, it cannot be clarified whether a vehicle is present on the road corresponding to.
[0046]
Therefore, in such a case, in this embodiment, predetermined points existing on two possible line segments are set as candidate points, their current position, error cost, accumulated error cost described later, etc. Are respectively stored in a predetermined area of the RAM of the memory 25. For ease of explanation, in the following explanation, one or more new candidate points are generated from a single candidate point unless it is clearly indicated that there are a plurality of candidate points.
[0047]
Next, the accumulated error cost in the current process defined by the following equation according to the calculated error cost ec (n) and the accumulated error cost es related to the candidate point obtained in the previous process. es (n) is calculated (step 425).
[0048]
es (n) = (1-k) × es + k × ec (n)
Here, k is a weight coefficient larger than 0 and smaller than 1. This accumulated error cost es (n) represents how much the error cost calculated in the previous process is reflected in the error cost calculated in the current process.
[0049]
Further, based on the calculated accumulated error cost es (n), a reliability trst (n) defined by the following equation is calculated (step 452).
[0050]
trst (n) = 100 / (1 + es (n))
As is clear from this equation, as the accumulated error cost ec (n) increases, the reliability trst (n) decreases and approaches 0 (zero). On the other hand, as it decreases, the reliability trst (n) increases and its value approaches 100.
[0051]
By performing such processing, the reliability trst (n) related to n line segments existing within a predetermined range from the current position A with respect to a certain candidate point is obtained. The reliability is calculated for each selected line segment as described above, but in the present specification, for the sake of convenience, it is also treated as the reliability for a candidate point obtained on the line segment.
[0052]
Next, a point advanced from a certain candidate point by a length corresponding to the distance R traveled by the vehicle along the corresponding line segment is set as a new candidate point C (n) (step 426). Therefore, when the number of line segments in which a candidate point is located or connected to the line segment and the difference between the direction and the vehicle direction is equal to or less than a predetermined value is n, n new candidate points C (n) will be generated. When there is a candidate point in a free state, which will be described later, there is no line segment where the candidate point is located, so when calculating the next candidate point for this candidate point (steps 422 to 426), a predetermined virtual current position is used. Since all the line segments in the range D are extracted, the number of candidate points can be increased.
[0053]
Finally, the candidate point with the highest reliability is selected from these candidate points as the display candidate point, and this display data candidate point data is output (step 427). More specifically, the candidate point C having the highest reliability value is set as a display candidate point CD, that is, a candidate point to be displayed on the display 17, its position, accumulated error cost, reliability, which will be described later. A state flag indicating whether the state is a matching state or a free state is stored in a predetermined area of the RAM of the memory 25, and the positions of candidate points other than the display candidate points, the accumulated error cost, the reliability, The status flag and the like are also stored in a predetermined area of the RAM.
[0054]
Here, the action of map matching is considered by taking a specific road as an example. For example, as shown in FIG. 7, it is assumed that the current position A is represented at a position indicated by a point 63 with respect to a certain candidate point 62 existing on the line segment 61. In such a case, a line segment 64 connected from the current position A to the line segment 61 where the candidate point 62 is located, and the difference between the direction and the vehicle direction is equal to or less than a predetermined value, 65, the distances L (1) and L (2) from the current position A to the line segments 64 and 65 are calculated, and the calculated distances and the angles θ (1) and θ ( 2) Calculate the related error cost, accumulated error cost, and reliability based on the vehicle orientation θcar and the like. Further, the length corresponding to the travel distance R from a certain candidate point 62 along the line segments 61 and 64 or along the line segments 61 and 65 based on the travel distance R of the vehicle obtained in step 307 of FIG. A position advanced by only this point is calculated, and points corresponding to this position are set as candidate points 66 and 67, respectively.
[0055]
Further, as shown in FIG. 8, the new current position A is represented at the position indicated by the point 71 with respect to the candidate point 66 on the line segment 64, while the candidate point 67 on the line segment 65 is displayed. On the other hand, it is assumed that the new current position A ′ is represented at the position indicated by the point 72. In this case, from the current position A, line segments 73 and 74 that are connected to the line segment 64 and whose difference between the azimuth and the vehicle azimuth is equal to or less than a predetermined value are taken out and a new one is taken. From the current position A ′, a line segment 75 connected to the line segment 65 and having a difference between the direction and the vehicle direction equal to or less than a predetermined value is taken out. Next, distances L1 (1) and L1 (2) from the current position A to the line segments 73 and 74 are calculated, and a distance L2 (1) from the current position A ′ to the line segment 75 is calculated. . Further, based on the distance calculated in relation to the current position A, the angles θ1 (1) and θ1 (2) of the line segments 73 and 74, the vehicle orientation θcar, and the like, the associated error cost, accumulated error cost, and reliability And the related error cost, accumulated error cost, and reliability are calculated based on the distance calculated in relation to the current position A ′, the angle θ2 (1) of the line segment 75, the vehicle orientation θcar, and the like. .
[0056]
Further, from the candidate point 66, along the line segments 64 and 73, or along the line segments 64 and 74, or from the candidate point 67, based on the vehicle travel distance R obtained in step 307 of FIG. A position advanced by a length corresponding to the travel distance R of the vehicle along 65 and 75 is calculated, and points corresponding to this position are set as new candidate points. FIG. 9 shows the candidate points 81 to 83 newly obtained in this way.
[0057]
Here, the candidate point matching state and the free state will be described. From the current position A to a candidate point located on a certain line segment, the line segment where the candidate point is located or a line segment connected thereto, and the difference between the direction and the traveling direction of the vehicle is less than a predetermined value There may be a case where there is no line segment such as In this case, the current position A itself is handled as the next candidate point calculated from the candidate point. In the present embodiment, the candidate points obtained in this manner are referred to as free state candidate points. On the other hand, in other states, that is, from the current position A to a candidate point located on a certain line segment, the line segment in which the candidate point is located or a line segment connected thereto, and its orientation and A state in which there is a line segment whose difference from the traveling direction of the vehicle is equal to or less than a predetermined value, and as a result, the next candidate point may exist on a specific line segment is referred to as a matching state.
[0058]
Further, when there is no line segment where the candidate point is located or connected to the line segment and the difference between the direction and the traveling direction of the vehicle is equal to or less than a predetermined value, in step 425 The error cost ec (n) to be calculated is given a constant value larger than the error cost value obtained in the matching state.
[0059]
When obtaining a new candidate point based on this free state candidate point, the virtual current position itself with respect to the free state candidate point is set as a new free state candidate point, and a predetermined range from the virtual current position. In D, if there is a line segment whose difference between the heading and the traveling direction of the vehicle is less than or equal to a predetermined value, the intersection of the vertical line drawn from the virtual current position to the line segment and this line segment, Let it be a new candidate point.
[0060]
As can be easily predicted from the above description, the processing time for executing the map matching process depends on the density of the road corresponding to the road data, and in particular, the map corresponding to the read map data is When the road density is high, such as in an urban area, this processing time is very long. Therefore, in this embodiment, as described above with reference to FIG. 4, by deleting candidate points whose distance from the display candidate points is a predetermined amount or more, it is possible to reduce the processing load and prevent an increase in processing time. it can. Since it is unlikely that a candidate point extremely far from the display candidate point is the true current position, it is considered that this does not reduce the accuracy of map matching.
[0061]
The display candidate points obtained in step 427 in FIG. 5 are displayed on the screen of the display 17 by processing based on the flowchart shown in FIG.
[0062]
This process is a routine of the microprocessor 24 that is activated and executed every second.
[0063]
First, it is determined by checking the contents of the parallel I / O 21 whether the switch 14 is instructed to change the scale of the map by pressing (step 1301). If it is pressed (Yes in Step 1301), a predetermined scale flag is set correspondingly (Step 1302).
[0064]
Next, data indicating the position and orientation of the display candidate point is read from a predetermined area of the RAM of the memory 25 (step 1303), and a map of a scale corresponding to the contents of the scale flag switched in step 1302 is displayed on the display 17. For example, it is displayed in a state as shown in FIG. 2 (step 1304).
[0065]
Then, the position of the display candidate point and its direction are displayed using, for example, the arrow symbol “↑” as shown in FIG. Finally, a north mark indicating north and a distance mark corresponding to the scale are displayed as shown in FIG. 2 so as to be superimposed on these (step 1306).
[0066]
In the present embodiment, the vehicle position and direction are indicated by using the arrow symbols as described above. However, in the display form of the vehicle position and direction, the display state is clearly shown for the position and the traveling direction. If it exists, the form may be arbitrary. The same applies to the north mark and the like.
[0067]
According to the present embodiment, since the candidate point is deleted based on the distance of each candidate point with respect to the display candidate point,
While maintaining the reliability of the map matching process, it is possible to reduce the process that requires a large amount of processing time, and therefore it is possible to reduce the processing time required to calculate the current position.
[0068]
In this specification, the term “means” does not necessarily mean a physical means, but includes cases where the function of each means is realized by software. Further, the function of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means.
[0069]
【The invention's effect】
According to the present invention, it is possible to provide a current position calculation device that can reduce the processing load without impairing the accuracy of map matching.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a current position calculation apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a display example of a map and a current position according to the present embodiment.
FIG. 3 is a flowchart showing a process for calculating a traveling direction and a travel distance of a vehicle.
FIG. 4 is a flowchart illustrating a main process executed for each predetermined travel distance according to the present embodiment.
FIG. 5 is a flowchart showing a detailed process of one step (map matching process) shown in FIG. 4;
FIG. 6 is a diagram for explaining an example of road data according to the embodiment.
FIG. 7 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and candidate points;
FIG. 8 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and candidate points.
FIG. 9 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and candidate points;
FIG. 10 is a flowchart of the current position display process according to the embodiment.
[Explanation of symbols]
10 Current position calculation device
11 Angular velocity sensor
12 Geomagnetic sensor
13 Vehicle speed sensor
14 switch
15 CD-ROM
16 CD-ROM reader
17 Display
18 Controller

Claims (1)

  A current position calculation device that is mounted on a vehicle and calculates a current position of the vehicle,
  Direction detection means for detecting the traveling direction of the vehicle;
  A distance calculating means for calculating a travel distance of the vehicle;
  Road data storage means for storing road data;
  A virtual current position of the vehicle is estimated, the estimated virtual current position is compared with road data stored in the road data storage means, a candidate point of the current position on the road is calculated, and the calculated candidate point The reliability is calculated according to the distance from the road where the candidate point is located to the virtual current position, the azimuth of the road where the candidate point is located, and the azimuth difference between the traveling directions, and the candidate with the highest reliability Map matching means to recognize the point as the current position and
With
  The map matching means includes:
  If the estimated virtual current position is outside the road and no candidate point on the road for the virtual current position is found, the virtual current position is directly calculated as a free candidate point,
  Among candidate points calculated last time, for candidate points on the road existing within a first distance from the candidate point having the highest reliability, the relative value obtained from the candidate point and the traveling direction and the travel distance Calculate the current virtual current position of the vehicle based on the displacement, calculate the current candidate point for the calculated current virtual current position,
  Among the candidate points calculated last time, free candidate points that exist within a second distance shorter than the first distance from the candidate point with the highest reliability, from the free candidate point Calculate the current virtual current position corresponding to the candidate point, and calculate the current candidate point for the calculated current virtual current position
A current position calculation device characterized by the above.

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