JP3656661B2 - Current position calculation system and current position calculation method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a current position calculation system that is mounted on a moving body such as a vehicle, measures a traveling 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 system for calculating the current position of a vehicle traveling on a road, the current position of the vehicle is measured by a vehicle traveling direction 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]
Further, the travel distance of the vehicle is generally obtained by measuring the output shaft of the transmission or the rotation speed of the tire and multiplying the rotation speed by a 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 traveling distance of the vehicle as described above, as described in Japanese Patent Laid-Open No. 63-148115, the vehicle determined based on the traveling distance and the amount of change in direction Based on the estimated position and the error of the road map, an error amount is obtained, and the estimated position is registered as a self position corresponding to all roads within the range of the error amount centered on the estimated position. A technique is disclosed in which a correlation coefficient for each road at a registered estimated position is calculated, and an estimated position corresponding to the correlation coefficient indicating that the error with respect to the road is the smallest is the current position. As described in this publication, a so-called map matching technique for correcting the current position of the obtained vehicle so as to match the road is known, and this map matching technique allows the calculation of the current position. Accuracy can be increased.
[0005]
[Problems to be solved by the invention]
When map matching is executed using the technique described above, a plurality of estimated positions may be calculated when the vehicle passes through a branch point. That is, as the vehicle travels and repeatedly passes through the branch point, the number of estimated positions increases significantly. In general, a current position calculation system that calculates the current position of a vehicle by executing map matching can only store several estimated positions due to the limitation of the storage capacity of a memory provided therein. Furthermore, the current position calculation system may not be able to calculate all estimated positions due to the processing time limit for executing map matching.
[0006]
Therefore, any estimated position is selected from a plurality of estimated positions, and the current position of a new vehicle is calculated based on the selected estimated position. It is desirable to decide appropriately whether to keep it.
An object of the present invention is to provide a current position calculation system that calculates a current position of a vehicle more accurately by selecting an appropriate estimated position from a plurality of estimated positions of a plurality of vehicles.
[0007]
[Means for solving the problems]
An object of the present invention is a current position calculation system that is mounted on a vehicle and calculates the current position of the vehicle, the direction detection means for detecting the traveling direction of the vehicle, and the distance calculation means for calculating the travel distance of the vehicle, Based on the relative displacement obtained based on the traveling direction and the travel distance and a candidate point indicating a state where the vehicle is located on any road or a state where the vehicle is not located on the road. Virtual current position generating means for generating a virtual current position that is expected to be a position, and the virtual current position and road data included in the map data so that at least one candidate point is obtained based on each candidate point And a candidate point generating means for generating a new candidate point, and a predetermined one selected from the new candidate point is set as the calculated current position of the vehicle Position calculation It is achieved by the system.
[0008]
In a preferred embodiment of the present invention, the image processing apparatus further includes reliability calculation means for calculating reliability indicating the credibility that the vehicle exists at a position on the road corresponding to the candidate point, and the candidate point generation means includes the Based on the reliability, it has a determining means for determining the number of candidates indicating the number of new candidate points that each candidate point should obtain, and generates new candidate points based on each candidate point according to the determined number of candidates. It is configured as follows.
[0009]
In a further preferred aspect of the present invention, the candidate point generating means is configured to assign a predetermined number of candidates to each candidate point according to the total number of candidate points.
[0010]
In a further preferred aspect of the present invention, the number of candidates is stored in a table having the total number of candidate points as an address.
[0011]
In a further preferred embodiment of the present invention, a predetermined one of the new candidate points is selected as the calculated current position according to the reliability.
[0012]
In a further preferred embodiment of the present invention, the candidate point generating means is configured such that the azimuth difference between the azimuth of the line corresponding to certain data included in the road data and the vehicle azimuth is greater than a predetermined angle value. In the case of being small, it is configured to generate candidate points indicating that the vehicle exists on the road corresponding to the line segment.
[0013]
[Action]
According to the present invention, at least one candidate point is obtained based on each candidate point. That is, a virtual current position is obtained from a certain candidate point, and one or more candidate points are always generated based on the virtual current position. Therefore, even though a certain candidate point is the current position of the vehicle, a new storage point based on the candidate point is newly created based on the limitation of the storage capacity of the memory for storing the candidate point or the limitation of the processing time of the system. The possibility that the candidate point cannot be obtained can be reduced, and as a result, the current position of the vehicle can be calculated more accurately.
[0014]
According to the preferred embodiment of the present invention, since the number of candidates indicating the number of new candidate points that each candidate point should obtain is determined based on the reliability, the candidate point with higher reliability that is the current position of the road Based on the above, it becomes possible to generate more new candidate points.
[0015]
According to a further preferred embodiment of the present invention, each candidate point is configured to be assigned a predetermined number of candidates according to the total number of candidate points, so that when the total number of candidate points is large, or In any case where the number is small, an appropriate number of new candidate points can be generated.
[0016]
According to a further preferred embodiment of the present invention, since the number of candidates is stored in the table, an appropriate number of candidates based on the total number of candidate points can be obtained by simple processing.
[0017]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0018]
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 an azimuth 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.
[0019]
In addition, a display 17 for displaying a map around the current position, a mark indicating the current position, and the like, and a command for switching the scale of the map displayed on the display 17 are used. The( A switch 14 received from the driver), a CD-ROM 15 for storing digital map data, and a driver 16 for reading the 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.
[0020]
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 azimuth 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.
[0021]
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 direction 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.
[0022]
Hereinafter, the operation of the current position calculation device 10 configured as described above will be described.
[0023]
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.
[0024]
FIG. 3 illustrates a flow of processing for calculating the traveling direction and traveling distance of the vehicle.
[0025]
This process is a routine of the microprocessor 24 that is activated and executed at a constant cycle, for example, every 100 ms.
[0026]
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. For this reason, next, the output value of the azimuth sensor 12 composed of a geomagnetic sensor is read from the A / D converter 20 (step 302), and the absolute azimuth calculated from the output value of the azimuth sensor 12 and the output from the angular velocity sensor 11 are output. The estimated heading of the vehicle is determined using the heading change (angular velocity output) (step 303).
[0027]
For example, when the vehicle speed is low for a long time, the error of the angular velocity sensor is large. Therefore, when the vehicle speed is low for a certain time or more, the direction is determined by using only the direction of the direction sensor.
[0028]
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).
[0029]
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.
[0030]
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 travel direction and the travel distance R (20 m in this embodiment) at that time Are output (step 307). In step 307, the accumulated distance is further initialized, and the accumulated travel distance is newly started.
[0031]
Next, a process of calculating a virtual current position of the vehicle based on the calculated traveling direction and traveling distance and obtaining a candidate point of the vehicle based on the calculated virtual current position will be described.
[0032]
FIG. 4 shows the flow of this process.
[0033]
This process is a routine of the microprocessor 24 that is activated and executed in response to the output of the traveling direction and traveling distance from FIG. That is, in this embodiment, this process is started every time the vehicle travels 20 meters.
[0034]
Well, in this process, first, step 307 The travel direction and travel distance output in step 1 are read (step 401). Next, based on these values, 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 402).
[0035]
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.
[0036]
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 on the line segment corresponding to the road due to an error such as a direction sensor. As a result, for example, as shown in FIG. 5, when the road is branched, that is, when two line segments 64 and 65 appear from the node or end 68 of the line segment 61 corresponding to the road, In many cases, it cannot be clarified whether a vehicle exists on the road corresponding to the line segment.
[0037]
Therefore, in such a case, in this embodiment, a point existing on a line segment (two line segments in the example shown in FIG. 5) obtained by the processing described later is selected as a candidate point under a predetermined condition. The current position, error cost, accumulated error cost, which will be described later, and the like are each 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.
[0038]
Next, the first road search process for matching with the road is executed only for the candidate points in the matching state obtained by the process for obtaining the candidate points of the previous vehicle (step 403). In this embodiment, the matching state means that a distance from the virtual current position or an azimuth difference between the direction and the traveling direction of the vehicle is within a predetermined range in relation to a certain virtual current position. This means a state in which a candidate point is obtained at a predetermined position on the road based on the virtual current position. On the other hand, in relation to a certain virtual current position, there may be a case where there is no road where the above-described distance and direction difference are within a predetermined range. In this embodiment, in such a case, the point itself corresponding to the virtual current position A is a candidate point, and the candidate point obtained in this way is referred to as a free state candidate point.
[0039]
FIG. 6 is a flowchart illustrating the first road search process according to the present embodiment.
[0040]
As shown in FIG. 6, in this road search process, first, predetermined road data is read from the CD-ROM 15 via the driver 16 and the DMA controller 23 (step 601). In this embodiment, as road data, as shown in FIG. 7, a plurality of line segments 51 to 55 connecting two points are approximated, and those line segments are expressed by coordinates of the start point and the end point. Used. For example, the line segment 53 is represented by its start point (x3, y3) and end point (x4, y4). Therefore, in this step 601, the line segment where the candidate point of the matching state obtained by the previous process is located is selected, and data relating to this is read out.
[0041]
Next, based on the coordinates of the line segment selected in step 601, a line segment including a position advanced by a length corresponding to 20 m along the traveling direction of the vehicle from the position of the candidate point is searched. Coordinate data relating to the minute is temporarily stored as data indicating the primary candidate line segment (step 602). More specifically, the length of the line segment where the candidate point is located to the end in the traveling direction of the vehicle is a length corresponding to 20 m. If it is above The coordinate data and the like are stored with the line segment as the primary candidate line segment. Further, the length to the end of the vehicle in the traveling direction of the line segment where the candidate point is located is a length corresponding to 20 m. Less than If so, a line segment connected to the line segment is searched.
[0042]
Next, in step 602, it is determined whether or not at least one primary candidate line segment has been found (step 603). If it is determined no (No), the process proceeds to step 604.
[0043]
On the other hand, if it is determined as Yes in step 603, an angle comparison process for comparing the angle between the traveling direction of the vehicle and the direction of the primary candidate line segment is executed (step 605). ). FIG. 8 is a flowchart showing the angle comparison processing according to the present embodiment. As shown in FIG. 8, in this process, an azimuth difference θd between the traveling azimuth of the vehicle and the azimuth of the line segment is calculated (step 901), and the absolute value of this azimuth difference θd is determined from a predetermined threshold value θth. Is also larger (step 902). In this embodiment, the threshold value θth is set to 30 °. When it is determined NO in step 902, the process is terminated. On the other hand, when it is determined YES, it is determined that the road is not a primary candidate line segment. The temporarily stored data corresponding to the primary candidate line segment is deleted (step 903).
[0044]
When the angle comparison process shown in step 605 of FIG. 6 is completed, if a plurality of primary candidate line segments are stored in step 602, the angle comparison process is also executed for the other primary candidate line segments (steps 605 and 606). ) When the angle comparison process is executed for all the primary candidate line segments, the process proceeds to step 607. In this way, the azimuth difference between the azimuth and the vehicle azimuth among the line segment where the candidate point obtained in the previous process is located or connected to this is less than the threshold θth. Is stored as data indicating the primary candidate line segment.
[0045]
Step 607 determines whether there is at least one primary candidate line segment temporarily stored. If it is determined NO in step 607, the process proceeds to step 604. On the other hand, if it is determined as Yes in step 607, a perpendicular distance comparison process is executed (step 608). FIG. 9 is a flowchart showing the perpendicular distance comparison process according to the present embodiment. As shown in FIG. 9, in this process, a perpendicular line is drawn from the virtual current position toward the primary candidate line segment, and the length L of this perpendicular line is obtained (step 1001). Next, it is determined whether or not the length L of the perpendicular is equal to or less than a predetermined threshold value Lth (step 1002). That is, it is determined whether or not the primary candidate line segment exists within the range of the threshold value Lth from the virtual current position. If the determination in step 1002 is YES, various data relating to the primary candidate line segment are stored as data indicating the secondary candidate line segment, and from the candidate points obtained in the previous process. The coordinate data at positions separated by a distance R along a predetermined line segment is stored as position data corresponding to the secondary candidate line segment. (Step 1003) .
[0046]
On the other hand, if it is determined NO in step 1002, the data related to the primary candidate line segment is deleted, and as a result, no secondary candidate line segment is generated (step 1004).
[0047]
Thus, when the perpendicular distance comparison process 608 is completed, it is determined whether or not the process has been completed for all primary candidate line segments (step 609).
[0048]
By repeating step 608 and step 609, a predetermined distance R from the line segment where the candidate point obtained by the previous process is located along the line segment or a line segment connected thereto in the traveling direction of the vehicle. There is a point that is separated by a distance, the azimuth difference between the azimuth and the traveling azimuth of the vehicle is less than or equal to a predetermined threshold value θth, and the distance from the virtual current position is a predetermined threshold value A secondary candidate line segment that is Lth or less can be obtained. Furthermore, as position data corresponding to the obtained secondary line segment, coordinate data of a position separated by a distance R along a predetermined line segment can be obtained from the candidate point obtained in the previous process. This coordinate data corresponds to data indicating candidate points to be described later.
[0049]
When the processing of steps 608 and 609 is completed for the primary candidate line segment, it is determined whether or not a secondary candidate line segment has been obtained as a result of these steps (step 610). If it is determined NO in step 610, the process proceeds to step 604. On the other hand, if YES is determined, the process is terminated.
[0050]
For example, in FIG. 5, it is assumed that the virtual 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, first, the line segment 61 where the candidate point 62 is located is selected (step 601), and the distance from the candidate point 62 on this line segment to the end 68 in the traveling direction of the vehicle is determined. In the case of the example of FIG. 5, since there is a road connected to this line segment, data related to the line segments 64 and 65 are temporarily stored as data indicating primary candidate line segments, respectively. In relation to, angle comparison processing (step 605) is executed. Here, in the example of FIG. 5, assuming that | θ (1) −θcar | <θth and | θ (2) −θcar | <θth, the processing loop consisting of steps 605 and 606 is repeated twice. Then, the perpendicular distance comparison process (step 608) is executed in relation to each of the line segments 64 and 65.
[0051]
Furthermore, in the example of FIG. 5, if L (1) <Lth and L (2) <Lth, the data related to the line segments 64 and 65 are stored as secondary candidate line segments, and further candidates Points that are advanced from the point 62 by a length corresponding to the travel distance R (20 m in this embodiment) along the line segments 61 and 64 or along the line segments 61 and 65 are set as candidate points 66 and 67. The coordinate data of this point, the data corresponding to the distances L (1) and L (2) from the virtual current position to the line segment, and the data corresponding to the angles θ (1) and θ (2) of the line segment Remembered.
[0052]
Returning to the description of the first road search process in FIG. 6 again. Here, when it is determined as No (No) at Step 603, when all the primary candidate line segments are deleted in the angle comparison process at Step 605 (No (No) at Step 607), or If the secondary candidate line segment is not obtained in the perpendicular distance comparison process (No in step 610), the coordinate data indicating the virtual current position becomes data indicating the candidate point.
[0053]
When the first road search process in step 403 is completed in this way, the second road search for matching with the road only with respect to the candidate points in the free state obtained by the process for obtaining the candidate points of the previous vehicle. Processing is performed (step 404). By executing the first road search process (step 403) and the second road search process (step 404), it becomes possible to obtain new candidate points for all candidate points obtained by the previous process. . Figure 10 These are the flowcharts which show the 2nd road search process concerning a present Example.
[0054]
As shown in FIG. 10, this process (steps 1301 to 1304) is similar to the first road search process (step 403 in FIG. 4) for the candidate points in the matching state shown in FIG. The difference between these two processes is as follows. That is, in the first road search process, the line segment where the candidate point obtained by the process for obtaining the candidate point of the previous vehicle is located or the line segment connected thereto is temporarily used as the primary candidate line segment. From these primary candidate line segments, further, the direction difference between the direction and the vehicle direction is equal to or smaller than a predetermined threshold value θth, and the length corresponding to the distance from the virtual current position is a predetermined threshold. A line segment within the value Lth is selected as a secondary candidate line segment.
[0055]
On the other hand, in the second road search process, all the line segments within the preset distance D centered on the virtual current position (A) are extracted (step 1301), and the direction is determined from these line segments. A line segment whose azimuth difference between the vehicle direction and the vehicle direction is equal to or smaller than a predetermined threshold value θth is selected (step 1302). A line segment whose length is within a predetermined threshold Lth is selected as a secondary candidate line segment (step 1303). In other words, in step 602 of the first road selection process, the line segment where the candidate point is located, or some line segments extending from the branch point of the line segment are selected. In 1302, a line segment to be extracted is determined based on the road data included in the read map data. Therefore, the processing time for executing steps 1301 to 1303 depends on the density of the road corresponding to the road data, and particularly when the map corresponding to the read map data is an urban area. When the density is high, this processing time is longer than the time required to execute the corresponding processing in the first road search processing.
[0056]
In this second road search process, when step 1303 ends, the line segment extracted in steps 1302 and 1303, that is, the azimuth difference between the azimuth and the vehicle azimuth is equal to or less than the threshold θth. A line segment whose length corresponding to the distance from the virtual current position is equal to or smaller than the threshold value Lth is selected as a secondary candidate line segment, and various data related to the line segment are selected as secondary candidate line segments. Is stored as data indicating. Also, the point where the current position is present and the leg of the perpendicular line drawn from the virtual current position to the line segment, that is, the intersection of the perpendicular line and the line segment are determined as candidate points, and the coordinate data of these candidate points Is stored (step 1304). In the second road search process, the virtual current position Rao The intersection point between the drawn perpendicular line and the line segment is a candidate point because the candidate point obtained by the previous processing is in a free state and therefore there is no line segment to be traced.
[0057]
In the second road search process, when there is no line segment within the predetermined range D from the virtual current position, there is a line segment whose azimuth difference between the direction and the traveling direction of the vehicle is equal to or smaller than the threshold value θth. Otherwise, or when there is no line segment whose length corresponding to the distance from the virtual current position is equal to or less than the threshold value Lth, the point corresponding to the virtual current position is the only candidate point.
[0058]
As described above, when the second road search process in step 404 ends, candidate point selection for selecting a predetermined one from a plurality of candidate points obtained by the first road search process and the second road search process Processing is executed (step 405).
[0059]
In the present embodiment, only seven candidate points are finally stored in the RAM in the memory 25. Therefore, the candidate point that should be the basis for calculating the virtual current position in the next process is selected in this step 405. FIG. 11 is a flowchart illustrating candidate point selection processing according to the present embodiment. As described above, in this process, seven candidate points are finally selected (steps in FIG. 11). 1114 However, in the middle steps up to this step, a maximum of 14 candidate points are temporarily selected.
[0060]
In this process, first, the number of candidate points Ai obtained by the previous process is checked (step 1101), and the reliability value indicating the reliability of the current position of the vehicle, which will be described later, is determined for these candidate points. Sort in descending order (step 1102). Next, it is determined how many candidate points can be newly generated for each candidate point obtained in the previous process (step 1103). More specifically, with reference to the generatable candidate number table shown in FIG. 12, for each number cnt of candidate points A obtained by the previous processing, the candidate point A0 having the largest reliability value or the smallest value is obtained. The number of candidate points that the candidate point A6 can generate is determined.
[0061]
For example, if the number cnt of the number of candidates Ai is 3, it is possible to generate seven candidate points based on A0, four candidate points based on A1, and three candidate points based on A2. It should be noted that as the reliability value of the candidate point A increases, the number of candidate points that can be generated based on the candidate point increases.
[0062]
The reason why the number of candidate points that can be generated based on each candidate point is determined according to the number of candidate points generated in the previous process and the reliability values of these candidate points will be described.
[0063]
As described with reference to FIG. 5, when candidate points in the matching state pass through a branch point, new candidate points may be generated as many as the number of line segments connected to the branch point. In addition, when a line segment exists within a predetermined range of the virtual current position obtained based on the candidate points in the free state, the point corresponding to the virtual current position and the line segment from the virtual current position are reduced. There are cases where both the intersection of the perpendicular line and the line segment become new candidate points. Thus, the number of candidate points increases cumulatively as the vehicle travels. On the other hand, the number of candidate points that can be stored is limited by the storage capacity of the memory, the processing time for calculating candidate points, and the like.
[0064]
Therefore, in this embodiment, according to the generatable candidate point table, each of up to seven candidate points obtained by the previous processing can generate and generate at least one new candidate point. The number of new candidate points is increased in accordance with the reliability value of the candidate points.
[0065]
As described above, when the number of candidate points that can be newly generated is determined based on the candidate points obtained by the previous process in step 1103, the number of candidate points A0 to A7 obtained by the previous process is obtained. The error cost, reliability, etc. of the new candidate point Bij thus obtained are calculated (steps 1105 to 1111).
[0066]
Further, in this embodiment, if the number of candidate points obtained in step 403 or 404 is less than the number of candidate points that can be generated based on the candidate points obtained in the previous process, The number of candidate points that can be generated, that is, (the number m of candidate points that can be generated based on the candidate point) − (the number of candidate points Bij actually obtained in step 403 or step 404) is the reliability. Is assigned to the number of candidate points that can be generated on the basis of another candidate point next to the candidate point.
[0067]
More specifically, first, in step 1104, the residual number x = 0 is initialized, and then y = the number m of candidate points that can be generated + the residual number x− (the number of actually obtained candidate points Bij). (Step 1105). If y is 0 (zero) or more, that is, if m + x is greater than or equal to the number of candidate points Bij actually obtained (in step 1106). No ( No )), The obtained y becomes a new residual number x to be used in the next step 1105 (step 1107), and the error cost, accumulated error cost, and reliability of each obtained candidate point Bij are calculated. (Step 1108).
[0068]
More specifically, the distance L (ij) between the virtual current position based on the candidate point Ai obtained in the previous process and the secondary candidate line segment where the obtained candidate point Bij is located, and the candidate point is Based on the azimuth difference θd (ij) between the azimuth of the secondary candidate line and the azimuth of the vehicle, an error cost ec (ij) defined by the following equation is calculated.
[0069]
ec (ij) = α × | θd (ij) | + β × L (ij)
Here, α and β are weighting factors. The values of these weighting factors should be used to select a road between a deviation between the traveling direction of the vehicle and the direction of the line segment, or a deviation between the virtual current position and the line segment. Therefore, it is determined. For example, when it is important to select a traveling direction and a road having a similar direction and direction, α is increased.
[0070]
Next, according to the calculated error cost ec (ij) and the accumulated error cost es related to the candidate point Ai obtained in the previous process, the accumulated error in the current process defined by the following equation Cost es (ij) is calculated.
[0071]
es (ij) = (1-k) * es + k * ec (ij)
Here, k is a weight coefficient larger than 0 and smaller than 1. This accumulated error cost es (ij) represents how much the error cost calculated in the previous process is reflected in the error cost calculated in the current process.
[0072]
Further, based on the calculated accumulated error cost es (ij), a reliability trst (ij) defined by the following equation is calculated.
[0073]
trst (ij) = 100 / (1 + es (ij))
As is clear from the above equation, the accumulated error cost e s As (ij) increases, the reliability trst (ij) decreases and approaches 0 (zero). On the other hand, as this becomes smaller, the reliability trst (ij) increases and its value approaches 100.
[0074]
By performing such processing, the reliability trst (ij) related to the candidate point obtained corresponding to the candidate point Ai is obtained.
[0075]
In relation to the candidate point in the free state, the error cost ec (ij) to be calculated in step 405 is given a constant value larger than the error cost value obtained in the matching state.
[0076]
On the other hand, if y is negative, that is, if m + x is smaller than the actually obtained candidate point Bij (in step 1106) Jesus ( Yes )), The error cost ec (ij), the accumulated error cost es (ij), and the reliability trst (ij) are calculated for each Bij as in step 1108, and the reliability trst corresponding to each of the candidate points Bij. These new candidate points Bij are sorted according to the value of (ij) (step 1109).
[0077]
Further, | y | candidate points are deleted from the one with the smaller reliability value. That is, data related to these candidate points stored in the RAM of the memory 25 is deleted (step 1110). In this case, when y is negative, the remaining number x is 0 (zero), and therefore x = 0 in step 1111.
[0078]
By repeating such processing, a maximum of 14 candidate points Bij can be obtained.
[0079]
For example, as shown in FIG. 13, seven candidate points A0 to A6 are selected by the previous process. If Consider the case where Ki candidate points Bij are obtained based on these candidate points in step 403 or step 404, respectively. In this case, in step 1105 related to each Ai, y as shown in FIG. 13 is generated, and step 1107 and step 1108 or steps 1109 to 1111 are executed according to the value of y. Here, in relation to A5, y = 2 + 0 (this is the remaining number obtained by the processing related to A4) −3 = −1, and therefore, among the three Bijs, the reliability value of 2 is large. Only Bij will be left.
[0080]
When the processing from step 1105 to step 1111 is executed in relation to all of the candidate points Ai obtained by the previous processing (Yes in step 1112), the obtained candidate points Bij are represented by their reliability values. (Step 1113) , Only a predetermined number (seven in this embodiment) of candidate points are selected in descending order of reliability, and data related to these candidate points is stored in a predetermined area of the RAM of the memory 25 (step 1114). ).
[0081]
As described above in detail, when the candidate point selection process (step 405 in FIG. 4) is completed, the reliability value of the predetermined number of candidate points (seven in this embodiment) is selected. The largest candidate point is set as a display candidate point, that is, a candidate point for displaying on the display 17, its position, accumulated error cost, reliability, state flag indicating whether it is a matching state or a free state, etc. Is stored in a predetermined area of the RAM of the memory 25. Further, 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 (step 406).
[0082]
Finally, data related to the display candidate point is output (step 407), and the process ends.
[0083]
Display candidate points obtained by executing steps 401 to 406 in FIG. 4 are displayed on the screen of the display 17 by processing based on the flowchart shown in FIG.
[0084]
This process is a routine of the microprocessor 24 that is activated and executed every second.
[0085]
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 1401). If it is pressed (Yes in Step 1401), a predetermined scale flag is set correspondingly (Step 1402).
[0086]
Next, data indicating the position and orientation of the display candidate point obtained by executing the processing of FIG. 4 is read from a predetermined area of the RAM of the memory 25 (step 1403), and the scale flag switched in step 1402 A map of a scale corresponding to the contents of is displayed on the display 17 in a state as shown in FIG. 2, for example (step 1404).
[0087]
Then, the position of the display candidate point and its orientation are displayed using the arrow symbol “↑” as shown in FIG. 2, for example, as shown in FIG. 2 (step 1405). 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 1406).
[0088]
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.
[0089]
According to the present embodiment, in the candidate point selection process, the confidence that at least one candidate point can be generated from the candidate points obtained by the previous process and each candidate point is the current position of the road. The number of new candidate points that can be generated from each candidate point is determined according to the reliability indicating the reliability, so even if a large number of candidate points can be generated due to road branching, etc. Based on such candidate points, the current position of the vehicle can be calculated more accurately.
[0090]
Further, according to the present embodiment, in order to search for the line segment where the candidate point is located or connected to the virtual current position obtained from the candidate point in the matching state, Compared with the case where all roads existing around the current position are searched, a desired line segment can be searched in a shorter time.
[0091]
Furthermore, according to the present embodiment, only the length corresponding to the travel distance of the vehicle along the line segment where the candidate point in the matching state is located and / or the line segment connected to the line segment where the candidate point is located. Since the position advanced from the candidate point is set as the candidate point, the error between the calculated current position of the vehicle and the actual current position of the vehicle can be further reduced.
[0092]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.
[0093]
For example, in the embodiment, the candidate point selection process is configured to temporarily hold a maximum of 14 candidate points and finally select 7 candidate points from these candidate points. The number of candidate points that are temporarily held or finally selected is not limited to this.
[0094]
In the candidate point selection process of the embodiment, candidate points to be deleted are determined based on the reliability of the candidate points Bij (steps 1109 and 1110 in FIG. 11), but the present invention is not limited to this. Absent. For example, in order to reduce the processing time for candidate point selection processing, the candidate point to be deleted is determined based on the error cost of Bij, and only the reliability of the remaining candidate points is calculated. Also good.
[0095]
In addition, the parameters used in this embodiment are merely given for illustration, and therefore these parameters are the processing speed of the device, the type of road on which the vehicle is traveling (for example, general road, highway) It should be understood that the change can be made according to the above.
[0096]
Furthermore, in this specification, the means does not necessarily mean a physical means, but includes cases where the functions of the means are 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.
[0097]
【The invention's effect】
According to the present invention, when there are estimated positions of a plurality of vehicles, it is possible to provide a current position calculation system that calculates the current position of the vehicle more accurately by selecting an appropriate estimated position from these. Become.
[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 illustrating a process of calculating a traveling direction and a traveling distance of the vehicle according to the present embodiment.
FIG. 4 is a flowchart illustrating a process for calculating candidate points for a vehicle according to the embodiment.
FIG. 5 is a diagram for explaining a line segment corresponding to a road, a virtual current position, and candidate points;
FIG. 6 is a flowchart illustrating a first road search process according to the embodiment.
FIG. 7 is a diagram for explaining an example of road data according to the embodiment.
FIG. 8 is a flowchart illustrating angle comparison processing according to the present embodiment.
FIG. 9 is a flowchart illustrating normal distance comparison processing according to the embodiment.
FIG. 10 is a flowchart of a second road search process according to the embodiment.
FIG. 11 is a flowchart of candidate point selection processing according to the embodiment.
FIG. 12 is a diagram illustrating a number of generatable candidates table according to the embodiment.
FIG. 13 is a diagram for explaining selection of candidate points according to the embodiment.
FIG. 14 is a flowchart illustrating a current position display process according to the embodiment.
[Explanation of symbols]
10 Current position calculation device
11 Angular velocity sensor
12 Direction sensor
13 Vehicle speed sensor
14 switch
15 CD-ROM
16 CD-ROM reader
17 Display
18 Controller

Claims (7)

A current position calculation system for calculating a current position of a vehicle,
Direction detection means for detecting the traveling direction of the vehicle;
A distance calculating means for calculating a travel distance of the vehicle;
The current position of the vehicle based on the relative displacement obtained based on the traveling direction and the travel distance and a candidate point indicating a state where the vehicle is located on any road or a state where the vehicle is not located on the road Virtual current position generating means for generating a virtual current position expected to be,
Based on each candidate point, the virtual current position and the detected traveling direction of the vehicle are compared with road data included in the map data so that a new candidate point is obtained so that at least one candidate point is obtained. Candidate point generating means for generating;
Means for estimating a predetermined one selected from the new candidate points to the calculated current position of the vehicle ;
A reliability calculation means for calculating a reliability indicating the credibility that the vehicle exists at a position on the road corresponding to the candidate point;
The candidate point generation means determines the number of candidates indicating the number of new candidate points that each candidate point should obtain based on the reliability, and according to the determined number of candidates, a new candidate based on each candidate point A current position calculation system characterized by generating points . The current position calculation system according to claim 1 , wherein the candidate point generation unit is configured to assign a predetermined number of candidates to each candidate point according to the total number of candidate points. The candidate point generation unit has a table storing the number of candidates that can be generated from each candidate point for each total number of candidate points, and the number of candidates is determined based on data obtained from the table. The current position calculation system according to claim 2 . The estimating means includes
The current position calculation system according to claim 1 , wherein a predetermined one of the new candidate points is selected as the calculated current position according to the reliability. When the candidate point generation means determines that the azimuth difference between the azimuth of a line segment corresponding to certain data included in the road data and the vehicle azimuth is smaller than a predetermined angle value, the vehicle becomes the line segment. current position calculating system as claimed in any one of claims 1 to 4, characterized in that it is configured to generate the candidate points shown that present on the corresponding road. A current position calculation method performed by a current position calculation system for calculating a current position of a vehicle,
The current position calculation system includes:
Detecting the traveling direction of the vehicle;
Calculating the mileage of the vehicle;
The current position of the vehicle based on the relative displacement obtained based on the traveling direction and the travel distance and a candidate point indicating a state where the vehicle is located on any road or a state where the vehicle is not located on the road Generating a virtual current position expected to be;
Based on each candidate point, the virtual current position and the detected traveling direction of the vehicle are compared with road data included in the map data so that a new candidate point is obtained so that at least one candidate point is obtained. A candidate point generation step to generate;
Estimating a predetermined one selected from the new candidate points to the calculated current position of the vehicle ;
Performing a step of calculating the reliability indicating the credibility that the vehicle exists at a position on the road corresponding to the candidate point;
The candidate point generation step includes:
Based on the reliability, determining the number of candidates indicating the number of new candidate points that each candidate point should obtain, and generating new candidate points based on each candidate point according to the determined number of candidates <br> A current position calculation method characterized by the following: When the number of candidates related to a predetermined candidate point is smaller than the predetermined number of candidates, the number corresponding to these differences is set as another candidate having a reliability smaller than the reliability of the predetermined candidate point. current position calculating system as defined in claim 2 or 3, characterized in that it is configured to add the number of candidates to be associated with the point.

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