JPS6312097A - Updating of sensor correction coefficient - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of updating a sensor correction coefficient, and particularly to a method of updating a correction coefficient that corrects output data of a sensor that detects the traveling distance and direction of a vehicle in an in-vehicle navigation system. It is related to.

1. In recent years, in-vehicle navigation devices have been developed that guide the vehicle to a predetermined destination by storing map information in a memory, reading the map information from the memory, and displaying the map information along with the vehicle's current location. being researched and developed.

Such navigation devices detect the vehicle's travel distance and direction based on output data from a travel distance sensor, a direction sensor, etc. mounted on the vehicle, and estimate the vehicle's current location, which changes from moment to moment, based on this. , the current location is displayed on the map displayed on the display.

In this case, it is preferable that the current location is always displayed on the road on the map, but depending on the accuracy of the sensor, the current location may deviate from the road on the display, especially as the distance traveled becomes longer.

Since the mileage sensor and the direction sensor inevitably produce errors in the output data obtained due to their accuracy, it is necessary to correct the output data using a correction coefficient. However, the error in the mileage obtained by the mileage sensor is not only due to sensor accuracy, but also due to map accuracy, changes in tire pressure, slippage, etc. Therefore, the distance correction coefficient once set If you use it all the time, you won't be able to accurately determine the distance traveled.

In addition, even when using a geomagnetic sensor that detects the vehicle's direction based on geomagnetism (earth's magnetic field), the north indicated by this geomagnetic sensor is not relative to the map, so the direction correction coefficient is used to correct the sensor's output. Data correction is performed. However, since this correction coefficient varies depending on the region, if the azimuth correction coefficient is always constant, the azimuth of the vehicle cannot be detected accurately.

1. The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for updating a sensor correction coefficient that allows accurate detection of the traveling distance and the direction of the vehicle at all times.

The sensor correction coefficient updating method according to the present invention updates the correction coefficients that correct the output data of the sensor that detects the travel distance and direction of the vehicle with the travel data from the previous detected intersection every time an intersection is detected or every time a predetermined distance is traveled. It is characterized by updating based on distance and angle information obtained from map data.

Execution - one example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an in-vehicle navigation device according to the present invention. In the figure, 1 is a geomagnetic sensor for outputting vehicle orientation data based on geomagnetism, 2 is an angular velocity sensor for detecting the angular velocity of the vehicle, and 3 is a mileage sensor for detecting the distance traveled by the vehicle. , 4 is a GPS (Global Positioning System) for detecting the current location of the vehicle from latitude and longitude information, etc.
The output of each of these sensors (devices) is supplied to the system controller 5.

The system controller 5 has an interface 6 which inputs the outputs of the sensors (devices) 1 to 4 and performs A/D (analog/digital) conversion, etc., and processes various image data which are sequentially sent from the interface 6. CPU <central processing circuit) 7 that calculates vehicle movement m etc. based on output data of each sensor (device) 1 to 4
, a ROM (read only memory) 8 in which various processing programs for the CPU 7 and other necessary information are written in advance, and a RAM (random memory) in which information necessary for executing programs is written and read. access memory) 9', a recording medium 10 consisting of a so-called CD-ROM, an IC card, etc., on which digitized (numerical) map information is recorded, and a V-RAM (V-RAM).
Graphic memory 11 consisting of ideo RAM), etc.
and a graphic controller 13 that controls graphic data such as a map sent from the CPU 7 to be drawn in a graphic memory 11 and displayed as an image on a display 12 such as a CRT. The input bag M14 consists of a keyboard or the like, and issues various commands to the system controller 5 by the user's keystrokes.

Map information is recorded on the recording medium 10,
The data structure will be explained below.

First, as shown in Figure 2 (A>
6384 (=2”) [m] Divide into square meshes, and one mesh at this time is called a territory.The territory is Territory No. (Tx.

Ty), and each territory is assigned a territory number based on, for example, the lower left territory in the figure. Territory No. is the current location (Crntx.

CrntV). Territory is the largest management unit in this data structure. The entire structure of the map data file is shown in Figure 2 (B).
As shown in Figure 2 (C), the D file contains the territory number, the start address in the file of (Tx, Ty), the latitude of the lower left of the territory (real number), and the longitude of the lower left of the territory (real number). ), geomagnetic declination (real number), and other data are written for each territory.

The territory file is the most important file in this data structure, and various map data and data necessary for map drawing are written therein. In FIG. 3A, the navigation ID and section table are files for searching roads and intersections in navigation, the picture IO is a file for display management, and the data from road section data to intersection data is actual map data. As shown in Figure 3 (B), the map data has a hierarchical structure, with the bottom layer being polygon data for rivers, oceans, lakes, etc., the top layer being line data for roads, railways, etc., and the top layer being the various types of data. Character data such as marks, etc., above that is character data such as place names, and the top layer is intersection data. The intersection data on the top layer is data used for intersection drawing, which will be described later, and is not displayed on the display.

Next, as shown in FIG. 4(A), one territory is divided into, for example, 256 parts, resulting in 102
4 (2” > [m] square mesh is called a unit. This unit is also unit number, (Nx, Ny)
Managed by, its no.

(Nx, Ny) is the current location (Crntx, crnty
). A unit is an intermediate management unit, and map information is recorded in this unit, and a collection of 256 units constitutes a territory file. Maps are drawn based on this unit, so it can be called the basic unit of drawing. The Navi ID file contains the unit number as shown in Figure 4 (B).

<Nx, Ny) file, line start address, intersection start address, road section start address,
Data such as the intersection start address is written for each unit.

Furthermore, as shown in FIG. 5(A), one unit is divided into, for example, 16 parts, resulting in 256
) [m] square mesh is called a section. This section is similarly managed by section No. (Sx, Sy), and its No. <Sx, Sy) is the current location (CrntX
, CrntV). A section is the smallest management unit, and information on line segments (roads, etc. are expressed by connecting line segments) and intersections within this area is shown in Figure 5 (B).
As shown in (C), a sixth section table is added as a section table.
As shown in Figures (A) and (B) and Figures 7 (A) and 7' (B), it is registered in the territory file as section data.

In addition, as shown in FIG. 3 (A>), the territory file includes a file called picture ID for display management. The actual map data is set to 1/25,000, which is the largest scale. Maps at each scale are shown in Figure 8. ~ As shown in each figure (A) of Fig. 10, it is divided into areas, and this area is area No, (A
nx.

Any). Area NO, (A, nx, A
ny) is determined from the current location (CrntX, crnty). If the scale is 1/25,000, the area number and unit number 6 are the same, if the scale is 1/50,000, one area is equivalent to four unit files, and if the scale is 1/100,000, one area is the same. is equivalent to 16 units. In addition, the picture IO of each scale includes the beginning of polygons, lines, characters, and character data necessary to display the map of that scale, as shown in each figure (B) of Figures 8 to 10. Address and data size are recorded.

Next, polygon data and line data will be explained. Polygon data and line data are represented by connected vectors (line segments) represented by starting points and ending points, as shown in FIGS. 11(A) and 12(A). here,
If you represent a map at 1/50,000 or 1/100,000 using map data at the largest scale of 2°/50,000, the distance between the start and end points will shrink, so as far as you can see on the display, all points will not be displayed. There are some things you can do without. Taking this into consideration, information that can be omitted visually when displayed on a display is shown in Figure 11 <8.
) and as shown in FIG. 12(B), each thinning bit of polygon and line data is entered in advance. and,
The number of line segments (vectors) to be displayed can be reduced by checking the thinning bits when displaying each scale and removing points containing information in the thinning bits as necessary.

Furthermore, as shown in FIG. 13(A), serial numbers (x n, yn) are assigned to all intersections within one unit. By the way, the intersections are orthogonal, 7-junction,
There are various types of intersections, such as five-way intersections, but especially at intersections where there are multiple roads with similar directions, when passing through this intersection, the sensor accuracy, calculation error, map accuracy, etc. may cause you to select the wrong road, and the display may not show up. There is a possibility that the road on which the current location is displayed does not match the road on which the vehicle is actually traveling. Therefore, for such intersections, the 13th
As shown in Figure (B), difficulty level data indicating the difficulty level of the intersection is stored in the difficulty level bit in the intersection data. When passing through an intersection, by performing processing based on this difficulty level data, it is possible to prevent the wrong road from being selected. The processing will be explained later.

Next, regarding the display of map data, a case will be described in which, for example, a V-RAM is used as the graphic memory 11. As shown in FIG. 14(A), the display configuration is a 512 (dot) x 512 (dot) V-RAM.
The screen above is divided into 16 areas, and each area has an independent 1
Display multiple maps. One area is one unit of 128 (dots) x 128 (dots), and one
By dividing into 6 areas, 1 area is 32 (dots) x 32
(dot) (Figure 14 (B), (
(See C). The actual in-vehicle display has 256 (dots)
A 56 (dot) area (encircled by a thick line) is displayed, and this area moves on the V-RAM to express the movement of the vehicle's current location.

Next, the basic procedure executed by CPLJ7 will be explained according to the flowchart of FIG. 15.

The CPLJ 7 first performs initialization to execute a program (step 81), and then determines whether the current location of the vehicle has been set (step 82). If the current location has not been set, a current location setting routine is executed (step S3), for example, the current location is manually set using the keys on the input device 14. Next, the mileage is set to zero (step S4), and it is then determined whether there is any key input from the input device 14 (step 85).

If there is no key personnel available, a map of the area around the current location is displayed on the display 12, and the current location of the vehicle and its direction are displayed on this map using, for example, a vehicle mark, and when the vehicle moves, the map scrolls as the vehicle moves. Furthermore, when the vehicle position is about to exceed the range of district data currently on the graphic memory 11, the necessary map data is read out from the recording medium 10 and displayed on the display 12 (step 86).

If there is key human power, the current location is reset (step S7) and sensor correction (step S8) according to the input data.
, destination setting (step 89), and map enlargement/reduction (step 510) routines are executed.

Also, the CPLI7 is activated by the timer interrupt.
As shown in FIG. 6, a process is performed to constantly calculate the vehicle's direction based on the output data of the geomagnetic sensor 1 and the angular velocity sensor 2 at fixed time intervals (steps 811 and 812).
.

Furthermore, when data is input from the mileage sensor 3, the CPU 7 performs interrupt processing by the mileage sensor. In this interrupt process, as shown in FIG. 17, the current location is calculated from the travel distance and direction (step 513), right turn or left turn is determined (step 514), and turning into the road (step 514) is performed.
step 515), intersection pull-in (step 816),
Retraction based on mileage (step 517) is performed. Note that each process in steps 813 to 817 will be explained in detail later.

In addition, the latitude and longitude data obtained from the GPS device 4 are
As shown in FIG. 18, the data is processed by a GPS data reception interrupt, and the coordinates are converted as current location data (step 518).

The travel distance of the vehicle is determined from the output of the travel distance sensor 3. As this mileage sensor 3, for example, a sensor configured to calculate the mileage by integrating the distance of one rotation from the rotation speed of the car's so-called speedometer cable (JIS standard size is 637 rotations/km) is used. However, it is inevitable that errors will occur in the travel distance obtained due to the accuracy of the sensor 3. Furthermore, not only the accuracy of the sensor 3 but also the accuracy of the map, changes in tire air pressure, slips, etc. are factors that cause errors in travel distance. Therefore, unless the mileage is corrected frequently, it will not be possible to accurately calculate the distance.

Therefore, by calculating the distance correction coefficient rs from the actual measured distance obtained from the output of the mileage sensor + 3 and the distance obtained from the map data, and performing the distance correction using this correction coefficient rs, the mileage can always be maintained. It can be detected accurately.

Further, the direction of the vehicle is determined from the output of the geomagnetic sensor 1. This azimuth detection method is described in Japanese Patent Application No. 60-282341 filed by the present applicant and others.

The north indicated by this geomagnetic sensor 1 is magnetic north, not map north. Therefore, if the magnetic north is deviated from the map north, the estimated current location P1 obtained from the output of the geomagnetic sensor 1 when traveling a certain distance from the reference position will be different from the actual current location P2, as shown in FIG. This will result in a deviation. Therefore, it is necessary to convert the orientation determined by the geomagnetic sensor 1 into a map orientation.

As shown in FIG. 20, this conversion work is performed using a rotation angle determined by two-dimensional geometric coordinate conversion, that is, an orientation correction coefficient θS. This azimuth correction coefficient θS varies depending on the region, and the mounting error that occurs when the geomagnetic sensor 1 is attached to the vehicle body also varies depending on the error. This direction correction coefficient θS
As shown in FIG. 21, the coefficient can be set to zero and the vehicle travels between two points whose positions are known, and can be determined from the error between the current location and the arrival point determined by inertial navigation.

By correcting the direction using this direction correction coefficient θS, the direction of the vehicle can always be accurately detected.

Note that the method for calculating the distance correction coefficient rs and the direction correction coefficient θS is described in the specification of Japanese Patent Application No. 1982-282344 by the present applicant and others.

Next, the mileage sensor 3 executed by the CPLI 7
The interrupt processing procedure will be explained according to the flowchart of FIG. 22. The estimated current location is calculated at any time based on the output data of the mileage sensor 3, and this routine is called at a predetermined timing as the current location display routine.

First, the CPU 7 determines whether the unit distance Jio has been traveled (step 820>. Here, the unit distance refers to a certain distance actually traveled by the vehicle, for example, 20 [m
] is set. Then, this routine is executed every fixed mileage, and first the relationship with the map data, that is, the 23rd
As shown in the figure, find the distance Eta to the nearest line point, the angle θn between that line segment and the north of the map, and if there are two or more line segments at approximately the same distance, indicate that with a log (
Step 521). In addition, the presence or absence of nearby intersections may also be determined here. Subsequently, it is determined whether the distance jm exceeds a preset threshold Jl th (step 522). If the error jm is not exceeded, the error jm is corrected, assuming that the current location is near the haboso line segment (step 523). This error ρm is calculated by the mileage sensor 3
This is due to detection errors in map data, digitization errors in map data, etc.

This modification is necessary to display the current location next time.
This is because it is necessary to cancel those errors by 15ffi. Thereafter, the process proceeds to a pattern pull-in routine to be described later.

On the other hand, if the distance jrn exceeds the threshold value ρth, then it is determined whether the vehicle has made a curve (turn right or turn left) (step 524). The curve detection method will be described separately later. If there is no curve, geomagnetic sensor 1
The difference between the traveling direction θ of the vehicle and the line segment angle θn obtained from the output data is compared with a set reference value 8th (step 525). If 1θ-θn 1>cth, proceed to the pattern pull-in routine without doing anything. In this case,
For example, a case may be considered in which the driver is heading towards the end of road T7 or is driving on a road that is not stored as map data. Next, it is determined whether there is a more difficult intersection with a smaller angle, such as a Y-junction, in the vicinity (step 826). For example, if there is a Y-junction in the vicinity, there is a possibility that the vehicle will be pulled into a road different from the one on which it is running, so the process proceeds to the pattern pull-in routine without doing anything.

The data indicating the difficulty of the intersection is calculated in advance from the intersection data as shown in No. 13I￥1(8) when converting the map into numerical values.
Since it is inserted in the ff ease level pit, the CPU 7 only has to check this pit 1- in step S26.

If the above two conditions do not apply, it is determined that an error has occurred in the sensor or the like and the route data is starting to deviate from the route data. In this case, the current location is corrected, that is, it is included in the road data (step 527).

As shown in Fig. 24, the new estimated point PCpd of the current location intersects with the perpendicular line drawn to the nearest neighbor line from the current estimated point Pcp calculated from the relative relationship from the previous estimated point Popd obtained from the sensor output. point, and change the display, etc. Distance Jam and coordinates of current estimated point PCD (X
m, Ym) are stored as correction values at that point for use in a pattern pull-in routine to be described later.

If it is determined in step S'24 that the vehicle has curved, the intersection pull-in routine is entered. First, the travel distance 11Lflc from the point previously displayed as an intersection is determined, and the product obtained by multiplying this travel distance 11jlc by a constant value aC is set as the intersection detection threshold ρCth (step 828). constant value a
C is a value related to the accuracy of the mileage sensor 3, for example 0
．． The value should be around 05.

Distance from current location Pcp to each intersection for intersection data included as map data! Find 1lifJc (
Step S29>, 'jl c <J) Determine whether an intersection cth exists (Step 530)
.

In step S30, a certain distance range (for example, several hundred [m
A judgment is also made as to whether or not the value is within 1). Here, if no intersection exists, the process proceeds to a pattern pull-in routine. In addition, it was determined that there were 11 nearby intersections and the distance Ac to the intersections was about the same, so it was determined that the nearby intersections could not be identified (
If step 531) is performed, the process also proceeds to the pattern pull-in routine.

If a nearby intersection is specified, that intersection is selected as a new current location estimation point p cpd (step 532). At this time, distance 1C to the intersection and current location P
The coordinates of cp (X c, Y c) are stored as a pull-in base. Furthermore, the estimated current location point pcpd is stored (updated) as a new displayed intersection. Thereby, when the current location of the vehicle deviates from one road on the map displayed on the display 12, the current location of the vehicle is forcibly placed on the intersection on the map, so-called intersection pull-in is performed.

Next, the distance and direction correction coefficients rs and θS are updated based on the coordinates of the intersection recognized last time, the sum of correction values therefrom, and the coordinates of the current location (step 533). In this way, if the distance and direction correction coefficients rs and θS are updated every time an intersection is recognized, or every time a certain distance 1p is traveled when the distance between intersections is long, more accurate current location estimation can be achieved. It becomes possible.

Next, pattern pull-in will be explained. This routine is executed after running a certain distance 1Ilpo. Distance lol
illpo has a value of 1000 [m], for example. Note that if intersection recognition is performed in step 331, the travel distance is reset.

While traveling a certain distance IJpo, the distance 11tftIm to the nearest line segment is measured n-j) po/Lo [times], and n error correction amounts ei are stored as data. Furthermore, for one measurement, the difference between the error correction 1ei-1 in the previous measurement and the current error correction mei is calculated as a change lci (ei - ei-1).

When it is determined that a certain distance 1jlfJpo has been run (step 534), the variation in the value of C1 is calculated at step $35), and then the deviation α6). and,
This value α is compared with a predetermined threshold αthh (step 537). This value α is determined by taking into account detection errors of each sensor, travel distance, and the like. If α>αthh, it is determined that pattern pull-in is not possible, and pattern pull-in is not performed. On the other hand, if α<αthh, it is further determined whether or not a pull-in is currently being carried out (step 838). If the pull-in is not being carried out, that is, if the current location is at a position outside of the road data, the nearest neighbor of the current location Retraction to the valve is performed (step 539). Furthermore, the threshold value αthh is compared with a similarly determined threshold value αthρ (step 540).
, α and αthΩ, the distance and direction correction coefficients rs and θS are updated (step 541).

With the above method, it is possible to re-enter another road after driving off the road. However, if you drive on a road that has not been digitized and then drive on a digitized road again, that road will be recognized after you have traveled a certain distance, making it possible to accurately estimate your current location. Also, for a fixed distance 1 po, a longer distance 1 po
Calculate the deviation for t and get the distance! It is also possible to shorten Jpo to increase the viscosity and shorten the response time. The situation is shown in FIG. 25 (A>, (B)).

As described above, the drawing to the nearest interception difference point and the drawing to the nearest line valve are performed. It is necessary to find out the difference.

Searching for the nearest interception difference point or nearest line valve takes time if there is a large amount of line segment or intersection data, that is, if the search area is wide, and the current location, which changes from moment to moment, cannot be displayed smoothly. Become. However, in this embodiment, as is clear from the data structures shown in FIGS. 2 to 5, the search area from the current location is made as small as possible, and the data of line segments and intersections that fall into that area are managed. By having data (section data, section table), it is possible to search for line segments and intersections within the minimum unit section as a reach area, thereby reducing the time required for the search. Hereinafter, the procedure executed by the CPU 7 to search for the nearest neighbor valve and the nearest intercept point from the current location will be explained according to the flowchart of FIG. 26.

First, the CPU 7 determines the current location (Crntx, Crnty
) to Territory No., (Tx,'ry), Unit No., (Nx, Ny), Section No., (Sx.

Sy) (step S50-852)
. This is because each area is divided into 2 units.
It can be determined by a simple calculation (division). Next, using the - section as a search area, the line segments and intersection data existing in this area are loaded by referring to the section table and section data (steps 853 to 853).
555). Based on the loaded data, calculate the distance from the current location to all line segments in the search area (the length of the perpendicular to the line segment) and the distance to all intersections, and compare them to calculate the nearest neighbor line. and the nearest interception difference point can be obtained (step 856). The speed of searching is proportional to the number of line segments and the number of intersections, but according to the search method based on the data structure described above, the number of sections is small, and the number of line segments to be calculated is Since the number of roads and intersections is small, high-speed searches are possible.

By the way, in a navigation system, when displaying maps of various scales, if map data of all scales is available, the display can be performed easily and quickly, but on the other hand, the data rise will be large. There is a disadvantage. On the other hand, if you only have map data at the largest scale and want to represent other scales by simple reduction,
Although the data size is smaller, the disadvantage is that the display is slower.

On the other hand, in this embodiment, as is clear from the data structure shown in FIGS. 8 to 10, in order to reduce the data size, only map data of the largest scale is included, and When displaying data, display management files and thinned data are used to speed up the display. Hereinafter, the procedure for enlarging/reducing the map executed by the CPU 7 will be explained according to the flowchart of FIG. 27.

First, the CPU 7 determines that the scale to be displayed has been entered manually from the input device 9 (step 560), and then calculates the area number (AnX, Any) corresponding to the scale from the current location (Crntx, Crnty) (step 861 to 563), then refer to the picture ID of that scale and step 864 to 866), load the map data according to the start address and data size, and
Each of the 16 areas on the RAM is drawn (step 567). In this way, picture ID for display management
The reference to the identified map data to be displayed is (
As the scale becomes smaller, it is possible to narrow down the displayed roads, place names, etc. to important ones), which makes it possible to speed up the display.

In addition, for polygon and line data, as explained in Figures 11 and 12, information to that effect is included in the thinning pits at points where it is okay to omit display, so When drawing maps of 1/100,000 or 1/100,000,
The thinned out bits are checked (step 868), and the points targeted for thinning are drawn (step 569). In this way, when the map is reduced, the number of line segments to be displayed can be reduced by thinning out the points that can be visually omitted when displayed on the display. This makes it possible to achieve faster speeds.

Note that in the above embodiment, thinning bits are provided for polygon and line data, and information to that effect is entered in the thinning pits at points where it is okay to omit display. Plot it with
The same effect can be obtained by thinning out images according to a predetermined rule (for example, skipping by one in the case of a scale of 1/50,000, skipping by four in the case of a scale of 1/100,000, etc.) at the time of display.

Next, step S2 in the flowchart of FIG.
The method for determining the curve (right turn/left turn) in No. 4 will be explained.

Basically, a right turn or a left turn is determined based on the output data of the azimuth sensor, for example, the geomagnetic sensor 1, and when a turn is detected, the intersection is pulled through the process from step 828 onwards. However, the geomagnetic sensor 1 is susceptible to external disturbances, and its output data will contain a large error when a large vehicle (for example, a truck or bus) passes over a railroad crossing, a railway bridge, or a large vehicle (for example, a truck or bus) on its own weight side. If this data is used as it is to judge whether to turn right or left, the vehicle will mistakenly think that the vehicle has turned when it was traveling straight and will pull into the intersection even though it is not even an intersection, causing the current location to deviate from the correct location.

Therefore, in this embodiment, the radius of curvature and vehicle speed are included in the criteria to determine whether the vehicle has turned.
This makes it possible to accurately judge whether to turn right or left. Below, C.P.
The procedure of the right-turn/left-turn judgment method executed by tJ7 will be explained according to the flowchart of FIG. 28. First, the CPU 7 moves from a certain distance (for example, 15 [m
)), when the vehicle hits a target at a certain angle (for example, 40 degrees) or more, it is determined that the vehicle has made a curve (turn right or left).
step 570). However, when a curve is made, the radius of curvature R at that time is a constant value Rm, which is the minimum radius of rotation of the judgment criterion.
in (for example, 3.5 [m]) or less,
It is determined that the data is wrong, and it is not determined that the data is curved (step S71).

This is because the vehicle cannot turn below its minimum turning radius. Furthermore, if the vehicle speed S exceeds a certain maximum judgment standard speed Smax (for example, 40 [Km/h]), it is normally unthinkable to turn at an intersection. (Step 572).Also, to determine whether to turn right or left, for example, if east is 0 degrees, north is 90 degrees, west is 180 degrees, and south is 270 degrees, then the direction is increased or decreased. (Step 573).In other words, the direction in which the bearing increases is a left turn (Step 574), and the direction in which the bearing decreases is a right turn (Step 575).
It is possible to determine a left turn.

Note that the radius of curvature R is determined at a certain point a, as shown in FIG.
θ[
radian], then Ω=R·θ, so it can be determined from the following equation R−ρ/θ obtained by modifying this equation.

In addition, the current location is controlled so that it is always located on the road shown on the map displayed on the display by the intersection pull-in process performed in accordance with the flow shown in Figure 22, but for example, if the distance between intersections is long, During this time, the current location will be slightly corrected, but due to distance errors due to sensor accuracy, division errors, map accuracy, etc., the distance between the actual current location from the last intersection and the current location on the map may vary. A difference occurs, and the error increases as the distance between intersections increases. In such a case, if there are a plurality of intersections close to each other in the vicinity of the intersection where the vehicle should pull in next, there is a possibility that the vehicle will pull in at the wrong intersection. In such a case, after the vehicle has traveled a certain distance between intersections, it may be possible to perform a so-called pull-in based on the travel distance. Hereinafter, the procedure will be explained according to the flowchart of FIG. 30.

First, initial values are set (step 580). As this initial value, a fixed current location is required, but this can be set by the user first, or the current location when pulling into a fixed point such as an intersection can be used, or if the current location has already been fixed, If you register the data in non-volatile memory, you only need to set it once. Reset the mileage to zero at this confirmed current location (Step 81), turn at an intersection (Step 582), and constantly monitor whether you have run a certain distance (Step 583). A point at a certain distance from the point on the map reset to zero (previously detected position) is found, the current location is changed to that point, and the pull-in is performed (step 584). While driving a certain distance, the vehicle's current location is drawn on the road on the map displayed on the display by drawing a perpendicular line to the line segment closest to the top and drawing it to the intersection (step 585). can be set. If it is detected that the vehicle has turned, the intersection pull-in is performed (step 886). This intersection lead-in is as described above.

In addition, the distance traveled can be effectively used to determine whether the vehicle has turned at an intersection. In other words, it is possible to determine a curved intersection from the map data based on the distance between the intersections and the travel distance.

! As explained above, according to the present invention, the correction coefficient for correcting the output data of the sensor that detects the traveling distance and direction of the vehicle is calculated from the previous detected intersection every time an intersection is detected or every time a predetermined distance is traveled. By updating based on the distance and angle information obtained from driving data and map data, the sensor output can always be corrected using the latest correction coefficient, so it is possible to always accurately detect the distance traveled and the direction of the vehicle. Become.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the configuration of an in-vehicle navigation device according to the present invention, Fig. 2(A) to (C) to Fig. 13(
A>, (B) are diagrams showing the data structure of map information stored in the recording medium in Fig. 1, and Figs. 14 (A) to (C)
! ; Figures 15 to 18 are flowcharts showing the basic procedures executed by the CPLJ in Figure 1; Figures 19 to 2 are diagrams showing the screen configuration on the tV-RAM;
1 is a diagram showing how to obtain the azimuth correction coefficient θS, and FIG. 22 is a flowchart 1 showing the procedure of the intersection drawing routine and pattern drawing routine executed by the CPU.
Figures 23 and 24 are diagrams showing the positional relationship between the current location and the nearest neighbor valve on the map, Figure 25 is a diagram showing other methods of drawing into the road, and Figure 26 is a diagram showing the positional relationship between the current location and the nearest neighbor valve. FIG. 27 is a flowchart showing the procedure for searching for an intersection; FIG. 27 is a flowchart showing the procedure for enlarging/reducing the map; FIG.
Figure 29 is a flowchart showing the procedure for determining whether to turn right or left. Figure 29 is a diagram showing how to determine the radius of curvature. Figure 30 is a flowchart 1 showing the procedure for pulling in by driving 20 distances.
− is. Explanation of symbols of main parts

Claims (1)

[Claims] A method for updating a correction coefficient for correcting output data of a sensor that detects the travel distance and direction of a vehicle, the method comprising: digitizing each position on a road and an intersection position on a map and storing it as map data; The nearest intersection on the road from the current location determined based on the output data of is detected from the map data, and this detected intersection is set as the current location on the map, and each time this intersection is detected or every time a predetermined distance is traveled, A method for updating a sensor correction coefficient, characterized in that the correction coefficient is updated based on travel data from a previously detected intersection and distance and angle information obtained from the map data.