JP2604394B2 - In-vehicle navigation system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle navigation device that introduces weighting based on traffic frequency in determining a branch approach road.

[Prior Art] An on-vehicle navigation device that displays the current position of a vehicle together with a road map on a display device in a vehicle cabin to help guide the destination of the vehicle uses radio waves from satellites, geomagnetism, and the like. It can be included in a broadly defined navigation system that estimates the current location of a moving object.

The conventional on-vehicle navigation device 1 shown in FIG. 3 is based on current position estimation by a central processing unit 4 to which a direction sensor 2 and a traveling distance sensor 3 are connected. A road map read from a map information recording medium 6 such as a CD-ROM via a reading device 5 called a media controller is temporarily stored in a buffer memory 7 and then displayed on a screen of a display device 8 together with an estimated current position. . The display device 8 controlled by the display control device 9 can display the road map data near the current position stored in the image memory 10, and performs key operations on the keyboard device 11 connected to the central processing unit 4. , The route closest to the line connecting the departure point and the destination at the shortest distance can be displayed together. For this reason, the driver can select a route to the destination while comparing the shortest distance route to the destination displayed on the screen of the display device 8 with the estimated current location.

[Problems to be Solved by the Invention] In the above-described conventional on-vehicle navigation device 1, there is a certain limit in the measurement accuracy of the direction sensor 2 and the traveling distance sensor 3,
With the lapse of time after the start of driving, there has been a problem that cumulative errors accumulate in the azimuth and running distance of the vehicle. For this reason, at present, as a method of matching the estimated travel trajectory to the actual travel trajectory of the vehicle as much as possible, for example, when the vehicle passes an intersection or a corner, the map information recording medium 6
The road data recorded in the vehicle is compared with the estimated travel trajectory, and if it is objectively found that the estimated current position of the vehicle is shifted, it is estimated to be the most appropriate point conceivable from the surrounding road conditions. Combined use of the so-called map matching method, in which the present location is forcibly relocated, has been regarded as a promising effective method to cope with the weak point of the estimated navigation.

However, such a map matching method also requires that, for example, when a vehicle goes straight over a long distance and then turns on one of a plurality of adjacent branch roads, it immediately enters the branch road closest to the estimated approach road on the road map. Because the road is determined as a road, the correct branch road that is slightly away from the estimated approach road is not selected, and an alley or a private road that is hardly used for vehicles may be selected. There has been a problem that the misalignment causes the subsequent estimation operation to be fundamentally out of order.

[Means for Solving the Problems] The present invention solves the above problems, and is an in-vehicle navigation device for estimating a current position of a vehicle based on outputs of a direction sensor and a mileage sensor. When entering a branch road, a branch road that is a candidate for an entrance road is selected on the road map, and the distance difference from the estimated approach road determined for each branch road is set in advance for each branch road. And a branch approach determining means for determining a branch road having the smallest obtained value as an estimated approach is provided.

[Operation] The present invention selects a branch road that is a candidate for an entrance road on a road map when a vehicle enters a branch road, and calculates a distance difference from an estimated approach road calculated for each branch road. By dividing by the traffic frequency preset for each branch road and determining the branch road with the smallest obtained value as the estimated approach road, an objective and highly appropriate branch approach determination based on the reality is determined. Do.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing an embodiment of the on-vehicle navigation device according to the present invention, and FIG. 2 is a flowchart for explaining a branch approach road determination operation by the central processing unit shown in FIG. is there.

In FIG. 1, the on-vehicle navigation device 21 is configured such that the actual traffic frequency is quantified and introduced into the branch approach determination by the central processing unit 22. That is, the central processing unit 22
When a vehicle enters a branch road, a branch road that is a candidate for an entrance road is selected on the road map, and the distance difference from the estimated approach position determined for each branch road is determined in advance for each branch road. Dividing by the set traffic frequency, the branch road with the smallest obtained value is determined as the estimated approach road.

The traffic frequency of a road is a value that can be said to be a probability of passing through the road in order to reach a destination in an actual traffic system, and is determined in consideration of various factors described below. In the embodiment, first, the road is a national road, a prefectural road, or a general road or a private road.
Classify according to the road management entity, and furthermore, the road width and 1
The traffic frequency is determined taking into account the daily traffic volume. The traffic frequency is a national highway and has three or more lanes.
In addition, roads with continuous traffic for 24 hours are classified as 100, with 100 being the highest, and alleys and private roads with the least traffic being the lowest, and having a minimum frequency of 1 of 100. The value recorded on the medium 6 is used.
The passing frequency is a dimensionless number.

Now, it is assumed that on the road map displayed on both sides of the display device 8 shown in FIG. 1, it is estimated that the vehicle has made a right turn at approximately the middle point between the roads A and B having traffic frequencies of 30 and 10, respectively. In this case, the distance difference between the estimated approach road and the roads A, B, and C, which are candidates for the approach road, is calculated according to step (101) shown in FIG. It is assumed that the road C is 7 m.

In an actual determination step, in a step (102) following the step (101), only the branch roads A and B having a stable running angle and a road angle of, for example, 20 degrees or less after the vehicle enters the branch road are selected. This is because the road angle is also an important determination factor in the map matching method, and branch road candidates can be narrowed down by excluding the road C whose road angle is far from the stable traveling angle from the candidates.

Two branch roads A and B remaining after sorting by road angle
Is corrected in step (103) to 0.3 m and 0.5 m, respectively, by dividing the distances 9 m and 5 m from the estimated approach road by a preset traffic frequency. As a result, the road A, which is actually far from the estimated approach road, approaches the estimated approach road after being corrected by the traffic frequency. The corrected value of the distance difference obtained in step (103) is subjected to minimum value selection in step (104). By selecting the branch road A having the minimum corrected value, the approach road becomes the branch road A. Is determined.

As described above, when the vehicle enters the branch road, the on-vehicle navigation device 21 selects the branch road A or B which is a candidate for the entrance road on the road map, and selects each of the branch roads A and B. The distance difference from the estimated approach road calculated for each branch road is divided by the traffic frequency preset for each branch road, and the branch road A with the smallest obtained value is determined as the estimated approach road. However, the branch road B having the smallest distance difference from the estimated approach position is not determined to be the immediate approach road, but the branch road candidate weighted by the reciprocal of the traffic frequency set based on the road width and the traffic volume. Among them, the branch road A, which is considered to be most appropriate objectively, can be determined as the branch approach road, and the estimation error based on the accumulated error of the mileage sensor 3 can be improved, as well as the estimation navigation accuracy. ,road Through the resilient operation of the map matching method in line with the situation, it is possible to accurately correct.

[Effects of the Invention] As described above, according to the present invention, when a vehicle enters a branch road, a branch road that is a candidate for an entrance road is selected on a road map, and an estimation is performed for each branch road. The distance difference from the approach road is divided by the traffic frequency preset for each branch road, and the branch road with the smallest obtained value is determined to be the estimated approach road. The branch road with the smallest distance difference is not determined to be an immediate approach road, but among branch road candidates weighted with the reciprocal of the traffic frequency set based on the width of the road and the amount of traffic, objectively The most appropriate branch road can be determined as a branch approach road, thereby improving the estimated navigation accuracy as well as the estimation error based on the accumulated error of the mileage sensor. Through the flexible operation of the map matching method adapted to the road conditions, excellent effects such as accurate correction can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a vehicle-mounted navigation device according to the present invention. FIG. 2 is a flowchart for explaining a branch approach determination operation by the central processing unit shown in FIG. FIG. 3 is a circuit diagram showing an example of a conventional on-vehicle navigation device. 2 azimuth sensor, 3 mileage sensor, 21 navigation system for vehicle, 22 central processing unit.

Claims (1)

(57) [Claims] 1. An on-vehicle navigation device for estimating a current position of a vehicle based on outputs of a direction sensor and a mileage sensor,
When a vehicle enters a branch road, a branch road that is a candidate for an entrance road is selected on a road map, and a distance difference from an estimated approach road determined for each branch road is set in advance for each branch road. An on-vehicle navigation device provided with branch approach road determination means for dividing a branch road having the smallest value as an estimated approach road by dividing by a predetermined traffic frequency.