JPH01175100A - Steering device for on vehicle - Google Patents

Abstract

PURPOSE:To improve the accuracy of an estimated steering method by dividing a branch road candidate by a previously set passage frequency and deciding a branch road having the minimum value as an estimated advancing road. CONSTITUTION:When it is estimated that a vehicle is turned to right on an approximately intermediate position between roads A, B respectively having passage frequency values 30, 20 on a road map displayed on the screen of a display device 8, a CPU 22 selects the roads based on load angles and converges the branch road candidates into A and B. Then, distance difference from estimated advancing roads found out in respective roads A, B are divided by the passage frequency values previously set in each branch roads and the branch road having the minimum value is decided as an estimated advancing road.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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] In-vehicle navigation systems that display the vehicle's current location along with a road map on a display device inside the vehicle to help guide the vehicle to its destination utilize radio waves from satellites, geomagnetism, etc. It can be included in a navigation system in a broad sense that estimates the current location of a moving object.

The conventional in-vehicle navigation device l shown in FIG.
The current location is basically estimated by a central processing unit 4 connected to a mileage sensor 3 and the like. CD-ROM through a reading device 5 called a media controller.
The road map read from the map information recording medium 6 such as
- After being stored in the buffer 7 memory 7, it is displayed on the screen of the display device 8 together with the estimated current location. A display device 8 controlled by a display control device 9 can display road map data near the current location stored in an image memory 10, and can be operated by key operations on a keyboard device ll connected to the central processing device 4. The route closest to the line connecting the departure point and destination in the shortest distance can also be displayed. Therefore, the driver can select a route to the destination while comparing the estimated current location with the distance M shortest route to the destination displayed on the screen of the display device 8.

[Problems to be Solved by the Invention] In the above-mentioned conventional vehicle-mounted navigation device, there is a certain limit to the measurement accuracy of the direction sensor 2 and the mileage sensor 3. There was a problem with cumulative errors accumulating in the direction and distance traveled. For this reason, currently, as a method of matching the estimated travel trajectory with the actual vehicle travel trajectory as much as possible, for example, when the vehicle passes an intersection or a corner, road data recorded on the map information recording medium 6 is used. Compare it with the estimated travel trajectory,
If it is determined objectively that there is a discrepancy in the estimated current location of the vehicle, it is possible to use the so-called map matching method, which forcibly relocates the estimated current location to the most appropriate location based on the surrounding road conditions. , it has come to be seen as a promising method as an effective method to address the weaknesses of dead reckoning navigation.

However, even with this map matching method, for example, when a vehicle has traveled straight for a long distance and then turns onto one of several nearby branch roads, it immediately enters the branch road closest to the estimated approach road on the road map. Therefore, the correct branch road that is slightly away from the estimated approach road may not be selected, and an alley or private road that is of little use for vehicle traffic may be selected. There was a problem in that a matching error fundamentally disrupted subsequent estimation operations.

[Means for Solving the Problems] The present invention solves the above problems, and is an in-vehicle navigation device that estimates the current location of a vehicle based on the outputs of a direction sensor and a mileage sensor. When entering a branch road, the system selects a branch road that is a candidate for the approach road on the road map, and sets the distance difference between the estimated approach road and the calculated approach road for each branch road in advance for each branch road. The present invention is characterized in that a branch approach road determining means is provided for determining the branch road with the smallest obtained value as the estimated approach road.

[Operation] When a vehicle enters a branch road, this invention selects a branch road that is a candidate for the approach road on the road map, and calculates the distance difference between the branch road and the estimated approach road determined for each branch road. is divided by the traffic frequency set in advance for each branch road, and the branch road with the smallest value is determined to be the estimated approach road.By doing so, the branch road with high objective validity based on reality is determined. Make a judgment.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. 1.2. FIG. 1 is a circuit configuration diagram showing an embodiment of the on-vehicle navigation system of the present invention, and FIG. 2 is a flowchart for explaining the operation of determining a branch approach road by the central processing unit shown in FIG. 1. be.

In FIG. 1, an on-vehicle navigation device 21 is configured to quantify the actual traffic frequency and introduce it into the branch entry judgment by the central processing unit 22. That is, the central processing unit 2
2, when a vehicle enters a branch road, selects a branch road that is a candidate for the approach road on the road map, and calculates the distance difference between the branch road and the recommended approach position calculated for each branch road. The branch road with the smallest obtained value is determined to be the estimated approach road.

The traffic frequency of a road is a value that can be said to be the probability of passing through that road to reach a destination in an actual transportation system, and is determined by considering various factors shown below. In the example, first, the road is determined by whether it is a national highway, a prefectural road, a general road or a private road, etc.
Classified according to road management entity, and further classified according to road width and 1
The frequency of traffic is determined by taking into account the daily traffic volume. The frequency of traffic is on a main road bordering a national highway with three or more lanes.
What's more, the 10 best roads have 24-hour traffic.
0, and alleys and private roads with the least amount of traffic have the lowest traffic frequency of 1, which are classified into classes with a total of lOO, and the values recorded in the map information recording medium 6 attached to the road map data are used. Note that this traffic frequency is a dimensionless number.

Now, on the road map displayed on the screen of the display device 8 shown in Fig. 1, the traffic frequencies are 30 and 20, respectively.
Assume that it is estimated that the vehicle turned right at approximately the halfway point between roads A and B. In this case, step (1) shown in Fig.
According to 01), the distance difference between roads A, B, and C, which were candidates for approach roads, and the estimated approach road was determined, and road A was 9 m.

Assume that road B is 5 m long and road C is 7 m long.

In the actual determination step, in step (102) following step (101), only branch roads A and B whose stable running angle of the vehicle after entering the branch road and the road angle are within 20 degrees, for example, are selected. This is because the road angle is also an important determining factor in the map matching method, and by excluding the road C whose road angle is far from the stable running angle from the candidates, it is possible to narrow down the branch road candidates.

Two branch roads A and B remaining after sorting by road angle
In step (103), the distance difference between the estimated approach road and the approach road is 9 m and 5 m with the preset traffic frequency.
are corrected to 0.3m and 0.25m, respectively. As a result, road A, which was actually far away from the estimated approach road, becomes closer to the estimated approach road due to the correction based on the traffic frequency. The distance difference correction value thus obtained in step (103) is subjected to minimum value selection in step (+04), and by selecting the branch road A with the minimum correction value, the approach road is changed to the branch road A. It is determined that

In this way, when the vehicle enters a branch road, the on-vehicle navigation device 2I selects branch road A or B, etc., which is a candidate for the approach road on the road map, and The difference in distance from the estimated approach road calculated for each branch road is divided by the preset traffic frequency for each branch road, and the branch road A with the smallest value is determined to be the estimated approach road. , instead of simply determining the branch road B with the smallest distance difference from the estimated approach position as a detour entry road, the branch road is weighted with the reciprocal of the traffic frequency set based on the width of the road and the amount of traffic. From road candidates, a branch road that is objectively considered to be appropriate can be determined as a branch approach road, which not only improves the estimated navigation accuracy but also improves estimation based on the cumulative error of the mileage sensor 3. Errors can be corrected accurately through flexible application of the Map Matching method according to road conditions.

[Effects of the Invention] As explained above, the present invention selects a branch road that is a candidate for an approach road on a road map when a vehicle enters a branch road, and calculates an estimate for each branch road. The difference in distance from the approach road is divided by the preset traffic frequency for each branch road, and the branch road with the smallest value is determined to be the estimated approach road, so it is simply the estimated approach position. A branch road with a small distance difference will not be judged as a detour, but instead it will be objectively selected from among branch road candidates weighted by the reciprocal of the traffic frequency set based on the width of the road and the amount of traffic. The branch road that is considered to be the most appropriate can be determined as the branch approach road, which not only improves the estimated navigation accuracy but also reduces the estimation error based on the cumulative error of the mileage sensor.
Through flexible operation of the map matching method according to road conditions, excellent effects such as accurate correction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the on-vehicle navigation system of the present invention, and FIG. 2 is a flowchart for explaining the branch approach road determination operation by the central processing unit shown in FIG. 1. FIG. 3 is a circuit configuration diagram showing an example of a conventional vehicle-mounted navigation device. 291. Orientation sensor, 3. ,,Odometer sensor. 21., Vehicle navigation device, 22. ,,central processing unit.

Claims (1)

[Claims] This is an in-vehicle navigation device that estimates the vehicle's current location based on the output of a direction sensor and a mileage sensor, and when a vehicle enters a branch road, it selects a branch road on a road map as a candidate for the approach road. , the distance difference from the estimated approach road calculated for each branch road is divided by the preset traffic frequency for each branch road, and the branch road with the smallest value is determined as the estimated approach road. An on-vehicle navigation device provided with an approach route determining means.