JPH0789062B2 - Vehicle navigation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle navigation device for informing a driver of the current position of a vehicle such as an automobile on a road map displayed on a display device.

[Conventional technology]

2. Description of the Related Art Conventionally, a vehicle navigation device has been proposed that informs a driver of the current position of a vehicle such as an automobile running on a road.

In this navigation device, for example, a high-precision position detecting device such as a so-called gyro is used to accurately detect the current position of the vehicle directly, and the detection result is a cathode ray tube in which a translucent road map is superimposed on the display unit ( It was displayed by plotting on a display device such as CRT).

[Problems to be solved by the invention]

By the way, in the navigation device as described above, if the accuracy of the position detection device that detects the current position of the automobile is low, an error occurs and the current position displayed on the display device does not match the actual current position. Will end up. For this reason, it is generally necessary to use an expensive and highly accurate position detecting device. Further, when the current position of the vehicle is out of the area of the road map that is overlaid on the display unit of the display device, it has to be replaced with another road map, which is troublesome.

Therefore, the present invention has been proposed in view of the above-mentioned conventional problems, and makes it possible to accurately display the current position of an automobile without using a highly accurate position detection device, and to reduce the cost. With the goal. Another object is to eliminate the trouble of exchanging road maps and improve the ease of use.

[Means for Solving the Problems]

A vehicle navigation device according to the present invention includes a current position detecting means for detecting a current position of a vehicle, a storage device in which road map information is stored, an output of the current position detecting means, and a read from the storage device. An arithmetic processing unit that calculates the current position information based on the issued road map information, and displays the road map information read from the storage device and displays the current position on the displayed road map according to the current position information. And a display device for displaying the current position of the vehicle detected by the current position detection means and the position on the road according to the road map information. The road with the shortest distance to the position is selected, and the current position of the vehicle is corrected so as to be located on the selected road.

[Action]

The vehicle navigation device according to the present invention is based on the current position information based on the output of the current position detection means for detecting the current position of the vehicle and the road map information read from the storage device storing the road map information. Is calculated by the arithmetic processing unit. This arithmetic processing unit compares the current position of the vehicle obtained from the current position detection unit with the position on the road based on the road map information, and determines the shortest distance from the current position of the vehicle detected by the current position detection unit. The road is selected, and the current position of the vehicle is corrected so as to be located on the selected road.

〔Example〕

Hereinafter, specific embodiments of a vehicle navigation device according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a navigation device installed in an automobile in this embodiment. In FIG. 1, a direction detecting device 1 for detecting a traveling direction of an automobile (not shown) and a running amount detecting device 2 for detecting a running amount are respectively present position calculating circuits for calculating a present position as described later. Connected to 11. The traveling amount detection device 2
For example, a range finder that detects the rotation of the tire may be used. Further, as the direction detecting device 1, for example, a direction detecting device utilizing earth magnetism as shown in FIG. 2 may be used. That is, the clock generator 21 for generating the clock signal φ is connected to the binary counter 22. The counter 22 is an n-bit (n = natural number) counter having outputs A _{0 to} A _n−1 , and each read-only memory (ROM; Read Only) via n address buses.
Memory) 23, 24 and latch 25, respectively. ROM23 and 24 are both 2 ⁿ × k bit words (k = natural number)
The quantized unit of sine wave (sin wave) in ROM23 and cosine wave (cos wave) in ROM24 is equally divided into 1/2 ^{n in the} time axis direction and 1/2 ^{k in} the amplitude axis direction. The data quantized in is written. That is, in each ROM23, 24, the counter
The n-bit output from 22 serves as an argument (address) of the function, and accordingly, the k-bit function value is output.

The ROM23 is a digital / analog converter (D / A converter) 26
Is further connected to a current driver 29 via a low-pass filter 27 and a semi-fixed resistor 28 for current adjustment. On the other hand, the ROM 24 is connected to the D / A converter 30, and further includes a low-pass filter 31 and a semi-fixed resistor for current adjustment.
It is connected to the current driver 33 via 32. Each of the current drivers 29, 33 is a Hall element 41, which is a magnetic detection element.
42 connected to each. The Hall elements 41, 42 are arranged so that the directions of the detection axes (shown by broken lines in the figure) of the Hall elements 41, 42 are orthogonal to each other. The Hall elements 41 and 42 are connected to the input terminals of the amplifiers 43 and 44, respectively, and the output terminals of the amplifiers 43 and 44 are the difference signal amplifier 4
5 are connected to the non-inverting input terminal and the inverting input terminal, respectively. The output terminal of the difference signal amplifier 45 is connected to the latch 25 via a zero cross comparator 46 that detects the zero cross point of the output signal from the difference signal amplifier 45.

This direction detecting device operates as follows. The clock signal φ generated by the clock generator 21 is sent to the counter 22. The counter 22 performs a counting operation according to the clock signal φ, and outputs n bits of A _{0 to} A _n-1 to the sine wave ROM 23, the cosine wave ROM 24, and the latch 25 via the address bus. Sent. In response to the n-bit output from the counter 22, the ROM 23 outputs k-bit sine wave forming data, and the ROM 24 outputs k-bit cosine wave forming data. The sine wave forming data is sent to the D / A converter 26 and converted into an analog value, and then the low pass filter 27 performs waveform shaping to obtain a smooth sine wave signal. This sine wave signal is sent to the current driver 29 via the semi-fixed resistor 28, and the current driver 29
The control current is supplied to the Hall element 41 by 29. On the other hand, the data for forming the cosine wave is sent to the D / A converter 30 and converted into an analog value, and then the waveform is shaped by the low pass filter 31 to obtain a smooth cosine wave signal. This cosine wave signal is sent to the current driver 33 via the semi-fixed resistor 32, and is supplied as a control current to the Hall element 42 by the current driver 33. Then, the earth magnetism is detected by the Hall elements 41, 42.

Here, the detection of the geomagnetism by the Hall elements 41 and 42 will be described with reference to FIG. The direction of the detection axis of the Hall element 41 and the direction of the detection axis of the Hall element 42 are orthogonal to each other, as described above. Now, the geomagnetism of the magnetic flux density B _G is parallel to the paper surface, and if the angle formed by the direction of the geomagnetism and the detection axis of the Hall element 42 is θ (rad), the magnetic flux density B detected by each Hall element 41, 42 active ingredients of _G are each B _G · sin
θ, B _G · cos θ. The current value of the sine wave signal supplied from the current driver 29 to the Hall element 41 is i _A = i ·
Let sinωt, and let the current value of the cosine wave signal supplied from the current driver 33 to the Hall element 42 be i _B = i · cosωt.
Then, the detection voltages E _A and E _B obtained by the Hall elements 41 and 42 are as shown below.

E _A = i _A・ C _A・ B _G・ sinθ ＝ i ・ sinωt ・ C _A・ B _G・ sin θ ………… Equation 1 E _B = i _B・ C _B・ B _G・ cos θ = i ・ cosωt ・ C _B · B _G · cos θ ··· Second formula Here, C _A and C _B are coefficients for magnetic-voltage conversion, respectively.

The detected voltages E _A and E _B obtained by the Hall elements 41 and 42 are amplified by the amplifiers 43 and 44, respectively. When the gains of the amplifiers 43 and 44 are both G, the output signals are Y _A = G · E _A = G · C _A · B _G · i · sin ωt · sin θ ··· Formula 3 Y _B = G · E _B = G · C _B · B _G · i · cosωt · cosθ ·········· Equation 4 Here, since the Hall elements 41 and 42 are usually of the same standard, C _A = C _B = C, and G · C · B _G
When ≡A is set, the third and fourth equations are as follows.

_{Y A = A · i · sinωt} · sinθ ............... Equation 5 _{Y B = A · i · cosωt} · cosθ ............... sixth equation of these signals Y _A, Y _B is the difference signal amplifier 25 To form the difference signal Y.

_{Y = Y B -Y A = A} · i (cosωt · cosθ-sinωt · sinθ) = A · i · cos (ωt + θ) , where ............... seventh equation, as shown in FIG. 2 again, the The difference signal Y is sent to the zero cross comparator 46, and the zero cross point is detected. Then, according to the detection timing of the zero-cross point by the zero-cross comparator 46,
The address of M23, 24 (output of the counter 22) is latched, and 2π (rad), that is, an angle of 360 ° is output with n-bit resolution. Thereby, the value of the angle θ or θ + m × 90 ° (m = integer) can be obtained. This is because the current value i _B = i · cosωt of the cosine wave signal supplied to the Hall element 42 and the difference signal Y =
It is nothing but the phase comparison with A · i · cos (ωt + θ).

In this way, the angle θ formed by the direction of the geomagnetism and the detection axis of the Hall element 42, that is, the traveling direction of the vehicle can be obtained.

Here, returning to FIG. 1, the description will be continued. The ROM 3 is a memory for storing road map information. For example, the road map information is written in a format in which intersections are nodes and roads connecting each intersection are branches. An example will be described with reference to FIG. 4 and Table 1 shown below.

That is, assuming that the road has a pattern as shown in FIG. 4, each intersection is defined as each node N _{1 to} N _5, and the road connecting each intersection is defined as each branch B _{1 to} B _6. . Then, as shown in Table 1, each of the nodes N _{1 to} N ₅ has x
Information is shown in the coordinates and y coordinates, and each branch B ₁
~ B ₆ is represented by information of two nodes among the nodes N _{1 to} N ₅ , for example, in the case of branch B ₁ , information of nodes N ₁ and N ₂ ,
These pieces of information are written in the ROM 3 as road map information. In this example, an extremely small area has been described in principle, but in reality, a huge amount of information having a resolution of several meters or less is written in the ROM 3 over a wide area of several 100 km or more. Further, access information for selectively searching for a desired area is also written in this ROM3. A compact disc (CD) system can be used for the ROM 3, for example.

The ROM 3 is connected to a buffer memory 12 that stores information from the ROM 3 in image units, and is also connected to a ROM controller 13 that controls the operation of the ROM 3.
The buffer memory 12 is connected to a display controller 14 that controls driving of the display device 4 such as a cathode ray tube and a liquid crystal display. The display device 4 is provided, for example, as shown in FIG. 5, at a substantially central position of the dashboard 100 provided in the automobile of this embodiment. The buffer memory 12 is connected to the current position calculation circuit 11. The system controller 15 to which the operation key 5 for initial setting is connected is connected to the current position calculation circuit 11, the buffer memory 12, the ROM controller 13, and the display controller 14, respectively, and controls each unit. The current position calculation circuit 11, buffer memory 12, ROM controller 1
3, the display controller 14, and the system controller 15 constitute the arithmetic processing unit 10.

Next, the operation will be described. First, the initial current position (initial value) is set by operating the operation key 5 before traveling of the automobile. That is, with the operation key 5
A desired road map is accessed and searched from the road maps stored in the ROM 3, and the road map is displayed on the display device 4. Then, the operation key 5 is further operated to plot and display the current position on one point of the road map on the display device 4.

While the vehicle is running, the direction detection device 1 supplies the traveling direction detection data and the traveling amount detection device 2 supplies the traveling amount detection data to the current position calculation circuit 11. The current position calculating circuit 11, the current time t _{n + 1,} the data of the variation with respect to data in the time t _n of the data at ₊₁ time Delta] t (e.g., 0.1 seconds) before time t _n (.DELTA.l,
θ, Δt) is sent to the system controller 15. Here, Δl represents the traveling amount, θ represents the traveling direction, and Δt represents the sampling time.

For example, as shown in FIG. 6, it is assumed that the position at time t _n is at point P _n on branch B _n . If the position detected by the direction detecting device 1 and the traveling amount detecting device 2 at time t _{n + 1} deviates from the branch B _n to the point X _{n + 1} without exceeding the node N _n , the current position is detected. The present position is corrected by the arithmetic circuit 11 from the point X _{n + 1} to the point P _{n + 1} on the branch B _n and displayed on the display device 4.
This is based on the premise that a vehicle always travels on a road (branch).

Further, as shown in FIG. 7, it is assumed that the position at time t _n is at point P _n on branch B _n . Then, the detection position at the time t _{n + 1} by the direction detection device 1 and the travel amount detection device 2 exceeds the node N _n and deviates from the branch B _{n at} a point X.
_When it becomes _{n + 1} , the current position calculation circuit 11 searches for a branch connected to the node N _n . here,
If three branches B _a , B _b , B _c were found, the current position would be on any of these branches B _a , B _b , B _c . This is because, as described above, it is premised that an automobile always travels on a road (branch). Next, the points P _{an + 1} , P _{bn + 1} , and P _{cn + 1} on the branches B _a , B _b , and B _c that are Δl apart from the point P _{n at} the time t _{n + 1} are obtained, respectively. At the same time, the distances Δl _{an + 1} , Δl _{bn + 1} , from the point X _{n + 1} to each point P _{an + 1} , P _{bn + 1} , P _{cn + 1}
Δl _{cn + 1} is calculated respectively. Then, the point having the smallest value among the distances Δl _{an + 1} , Δl _{bn + 1} , and Δl _{cn + 1} (any one of P _{an + 1} , P _{bn + 1} , and P _{cn + 1} ) is currently It is likely to be a position. However, in order to perform an accurate representation, further time t _{n +} detection position in the _two points X _{n + 2} each branch from B _a, B _b, each point on the _{B c P an + 2, P} bn + 2, P _{cn + 2} and the respective distances Δl _{an + 2} , Δl _{bn + 2} , Δl _{cn + 2} are obtained, and the sum of the distances Δl _{an + 1} + Δl _{an + 2} , Δl _{bn + 1} + Δl _{bn + 2} , Δl _{cn + 1} + Δl
_The point with the smallest value of _{cn + 2} (in this case P _{an + 2} ) is selected and the current position is modified from point X _{n + 2} to point P _{an + 2} on branch B _a and displayed. It is designed to be displayed on the device 4. In consideration of the detection error of the traveling amount by the traveling amount detecting device 2, for example, by setting the point where the direction detecting device 1 detects a large change in the traveling direction, such as an automobile turning at an intersection at a right angle, as a node,
It is possible to more accurately display the current position. As described above, in the navigation device of this embodiment, the vehicle operates on the premise that the vehicle always travels on the road.

Further, when the current position of the vehicle is about to extend from the area of the road map displayed on the display device 4, the current position calculation circuit 11 detects this.
Then, the ROM controller 13 reads out new road map information from the ROM 3, and a new road map suitable for the traveling direction of the automobile is displayed on the display device 4 via the buffer memory 12 and the display controller 14. Has become.

According to the vehicle of the present embodiment equipped with the navigation device as described above, the direction detecting device 1 as the position detecting device 1
And comparing the detection information from the direction detecting device 1 and the traveling amount detecting device 2 with the road map information from the ROM 3 in the arithmetic processing device 10 without using a highly accurate traveling amount detecting device 2. With this, the current position of the automobile can be corrected and accurately displayed, so that the cost can be reduced. Further, when the current position of the vehicle is about to extend from the area of the road map displayed on the display device 4, a new road map that automatically matches the traveling direction of the vehicle is displayed. The ease of use can be improved without the trouble of exchanging road maps as in the conventional case. Further, as described above, if the compact disc system is installed in the ROM 3, the cost of hardware other than the compact disc system can be considerably reduced.

〔The invention's effect〕

As described above, in the vehicle navigation device according to the present invention, the arithmetic processing device compares the current position of the vehicle obtained from the current position detecting means with the position on the road based on the road map information, and detects the current position detecting means. The road that has the shortest distance to the current position of the vehicle detected by is selected, and the current position of the vehicle is corrected so that it is located on the selected road. Can always be accurately displayed on the road map displayed on the display device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a navigation device according to the present invention, and FIG. 2 is a block diagram showing an example of a direction detecting device applied to the navigation device according to the present invention. FIG. 4 is a schematic diagram showing the positional relationship between the Hall element and the geomagnetism in the direction detecting device shown in FIG. 2, and FIG. 4 is a schematic map of the road map for explaining the format of the road map information written in the ROM of the navigation device. 5 and 5 are schematic diagrams schematically showing the periphery of the dashboard of the automobile of this embodiment, and FIGS. 6 and 7 are schematic diagrams of a road map for explaining the operation of the navigation device. FIG. 6 shows the case _{where the} detected position does not exceed the node N _n, and FIG. 7 shows the case where the detected position exceeds the node N _n . 1 ... Direction detection device 2 ... Travel amount detection device 3 ... ROM 4 ... Display device 5 ... Operation key 10 ... Calculation processing device

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-59-119377 (JP, A) JP-A-57-135972 (JP, A) JP-A-57-20681 (JP, A) JP-A-58- 132612 (JP, A) JP 60-45285 (JP, A) JP 58-129313 (JP, A)

Claims (1)

[Claims] 1. A current position detecting means for detecting a current position of a vehicle, a storage device in which road map information is stored, an output of the current position detecting means and road map information read from the storage device. An arithmetic processing unit for calculating the current position information based on the above, and a display unit for displaying the road map information read from the storage unit and for displaying the current position according to the current position information on the displayed road map. In the arithmetic processing device, the current position of the vehicle obtained from the current position detection means is compared with the position on the road based on the road map information, and the distance between the detected current position of the vehicle is the shortest. The road navigation device for a vehicle, wherein the road is selected, and the current position of the vehicle is corrected so as to be located on the selected road.