JPS63177013A - Navigation apparatus of car - Google Patents

Abstract

PURPOSE:To automatically correct the azimuth detected by an earth magnetism sensor, by utilizing a signal informing the azimuth of a road during the running of a vehicle transmitted from a sign post as the data relating to a running azimuth. CONSTITUTION:In a vehicle during running, the running azimuth of the vehicle is detected by an earth magnetism sensor 1 and, when the vehicle comes to the vicinity of the sign posts SP (SP1, SP2...) provided at important points of a road, the signal informing the azimuth of the road during the running of the vehicle transmitted from each of the sign posts SP is received by a receiver 4. Then, on the basis of he azimuth obtained from said signal, the azimuth theta detected by the sensor 1 is corrected by a control circuit 5. By this method, the azimuth detected by the sensor 1 is automatically corrected and the confirmation of the running azimuth is easily and accurately performed. Therefore, the confirmation accuracy in the confirmation of the present position of the vehicle utilizing the earth magnetism sensor 1 is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a navigation device for a vehicle, and particularly to a navigation device configured to detect the running direction of a vehicle using geomagnetism.

(Conventional technology) Car navigation 8I! For example, as disclosed in Japanese Unexamined Patent Application Publication No. 58-70117, a vehicle is known that displays the current location of the vehicle and a map of its surroundings on the screen of a display device to provide travel guidance.

As means for recognizing the current position of a vehicle in such a navigation device, one using a geomagnetic sensor has already been put into practical use. That is, the current position recognition means is capable of recognizing the current position of the vehicle by detecting the distance traveled and the direction of the vehicle from the reference position using the odometer and the geomagnetic sensor, It can be constructed at relatively low cost.

(Problem to be Solved by the Invention) However, the current position recognition means using the geomagnetic sensor as described above employs so-called dead reckoning navigation, which recognizes the current position of the vehicle as a relative position to a reference position. Therefore, as the vehicle moves away from the reference position, measurement errors in mileage and direction will accumulate.
The accuracy of recognizing the current location decreases.

The above measurement error includes an error in measuring the vehicle's distance traveled by the odometer and an error in measuring the vehicle's running direction by the geomagnetic sensor. due to measurement error. The measurement error of this driving direction is caused by the error due to the declination angle (i.e., the geomagnetic sensor is located at a point north (different from true north on the map).
This is largely due to the error caused by indicating magnetic north (magnetic north).

Furthermore, the geomagnetic sensor has the property of being magnetized by disturbance, and the traveling direction detected in such a magnetized state has low reliability as data for recognizing the current position of the vehicle.

Therefore, in order to maintain high recognition accuracy of the current position of the vehicle, it is necessary to correct the declination or @magnetism, that is, correct the azimuth detected by the geomagnetic sensor, at an appropriate time. However, it is extremely troublesome and difficult for a user such as a driver to perform such correction.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a navigation device for a vehicle that can automatically correct the orientation detected by a geomagnetic sensor.

(Means for Solving the Problems) A navigation device for a car according to the present invention is configured to achieve the above object by using information regarding the driving direction that can be obtained while the vehicle is running. As the information regarding the driving direction, a signal sent from a sign post indicating the direction of the road on which the vehicle is traveling is used. That is, as shown in Figure 1,
A direction detecting means (a) for detecting the direction in which a vehicle is traveling by using earth's magnetism, a receiving means (b) for receiving a signal transmitted from a sign post to inform the direction of the road on which the vehicle is traveling, and this receiving means ( 1) Correction means (C) for correcting the direction detected by the recorded direction detection means (a) based on the direction obtained from the signal received in step 1) .

The above-mentioned "sign post" is a type of signal membrane that is installed at important points on the road and sends a signal indicating information about the path situation to vehicles traveling on the road adjacent to the sign post. The signals include at least a signal indicating the direction of the road adjacent to the sign post.

(Function) With the above configuration, when a vehicle is running, the direction detection means detects the direction of the vehicle using geomagnetism, and when the vehicle approaches a sign post, the receiving means detects the direction of the sign post. A signal that informs the direction of the road on which the vehicle is traveling is received, and based on the direction obtained from this received signal, the correction means corrects the direction detected by the direction detection means.

(Effects of the Invention) As described above, according to the present invention, since the direction detected by the geomagnetic sensor is automatically corrected, the running direction can be easily and accurately recognized, and thus the vehicle using the geomagnetic sensor can be easily and accurately recognized. The recognition accuracy in recognizing the current position of the navigation device can be improved, and the marketability of the navigation device can be improved.

(Examples) Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is an overall configuration diagram showing an embodiment of an automobile navigation device according to the present invention.

The navigation device is composed of a geomagnetic sensor 1 as a direction detecting means, a mileage measuring device 2, a memory device @3, a receiver 14 as a receiving means, a control circuit 5 as a correction means, and a display 6. .

The geomagnetic sensor 1 detects geomagnetism and outputs a signal indicating the vehicle's running direction obtained thereby to the control circuit 5.
The mileage measuring device 2 measures the distance traveled by the vehicle from a predetermined reference position by detecting the number of rotations of the tires, etc.
A signal indicating the distance traveled is output to the control circuit 5.

The storage W13 is made up of a CD-ROM 1 magnetic tape, etc., and stores therein maps and the like showing contents necessary for traveling guidance of the vehicle, such as roads and buildings.

The receiver 4 is configured to receive a signal transmitted from a sign post placed at a key point on the road, informing the direction of the road adjacent to the sign post, and output this signal to the control circuit 5. It has become.

The crime prevention circuit 5 is composed of a microcomputer equipped with an arithmetic circuit 7 and a memory circuit 8 connected thereto.
, the mileage measuring device 2, the storage device 3, the receiver 8114, and the display device 6, respectively. and control circuit 5
In the arithmetic circuit 7 and memory circuit 8, the current position of the vehicle is determined and stored based on the azimuth signal input from the geomagnetic sensor 1 and the mileage signal input from the mileage measuring device 2. In the i#JwJ circuit 5, the map around the current position recognized as described above is retrieved from the memory @ storage 3 and is configured on a CRT or the like together with the recognized current position of the vehicle and its travel trajectory. An operation is performed to display the information on the screen of the display device 6.

FIG. 3 is a block diagram showing the configuration of the geomagnetic sensor 1.

The geomagnetic sensor 1 includes a detection coil 11 that separates and detects geomagnetism into components in two orthogonal directions. The detection coil 11 includes a ring-shaped magnetic core 11a made of laminated permalloy thin plates, an excitation coil 11b wound around the entire circumference of the magnetic core 11a with its cross-sectional centerline as the coil centerline, and a magnetic core 11a drawn by the excitation coil 11b. An X-axis coil 11x that detects the X-axis direction (vehicle width direction) component of earth's magnetism is wound around the outside of the magnetic core 11a along one diameter of the circle in the longitudinal direction of the vehicle body, and - It consists of a y-axis coil 11y that detects the component of the earth's magnetism in the y-axis direction (vehicle body longitudinal direction), which is wound around the outside of the magnetic core 11a along the diameter in the vehicle width direction perpendicular to the diameter. The geomagnetic sensor 1 also includes an excitation oscillator 12. This excitation oscillation! 8 of the detection coil 11 by the signal of frequency f given from g12.
-1-1 characteristics are saturated. B- of the detection coil 11
When the H characteristic is saturated, an alternating current signal is generated by electromagnetic induction in the X-axis coil 11x and the y-axis coil 1iyt in response to an external magnetic field HO (horizontal component of earth's magnetism). The geomagnetic sensor 1 further includes frequency multiplier filter circuits 13x and 13y that filter these outputs, AC amplifiers 14x and 14y that amplify the output voltages, and doubles the frequency output by the excitation oscillator 12. Frequency multiplier 1
5, a phase shifter 16, and a frequency 2 through this phase shifter 16.
f phase signal is input, and the AC amplifiers 14x and 14y
phase detectors 17x, 17y that output DC signals corresponding to the azimuth by phase-detecting the outputs of
It is equipped with Output signals X and Y from the DC amplifiers 18x and 18y are input to the control circuit 5.

48 and 4b are diagrams showing a method of detecting geomagnetism by the geomagnetic sensor 1. FIG.

As shown in Fig. 4a, when the direction of the horizontal component Ha of the earth's magnetism is inclined by θ with respect to the X-axis coil 11x, the 4b
As shown in the figure, if the magnitude of Ho is kl-1o, the components of l-10 in the X-axis direction and y-axis direction are k
HO3inθ, kl-1a cos O, and these x, y are applied to the X-axis coil 11x and the y-axis coil 11y.
Currents corresponding to the components in each axis direction flow, thereby outputting signals X and Y indicating the horizontal component Ho of the earth's magnetism as components in two directions. In this case, the X-axis coil 1
1x is provided to extend in the longitudinal direction of the vehicle body, so the inclination θ indicates the direction of the horizontal component HO of the earth's magnetism, that is, the azimuth angle of the vehicle westward with respect to magnetic north.

The azimuth angle θ is calculated from the output signals X and Y by the arithmetic expression θ=jan(Y/X) stored in the storage circuit 8 in the peak output circuit 7 of the control circuit 5. However, The vehicle driving direction obtained in this way is based on magnetic north, so it deviates from the true north on the map by the declination.Also, due to disturbances such as external abnormal magnetic fields, the vehicle body When Wl (that is, @magnetism to the geomagnetic sensor 1) occurs, the average value XO of each of the above output signals X and Y occurs.

YO does not become zero, so one litharge circle drawn by the Ryokawa power signals X and Y is offset from the origin of the x-y coordinates. Therefore, the performance formula θ=tar+−IY/X
The azimuth angle θ screened by this method also has insufficient reliability as data.

Therefore, in this embodiment, the azimuth angle θ is automatically corrected by using the azimuth signal received by the receiver 4 and input to the control circuit 5, that is, the signal informing the azimuth of the road on which the vehicle is traveling. It is supposed to be done.

FIG. 5 and FIGS. 6a and 6b are diagrams showing an example of a method for correcting the azimuth angle θ.

As shown in Figure 5, passage A is slightly inclined from the north-south direction.
A vehicle C traveling straight ahead is equipped with the geomagnetic sensor 1 described above, and the geomagnetic sensor 1 detects the azimuth θ of the vehicle C, which includes the influence of the declination angle. When vehicle C approaches sign post SP1 installed adjacent to road A, this sign post SPx
A signal informing the direction of road A is received from 11.
received by 4. Then, in the control circuit 5, the azimuth angle θ- of the road A is highlighted. From this azimuth angle θ- and the above-mentioned azimuth angle θ, the deflection angle Δθ is determined by Δθ=θ−θ′. Thereafter, the azimuth angle θ detected by the geomagnetic sensor 1 is converted into an x''-y-coordinate rotated by Δθ from the x-y coordinate shown in FIG. 4b, as shown in FIG. 6a, and drawn. The azimuth angle θ' is determined based on the serge circle, and the declination angle is thereby corrected.

If the body of vehicle C is not magnetized, the correct running direction can be recognized by the above declination correction, but if the body is magnetized, it is necessary to further remove the influence of this. There is.

Therefore, as shown in FIG. 5, after receiving the signal from the sign post SP1, when receiving the signal from the next sign post SP2, the magnetization is corrected. That is, when the vehicle C passes the sign post SPs, turns left at the intersection J, enters the path B that is slightly inclined from the east-west direction, and runs straight on this fiNB, at this time, the control circuit 5 detects the signal detected by the geomagnetic sensor 1. The azimuth angle θ is the declination corrected azimuth angle! ' is used as a sieve. Then, when vehicle C arrived in front of sign post SPz,
A signal that informs the direction of the road B transmitted from the sign post SP2 is received by the receiver f14, and based on this received signal, the control circuit 5 determines the direction of the road B as 01''.
is used sparingly. When the li body is magnetized, the beam surge circle is in an offset state, so the azimuth angle θ1− and the azimuth angle 01″ do not match. Therefore, in the control circuit 5, as shown in FIG. 6b, , an operation is performed to offset or move the coordinate origin to the center of the surge circle. That is, the origin of the x-y coordinate is moved in the direction of the azimuth θ-, and the azimuth θ1- and the azimuth 61" are sharpened. Move it to the point where it intersects on the circle, and from x--y=coordinate x
#V Coordinate conversion to LJ coordinates will be performed. This corrects the magnetization of the vehicle body.

As described above, the declination correction and magnetization correction are completed, and henceforth, the accurate running direction of the vehicle C is recognized, and based on this, the current position of the vehicle C can be recognized with high precision. By the way, the declination angle varies depending on the position on the earth, and magnetization of the vehicle body can occur again, so even if it is possible to recognize the accurate driving direction, the recognition accuracy may deteriorate again. However, the control circuit 5
Therefore, each time the vehicle passes in front of a sign post, the above-mentioned correction operation is repeatedly and automatically performed, so that the decrease in the recognition accuracy of the driving direction is suppressed to small eyes.

FIG. 7 is a flowchart, but does not show the processing routine of the above-mentioned correction operation in the control circuit 5.

When a signal is received from a sign post while the vehicle is running (S
s), the declination angle is corrected (S2).

After that, it is determined whether a signal from the next sign post has been received within a predetermined time and within a predetermined running distance (33), and if it is determined that a signal has been received, the magnetization of the vehicle body is corrected. (S4). On the other hand, if the signal from the next sign post is not received within the predetermined time and within the predetermined mileage, there is a possibility that the declination angle will change or new magnetization of the vehicle will occur during this time. Therefore, magnetization correction is not performed. In other words, magnetization correction is possible by receiving signals from two sign posts, and in this case,
This is because if a disturbance occurs during the reception of both signals, the correction accuracy will decrease.

In addition, in the above correction operation, when the vehicle receives the signal from the sign post, it is important to drive straight on the road in order to improve the correction accuracy. The best correction accuracy is obtained when signals from each sign post are received while driving on a road extending in the same direction, and magnetization is achieved when signals from each sign post are received while driving on a road extending in the same direction. Correction becomes impossible. However, since the above correction operation is repeated every time the vehicle passes in front of a sign post, it is possible to realize accurate orientation recognition in a short period of time.

As described in detail above, according to this embodiment, the driving direction of the vehicle detected by the geomagnetic sensor 1 is automatically corrected by the control circuit 5, so that accurate direction can be determined without bothering the driver or the like. This makes it possible to perform recognition, thereby making it possible to improve the accuracy of recognizing the current position of the vehicle.

In this embodiment, a method of automatically correcting the traveling direction has been described, but it goes without saying that a method of manually correcting the direction may also be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is an overall configuration diagram showing an example of an automobile navigation device according to the present invention, FIG. 3 is a block diagram showing the configuration of a geomagnetic sensor of the device, and FIG. 4a Figure 4b is an explanatory diagram showing the action of the geomagnetic sensor, Figure 5 is an explanatory diagram of direction detection by the geomagnetic sensor and signpost glass by the receiver while the vehicle is running, and Figure 7 is a flowchart showing the processing routine in the control circuit. be. a(1)...Geomagnetic sensor b(4)...Receiving means C(5)...Correction means Fig. 1 Fig. 2 Fig. 3 Fig. 40 Fig. 4b Fig. 6 Fig. °°Fig. yl+

Claims (1)

[Claims] A bearing detecting means for detecting the driving direction of a vehicle using geomagnetism, a receiving means for receiving a signal transmitted from a sign post to inform the direction of the road on which the vehicle is traveling, and a signal obtained from the signal received by the receiving means. a correction means for correcting the direction detected by the direction detection means based on the direction determined by the direction detection means.