JPH0261685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle direction detection device that detects earth's magnetic field and displays the direction of travel of a vehicle.

It is well known that when a direction detection device having a geomagnetic sensor is installed in a vehicle, it is affected by a magnetic field due to the magnetization of the vehicle itself (hereinafter referred to as vehicle body magnetization). Therefore, in order to put this type of orientation detection device into practical use, means for correcting the vehicle body magnetization is required. There are various types of correction means, but it is desirable that the correction can be completed naturally without requiring the driver to bother with the correction.

A conventional example of this device is shown in the block diagram of FIG. In the figure, 1 is a magnetic sensor mounted on a vehicle for detecting earth's magnetism, and 2 is a magnetic core 1c connected to an excitation coil (not shown) of the magnetic sensor 1.
An excitation circuit 3 is connected to the secondary coil 1X wound around the outer periphery of the magnetic core 1c, and an amplifier circuit is connected to the secondary coil 1X to amplify the geomagnetic signal generated in the secondary coil 1X. 4 is an amplification circuit that excites the outer periphery of the magnetic core 1c. is connected to the secondary coil 1Y wound orthogonally to the secondary coil 1X, and amplifies the geomagnetic signal generated in the secondary coil Y; 5 and 6 are the amplifier circuits 3 and 4;
7 is an A/D converter that converts the analog signals of the smoothing circuits 5 and 6 into digital signals; 8 is an A/D converter of the A/D converter 7; A correction switch that receives the output signal and converts it into a direction signal, and also commands the start of correction.
A microcomputer that performs correction processing after receiving the CS signal; 9 a display that receives the azimuth output signal from the microcomputer 8 and displays the azimuth; 1
0 and 11 are D/1 converters for converting the correction digital output signal of the microcomputer 8 into an analog signal.
A converters 12 and 13 are the D/A converters 10 and 1
Voltage that converts the output signal voltage of 1 into correction current -
It is a current converter.

In the above configuration, the operation of the conventional example will be explained.

Assuming that the signal voltages generated in the secondary coils 1X and 1Y of the magnetic sensor 1 are _eX and _eY, respectively, these can be obtained by the following equation.

_{e _} If e _X and e _Y are determined from (1) and (2) above, θ is determined, and the traveling direction of the vehicle is determined. _The output signals _e
For example, it functions to remove magnetic disturbances generated by electrical loads and disturbance magnetic fields that enter from road structures. Next, the analog signals smoothed by the smoothing circuits 5 and 6 are converted into digital signals by the A/D converter 7,
The signal is applied to the microcomputer 8. The microcomputer 8 receives the digital signals corresponding to the output signals _e.sub.X and _e.sub.Y , calculates .theta. using the above-mentioned equations (1) and (2), and generates a direction signal 8a. The display 9 receives this direction signal 8a and displays the direction.

By the way, since the vehicle body is magnetized as described above, if the earth's magnetic field is disturbed, the direction display will not be normal.

Figure 2 shows the output signals e _X and e _Y of the secondary coils 1X and 1Y.
This is a resurge diagram. That is, the Lissage diagram when the vehicle body magnetization is completely corrected becomes a circle centered on the origin O, like a circle S. However, if there is an influence of the vehicle body magnetization, for example, a circle R is formed with the center at point P, and the magnitude of the influence of the vehicle body magnetization can be expressed as a vector OP→. Therefore, for example, in the north direction, an error occurs by the angle θ shown in the figure.

Now, the driver turns on the correction switch to perform correction.
When the CS is activated, the microcomputer 8 executes a program to detect the intercepts of the X and Y axes shown in FIG. When the vehicle makes one turn, the values of the four intercepts A, B, C, and D with respect to the X and Y axes are detected. Next, once the four intercepts are determined, the central velocity coordinates (V _XO , V _YO ) of the center point P of the circle are determined from the following equation.

V _XO = V _C + V _D /2 (3) V _YO = V _A + V _B /2 (4) Once these velocity coordinate values V _XO and V _YO are found, find the opposite vector PO→ that should cancel the vector OP→ It is possible to eliminate the influence of vehicle body magnetization. _In order to generate this backward vector PO→, a correction digital signal corresponding to ( _-V Further voltage-
The current is converted into a final correction current by current converters 12 and 13, and is supplied to the secondary coils 1X and 1Y of the magnetic sensor 1. This correction current generates a magnetic field in the magnetic sensor 1 to create a reverse vector PO→.

However, although the correction is made by turning the vehicle, the turning speed varies depending on the driver.
Therefore, in order to reliably detect the intercepts A, B, C, and D in the Lissage diagram in Fig. 2 even when turning at a certain high speed, the time constants of the smoothing circuits 5 and 6 shown in Fig. 1 are made small. Improves responsiveness. However,
If this responsiveness is good, a problem occurs when the display on the display 9 flickers due to the influence of magnetic disturbance (for example, from a railway bridge, an expressway, an adjacent vehicle, etc.) during normal driving. In order to eliminate this problem, it is necessary to considerably increase the time constants of the smoothing circuits 5 and 6 to reduce the responsiveness. Geomagnetic output signal in this case
Figure 3 shows the Lissage diagram of e _X and e _Y. In the figure, circle R is a resurge diagram when turning at a very slow speed, and conversely, the figure R' shown by a dotted line is a resurge diagram when turning at a fast and irregular turning speed.

Therefore, the intercept detected during correction is the normal A,
B, C, and D become A', B', C', and D'. That is,
If the smoothing time constant of the analog detection potential during correction is set large, the delay will be large, causing an error, and the correction will not be performed accurately.On the other hand, if the smoothing time constant is set small, the direction display will flicker due to the influence of magnetic disturbance. It was hot.

The present invention was made in order to eliminate the drawbacks of the conventional devices as described above, and it is an object of the present invention to provide a vehicle orientation detection device that can accurately correct the traveling direction of the vehicle even when the vehicle is turning at high speed. The purpose is

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram showing an embodiment of the present invention.

In the figure, 14 and 15 are the smoothing circuits 5 and 6.
Similarly, a smoothing circuit for smoothing the output signals of the amplifiers 3 and 4 is shown, but the smoothing time constant is different from that of the above-mentioned smoothing circuits 5 and 6.
It has become sufficiently larger than that. Analog switches 16 and 17 switch the output signals of the smoothing circuits 5 and 14 or 6 and 15 in response to the output signal of the microcomputer 8, and supply the output signals to the A/D converter 7.

Based on the above configuration, the operation of an embodiment of the present invention will be explained.

Now, when the correction switch CS is activated and the microcomputer 8 detects the start of this correction, the analog switches 16 and 17 select the output signals of the smoothing circuits 5 and 6.
continues supplying output signals to the analog switches 16 and 17 until the correction is completed. Since the smoothing circuits 5 and 6 are configured so that their time constants can be set to a small value, the intercept can be reliably detected in the Lissage diagram even when the vehicle is turning at high speed, and as a result, accurate correction can be performed.

Next, when the correction is completed, the smoothing circuits 14 and 1
5 is selected from the microcomputer 8 to the analog switches 16 and 17.
A signal is supplied to Therefore, in the normal display after correction, the time constants of the smoothing circuits 14 and 15 are sufficiently large, so that display flickering due to magnetic disturbance is eliminated.

As explained above, according to the present invention, there is provided a means for detecting magnetic flux density that causes disturbance to a geomagnetic detector;
A correction means for supplying current to the geomagnetism detector to cancel out the magnetic disturbance,
With the configuration in which the smoothing time constant of the analog detection potential can be switched in magnitude, it is possible to perform the correction reliably at the time of correction, and moreover, it has the great practical effect of being able to display the accurate direction even during the normal display.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a conventional device, FIGS. 2 and 3 are resurge diagrams explaining the operation of the conventional device shown in FIG. 1, and FIG. 4 is a block configuration diagram showing an embodiment of the present invention. be. 1... Magnetic sensor, 2... Excitation circuit, 3, 4... Amplification circuit, 5, 6, 14, 15... Smoothing circuit, 7... A/
D converter, 8... Microcomputer, 9... Display, 10, 11... D/A converter, 12, 13... Voltage-current converter, 16, 17... Analog switch, CS... Correction switch. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A geomagnetism detector that detects geomagnetism by dividing it into two orthogonal components in a horizontal plane and converts it into an electrical signal corresponding to each component, and a DC voltage that amplifies the electrical signal output from this geomagnetic detector and corresponds to the geomagnetism. An amplifier circuit that converts the signal into a signal, a smoothing circuit that smoothes the electrical signal output from the amplifier circuit, a display that receives the electrical signal output from the smoothing circuit, receives a direction signal, and displays the direction, and a vehicle In a vehicle azimuth detection device comprising a correction means for detecting the magnetic flux density that a magnet gives to the geomagnetic detector and supplying current to the magnetic detector to cancel this magnetic flux density, the azimuth detection device is configured to detect the magnetic flux density that a magnet gives to the geomagnetism detector, and to supply current to the magnetic detector in order to cancel the magnetic flux density. A vehicle azimuth detecting device characterized in that a switching means for selectively changing the time constant of the smoothing circuit is provided.