JPS59176621A - Direction detector for vehicle - Google Patents

Abstract

PURPOSE:To correct the direction of a vehicle accurately even during fast turning, etc., by making the time constant of a smoothing circuit which generates a DC voltage corresponding to the direction different during normal direction display based upon terrestrial magnetism and during correction corresponding to the magnetism of the vehicle. CONSTITUTION:When the vehicle is magnetized, a correction switch CS is put in operation to apply a reverse current for correction to secondary coils 1X and 1Y of a magnetic sensor 1 which detects a terrestrial magnetic component by an A/D converter and voltage-current converters 10 and 12, and 11 and 13. At the same time, analog switches 16 and 17 are controlled through a microcomputer 8 according to the state of the switch CS, and time constant circuits of the smoothing circuit which converts a direction voltage by the terrestrial magnetism detection into a DC voltage are switched from circuits 5 and 6 having large time constants to circuits 14 and 15 having small time constants and reset to the circuits 5 and 6 after the correction is completed. Therefore, the direction on the normal display is obtained without any flicker and the accurately corrected direction at the time of the correction is displayed even during fast turning.

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.

When a direction detection device having a geomagnetic sensor is installed in a vehicle, the magnetization of the vehicle itself (hereinafter referred to as vehicle body magnetization) K
It is well known that it is affected by magnetic fields caused by Therefore, in order to put this type of orientation detection device into practical use, means for correcting the vehicle body magnetization is required. Various types of correction means are available, but it is desirable that the correction can be completed naturally without the driver having 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 and detects geomagnetism, and 2 is an excitation coil (not shown) of the magnetic sensor 1.
3 is an excitation circuit that is connected to the K and excites the magnetic core IC; 3 is an amplifier circuit that is connected to a secondary coil IX wound around the outer periphery of the magnetic core 1c; and 4 is an amplifier circuit that amplifies the geomagnetic signal generated in the secondary coil IX; connected to a secondary coil IY wound around the outer periphery of the magnetic core IC perpendicularly to the secondary coil LX;
An amplifier circuit for amplifying the geomagnetic signal generated in the secondary coil IY; 5 and 6 are smoothing circuits for smoothing the output signals of the amplifier circuits 3 and 4 and absorbing instantaneous disturbance magnetism; 7 is a smoothing circuit for the smoothing circuit 5, A/D converts 6 analog signals into digital signals
A converter 8 receives the output signal of the A/D converter 7 and converts it into an azimuth signal, and also receives a signal from a correction switch C8 that commands the start of correction, and then performs correction processing. Micro: 17 Huta; 9 c. The microcomputer 8 (
7) Display device that receives the azimuth output signal and displays the azimuth, 1o
.

11 is a D/A converter that converts the correction digital output signal of the microcomputer 8 into an analog signal; 1;
2,13LtThe D/A 1m61 (This is a voltage-current converter that converts the output signal voltage of 1,11 into a correction current.

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

Let eX and eY be the signal voltages generated in the secondary coils IX and IY of the magnetic sensor 1, respectively, and these can be obtained by the following equations.

eX=KHcasθ (1)ey
= KH-θ (2) where K is a constant, ■ is the horizontal component of the earth's magnetism, and θ is the angle formed between the direction of the earth's magnetism and the secondary coil IX. From the above (1) and (2), ez + ey is determined, the angle θ is determined, and the traveling direction of the vehicle is determined. To output No. 1B of magnetic sensor 1 and ey
is amplified by amplifier circuits 3 and 4, and its output signal is smoothed by smoothing circuits 5 and 6, which serve to remove, for example, disturbance magnetism generated by electrical loads and disturbance magnetism entering 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 and applied to the microcomputer 8. The microcomputer 8 receives the digital signal corresponding to the output signal ez rey, calculates θ from the above equation fi+, +21, and creates a direction signal 8a. The display 9 receives this azimuth signal 8a and displays the azimuth.

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 number of output signals of secondary coils IX and IY.

It is a Lissajous diagram of eY. In other words, when the vehicle body magnetization is completely corrected, the torsage diagram 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 R7 with the center at point P is formed, and the magnitude of the influence of the vehicle body magnetization can be expressed by a vector OP. Therefore, for example, in the north direction, an error occurs by the angle θ shown in the figure.

Now, when the driver operates the correction switch C8 to perform correction, the microcomputer 8 executes a program to detect the Y-axis and the intercept of the Y-axis shown in FIG. When the vehicle makes one turn, the values of the four intercepts A, B, C, and D with respect to X@I and Y@I are detected.

Next, once the four intercepts are determined, the central velocity coordinates (vxo, vY) of the center point P of the circle are determined from the following equation.

This makes it possible to eliminate the influence of vehicle body magnetization. In order to generate this backward vector PO, a D/A converter 10,
A correction digital signal corresponding to (-VXO"YO) is applied to 11 from the microcomputer 8, converted into an analog signal, and further converted into a final correction current by the Vct pressure-current converter 12.13, and the above-mentioned Secondary coil IX of magnetic sensor I.

Supplied by IYK. This correction current generates a magnetic field within 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 slope diagram in Figure 2 even when turning at a certain high speed, the time constants of the smoothing circuits 5 and 6 shown in Figure 1 are reduced. Improves responsiveness. However, if this responsiveness is good,
During normal driving, a problem occurs in which the display 9Q display flickers due to the influence of magnetic disturbances (for example, from iron bridges, expressways, adjacent vehicles, etc.). In order to eliminate this problem, it is necessary to considerably increase the time constant of the smoothing circuit 5.6 to reduce the responsiveness. In this case, the geomagnetic field signal ez + e
The y glue serge diagram is shown in Figure 3. In the same figure, the circle R
is a slope diagram when turning at a very slow speed, and conversely, figure R' shown by a dotted line is a slope diagram when turning at a high speed and at an irregular turning speed.

Therefore, the intercept detected during correction is normal i,B.

C and D become A', B', C', and D'.

In other words, if the smoothing time constant of the analog detection potential during correction is set large, the delay will be large and errors will occur, 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. There was a problem.

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 azimuth detection device capable of accurately correcting the traveling direction of the vehicle even when the vehicle is turning at high speed. It is an object.

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 which 14.15 is an amplifier 3 similar to the smoothing circuits 5 and 6 described above.
, 4 is shown, and the smoothing time constant is sufficiently larger than that of the smoothing circuits 5 and 6 described above. Reference numerals 16 and 17 indicate analog switches that switch the output signals of the smoothing circuits 5, 14 or 6, 15 in response to the output signals 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 described.

Now, when the correction switch C8 is activated and the microcomputer 8 detects the start of this correction, the analog switch C8 is activated.
6 and 17 select the output signals of the smoothing circuits 5 and 6, the micro combi coater 8 switches the analog switches 16 .
17 continues to supply the output signal 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 Lissajous 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, a signal is supplied from the microcomputer 8 to the analog switches 16 and 17 so that the output signals of the smoothing circuits 14 and 15 are selected. Therefore, in the normal display after correction, the smoothing circuit 1
Since the time constant of 4.15 is sufficiently large, flickering of the display due to magnetic disturbance is eliminated.

As explained above, according to the present invention, in a device comprising means for detecting magnetic flux density that causes a disturbance to a geomagnetism detector, and correction means for supplying current to the geomagnetism detector in order to cancel the disturbance magnetism, an analog With the configuration in which the smoothing time constant of the detected potential can be switched to a desired magnitude, the correction can be made reliably during correction, and an accurate azimuth can be displayed even during normal display, which is a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, FIGS. 2 and 3 are Lissajous diagrams explaining the operation of the conventional device shown in FIG. 1, and FIG. 4 is a block diagram of an embodiment of the present invention. be. 1...Magnetic sensor, 2...-excitation circuit, 3,4...
Amplifier circuit, 5, 6, 14. 15... Smoothing circuit, 7...
・A/D converter, 8.--Microcomputer, 9.
・・Display device, 10.11-・・D/A converter, 12.1
3... Voltage-current converter, 16.17... Analog switch, C8... Correction switch. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Shin Kuzuno −

Claims (1)

[Claims] There is a geomagnetism detector that detects geomagnetism by dividing it into two orthogonal components in the horizontal plane and converts it into an electrical signal corresponding to each component, and a geomagnetism detector that amplifies the electrical signal output from this geomagnetic detector and corresponds to the geomagnetism. an amplifier circuit that converts it into a voltage signal;
A smoothing circuit that smoothes the electrical signal output from this amplifier circuit, a display that receives the electrical signal output from this smoothing circuit and receives a direction signal and displays the direction, and the magnetization of the vehicle that is applied to the geomagnetic detector. In a vehicle orientation detection device equipped with correction means for detecting magnetic flux density and supplying current to the magnetic detector in order to cancel the magnetic flux density, the time constant of the smoothing circuit described above is adjusted during correction and during normal orientation display. A vehicular orientation detection device characterized by being provided with switching means for selectively changing VC.