JPS62255814A - Correcting method for vehicle azimuth error - Google Patents

Abstract

PURPOSE:To execute navigation with high accuracy by operating a prescribed expression by using an output voltage of an earth magnetism sensor, discriminating it to be an azimuth error caused by magnetization of a car body, when said voltage exceeds a prescribed value, issuing an alarm, calculating a new offset by magnetization, and calculating an exact vehicle azimuth. CONSTITUTION:A magnetic field by magnetization of a vehicle is added vectorially to output voltages Vx, Vy of earth magnetism sensors placed orthogonal to each other on the vehicle. When the vehicle rotates by 360 deg., Vx and Vy draw a circular locus, and in the Vx and Vy coordinate system, the center of a circle exists at offsets vxn, vyn and a radius KB of the circle is proportional to the magnitude of the horizontal component of the earth magnetism B. Even if a vehicle azimuth is varied, if magnetization M is constant, the radius KB is constant. When the magnetization is varied, the offset moves, and a circle C also moves. In this state, from the circular locus after one rotation of the vehicle, the offsets vxn, vyn are calculated and (Vx-vxn)<2>+(Vy-vyn)<2> is calculated at a prescribed timing. When it exceeds the square of the radius of the circle C, an alarm is issued, and after they have been updated to new offsets vxn+1, vyn+1, an exact azimuth theta is calculated. According to this constitution, navigation can be executed with high accuracy.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a navigation system for a vehicle, and more specifically, a system that detects an error in orientation due to magnetization of a vehicle body, issues a warning, and performs correction. This invention relates to a vehicle direction error correction method.

(Prior Art) Generally, in a vehicle navigation system, the traveling direction of the vehicle is expressed as an angle θ with respect to the horizontal component of the earth's magnetic field (geomagnetic field).

FIG. 3 shows a geomagnetic sensor mounted on a vehicle for detecting vehicle direction. 10 is a magnetic core made of permalloy, for example, and an excitation film 12 is wound around this. In addition, output windings X and Y, which are orthogonal to each other, are also provided as shown in the figure.
Output voltages VX and VY are taken out from the respective output terminals.

Such a geomagnetic sensor is attached to the roof of a vehicle body, etc., as shown in FIG. And the horizontal component of geomagnetism B
When interlinked at an angle of θ as shown in the figure, the output voltage from the geomagnetic sensor is V x + V y expressed by the following formula.
is obtained.

Vx=KBcosθ ... between songs (I) V
y=KBsinθ Song...Song interval (2) Here, K: Coefficient determined by the output winding. Therefore, from the above equations (1) and (2), the angle θ of the traveling direction P of the vehicle can be found by the following equation.

θ=tan (Vy/Vx) ==(3) Also, (
Equations 1) and (2) can be transformed as follows.

Vx +Vy = (KB)2 ・・・・・・・・・
(4) This represents a circle centered on the origin O of the VX, Vy coordinates and with a radius KB. That is, when the vehicle turns 380 degrees, the locus drawn by V xlV y becomes a circle Co as shown by the solid line in FIG.

(Problem to be solved by the invention) By the way, the principles of equations (1) to (4) above hold true when the magnetic field acting on the geomagnetic sensor is only the geomagnetism, but in reality, it is true that the magnetic field acting on the geomagnetic sensor is When the car body passes through a place that generates a strong magnetic field, it becomes magnetized, and the magnetic field generated by this overlaps with the earth's magnetism vectorwise.For example, as shown in Figure 4, when the magnetic field due to magnetization at angle α and size G is superimposed, The corresponding bias or offset y x1, v
yl is generated in the output windings X and Y of the geomagnetic sensor, respectively, and the output circle in FIG. 5 moves to a circle C1 as shown by the dotted line.

In such a case, using equation (3) will cause an error, so
The following formula may be used.

θ: tan ((Vy − v xi) / (Vx −
v yl) - (5) In this way, the influence of magnetization of the vehicle body can be corrected using equation (5), but as a premise it is necessary to know that it has been magnetized. However, magnetization of the car body occurs in various places and factors other than train crossings, and it changes easily, so it is impossible for the driver himself to know while driving, so the direction error remains uncorrected. Driving is performed, and the navigation becomes erroneous.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide a method for correcting vehicle heading errors that detects errors in heading due to magnetization of a vehicle body, issues a warning, and performs correction. shall be.

(Means for Solving the Problems) The method of the present invention for achieving the above object includes mounting a geomagnetic sensor on a vehicle, and generating electricity from one output winding of the geomagnetic sensor and the other output winding perpendicular thereto. In a vehicle direction detection method that determines the traveling direction of the vehicle based on the output voltage V x + V y that Offset of the output voltages Vx and Vy due to magnetization) vxn+v
(b) Calculating the value of the following formula at a predetermined timing, (
Vx −vxn)” + (Vy −vyn)”(c)
issuing a warning when the value of the above formula exceeds a predetermined value; (d) when the vehicle turns in response to the warning, the new Offsera obtained in step (a)) VXn+IIVyn;
The method is characterized in that it includes the following steps: updating the previous offset v xn, v yn to +1.

(Function) The horizontal component of the earth's magnetic field (geomagnetic field) and the magnetic field due to vehicle body magnetization act on the geomagnetic sensor by vectorial superposition.

When the vehicle turns 360 degrees, the horizontal force of the geomagnetism rotates 360 degrees relative to the vehicle, and the output voltages Vx and Vy of the geomagnetic sensor draw a circular locus. Vx, V
In the y coordinate, the coordinates of the center of this circle (output circle) correspond to offsets v xn and v yn due to magnetization of the vehicle body, and the radius of the circle is proportional to the magnitude of the horizontal component of the earth's magnetism.

Therefore, if the vehicle body magnetization is constant even if the vehicle direction changes, the coordinate positions of the output voltages Vx and Vy will be on the output circle, and the value of the equation in step (b) will be a constant value (radius). is maintained, does not exceed a predetermined value, and no warning is issued.

However, when the car body magnetization changes, the offset moves,
The outgoing yen will also move accordingly. Then step (b)
The value of the expression changes and exceeds a predetermined value, and a warning is issued.

In response to this warning, step (d) causes the vehicle to e.g.
When the circumference is completed, new offsets V xn+1 and V 3jn+1 are calculated by a well-known one-round correction method to correct errors caused by the vehicle body magnetization.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1, 2, and 5.

FIG. 2 shows the configuration of a vehicle orientation detection device that implements the method of the present invention. The magnetic fan 10, excitation coil 12, and output windings X and Y are the same as those shown in FIG.

Output voltage Vx taken out from output windings X and Y.

Vy is each converted into a digital value by an analog-to-digital (A/D) converter 14, 18 and supplied to the microcomputer 18. Furthermore, the microcomputer 18 includes a cumulative distance meter 20 consisting of a tachometer, etc.
A vehicle speed pulse PC is inputted as an interrupt pulse every fixed travel distance.

The warning indicator 22 is made of, for example, a lamp, and is provided in a display section of the driver's seat.

FIG. 1 shows a microcomputer 18 according to this embodiment.
The processing operation program is shown below.

An interrupt is generated by the vehicle speed pulse PC from the cumulative distance meter 20, and this program is executed. First, output windings X, Y
The output voltage V x + V y is taken in and the value of the following equation is calculated (step ■).

(Vx −vxn-1”+ (Vy −vyn-1)’
= r n”...-(G) Here, V xn-1, V
yn-1 is the previous offset, that is, the offset obtained in step ■ during the previous execution of this program, and in FIG. 5, the coordinates (v xn-1° vyn -1). Therefore, if the vehicle body was not magnetized last time, the previous output circle is the circle CO shown by the solid line, and the offset v xot
v yo are each zero (origin).

Next, the value rn obtained by the above formula is differenced from a constant value (KB)2 corresponding to the radius of the output circle in FIG. It is checked whether it exceeds (step ■).

As a result of this inspection, if the predetermined value F is not exceeded, it is determined that the output circle has not substantially moved, that is, there is no azimuth error due to the vehicle body magnetization, and in step 2, the offset V Xn-L V yn After calculating the vehicle orientation angle θ from the following equation using -1, the interrupt program exits.

θ=tan((Vy-vyl)/(Vx-vxl)) Therefore, in this case, the previous offset vxn-1°v
yn-1 is not updated and is maintained as is.

However, in the inspection of step ■, l r n” − (KB)
``If l exceeds the predetermined value F, it is determined that the output circle is moving, that is, an error has occurred in the vehicle direction due to the vehicle body magnetization, and a warning is issued (step ■). This is done by causing the warning display 22 to provide a predetermined display in response to an instruction signal from the microcomputer 18.

If this warning is issued, the driver can simply turn the car once (360°) at an appropriate location to correct the heading error. In this case, the horizontal component B of the earth's magnetism rotates once (360°) relative to the vehicle, and in FIG. 5, the output voltage V Draw a locus of a circle centered on (.For example, if the offset due to vehicle body magnetization is (vx1,
vyl), a dotted circle CI is drawn.

The offset (vxn.

v yn) is determined and the previous offset (v xn
-1, vyn-1) to its offset (vxn, v
yn) is updated (steps ■, ■, ■).

Then, the correct orientation θ is calculated using the new offset (vxn+vyn) (step ■), and the interrupt program is extracted.

Once the offset has been updated as described above, when the next vehicle speed pulse PC is input, the value of the following equation is calculated in step (2).

(Vx −vxn)”+ (Vy −vyn)”=
r n+12-46) Then, in step ■, the absolute value l
It is checked whether r n+12- (KB) 21 exceeds a predetermined value F, and the same processing operation as described above is performed according to the test result.

In FIG. 5, the dashed-dotted circle C2 is the output circle when the offset moves to (Vx2. vy2) due to new magnetization of the vehicle body. For example, the output voltage Vx taken in from the output windings X and Y , Vy are at the coordinate position P2, the value of the following equation is calculated in step (3).

(Vx - vxl) + (Vy - vyl)' = r
22-(11i) Then, in step ■, I r
22- (KB) 21 > F, and a warning is displayed in step (■). Then, when the vehicle turns once, a new offset, that is, the coordinate position of the center of circle C2 (Vx2. vy2) is calculated by the one-round correction method, and the previous offset (vxl) is calculated.

v yl) is updated to its offset (Vx2. vy2) (Steps ■, ■, ■), and in Step ■, an accurate azimuth angle θ is calculated using the following equation.

θ=jan ((Vy-vy2)/(Vx-Vx2
)) The -period correction method is to calculate the local maximum values VxM, V of the output voltages Vx, Vy, respectively, in the circle (output circle) drawn by the output voltages Vx, Vy when the vehicle turns once.
This is a method of finding yM and minimum values V xff1, V ym and calculating the offset (vxn+vyn) from the following equation.

vxn= (VxM+Vxi+) / 2vyn=
(VyM+Vym) / 2 Although one embodiment of the present invention has been described above, various modifications and changes are possible within the scope of the technical idea of the present invention. For example, in step ■ l r n
Instead of 2-(KB)''I, it may be checked whether lrn-(KB)I exceeds a predetermined value f.

Furthermore, methods other than the one-round correction method described above can also be used to calculate the offset.

(Effects of the Invention) As described above, according to the present invention, a predetermined formula is calculated using the output voltage of the geomagnetic sensor, and if the value exceeds a predetermined value, the error in orientation due to magnetization of the vehicle body is detected. This system detects that a magnetic field is occurring and issues a prompt and appropriate warning, and also calculates the new offset caused by the magnetization to determine the accurate vehicle direction, resulting in a highly accurate navigation system. Ru.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a program for processing operations of a microcomputer according to an embodiment of the present invention; FIG. 2 is a block diagram showing the configuration of a vehicle direction detection device that implements the method of the present invention; FIG. is a perspective view showing the configuration of the geomagnetic sensor, FIG. 4 is a schematic plan view showing how a magnetic field acts on the geomagnetic sensor attached to a vehicle, and FIG. 5 is an output circle drawn by the output voltage of the geomagnetic sensor. FIG. 3 is a diagram showing the effect of the embodiment. 10... Magnetic core, X, Y... Output winding, 1
2...Excitation filter, 14.16...A/D
Converter, 18...Microcomputer, 20.
...Total distance meter, 22...Warning indicator. Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A geomagnetic sensor is mounted on a vehicle, and the traveling direction of the vehicle is determined based on output voltages Vx and Vy generated from one output winding of the geomagnetic sensor and the other output winding orthogonal thereto, respectively. (a) An offset vxn of the output voltages Vx, Vy due to magnetization of the vehicle is determined based on the locus of the output voltages Vx, Vy obtained when the vehicle turns approximately once;
, vyn; (b) Calculating the value of the following formula at a predetermined timing; (
Vx-vxn)^2+(Vy-vyn)^2 (c) issuing a warning when the value of the above formula exceeds a predetermined value; (d) when the vehicle turns in response to the warning; The new offset vxn+ obtained in step (a) above
1. Updating the previous offset vxn, vyn to 1, vyn+1.