JPH02194313A - Bearing indicator for vehicle - Google Patents

Abstract

PURPOSE:To detect the center coordinate position of an output circle with high accuracy by setting the initial virtual center value and radius of the output circle and performing arithmetic processing so that the initial virtual value prescribes the expression of the output circle approximated from the output value of an earth magnetism bearing sensor. CONSTITUTION:The earth magnetism bearing sensor 1 detects an earth magnetism component as two directional components which cross each other on a horizontal plane at right angles. A sensor output storage means (a) is stored with the output value of the sensor 1 successively. An initial virtual center value arithmetic means (b) calculates the initial virtual value of the center coordinate position of the output circle from plural output values which are stored in the means (a). An initial virtual radius setting means (c) sets the initial virtual value of the radius of the output circle according to the mean intensity of earth magnetism. An initial virtual radius limiting means (d) limits the initial virtual radius which is set (c) to values within the range of the actual earth magnetism. A correction quantity arithmetic means (e) calculates a correction quantity so that the initial virtual center value which is calculated (b) and the initial virtual radius which is limited (d) prescribe the expression of the output circle approximated by the output value of the sensor 1; and a correcting value correcting means (f) corrects the initial virtual value by the correction quantity of the means (e).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a geomagnetic direction sensor for use in vehicles that detects the direction from the output circle center coordinates of the sensor to the coordinates indicated by the output value of the geomagnetic direction sensor as the running direction of the vehicle. Regarding compass.

(Prior Art) As a device for detecting the running direction of a vehicle using a geomagnetic direction sensor, one disclosed in Japanese Patent Application Laid-Open No. 100812/1983 is known.

This compass has a pair of windings that are orthogonal in a horizontal position.
These windings each obtain a geomagnetic component detection voltage (output value) corresponding to the geomagnetic linkage, and when a vehicle runs around in a uniform geomagnetism, the coordinates indicated by the detection voltages of these windings are used to coordinate A circle (output circle of the geomagnetic direction sensor) is drawn on the plane -1-.

Further, during normal running of the vehicle, the direction from the center of the output circle to the coordinates indicated by the detected voltages of both windings is determined as the running direction of the vehicle.

Here, when the vehicle body is magnetized, the center coordinates of the output circle move, which causes an error in detecting the running direction.

In this case, the vehicle is traveling around, and during that time the output values of the geomagnetic direction sensor are sampled, and if only the output values of four points intersecting the X-axis and Y-axis are obtained on the sensor output circle, The center coordinates of the output circle are corrected by averaging these sampling output values.

(Problem to be Solved by the Invention) However, in the conventional device as described above, even if the magnetic field environment of the place where the correction is performed is bad, the averaging process is performed using the sampling output values of only four points. However, there was a problem in that the center coordinate position could not be obtained with high precision, and the driver was forced to make a full turn during correction.

(Object of the Invention) In view of the above problems, it is an object of the present invention to provide a vehicle orientation = 1 that allows the center coordinate position of an output circle to be obtained with high accuracy and that does not require a single round turn for correction. The eyes? ]
shall be.

(Means for Solving the Problems) In order to achieve the above object, a vehicle compass according to the present invention is constructed as shown in FIG.

This vehicle compass uses a geomagnetic azimuth sensor to detect geomagnetic components as components in 2h directions perpendicular to each other on a horizontal plane, and the direction from the center coordinate position of the output circle to the coordinate position indicated by the geomagnetic components in the two directions. The driving direction of the vehicle is determined based on the following.

In the sensor output value storage means a, output values output from the geomagnetic azimuth sensor are sequentially stored.

The initial virtual center value calculation means calculates the initial virtual value of the center coordinate position of the output circle by arithmetic averaging from the plurality of output values stored by the sensor output value storage means a.

In the initial virtual radius setting means C, an initial virtual value of the radius of the output circle is set based on the average strength of the earth's magnetism.

The initial virtual radius limiting means d limits the initial virtual radius set by the initial virtual radius setting means C to those within the range of the actual geomagnetic strength.

In the correction amount calculating means e, the initial virtual center value calculated by the initial virtual center value calculating means 1 and the initial virtual radius limited by the initial virtual radius limiting means d are approximated from the output value of the geomagnetic direction sensor 1. The amount of modification of each initial virtual value is calculated so as to define the formula of the output circle.

The virtual value correction means f corrects the initial virtual value of each correction amount calculated by the correction amount calculation means C, and converts the initial virtual value into the center coordinate position of the output circle approximated from the output value of the geomagnetic direction sensor. and converge to the radius.

(Operation) In this invention, the initial virtual center value and initial virtual radius of the output circle are set, and calculation processing is performed so that these initial virtual values define the formula of the output circle approximated from the output value of the geomagnetic direction sensor. By doing so, the center coordinate position of the output circle is corrected.

In addition, the virtual radius used in the above calculation process is
It is always used only within the range of the actual geomagnetic strength.

(Description of Embodiments) Hereinafter, preferred embodiments of the vehicle compass according to the present invention will be described based on the drawings.

FIG. 2 shows the basic configuration of a navigation system to which the present invention is applied. In the figure, the geomagnetic direction sensor separates the geomagnetic component into components in two orthogonal directions on a horizontal plane, and the geomagnetic component in each direction is It is output as an electrical signal indicating.

2 is an output processing circuit that detects the output of the geomagnetic azimuth sensor 1 and converts it into a digital signal; 3 is an azimuth calculating section that calculates the azimuth from the output signal of the geomagnetic azimuth sensor 1; 4 is a characteristic part of the present invention This is a vehicle body magnetization correction circuit that is mainly composed of a microcomputer.

Next, FIG. 3 shows the geomagnetic direction sensor 1.
The annular permalloy core 6 has windings 7X orthogonal to each other.
, 7Y are provided.

A winding 8 is wound around the permalloy core 6, and the winding 8 is energized by an excitation power source 9 until just before the permalloy core 6 is saturated, as shown in FIG.

When the geomagnetic direction sensor 1 described above is placed in a non-magnetic field,
Magnetic flux Φ1 passing through portion S11 and portion S2 of permalloy core 6, respectively. Φ2 has the same size and opposite direction as shown in FIG.

Therefore, the magnetic flux interlinking with the winding 7X becomes zero, and the detected voltage vy of the winding 7Y also becomes zero.

Furthermore, when geomagnetic He is applied to this geomagnetic direction sensor at right angles to the winding 7X as shown in FIG. given, magnetic flux Φ
1. Φ2 becomes asymmetrical as shown in FIG.

Therefore, the detection voltage Vx having the waveform shown in FIG. 7 is obtained in the winding 7X.

Furthermore, since the earth's magnetic field He is parallel to the winding 7Y, the earth's magnetic field He does not intersect with the winding 7Y, and therefore no voltage y is generated in the winding 7Y.

This geomagnetic direction sensor is mounted on a vehicle in a horizontal position as shown in FIG.
X, 7Y have detection voltages Vx, Vy according to the earth's magnetic field He.
(output value) are obtained respectively.

These detection voltages Vx and Vy are calculated by the following equation (1), where K is the winding constant and B is the horizontal component of the earth's magnetic field He.
2) are shown in the following equations.

V x = K B cosθ (
1) Vy=KBsinθ (2) Therefore, if the width direction of the vehicle is used as a reference as shown in FIG. 8, the angle θ indicating the running direction is θ=jan' (
Vx/Vy) (3).

As understood from Equations (1) and (2) in Section 2, when the vehicle travels around in the uniform geomagnetic He, the detected voltage Vx of the windings 7X and 7Y.

A circle (output circle of the geomagnetic azimuth sensor) is drawn on the X-Y plane coordinates as shown in FIG. 9 by the coordinates indicated by Vy, and the output circle is expressed by the following equation.

Vx2+Vy” = (KB) 2 (4)
In this way, since the coordinates determined by the detection voltages Vx and Vy of the windings 7X and 7Y exist on the output circle, the direction detecting section 3 determines that the direction from the center O of the output circle to the coordinate point (output point) is the direction of the vehicle. Detected as the driving direction.

Here, the body of the vehicle is magnetized, and as shown in FIG. 10, for example, as shown in FIG.
When X and 7Y are interlinked, the output circle moves from the broken line position to the solid line position as shown in FIG.

As a result, an error occurs in the detection of the running direction of the vehicle performed by the direction detecting section 3.

Hereinafter, the processing procedure of the vehicle body magnetization correction circuit 4, which is a characteristic part of this embodiment, will be described in detail with reference to the flowchart shown in FIG.

When the program is started, a reference collection constant N for collecting a predetermined amount of data from the geomagnetic azimuth sensor 1, and convergence determination constants εX and εy when correcting the center coordinate position of the output circle, which will be described later.

εr is set (step 100).

In this way, when a certain constant necessary for vehicle body magnetization correction is set, the collected data counter i of the geomagnetic azimuth sensor 1 is reset to 0 (step 102), and from then on, the output values of the geomagnetic azimuth sensor 1 are stored sequentially. (Step 104).

Therefore, in step 106, the first output voltages Vx and Vy output by the geomagnetic direction sensor 1 are equal to the output value (X (
i), Y(i)) and stored.

When a predetermined number of output values of the geomagnetic azimuth sensor 1 are collected as described in L, it is then determined whether the output values exceed a constant N (step 108). The output value collected here is N
If it does not exceed N (NO in step 108), collect more data, and if it exceeds N (step 108)
YES), the process proceeds to step 110, and based on the collected data, first, the center coordinate position of the output circle is determined by the following equation to an initial virtual value (this is referred to as the initial virtual center value) (Xo
, yo:l.

Xo−ΣX (1()/i
(5) −1 Yo−ΣY (k)/i (6)
-J On the other hand, once the initial virtual center value is obtained in this way, next is the initial virtual value of the radius of the output circle (this is called the initial virtual radius).
Ro is set (step 112).

In this example, the initial virtual radius Ro is set to a size equivalent to 300 mG (milligauss), which is the average geomagnetic strength.

In this way, when the initial virtual center value (X, o, Yo) and initial virtual radius R6 are obtained, the center coordinate value of the output circle is corrected using the calculation method described below using these initial virtual values. However, in this correction process, the initial virtual radius Ro of the above two initial virtual values is
It is converted and used as shown in the following equation (step 114).

Ro=Rm+kXsin (r) (7
) Here, Rm is the intermediate value of the geomagnetic strength, r
is a variable, and k is the difference between this intermediate value Rm and the maximum value (or minimum value) of the geomagnetic strength. The initial virtual radius R6 is (7
) The purpose of converting a variable with a restricted angle, that is, Rm − into ≦Ro≦Rm+k (8), is to limit the value of Ro to a value within the range that can actually be taken, thereby increasing the efficiency of the subsequent calculation process. This is to ensure that the process is carried out efficiently and accurately.

In the above case, the values of Rm and k can be set in advance, but there is a method in which they are determined by constantly monitoring the sensor output value of the geomagnetic direction sensor and referring to the average geomagnetic strength in the area. can also be considered. In this case, the average geomagnetic strength value can be set as Rm, and the larger difference between Rm and the maximum or minimum value of the monitored geomagnetic strength can be set as k.

Hereinafter, the center coordinate value will be corrected using the least squares method. In this process, first, the initial virtual center value (Xo, Yo) and the output value of the geomagnetic direction sensor 1 (
The distance on the coordinates indicated by X (i), Y (i)l,
The sum of the squares of the differences from the distance on the coordinates indicated by the initial virtual radius R6 is calculated.

That is, the coordinates (Xo, Yo
) and the coordinates (
The distance Ri from X (i), Y (i)) is obtained by the following formula.

R1= [(X(i) The sum of squares (hereinafter referred to as sum of squares) J of the difference between the distance Ri indicated by the output value of and the distance indicated by the initial virtual radius R6 is obtained by the following equation.

J-Σ[f (X(k)-Xo) 2 In this embodiment, the minimum square correction is performed to correct the magnetization co-4 of the output circle by obtaining the virtual center value that minimizes the sum of squares J. The subsequent calculations are based on the multiplication method.

By the way, in equation (10), minimizing the sum of squares J means
, r (RO has been converted into a function dependent on the variable r by equation (7)). □JET; Blind 4-ru.

In this case, the following formula (11,), (1,2)
.

X of the sum of squares J given by (13). , Yo, it is a necessary condition that the derivative with respect to r be [il.

That is, (Xi Xo) −〇 (11) f3EδJ δr −Σ k, (Xi −
)(Rm+ksin(r))l eos(r
) = 0 Therefore, the above (11), (12), (
13) X that satisfies each expression. , Yo, r, then X. , Yo will be the center coordinates of the geomagnetic azimuth sensor 1 after correction.

However, -” 1 (11), (12), (13
), it is not possible to obtain the equation before analysis.

Therefore, in this embodiment, Newton-Raphson
Using the method, the following equations (14) and (1,5) are obtained.

(i6), (17) to correct XO, YO, r, 1. Let us find m (steps 1, 16).

σZ shall be.

In other words, finding the numerical solution for XO, YO, r is -1
--Notes (1., 4), (15), (16),
A modified scale that satisfies each formula (17), 1. It converges on finding m.

In this embodiment, X when the above-mentioned correction scales, l, and m are less than a predetermined value. , Yo becomes the center of the output circle of the geomagnetic direction sensor 1.

That is, the above-mentioned correction scale, 1. The value of m is
Convergence judgment constants εX, εy set to 0.

compared with εr, and if all values are smaller than the above constant (
YES in steps 118, 120, and 122),
The values of Xo and Yo at that time are set as the center coordinates of the output circle, and the processing of the vehicle body magnetization correction circuit 4 is thus completed.

On the other hand, if even one of the above correction amounts is larger than the convergence determination constant (N
O) , XO, YO, and r are each added with 1-note correction and ml (step 124), these are used as the new virtual center value and virtual radius, and the process returns to step 116.

Then, proceed to step 11 until a predetermined amount of correction is obtained.
Processes 6 to 124 will be repeated.

As mentioned above, in this embodiment, the calculation method of the least squares method is adopted, and it is assumed that the output circle of the geomagnetic direction sensor 1 originally draws a perfect circle, and the coordinates indicated by the virtual center value and the sensor output value are The center coordinates of the output circle are corrected by performing arithmetic processing to minimize the sum of powers of the difference between the distance to - and the virtual radius.

Therefore, even if the output circle is greatly distorted due to deterioration of the magnetic field environment, the center coordinates of the output circle can be corrected with high accuracy.

Furthermore, even if sensor output values are not obtained over the entire circumference of the output circle, the central coordinates of the output circle can be corrected with high accuracy because the calculation process is repeated so that the output values draw a perfect circle.

On the other hand, the converged value obtained by this type of arithmetic processing is not a minimum value but a local minimum value due to the nature of calculation. The multiplier may converge to a value that is far from the intensity value. However, in this embodiment, the virtual radius used in the tortoise calculation process is converted in advance into a certain conversion formula and used so that it is limited to those within the range of the actual geomagnetic strength. Therefore, the converged output circle radius always has a value that reflects the actual geomagnetic strength, and accurate center value correction can always be performed.

(Effects of the Invention) The vehicle direction meter according to the present invention stores the output value output from the geomagnetic direction sensor while the vehicle is running, as described in 1-1.
An initial virtual value of the center coordinate position of the output circle is calculated from a predetermined number of the stored output values, and an initial virtual value of the radius of the output circle is also calculated, and these initial virtual values are approximated from the geomagnetic direction sensor output value. The center coordinate position of the output circle is corrected by performing arithmetic processing so as to define the formula of the output circle.

Furthermore, the output circle radius as the initial virtual value used in the correction process described in item 1 is once converted to reflect the actual geomagnetic strength and used.

For this reason, it is possible to always perform accurate center value correction that reflects the actual geomagnetic strength, and there is also an advantage that it is not necessary to make one full rotation for correction.

[Brief explanation of the drawing]

Fig. 1 is a complaint correspondence diagram, Fig. 2 is a block diagram showing the system configuration of the present invention, Fig. 3 is an explanatory diagram of the configuration of the geomagnetic azimuth sensor, Fig. 4 is an explanatory diagram of the excitation characteristics of the geomagnetic azimuth sensor,
Figure 5 is a characteristic diagram showing the magnetic flux change in the permalloy core of the geomagnetic orientation sensor in the absence of a magnetic field, Figure 6 is an explanatory diagram of the detection operation of the geomagnetic orientation sensor, Figure 7 is a detection voltage characteristic diagram of the geomagnetic orientation sensor, Figure 8 is an explanatory diagram of vehicle running direction, Figure 9
The figure is an explanatory diagram of the output circle, Fig. 10 is an explanatory diagram showing a state in which a magnetic field other than geomagnetism is applied to the geomagnetic direction sensor, Fig. 11 is an explanatory diagram showing the movement of the output circle due to vehicle body magnetization, and Fig. 1.2 is a flowchart showing the processing procedure of the present invention. 1...Geomagnetic force position sensor 6...Permalloy core 7X, 7Y...Winding 8...Winding (for excitation) 9...Excitation power supply Patent applicant Nissan Motor Co., Ltd. Agent Patent attorney Kazu 1) Rules of construction Figure 1 Figure 10 Figure 2

Claims (1)

[Claims] 1. A geomagnetic azimuth sensor detects geomagnetic components as components in two mutually orthogonal directions on a horizontal plane, and determines the running direction of the vehicle based on the direction from the central coordinate position of the output circle to the coordinate position indicated by the geomagnetic components in the two directions. In a vehicle direction meter, there is provided a sensor output value storage means for sequentially storing output values output from the geomagnetic direction sensor, and a center coordinate of the output circle based on an arithmetic average of a plurality of output values stored by the sensor output value storage means. an initial virtual center value calculating means for calculating an initial virtual value of the position; an initial virtual radius setting means for setting an initial virtual value of the radius of the output circle based on the average strength of geomagnetism; an initial virtual radius limiting means for limiting the initial virtual radius to one within the range of the actual geomagnetic strength; and an initial virtual center value calculated by the initial virtual center value calculating means and an initial virtual radius limited by the initial virtual radius limiting means. correction amount calculation means for calculating the correction amount of each initial virtual value so that the radius defines the formula of the output circle approximated from the output value of the geomagnetic azimuth sensor; virtual value correction means for correcting each initial virtual value by the correction amount determined by the correction amount, and converging the initial virtual value to the center coordinate position and radius of the output circle approximated from the output value of the geomagnetic azimuth sensor. A compass for vehicles.