JPH01321310A - Direction detecting device - Google Patents

Abstract

PURPOSE:To enable temporary correction by calculating a vector directed to the center of a circle from an origin of coordinates which vector corresponds to a terrestrial magnetism direction signal, calculating the variation between the previous and present directions, and obtaining a value of coordinates of the center of said circle from a value of coordinates of the present terrestrial magnetism direction signal and said vector when said variation is over a predetermined reference. CONSTITUTION:A terrestrial magnetism sensor 2 has such construction, for example, that a ferromagnetic body is wound by a pair of coils orthogonal to each other. A terrestrial magnetism direction signal generated from the sensor 2 is composed of two orthogonal components Vx and Vy. An operating means 3 has a microprocessor as its central function. A vector directed to the center of a circle from an origin of coordinates and corresponding to the terrestrial magnetism direction signal is calculated and stored. Then, the variation between the previously-detected direction and the present detected direction is calculated. If the variation exceeds a predetermined reference, the value of coordinates of the present direction signal and the stored vector are employed to calculate the value of coordinates of the center of the circle. By using this value of coordinates of the center of the circle, the movement of the circle can be corrected on the whole.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a direction detection device, and more particularly to a direction detection device using a geomagnetic sensor.

[Conventional technology]

The principle of an orientation detecting device using a geomagnetic sensor will be explained with reference to FIG.

The geomagnetic azimuth signal output by the geomagnetic sensor consists of two orthogonal components Vx and V. This vX.

When V is the coordinate value, when the geomagnetic sensor is rotated 360 degrees, the locus of the coordinate points corresponding to the geomagnetic azimuth signal draws a circle, which is represented by the circle A indicated by the broken line in FIG.

If the center o8 of this circle A is known, the coordinate point P corresponding to the geomagnetic direction signal output by the geomagnetic sensor and the center 0
．． The direction θ1 can be detected from (however, Vy
(the direction of is considered magnetic north).

A direction detecting device using such a geomagnetic sensor is used, for example, in a car's navigation system. In this case, for example, when the car body is magnetized, circle A moves, and the solid line in FIG. It will look like circle B shown in .

At this time, if the azimuth θb is detected from the coordinate point Pl corresponding to the geomagnetic azimuth signal and the center 0□ of the previous circle A without considering the movement of this circle, this azimuth θ will be an incorrect azimuth.

Therefore, Japanese Patent Application Publication No. 57-127807 and Japanese Patent Application Publication No. 58
JP-A-34314 proposes a technique for determining the center coordinate value of a circle defined by three coordinate points corresponding to three sets of coordinate values of a geomagnetic sensor and correcting the movement of the circle.

Also, find vX corresponding to the center of the circle from two sets of geomagnetic azimuth signals with different 8 and equal , and calculate vy corresponding to the center of the circle from two sets of geomagnetic azimuth signals with equal There is also a known technique for correcting the movement of a circle by determining .

[Problem to be Solved by the Invention] In the conventional technology for correcting the movement of the circle, from the viewpoint of accuracy, three or four coordinate points corresponding to the geomagnetic azimuth signal are distributed evenly on the circumference. is necessary.

Therefore, it is necessary to rotate the geomagnetic sensor 360 degrees, and when used in a navigation system for a vehicle, it is necessary to rotate the vehicle 360 degrees. This is so-called one-turn correction.

However, at any time, the geomagnetic sensor (or car)
Since the rotation is not necessarily performed by 60 degrees, there is a problem that there is a period during which no correction is made until m-.

Therefore, an object of the present invention is to provide an azimuth detection device that can perform temporary correction until the above-mentioned correction is made by rotating the geomagnetic sensor (or vehicle) by 360 degrees. be.

[Means to solve the problem]

The orientation detection device of the present invention includes a geomagnetic sensor that outputs a geomagnetic orientation signal consisting of two orthogonal components, and a geomagnetic sensor that outputs a geomagnetic orientation signal consisting of two orthogonal components.
a center coordinate value calculation means for calculating center coordinate values of a circle defined by three or more coordinate points corresponding to three or more sets of coordinate values when the components are coordinate values; and coordinate values based on the geomagnetic azimuth signal; and azimuth calculation means for calculating the azimuth based on the center coordinate value, the vector calculation means for calculating and storing a vector directed from the coordinate point corresponding to the geomagnetic azimuth signal to the center of the circle. and a change amount calculating means for calculating the amount of change between the previously detected direction and the currently detected direction, and when the amount of change is greater than a predetermined standard, the center coordinate of the circle is calculated from the coordinate value based on the current geomagnetic direction signal and the vector. The configuration is characterized by the provision of center coordinate value updating means for calculating and updating the values.

[Effect]

The vector directed from the coordinate point corresponding to the geomagnetic azimuth signal to the center of the circle does not change even if the body of the car is magnetized, unless the azimuth changes.

On the other hand, in this type of orientation detection device, the geomagnetic sensor samples at short intervals (for example, 0.1 seconds), so it is impossible for the orientation to change significantly in such a short period of time. If the direction detected this time has changed significantly compared to the previous time, it is considered to be due to magnetization of the car body, etc. 7 Therefore, in such a case, the coordinate values based on the geomagnetic direction signal of the geomagnetic sensor this time and The center coordinate value of the circle moved from the previous vector can be roughly calculated backwards. Then, by using this center coordinate value, the movement of the circle can be roughly corrected.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the drawings. Here, FIG. 1 is a block diagram of an azimuth detection device according to an embodiment of the present invention, FIG. 2 is a flowchart of the main part of the operation of the embodiment device shown in FIG. 1, and FIG. A coordinate diagram for explaining the operation. FIG. 4 is a coordinate diagram for explaining the operation when the movement of the circle is large. Note that the present invention is not limited to the following examples.

A direction detecting device 1 shown in FIG. 1 is installed in an automobile as an element of a navigation system, and includes a geomagnetic sensor 2 and a calculation processing means 3.

The geomagnetic sensor 2 has, for example, a basic structure in which a set of coils is wound orthogonally around a ferromagnetic material, and therefore, the geomagnetic direction signal it outputs has two orthogonal components v.
It consists of X and Vy.

The arithmetic processing means 3 has a microprocessor as its core, and operates as shown in FIG.

First, a check is made to see if a command for one-rotation correction has been given by the driver (St).

If the instruction to make one rotation correction had been given, the car would have
The geomagnetic azimuth signals (Vx, Vy) output by the geomagnetic sensor 2 are sampled three or four times while the geomagnetic sensor 2 is being rotated by 60 degrees, and the center 0. Calculate the coordinate values of. By this one-rotation correction, for example, the center 01 of circle A shown in FIG. 3 is obtained (S2). Note that the radius r can also be obtained if necessary.

Next, read the geomagnetic azimuth signal (Vx, Vy) output by the geomagnetic sensor 2 while the car is running. If this is taken as the coordinate value, for example, the coordinate point P1 shown in FIG. 3 will be obtained. (S3).

Next, the orientation θ is calculated from the obtained coordinate point P and the center 0□. In FIG. 3, V represents the direction θ with the direction being magnetic north (S4).

Next, from that coordinate point P, center 0. Vector α toward
is calculated and stored (S5).

Next, the previously calculated orientation θ1 is output (S6).

When not making one rotation correction (Sl), geomagnetic direction signal (
Vx, Vy) are read (S7), and the orientation θ is calculated from the corresponding coordinate point P and the previously calculated center 0 of the circle (S8>).

Next, it is checked whether the amount of change between the previous direction θ and the currently calculated direction θ is small according to a predetermined standard (39), 1
If rotation correction is not to be performed, step S7. Since S8 is repeated at a predetermined short period (for example, 0°1 second), unless there is movement of the circle due to magnetization of the car body, the previous orientation θ3 and the current orientation θb will not change significantly and will not meet the predetermined standard. The following is true.

Therefore, in this case, the current direction θb is the previous direction θ,
(SIO).

Then, a vector α directed from the point P toward the center 08 of the circle is calculated and updated (S5).

Further, the direction θ is output (S6).

When a car passes under a railway guard, the car body becomes magnetized, and for example, as shown in Figure 3, circle A becomes circle B.
Move like.

Then, in step S7, the coordinate point P is read,
Next, in step S8, the coordinate point PI and the center of the circle A 0. Since the azimuth θ is calculated, this azimuth θb is the previous azimuth θ.
It will be very different from 3.

If there is such a large change, the amount of change (θ, -θI,) exceeds the predetermined standard in step S9, so the process moves to step 311.

In step Sll, the coordinate point Pb is
The coordinate values of the center OL of the circle B moved from are calculated. Although this center O does not exactly match the center of the actual circle B that has been moved, since the time difference between the previous detection and the current detection is small, the error is small.

Next, check whether the amount of movement between the center O□ of the previous circle A and the center 0 of the current circle B is smaller than a predetermined value M (
512>, this predetermined value M is, for example, the previous circle A
The radius r can be used.

Move the center of the circle! If (O□-Oshi) is smaller than the predetermined value M, the current center Ob of circle B is the previous center 0. (313).

Then, the previous direction θ is output (S6).

In Fig. 3, using vector α from P, the center Ot! This is because finding azimuth .theta.' is nothing but assuming that azimuth .theta.8 is equal to azimuth .theta.8.

On the other hand, as shown in FIG. 4, if the amount of movement of the center (0 degrees - 0 degrees) is greater than or equal to the predetermined value M, an alarm prompting one-rotation correction is output (S14).

Then, the center 08 is replaced with the center OI (513), and the orientation θ8 is output (S6).

In this way, the center coordinate value of the circle, which is the standard for calculating the direction, is updated, so the direction can continue to be detected with a small error until the center coordinate value is accurately determined by one-turn correction. .

As another example, directional magnetic sensors are orthogonally arranged as geomagnetic sensors and 2+[li! Examples include those using an arranged structure.

〔Effect of the invention〕

According to the present invention, there is provided a geomagnetic sensor that outputs a geomagnetic azimuth signal consisting of two orthogonal components, and three or more coordinate points corresponding to three or more sets of coordinate values when the two orthogonal components are taken as coordinate values. A direction detection device comprising: a center coordinate value calculating means for calculating a center coordinate value of a circle defined by the above; and an azimuth calculating means for calculating a direction based on the coordinate value according to the geomagnetic direction signal and the center coordinate value. , a vector calculation means for calculating and storing a vector directed from a coordinate point corresponding to a geomagnetic azimuth signal to the center of a circle; a change amount calculation means for calculating an amount of change between the previously detected azimuth and the currently detected azimuth; is larger than a predetermined standard, the direction detecting device is characterized in that it is provided with a center coordinate value updating means for calculating and updating the center coordinate value of the circle from the coordinate value of the current geomagnetic direction signal and the vector. As a result, even when accurate direction detection becomes impossible due to magnetization of the automobile body, the error can be reduced and detection can be continued.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an orientation detection device according to an embodiment of the present invention, Fig. 2 is a flowchart of the main part of the operation of the embodiment shown in Fig. 1, and Fig. 3 shows the operation when the movement of the circle is small. Figure 4 is a coordinate diagram for explaining the operation when the movement of the circle is large. Figure 5 is a coordinate diagram for explaining errors in direction detection due to magnetization of the car body, etc. be. [Explanation of symbols] l... Direction detection device 2... Geomagnetic sensor 3... Arithmetic processing means VX, Vy... Component θ1 of the geomagnetic direction signal. θb...
・Direction 0,. 0. ...Circle center Pa, P...coordinate points. Applicant Daihatsu Motor Co., Ltd.

Claims (1)

[Claims] 1. A geomagnetic sensor that outputs a geomagnetic azimuth signal consisting of two orthogonal components; An azimuth comprising a center coordinate value calculation means for calculating a center coordinate value of a circle defined by a coordinate point, and an azimuth calculation means for calculating an azimuth based on the coordinate value by the geomagnetic azimuth signal and the center coordinate value. In the detection device, a vector calculation means that calculates and stores a vector directed from a coordinate point corresponding to the geomagnetic azimuth signal to the center of the circle, a change amount calculation means that calculates the amount of change between the previously detected azimuth and the currently detected azimuth; A direction detection device comprising a center coordinate value updating means for calculating and updating a center coordinate value of a circle from the coordinate value based on the current geomagnetic direction signal and the vector when the amount of change is larger than a predetermined standard. Device.