JPH0629731B2 - Vehicle compass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention detects a direction from the output circle center coordinate of the sensor to the coordinate indicated by the output value obtained by the geomagnetic direction sensor as the traveling direction of the vehicle. The present invention relates to a compass for a vehicle.

《Prior art and its problems》 Regarding the device that detects the traveling direction of the vehicle using the geomagnetic direction sensor, Automotive Technology Vol.39, No.5,
The one shown in 1985. is known, and in the geomagnetic direction sensor used in the device, a pair of windings are orthogonal to each other in a horizontal attitude.

Then, each of these windings obtains a geomagnetic component detection voltage (output value) corresponding to the interlinkage geomagnetism. When the vehicle travels in a uniform geomagnetism, the coordinates indicated by the detection voltage of those windings are used. A circle (an output circle of the geomagnetic direction sensor) is drawn on the coordinate plane.

Furthermore, during normal running of the vehicle, the direction from the coordinates of the output circle center to the coordinates indicated by the detected voltage of both windings is found as the running direction of the vehicle, and the center coordinates of the output circle are the geomagnetic field in the absence of magnetic field. It is given by the voltage obtained by both coils of the orientation sensor.

When the vehicle body is magnetized, the output circle moves, which makes it impossible to accurately detect the traveling direction.

In that case, the vehicle travels around, and the detection voltage obtained by both coils of the geomagnetic direction sensor is sampled during that time.

Then, in the above-mentioned conventional device, the offset amount of the center coordinate is obtained on the assumption that the coordinates indicated by the detected voltages exist on the circular locus, and based on the offset amount, during normal traveling of the vehicle, The coordinates indicated by the detected voltage of the geomagnetic direction sensor were corrected.

However, it is extremely rare that the geomagnetism is disturbed by buildings and the geomagnetism becomes uniform, so the locus drawn by the detected voltage of the geomagnetic direction sensor does not generally match the size of the output circle while the vehicle orbits. Therefore, the offset amount of the output circle center coordinates cannot be accurately obtained, and therefore, in the conventional art, a large error has occurred in the detection voltage correction of the geomagnetic direction sensor.

As a result, conventionally, there has been a problem that it is impossible to accurately detect the traveling direction of the vehicle despite the correction by the traveling of the vehicle.

<Object of the Invention> The present invention has been made in view of the above-mentioned conventional problems,
An object of the present invention is to provide a vehicle azimuth meter that can accurately set the output circle center coordinates of a geomagnetic direction sensor even when the geomagnetism is disturbed by the influence of external magnetism.

<< Structure of the Invention >> In order to achieve the above object, the vehicular azimuth meter according to the present invention is structured as shown in FIG.

In the figure, the geomagnetic direction sensor A decomposes the geomagnetic direction into two orthogonal directions on the horizontal plane, and the geomagnetic component in each direction is output as an electric signal indicating coordinates. From the output values output from the azimuth sensor, a plurality of output values are extracted such that the positional relationship between the coordinates indicated by each output value is at a predetermined distance.

Then, the first temporary coordinate calculating means C averages the plurality of extracted output values, and temporarily shows the center of the output circle drawn by the coordinates indicated by the output values output from the geomagnetic direction sensor A. Temporary coordinates are calculated.

Further, the distance calculating means D calculates the distance between the coordinates indicated by each output value and the first provisional coordinate for all of the extracted output values, and the average value of all the calculated distances is the distance average. It is calculated by the value calculation means E.

The standard deviations of all the calculated distances and the average value are calculated by the standard deviation calculating means F, and the extracted output value is calculated based on the average value and the calculated standard deviation. The area for invalidating is set on the coordinate plane by the area setting means G.

Further, the second provisional coordinate calculation means H averages valid output values among the extracted output values to obtain second provisional coordinates that provisionally indicate the center of the output circle.

Then, the central coordinate calculating means I performs the averaging process of the first temporary coordinate and the second temporary coordinate to obtain the central coordinate of the output circle.

<< Description of Embodiments >> Preferred embodiments of a vehicle azimuth meter according to the present invention will be described below with reference to the drawings.

FIG. 2 shows the configuration of a system to which the present invention is applied. In this system, the traveling position and traveling locus of the vehicle are displayed on a map.

The front part 20 of the figure composed of a CRT or the like for those displays
The CPU 22 determines the traveling position of the vehicle.

The CPU 22 obtains the traveling position of the vehicle relative to the reference position by an integration process using the detection signals of the vehicle speed sensor 24 and the geomagnetic direction sensor 26, and the reference position is a key input unit 28 including a keyboard or the like. To the CPU 22.

The map data displayed on the display unit 20 is fetched from the external storage device 30 via the data input unit 32.
The external storage device 30 is composed of a compact disk device, a ROM, and the like.

The processing of the CPU 22 is performed using the RAM according to the contents stored in the ROM of the memory unit 34, and the map data including the traveling position of the vehicle is read from the external storage device 30 into the CPU 22. The map is displayed on the display unit 20.

A vehicle speed sensor 24 of this embodiment is shown in FIG. 3, and a vehicle speed pulse is obtained by driving a reed switch 24c on and off by a magnet 24b provided on a speedometer cable 24a.

Further, FIG. 4 shows a geomagnetic direction sensor 26, and an annular permalloy core 36 is provided with windings 38X and 38Y orthogonal to each other.

A winding 40 is wound around the permalloy core 36, and the winding 40 is formed by the permalloy core 36 as shown in FIG.
Is excited by the excitation power source 42 until just before saturation.

When the above geomagnetic direction sensor 26 is placed in a non-magnetic field,
The magnetic fluxes Φ ₁ and Φ ₂ passing through the portions S ₁ and S ₂ of the permalloy core 36 have the same magnitude but opposite directions as shown in FIG.

Therefore, when the magnetic flux linked to the winding 38X becomes zero, the detected voltage (N is the number of turns) is also zero, and similarly, the detection voltage Vy of the winding 38Y is also zero.

Further, when the geomagnetic He is applied to the geomagnetic direction sensor 26 at right angles to the winding 38X as shown in FIG. And the magnetic fluxes Φ ₁ and Φ ₂ are asymmetrical as shown in FIG.

Therefore, the detection voltage Vx having the waveform shown in FIG. 8 is obtained at the winding 38X.

Since the geomagnetism He is parallel to the winding 38Y,
The geomagnetism He does not intersect with the winding 38Y, so that the voltage Vy is not generated in the winding 38Y.

The geomagnetic direction sensor 26 is mounted on the vehicle in a horizontal posture as shown in FIG. 9, and for example, as shown in FIG.
Intersect the windings 38X and 38Y, and as a result, the windings 38X and 38Y have a detection voltage V corresponding to the geomagnetism He.
x and Vy (output values) are obtained respectively.

The detection voltages Vx and Vy are expressed by the following equations (1) and (2), respectively, where the value K is the winding constant and the value B is the horizontal component of the geomagnetism He.

Vx = KB cos θ ... Equation (1) Vy = KBsin θ ... Equation (2) Therefore, when the width direction of the vehicle is used as a reference as shown in FIG. 9, the angle θ indicating the traveling direction is θ = tan ⁻¹ (Vx-Vy) ... Formula (3) is shown.

Then, as understood from the expressions (1) and (2), when the vehicle travels in the uniform geomagnetic He, the coordinates indicated by the detection voltages Vx and Vy of the windings 38X and 38Y are changed. As shown in FIG. 10, a circle (an output circle of the geomagnetic direction sensor 26) is drawn on the XY plane coordinates, and the output circle is represented by the following equation.

Vx ² + Vy ² = (KB) ² Equation (4) Since the coordinates determined by the detection voltages Vx and Vy of the windings 38X and 38Y exist on the output circle in this manner, the CPU 22 has the coordinate points (output points). The direction from the center O of the output circle is detected as the traveling direction of the vehicle.

Here, the vehicle body of the vehicle is magnetized, and as shown in FIG.
When interlinking with 8X and 38Y, 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 traveling direction of the vehicle performed by the CPU 22, and the traveling position display on the display unit 20 does not match the map display.

In this case, the correction switch 44 shown in FIG. 2 is operated, a correction command is given to the correction control unit 46, and the vehicle runs around.

The correction control unit 46 is mainly composed of a microcomputer, and performs a correction process for vehicle magnetization according to a correction command given from the correction switch 44.

The correction control unit 46 monitors the radius of the output circle by using the detection voltages Vx and Vy of the geomagnetic direction sensor 26, and when the radius becomes abnormal due to vehicle body magnetization as shown in FIG. Also, the above correction process is automatically performed.

FIG. 13 is a flowchart showing the procedure of the process performed by the CPU 22, and FIGS. 14 to 17 are flowcharts showing the procedure of the correction process performed by the correction control unit 46.

In FIG. 13, in the first step 100, the vehicle departure point (x ₀ , y ₀ ) is set using the key input unit 28.

In the next step 110, the vehicle traveling position (x, y) with the departure point (x ₀ , y ₀ ) as the reference position is the following formula (5),
It is obtained by the integration process according to the equation (6).

However, in both of the above equations, the value T is the elapsed time from the time of departure, the value V (t) is the vehicle speed at time t obtained based on the detection signal of the vehicle speed sensor 24, and the value θ (t) is the geomagnetic direction sensor 26. The respective vehicle traveling directions (see FIG. 9) at time t obtained based on the detected voltage are shown.

When the traveling position (x, y) of the vehicle is obtained in step 110, it is determined in step 120 whether the traveling position (x, y) of the vehicle is included in the map displayed on the display unit 20. If it is determined in step 120 that the vehicle running position (x, y) is not included in the currently displayed map, the map data including the running position (x, y) is output in step 130 to the outside. It is read from the storage device 30.

Then, in step 140, the traveling position (x, y) of the vehicle is displayed on the map, and when it is determined in step 120 that the traveling position (x, y) of the vehicle is included in the displayed map. Is also displayed.

Further, in step 150, it is determined whether or not the correction mode signal from the correction control unit 46 is received. If not received, the process returns to step 110 and the traveling position (x, y) of the vehicle is simply displayed on the map. To be done.

When the correction mode signal is received, step 160
The correction mode is displayed with.

A display example of this correction mode is shown in FIG. 18, and as can be understood from the same figure, the content for instructing the driver to drive the vehicle in a circuit is displayed on the display unit 20.

Then, in step 170, it is determined whether or not the output circle center coordinates have been calculated by the correction control unit 46, and if the center coordinates have not been calculated, the process returns to step 110, and the map and vehicle traveling position (x, y) are calculated. Along with the display, the correction mode display of step 160 is performed.

Further, when the output circle center coordinates are calculated by the correction control unit 46,
The center coordinates are fetched in step 180, and then the correction mode display is ended in step 190.

During the subsequent traveling of the vehicle, the vehicle traveling azimuth θ (t) is obtained in step 110 with reference to the output circle center coordinates obtained by the correction control unit 46, and the fifth (5) using the θ (t) is obtained. , The vehicle traveling position (x, y) is obtained by the equation (6).

Next, the operation of the correction controller 46 will be described with reference to FIGS. 14 to 17.

In FIG. 14, in step 200, it is judged whether or not the output value (radius of the output circle) of the geomagnetic direction sensor 26 is equal to or larger than the specified value. The output value of the geomagnetic direction sensor 26 may be equal to or higher than the specified value when the vehicle passes through a place where the magnetic field is strong such as a railroad crossing or when the vehicle body is magnetized.

Further, in step 210, it is judged whether or not the correction switch 44 is pushed, and the correction switch 44 is pushed when it is confirmed from the display of the display section 20 that the vehicle body is magnetized.

If YES at step 200 or YES at step 210, the correction mode signal is sent to the CPU 2 at step 220.
It is sent to 2.

Further, in step 230, the output circle center coordinates are obtained by the processing described later, and when this processing ends, step 2
At 30, the transmission of the correction mode signal is stopped and the correction mode display ends as described above.

FIG. 15 shows the contents of the processing in step 230, and this processing is carried out while the vehicle is traveling around.

When the vehicle starts to travel in accordance with the correction mode display in step 160 in FIG. 13 described above, the detected voltages Vx and Vy output from the geomagnetic direction sensor 26 draw a looped locus P as shown in FIG. 19, for example. .

The locus P is not a perfect circle as can be understood from the figure, which is caused by the disturbance of the geomagnetism due to the building street and the like.

In FIG. 15, in the first step 300, the extraction interval constant DLT8MIN shown in FIG. 19 and the constant DLTEN used to confirm the end of the vehicle round trip are set.
DMAX is set.

The extraction interval constant DLT8MIN is a constant preset based on the radius of the output circle, and the constant DLTEN
DMAX is a constant for setting the neighborhood area of the extraction representative point (described later) extracted in the initial stage (for example, the first stage).

Then, in the next step 310, the detected voltages Vx and Vy obtained at that time are the first extracted representative points {X (1),
Y (1)} is extracted and stored, and the extracted representative point number C is set to the value 1.

Further, in the next step 320, the detection voltages Vx, Vy output from the geomagnetic direction sensor 26 are collected.

Further, in step 330, the distance D between the coordinates (x, y) and the first extracted representative point {X (1), Y (1)}.
LT8 is calculated by the following equation.

Further, in step 340, it is judged whether or not the extracted representative score c has reached the value 9, and the number C is set to the value 1 at the start of the lap traveling.
Therefore, the process proceeds to step 360.

When the extracted representative score c reaches the value 9, the process proceeds to step 350 and the one round check process is performed.

Therefore, the details of the one-round check process in step 350 will be described with reference to the flowchart of FIG.

The round check processing, after extracting representative points c reaches the value 9, is repeated every time the output point Q ₁ to Q ₆ is obtained, when Q ₆ is obtained as understood from FIG. 19 Then, the process ends.

In FIG. 16, in step 400, extracted representative points (C =
The counter value n indicating the number 1) is set to 1. Then, in the next step 410, it is determined whether or not the counter value n has reached the value 2, and since the counter value n is the value 1, the process proceeds to step 420.

Then, in step 420, the distance DLTEND between the extracted representative point (C = 1) and the output point Q ₁ is calculated by the following equation.

In the next step 430, the magnitude of the distance DLTEND and the previously set constant DLTENDMAX are compared, and as is understood from FIG. 19, the distance DLTEND is larger than the constant DLTENDMAX at the output point Q ₁ . The process proceeds to step 440 and the counter value n is n +
The count is incremented to 1 and the process returns to step 410.

It should be noted that whether or not the traveling of the vehicle is completed is confirmed by whether or not the output point Q is present in the vicinity of the extracted representative point (for example, C = 1 to 4) extracted in the initial stage. In this embodiment, the radius DLTENDMAX centered on the extracted representative point (C = 1)
If the output point Q exists within the circle, it is confirmed that the vehicle has completed the round trip.

Therefore, when the counter value n reaches 2 in step 410, the one-round check process is once finished, and the process goes out to step 360 in FIG. 15 to obtain the next output point Q ₂ . Then, for this output point Q ₂ , steps 400 to 400 in FIG.
The processing of step 430 is performed, and thereafter, the same processing is similarly performed on the output points Q ₃ , Q ₄ , and Q ₅ .

Then, the output point Q ₆ is obtained, and the distance DLTEND and the constant D are obtained.
When the magnitude of LENDMAX is compared in step 430, the distance DLTEND is smaller, as can be understood from FIG. 19, so that it is confirmed that the vehicle is running round, and the one-round check process is finished.

As described above, the one-round check process is performed in step 350 of FIG. 15, and if the end of the vehicle lap traveling is not yet confirmed or the extracted representative score C has not reached the value 9, the process proceeds to step 360. move on.

In this step 360, the extraction interval constant DLT8MI
It is determined whether or not the distance DLT8 has reached N, and if the distance DLT8 is shorter than the extraction interval constant DLT8MIN, the process returns to step 320, and the processes of steps 320 to 360 are repeated. And the processing is about 50
Since it is set to be repeated in ms, the coordinates (x, y) at the initial stage of acquisition are shorter than the extraction interval constant DLT8MIN.

After that, when the distance DLT8 reaches or exceeds the extraction interval constant DLT8MIN, the process exits to step 370, and in step 370, the extraction representative score C is incremented.

Further, in step 380, the coordinate (x, y) at that time is 2
The th extraction representative point {X (2), Y (2)} is extracted and stored. After that, the processes of steps 320 to 350 are repeated.

As described above, a plurality of extracted representative points (C = 1, C = 2, ... C = 9) on the locus P shown in FIG. 19 are sequentially extracted while the vehicle is traveling, and the coordinates thereof are stored.

Then, in step 380, the extracted representative score C reaches 9, and this is confirmed in step 340, and when it is confirmed in step 350 that the vehicle orbiting is completed, the process proceeds to step 390.

FIG. 17 shows the processing procedure performed in step 390, and the first step 5 in FIG.
In 00, all the extracted representative points (C = 1, C =
2, ... C = 9) detection voltages Vx, Vy (output values) are averaged (arithmetic mean) according to the following equation, whereby the first provisional coordinates (CX1, CY) tentatively indicating the output circle center coordinates are obtained.
1) is required.

As described above, in step 500, the first temporary coordinate (CX
1, CY1) is calculated, the average distance between the first temporary coordinates (CX1, CY1) and each extracted representative point is calculated by the following equation in step 510.

However, Ri = [{CX1-X (i)} ² + {CY1-Y
(I)] ^1/2 and in the next step 520, the first temporary coordinate (CX1, CX
The standard deviation of the distance between Y1) and each extracted representative point is calculated by the following equation.

Further, in the next step 530, the average distance and the standard deviation σ
From this, an area satisfying Ri in the following equation is set.

−2σ ≦ Ri ≦ + 2σ And the output value indicating the extraction representative point that gives Ri that does not satisfy the above expression is invalidated as abnormal data. In this embodiment, as can be understood from FIG. 19, the extraction representative point C =
The output values indicating 5, C = 8 and C = 9 are invalidated.

A valid extraction representative point is selected from all the extracted representative points stored as described above, and the output circle center coordinates are provisionally calculated by averaging the output values indicating the selected extraction representative points from the following equation. The second temporary coordinates (CX2, CY2) shown are calculated.

However, α is the number of selected representative points.

Then, in the next step 550, the first temporary coordinates (CX1, CX
Y1) and the second temporary coordinates (CX2, CY2) are averaged to calculate the output circle center coordinates (CX, CY).

As described above, according to the present embodiment, the first provisional coordinates (CX1, CY1) are calculated by the averaging process of the plurality of extracted output values. Even if the locus P drawn by the coordinates indicated by the output value of the geomagnetic direction sensor 26 as shown in FIG. 19 is significantly distorted with respect to the perfect circle, the distortion error is canceled.

In addition, by performing an averaging process on the output values that produce the selected extracted representative point, the second provisional coordinate (CX
2, CY2) is calculated and the first temporary coordinates (CX1, CY) are calculated.
Since the output circle center coordinates (CX, CY) are calculated by performing the averaging process of 1) and the second provisional coordinates (CX2, CY2), the distortion error is further reduced.

Therefore, the output circle center coordinates (CX, CY) are accurately calculated, and the vehicle traveling azimuth is obtained using the output circle center coordinates (CX, CY), so that the azimuth can be obtained accurately.

After the desired number of extracted representative points C (= 1 to 9) are extracted, is there an output point Q (Q _{1 to} Q ₆ ) in the vicinity of the first extracted representative point (C = 1)? Since the end of the vehicle orbital traveling is confirmed by checking whether or not the vehicle is completely magnetized, the end of the vehicle orbital traveling can be surely confirmed even when the vehicle body is significantly magnetized.

Therefore, the automation of the start of the calculation of the output circle center coordinates (CX, CY), which is performed after confirming the end of the vehicle circular traveling, is ensured.

Further, since the traveling around the vehicle is confirmed as described above, it becomes possible to sample the geomagnetic component detection voltage in all directions of 360 degrees with respect to the center of the output circle, and the vehicle traveling direction is detected based on the sampled geomagnetic component detection voltage. Therefore, it is possible to detect the direction more accurately.

<< Effects of the Invention >> As is clear from the above description, the vehicle azimuth meter according to the present invention is an output value of the output values of the geomagnetic direction sensor in which the positional relationship of the coordinates indicated by each output value is a predetermined distance interval from each other. Since a plurality of values are extracted and the first temporary coordinates are obtained by averaging the plurality of extracted output values, the locus drawn by the coordinates indicated by the output values obtained while the vehicle is traveling around is true due to the disturbance of the geomagnetism. Even if the circle is significantly distorted, the distortion error can be canceled out.

Further, among the plurality of extracted output values, the second provisional coordinate is obtained by averaging the effective output values, and the center coordinate of the output circle is obtained by averaging the first provisional coordinate and the second provisional coordinate. The distortion error is further reduced.

Therefore, since the center coordinates of the output circle, which should be originally drawn by the coordinates indicated by the output value, are accurately obtained, it is possible to surely eliminate the orientation detection error due to the magnetization of the vehicle body or the like and obtain an accurate orientation.

[Brief description of drawings]

1 is a block diagram showing a preferred embodiment of a vehicular azimuth meter according to the present invention, FIG. 3 is a configuration explanatory view of a vehicle speed sensor, and FIG. 4 is a configuration of a geomagnetic direction sensor. Explanatory diagram, FIG. 5 is an explanatory diagram of the excitation characteristic of the geomagnetic direction sensor,
FIG. 6 is a characteristic diagram showing a magnetic flux change in the permalloy core of the geomagnetic direction sensor in the absence of a magnetic field, FIG. 7 is an explanatory view of the detection action of the geomagnetic direction sensor, FIG. 8 is a detection voltage characteristic diagram of the geomagnetic direction sensor, and FIG. FIG. 9 is an explanatory view of the vehicle traveling direction, the first
FIG. 0 is an explanatory diagram of an output circle, FIG. 11 is an explanatory diagram showing a state in which a magnetic field other than geomagnetism is applied to the geomagnetic direction sensor, FIG. 12 is an explanatory diagram showing movement of the output circle due to magnetization of the vehicle body, and FIG. Flowchart showing the processing procedure of the CPU 22, 14th
FIG. 15, FIG. 16, FIG. 16 and FIG.
18 is a flow chart showing the processing procedure of No. 6, FIG. 18 is an explanatory view of a display example for instructing the traveling around, and FIG. 19 is a correction controller 46.
FIG. 7 is a diagram for explaining the correction action of FIG. 20 ... Display unit 22 ... CPU 24 ... Vehicle speed sensor 26 ... Geomagnetic direction sensor 28 ... Key input unit 30 ... External storage device 32 ... Data input unit 34 ... Memory unit 36 ... Permalloy core 38X, 38Y ... Winding 40 ... Winding (for excitation) 42 ... Excitation power supply 44 ... Correction switch 46 ... Correction control unit

Claims (1)

[Claims] 1. A geomagnetic direction sensor in which the geomagnetic direction is decomposed into two orthogonal directions on a horizontal plane, and geomagnetic components in each direction are output as electric signals indicating coordinates, and a geomagnetic direction sensor output while the vehicle is traveling. Of the output values, the extraction means for extracting a plurality of output values in which the positional relationship of the coordinates indicated by each output value is a predetermined distance interval from each other, and the averaging processing of the plurality of extracted output values is performed. A first provisional coordinate calculating means for obtaining a first provisional coordinate that provisionally indicates the center of an output circle drawn by the coordinates represented by the output value output, and the coordinates represented by each output value for all of the extracted output values and the above Distance calculating means for calculating a distance from the first provisional coordinates, distance average value calculating means for calculating an average value of all calculated distances, all calculated distances and the average value Standard deviation calculation means for calculating the standard deviation of those distances based on, and area setting means for setting an area for invalidating the extracted output value on the coordinate plane based on the average value and the standard deviation. A second temporary coordinate that tentatively indicates the center of the output circle by averaging the valid output values among the extracted output values,
A vehicle azimuth meter comprising: temporary coordinate calculation means; and central coordinate calculation means for averaging the first temporary coordinate and the second temporary coordinate to obtain the central coordinate of the output circle.