JPH03152412A - Computing method for azimuth of vehicle - Google Patents

Abstract

PURPOSE:To enable output of a correct azimuth even when the center set beforehand shifts under the effect of magnetic disturbance, by correcting the set center by replacing it by the center of a circle determined by output voltages of sensors at three points different in the azimuth in the course of running of a vehicle, when an offset amount between the center of the circle and the set center exceeds an allowable value. CONSTITUTION:The center (X0, Y0) of a circle showing the relationship between an X-axis-side sensor output voltage and a Y-axis-side sensor output voltage which are obtained by rotating the direction of a magnetic azimuth sensor 1 before hand is determined and set before hand, and output voltages of respective axis sensors at three points different in an azimuth are determined in the course of running of a vehicle. While the center (X0', Y0') of a circle decided by these output voltages is determined, an offset amount between the center (X0', Y0') and the set center (X0, Y0) is determined, and when the offset amount is an allowable value or below, the correction of the set center (X0, Y0) is not conducted. When the amount exceeds the allowable value, the set center is corrected by replacing it by the determined center (X0', Y0'), and based on the corrected center of the circle and the X-axis-side and Y-axis-side sensor output voltages X and Y, the azimuth of the vehicle is computed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a vehicle orientation calculation method, and more particularly to a vehicle orientation calculation method for calculating the vehicle orientation based on the output voltage of a magnetic orientation sensor.

<Prior art> Two geomagnetism detection elements (X-axis coil, Y-axis coil) are arranged on the same plane with a phase angle of 90 degrees, and the geomagnetism is detected based on the detection signal of the amount of geomagnetism output from these detection elements. There is a direction measuring device that measures the traveling direction of a vehicle equipped with an element, and is used in automobile navigation systems.

FIG. 4 is an explanatory diagram of such an azimuth measuring device, in which 1 is a magnetic azimuth sensor, and a toroidal ferrite core 1a
The two sensing windings CXX with a phase angle of 90 degrees to each other
cocoil Y-axis coil) 1b.

1c is provided, and the excitation winding #! 1d is provided. A rectangular wave having a frequency f is applied to the excitation winding 1d via an oscillator 2 and an excitation circuit 3, and an excitation current necessary to magnetically saturate the core is applied. In such a state, when earth's magnetism is applied, an imbalance occurs in the magnetic saturation point and the excitation current changes, and based on the change, the detection winding 1b
, lc are generated at a frequency of 2f and a pulse voltage having a width proportional to the magnetic field strength H6. Therefore, these detection winding outputs are input to bandpass filters 4 and 5 with a frequency of 2f.

When rectified by the rectifier 6.7, a voltage expressed by the following formula % (1) () (θ is the direction and K is a constant) is output, and V
From x and Vy, the orientation θ can be calculated using the following formula (2).

Therefore, the direction calculation section 8 calculates Vx,
Vy is taken in, and the vehicle direction O is sequentially calculated using equation (2) and output. Incidentally, while rotating the magnetic orientation sensor 1, Vx and Vy are taken in at a predetermined sampling period, and the Vx and Vy are input to the display device 9 as X-axis and Y-axis coordinate values to generate an image and draw it on the CRT. In this case, a circle, which is a Lissage figure, is drawn.

Figure 5 shows a circle which is a beam serge figure, and the point Pi (i=1.2...) on the circle is the point where the j-th 11th sampling voltage Vx, Vy is the coordinate value Xi, Yi, Xll1ax when the vehicle is facing east, X win when facing west, Ymax when facing north,
Y win when facing south. Further, the coordinate values (Xo, YO) of the center Pc and the radius R are given by the following equation 1%(3) (3) (3). Therefore, voltages Vx and Vy are calculated from X and Y.

<Problems to be Solved by the Invention> By the way, if the amount of R magnetism of the vehicle is constant, the center position of the circle is constant, and the direction can be calculated accurately without distortion of the circle. However, if it is subjected to magnetic disturbances, such as when the magnet is moved close to a vehicle or when it is exposed to a strong directional magnetic field, such as when passing through a direct current railroad crossing, the center of the circle shifts and the 5-yen becomes distorted.

For example, if the center of the circle is shifted from Pc to Pc' as shown in Figure 6, and the vehicle is facing in the azimuth θ' force direction, θ' will not be calculated and an incorrect azimuth θ will be calculated. Put it away. That is, the coordinate value x0. of the center Pc before the shift. Using yo, 0 = jan-((Y'-Yo)
/ (X' - Xo'') is performed, and the correct orientation θ' is not calculated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a vehicle heading calculation method that can output a correct heading through correction even if the center moves due to magnetic disturbance.

Another object of the present invention is to provide a vehicle heading calculation method that can output a correct heading even if the circle is distorted due to magnetic disturbance.

Means for Solving the Problems> In the present invention, the above problem is solved by a magnetic orientation sensor and a center of a circle (Xo , Yo), means for calculating the output voltage of each axis sensor at three points with different azimuths θ while driving, and means for calculating the center (xa' - Yo') of the circle determined by these output voltages. , the center (xa' -Yo/ ) and the setting center (
means for calculating an offset amount between Xo and Y(1);
If the offset amount is less than the allowable value, the setting center (x 0 =
means for correcting the set center by replacing it with the obtained center (xo', y-') when the value exceeds the allowable value without performing correction of y o ); This is achieved by calculating the vehicle direction based on the output voltages X and Y.

Function> The center of the circle (Xo, Yo) indicating the relationship between the X-axis sensor output voltage and the Y-axis sensor output voltage obtained by rotating the direction of the magnetic orientation sensor is determined and set in advance, and the center of the circle (Xo, Yo) is determined and set when the vehicle is running. The output voltage of each axis sensor at three points with different directions within the circle is determined, and the center of the circle (x,
', yo') and the center (X0', Yo
') and setting center (Xo.

Find the offset amount between (Yo) and if the offset amount is less than the allowable value, do not correct the setting center < x, yo).
If the value is greater than or equal to the allowable value, the setting center is set to the center determined above (Xo
', Yo') and calculate the vehicle orientation based on the corrected circle center and the X-axis and Y-axis sensor output voltages X and Y. 1 is a block diagram of a related vehicle direction measuring device, 1 is a magnetic azimuth sensor, 1a is a toroidal ferrite core la, lb, and lc are two detection windings (X-axis coil, Y-axis coil), 1d is an excitation winding gld, 2 is an oscillator, 3 is an excitation circuit, 4 and 5 are bandpass filters, 6 and 7 are rectifiers, 11 is a multiplexer, 12 is a sampling hold circuit, 1
3 is an AD converter, and 14 is a processor for calculating direction.

15 is an operation section, and 16 is a vehicle speed sensor. below.

The processing of the orientation calculation processor 11 in FIG. 1 will be explained according to the flowchart in FIG. 2.

An initial setting command is input to the processor 14 from the operation unit 21, and then the vehicle is rotated to change the orientation of the magnetic direction sensor 1 to 1.
The output voltage V of the detection windings 1b and lc is detected at a predetermined period.
x, Vy are sampled via the multiplexer 11, sampling hold circuit 12, and AD converter 13, and the maximum and minimum values of these sampling voltages Xmax, Xa are determined.
Find +in, Yo+ax, Ymin, (3a) ~
(3c) Find the center (Xo, Yo) and radius R of the Lissajous figure circle (see Figure 5) and use the built-in memory 1.
4a (step 101). ...Initial Setting After initial setting, the direction calculation processor 11 is connected to the vehicle speed sensor 1.
The output voltages Vx, Vy (=
X, Y) are taken in via the 77t/multiplexer 11, the sunburst jig hold circuit 12, and the AD converter 13, and the vehicle heading θ is sequentially calculated and output using equation (4), and the heading θ and the output voltage are The relationship between X and Y is stored in the built-in memory 14a (step 102).

Thereafter, it is checked whether the preset correction time has elapsed (step 103), and if it has not elapsed, the process jumps to step 102, and the direction is calculated every cycle according to the vehicle speed.

On the other hand, if the correction time has come, from θtXtY stored in the built-in memory 14a, three sets of
Y (X□, Yl; X2.Yo;
R2(xz Xo')? + (Y2 y0/
) 2=R2(Xa Xo') 2+ (Yl-Y
ll') Solve 2=R2 to find the center of one circle (xa',
y, /), and the radius R' is determined from the following formula (%) (step 105).

Next, the magnitude of |R-R' l and the tolerance value εr are compared (step 106), and if |R-R' l is greater than or equal to the tolerance value Er, it is assumed that the circle is considerably distorted due to magnetic disturbance, and a buzzer is activated. Or depending on the display, the center (Xo, Yo
) and the radius R, and stop calculation of the direction and its output (step 107).
), as shown in (b), the circles C□ and C2 are distorted and become an ellipse E.
1. When it comes to E2, the circle created using three points on the ellipse will be C, C, 2, C21° C22, and its radius will be smaller or larger than the radius R of the circle C, C2. , the greater the distortion, the greater the degree.

On the other hand, if |R-R'l is less than the allowable value εr, there is no distortion, and the center (xo'
The offset amount 1x-xo'l IY-Y0 of each axis between the set center (Xo, Yo) and the set center (Xo, Yo) is determined, and it is checked whether the offset amount of each axis is less than the allowable value εx, iy (step 108).

IX-XI,' 1(fx and IY-Yo' If l<εy, the movement of the center is small and does not affect the calculation accuracy of the azimuth 0, so the set center (Xo, yo) is not corrected,
The process jumps to step 102 and returns to the subsequent processing. However, if IX -
, Yo') and R'.

Namely.

X0'→X.

Yo′→Yll R' → R Then jump to step 109) and step 102.

The subsequent processing is repeated using the corrected setting center and radius.

It should be noted that by setting tx=iy=o, it is also possible to configure a configuration in which any movement of the center is corrected. Moreover, in the above, one allowable value εX, εy&B.

1x-xt,' +≧EX or lY yu' l
The case where the setting center and radius R are corrected when ≧ty has been explained, but the first and second tolerance values εX□, fx2(t
xt<txz) # fyxt Ey2(fyx<f
y2), and then Hx xa' I -1"
If ya' I is less than or equal to ix□riYo, no correction is made, and which one is EX2. It may be configured such that if ε72 or more, a reset instruction is issued in step 107, and in other cases, correction is performed.

Further, in the above description, it has been determined whether to perform correction based on the offset amount of each axis between the centers, but it is also possible to configure the distance between the centers to be processed as the offset amount.

<Effects of the Invention> According to the present invention, the center of the circle (Xs', Yo') determined by the X-axis side and Y-axis side sensor output voltages at three points with different azimuths θ while the vehicle is running is If the offset amount between the set centers (Xo, Yo) is less than the allowable value, the set center (Xo).

Y. ) is not corrected, but if it exceeds the allowable value, the set center is replaced with the obtained center (xo', yo') and corrected. From then on, the corrected circle center and the X-axis and Y-axis sensor outputs are used. Since the vehicle orientation is calculated based on the voltages x and y, even if the center moves due to magnetic disturbance, the correct orientation can be output by correction.

Further, according to the present invention, the center (Xo, Yo) and the radius R
is set, and the radius R' of the circle determined by the sensor output voltages at three points is calculated.

|R-R' If l is greater than or equal to the allowable value, the center (Xo.

YO) and the radius R are reset, so even if the circle is distorted due to magnetic disturbance, the correct orientation can be output after the reset, and it is possible to prevent the wrong orientation from being output.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the direction measuring device according to the present invention, Fig. 2 is a flowchart of the direction calculation process, Fig. 3 is an explanatory diagram of the radius in the case of distortion, and Fig. 4 is an explanatory diagram of the conventional direction detecting device. , FIG. 5 is a diagram illustrating the principle of direction detection, and FIG. 6 is a diagram illustrating conventional problems. l... Magnetic direction sensor 11... Processor for direction calculation

Claims (2)

[Claims] (1) Find and set the center of the circle (X_o, Y_o) that shows the relationship between the X-axis sensor output voltage and the Y-axis sensor output voltage obtained by rotating the direction of the magnetic orientation sensor, and set it on the X-axis side. In a vehicle direction calculation method in which the direction of the vehicle is calculated using the Y-axis sensor output voltages X, Y and the set center of the circle (X_o, Y_o), three different directions are detected while the vehicle is running.
Find the output voltage of each axis sensor at the point, and find the center of the circle (X_o', Y_o') determined by these output voltages.
At the same time, find the offset amount between the center (X_o', Y_o') and the set center (X_o, Y_o), and if the offset amount is less than the allowable value, set center (X_o, Y_o)
o) is not corrected, and if the value exceeds the allowable value, the setting center is corrected by replacing it with the obtained center (X_o', Y_o'), and the corrected setting center and the X-axis side and Y-axis side sensor A vehicle direction calculation method characterized by calculating the vehicle direction based on output voltages X and Y. (2) Set the radius R along with the center (X_o, Y_o), calculate the radius R' of the circle determined by the output voltage at the three points, and if |R-R'| is greater than the allowable value, Instructs to reset the center (X_o, Y_o) and radius R, and when |R-R'| is less than a tolerance value, a correction process is executed according to the offset amount. The vehicle direction calculation method according to item 1.