JPH0534605B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a course guidance device for a moving object, in particular, a course guidance device for a moving object based on the outputs of a magnetic direction sensor and a speed sensor mounted on a moving object such as a passenger car and detecting the direction of the earth's magnetic field. In a course guidance device for a moving object that displays the current position of the moving object on a display, in addition to the function of displaying the current position of the moving object, the absolute value of the azimuth vector signal detected by the magnetic azimuth sensor varies depending on the azimuth. This invention relates to a course guidance device for a moving object that has a function to warn when it is detected that the object is moving.

2. Description of the Related Art Conventionally, it has been considered to detect the direction of travel of a mobile object by detecting the direction of earth's magnetism using a magnetic direction sensor that detects the direction of a magnetic field. For example, the above-mentioned magnetic direction sensor and speed sensor mounted on a moving object such as a passenger car are used.
The current position of the passenger car is extracted based on the output of the sensor, and is plotted as a traveling trajectory of the passenger car on a display, for example, and a road map is associated with the display, so that the plot extends along the road on the map. A course guiding device for a moving object is being developed that guides the course as the vehicle moves. As mentioned above, the basic principle of the course guidance device for a mobile object using the magnetic orientation sensor is to know the running direction of the mobile object based on the direction of the earth's magnetism detected by the magnetic orientation sensor. be. Therefore, the detection signal of the magnetic azimuth sensor must be accurate azimuth information of the earth's magnetism. However, when the above-mentioned magnetic direction sensor is mounted in a vehicle made of iron plates, such as a passenger car, the output of the above-mentioned magnetic direction sensor is affected by the magnetization of the iron plates that make up the vehicle. Due to the offset, the accurate direction of the earth's magnetic field cannot be detected. In addition, due to the problem that there is anisotropy in the ease with which magnetic flux passes due to the shape of a vehicle with a steel plate structure (generally, the width of the vehicle body is small compared to the length in the direction of travel),
The detection sensitivity of the magnetic azimuth sensor to the terrestrial magnetism varies depending on the mounting position of the magnetic azimuth sensor in the vehicle or the direction of incidence of the terrestrial magnetism, which makes it impossible to accurately detect the azimuth of the terrestrial magnetism. These matters will be specifically explained with reference to FIGS. 1 and 2.

For example, in the magnetic orientation sensor 1 shown in FIG.・Excite with alternating current so that unsaturation is repeated. In this state, when a magnetic field (in this case, due to earth's magnetism) having a magnetic field strength He is applied as shown in the figure,
The above magnetic field strength He is applied to the orthogonal detection coils 4 and 5.
Voltages V _X and V _Y proportional to are generated. The generated voltages, that is, the outputs V _X and V _Y of the magnetic orientation sensor 1 are:
The X-axis and Y-axis components of the geomagnetic vector He are given by the following equation, where K is the proportionality constant. That _{is , V} The trajectory obtained with V _Y is the first
As shown in Figure B, the circle l ₁ is given by V _X ² + V _Y ² = (KHe) ² = a ² (2). Therefore, the direction of earth's magnetism, that is, the magnetic north direction, can be determined from the outputs V _X and V _Y of the magnetic direction sensor 1. As a result, for example, by making the Y-axis direction of the magnetic orientation sensor 1 coincide with the traveling direction of the moving object, it is possible to know the orientation of the moving direction of the moving object with respect to the magnetic north direction.

However, when the magnetic orientation sensor 1 is installed in a vehicle made of iron plates, such as an automobile, residual magnetism (due to magnetization during vehicle assembly) of the iron plates making up the vehicle Therefore, the XY output of the magnetic orientation sensor 1 is offset. That is,
The illustrated arrow Hr in FIG. 2 represents the residual magnetic vector, and the origin O of the X-Y output of the magnetic orientation sensor 1 is determined by the residual magnetic vector Hr to the illustrated point.
It will be displaced to O′. As a result, the locus of the output (V _X , V _Y ) of the magnetic azimuth sensor 1 based on the geomagnetic vector He becomes as shown in FIG. 2 (l _{2 )} .
Therefore, the direction of the geomagnetic vector He is indicated by the arrow shown in the figure.
Although it is in the O'P direction, the azimuth vector obtained by the output of the magnetic azimuth sensor 1 is a composite vector of the residual magnetic vector Hr and the geomagnetic vector He (the vector shown in FIG. 2),
Unable to detect accurate geomagnetic direction.

Further, as described above, the magnetic detection sensitivity of the magnetic azimuth sensor 1 differs depending on the azimuth based on the change in the angle of incidence of the earth's magnetism with respect to the vehicle. In this case, the output locus of the magnetic orientation sensor 1 is not a perfect circle like the locus l ₁ or l ₂ shown in FIG. 1 or 2, but is an ellipse (not shown). Further, although not shown, the influence of the installation position of the magnetic orientation sensor in the vehicle appears as a trajectory in which the long axis of the elliptical trajectory is inclined with respect to the X and Y axes.

Therefore, by performing offset correction and sensitivity correction on the output of the magnetic azimuth sensor 1, accurate geomagnetic azimuth information can be obtained. However, even if the above-mentioned correction is made at the start of driving, for example, the amount of magnetization of the vehicle body may change when passing through a railroad crossing using DC power transmission, or due to the passage of time. The amount of magnetization may change due to gradual demagnetization. As described above, when the amount of magnetization of the vehicle body changes, the offset correction performed in the initial state becomes incorrect. Therefore, if the vehicle continues to run without noticing the change in the amount of magnetization, there is a problem that an error will occur in the display of the running trajectory.

The present invention aims to solve the above problems, and monitors the absolute value of the corrected detection signal of the magnetic azimuth sensor, detects the variation of the absolute value due to the azimuth, and then adjusts the variation value to a predetermined level. A course guidance device for a moving object that appropriately recognizes the timing to re-correct the offset correction by issuing a warning when the above occurs, and enables accurate display of the travel trajectory. is intended to provide. This will be explained below with reference to the drawings.

FIG. 3 shows a block diagram of one embodiment of the present invention. The reference numeral 1 in the figure corresponds to Fig. 1, and 6
7 is a sensor output correction section that performs offset correction and sensitivity correction for the outputs X and Y of the magnetic orientation sensor 1; 7 is an absolute value calculation section that calculates correction data X output from the sensor output correction section 6; ₁ ,
8X and 8Y are absolute value correction units that calculate the absolute value of Y ₁ and correct the correction data X ₁ and Y ₁ from the sensor output correction unit 6 based on the output of the absolute value calculation unit 7. things to do, 9
10 is a speed sensor which outputs a clock signal every unit mileage of the moving object, for example, every 10 revolutions of a wheel; 10 is an integration unit which outputs the above absolute value in response to the clock signal from the speed sensor 9; The outputs X ₂ and Y ₂ of the correction sections 8X and 8Y are integrated and outputted. 11 is a trajectory storage section in which the outputs of the integration section 10 are sequentially stored and the display 12 is stored based on the stored contents. 13 is a quadrant determination unit that displays the traveling trajectory of the moving body, and 13 is a quadrant determination unit that displays the output of the sensor output correction unit 6.
₁₄ and 15 are gate _circuits ; 16 is a distribution circuit; 17 to 20 are first to fourth shift registers; , 21 to 24 are average value calculation units that read out the contents stored in the shift registers 17 to 20 and calculate the average value, and 25 is a comparison circuit unit that reads out the contents stored in the shift registers 17 to 20 and calculates the average value. The above average value calculation section 2
1 to 24 and outputs a warning signal if they do not match.

Referring to FIG. 3 showing an embodiment of the present invention, first, the traveling locus display function of the present invention will be explained. As stated at the beginning of this specification, the outputs X and Y detected by the magnetic orientation sensor 1 are subjected to offset correction and sensitivity correction in the sensor output correction section 6 based on the following equations, and are converted into correction data X ₁ , Y ₁ is output. That is, X ₁ = (X - a) c Y ₁ = (Y - b) d ... (3) In equation (3), a is the
is a Y offset correction value, c is an X sensitivity correction value, and d is a Y sensitivity correction value.

The correction data X ₁ and Y ₁ outputted from the sensor output correction ^section ₆ are sent to ^the absolute value correction section _8X and At 8Y, absolute value correction is performed based on the following equation, and the azimuth unit vectors X ₂ and Y ₂ are sent to the integrating section 10. That is, In the integrating unit 10, the azimuth unit vectors X ₂ and Y ₂ are sequentially integrated in response to the clock signal from the speed sensor 9, and are stored in the trajectory storage unit 11.
are stored sequentially. Then, the contents of the trajectory storage section 11 are read out and displayed on the display 12 as a traveling trajectory.

Next, another function of the present invention, that is, a function of immediately warning the occurrence of a change in the offset state due to a change in the amount of magnetization of the vehicle body will be explained. When the correction in the sensor output correction section 6 is performed correctly, the trajectory of the correction data X ₁ and Y ₁ output from the sensor output correction section 6 is, for example, as shown in FIG.
It becomes a right circle as shown in the locus _l1 . Therefore, the absolute value (√ ₁ ² + ₁ ² ) of the orientation vector represented by the correction data X ₁ and Y ₁ is approximately constant.
However, as stated at the beginning of this specification, when _the amount of magnetization of the vehicle body changes, the offset state described in connection with _FIG . 2. Trajectory shown in figure 2
The origin is shifted from the origin O of the X-Y axis, as shown in l ₂ . In other words, depending on the direction, the above absolute value (√
There will be a difference in X ₁ ² + Y ₁ ² ). In the present invention, paying attention to this, the above correction data X ₁ , Y ₁
Detect the discrepancy between the average value of the absolute value (√ ₁ ² + ₁ ² ) for each of the 1st to 4th quadrants and the reference value (corresponding to the arrow He in Figure 1 B or Figure 2) and perform the above procedure. A warning is given that a change in the offset state has occurred. This will be explained in detail below with reference to FIG. As mentioned above, the above correction data X ₁ ,
The absolute value (√ ₁ ² + ₁ ² ) of Y ₁ is calculated in the absolute value calculation unit 7, and it is also determined in which quadrant the azimuth vector represented by the correction data X ₁ and Y ₁ exists. is determined by the quadrant determining section 13. Then, in synchronization with the clock signal from the speed sensor 9, the above absolute value (√ ₁ ² + ₁ ² )
and the quadrant determination result are simultaneously sent to the distribution circuit section 16 via gate circuits 14 and 15. In the distribution circuit section 16, the absolute value (√ ₁ ² + ₁ ² )
1st to 4th based on the above quadrant determination results.
Shift registers 17 to 20 of FIG.
That is, the first to fourth shift registers 17
20 are predetermined to correspond to the above-mentioned quadrants, for example, the first shift register 17 is
The second shift register 18 stores the absolute value of the orientation vector within the quadrant range, and the second shift register 18 stores the absolute value of the orientation vector within the second quadrant range.
It is defined as follows. In this way, the plurality of absolute values (√ ₁ ² + ₁ ² ) divided into each quadrant and shifted and stored in the first to fourth shift registers 17 to 20 are stored in the average value calculation unit. In steps 21 to 24, respective average values are calculated. Each average value is compared with a reference value having a predetermined threshold value in the comparison circuit section 25, and when a mismatch is detected, a warning signal is outputted indicating that the offset correction needs to be re-corrected. In response to the warning signal, a warning lamp or a warning buzzer may be activated to notify the driver or the like. In addition, if the above warning is issued, please re-correct the above offset correction.
Needless to say, it is necessary to accurately display the travel trajectory so that the moving object can be guided on the correct course.

The reason why the absolute value data of each quadrant is taken in in synchronization with the output of the speed sensor is to take the average value of data over a certain distance as each quadrant data. This is because there are places on the road where the direction and absolute value of the geomagnetic field vary greatly locally, and if you stop at that place, the difference will be instantaneous if no averaging is performed, or constant if averaged over time. After a certain period of time, a warning about magnetization of the vehicle body will be issued, making it impossible to make a correct determination. Therefore, data for each quadrant is accumulated over a longer distance than local geomagnetic disturbances and averaged to detect only deviations in sensor correction values such as vehicle body magnetization.

Also, the reason for distributing the absolute value data to each quadrant is
The absolute value of the corrected geomagnetic vector should be constant regardless of the orientation of the vehicle body, and a deviation in the absolute value immediately indicates that an error has occurred in the detected orientation.

Regarding the magnetization of the vehicle body, which is a typical cause of error, the result is a difference in the absolute value of each quadrant.
In particular, it can be easily detected when the absolute values in opposite directions increase in one and decrease by the same amount in the other.

If the sensitivity correction of the sensor is incorrect, it can be detected by the fact that the absolute values of quadrants in mutually opposite directions increase or decrease in conjunction with the absolute values of other quadrants.

By using the absolute value of the geomagnetic vector as the criterion, data variation is reduced compared to averaging XY coordinate values within a certain range, and more data over a wider range can be averaged. More accurate judgment becomes possible.

As explained above, according to the present invention, the absolute value of the corrected detection signal of the magnetic azimuth sensor is constantly monitored, and fluctuations in the absolute value based on the azimuth are detected and the fluctuation value exceeds a predetermined level. To provide a course for a moving object that immediately issues a warning in the event of an offset correction, thereby making it possible to appropriately recognize the timing at which offset correction should be re-corrected, thereby obtaining an accurate driving trajectory display. A guidance device can be provided.

[Brief explanation of drawings]

1A and 1B are explanatory diagrams for explaining one embodiment of the magnetic orientation sensor used in the present invention, FIG. 2 is an explanatory diagram regarding the offset in the output of the magnetic orientation sensor, and FIG. A block diagram of the entire embodiment is shown. In the figure, 1 is a magnetic direction sensor, 6 is a sensor output correction section, 7 is an absolute value calculation section, 8X and 8Y are absolute value correction sections, 9 is a speed sensor, 10 is an integration section, 11 is a trajectory storage section, 12 is display, 1
3 is a quadrant determination unit, 14 and 15 are gate circuits,
16 represents a distribution circuit section, 17 to 20 first to fourth shift registers, 21 to 24 average value calculation sections, and 25 a comparison circuit section.

Claims (1)

[Scope of Claims] 1. A magnetic direction sensor and a speed sensor are mounted on a moving object, and a display mounted on the moving object and a map displayed in correspondence with the display screen of the display are provided, A course guidance device for a moving object configured to extract the current position of the moving object using a direction sensor and a speed sensor, plot the current position on the display, and correlate it with the map, comprising: an absolute value calculation unit that performs a calculation to obtain an absolute value based on the output of the magnetic orientation sensor that detects the X and Y direction components of the orientation vector, and outputs the absolute value, and the orientation vector of the output of the magnetic orientation sensor is
a quadrant determining section for determining which of a plurality of quadrants the object corresponds to, and an average value of each of the plurality of quadrants of the absolute values outputted from the absolute value calculation section is determined in advance. 1. A course guidance device for a moving body, characterized in that the device is configured to output a warning signal when the difference is compared with a reference value given by a predetermined value or more.