JPH0682051B2 - Magnetization error correction method for azimuth detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention is a method for correcting a magnetization error of an azimuth detecting device, and in particular, is improved in that the error can be automatically corrected every time a predetermined amount of the magnetization error occurs. Correction method.

[Prior Art] In a moving body such as a vehicle, a ship or an aircraft, it is necessary to constantly detect the azimuth of the moving body in order to always confirm the current position. It becomes possible to know.

Such an azimuth detecting device is particularly useful for a navigation system of a mobile body, and in recent years, a navigation device is mounted on a normal general vehicle, and based on the traveling distance and the azimuth data from the azimuth detecting device, for example, on a CRT display. It is possible to trace the current position on the map displayed in, and it is possible to travel with peace of mind even when traveling on a road in which geography is not known.

The azimuth detecting device is capable of detecting the azimuth of the moving body from the direction of the terrestrial magnetism by fixing the azimuth sensor that electrically detects the earth's magnetism to the moving body, and the azimuth is detected with sufficient accuracy in practical use. .

However, in the geomagnetic detection type azimuth sensor, the occurrence of a magnetization error due to external magnetism applied to the moving body has been a serious problem.

In the case of a vehicle, such a magnetization error is typically caused by a strong leakage magnetic field when passing through a railroad crossing, etc., and when the vehicle body is magnetized above the geomagnetic level, the geomagnetism detected by the sensor is detected. There is a problem that a large coordinate error occurs in the vector locus circle which is the locus of the end point of the vector, and the navigation system does not operate correctly.

FIG. 4 shows a state in which such a magnetization error occurs, and assuming that the reference coordinates given to the sensor are the X axis and the Y axis, in the case of no magnetization, the coordinate origin "0" is taken as the center. The azimuth detection data moves on the vector locus circle as shown in FIG. Then, the component force in each axial direction at this time is Vx, Vy
Is required as.

Therefore, it is possible to accurately know the azimuth of the moving body from the current azimuth detection data on the vector locus circle.

However, when the moving body is magnetized by a strong magnetic field from the outside, this magnetization acts as a bias on the vector locus circle, and the detected azimuth data moves to the origin "O '" as shown in the figure. There was a problem of doing.

Therefore, as is clear from FIG. 4, it is understood that the azimuth data on the vector locus circle after magnetization, for example, the point a, is far from the actual azimuth.

Conventionally, such a magnetization error has been disclosed in, for example, Japanese Patent Laid-Open No. 59-
It was corrected each time by a complicated correction method as indicated by 100812.

FIG. 4 shows a schematic correction method in the conventional device. When the coordinate of the point a is detected and an abnormal value is detected, an alarm is given to the occupant of the moving body, and this alarm is issued. According to the above, the action of making a turn of the moving body to make a correction is performed.

In this one-round correction, the false vector locus circle due to the magnetization error is obtained by one round of the moving body, that is, 360-degree turn, and the magnetization error is corrected by this.

That is, the output circle obtained by turning the moving body 360 degrees around the magnetized state is a vector locus circle centered on the origin "O '" in FIG. The magnetization error is calculated from the false vector locus circle.

The calculation is performed by the correction calculation logic of the apparatus. For example, the correction coordinates surrounding the azimuth data a when the magnetization error is found are hypothesized, and the false origin "O '" is obtained from the plurality of data obtained at this time. Then, the coordinate error is obtained.

In FIG. 4, the virtual correction coordinates are two virtual x-axes corresponding to two points y ₁ and y ₂ on the Y-axis that are equidistant from the current direction data a in the opposite direction with respect to the X-axis. x (y ₁ ), x
Is set at (y _2), similarly, the virtual y axis y (x ₁₎ of x _1, x ₂ with respect to the Y axis on or X axis spaced equidistantly in the opposite direction from the orientation data a, y ( x ₂ ) is set.

Then, based on the data obtained by the one-turn turn on these corrected coordinates, a plurality of the corrected coordinates, that is, xa (y ₁ ), xb (y ₁ ) and ya in FIG.
The false origin “O ′” is obtained from (x ₁ ), yb (x ₁ ) and ya (x ₂ ) yb (x ₂ ).

As described above, according to the conventional device, the corrected coordinates of equal distance are virtualized on both sides of the current azimuth data a, and desired data is read from the one-turn data corresponding thereto, so that at least two correction coordinates are present on the virtual x-axis. At least two pieces of data can be taken on the virtual y-axis, and the magnetization error can be correctly obtained.

[Problems to be Solved by the Invention] However, in such a conventional device, the occupant is warned by detecting that the azimuth data a is an abnormal value, and the occupant makes a turn around the moving body by this warning. There is a problem in that it is necessary to move the magnet and correction of the magnetization error requires an extremely troublesome operation.

That is, the correction requires a special correction operation with respect to the moving operation of the moving body. For example, even in a vehicle or the like, the vehicle has to make a turn operation every time a magnetization error occurs. Corrective driving is often impossible,
This often caused the navigation system to be disabled due to magnetization errors.

Then, once the magnetization error occurs, the subsequent azimuth data is accumulated unless corrected, and there is a problem that it is impossible to construct a navigation system that can endure use.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to automatically perform desired correction whenever the above-mentioned magnetization error occurs, and improved automatic correction capable of always detecting accurate azimuth data. To provide a method.

[Means for Solving the Problems] In order to achieve the above object, the present invention uses an X-axis component and a Y-axis component of a geomagnetic vector detected by two magnetic sensors provided on a moving body and arranged orthogonally to each other. In an azimuth detecting device for detecting an azimuth of a moving body, a plurality of virtual x-axes parallel to the X-axis and a plurality of virtual y-axes parallel to the Y-axis are stored, and the end point of the detected geomagnetic vector is stored as The points on the virtual x axis and the virtual y axis are sequentially stored, and the same virtual x is stored.
At least one set of two geomagnetic vector end points on the axis and at least one set of two geomagnetic vector end points on the same virtual y-axis are extracted, and calculated from the coordinates of the extracted geomagnetic vector end points. The magnetization error is calculated from the starting point of the geomagnetic vector, and whether the magnetization error exceeds a predetermined value is constantly monitored, and if it exceeds, coordinate correction is performed with the starting point of the geomagnetic vector as the coordinate origin. In the case where the moving speed of the moving body is less than a predetermined speed, or when the geomagnetic vector detection value fluctuates by exceeding a predetermined value with respect to the previous detection value, It is prohibited to store the end point of the geomagnetic vector, prohibit the calculation of the magnetization error when the end point of the stored geomagnetic vector is less than a predetermined number, and calculate the end point of the stored geomagnetic vector. Low endpoint frequently eliminates during the deposition 磁誤 difference calculation.

[Operation] Therefore, according to the present invention, the magnetization error of the moving body is constantly monitored, and the occupant needs to perform some special operation, that is, a special correction traveling such as the conventional one-turn traveling. Instead, it is possible to automatically correct the magnetization error and always obtain a correct navigation function even when traveling a long distance.

Further, according to the present invention, it is possible to prevent the magnetization correction from being made incorrectly due to the false magnetization error at the extremely low speed, and it is judged that the data having extremely large fluctuation is noise, and it is eliminated. Therefore, it becomes possible to perform the magnetization correction which is hardly affected by noise.

Further, since the magnetization correction is performed with a predetermined number of data or more, stable correction processing can be performed. Further, of the fetched data, the data having a low appearance frequency is excluded during the correction process, so that more stable correction can be performed.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a preferred embodiment of the azimuth detecting apparatus to which the present invention is applied.

In the figure, the azimuth detecting means 10 is composed of a fluxgate type terrestrial magnetism detecting type azimuth sensor, and includes an annular core 12 made of a magnetically hard material such as permalloy. It is wound, and an exciting circuit 16 such as an oscillator supplies an exciting coil 12 with an AC signal of a predetermined frequency f, so that the exciting coil 12 is AC excited.

Further, the output coils 18 and 20 are wound around the annular core 12 so as to be orthogonal to each other, and the output coil 18 has a coil axis perpendicular to the traveling direction of a moving body such as a vehicle and the other output coil 20. It is fixed to the vehicle body according to the traveling direction of the vehicle.

As is well known, the excitation coil 14 is almost saturated by the excitation frequency f, and as a result, both output coils 1
Outputs 8 and 20 are cores 1 at both ends in the absence of an external magnetic field
Although removed by 2, when an external magnetic field, that is, geomagnetism is applied, a distorted waveform is generated in the output coils 18 and 20, and the amplitude of the second harmonic of this distorted waveform is detected by the fluxgate type sensor. Proportional to the magnitude of the applied DC geomagnetism, an output corresponding to the geomagnetism is obtained at both ends of the capacitors 22 and 24, and a quadrature output corresponding to the direction of the azimuth detecting means 10 can be obtained. The direction data on the locus circle can be obtained.

In the embodiment, the noise removing means 26 first removes the noises from the above-described known direction detecting means 10 along the X and Y axes, that is, along the axes of the coils 18 and 20. That is, although the geomagnetism is usually a constant value, it is greatly affected by the environment around the moving body, and for example, when the vehicle passes each other, the magnitude of the magnetic field changes according to the vehicle speed,
This causes an error in the azimuth data.

In this embodiment, noise is removed by a filter including a resistor and a capacitor, and the output from which the high frequency component has been removed in this way is supplied to the sampling and holding circuit 28.

The sampling and holding circuit 28 includes a switching element 30 that opens and closes each output of the noise removing means 26, a sampling signal thereof is obtained from a frequency divider 32, and direction data is taken in at a predetermined timing.

The sampling output is further smoothed by a filter 34 including a resistor and a capacitor, and is supplied to the data processing means 36 as azimuth data from which an error component is removed.

The data processing means 36 includes a CPU 38, and after the analog azimuth data is converted into a digital signal by the AD converter 40.
The CPU 38 adds the desired correction effect according to the present invention to this azimuth data, and then outputs it to the display 42 as an azimuth signal.

The CPU 38, the sampling and holding circuit 28, and the azimuth detecting means 10 are synchronously controlled by the timing control means 44.

A characteristic of the present invention is that the data processing means 36
Is storing a virtual x-axis and virtual y-axis data table which will be described in detail later. In the embodiment, this data table is stored in the ROM 46, and the CPU 38 uses this data table from the AD converter 40. It is possible to constantly compare and calculate the supplied azimuth data to monitor the magnetization error.

Although not shown in detail, the data processing means 36 is additionally provided with a data input / output interface and a register or RAM.

FIG. 3 shows the contents of the above-mentioned data table 46, and the positive origin of the positive coordinates given to the azimuth detecting means 10 when there is no magnetization error is indicated by "0", and on the X-axis. Is taken as VX and the coordinate on the Y-axis is taken as VY, and the circle centered on the positive origin "O" indicates a vector locus circle when there is no magnetization.

In the present invention, the data table 46 stores a plurality of virtual axis groups shown in a graph in FIG. 3, and in the figure, the virtual x axis group is a large number of axes that are equally spaced in parallel with the X axis. shown as if these virtual x-axis for each Y-coordinate and a _{y 1 ... y n, x (} y 1), x (y 2), x (y 3) ... x (y n) ...
Becomes Of course, a large number of such virtual x-axis groups are also provided at equal intervals on the negative side of the Y coordinate.

Here, considering a positive vector locus circle, it is understood that two points on the positive vector locus circle have the same value only by inverting the positive and negative values with respect to any of the virtual x-axis groups. In such a case, it is determined that at least the actually detected vector correction data does not have a magnetization error with respect to the X-axis in such a case, and the two pieces of data are calculated to magnetize in the X-axis direction. The amount when there is an error can be obtained by comparison with the data table.

Similarly, a plurality of virtual y-axis groups are set in parallel with the Y-axis, and a plurality of virtual y-axis groups are defined on the positive and negative sides of the X-axis at equal intervals as in the virtual x-axis group. Y (x ₁ ), y (x ₂ ), y corresponding to each X coordinate x ₁ ... x _n ... on the axis
(X ₃ ) ... y (x _n ) ...

Therefore, similarly, a positive vector locus circle having no magnetization error on each virtual y-axis has the same value in which two points on the circle are inverted, and when a magnetization error occurs, any virtual y is generated. The two data on the axis have different values, and the error value of the magnetization error along the y-axis can be known.

As described above, according to the present invention, of the detected azimuth data, from two data that coexist on the common virtual x-axis and two data that exist on the common virtual y-axis,
You can always know the magnetization error. Further, when this magnetization error exceeds a predetermined value, it is possible to correct the already obtained magnetization error amount and obtain accurate azimuth data.

FIG. 1 shows a flowchart of actual azimuth display and magnetization correction using the above-described present invention.

This routine starts at step 100 and is cyclically repeated continuously while the moving body is moving.
In step 101, all parameters are initialized, and the noise-removed azimuth data obtained from the azimuth detecting means 10 shown in FIG. 2 is subjected to the same azimuth calculation under the control of the CPU 38 in the data processing means 36 (step 10).
2) is performed, and the result is displayed in the direction on the display 42 (step 103) or, if necessary, displayed in a trace on a map provided in the moving body.

Although the conventional navigation system repeats the above steps, the present invention is characterized in that, in addition to such normal data processing, the magnetization error is constantly monitored and automatically corrected.

The automatic correction of the magnetization error in the present invention includes the calculation and the automatic correction of the magnetization error based on the virtual x-axis and virtual y-axis data tables described in FIG. 3 described above. Alternatively, some condition settings are added to eliminate erroneous magnetization correction due to a momentary pseudo magnetization error.

The first condition is a condition based on the vehicle speed, and step 104 determines whether or not the current vehicle speed is higher than the reference value vs. When the vehicle speed is extremely low, there is a possibility of picking up a false magnetization error. Therefore, in step 104, such data acquisition below a certain vehicle speed is prohibited.

The second condition is to eliminate the case where the change amount of the azimuth data is extremely large, and step 105 determines whether the change amount ΔV of the sampling data is equal to or less than a predetermined value G.

That is, it is unlikely that the azimuth will change extremely greatly in a normal moving state, and although such data includes some error, only the change component below the normally considered reference value is extracted and other extremely large changes are taken. The variable component prohibits its incorporation.

The sample data selected in this way is processed in step 10.
In FIG. 6, the data is temporarily taken into the memory, and in actuality, the CPU 38 in FIG. 2 stores and holds such sample data for magnetization correction in its built-in RAM or register.

The third condition defines the parameter of the sample data, prohibits the next calculation until the sample data reaches a specified number, for example, n, and step 107 counts the amount of the sample data taken in, and a constant value. The next arithmetic processing is prohibited until is reached.

The sample data of the specified number or more thus fetched is subjected to the frequency distribution process in step 108, and the process of excluding the data of extremely low frequency is performed for almost the same azimuth data position. Step 10 is whether data at the point has a frequency of i or more, for example.
The determination is made in 9, and it is determined whether or not sufficient data has been accumulated to automatically correct the magnetization error according to the fourth condition.

In the present embodiment, further, the automatic correction is not carried out prematurely. Therefore, as the fifth condition, the i data items subjected to the frequency processing in step 110 are averaged, and then step 11 is performed.
At 1, it is determined whether or not there are 1 of these average values.

Therefore, according to the present embodiment, the sampled azimuth data is sequentially fetched until all of the above five conditions are satisfied, and the normal azimuth display is executed during this period, but it is automatically Correction is suspended until sufficient data is accumulated.

When the average value reaches l, step 112 averages it. Then, in step 113, two orientation data (V _XE , V _XW ) on the same virtual x-axis and two orientation data (V _YN , V _YS ) on the same virtual y-axis are extracted.

Then, the calculation of the magnetization error is performed in step 114.
The coordinates (V _Xe , V _Ye ) of the starting point O ′ of the current geomagnetic vector are obtained based on the extracted four azimuth data in total.

As a matter of fact, this calculation is based on the virtual x shown in FIG.
It is performed from the calculation of the above-mentioned sufficiently accumulated data on the axis and the virtual y-axis, that is, the sample data taken in as described above should be distributed along the magnetization vector locus circle in FIG. By comparing this distribution state with the data stored in the data table 46, the starting point of the current geomagnetic vector can be obtained. Further, in this step, the magnetization error Hr is calculated.

Therefore, according to the present embodiment, it is understood that the value of the magnetization error Hr has already been obtained at this stage.

In the present embodiment, this magnetization error Hr is calculated in the next step 115.
Is compared with the reference value MG to determine whether the magnetization error Hr exceeds a predetermined value MG. If the magnetization error is less than or equal to the predetermined value, the contents of each memory are changed to Step 11.
It is reset at 6 and returns to the normal calculation and magnetization error monitoring routine again.

In this way, the routine proceeds while constantly monitoring the magnetization error, and when the magnetization error exceeds the predetermined value, that is, MG,
In step 117, automatic correction is performed.

That is, in this automatic correction, since the magnetization error Hr has already been obtained in step 114, this magnetization error is
This is executed by correcting Hr for the coordinates up to that point and removing the magnetization error.

Therefore, according to the present invention, the occupant of the moving body does not perform any special movement operation and correction operation, and while the magnetization error is constantly monitored, the correction operation is automatically performed when it exceeds a certain value. , It is possible to always fetch the optimum azimuth data.

[Effects of the Invention] As described above, according to the present invention, when detecting the azimuth of a moving body, the magnetization error of the azimuth data is constantly monitored, and when the magnetization error exceeds a certain value. Since the automatic correction is performed immediately, it is possible to always obtain accurate azimuth data and to provide extremely useful azimuth data to the navigation system of a mobile body without accumulating errors that often occur in the past. It will be possible.

[Brief description of drawings]

FIG. 1 is a flow chart of a preferred embodiment showing the azimuth display, the azimuth data monitoring, and the automatic correction operation to which the method for automatically correcting the magnetization error of the azimuth detecting apparatus according to the present invention is applied, and FIG. 2 is FIG. FIG. 3 is a schematic configuration diagram of an azimuth detecting apparatus for executing the flowchart shown in FIG. 3, FIG. 3 is an explanatory diagram showing a virtual x-axis and virtual y-axis data table used in the present invention, and FIG. 4 is a conventional magnetization error. It is explanatory drawing which shows and its correction effect. 10 ...... azimuth detection means 36 ...... data processing means 42 ...... Display 46 ...... data table _{x (y 1) ~x (y} n) ...... imaginary x-axis _{y (x 1) ~y (x} n) ... ... virtual y-axis

Claims (1)

[Claims] 1. An azimuth detecting device for detecting an azimuth of a moving body by means of X-axis and Y-axis components of a geomagnetic vector detected by two magnetic sensors provided on the moving body and arranged orthogonally to each other. A plurality of virtual x-axes and a plurality of virtual y-axes parallel to the Y-axis, and stores the end point of the detected geomagnetic vector as the virtual x-axis.
Sequentially store as points on the virtual y-axis, at least one set of two geomagnetic vector end points on the same virtual x-axis and at least one set of two geomagnetic vector end points on the same virtual y-axis. Extract and calculate the magnetization error from the starting point of the geomagnetic vector calculated from the coordinates of the extracted geomagnetic vector end point, and always monitor whether this magnetization error exceeds a predetermined value. A method of correcting a magnetization error in which coordinate correction is performed using the starting point of the geomagnetic vector as a coordinate origin, and the subsequent azimuth detection is performed, wherein the moving speed of the moving body is less than a predetermined speed, or the detected value of the geomagnetic vector is the previous value. When the detected value fluctuates beyond a predetermined value, the storage of the end point of the geomagnetic vector is prohibited, and when the stored end point of the geomagnetic vector is less than a predetermined number, the magnetization error is calculated. Prohibited, and the low endpoint frequent among end points of the stored geomagnetic vector eliminates during the deposition 磁誤 difference calculation, wear 磁誤 difference correction method of the azimuth detecting apparatus characterized by.