JPH0674979B2 - Navigator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vehicle navigator, and in particular, when measuring a traveling direction of a vehicle by geomagnetism, a measurement error due to magnetization of the vehicle is corrected. Regarding the navigator made possible.

[Conventional technology]

Conventionally, a road map is displayed on a display device, and along with this, the current position of the vehicle is detected and displayed on this road map so that the driver etc. can be informed of where the vehicle is currently traveling. Known vehicle navigators. As a method to detect the current position of the vehicle,
The vehicle speed sensor and the azimuth sensor are used to measure the traveling distance by the output pulse of the vehicle speed sensor, the traveling direction is measured by the output of the azimuth sensor, and the current position of the vehicle is obtained from these measurement results.

A geomagnetic sensor is usually used as the direction sensor. That is, in this azimuth sensor, the X-coordinate component of the geomagnetism in the XY coordinate system (hereinafter referred to as V _X ) in which the traveling direction of the vehicle is the X coordinate and the direction perpendicular thereto is the Y coordinate.
And a Y coordinate component (hereinafter referred to as V _Y ) are detected,
The traveling direction is obtained from these ratios. In this case, when the vehicle makes one turn while the vehicle is not magnetized and the terrestrial magnetism is not disturbed, the obtained V _X and V _Y change in a sinusoidal shape with the same amplitude and different phases by 90 °. Then
Therefore, the locus by V _X , V _Y in the XY coordinate system is
The circle is centered on the origin of the XY coordinate system and has the radius of the amplitudes of V _X and V _Y.

By the way, in order to accurately detect the traveling direction of the vehicle,
It is assumed that the orientation sensor detects only undisturbed geomagnetism. However, in reality, the surrounding magnetism disturbs the earth's magnetism, and the vehicle's magnetization causes the error, which causes an error in the detection of the traveling direction of the vehicle and causes an incorrect current position display. become.

Conventionally, various methods for solving such a problem have been proposed. As an example, the technique disclosed in Japanese Patent Laid-Open No. 58-48811 discloses that the vehicle is made to make one turn to produce V _X and V _Y. By calculating the center of the circle in the XY coordinate system by
The amount of deviation of the center of this circle from the origin of the XY coordinate system is used as a correction value, and this correction value is also used as the X-side coil, Y
The current flowing through the side coil is corrected so that the center of the circle formed by V _X and V _Y actually obtained from the direction sensor coincides with the origin of the XY coordinates.

Further, as another example, the technique disclosed in Japanese Patent Laid-Open No. 58-135911 discloses a circular locus (reference circle) of V _X and V _Y obtained by detecting only undisturbed geomagnetism. After making a quick setting, display this and the circle locus (detection circle) by V _X , V _Y obtained by turning the vehicle once in a normal environment on the same display screen, and use the keyboard so that they match. By adjusting the volume by operating it, the currents flowing through the X-side coil and the Y-side coil of the azimuth sensor are corrected according to this operation.

[Problems to be solved by the invention]

The technique disclosed in Japanese Patent Laid-Open No. 58-48811 described above calculates the center of a circle by calculation and corrects the current flowing in each coil of the direction sensor, so that the vehicle can make one turn only. It is possible to automatically eliminate the detection error in the vehicle traveling direction. However, V _X , V _Y obtained from the orientation sensor
To calculate the center of the circle, use A / D (analog /
It is converted to digital data by a digital converter and supplied to the microcomputer. However, if all V _X and V _Y obtained when the vehicle makes one turn does not fall within the operating range of the A / D converter, these V _X , V _Y cannot find the correct center of the circular locus. In practice, the magnetization of the geomagnetic disturbances and vehicles according to the ambient environment, V _X which is obtained by turning one revolution of the _vehicle, V _Y is sometimes extend beyond the operating range of the A / D converter, V _X, V _{The part of the Y} that is outside the operating range of the A / D converter is fixed at the upper or lower limit of the operating range.
The center of the circular locus by these V _X and V _Y cannot be obtained from the output data of the D converter. Therefore, in this case, the correct traveling direction of the vehicle cannot be obtained.

On the other hand, the technique disclosed in Japanese Patent Laid-Open No. 58-135911 discloses that the reference circle and the detection circle are actually displayed and the two are coincided with each other. _X, even protrude V _Y from the operating range of the a / D converter, this part, when viewed from the entire circle, generally insignificant, not very trouble to match detection circle reference circle.

However, the user is required to perform an operation for making the reference circle and the detected circle coincide with each other after turning the vehicle once, which is a burden on the user. Moreover, in order to accurately detect the current position of the vehicle, these circles must be matched with each other with high accuracy, which is very troublesome. In the azimuth sensor, the detection sensitivity of V _X, V _Y there is a difference, these V _X, locus by V _Y may also be elliptical. In such a case, this ellipse must match the reference circle, which is impossible. In this case, even if the allowable range of the degree of coincidence is set, this allowable range cannot be increased so much. In some cases, the ellipse cannot fit within this allowable range, and in the end, accurate correction cannot be performed.

An object of the present invention is to solve the above problems and provide a navigator capable of automatically detecting a traveling method of a vehicle with high accuracy.

[Means for solving problems]

In order to achieve the above object, the present invention provides level correction means for level-correcting V _X and V _Y from an azimuth sensor and supplying them to an A / D converter, and A / D when the vehicle makes one turn. D
A determination unit that takes in the output of the converter and determines whether all the input levels of the A / D converter are within the operating range of the A / D converter, and forms an offset value according to the determination result of the determination unit An offset value forming means is provided, and the level correction amount in the level correcting means is determined by using the offset value.

[Action]

When the input level of the A / D converter exceeds the operating range of the A / D converter, that portion is fixed to the upper limit value or the lower limit value of this operating range. The determination means makes the determination by detecting whether the output data of the A / D converter matches the upper limit value or the lower limit value of the operating range of the A / D converter. The offset value forming means sets the offset values for V _X and V _Y in the level correction circuit so that the input level of the A / D converter is within its operating range.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a navigator according to the present invention, in which 1 is a vehicle speed sensor, 2 is a waveform shaping circuit,
3 is a direction sensor, 4 is a multiplexer, 5 is a level correction circuit, 6 is an A / D converter, 7 is a control circuit, 8 is a keyboard, and 9 is a display device.

In the figure, a vehicle speed sensor 1 generates a pulse (vehicle speed pulse) having a repetition frequency proportional to the traveling speed of the vehicle. After this vehicle speed pulse is waveform-shaped by the waveform shaping circuit 2,
The data is supplied to the control circuit 7 and data representing the traveling distance of the vehicle is generated.

Further, the azimuth sensor 3 detects the intensity of the geomagnetism, and the traveling direction of the vehicle is the X coordinate, and the direction perpendicular to this is the Y coordinate.
Geomagnetic X-coordinate component V in the XY coordinate system used as coordinates
_It outputs the _X and Y coordinate components V _Y. These V _X and V _Y are alternately selected in the multiplexer 4 by the selection signal S _e from the control circuit 7. Multiplexer 4
Of the output signal V _{X / Y} (V _X or V _Y ) is level-corrected in the level correction circuit 5 by the offset value V _off from the control circuit 7 and supplied to the A / D converter 6. A / D converter 6 receives the start signal S _t from the control circuit 7, A / D conversion takes in component V 'X _{/ Y,} which has been level-corrected and supplies the digital data D to the control circuit 7 at the same time , End signal S _{p is} also sent to the control circuit 7. Control circuit 7
Displays the traveling direction of the vehicle by processing the captured digital data D as will be described later, and further obtains data representing the current position of the vehicle from the traveling distance and displays it on the display device 9
Send to. On the display device 9, a road map is displayed,
The current position of the vehicle is displayed on this road map by the data from the control circuit 7.

The control circuit 7 generates the selection signal S _e every time the vehicle speed pulse is supplied from the waveform shaping circuit 2. Multiplexer 4
When this selection signal S _e is supplied, V _X and V _Y are selected once.

The level correction circuit 5 detects V _X , V detected by the direction sensor 3.
The levels of _Y are all corrected so that all of them fall within the operating range of the A / D converter 6. Below, A / D
The operating range of the converter is 0 (v) to 5 (v), and the operating point is 2.5 (v) which is the midpoint thereof. V _X and V _Y obtained from the direction sensor 3 when the vehicle makes one revolution have an intermediate value of 0.
(V), the phases are changed in a sine wave shape having a phase difference of 90 °. If there is no disturbance in the earth's magnetism, the vehicle is in a non-magnetized state, and if the directional sensor 3 has the same sensitivity and gain with respect to V _X and V _Y , the V _X obtained when the vehicle makes one revolution is obtained. , V _{Y in} the XY coordinate system has a radius R
It becomes the circle of (v). When such V _X and V _Y are obtained, when these are supplied to the A / D converter 6,
As shown in FIG. 2A, the offset value V _off is supplied to the level correction circuit 5 so that the intermediate value thereof coincides with the operating point (2.5 (v)) of the A / D converter 6, and The gain of the azimuth sensor 3 and the like are set so that the amplitude becomes 2 (v).

However, in reality, as described above, there are disturbances in the geomagnetism, sensitivity differences and gain differences with respect to the X and Y coordinates of the direction sensor 3, and the vehicle is also in a magnetized state, so V _X , V _Y
The amplitude and the level of are not in the ideal state as described above, and in the worst case, as shown in FIG. 2 (B), they may be out of the operating range of the A / D converter 6. The level correction circuit 5 further level-shifts these V _X and V _Y within this operating range by the offset value V _off , and the maximum values of V _X and V _Y actually obtained are shown in FIG. As shown in (B), when the operation range of the A / D converter 6 is equal to or higher than the upper limit value, V _X and V _Y are set to the offset value V.
is level shifted downward to _off, reverse, V _X, the minimum value of V _Y is below the lower limit of the operating range, V _X, shift the level of the V _Y upwardly offset value V _off. V _X and V _Y are A
If the offset value V _off is within the operating range of the / D converter 6, the offset value V _off is V _X , V output from the direction sensor 3.
_When the intermediate value of _Y is 0 (v), those intermediate values are
It is set to be 2.5 (v) (Fig. 2 (A)).
Therefore, the offset value V _{off at} this time is 2.5.
(V). In generalizing this, V _o
And

Further, as shown in FIG. 2 (B), when the maximum value of V _X and V _Y is equal to or higher than the upper limit value (5v) of the operating range of the A / D converter 6, the offset value V _off is V _X, the minimum value and the second view of the _{V Y} minimum value when _{(a) (0.5 (v)} ) by the difference between _{V o} (2.5 (v)) is set smaller than. Thus, if the peak-to-peak value of V _X and V _Y is 4 (v), the intermediate value is 2.5 by the level correction circuit 5.
It is set to (v). On the contrary, when the minimum value of V _X and V _Y is less than or equal to the lower limit value (0 (v)) of the operating range of the A / D converter 6, the offset value V _off is as shown in FIG. 2 (A). the maximum value of (4.5 (v)) the V _X, is set to be larger than the difference only V _o of the maximum value of V _Y. In this case also, the level correction circuit 5 sets the midpoint of V _X and V _Y to 2.5 (v).

FIG. 3 is a circuit diagram showing a specific example of the level correction circuit 5 in FIG. 1, in which 10 is an input terminal, 11 is an output terminal, and 12 is an output terminal.
Is a data line, 13 is a D / A converter, 14 is an operational amplifier, 15
~ 17 is resistance.

In the figure, V _X and V _Y selected by the multiplexer 4 (FIG. 1) are supplied to the operational amplifier 14 via the resistor 15. Further, the offset value V _off is supplied from the control circuit 7 (FIG. 1) via the data line 12, and D / A (digital /
After being converted to an analog value by the (analog) converter 13,
It is supplied to the operational amplifier 14 via the resistor 17.

Now, assume that the resistance values of the resistors 15, 16 and 17 are R ₁ , R ₂ and R ₃ , respectively, and the input voltage at the input terminal 10 is E ₁ and the output voltage of the D / A converter 13 is
Assuming E ₂ , the voltage E ₀ obtained at the output terminal 16 is Becomes As a result, as described with reference to FIG.
The offset value V _off can be set so that the D / A converter 13 can obtain the voltage E _{2 at} which the intermediate value of E ₀ becomes 2.5 (v).

Next, the operation of this embodiment, particularly the operation for detecting the traveling direction of the vehicle will be described.

In order to sequentially detect the traveling direction of the vehicle during traveling, first, it is determined whether V _X and V _Y obtained from the azimuth sensor 3 in the control circuit 7 fall within the operating range of the A / D converter 6 in all directions. If they do not fall within this operating range, the offset value V _off as described with reference to FIG. 2 is set to V _X ,
Set for V _Y respectively.

The operation of the control circuit 7 will be described below with reference to the flow charts of FIGS. 4 (A) and 4 (B).

First, in FIG. 4 (A), when the correction start switch provided on the keyboard 8 is operated, the data is initialized (step 101). Thus, the maximum value V _{X max} and the minimum value V _{X min} for _{V X,} the maximum value V _Y for _{V Y max}
And the minimum value V _{Y min} and V over flag are set to 0, and the offset values X _off and Y _off for these components are respectively set.
Set to V ₀ . At the same time, the vehicle starts to make one turn.

When the data initialization is completed, the digital data D is read for the first time from the A / D converter 6 (step 10).
2). The digital data D is V _X of the level correction circuit 5 one by TsuTsuta _1, which has been digitized in V _Y, below, in order to simplify the explanation, digital data is also V _X, the V _Y Represent. At this time, since the offset values X _off and Y _off have been initialized, the offset values X to V _X and V _Y supplied to the level correction circuit 5 are set.
_off and Y _off are zero.

This captured V _X is the maximum value V _{X max} (in this case, V _{X
X max} = 0) is compared (step 103), V _X <V
_{If X max} , proceed to step 108. V _X ≧ V _{X max}
If this is the case, this V _X is temporarily set to V _{X max} (step 104), and the V _Y taken in with this V _X is set.
_Is defined as the intermediate value V _{Y mid1} (step 105). This is because when one of V _X and V _Y is the maximum value, the other is an intermediate value. Next, the temporary maximum value V _{X max} is A / D.
The upper limit of the operating range of the converter 6 (in this case, 5
(V)) is determined (step 106).
When both are equal, the portion of 5 (v) or more is fixed to 5 (v) by the A / D converter 6, so that V _X is A /
May extend beyond the upper limit direction of range of D converter 6, and then proceeds to step 108 to "1" to 2 ⁰ bit of V over flag. The V-over flag consists of 4 bits, and each bit is assigned as follows.

Be equal to 2 ⁰ bit → V _{X max,} 2 ¹ bit → V _{X min} 2 ² bit → V _{Y max,} 2 ³ bits → V _{Y min} V _{X max} is in the operating range of the A / D converter 6 limit (i.e. if less than) 2 ⁰ bit of V over flag is sent to the step 108 as it is "0".

Above is been made in detection processing of the midpoint V _{Y mid1} maximum value V _{X max} and V _Y to this the V _X, the next step 10
Series of operations by the 8-112 is to detect the midpoint V _{Y mid2} minimum value V _{X min} and V _Y to this the V _X, step 103 only the compared V _X becomes V _{X min}
This is the same as the processing operation of steps 107 to 107. However, when V _X is equal to the lower limit value (0 (v) in this case) of the operating range of the A / D converter 6, the portion of V _{X that} is 0 (v) or less is 0 by the A / D converter 6. since is fixed to (v), and "1" to 2 ¹ bit of V over flag.

The series of operations in the next steps 113 to 117 is performed by the maximum value V _Y of V _Y.
Is used to detect an intermediate value V _{X mid1} of _{Y max} and V _X to this, when V _{Y max} is equal to the upper limit of the operating range of the A / D converter 6, 2 ² bits of V over flag is "1" Become. Similarly, step 118 to 122 to detect a minimum value V _{Y min} and the intermediate value V _X of the V _X for this _mid2 of V _Y performed by, when V _{Y min} is equal to the lower limit value of the A / D converter 6, 2 ³ bits of V over flag is set to "1".

When the above series of operations is completed, it is determined whether or not the vehicle has made one turn (step 123). If the turn is not completed, the process returns to step 102 and the same processing is performed. That is, while the vehicle makes one turn, steps 102 to 1
A series of operations by 22 is repeated. The number of vehicles is 1
When the vehicle turns around, the user operates the correction end switch provided on the keyboard 8. The step 123 determines whether or not the turning of the vehicle has ended depending on whether or not the correction end switch is operated.

When the vehicle turns one turn and operates the correction end switch, the maximum value V of V _X and V _Y that changes sinusoidally by this turn
_{X max} , V _{Y max} , minimum values V _{X min} , V _{Y min} , intermediate values V _{Y mid1} , V _{Y mid2} , V _{X mid1} , V _{X mid2} and V over flag are obtained. FIG. 5 shows a case where the locus 18 by V _X , V _Y is out of the operating range 19 of the square A / D converter 6. In this case, the maximum value V of V _{X
X max} exceeds the upper limit value 5 (v) of this operating range,
V over flag 2 ⁰ bit is (0001) of "1".

If it is determined in step 123 that the vehicle has made one turn, then the flow chart processing shown in FIG. 4 (B) is performed.

Here, first, it is determined whether or not the V-over flag is 0 (that is, all of the bits are "0") (step 124). If this is 0, all detected Vs
_X and V _Y are within the operating range of the A / D converter 6, and then the obtained intermediate point V _{X mid} from V _{X max} and V _{X min} to V _X obtained is _{Y max,} the intermediate value V _{Y min} from V _{Y min} V _Y is respectively sought (step 125),
Moreover, the operation by the correction factor of the amplitude K _Y is obtained for the correction coefficient K _X and V _Y amplitude (step 126) for V _X is completed. Here, these K _X and K _Y are obtained V
_As shown in FIG. 2 (A), the peaks and peaks of the sine waves of _X and V _Y are correction factors for making them 4 (v), and are 4 (v) and the actual amplitude value. It is expressed as a ratio with.

On the other hand, if the V-over flag is not 0, it is determined which bit of the V-over flag is "1". Now, when the 2 ⁰ bit or 2 ¹ bit is "1", the offset of V ₀ which level correction circuit 5 (2.5 (v)),
Although V _X is that protrudes from the operating range of the A / D converter 6, when 2 ⁰ bit is "1", V _X is the second
In the state shown in FIG. 3B, V _X is shifted to a lower level to obtain an offset value X _off such that its minimum value V _{X min} is 0.5 (v). Further, 2 ¹ if bit is "1", the minimum value V contrary to the state shown in FIG. 2 (B)
_{X min} is 0 (v) or less, and at this time, V
_X is shifted to a higher level and V _{X max} is 4.5 (v)
The offset value X _off is calculated as follows. Similarly, when the 2 ³ bit or the 2 ⁴ bit is "1", the offset value Y _off with respect to V _Y is obtained (above, step 12
7). From the above, the offset values X _off and Y _off set according to the V over flag are corrected from V _{0 as} follows.

2 ⁰ bits _{= "1" → X off =} V 0 + (V min -V X min) 2 1 bit _{= "1" → X off =} V 0 + (V max -V X max) 2 2 bits = "1 _{"→ Y off = V 0 +} (V min -V Y min) 2 3 bits _{=" 1 "→ Y off =} V 0 + (V max -V Y max) However, V _min, V _max, respectively the second As shown in FIG. 2A, it is the minimum value and the maximum value in the A / D converter 6 with respect to V _x and V _y obtained in an ideal state. In the case of FIG. 2A, V ₀ = 2.5 (v), V _min = 0.5 (v), V _max = 4.5 (v).

After the offset values X _off and Y _off have been set in this way, the vehicle is turned again to instruct to perform the operation shown in FIG. 4 (A) (step 128).

Based on this instruction, when the user operates the correction start switch of the keyboard 8 to start turning the vehicle, the fourth
The series of processing operations shown in FIG. At this time, in the level correction circuit 5, the multiplexer 4 outputs V _x , V
Each time _y is selected, the offset values X _off , Y _off determined in step 127 are supplied. Therefore, the series of processing shown in FIG. 4A this time is performed on V _x and V _y whose levels have been corrected with these offset values X _off and Y _off . Then, when the processing shown in FIG. 4 (A) ends, the processing shown in FIG. 4 (B) is performed again, and V _X , V
Intermediate value V _{X mid} for _Y, V _{Y mid} and the correction coefficient _{K X,} K
_Y is required.

As described above, the preparatory operation for detecting the traveling direction of the vehicle is completed, and the obtained data V _{X mid} , V _{Y mid} , K _X , _KY , X _off , Y
_off is V _X , when the vehicle is traveling and its direction is detected,
Used to modify V _Y.

Next, the azimuth measuring operation during traveling of the vehicle will be described with reference to FIG.

FIG. 6 (A) shows the operation of taking in V _X and V _Y from the azimuth sensor 3, and in this case, V _X and V _Y are taken in a plurality of times and averaged in order to improve the measurement accuracy.

After completing the preparatory operation shown in FIGS. 4 (A) and 4 (B),
When the measurement start switch in the keyboard 8 is operated to drive the vehicle, first, the reset and the like of the counter used for performing a predetermined count are initialized (steps 200 and 201).

When the continuous pulse is taken from the waveform shaping circuit 2 (step 202), the offset X _off obtained previously is set to the level correction circuit 4 (step 203), and the selection signal S _e is sent to the multiplexer 4 to send the multiplexer. 4 to V _X
Is selected (step 204). The selected V _X is corrected by the level correction circuit 5 according to the offset value X _off , and A
It is sent to the / D converter 6. A / D converter 6 is this V
Wait until the analog value of _X is sufficiently held (step 20
5), after a predetermined time has elapsed, thereby starting the operation of the connexion A / D converter 6 send a start signal S _t (step 206). A / D converter 6 has finished conversion operation, and outputs the connexion end signal S _P, such as to output the correct digital data D for the input V _X, captures the digital data D as V _X Te cowpea thereto (Step 207).

Then, the offset value Y _off is set to the level correction circuit 5 (step 208), and the selection signal S _e is output to cause the multiplexer 4 to select V _Y. In the same way, A / D
The digital data D is fetched as V _Y from the converter 6 (steps 210 to 212), and the count value n ₁ of the first counter is incremented by 1 (step 213).

As described above, the series of processing operations of steps 202 to 213 are performed every time the vehicle speed pulse is fetched, and the count value of the first counter is counted.
When n ₁ is a has decreased set value N _1, namely, V _X, when V _Y is taken _once N (step 214), the average of N ₁ pieces of V _X data VX and N ₁ pieces of V _Y The average data VY of is calculated (step 215).

When the average data VX and VY have been obtained as described above, the processing shown in FIG.

Here, first, it is determined whether or not the average data VX and VY are valid (step 216). The contents and necessity of this judgment will be described later, but when these are valid, the intermediate value V obtained in steps 125 and 126 of FIG.
Average data V using _{X mid} , V _{Y mid} and correction factors K _X , K _Y
Correct X and VY (step 217). This correction is data obtained in the ideal state where the obtained average data VX and VY are as shown in FIG. 2 (A) (that is, there is no disturbance of the earth's magnetism or magnetization in the vehicle). It will be converted as follows. That is, the average data VX, VY is corrected so as to represent a point on a circle having a radius of 2 (v) centered on a point at which the XY coordinate is 2,5 (v) in the XY coordinate system. . The data VX ₀ and VY ₀ obtained by this correction are respectively expressed as follows.

The first term on the right side of these equations (1) sets the above center as described above, and the second term also sets the radius of the circle to 2
(V).

By such a correction, even if the geomagnetism is disturbed or the vehicle is magnetized, the data VX ₀ and VY ₀ in an ideal state without them can be obtained. In other words, the data VX ₀ and VY ₀ that depend only on the undisturbed geomagnetism can be obtained. In addition, the direction sensor 3
To V _X, due sensitivity difference for V _Y, the correction coefficient K _X of V _X obtained in one round turn of the _vehicle, if the trajectory of V _Y is not a circle (for example, an ellipse) but, above equation (1) , K _Y is corrected to a circular locus, and the influence due to the difference in detection sensitivity of the direction sensor is removed.

Next, using these data VX ₀ and VY ₀ , the traveling direction θ of the vehicle
Is required (step 219). This is done by the following operation.

θ = tan (VY _o / VX ₀ ) When this traveling direction θ is obtained, the current position of the vehicle is obtained from the traveling distance data of the vehicle previously obtained from the continuous speed pulse, and from the data obtained as a result The current position of the vehicle is displayed on the road map displayed on the display device 9.

Then, unless there is a command to stop the measurement due to the stop of the vehicle or the operation of the predetermined switch on the keyboard 8, the process returns to the step 201 of FIG. 6 (A) and the same measurement process is performed. As a result, the vehicle moves and the current position display point of the vehicle on the display device 9 moves.

The above is the case where the magnetic field state for the vehicle (that is, the disordered state of the earth's magnetism, the magnetized state of the vehicle, etc.) is almost the same as the point and time when the preparatory processing shown in FIG. 4 is performed.
When the vehicle moves and the surrounding environment changes, the disordered state of the earth's magnetism and the magnetized state of the vehicle change. In such cases,
When the correction of the above equation (1) is performed in step 217, the obtained radii K _X (VX−V _{X mid} ), K _Y (VY− are obtained because the intermediate points V _{X mid} and V _{Y mid} are fixed and used. An error occurs in V _{Y mid} ). If this error is small, there is no problem, and even if a large error occurs, there is no problem if this error disappears in a short time as the vehicle travels, but a large error continues for a long time. In case of display device 9
Then, the current position is erroneously displayed for a long time, which is not preferable.

Step 216 determines whether the error between VX and VY is within a predetermined range, that is, the intermediate values V _{X mid} and V _{Y mid} and the correction coefficients K _X and K set at steps 125, 126 and 127 in FIG. 4 (B). _Y ,
With respect to the offsets X _off and Y _off , it is determined whether or not the traveling direction of the vehicle can be detected from the obtained V _X and V _{Y with} almost no error.

This determination is performed as follows. That is, as shown in FIG. 7, in the XY coordinate system, the X and Y coordinates obtained at step 125 in FIG. 4B are centered at V _{X mid} and V _{X mid} , respectively, and the radius R Imagine a circle. In this case, R = 2
(V). Therefore, the median of this circle is V _{X mid} , V
It is a locus by VX and VY that changes at _{Y mid} and has an amplitude of 2 (v) in a sine wave shape. This circle serves as a reference when measuring the traveling direction of the vehicle, and if the magnetic field state changes while the vehicle is traveling, the circular locus of VX and VY obtained at this time will deviate from this reference circle. This shift amount is the above error.

This error is allowed to some extent. That is, in FIG. 7, the radius is ± α (where
An annular area 401 surrounded by two circles of α ≠ 0 is an allowable range, and a circular locus 402 based on the average data VX and VY obtained by the processing of FIG. 6A is shown in FIG. As shown in FIG. 7A, when entering the annular area 401 centered on the origin 0, it is judged to be effective in step 216, and when it does not enter the annular area 401 as shown in FIG. 7B, the center is 0 ¹ , Determine that it is not valid. Specifically, for example, it is assumed that the obtained average data VX, VY represents one point on a circle having a radius r centered on the intermediate values V _{X mid} , V _{Y mid} , and R-α≤r≤R + α is satisfied. It is determined by whether or not it is. However, Is.

If VX and VY are valid as a result of this judgment, step 2
The current position of the vehicle is detected by the following processing, but
If these are not valid, step 201 in FIG.
The count value n ₂ of the second counter preset to N ₂ by
Is decreased by 1 (step 221). Note that N ₂ is a value sufficiently larger than N ₁ in step 214 (FIG. 6 (A)). Then, the count value n ₂ of this second counter
If is not 0 (step 222), the process returns to step 201 of FIG. 6 (A) and the process of obtaining the average data VX, VY is performed again.

As described above, if the state in which VX and VY as shown in FIG. 7B are not valid continues as the vehicle travels, the count value n ₂ of the second counter is 1 every time VX and VY are obtained. When n ₂ = 0, the warning process is performed (step 223) to warn that there is an error in the current position display. In this case, since the current environment is significantly different from the environment in which the preparation process of FIG. 4 was performed first, the user operates the correction start switch of the keyboard 8 to rotate the vehicle once. The preparatory process shown in FIG. 4 may be performed again by rotating it.

Here, the processing of the steps 221 and 222 by the second counter measures the traveling distance, and when VX, VY obtained even when traveling the predetermined distance determined by the value N ₂ is not continuously effective, a warning is generated. To do. However, if the environment of the vehicle changes to an environment equivalent to the one in which the preparatory processing shown in Fig. 4 was performed before traveling the predetermined distance, VX and VY are effective and the current position cannot be detected. To be executed.

In this way, when the environment changes, this is automatically detected and adjustments can be made according to this demarcation boundary, and the current position is accurately detected. If an error occurs in the detection result, but it returns to the normal state again, it is possible to save the trouble of making adjustments one by one.

〔The invention's effect〕

As described above, according to the present invention, by simply turning the vehicle once, the direction sensor output level from the operating range of the A / D converter due to the disturbance of the geomagnetic field or the magnetization of the vehicle is automatically detected. It is possible to set a correction amount for the protrusion, simplify the preparation operation that should be performed when measuring the current position of the vehicle, and improve the measurement accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the navigator according to the present invention, FIG. 2 is an explanatory view showing the operation of the level correction circuit in FIG. 1, and FIG. 3 is a circuit showing one specific example of this level correction circuit. 4 and 5 are flow charts showing the operation for forming offset values and correction data, and FIG. 5 shows an example of the case where the output level of the azimuth sensor in FIG. 1 is out of the operating range of the A / D converter. FIG. 6 is a flow chart showing an example of the vehicle current position measuring operation of the embodiment shown in FIG. 1, and FIG. 7 is a step in FIG.
It is explanatory drawing which shows an example of the determination method of 216. 1 ... Vehicle speed sensor, 3 ... Direction sensor, 5 ... Level correction circuit, 6 ... Analog / digital converter, 7 ...
... control circuit, 9 ... display device.

Claims (2)

[Claims] 1. A distance detecting means for detecting a traveling distance of a vehicle, an azimuth sensor for detecting first and second components of geomagnetism which are orthogonal to each other, and converting the first and second components into digital data. An analog / digital converter and an azimuth detecting means for processing the digital data to form traveling direction data of the vehicle are provided, and the current position data of the vehicle is obtained from the distance detecting means and the data obtained by the azimuth detecting means. In a navigator adapted to obtain and display a level correction means for level shifting the first and second components supplied from the direction sensor to the analog / digital converter, and at least one turn of the vehicle during turning operation. From the obtained output data of the analog / digital converter, the input signal of the analog / digital converter is converted to the analog / digital converter.
A judgment means for judging whether or not it is within the operation range of the digital converter and an offset value forming means for forming an offset value according to the judgment result of the judgment means are provided, and the offset is set as the level correction means. Thus, the navigator characterized in that the input level of the analog / digital converter in all directions of the vehicle can be set within the operating range of the analog / digital converter. 2. The determination means according to claim 1, wherein the analog / digital converter among the output data of the analog / digital converter by one turn of the vehicle.
A navigator characterized by detecting and determining whether or not there is an upper limit value or a lower limit value of an operating range of a digital converter.