JPH0370840B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a travel information display device that can display the current position of a vehicle on a map displayed on the screen of a display device.

[Prior art]

Conventional travel information display devices use a travel distance detector such as an electromagnetic pickup to output an electric signal every time the vehicle travels a predetermined distance, and use a direction detector such as a magnetic sensor to monitor the vehicle's progress. Outputs an electrical signal corresponding to the direction. These electrical signals are then processed and calculated by a control circuit using a microcomputer or the like. In this case, the microcomputer reads the map information stored in the memory in advance and displays it on the display, and also displays the map on the screen of the display.
This displays the vehicle's current location mark and travel trajectory overlaid. Therefore, by looking at the display screen, the driver can know the current location of the vehicle he or she is driving, even on roads in unfamiliar areas, by comparing it with a map.

However, when a geomagnetic sensor is used as a direction detector in a conventional driving information display device,
Since a vehicle made of ferromagnetic material is magnetized by a disturbance magnetic field received from outside the vehicle, a bias magnetic field is applied to the geomagnetic sensor, resulting in the disadvantage that the orientation cannot be detected accurately.

[Summary of the invention]

Therefore, an object of the present invention is to provide a travel information display device that can detect a bias magnetic field applied to a geomagnetic sensor, automatically calibrate the orientation, and detect an accurate orientation.

In order to achieve such an object, the present invention provides a vehicle travel information display device having a travel distance detector, a geomagnetic direction detector, a map memory storing map information, a display, and a control circuit. The control circuit inputs the outputs of the mileage detector and the direction detector, calculates the current position of the vehicle, reads information from the map memory, and displays the map and the mark of the current position of the vehicle on the display. and compare the map information in the map memory with the vehicle's current position. When the vehicle is traveling on a straight road, the direction of the straight road obtained from the map information in the map memory and the direction obtained from the direction detector. An error is detected by comparing the traveling direction of the vehicle, and when the error reaches a predetermined value, the output of the direction detector is calibrated according to the error. explain.

[Embodiments of the invention]

FIG. 1 is a block diagram showing one embodiment of a travel information display device according to the present invention. In the same figure,
1 is a mileage detector that generates a pulse train signal as the wheels (not shown) of the vehicle rotate; 2 is a direction detector that is composed of, for example, a flux gate type magnetic sensor and outputs an analog geomagnetic signal; 3; numeral 4 is a microcomputer (hereinafter referred to as microcomputer); numeral 4 is a microcomputer (hereinafter referred to as microcomputer); numeral 5 processes the pulse train signal output from the mileage detector 1; an interface circuit which inputs a pulse to an interrupt terminal 4a of the microcomputer 4 every time the distance 4 (for example, 1 m) is traveled, and causes the microcomputer 4 to perform interrupt processing; 6 is a calibration processing means for calibrating the azimuth detector 2; 7; 8 is a display capable of displaying a two-dimensional screen, such as a CRT, which displays a road 7b and a mark 7c (hereinafter referred to as current position mark) indicating the current position of the vehicle on the screen 7a, and 8 is a switch (not shown). This is an operating device for the user to set the current position mark 7c on the screen of the display 7.

Note that the microcomputer 4 and interface circuit 5 constitute a control circuit 9. In addition, as shown in FIG. 2, the direction detector 2 uses the horizontal component force of the geomagnetic field H→, where θ is the angle formed by the traveling direction 11 of the vehicle 10 and the direction of the earth's magnetic field H→ (hereinafter referred to as the traveling direction). Assuming that the magnitude of is H, a component Ha parallel to the traveling direction θ of the vehicle 10 and a component Hb perpendicular to the direction θ can be expressed as follows.

Ha=kH _cps θ Hb=kH _sio θ However, k is a constant.

Therefore, the traveling direction θ can be calculated from the above equation as follows.

θ=tan ^-1 (Hb/Ha) Furthermore, as shown in FIG. 4, road information is stored in the map memory 3, and P ₁ to _{P 5} are roads P ₁ to _{P 2} indicated by dotted lines. Indicates the break point obtained by approximating ~P ₃ , P ₄ ~P ₂ ~ _{P 5} with a broken line, and indicates the break point (e.g. P ₁ )
coordinates (e.g. (x ₁ , y ₁ )), between the corner points (e.g. P ₁ and
A set of distances ₁₂ of P ₂ ) are sequentially stored in each memory M ₁ , M ₂ , . . . M _i+1 of the map memory 3 shown in FIG. For example, since the distance ₁₂ between the break points (P ₁ and P ₂ ) is approximated by a broken line, the relationship ₁₂ > _{1 2} =√( ₁ − ₂ ) ² + ( ₁ − ₂ ) ² holds true. However, roads _P2 to _P5 are straight roads, and this is stored in the memories Mi and M _i+1 of the map memory 3 shown in FIG. Also, microcontroller 4
A flowchart of the main routine of the program is shown in FIG. 5a, and a flowchart of the interrupt processing routine is shown in FIG. 5b.

Next, the operation of the driving information display device having the above configuration will be explained with reference to FIGS. 5a and 5b. First, the process is started by power-on reset of the control circuit 9, etc. In step 1, correction parameters ka and kb (described later) and a variable n are cleared to zero. In step _S2 , the memories M ₁ , M ₂ . In step _S3 , the user first moves the current position mark 7c displayed in the center of the screen 7a to the actual current position, but for the sake of simplicity, the setting of the current position mark 7c will be performed on the corner point. shall be taken as a thing. In step _S4 , the geomagnetic components Ha and Hb are input from the direction detector 2, and in step _S5 , using the correction parameters ka and kb, Ha←Ha−ka Hb←Hb−kb, where the arrow indicates the variable on the right side. Memory corresponding to After processing the contents, it is stored in the memory corresponding to the variable on the left side.

Correct based on. However, initially, the initial values of the correction parameters ka and kb are zero as shown in step _S1 . In step _S6 , the traveling direction θ of the vehicle 10 is calculated based on θ←tan ^-1 (Hb/Ha). In step _S7 , the branch road closest to the traveling direction θ is detected. For example, if the current position mark 7c is set at the turning point _P2 in FIG. 4, roads _P2 to _P1 , _P2 to _P5 , _P2 to
There are four possible paths, P ₃ , P ₂ to _{P 4} , and the inclination (or direction) of each road is calculated, and the branch road closest to the traveling direction θ of the vehicle 10 is detected. Based on the branch road (for example, roads P ₂ to _{P 3} ) detected in step _S7 , various constants Pm, Pn, r,
Set θmn,F. These constants are as shown in Fig. 6. The constant Pm corresponds to the end point P ₂ between the bending points (P ₂ - P ₃ ), and the coordinates are (xm, ym), and the constant Pn corresponds to the end point P ₃ , and the coordinates are (xm, ym). xn, yn). The constant r is the actual distance ₂₃ between the turning points (P ₂ to _{P 3} ), and the constant θmn indicates the orientation θ ₂₃ of the road ₂₃ approximated by a straight line.
The constant F is a flag indicating whether the road is a straight road or not, and is set to "1" when the road is a straight road, and to "0" otherwise. In this example, it is set to "0". With the above steps, the vehicle 10 is ready to travel. In addition, step S ₉
is repeatedly executed until the reset switch (not shown) included in the operating device 8 is operated, and when it is operated to reset the current position mark 7c, the process returns to step _S3 and the same procedure as above is performed. Try again. As described above, when the vehicle 10 is driven after displaying the map and setting the current position mark 7c,
Based on the pulse train signal output from the mileage detector 1, an interrupt command signal is input to the interrupt terminal 4a of the microcomputer 4 every unit distance 4. Therefore, the interrupt processing routine shown in FIG. 5b is executed. _R2 represents the starting point of this interrupt processing routine. Further, steps _S4 to _S6 are of course the same as steps _S4 to _S6 in FIG. 5a.
In step _S10 , the cumulative distance from the starting point Pm is calculated based on ←+Δ. In the following description, it is assumed that the vehicle 10 is traveling along roads _P1 to _P2 in the direction of turning point _P2 , as shown in FIG. Therefore, during this period, the constant Pm is
P ₁ , constant Pn is P ₂ , constant r is ₁₂ , constant θmn is the direction of road _{1 2} approximated by a straight line, constant F is “0”
is set to . In step _S11 , a straight line approximation road corresponding to the actual distance traveled by the vehicle 10 is created.
Movement distance c of current position mark 7c on PmPn
c←・PmPn/r Here, =√(-) ² +(-
)
Calculated based on ² . In step _S12 , the moving distance c of the current position mark 7c calculated in step _S11 is used to calculate the coordinates (xd, yd) for displaying the current position mark 7c based on xd←xm+c・sinθmn yd←ym+c・cosθmn. This is calculated and displayed in step _S13 . In step _S14 , it is detected whether the vehicle 10 has reached the end point Pn of roads Pm to Pn. If the vehicle 10 has not yet reached the end point Pn, step _S15 is executed. Step S ₁₅ a indicates roads Pm to Pn on which the vehicle 10 is traveling.
is a straight road or not based on the flag F. In this case, the vehicle 10 is on the road P ₁ to _{P 2} and the flag F is "0", so the return terminal is
From _R3 , the process returns to the main routine shown in FIG. 5a. The above process is repeatedly executed, and when the vehicle 10 reaches the turning point _P2 , this is detected in step _S14 , and step _S15b is executed. Step _S15b is the same step as step _S15a , and if the vehicle is not traveling on a straight road (which corresponds to this case), it jumps to step _S7 . Steps _S7 and _S8 are the same steps as steps _{S7 and S8 in} FIG. Below, vehicle 1
0 turns right at turning point _P2 and selects roads _P2 to _P5 . Then step S ₇ above
After executing, in step _S8 , various constants Pm, Pn,
Set r, θmn, and F. That is, the constant Pm is
P ₂ , constant Pn is set to P ₅ , constant r is set to ₂₅ , constant θmn is set to θ ₂₅ , and constant F is set to “1”. Step S ₂₃
Now, clear the variables Has and Hbs to zero (these variables Has and Hbs will be explained later),
The process returns to the main routine shown in FIG. 5a. When _{executing the} next interrupt routine shown in _{FIG .}
In addition to executing step a, steps _S16 and _S17 are also executed. That is, in step _S15a , flag F is set to "
1", and executes step _S16 . This step _S16 is combined with step _S18 , which will be described later, to calculate the average value of the geomagnetic components Ha, Hb,
This is to calculate Hb, Has←Has+Ha Hbs←Hbs+Hb Here, Has, Hbs: Based on the integration variables of Ha, Hb, Has and Hbs are integrated, and the number of integrations n
After calculating n←n+1 in step _S17 , the process returns to the main routine shown in FIG. 5a. The average value of the geomagnetic components Ha and Hb is determined in order to absorb fluctuations caused by the influence of other nearby vehicles, buildings, etc. on the values Ha and Hb at a certain point. The above process is repeatedly executed, and when the vehicle 10 reaches the turning point _P5 , this is detected in step _S14 , and step _S15b is executed. Now, Flag F
Since this is "1", this is determined in step _S15b , and step _S18 is executed. This step S ₁₈
As mentioned above, is combined with step _S16 to calculate the average value of the geomagnetic components Ha and Hb, and is calculated by ←Has/n ←Hbs/n, and in step _S19 , the number of integrations n is calculated. Clear to zero. In step S ₂₀ , the averaged geomagnetic component is used to calculate the straight road P ₂ ~
Calculate the average value of heading θ on P ₅ based on ←tan ^-1 (/). In step _S21 , the error between the averaged traveling direction and the direction _{θ25 of road 25 ,} which is a straight road, is calculated based on | _−θ25 | and a predetermined allowable error angle θe, | _−θmn |>θe. After comparing the sizes, if the above error |-θmn| is smaller than the allowable error angle θe, it is determined that the vehicle 10 is not magnetized by a disturbance magnetic field, etc., and the process proceeds to step _S7 .
Jump over to. If |−θmn| is greater than or equal to θe, step _S22 is executed, and the correction parameters ka and kb are calibrated based on ka←−H·sinθmn kb←−H·cosθmn. The above calibration operation will be further explained with reference to FIG. In the figure, 12a is a circular locus of geomagnetism H→(Ha, Hb) drawn when the vehicle 10 makes one turn, and the bias magnetic field
12b shows the case where there is no H _B , and 12b also shows the case where the bias magnetic field _B is present. As can be easily seen from the figure, the correction parameters ka and kb are the circular locus 12b
The coordinates (ka, kb) of the center of This step
After executing _S22 , execute steps _S7 , _S8 , _S23 ,
The process returns to the main routine shown in FIG. 5a. As a result, the correction parameters calculated in step _S22
ka and kb are used in step _S5 to calculate the geomagnetic component
Since Ha and Hb are calibrated, the traveling direction θ can be accurately calculated even if the bias magnetic field _B is applied to the vehicle 10.

Note that in the above embodiment, step _S4 in FIG.
Calibration calculations were performed using the calibration parameters ka and kb for the input geomagnetic components Ha and Hb in step _S5 , but the present invention is not limited to this; after calculating the correction parameters ka and kb in step _S22 , A magnetic field _-B that cancels the bias magnetic field _B corresponding to the coordinates (ka, kb) of the center of the circular locus 12b shown in FIG. 7 may be generated by the calibration processing means 6 of FIG. FIG. 8 shows a specific embodiment of the calibration processing means, which applies a correction magnetic field to the direction detector 2 using two sets of DC magnetic field generation coils 13a and 13b orthogonal to each other for calibration. It is something.
Furthermore, in steps S ₁₆ and S ₁₈ shown in FIG. 5b,
Although the traveling direction θ is averaged, it goes without saying that averaging is not particularly necessary when there are few minute fluctuations in the traveling direction θ.

〔Effect of the invention〕

As explained in detail above, the driving information display device according to the present invention detects that the vehicle is traveling on a straight road by comparing map information with the calculated current position of the vehicle. When the error between the heading obtained from the map memory of a straight road and the detected heading of the vehicle reaches a predetermined value, the bias magnetic field of the vehicle is detected, and based on this, the heading of the vehicle is determined by the heading detector. Since the heading is calibrated, it is possible to obtain an accurate heading even if the vehicle is magnetized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the travel information display device according to the present invention, FIG. 2 is a diagram for explaining the direction detector shown in FIG. 1, and FIG. 3 is a diagram showing the map memory shown in FIG. 1. Figure 4 shows the memory map.
FIGS. 5a and 5b are flowcharts showing an example of road information stored in the map memory in FIG.
The figure is a diagram showing road information to explain the operation in Figure 1, Figure 7 is a diagram to explain the calibration operation in Figure 1, and Figure 8 is another example of the calibration method shown in Figure 7. FIG. 1... Mileage detector, 2... Direction detector, 3
...Map memory, 4...Microcomputer,
4a...Interrupt terminal, 5...Interface circuit, 6...Calibration processing means, 7...Display device, 7a...
...Screen, 7b...Road, 7c...Current position display mark, 8...Control device, 9...Control circuit, 10...
Car, 11... Direction of travel, 12a and 12b
...Circular locus, 13a and 13b...DC magnetic field generation coil, Ha, Hb...Geomagnetic component, θ...Direction of travel, P ₁ , P ₂ ...P ₅ ... Break point of road approximated by broken line, M ₁ , M ₂ , M _i+1 ...Memory of map memory,
r...actual distance between corner points, c...movement distance in linear approximation. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A vehicle travel information display device comprising a travel distance detector 1, a geomagnetic direction detector 2, a map memory 3 storing map information, a display 7, and a control circuit 9. The control circuit 9 inputs the outputs of the mileage detector 1 and the direction detector 2, calculates the current position of the vehicle,
The information in the map memory 3 is read out, the map and the mark indicating the current position of the vehicle are displayed on the display 7, and the map information in the map memory 3 is compared with the current position of the vehicle to ensure that the vehicle is traveling on a straight road. When the vehicle is traveling, the direction of the straight road obtained from the map information in the map memory 3 is compared with the direction of travel of the vehicle obtained from the direction detector 2 to detect an error, and when the error reaches a predetermined value, the direction of the straight road is detected. A vehicle travel information display device that calibrates the output of the direction detector 2 according to errors.