JPH0123047B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides information on traveling trajectories obtained based on the outputs of a course guidance device, particularly a magnetic azimuth sensor that detects the geomagnetic direction and a speed sensor that detects the traveling speed. In a course guidance device that updates the current position of a moving object and displays it in correspondence with a road map, a minute offset error of the magnetic azimuth sensor that occurs when the moving object is traveling is corrected based on the traveling trajectory information. The present invention relates to a course guidance device that displays an accurate travel trajectory.

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. Then, the current position of the passenger car is extracted based on the outputs of the magnetic azimuth sensor and speed sensor mounted on a moving object such as a passenger car, and is plotted as a traveling trajectory of the passenger car on a display, for example, and a road map is also displayed. A course guidance device for a moving object is being developed that guides a course by making the plots correspond to the above-mentioned display and extend along the road.

The principle of direction detection using the magnetic direction sensor described above is explained as follows.
This will be explained with reference to the figures. Reference numeral 1 in the figure is a magnetic azimuth sensor, which detects geomagnetism in two orthogonal axes, X and Y.
As shown in the figure, the angle θ in the Y direction of the magnetic azimuth sensor 1 oriented in the magnetic north direction can be determined. That is, the X-axis and Y-axis of the magnetic orientation sensor 1
The axial output (Vx, Vy) is expressed by the following equation (1).

Vx = Kx・Hex・sinθ Vy=Ky・Hex・cosθ ...(1) However, Hex represents the strength of the geomagnetic horizontal component, and Kx and Ky represent the sensitivity of the magnetic orientation sensor 1 in the X-axis and Y-axis directions. coefficient.

When the sensitivity of the X-axis and Y-axis of the magnetic direction sensor 1 is adjusted to be uniform, that is, Kx=Ky=
If K is set, then the angle θ of the magnetic direction sensor 1 in the Y direction with respect to the magnetic north direction can be determined by the following equation (2) based on equation (1).

θ=tan ⁻¹ (Vx/Vy) (2) In this way, the traveling direction of the moving object can be known from the output of the magnetic orientation sensor 1.
However, when the magnetic orientation sensor 1 is mounted in a vehicle such as a passenger car that is made of iron plates, the output of the magnetic orientation 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. Furthermore, the detection sensitivity may vary depending on the mounting position of the magnetic orientation sensor in the vehicle. Therefore, if the output of the magnetic azimuth sensor is simply used as data for determining the running direction, there is a problem that an error will occur in the current position display.

In order to solve the above-mentioned problem, the applicants of the present application, prior to filing the application of the present application, applied corrections such as offset correction and sensitivity correction to the output of the above-mentioned magnetic azimuth sensor, thereby determining the azimuth in the traveling direction of the moving object. We have proposed a course guiding device as shown in FIG. 2, which is equipped with a magnetic azimuth detecting device that accurately detects the direction of the vehicle. In the figure, 1 is a magnetic direction sensor, 2 is an A/D converter, 3 is an initial correction section, 4 is an angle conversion section, and 5
6 represents a unit vector generator, 6 a speed sensor, 7 an integrator, 8 a travel locus memory, and 9 a display unit.

In FIG. 2, the output Vx of the magnetic direction sensor 1,
Vy (analog signal shown by equation (1))
is converted into a digital signal by the A/D converter 2. An initial correction section 3 performs offset correction and sensitivity correction in an initial state on the outputs Vx and Vy of the magnetic azimuth sensor 1, which are converted into digital signals by the A/D converter 2. Note that the initial correction in the initial correction section 3 is performed based on equation (3).

V′x=k _x (Vx−Vx ₀ ) V′y=k _y (Vy−Vy ₀ ) ……(3) However, k _x and k _y are sensitivity correction values, Vx ₀ and
Vy ₀ is the offset correction value, and V'x and V'y are the outputs of the magnetic direction sensor 1 after correction.

Next, in the angle conversion section 4, the above-mentioned initial correction section 3
That is, the output of the magnetic direction sensor 1 after correction
Find the running direction angle θ using V′x and V′y. The traveling azimuth angle θ is determined by the following equation (4).

θ=tan ^-1 (V'x/V'y) ...(4) The unit vector generator 5 converts the output of the angle converter 4, that is, the traveling azimuth θ shown by equation (4). Find the sin and cos components, ie, sin θ and cos θ. Further, the speed sensor 6 outputs a clock pulse every time the vehicle travels a certain distance Δl in accordance with the rotation of the wheels, for example. In the integrator 7, each time a clock pulse is input from the speed sensor 6, that is, each time the moving object travels a distance Δl, the travel azimuth information input from the unit vector generator 5, that is, the sin θ and cos θ are successively integrated, and the integrated values are sequentially stored in the travel trajectory memory 8 as travel trajectory information of the mobile object. The traveling trajectory information stored in the traveling trajectory memory 8 is the third
As shown in the figure, the traveling position for each distance Δl
These are the coordinate values of P ₁ , P ₂ , ..., Pn, and generally the traveling trajectory information (Vi, Yi) corresponding to the traveling position Pi is calculated by the following formula:
(5).

Then, based on the contents of the traveling trajectory memory 8, the traveling trajectory of the moving body, that is, the position for each traveling distance Δl is displayed on the display section 9. For example, the display section 9
It is a display device composed of a CRT or an LCD, and a road map is displayed on the display section 9, and the travel trajectory is displayed in correspondence with the road map.

In the above-mentioned course guidance device, the accuracy of the traveling trajectory display is greatly influenced by the correction of the output of the magnetic orientation sensor 1 in the initial correction section 3, especially the suitability of the offset correction. This will be specifically explained with reference to FIGS. 4 and 5. In FIG. 4, OP→ indicates the output vector (represented by a unit vector with a magnitude of 1) of the magnetic orientation sensor 1 in the case of no offset. However, as shown in FIG. 4, if there is an offset a in the "east" direction, for example,
The output of the magnetic azimuth sensor 1 is combined with the above OP→ and the offset a, so that the detected azimuth changes from θ to θ'.
An error occurs in the travel trajectory information stored in the . Therefore, for example, when traveling straight in the azimuth angle θ direction, the traveling locus displayed on the display unit 9 is P ₁ as shown in FIG.
P _{′ 1} , P _{′ 2} , P′ ₁ , P′ ₂ ,
It will be displayed as a trajectory l ₂ following P′ ₃ .

Therefore, as described above, in the example illustrated in FIG. 2, consideration is given to performing correction in the initial correction section 3 to display an accurate traveling trajectory. However, even if an accurate initial correction is made,
When the above-mentioned moving object is made of a ferromagnetic material such as a car, the amount of offset (in the present invention (referred to as a minute offset amount) may fluctuate, and if you continue to drive without noticing this, an error will occur in the display of the traveling trajectory. Therefore, in order to obtain accurate travel trajectory information, the above-mentioned initial correction must be repeated many times.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned drawbacks, and aims to automatically correct the minute offset amount after the initial correction of the magnetic azimuth sensor based on travel locus information obtained from the travel of a moving object. Accordingly, it is an object of the present invention to provide a course guidance device that makes it possible to accurately display a traveling trajectory by obtaining highly accurate traveling trajectory information. This will be explained below with reference to the drawings.

6 to 10 are explanatory diagrams for explaining the basic principle of minute offset correction in the present invention, and FIG. 11 is a block diagram showing the configuration of an embodiment of the present invention.

The minute offset correction according to the present invention in the case where a minute offset exists in the azimuth "east" will be explained with reference to FIG. For convenience of explanation, it is assumed that the X axis in FIG. 6 (the same applies to FIGS. 7 to 10, which will be described later) coincides with the "east" direction, and the Y axis coincides with the "north" direction. In FIG. 6, the illustrated arrow a represents the minute offset amount,
OP→ is a unit vector obtained from the output of the magnetic orientation sensor 1 when the minute offset amount a does not exist, and the unit vector OP→ is the sinθ of the X component.
=x and cosθ=y of the Y component.
However, since there is a small offset amount a,
The actual output of the magnetic orientation sensor 1 corresponds to OQ→, as described above with reference to FIG.
The unit vector of OQ→ becomes OP→'. Therefore,
(OP→′−OP→) becomes the error vector PP→′ due to the minute offset amount a. That is, PP→′=OP→−OP→Therefore, OP→=OP→′−PP→′……(6) In the above equation (6), OP→ is the magnetic direction sensor 1
The original unit vector OP→ can be obtained by finding the error vector PP→′ caused by the existence of the minute offset amount a.

In Figure 6, PQ→=a, and generally 0<a
Since ≪1, ∠QPP′≒θ, therefore, PP→′=PQ→cos(∠QPP′)≒a cosθ Furthermore, the X component Δx _a and Y component Δy _a of PP→′ are expressed by the following equation (7 )
It is represented by.

Therefore, by finding the X component Δx _a and the Y component Δy _a of the error vector PP→' expressed by equation (7), equation (6) can be transformed into the respective X components of each vector,
Expressed in terms of the Y component, the following equation (8) is obtained.

(x, y) = (x' - Δx _a , y' - Δy _a ) ...(8) In other words, Equation (8) is This is an offset correction formula for the output (x', y') of the direction sensor 1.

Next, the minute offset correction when there is a minute offset amount b in the north direction will be explained with reference to FIG. Similarly to FIG. 6, OP→ is the original unit vector, OP→' is the unit vector due to offset, and PP→' is the error vector. and,
PS=b, ∠PSP'=∠PP'T≒θ, and the X component Δx _b and Y component Δy _b of the above error vector PP→' are
Similar to the example shown in FIG. 6, it is expressed by the following equation (9).

Generally, as shown in FIG. 8, when there is a minute offset amount as shown by the arrow c in the figure, the minute offset amount c is divided into the X component (arrow a in the figure) and the Y component (arrow b in the figure). By decomposing the error vector (Δx,
Δy).

Δx＝Δx _a +Δx _b =a cos ² −b sinθ・cosθ Δy＝Δy _a +Δy _b =b sin ² −asinθ・cosθ ...(10) Equation (10) above is the error vector when expressed as a unit vector. The X and Y components of the vehicle are as follows on the traveling trajectory.

That is, as described above with reference to FIG. 3, the coordinates of each traveling position are generally expressed by equation (5). For example, as shown in FIG. 9A, the X component ΔX _i of a unit vector from point P _i-1 to point P _i
and Y component ΔY _i is expressed by the following equation (11).

_{∆X i = _ _ _ _} Since it is for a vector, the error vector (Δx′ _i ,
Δy′ _i ) is expressed by the following equation (12).

Δx′ _i = Δl・Δx _i = Δl(a cos ² θ _i −b sinθ _i・cosθ _i ) Δy′ _i = Δl・Δy _i Δy′ _i = Δl・Δy _i = Δl(b sin ² θ _i −a sinθ _i・cosθ _i )……(1
2) However, as mentioned above, since the travel trajectory information is coordinate information (X _i , Y _i ) calculated based on the azimuth information (sinθ _i , cosθ _i ), the following equation (13)
Based on the equation, the above equation (12) can be expressed as the following equation (14). That is, sinθ _i = ΔX _i / Δl = (X _i −X _i-1 ) / Δl cosθ _i = ΔY _i / Δl = (Y _i −Y _i-1) ...(13) Expression (13) is Substituting into equation (12), Δx′ _i = Δl{a・(Y _i −Y _i-1 ) ² /(Δl) ² −b・(
X _i −X _i-1 )/Δl ・(Y _i −Y _i-1 )/Δl} Δy′ _i = Δl{b・(X _i −X _i-1 ) ² /(Δl) ² −a・ ( X _i −X _i-1 )/Δl・(Y _i −Y _i-1 )/Δl} Therefore, That is, the coordinates (X' _i , Y' _i ) of the corrected position P' with respect to the point P are expressed by the following equation (15).

X′ _i =X _i-1 +ΔX′ _i =X _i-1 +ΔX _i −Δx′ _i =X _i-1 +(X _i −X _i-1 )−Δx′ _i X _i −Δx′ _i Similarly, Y′ _i =Y _i −Δy′ _i (15) The correction according to the above equation (15) is illustrated as shown in FIG. 9B.

Although the correction at a certain traveling position P _i has been described above, it goes without saying that the correction is performed on all traveling locus information. That is, traveling position P ₁
The coordinate X′ ₁ after correction of the X component at P _o
X′ ₂ ,… are X′ ₁ =X′ ₀ + _{ΔX 1} −Δx′ ₁ =X ₀ +(X ₁ −X ₀ )−Δx′ ₁ =X ₁ −Δx _{′ 1 2} −Δx′ ₂ =X′ ₁ +(X ₂ −X ₁ )−Δx′ ₂ =(X ₁ −Δx′ ₁ )+(X ₂ −X ₁ )−Δx′ ₂ =X ₂ −Δx′ ₁ − Similarly to Δx′ ₂ , X′ ₃ =X ₃ −Δx′ ₁ −Δx′ ₂ −Δx′ ₃ and is generally expressed by the following equation (16).

X′ _o =X _o − _o 〓 ⁱ⁼¹ Δx′ _i (16) Furthermore, the Y component is similarly expressed by the following equation (17).

Y′ _o = Y _o − _o 〓 ⁱ⁼¹ Δy′ _i ...(17) Therefore, as shown in equation (15) above, based on the traveling trajectory information stored in the traveling trajectory memory, By calculating X′ _i and Y′ _i and sequentially integrating them, and making corrections based on equations (16) and (17) above, accurate travel trajectory information can be obtained.

After all travel trajectory information is corrected in this way, the travel trajectory based on this corrected trajectory information is displayed on the display, and the quality of the correction amounts a and b is determined by making it correspond to the road map. do.

With the above steps, the correction of the trajectory information after traveling is completed.

The post-correction based on the minute offset amounts a and b when the vehicle returns to the running state is as follows.

The i-th trajectory information has been corrected, and when traveling is resumed from the i+1th position, the coordinate components are X _i+1 = X′ _i +ΔX _i+1 Y _i+1 = Y′ _i +ΔY _i+1 …… (18) From equation (11), ΔX _i+1 = Δlsinθ _i+1 ΔY _i+1 = Δlcosθ _i+1 ... (19) Therefore, the correction amounts Δx' _i+1 and Δy' _i+1 are From equation (12), Δx′ _i+1 = Δl(a cos ² θ _i+1 −b sinθ _i+1 cosθ _i+1 ) Δy′ _i+1 = Δl(b sin ² θ _i+1 −a sinθ _i+1 cosθ _i+1 ) ...(20) Therefore, the coordinate components after correction are X′ _i+1 =X′ _i +ΔX _i+1 −Δx′ _i+1 X′ _i+1 =X′ i +ΔX _i+1 −Δx′ _{i +1} =X′ _i +Δl(sinθ _i+1 −a cos ² θ _i+1 +b sinθ _i
+1 cosθ _i+1 ) Similarly, Y′ _i+1 =Y′ _i +Δl(cosθ _i+1 −b sin ² θ _i+1 +a sin
θ _i+1 cosθ _i+1 )...(21)

As described above, trajectory information corrected based on equation (21) is obtained every time a pulse from the speed sensor is input.

FIG. 10 is a schematic diagram of trajectory correction, and for simplicity, only correction of Δy′ _i is shown. l ₃ is the trajectory before correction. The corrected trajectory in which the corrections shown in equation (17) are sequentially performed is indicated by _l4 .

FIG. 11 is a block diagram showing the basic configuration of an embodiment of the present invention, and reference numerals 1 to 9 in the figure correspond to those in FIG. Reference numeral 10 denotes a post-correction value input section into which the post-correction values a and b are inputted, and numeral 11 denotes a post-correction vector generation section which receives the post-correction values a and b from the speed sensor 6 based on the post-correction values a and b. 12 is a trajectory data post-correction section which corrects the unit vector from the unit vector generator 5 in response to the clock pulse of Correction values Δx′ _i and Δy′ _i are calculated based on the traveling trajectory information stored in the traveling trajectory memory 8.
(according to equation (14)), Σx' _i and Σy' _i corresponding to each travel locus information are temporarily held, and the contents of the travel locus memory 8 are rewritten. The operation of the embodiment shown in FIG. 11 will be described below.

After a certain amount of travel trajectory information has been obtained, first, minute offset values a and b are input using the post-correction value input section 10. Based on these input values a and b, the trajectory data post-correction unit 12 uses the traveling trajectory information stored in the traveling trajectory memory 8 to calculate the correction values Δx' _i and Δy' _i according to the above-mentioned equation (14). .

Δx′ _i =1/Δl{a(Y _i −Y _i-1 ) ² −b(X _i −X _i-1 )(Y _i −Y _i-1 )} Δy′ _i =1/Δl{b( X _i −X _i-1 ) ² −a(X _i −X _i-1 )(Y _i −Y _i-1 )} Next, the traveling trajectory is calculated based on the above-mentioned equations (16) and (17). Add corrections to the information. That is, X′ _o =X _o − _o 〓 ⁱ⁼¹ Δx′ _i Y′ _o =Y _o − _o 〓 ⁱ⁼¹ Δy′ _i Finally, this obtained new trajectory information is stored in the traveling trajectory memory 8.

Here, the display unit 9 can display the travel trajectory based on the corrected trajectory information. By comparing the displayed travel trajectory with the road map, it can be determined whether the minute offset values a and b are appropriate. As a result, if the displayed travel trajectory does not correspond to the road map, the minute offset values a and b are input again and the correction calculation is repeated. In this way, the traveling trajectory information is corrected and the minute offset values a and b are determined. After comprehensively determining the deviation between the travel trajectory and the road map, minute offset values a and b are first assumed and set, and a corrected travel trajectory is obtained. If the corrected travel trajectory corresponds correctly to the road map, it is determined that the values a and b are desired values. If the correspondence is not correct, the above values a,
Re-enter b. In this way, desired values a and b are obtained by cut and try.
If the desired values a and b have been obtained, correction will be performed as described below, and the above correspondence will be correct from now on.

The corrected values X' _i and Y' _i of the latest trajectory information are stored in the integrator 7 in preparation for the next time the vehicle resumes running. Further, the minute offset values a and b are also sent to the post-correction vector generation section and used for correction calculations during running.

Post-correction during driving is performed using the above-mentioned equation (21). That is, X′ _i+1 = X′ _i +Δl(sinθ _i+1 −a cos ² θ _i+1 +b
sinθ _i+1・cosθ _i+1 ) X′ _i+1 =X′ _i +Δl(sinθ _i+1 −a cos ² θ _i+1 +b
sinθ _i+1・cosθ _i+1 ) Y′ _i+1 =Y′ _i +Δl(cosθ _i+1 −b sin ² θ _i+1 +a sin
θ _i+1・cos θ _i+1 ) Here, the expression in parentheses in Equation (21) is the unit vector after the post-correction. Therefore, each time a pulse from the speed sensor 6 is input, the post-correction vector generator 11 calculates (sinθ _i+1 −a cos ² θ _{i +1} +b sinθ _i+1・cosθ _i+1
)
and (cosθ _i+1 −b sin ² θ _i+1 +a sinθ _i+1・cosθ _i+1
), a corrected unit vector is generated and sent to the integrator 7. In the integrator 7, the coordinates are updated according to the above equation (21) and stored in the travel trajectory storage device. Using the above procedure, the minute offset values a,
The post-correction in b is completed, and it becomes possible to obtain highly accurate travel trajectory information.

As explained above, according to the present invention, after the initial correction of the magnetic azimuth sensor, it is possible to automatically and accurately correct small offset changes that occur during driving using driving trajectory information. Therefore, it is possible to provide a course guidance device that always displays an accurate travel trajectory and can perform an effective course guidance device.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a magnetic azimuth sensor used in a course guidance device, Fig. 2 is a block diagram showing the configuration of a conventional example of a course guidance device, and Fig. 3 is an explanatory diagram for explaining a traveling locus display mode in the course guidance device. FIGS. 4 and 5 are explanatory diagrams for explaining the necessity of offset correction for the output of the magnetic orientation sensor, and FIGS. 6 to 10 illustrate the basics of minute offset correction in the present invention. FIG. 11, which is an explanatory diagram for explaining the principle, is a block diagram showing the configuration of an embodiment of the course guiding device of the present invention. In the figure, 1 is a magnetic direction sensor, 2 is an A/D converter, 3 is an initial correction section, 4 is an angle conversion section, 5 is a unit vector generation section, 6 is a speed sensor, 7 is an integrator, and 8 is a travel trajectory memory , 9 is a display section, 10 is a post-correction value input section, 11 is a post-correction vector generation section, and 12 is a trajectory data post-correction section.

Claims (1)

[Claims] 1. A magnetic azimuth sensor that detects the geomagnetic azimuth and outputs traveling direction information of a moving object, and a speed sensor that outputs traveling distance information of a moving object, and is calculated based on the outputs of the magnetic azimuth sensor and speed sensor. The vehicle is equipped with a travel trajectory memory in which travel trajectory information is stored, and the contents of the travel trajectory memory are read out and the travel trajectory of the moving object is displayed in association with the road map on a display displaying the road map. In the course guiding device,
A post-correction value input section for inputting a small offset value for performing a small offset correction on the output of the magnetic orientation sensor; A trajectory data post-correction section that performs minute offset correction on the stored travel trajectory information, and a minute offset correction on the output of the magnetic azimuth sensor based on the minute offset value input from the post-correction value input section. and a post-correction vector generation unit that performs the correction and outputs it to the travel trajectory memory, and compares the travel trajectory displayed on the display with the road map based on the travel trajectory information obtained by the minute offset correction. 2. A course guidance device, characterized in that the minute offset value inputted in the post-correction value input section is adjusted so that a desired travel trajectory can be obtained by adjusting the course guidance device.