System and method for displaying present position for moving object

• US 4,970,652 A
• Filed: 06/16/1989
• Issued: 11/13/1990
• Est. Priority Date: 06/16/1988
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Nagashima, Yoshimasa
• Primary Examiner(s): Black, Thomas G.
• Application Number:
  US07/366,995
• Time in Patent Office: 515 Days
• Field of Search: 364/449, 364/443, 364/424.01, 340/990, 340/995, 342/64, 382/48, 382/49
• US Class Current: 701/208
• CPC Class Codes: G01C 21/30 Map- or contour-matching

Abstract

A system and method for displaying a present position of a moving object on a road are disclosed in which a road map information surrounding the present position of the moving object is displayed together with the present position of the moving object and the present position of the vehicle which is derived on the basis of output signals of a running distance sensor and running direction sensor is automatically corrected through a pattern recognition between a form of a road on which the vehicle has travelled and a form of a running locus of the moving object.

Claims

1. A system for displaying a present position of a moving object, comprising:

(a) first means for detecting a running distance of the moving object;

(b) second means for detecting a running direction of the moving object;

(c) third means for initially setting the present position of the moving object;

(d) fourth means for deriving movement components in a horizontal direction per unit run distance and in a vertical direction per unit run distance when the moving object has moved on the basis of the unit run distance and running direction of the moving object derived from the first and second means;

(e) fifth means for accumulating respective movement components derived by the fourth means with an initially set position of the moving object derived by the third means as a start point to derive the present position of the moving object;

(f) sixth means for storing a locus data having the respective movement components in the horizontal and vertical directions per unit run distance derived by the fourth means;

(g) seventh means for storing a road map information;

(h) eighth means for selecting a road map information peripheral to the present position from the stored road map information of the seventh means;

(i) ninth means for storing a display information to superpose and display the present position of the moving object on the road map information selected by the eighth means;

(j) tenth means for displaying the contents of the ninth means on a screen thereof;

(k) eleventh means for executing a pattern recognition between a road form based on the road map and a running locus form of the moving object based on the locus data; and

(l) twelfth means for automatically correcting the present position of the moving object when a degree of coincidence between both patterns of the road form and locus form are relatively high.

2. A system as set forth in claim 1, wherein the eleventh means selects the locus form to be subjected to the pattern recognition in such a way that minor totals of the movement components stored in the sixth means for each unit distance (Δ

l₁) are discretely selected whenever at least one of the movement components in the horizontal and vertical directions exceeds another unit run direction (Δ

l₂ ;

Δ

l₂ >

Δ

l₁).

3. A system as set forth in claim 2, wherein the ninth means includes a V-RAM (Video Random Access Memory) in which the road form is depicted and wherein the eleventh means selects an end point of the road form to be subjected to the pattern recognition in such a way as to search in a spiral form a block with the present position of the moving object when a coordinate transform is executed on the V-RAM in which the road form is depicted.

4. A system as set forth in claim 3, wherein the eleventh means changes stepwise a width of an area (matching area) in which the block is spirally searched through a function having parameters of a running distance from a previously position corrected present position, the degree of coincidence when the pattern recognition is previously executed, and a probability density of the previously position corrected present position.

5. A system as set forth in claim 4, wherein the eleventh means deletes one of the two selected road points whose mutual distance is below a predetermined value l₃ (Δ

l₁ <

l₃ <

Δ

l₂) and sorts the respective road points in an order such that a road point which is nearest to the present position is the first.

6. A system as set forth in claim 5, wherein the eleventh means superposes and relax the discrete locus data in an order from a road point derived in the claim 5 with a predetermined allowance value so as to extract the corresponding point of road.

7. A system as set forth in claim 6, wherein when all prescribed numbers (N) of points from the present position correspond to the points of road, the eleventh means determines an end point of the road as a point of candidate for the correction of the present position.

8. A system as set forth in claim 7, wherein when the points which do not correspond to the locus data and road data are n number (n<

N), the eleventh means determines an end point of the road as the point of candidate for the correction of the present position.

9. A system as set forth in claim 8, wherein the eleventh means calculates a sum of residual square (E) from the road data on the point of candidate and the corresponding locus data before subjected to the relaxation, determines whether E is below Tl (threshold), and determines the end point of the road as being a promising point of candidate.

10. A system as set forth in claim 9, wherein the eleventh means rotates the locus data with the present position as a center through each unit angle (Δ

θ

_i), derives a minimum value (Emin) of a sum of residual square for each rotation angle, determines whether Emin is below the threshold (Tl), and determines the rotated locus data as the promising point of candidate when this value Emin is below the threshold and determines this value Emin as the degree of coincidence at the promising point of candidate.

11. A system as set forth in claim 10, the angle of rotation of the locus data is within the allowance limit value (±

Δ

θ

₂).

12. A system as set forth in claim 11, wherein the twelfth means includes:

(a) thirteenth means for deriving a standard deviation (σ

) and correlative coefficient γ

on the basis of a set of the promising points of candidates;

(b) fourteenth means for correcting the present position to one promising point of candidate which provides a minimum of the sum of residual square (E) when the standard deviation (σ

) is below a constant (σ

_c);

(c) fifteenth means for correcting the present position to one promising point of candidate in which an absolute value (l_m =|l_m1 -l_m2 |) of a difference between a distance (l_m1) from the previously corrected position to the present position of the vehicle and a distance from the previously corrected position to the promising point of candidate (l_m2) becomes minimum when the standard deviation is equal to or above the constant (σ

≧

σ

_c) and correlative coefficient γ

>

γ

_c (constant); and

(d) sixteenth means for inhibiting the correction of the present position when either σ

≧

σ

_c and γ

≦

γ

_c, or σ

<

σ

_c and γ

>

γ

_c.

13. A system as set forth in claim 1, which further comprises thirteenth means for manually correcting the present position of the vehicle when the present position is placed on a position except the road map information.

14. A system for displaying a present position of a moving object, comprising:

(a) first means for detecting a running distance of the moving object;

(b) second means for detecting a running direction of the moving object;

(c) third means for initially setting the present position of the moving object;

(d) fourth means for deriving movement components in a horizontal direction per unit run distance and in a vertical direction per unit run distance when the moving object has moved on the basis of the unit run distance and running direction of the moving object derived from the first and second means;

(e) fifth means for accumulating respective movement components derived by the fourth means with an initially set position of the moving object derived by the third means as a start point to derive the present position of the moving object;

(f) sixth means for storing a locus data having the respective movement components in the horizontal and vertical directions per unit run distance derived by the fourth means;

(g) seventh means for storing a road map information;

(h) eighth means for selecting a road map information peripheral to the present position from the stored road map information of the seventh means;

(i) ninth means for storing a display information to superpose and display the present position of the moving object on the road map information selected by the eighth means;

(j) tenth means for displaying the contents of the ninth means on a screen thereof;

(k) eleventh means for executing a pattern recognition between a road form based on the road map and a running locus form of the moving object based on the locus data; and

(l) twelfth means for automatically correcting the present position of the moving object according to a result of the pattern recognition executed by the eleventh means.

15. A system as set forth in claim 14, wherein the third means comprises a series of keys on a keyboard for inputting an initial position of the moving object as the present position of the vehicle.

16. A system as set forth in claim 14, wherein the sixth means derives and stores a required number of minor totals of the movement components in the horizontal and vertical directions with respect to the road map information displayed on the tenth means as the locus data of the moving object when the movement components of the moving object in either the horizontal or vertical direction exceeds another unit of run distance.

17. A system as set forth in claim 16, wherein the eighth means comprises:

(a) thirteenth means for searching spirally points of candidate for the present position of the moving object on any one of roads peripheral to the present position of the moving object;

(b) fourteenth means for deleting at least one of the two points of candidate which are placed on a peripheral road and whose mutual interval distance is too short;

(c) fifteenth means for sorting the points of candidate in an order such that one of the points of candidate for the present position which is nearest to the present position is the first; and

(d) sixteenth means for overlapping the locus data on the road form for each point of candidate and selecting one point of candidate at which the overlapping can be achieved through a relaxation method within an allowance limit as one promising point of candidate.

18. A systemm as set forth in claim 17, wherein the eleventh means carries out a rotation of the locus with the promising point of candidate as a center, derives an error value between each promising candidate and a corresponding point on the peripheral road, and determines whether one of each promising point of candidate which provides the error value which is below a threshold is present.

19. A system as set forth in claim 18, wherein the eleventh means calculates a standard deviation and correlative coefficient of the promising point of candidate which provides the error value which is below the threshold and wherein the twelfth means corrects the present position of the vehicle on the basis of the result of the calculation of the standard deviation and correlative coefficient by the eleventh means.

20. A system as set forth in claim 14, wherein the seventh means comprises a CD (Comapct Disc) - ROM.

21. A system as set forth in claim 14, wherein the ninth means comprises a V-RAM.

22. A method for displaying a present position of a moving object, comprising the steps of:

(a) detecting a running distance of the moving object;

(b) detecting a running direction of the moving object;

(c) setting an initial present position of the moving object;

(d) deriving movement components in a horizontal direction per unit run distance and in a vertical direction per unit run distance when the moving object has moved on the basis of the unit run distance and running direction of the moving object derived in the steps (a) and (b);

(e) accumulating respective movement components derived in the step (d) with an initially set position of the moving object derived in the step (c) as a start point to derive the present position of the moving object;

(f) storing a locus data having the respective movement components in the horizontal and vertical directions per unit run distance derived in the step (d);

(g) storing a road map information;

(h) selecting a road map information peripheral to the present position from the stored road map information;

(i) storing a display information to superpose and display the present position of the moving object on the road map information selected in the step (h);

(j) displaying the stored contents in the step (i) on a screen thereof;

(k) executing a pattern recognition between a road form based on the road map and a running locus form of the moving object based on the locus data; and

(l) automatically correcting the present position of the moving object according to a result of the pattern recognition executed the step (k).