METHOD FOR LOCATING AN OBJECT USING A REFERENCE GRID

• US 20140211998A1
• Filed: 08/22/2012
• Published: 07/31/2014
• Est. Priority Date: 08/24/2011
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Villien, Christophe
• Granted Patent: US 9,317,774 B2
• Time in Patent Office: Days
• US Class Current: 382/103
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

A method for locating an object by a reference grid, the object moving in a plane parallel to or identical to that of the grid. When crossing of a line of the grid is detected by the object, its heading is determined and, as a function of the detection, probabilities of the thus crossed line being a horizontal line and a vertical line respectively are obtained. Displacement of the object is assessed from the probabilities obtained and a horizontal and vertical pitch of the grid. A position of the object is then updated from a position of the object determined during a last line crossing of the grid and the displacement thus assessed.

Claims

1-15. -15. (canceled)

16. A method for locating an object by a reference grid, the object moving in a plane parallel to or identical to that of the grid, the grid being defined by a plurality of horizontal lines, aligned along a first direction, and a plurality of vertical lines, aligned along a second direction distinct from the first direction, the vertical lines being separated by a first distance along the first direction and the horizontal lines being separated by a second distance along the second direction, the method comprising, each time the object crosses a line of the grid:

determining a heading of the object with respect to a reference direction;

obtaining, as a function of the heading thus determined, probabilities p(dy₁/φ

₁), p(dx₁/φ

₁) of the line thus crossed being respectively a horizontal line and a vertical line of the grid, when the object moves in the direction given by the course;

assessing, from the probabilities and the first and second distances, displacement (, ) of the object since a last time the object crossed the line of the grid;

updating a position of the object from the assessed displacement.

17. The locating method according to claim 16, wherein the first and second directions are orthogonal.

19. The locating method according to claim 17, wherein, the first direction being selected as the reference direction, the displacement of the object is assessed by =sgn(cos φ

_i)p(dx_i|φ

_i)L_x and =sgn(sin φ

_i)p(dy_i|φ

_i)L_y where sgn( ) is the signum function and φ

₁ is the heading.

20. The locating method according to claim 19, wherein the position ({circumflex over (x)}₁, ŷ

₁) of the object is updated according to =+ and =+, where (, ) is the position of the object obtained the last time the object crossed a line of the grid and (, ) is the displacement assessed since the last time.

21. The locating method according to claim 16, wherein the object includes a first sensor configured for detecting a line crossing of the grid.

22. The locating method according to claim 21, wherein the first sensor is an optical sensor.

23. The locating method according to claim 21, wherein the first sensor is an accelerometer.

24. The locating method according to claim 21, wherein the object includes heading measuring means comprising a second sensor configured to provide orientation of the object and a third sensor configured to give a direction of its movement.

25. The locating method according to claim 24, wherein the second sensor is a magnetometer.

26. The locating method according to claim 28, wherein the second sensor is a gyroscope.

27. The locating method according to claim 24, wherein the third sensor is of same type as the first sensor and is provided on the object in proximity of the first sensor, an order of detecting the line crossing by the first and third sensors providing the direction of movement.

28. The locating method according to claim 24, wherein the third sensor is a Doppler sensor.

29. The locating method according to claim 24, wherein the object includes wheels and the third sensor provides a direction of rotation of the wheels.

30. The locating method according to claim 16, wherein the object is a supermarket trolley.