Method for locating an object using a reference grid

• US 9,317,774 B2
• Filed: 08/22/2012
• Issued: 04/19/2016
• Est. Priority Date: 08/24/2011
• Status: Expired due to Fees

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Villien, Christophe
• Primary Examiner(s): Carter, Aaron W
• Application Number:
  US14/238,610
• Publication Number:
  US 20140211998A1
• Time in Patent Office: 1,336 Days
• Field of Search: None
• US Class Current: 1/1
• 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. 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, L_x, along the first direction and the horizontal lines being separated by a second distance, L_y, along the second direction, the method comprising, each time the object crosses at least one line of the grid:

determining a heading, φ

_i, of the object with respect to a reference direction;

obtaining, as a function of the determined heading, probabilities p(dy_i|φ

_i), p(dx_i|φ

_i), of the at least one line of the grid crossed by the object being respectively a horizontal line of the grid and a vertical line of the grid, when the object moves in the heading direction, φ

_i, where dy_i is a displacement of the object in the second direction, and dx_i is a displacement of the object in the first direction;

assessing, from the probabilities p(dy_i|φ

_i), p(dx_i|φ

_i), the first distance, L_x, and the second distance, L_y, a displacement, (,), of the object since a most recent time the object crossed the at least one line of the grid; and

updating a position, ({circumflex over (x)}_i, ŷ

_i), of the object in the reference grid from the assessed displacement, (,).

2. The locating method according to claim 1, wherein the first and second directions are orthogonal.

3. The locating method according to claim 1, wherein when the first direction is selected as the reference direction, the probability p(dx_i|φ

_i) of the at least one crossed line being a vertical line is determined by

4. The locating method according to claim 2, wherein, the first direction being selected as the reference direction, the displacement of the object is assessed by =sgn(cos φ

_i)p(dx₁|φ

_i)L_x and =sgn(sin φ

_i)p(dy_i|φ

_i)L_y where sgn(·

) is the signum function.

5. The locating method according to claim 4, wherein the position, ({circumflex over (x)}_i, ŷ

_i), of the object is updated according to {circumflex over (x)}_i=+ and ŷ

_i=+, 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.

6. The locating method according to claim 1, wherein the object includes a first sensor configured for detecting a line crossing of the grid.

7. The locating method according to claim 6, wherein the first sensor is an optical sensor.

8. The locating method according to claim 6, wherein the first sensor is an accelerometer.

9. The locating method according to claim 6, 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.

10. The locating method according to claim 9, wherein the second sensor is a magnetometer.

11. The locating method according to claim 10, wherein the second sensor is a gyroscope.

12. The locating method according to claim 9, 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.

13. The locating method according to claim 9, wherein the third sensor is a Doppler sensor.

14. The locating method according to claim 9, wherein the object includes wheels and the third sensor provides a direction of rotation of the wheels.

15. The locating method according to claim 1, wherein the object is a supermarket trolley.