Method and device for locating and guiding a mobile unit equipped with a linear camera

• US 6,654,482 B1
• Filed: 05/03/2000
• Issued: 11/25/2003
• Est. Priority Date: 11/04/1997
• Status: Expired due to Fees

• Current Assignee: Inria Institut National de Recherche EN Informatique et EN Automatique
• Original Assignee: Inria Institut National de Recherche EN Informatique et EN Automatique
• Inventors: Parent, Michel, Gualino, David
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Lu, Tom Y.
• Application Number:
  US09/530,655
• Time in Patent Office: 1,301 Days
• Field of Search: 382/104, 701/23, 701/207, 235/384, 348/148
• US Class Current: 382/104
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• CPC Class Codes: G05D 1/0246 using a video camera in combination with image processing means

Abstract

The method for locating a mobile unit relatively to an intermittent lighted beacon consists in calculating, on the basis of data concerning the mobile movement, the position of the discrete scatterer on the linear barrette obtained by a point by point subtraction of two linear images of the same image field, one wherein the beacon is alight and one wherein it is not alight, and the derivative of the position. On the basis of said data, the distance separating the beacon thus represented and a mark related to the mobile unit is calculated, and the beacon angular position relative to said mark linked with the mobile.

Claims

1. Method for locating a moving body equipped with a camera of the type comprising a linear array of photosensitive elements (CA), aimed in a known direction with respect to reference axes associated with the moving body, image processing means, and means (ODO) for capturing information relating to the movement of the moving body (M), characterized in that it involves the steps consisting in:

a) distributing in the zone in which the moving body moves, fixed beacons (B1, B2) which are intermittently illuminated either actively and/or passively,

b) at the moving body (M) and at a chosen rate, taking a pair of different linear images (IL1 and IL2) of the same image field, one of the images being one in which the beacon or beacons are illuminated, the other being one in which the beacon or beacons are not illuminated,

c) processing the pair of linear images by a point-by-point subtraction of one from the other,

d) obtaining at least one bright spot (P1) from the subtraction of the two linear images (IL1 and IL2), this spot representing at least one light beacon in the environment, and

e) calculating, on the basis of information relating to the movement of the moving body, the position (e) of the bright spot (P1) on the linear array, and its derivative, a first item of information relating to the distance (D1) separating the beacon thus represented (B1) and a frame of reference (A) associated with the moving body, and a second item of information relating to an angular position of the beacon with respect to said frame of reference associated with the moving body, thus making it possible, as a function of the first and second items of information thus calculated, to locate the moving body in relative terms with respect to said beacon.

2. Method according to claim 1, characterized in that step e) further comprises locating the moving body in absolute terms with respect to a fixed frame of reference defined using two separate beacons which can be seen simultaneously, said absolute location consisting in calculating, at a given instant, a relative location of the moving body with respect to each beacon, in calculating the heading of the moving body with respect to the two beacons, and in calculating the coordinates of a chosen point of the moving body with respect to said fixed frame of reference associated with the two beacons.

3. Method according to claim 1, characterized in that step e) further comprises locating the moving body in absolute terms with respect to a fixed frame of reference (R₀) associated with two beacons which can be seen at least in turn as the moving body moves along (B1, B2), said absolute location consisting in calculating, at a first given instant, a first relative location of the moving body with respect to the first beacon, in calculating, at a second given instant, after the first instant, a second relative location of the moving body with respect to the second beacon which follows the first, in using odometry to calculate the movement of the moving body and the heading of the moving body with respect to said first and second beacons and in calculating the coordinates of a chosen point (A2) of the moving body with respect to said fixed frame of reference (R₀).

4. A method according to claim 1, in which a number of beacons (B1, B2, . . . ) are distributed along the roadway (CH) to define a reference path, and the method further comprises a step

f) which consists in determining said reference path using the relative and/or absolute location of the moving body with respect to said beacons, and in guiding the moving body, keeping a certain distance between the moving body and said reference path.

5. Device for locating a moving body equipped with a camera (CA) of the type comprising a linear array of photosensitive elements aimed in a known direction with respect to reference axes associated with the moving body, image processing means and means (ODO) for capturing information relating to the movement of the moving body,

characterized in that it comprises fixed beacons which are intermittently illuminated either actively and/or passively, and distributed in the zone in which the moving body moves,

in that the linear camera (CA) is capable, at a chosen rate, of taking a pair of different linear images (IL1 and IL2) of the same image field, one of the images being one in which the beacon or beacons are illuminated, the other being one in which the beacon or beacons are not illuminated,

in that the image processing means are capable of processing the pair of linear images to perform a point-by-point subtraction of one from the other and obtaining at least one bright spot (P1) from the subtraction of the two linear images, this spot representing at least one beacon in the environment,

in that the moving body comprises calculation means capable of calculating, on the basis of information relating to the movement of the moving body, the position (e) of the bright spot (P1) on the linear array, and its derivative, a first item of information relating to the distance (D1) separating the beacon thus represented and a frame of reference (A) associated with the moving body, and a second item of information relating to an angular position of the beacon with respect to said frame of reference associated with the moving body, thus making it possible to locate the moving body in relative terms with respect to said beacon.

6. Device according to claim 5, characterized in that the calculation means are capable of locating the moving body in absolute terms with respect to a fixed frame of reference defined using two separate beacons (B1 and B2) which can be seen simultaneously, said calculation means being capable of calculating, at a given instant, a relative location with respect to each beacon, the heading of the moving body with respect to said beacons (B1 and B2) and the coordinates of a chosen point of the moving body with respect to said fixed frame of reference associated with said two beacons.

7. Device according to claim 5, characterized in that the calculation means are capable of locating the moving body in absolute terms with respect to two beacons which can be seen at least in turn as the moving body moves along, said calculation means being capable of calculating, at a first given instant, a first relative location of the moving body with respect to the first beacon, of calculating, at a second given instant, after the first instant, a second relative location of the moving body with respect to the second beacon which follows the first, of using odometry to calculate the movement of the moving body and the heading of the moving body with respect to said first and second beacons and of calculating the coordinates of a chosen point (A2) of the moving body with respect to said fixed frame of reference (R₀).

8. Device according to claim 5, in which a number of beacons are distributed along the roadway (CH) to define a reference path, the device being characterized in that the calculation means are capable of determining said reference path using the relative and/or absolute location of the moving body with respect to said beacons, and of guiding the moving body, keeping a certain distance between the moving body and said reference path.

9. Device according to claim 5, in which the light beacons (B1, B2) are of the retroreflective type, characterized in that the moving body further comprises a flash capable of intermittently passively illuminating said light beacons, the flash and the camera being controlled synchronously.

10. Device according to claim 9, characterized in that the flash (FH) comprises a support (10) aimed in the same direction as the camera, equipped with an opening (12) through which the light radiation passes to reach the camera and on the periphery of which there are a number of light-emitting diodes (EL).

11. Device according to claim 10, characterized in that the support (10) for the flash is of concave overall shape.

12. Device according to claim 9, in which the beacons are passively illuminated, characterized in that the moving body comprises synchronization means capable of bringing the camera acquisition signal into phase with the light signal from the flash.

13. Device according to claim 5, in which the beacons are actively illuminated, characterized in that the moving body comprises synchronization means capable of bringing the camera acquisition signal into phase with the light signal from the beacons.