Automatically guided vehicle control system

• US 4,678,329 A
• Filed: 10/18/1985
• Issued: 07/07/1987
• Est. Priority Date: 10/18/1985
• Status: Expired due to Fees

• Current Assignee: Calpine Corporation
• Original Assignee: Calpine Corporation
• Inventors: Lukowski, Frank J. Jr., Hammill, Harry B. III
• Primary Examiner(s): Buczinski, Stephen C.
• Assistant Examiner(s): Wallace, Linda J.
• Application Number:
  US06/789,280
• Time in Patent Office: 627 Days
• Field of Search: 356/152, 356/138, 356/400, 356/141, 244/171, 250/214 B, 358/95
• US Class Current: 356/152.2
• CPC Class Codes: B66F 9/0755 Position control; Position detectors
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G05B 2219/37555 Camera detects orientation, position workpiece, points of workpiece
• CPC Class Codes: G05B 2219/45049 Forklift
• CPC Class Codes: G05D 1/0225 involving docking at a fixed facility, e.g. base station or loading bay parking aids B62D15/027
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70

Abstract

A target member mounted on a stationary object, such as a pallet, includes at least three reflector elements. An identifying means, such as a high intensity light source, and an imaging sensor are carried by another, movable object, such as a forklift truck. The reflector elements are so configured as to form images of the identifying means with said images defining a plane oriented other than normal to align from the identifying means to that plane, the images also defining a circle that does not include the identifying means. The target member may be in the form of a vertically oriented planar support member on which are mounted a pair of convex mirrors and a concave mirror. The images of the identifying means in the mirrors are detected by an imaging sensor, such as a television camera, and the directions of each of the images at the camera are used to determine all six degrees of positional information of the sensor with respect to the target. That information may be used to guide the forklift truck into position relative to a pallet. The target support member includes retroreflector elements to aid in locating a pallet. Circuit means are provided to flash the light source and in response to the light returned by the retroreflectors to define an area on the image plane of the camera where reflections from the mirrors may be found. Ambient light images are then temporarily recorded, the light source again flashed, and the ambient images are electronically removed so that only those images due to reflections in the mirrors are finally recorded.

Claims

1. Apparatus for use in determining the relative location of a vehicle with respect to a target, including:

a light source and a camera mounted on the vehicle, said target including at least three reflector elements, each selected to form an image of the light source, and all the images together defining a plane oriented other than normal to a line from the light source to the target;

means for recording those images due to ambient light formed on the image plane of said camera;

means for thereafter flashing the light source;

means for comparing said images due to ambient light stored in said recording means and the images resulting both from ambient light and from the light source; and

means for recording those images formed on the image plane of said camera due only to reflections of said light source.

2. The apparatus of claim 1 further including:

retroreflective members mounted on said target and in a predetermined relation to said reflector elements;

means for initially flashing the light source;

means for sensing the reflections of the light source from the retroreflector members as they appear on the image plane of the camera; and

means responsive to the images of the retroreflectors for defining an area on the image plane of the camera where reflections from the reflector elements would be located.

3. A method for gathering information for determining the relative location of a target with respect to a vehicle wherein the vehicle is provided with a light source and a camera, and wherein the target is provided with at least three reflector elements, each selected to form an image of the light source, and all the images together defining a plane oriented other than normal to a line from the light source to the target, the method comprising the steps of:

(a) recording the images formed on the image plane of the camera due to ambient light;

(b) flashing the light source;

(c) comparing the images recorded in step (a) with the images resulting both from ambient light and from the light source thereby to isolate those reflections of the light source in the reflector elements;

(d) recording those images of the reflections due to the light source; and

(e) identifying the position of each such reflection of the light source from the reflector elements both on the image plane of the camera and with respect to each other.

4. A method for gathering information for determining the relative location of a target with respect to a vehicle, and wherein the vehicle is provided with a light source and a camera wherein the target is provided with at least three reflector elements, each selected to form an image of the light source and all the images together defining a plane oriented other than normal to a line from the light source to the target, and retroreflective members in a predetermined relation to the reflector elements, the method comprising the steps of:

(a) flashing the light source;

(b) recording the positions of the reflections of the light source from the retroreflector members are viewed by the camera;

(c) defining an area within the image plane of the camera where reflections for the reflector elements would be located by reference to the location of the light reflected by the retroreflector members;

(d) recording the images from the target within the defined area due to ambient light;

(e) flashing the light source a second time;

(f) recording the images within the defined area resulting from both ambient light and from the light source;

(g) comparing the images from step (d) with those from step (f) to isolate those reflections from the light source; and

(h) determining the position of each reflection of the light source from the reflector elements both on the image plane of the camera and with respect to each other.

5. The method of claim 4 wherein the images recorded in step (f) must be brighter than a predetermined level, and wherein the record of all reflections from the target from step (d) are compared with those reflections from the target recorded in step (f) that are brighter than the predetermined level in order to identify those reflections of the light source reflected only by the reflector elements.