Method and apparatus for determining position and rotational orientation of an object

• US 7,845,560 B2
• Filed: 12/03/2005
• Issued: 12/07/2010
• Est. Priority Date: 12/14/2004
• Status: Active Grant

• Current Assignee: Shenzhen Invention Discovery Company Limited
• Original Assignee: Sky-Trax Incorporated (TotalTrax, Inc.)
• Inventors: Mahan, Larry G., Ungerbuehler, Richard H., Emanuel, David C.
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US11/292,463
• Publication Number:
  US 20060184013A1
• Time in Patent Office: 1,830 Days
• Field of Search: 23546201-46245, 235/472.01, 235/472.02, 235/472.03
• US Class Current: 235/462.08
• CPC Class Codes: B66F 9/0755 Position control; Position detectors
• CPC Class Codes: B66F 9/24 Electrical devices or systems
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70

Abstract

A method and apparatus for determining position and rotational orientation of an object within a predetermined area is disclosed. Position markers, encoded with their identity, are viewed with a camera, images are captured and processed, and the position and rotational orientation of the object are calculated. Three embodiments are disclosed; the first having a camera mounted on the movable object while position markers bearing linear bar codes are fixed in location, the second having a camera mounted on the movable object while position markers bearing two-dimensional bar codes are fixed in location, and the third having a position marker of either type affixed to the object while the camera is fixed in location.

Claims

1. A method of determining the position and the rotational orientation of an object within a predefined coordinate space, the method comprising:

a) providing a plurality of unique position markers having identifying indicia and positional reference indicia thereupon, the markers being arranged at predetermined known positional locations within the coordinate space so that at least one position marker is within view of the object;

b) using an image acquisition system mounted on the object, acquiring an image of the at least one position marker within view;

c) processing the image to determine the identity, the position relative to the object, and the rotational orientation relative to the object of each position marker within view; and

d) calculating the position of the object and the rotational orientation of the object in the coordinate space and storing the position and rotational orientation information in a memory.

2. The method of claim 1, further comprising first identifying each position marker and calculating the actual position and the rotational orientation of the object in the coordinate space from the position reference indicia of the position marker and from the corresponding known location and angular orientation of the identified position marker.

3. The method of claim 2, further comprising the step of translating the information encoded in each position marker within view to a coordinate location of the position marker within view to a coordinate location of the position marker and then calculating the coordinate location of the object within the predefined coordinate space.

4. The method o f claim 2, further comprising the step of translating the information encoded in the position marker within the field of view to determine a rotational orientation of the marker within the field of view to determine a rotational orientation of the marker and then calculating the rotational orientation of the object.

5. The method of claim 1, wherein the processing of the acquired image in step c) comprises decoding a barcode, and wherein the decoded data identifies the position marker, the position coordinates and the rotational orientation of the position marker within the predefined coordinate space.

6. the method of claim 1, further comprising, after step d), combining the position an rotational orientation data into a single numerical sequence and then transmitting the position and rotational orientation information to a navigation system or to an inventory management system.

7. The method of claim 1, further comprising, maintaining a look-up-table containing actual X, Y, and Z coordinates and rotational orientation of all position markers within the coordinate reference.

8. The method of claim 7, further comprising determining an approximate position of the marker from said look-up-table.

9. The method of claim 1, wherein step d) comprises:

a) identifying two key points in the position marker;

b) defining a line between the two points;

c) calculating the length of the line; and

d) determining the center of the line to define the center of the position marker.

10. The method of claim 9, further comprising

a) determining a vector from the center of the field of view to the center of the position marker;

b) determining a length and angle of this vector relative to the field of view by plane geometry; and

c) calculating an adjusted position of the object by correcting the approximate position of the object by using the length and angle of the vector to calculate a position offset.

11. The method of claim 10 wherein the adjusted position of the object is corrected to a true position by applying small variations for said marker recorded in the look-up table.

12. The method of claim 9, further comprising determining an approximate rotational orientation by locating the line between the two key points and calculating its approximate angle of rotation relative to the field of view;

and wherein a correction is made to the approximate rotational orientation angle by retrieving stored rotational orientation data for the decoded position marker form the look-up table and adjusting the rotational orientation accordingly.

13. The method of claim 1, further comprising encoding the identity of each position marker'"'"'s identity in digital form using:

a) a linear one-dimensional barcode symbology consisting of Interleaved 2 of 5 code, Code 39, Code 128, Code 93, UPC code or Codabar;

or

b) a two-dimensional barcode consisting of DataMatrix, Code One, PDF417, Array Tag, or QR Code.

14. A method of determining a coordinate position and rotational orientation of an object within a predefined coordinate space, the method comprising:

a) providing a marker mounted on the object;

b) arranging a camera or plurality of cameras of an image acquisition system at predetermined known positional locations within the coordinate space, so that all portions of the coordinate space are within view of at least one camera;

c) acquiring an image of the marker with at least one camera;

d) processing the image to determine the identity, the position relative to the camera, and the rotational orientation relative to the camera of the marker; and

e) calculating the position of the object and the rotational orientation of the object in the coordinate space and storing the position and rotational orientation information in a memory.

15. An apparatus useful for determining a coordinate position and rotational orientation of an object within a predefined coordinate space, the apparatus comprising:

a) a plurality of unique position markers arranged in predetermined positional locations within the coordinate space such that at least one position marker is within view of the object and each position marker comprising a machine-readable code;

b) an image acquisition system, comprised of a machine vision system, the machine vision system comprising a camera, a light source, and image capture electronics, mounted on the object, for acquiring an image of the position markers within view;

c) an image processing system for processing pixels in the acquired image to determine the identity of each position marker, the position of each position marker relative to the object, the rotational orientation of each position marker relative to the object, the rotational orientation of each position marker relative to the object; and

d) a post processing system for calculating the position of the object and the rotational orientation of the object in the coordinate space.

16. The apparatus of claim 15, wherein the position markers are arranged in a pattern corresponding to a predetermined mapping of the predefined coordinate space and wherein the position markers are positioned on a support structure comprised of a grid of support material, said material being substantially transparent and permeable to air, the support structure being in a predetermined positional relationship with the predefined coordinate space.

17. The apparatus of claim 16, the support structure comprising a web, a mesh, a screen or a net.

18. The apparatus of claim 16, wherein the position marker further comprises human readable text indicating the relative position and/or unique identification of the position marker within the predefined coordinate space.

19. The apparatus of claim 16, wherein the position marker comprises geometric symbols place in a predetermined pattern and rotational orientation.

20. The apparatus of claim 16, wherein the position marker further comprises a linear or matrix bar code encoded with marker identification and relative portion and angular orientation of the marker within the predefined coordinate space.