Vision based precision docking of vehicles

• US 6,078,849 A
• Filed: 12/11/1998
• Issued: 06/20/2000
• Est. Priority Date: 12/11/1998
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Brady, Daniel G., Sobetski, Jerome F., Kennedy, William A, Hougen, Darrell R.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/209,489
• Time in Patent Office: 557 Days
• Field of Search: 701/23, 701/28, 701/200, 701/301, 701/3, 701/93, 701/96, 701/1, 180/167, 180/168, 180/169, 342/350, 342/455, 342/457, 342/458, 318/587
• US Class Current: 701/28
• CPC Class Codes: B60T 7/22 initiated by contact of vehicle, e.g. bumper, with an external object, e.g. another vehicle , or by means of contactless obstacle detectors mounted on the vehicle
• 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
• CPC Class Codes: G05D 1/0255 using acoustic signals, e.g. ultra-sonic singals sonar systems designed for anti-collision purposes G01S15/93
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00

Abstract

A three phase control arrangement is employed after visual detection of a target at greater range than otherwise available. The first and last phases employ an optimization criterion for which errors do not vary with distance from a target; limiting the initial error and process error in an intermediate phase which controls approach trajectory to the intended docking location and yielding repeatable high accuracy docking. The three phase approach with different control criteria and control gain parameters makes feasible a docking maneuver that begins at a much greater range and potentially greater lateral separation from the destination than would otherwise be possible, while providing control of both the final location and final orientation of the vehicle. A preferred visual thresholding technique provides consistency of results over a wide range of illumination and contrast conditions while limiting the computation burden for target image acquisition and tracking.

Claims

1. A method of vision based automated vehicle guidance to a location comprising the steps of

approximating distance to a visual target detected by a camera located on a vehicle,

a first phase between a first distance and a second distance from said target, minimizing an angle between vehicle trajectory and a direction toward said visual target,

a second phase between said second distance and a third distance from said target, minimizing an angle between a desired direction and a location of said vehicle relative to said visual target, and

a third phase between said third distance from said target and said location, minimizing an angle between vehicle trajectory and a direction toward said visual target.

2. A method as recited in claim 1, including the step of providing a first control gain during said first phase.

3. A method as recited in claim 2, including the further step of providing a second control gain, different from said first control gain during said second phase.

4. A method as recited in claim 3, wherein said second control gain is greater than said first control gain.

5. A method as recited in claim 3, including the further step of providing a third control gain, different from said second control gain during said third phase.

6. A method as recited in claim 5, wherein said third control gain is greater than said second control gain.

7. A method as recited in claim 1, wherein each of said first, second and third phases provide guidance control which is proportional to a weighted sum of a deviation angle and a rate of change of said deviation angle.

8. A method as recited in claim 1, wherein said step of approximating a distance includes the step of detecting a first visual target and a second visual target.

9. A method as recited in claim 8, wherein said second visual target is vertically displaced from said first visual target.

10. A method as recited in claim 8, wherein said second phase includes the step of detecting a third visual target.

11. A method as recited in claim 10, wherein said third visual target is horizontally displaced from said first visual target.

12. A method as recited in claim 11, wherein a location of said third visual target defines an approach angle of said vehicle to said location.