Automatic guided vehicle system and method

• US 8,676,426 B1
• Filed: 08/29/2012
• Issued: 03/18/2014
• Est. Priority Date: 08/29/2012
• Status: Active Grant

• Current Assignee: Jervis B Webb Company (Daifuku Company Limited)
• Original Assignee: Jervis B Webb Company (Daifuku Company Limited)
• Inventors: Murphy, Christopher John
• Primary Examiner(s): Black, Thomas
• Assistant Examiner(s): PAIGE, TYLER D
• Application Number:
  US13/597,535
• Publication Number:
  US 20140067184A1
• Time in Patent Office: 566 Days
• Field of Search: 701/23, 180/167, 180/168, 180/169, 318/587
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

An apparatus and method for guiding an automatic guided vehicle along a magnetic pathway and more specifically to an apparatus and a method capable of accurately and precisely following a weak magnetic field emitted by a substantially continuous passive magnetic marker having route junctions.

Claims

1. An automatic guided vehicle (AGV) configured to travel on a supporting surface and follow a pathway producing a magnetic field, said AGV comprising:

a support assembly having a plurality of wheels and wherein at least one of said plurality of wheels is configured to directionally steer the AGV;

a first magnetic sensor assembly coupled to said support assembly, said magnetic sensor assembly having a first magnetic field detector arranged adjacent to a second magnetic field detector and wherein said first magnetic field detector is configured to measure the strength of the magnetic field produced by the pathway along a first axis and output a first signal related to the magnetic field strength along said first axis of said first magnetic field detector and said second magnetic field detector is configured to measure the strength of a magnetic field along a second axis and output a second signal related to the magnetic field strength along said second axis and wherein said first axis of the first magnetic field detector is orthogonal to said second axis of the second magnetic field detector; and

a controller capable of receiving said first and second signals and based on said first and second signals, determining a steering signal to said at least one of said plurality of wheels configured to directionally steer the AGV;

wherein said first and second magnetic field detectors are located adjacent to each other on a single chip and approximately aligned with the supporting surface.

2. The AGV of claim 1 wherein at least one of said first axis and second axis is substantially perpendicular to the supporting surface and the other of said first axis and second axis is substantially parallel to the supporting surface.

3. The AGV of claim 2 wherein each of said first axis and said second axis are substantially located within a first plane that is located substantially perpendicular to the supporting surface.

4. The AGV of claim 3 wherein said first plane is substantially perpendicular to the pathway.

5. The AGV of claim 1 further including a second magnetic sensor assembly coupled to said support assembly and wherein said second magnetic sensor assembly includes a third magnetic field detector and a fourth magnetic field detector, each having an axis and wherein said axes of said third and fourth magnetic field detectors are orthogonal and located substantially within a second plane.

6. The AGV of claim 5 wherein each of said first axis and said second axis are substantially located within a first plane that is located substantially perpendicular to the supporting surface and wherein said second plane is approximately aligned with or within said first plane.

7. The AGV of claim 1 wherein said field detectors are selected from the group consisting of hall effect sensors and giant magnetoresistance sensors.

8. The AGV of claim 1 further including a second magnetic sensor assembly coupled to said support assembly and wherein said second magnetic sensor assembly includes a third magnetic field detector and a fourth magnetic field detector, each having an axis and wherein said axes of said third and fourth magnetic field detectors are orthogonal and located substantially within the second plane, and a third magnetic sensor assembly coupled to said support assembly and wherein said third magnetic sensor assembly includes a fifth magnetic field detector and a sixth magnetic field detector, each having an axis and wherein said axes of said fifth and sixth magnetic field detectors are orthogonal and located substantially within a third plane, and wherein the axes of said first, third and fifth field detectors are substantially aligned and wherein the axes of said second, fourth and sixth field detectors are spaced apart and substantially parallel.

9. The AGV of claim 8 wherein said first, second and third planes are substantially aligned or within the same plane.

10. A method of controlling an AGV, operating on a supporting surface, along a pathway producing a magnetic field and wherein said pathway is substantially continuous, said method comprising the steps of:

determining the strength of the magnetic field along a first axis;

determining the strength of the magnetic field along a second axis, wherein said second axis is orthogonal to said first axis;

calculating a first vector directed at the pathway using the determined strength of the magnetic field along the first axis and the determined strength of the magnetic field along the second axis;

calculating a second vector directed at the pathway using the determined strength of the magnetic field along the first axis and the determined strength of the magnetic field along the second axis;

determining a point of convergence of the first vector and the second vector; and

determining if the point of convergence of the first vector and the second vector is within a predetermined range of the supporting surface.

11. The method of claim 10 further including the step of comparing deviation of the angle of the calculated vector to a reference vector angle.

12. The method of claim 10 further including the steps of:

determining the strength of the magnetic field along a third axis;

determining the strength of the magnetic field along a fourth axis, wherein said fourth axis is orthogonal to said third axis;

calculating a second vector directed at the pathway using the determined strength of the magnetic field along the third axis and the determined strength of the magnetic field along the fourth axis.

13. The method of claim 10 further including the step of determining that the determined strength of the magnetic field along at least one of the first axis and the second axis exceeds a baseline strength.

14. The method of claim 10 further including the step of instructing the AGV to stop if the point of convergence is outside of the predetermined range of the supporting surface.

15. The method of claim 10 further including the step of correcting an actual travel path of the AGV to match a desired travel path aligned with the magnetic marker based on the direction of the first and second vectors.