System and method for laser-based auto-alignment

• US 9,221,137 B2
• Filed: 10/04/2013
• Issued: 12/29/2015
• Est. Priority Date: 10/05/2012
• Status: Active Grant

• Current Assignee: Beckman Coulter Incorporated (Danaher Corporation)
• Original Assignee: Beckman Coulter Incorporated (Danaher Corporation)
• Inventors: Otts, Stephen
• Primary Examiner(s): Amin, Bhavesh V
• Application Number:
  US14/046,868
• Publication Number:
  US 20140173870A1
• Time in Patent Office: 816 Days
• Field of Search: 294/071
• US Class Current: 1/1
• CPC Class Codes: B23P 19/04 for assembling or disassembling parts
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G05B 2219/40293 Gantry, portal
• CPC Class Codes: G05B 2219/40613 Camera, laser scanner on end effector, hand eye manipulator, local
• CPC Class Codes: Y10T 29/4978 Assisting assembly or disassembly
• CPC Class Codes: Y10T 29/53087 with signal, scale, illuminator, or optical viewer

Abstract

In a laser-based alignment system, a laser sensor tool, comprising a laser emitter and detector element can be gripped by a gripper unit of a robotic arm and used to automatically align the robotic arm with a work surface. A landmark on the work surface can be identified by scanning the work surface with the laser sensor in an X-Y plane. A center point of the landmark in the X-Y plane can be determined to align the gripper unit with the work surface in the X-Y plane. The robotic arm can be calibrated on a Z-axis by moving the gripper downward in a z-direction until the gripper unit contacts the work surface.

Claims

1. A method for auto-alignment, comprising:

gripping a laser sensor tool by a gripper unit of a robotic arm, wherein the laser sensor tool is configured to emit a laser pulse and receive a reflection of the laser pulse;

identifying a landmark on a work surface by scanning the work surface with the laser sensor tool in an X-Y plane;

determining a center point of the landmark in the X-Y plane to align the gripper unit with the work surface in the X-Y plane;

aligning the gripper unit with the work surface in the X-Y plane based on the determined center point of the landmark; and

calibrating the gripper unit on a Z-axis by moving the gripper downward in a z-direction until the gripper unit contacts the work surface.

2. The method of claim 1, wherein determining a center point of the landmark in the X-Y plane to align the gripper unit with the work surface in the X-Y plane further comprises:

scanning the landmark in a first direction to determine a first edge of the landmark and a second edge of the landmark based on reflections received by the laser sensor tool;

determining a first center point of the landmark on a first axis based on the first edge and the second edge;

scanning the landmark in a second direction, substantially orthogonal to the first direction, from the first center point of the landmark to determine a third edge and a fourth edge;

determining a second center point of the landmark on a second axis based on the third edge and fourth edge; and

repeating scanning the landmark until a plurality of center points are within a preset distance of each other.

3. The method of claim 1, further comprising:

after the center point of the landmark is determined, rotating the laser sensor tool 90 degrees relative to the laser sensor tool'"'"'s initial position in the gripper unit and determining a second center point of the landmark;

rotating the laser sensor tool 180 degrees relative the laser sensor tool'"'"'s initial position in the gripper unit and determining a third center point of the landmark;

rotating the laser sensor tool 270 degrees relative the laser sensor tool'"'"'s initial position in the gripper unit and determining a fourth center point of the landmark; and

determining an average center point of the landmark by averaging the center points.

4. The method of claim 1, wherein identifying a landmark on the work surface by scanning the work surface with the laser sensor tool in an X-Y plane further comprises:

moving the gripper unit in a programmed path in the X-Y plane;

emitting pulses from the laser sensor tool; and

recording reflections from the work surface, wherein the landmark is identified when a modified reflection is recorded.

5. The method of claim 2, wherein the landmark is a bore hole in the work surface.

6. The method of claim 2, wherein the landmark is an area of the work surface coated with a non-reflective coating.

7. The method of claim 1, further comprising:

storing the center point of the landmark; and

comparing the center point of the landmark with alignment data to identify locations of one or more elements on the work surface.

8. The method of claim 7, wherein the one or more elements on the work surface can include a drawer, a rack, or a tool.

9. The method of claim 1, wherein calibrating the gripper unit on a Z-axis by moving the gripper downward in a z-direction until the gripper unit contacts the work surface, further comprising:

releasing, by the gripper unit, the laser sensor tool;

gripping, by the gripper unit, a Z-calibration tool;

positioning the gripper unit at a first height over the work surface, and recording a first Z position;

lowering the gripper unit in the Z-direction until the Z-calibration tool makes contact with the work surface, and recording a second Z position; and

storing the first and second Z positions.

10. The method of claim 1, wherein the laser sensor tool includes a grippable housing including a groove or ledge.

11. An assembly, comprising:

a robotic arm, including a gripper unit configured to grip a laser sensor tool, wherein the robotic arm is configured to move in three dimensions over a work surface;

an auto-alignment system, including one or more controllers coupled to the robotic arm and laser sensor tool, wherein the auto-alignment system is configured to instruct the robotic arm to grip the laser sensor tool, wherein the laser sensor tool is configured to emit a laser pulse and receive a reflection, and to move the robotic arm over the work surface in an X-Y plane;

wherein the auto-alignment system is further configured to instruct the laser sensor tool to scan the work surface to identify a landmark, and determine a center point of the landmark in the X-Y plane to align the robotic arm with the work surface in the X-Y plane,

wherein the auto-alignment system is further configured to align the gripper unit with the work surface in the X-Y plane based on the determined center point of the landmark, and

wherein the auto-alignment system is further configured to calibrate the robotic arm on a Z-axis by moving the gripper downward in a z-direction until the gripper unit contacts the work surface, and storing a position of the robotic arm on the Z-axis when the gripper unit contacts the work surface.

12. The assembly of claim 11, wherein to determine a center point of the landmark in the X-Y plane, the auto-alignment system is configured to instruct the robotic arm and laser sensor tool to:

scan the landmark in a first direction to determine a first edge of the landmark and a second edge of the landmark based on reflections received by the laser sensor tool;

determine a first center point of the landmark on a first axis based on the first edge and the second edge;

scan the landmark in a second direction, orthogonal to the first direction, from the first center point of the landmark to determine a third edge and a fourth edge;

determine a second center point of the landmark on a second axis based on the third edge and fourth edge; and

repeat scanning the landmark until a plurality of center points are within a preset distance of each other.

13. The assembly of claim 11, wherein the auto-alignment system is further configured to instruct the robotic arm and laser sensor tool to:

after the center point of the landmark is determined, rotate the laser sensor tool 90 degrees relative the laser sensor tool'"'"'s initial position in the gripper unit and determine a second center point of the landmark;

rotate the laser sensor tool 180 degrees relative the laser sensor tool'"'"'s initial position in the gripper unit and determine a third center point of the landmark;

rotate the laser sensor tool 270 degrees relative the laser sensor tool'"'"'s initial position in the gripper unit and determine a fourth center point of the landmark; and

determine an average center point of the landmark by averaging the center points.

14. The assembly of claim 11, wherein to identify a landmark on the work surface by scanning the work surface with the laser sensor tool in an X-Y plane, the auto-alignment system is further configured to:

move the gripper unit in a programmed path in the X-Y plane;

emit pulses from the laser sensor tool; and

record reflections from the work surface, wherein the landmark is identified when a modified reflection is recorded.

15. The assembly of claim 13, wherein the landmark is a bore hole in the work surface.

16. The assembly of claim 13, wherein the landmark is an area of the work surface coated with a non-reflective coating.

17. The assembly of claim 11, wherein the auto-alignment system is further configured to:

store the center point of the landmark; and

compare the center point of the landmark with alignment data to identify locations of one or more elements on the work surface.

18. The assembly of claim 17, wherein the one or more elements on the work surface can include a drawer, a rack, or a tool.

19. The assembly of claim 11, wherein the laser sensor tool includes a grippable housing including a groove or ledge.

20. A method of identifying a center point of a landmark, comprising:

gripping a laser sensor tool by a gripper unit of a robotic arm, wherein the laser sensor tool is configured to emit a laser pulse and receive a reflection of the laser pulse;

identifying a first set of boundary points of a landmark in a first direction by scanning the work surface with the laser sensor tool;

determining a first midpoint of the landmark in the first direction based on the first set of boundary points;

identifying a second set of boundary points of the landmark in a second direction, substantially orthogonal to the first direction, wherein the second set of boundary points and the first midpoint are collinear;

determining a second midpoint of the landmark in the second direction based on the second set of boundary points; and

comparing a location of the first midpoint to a location of the second midpoint, and

if the location of the first midpoint is within a predetermined distance of the second midpoint, calculating an average location and storing the average location, wherein the average location corresponds to a center point of the landmark;

if the location of the first midpoint is not within the predetermined distance of the second midpoint, iteratively determining midpoints in alternating orthogonal directions, until locations of at least two midpoints are within the predetermined distance of each other.