Operating a Mobile Robot

• US 20120185096A1
• Filed: 02/22/2011
• Published: 07/19/2012
• Est. Priority Date: 05/20/2010
• Status: Active Grant

• Current Assignee: Ava Robotics, Inc.
• Original Assignee: iRobot Corporation
• Inventors: Rosenstein, Michael, Shamlian, Steven V., Won, Chikyung, Halloran, Michael, Chiappetta, Mark, Allen, Thomas P.
• Granted Patent: US 8,935,005 B2
• Time in Patent Office: Days
• US Class Current: 700/259
• CPC Class Codes: B25J 11/009 Nursing, e.g. carrying sick persons, pushing wheelchairs, distributing drugs
• CPC Class Codes: B25J 5/007 mounted on wheels
• CPC Class Codes: G05D 1/0227 using mechanical sensing means, e.g. for sensing treated area
• CPC Class Codes: G05D 1/024 in combination with a laser lasers per se H01S
• CPC Class Codes: G05D 1/0242 using non-visible light signals, e.g. IR or UV signals
• CPC Class Codes: G05D 1/0246 using a video camera in combination with image processing means
• 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 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• 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
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

A method of operating a mobile robot to traverse a threshold includes detecting a threshold proximate the robot. The robot includes a holonomic drive system having first, second, and third drive elements configured to maneuver the robot omni-directionally. The method further includes moving the first drive element onto the threshold from a first side and moving the second drive element onto the threshold to place both the first and second drive elements on the threshold. The method includes moving the first drive element off a second side of the threshold, opposite to the first side of the threshold, and moving the third drive element onto the threshold, placing both the second and third drive elements on the threshold. The method includes moving both the second and third drive elements off the second side of the threshold.

Claims

1. A method of operating a mobile robot to traverse a threshold, the method comprising:

detecting a threshold proximate the robot, the robot comprising a holonomic drive system having first, second, and third drive elements configured to maneuver the robot omni-directionally;

moving the first drive element onto the threshold from a first side;

moving the second drive element onto the threshold to place both the first and second drive elements on the threshold;

moving the first drive element off a second side of the threshold, opposite to the first side of the threshold;

moving the third drive element onto the threshold, placing both the second and third drive elements on the threshold; and

moving both the second and third drive elements off the second side of the threshold.

2. The method of claim 1, further comprising determining an elevation change associated with the threshold and continuing to traverse the threshold when the elevation change is within a threshold elevation range.

3. The method of claim 2, wherein the threshold elevation range prevents high centering of the robot.

4. The method of claim 2, wherein the threshold elevation range is less than a radius of the drive elements.

5. The method of claim 1, further comprising maneuvering the first and second drive elements to approach a first side of the threshold at least substantially equidistantly before moving the first drive element onto the threshold.

6. The method of claim 1, further comprising pivoting about the second drive element to move the first drive element onto the threshold.

7. The method of claim 1, further comprising holding the first drive element stationary while moving the second drive element onto the threshold to place both the first and second drive elements on the threshold.

8. The method of claim 1, further comprising holding the second drive element stationary while moving the first drive element off the second side of the threshold.

9. The method of claim 1, further comprising continuing to pivot the robot about the second drive element after moving the first drive element off the second side of the threshold to move the third drive element onto the threshold.

10. The method of claim 1, further comprising moving both the second and third drive elements off the second side of the threshold at substantially the same time.

11. The method of claim 1, further comprising moving the first and second drive elements off the threshold at the same time, pulling the third drive element over the threshold.

12. The method of claim 1, wherein the holonomic drive system comprises first, second, and third drive wheels, each drive wheel trilaterally spaced about a vertical center axis and having a drive direction perpendicular to a radial axis with respect to the vertical center axis.

13. The method of claim 1, wherein the holonomic drive system comprises first, second, and third drive balls, each drive ball trilaterally spaced about a vertical center axis.

14. The method of claim 1, wherein the holonomic drive system comprises first, second, and third drive ball assemblies, each drive ball assembly comprising:

a drive ball;

a transmission rollers in continuous contact with the respective drive ball, the transmission roller actively rotating about a first axis and passively rotating about a second axis; and

a drive mechanism rotating the transmission roller to rotate the drive ball.

15. A mobile robot comprising:

a holonomic drive system having first, second, and third drive elements configured to maneuver the robot omni-directionally; and

a controller in communication with the drive system, upon detecting a threshold proximate the robot, the controller issuing commands to the drive system to;

move the first drive element onto the threshold from a first side;

move the second drive element onto the threshold to place both the first and second drive elements on the threshold;

move the first drive element off a second side of the threshold, opposite to the first side of the threshold;

move the third drive element onto the threshold, placing both the second and third drive elements on the threshold; and

move both the second and third drive elements off the second side of the threshold.

16. The mobile robot of claim 15, further comprising:

a base supporting the drive system;

a leg extending upward from the base and having a variable height;

a torso supported by the leg, the torso defining a shoulder having a bottom surface overhanging the base; and

a torso imaging sensor disposed on the bottom surface of the torso and pointing downward along a forward drive direction of the drive system, the torso imaging sensor capturing three-dimensional images of a scene about the robot.

17. The mobile robot of claim 16, wherein the torso imaging sensor is recessed within a body of the torso while maintaining its downward field of view.

18. The mobile robot of claim 15, further comprising a volumetric point cloud imaging device in communication with the controller and capable of obtaining a point cloud from a volume of space adjacent the robot.

19. The mobile robot of claim 18, wherein the volumetric point cloud imaging device scans side-to-side with respect to the forward drive direction to increase a lateral field of view of the volumetric point cloud imaging device.

20. The mobile robot of claim 18, wherein the volumetric point cloud imaging device is positioned at a height of greater than 2 feet above the ground and directed to be capable of obtaining a point cloud from a volume of space that includes a floor plane in a direction of movement of the robot.

21. The mobile robot of claim 15, further comprising a laser scanner in communication with the controller and having a field of view centered on the forward drive direction and substantially parallel to a work surface supporting the robot.

22. The mobile robot of claim 15, wherein the controller determines an elevation change associated with the threshold based on a sensor signal of at least one sensor in communication with the controller and issues a command to the drive system to continue to traverse the threshold when the elevation change is within a threshold elevation range.

23. The mobile robot of claim 22, wherein the threshold elevation range prevents high centering of the robot.

24. The mobile robot of claim 22, wherein the threshold elevation range is less than a radius of the drive elements.

25. The mobile robot of claim 15, wherein the controller issues a command to the drive system to maneuver the first and second drive elements to approach a first side of the threshold at least substantially equidistantly before moving the first drive element onto the threshold.

26. The mobile robot of claim 15, wherein the controller issues a command to the drive system to pivot the robot about the second drive element to move the first drive element onto the threshold.

27. The mobile robot of claim 15, wherein the controller issues a command to the drive system to hold the first drive element stationary while moving the second drive element onto the threshold to place both the first and second drive elements on the threshold.

28. The mobile robot of claim 15, wherein the controller issues a command to the drive system to hold the second drive element stationary while moving the first drive element off the second side of the threshold.

29. The mobile robot of claim 15, wherein the controller issues a command to the drive system to continue to pivot the robot about the second drive element after moving the first drive element off the second side of the threshold to move the third drive element onto the threshold.

30. The mobile robot of claim 15, wherein the controller issues a command to the drive system to move both the second and third drive elements off the second side of the threshold at substantially the same time.

31. The mobile robot of claim 15, wherein the controller issues a command to the drive system to move the first and second drive elements off the threshold at the same time, pulling the third drive element over the threshold.

32. The mobile robot of claim 15, wherein the holonomic drive system comprises first, second, and third drive wheels, each drive wheel trilaterally spaced about a vertical center axis and having a drive direction perpendicular to a radial axis with respect to the vertical center axis.

33. The mobile robot of claim 15, wherein the holonomic drive system comprises first, second, and third drive balls, each drive ball trilaterally spaced about a vertical center axis.

34. The mobile robot of claim 15, wherein the holonomic drive system comprises first, second, and third drive ball assemblies, each drive ball assembly comprising:

a drive ball;

a transmission rollers in continuous contact with the respective drive ball, the transmission roller actively rotating about a first axis and passively rotating about a second axis; and

a drive mechanism rotating the transmission roller to rotate the drive ball.

35. A method of operating a mobile robot, the method comprising:

driving the robot along a forward drive direction using a holonomic drive system having first, second, and third drive elements configured to maneuver the robot omni-directionally, the forward drive direction coincident with an angled bisector of an angle formed between the first drive element and the second drive element and the first drive element and the third drive element, the first drive element leading the second and third drive element along the forward drive direction;

accelerating the drive system while monitoring an inertial measurement unit of the drive system to maintain vertical stability of the robot; and

decelerating the drive system by applying a braking force to the second and third drive elements while allowing the first drive element to slip on a supporting surface of the robot along the forward drive direction.

36. The method of claim 35, wherein the holonomic drive system comprises first, second, and third drive wheels, each drive wheel trilaterally spaced about a vertical center axis and having a drive direction perpendicular to a radial axis with respect to the vertical center axis.

37. The method of claim 35, wherein the holonomic drive system comprises first, second, and third drive balls, each drive ball trilaterally spaced about a vertical center axis.

38. The method of claim 37, wherein the holonomic drive system comprises first, second, and third drive ball assemblies, each drive ball assembly comprising:

a drive ball;

a transmission rollers in continuous contact with the respective drive ball, the transmission roller actively rotating about a first axis and passively rotating about a second axis; and

a drive mechanism rotating the transmission roller to rotate the drive ball.

39. A method of operating a mobile robot to open a door, the method comprising:

grasping a doorknob of the door with an end effector of a manipulator arm mounted on a body of the robot;

disengaging the door knob;

driving holonomically through a doorway of the door while continuing to grasp the doorknob; and

releasing the doorknob after passing through the doorway.

40. The method of claim 39, further comprising altering a height of the manipulator arm to disengage the doorknob.

41. The method of claim 39, further comprising altering a length of the manipulator arm while passing through the doorway.

42. The method of claim 39, further comprising:

sensing a person near the doorway;

holding the door open to allow the person to pass through the doorway;

detecting when the person has passed through the doorway; and

releasing the doorknob after detection of the person having passed through the doorway.