Method and system for multi-mode coverage for an autonomous robot

• US 20030025472A1
• Filed: 06/12/2002
• Published: 02/06/2003
• Est. Priority Date: 06/12/2001
• Status: Active Grant

• Current Assignee: iRobot Corporation
• Original Assignee: iRobot Corporation
• Inventors: Mass, Philip R., Jones, Joseph L.
• Granted Patent: US 6,809,490 B2
• Time in Patent Office: Days
• US Class Current: 318/568.12
• CPC Class Codes: G05D 1/0219 ensuring the processing of the whole working surface
• CPC Class Codes: G05D 1/0227 using mechanical sensing means, e.g. for sensing treated area
• CPC Class Codes: G05D 1/0238 using obstacle or wall sensors G05D1/0246 and G05D1/0289 take precedence; lidar systems designed for anti-collision purposes G01S17/93
• CPC Class Codes: G05D 1/0242 using non-visible light signals, e.g. IR or UV signals
• 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 2201/0203 Cleaning or polishing vehicle

Abstract

A control system for a mobile robot (10) is provided to Effectively cover a given area by operating in a Plurality of modes, including an obstacle following mode (51) and a random bounce mode (49). In other embodiments, spot coverage, such as spiraling (45), or other modes are also used to increase effectiveness. In addition, a behavior based architecture is used to implement the control system, and various escape behaviors are used to ensure full coverage.

Claims

1. A mobile robot comprising:

(a) means for moving the robot over a surface;

(b) an obstacle detection sensor;

(c) and a control system operatively connected to said obstacle detection sensor and said means for moving;

(d) said control system configured to operate the robot in a plurality of modes, said plurality of modes comprising;

a spot-coverage mode, an obstacle following mode whereby said robot travels adjacent to an obstacle, and a bounce mode whereby the robot travels substantially in a direction away from an obstacle after encountering an obstacle.

2. A mobile robot according to claim 1 in which said control system is configured to operate first in said spot-coverage mode, then alternate operation between said obstacle following mode and said bounce mode.

3. A mobile robot according to claim 2 in which said spot-coverage mode comprises substantially spiral movement.

4. A mobile robot according to claim 2 in which the control system is configured to return to spot-coverage mode after a predetermined traveling distance.

5. A mobile robot according to claim 2 in which the control system is configured to return to spot-coverage mode after a predetermined elapsed time.

6. A mobile robot according to claim 2 in which the control system is configured to return to spot-coverage mode if the average distance between obstacle interactions is above a predetermined threshold.

7. A mobile robot according to claim 1, whereby said obstacle detection sensor comprises a tactile sensor.

8. A mobile robot according to claim 7, whereby said obstacle detection sensor further comprises an IR sensor.

9. The mobile robot according to claim 1, whereby said obstacle following mode comprises alternating between decreasing the turning radius of the robot as a function of distance traveled such that the robot turns toward said obstacle until the obstacle detection sensor detects an obstacle, and decreasing the turning radius of the robot as a function of distance traveled such that the robot turns away from said obstacle until the obstacle detection system no longer detects an obstacle.

10. The mobile robot according to claim 1, whereby the robot operates in obstacle following mode for a distance greater than twice the work width of the robot and less than approximately ten times the work width of the robot.

11. The mobile robot according to claim 10, whereby the robot operates in obstacle following mode for a distance greater than twice the work width of the robot and less than five times the work width of the robot.

12. The mobile robot according to claim 1, further comprising a means for manually selecting an operational mode.

27. A mobile robot according to claim 1, wherein said control system further comprises memory wherein an operational system program is stored, said operational system program comprising a plurality of behaviors and an arbiter to select which behavior is given control over the means for moving.

28. A mobile robot according to claim 27, further comprising an escape behavior.

29. A mobile robot according to claim 28, wherein said obstacle detection sensor comprises a tactile sensor, and wherein said escape behavior comprises operating in said obstacle following mode.

30. A mobile robot according to claim 28, wherein said escape behavior is triggered by the rate of a motor stall event.

31. A mobile robot according to claim 30, wherein said escape behavior is triggered by an increase in said rate of a motor stall event.

32. A mobile robot according to claim 28, wherein said escape behavior is triggered by the duration of sensor input.

33. A mobile robot according to claim 28, wherein said escape behavior comprises shutting off the robot.

34. A mobile robot according to claim 28, wherein said escape behavior is triggered by a lack of sensor input.

13. A mobile robot comprising:

(a) means for moving the robot over a surface;

(b) an obstacle detection sensor;

(c) and a control system operatively connected to said obstacle detection sensor and said means for moving;

(d) said control system configured to operate the robot in a plurality of modes, said plurality of modes comprising;

an obstacle following mode whereby said robot travels adjacent to an obstacle, and a bounce mode whereby the robot travels substantially in a direction away from an obstacle after encountering an obstacle;

(e) whereby said control system is configured to alternate into said obstacle following mode after a predetermined number of sensor interactions.

14. A mobile robot according to claim 13, wherein said predetermined number of sensor interactions is randomly determined.

15. A mobile robot according to claim 13, wherein said predetermined number of sensor interactions is between approximately 5 and approximately 15.

16. A mobile robot according to claim 13, wherein said control system is configured to alternate into said bounce mode after the robot travels a predetermined distance in said obstacle following mode.

17. A mobile robot according to claim 13, wherein said control system is configured to alternate into said bounce mode upon either the robot has traveled a maximum distance or the robot has traveled a minimum distance and an obstacle has been encountered.

18. A mobile robot according to claim 17, wherein said minimum distance is at least 115 cm.

19. A mobile robot according to claim 18, wherein said maximum distance is less than 520 cm.

20. A mobile robot according to claim 13, wherein the control system alternates operational modes based on the distance traveled by said robot.

21. A mobile robot according to claim 13, further comprising a means for determining the level of clutter.

22. A mobile robot according to claim 21, wherein said means for determining the level of clutter comprises tracking the number of interactions with obstacles over time.

23. A mobile robot according to claim 22, further comprising a means for imputing the approximate area of the surface, wherein said means for determining the level of clutter further relates to the approximate area of the surface.

24. A mobile robot according to claim 22, wherein the level of clutter is correlated to the frequency at which the controller alternates operational modes.

25. A mobile robot according to claim 21, wherein the level of clutter is positively correlated to the minimum obstacle following distance.

26. A mobile robot according to claim 13, wherein the control system alternates between operational modes based upon a lack of sensor input.

35. A mobile robot according to claim 13, further comprising a cliff detector, whereby said control system is configured to reduce the robot'"'"'s velocity upon detection of a cliff.

36. A mobile robot according to claim 13, further comprising a wheel drop sensor, whereby said robot utilizes the rate of wheel drop sensor events as input to said control system .

37. A method of controlling a mobile-robot equipped with a sensor for detecting an obstacle, said method comprising the steps of:

a. moving in a spiral running motion;

b. discontinuing said spiral running motion after the earlier of sensing and obstacle or traveling a predetermined distance;

c. running in a substantially forward direction until an obstacle is detected;

d. turning and running along said detected obstacle;

e. turning away from said obstacle and running in a substantially forward direction; and

f. thereafter repeating said step of running along said obstacle and said step of turning away from said obstacle.

38. The mobile-robot steering method according to claim 37, further comprising the step of repeating the spiral running motion after a predetermined number of sensor events.

39. The mobile-robot steering method according to claim 37, whereby the robot runs along said obstacle for at least a minimum distance but less than a maximum distance.

40. The mobile-robot steering method according to claim 39, whereby said obstacle sensor comprises an IR sensor able to detect said boundary.

41. The mobile-robot steering method according to claim 40, whereby said obstacle sensor further comprises a tactile sensor.