Obstacle following sensor scheme for a mobile robot

• US 8,412,377 B2
• Filed: 06/24/2005
• Issued: 04/02/2013
• Est. Priority Date: 01/24/2000
• Status: Active Grant

• Current Assignee: iRobot Corporation
• Original Assignee: iRobot Corporation
• Inventors: Casey, Christopher, Cross, Matthew, Ozick, Daniel, Jones, Joseph L.
• Primary Examiner(s): Tran, Khoi
• Assistant Examiner(s): Amin, Bhavesh V
• Application Number:
  US11/166,986
• Publication Number:
  US 20050251292A1
• Time in Patent Office: 2,839 Days
• Field of Search: None
• US Class Current: 700/253
• CPC Class Codes: A47L 2201/04 Automatic control of the travelling movement; Automatic obstacle detection
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G01S 15/931 of land vehicles
• CPC Class Codes: G01S 17/93 for anti-collision purposes
• 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 1/024 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 1/0255 using acoustic signals, e.g. ultra-sonic singals sonar systems designed for anti-collision purposes G01S15/93
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]
• CPC Class Codes: Y10S 901/01 Mobile robot
• CPC Class Codes: Y10S 901/47 Optical

Abstract

A robot obstacle detection system including a robot housing which navigates with respect to a surface and a sensor subsystem aimed at the surface for detecting the surface. The sensor subsystem includes an emitter which emits a signal having a field of emission and a photon detector having a field of view which intersects the field of emission at a region. The subsystem detects the presence of an object proximate the mobile robot and determines a value of a signal corresponding to the object. It compares the value to a predetermined value, moves the mobile robot in response to the comparison, and updates the predetermined value upon the occurrence of an event.

Claims

1. A method for operating a mobile robot, the method comprising:

detecting the presence of an object proximate the mobile robot by emitting an infrared signal and detecting a reflected infrared signal;

sensing a value of the reflected infrared signal corresponding to the object;

comparing the sensed value to a threshold value corresponding to a detected surface having a threshold level of reflectivity;

moving the mobile robot with respect to the detected object in response to the comparison of the sensed value and the threshold value; and

updating the threshold value upon the occurrence of an event, the event comprising at least one of a physical contact between the mobile robot and the object and when the updated threshold value is less than the non-updated threshold value.

2. The method of claim 1, wherein updating the threshold value comprises multiplying the threshold value by a constant.

3. The method of claim 2, wherein the event comprises when the updated threshold value is less than the non-updated threshold value.

4. The method of claim 1, wherein moving with respect to the detected object comprises moving toward the detected object, when the sensed value is less than the threshold value.

5. The method of claim 1, wherein moving with respect to the detected object comprises moving away from the detected object, when the sensed value is greater than the threshold value.

6. The method of claim 1, further comprising conditioning the sensed value of the reflected signal.

7. The method of claim 1, further comprising executing a first detection at a first distance to the object and executing a second detection at a second distance to the object.

8. The method of claim 1, further comprises detecting a plurality of reflected signals, averaging the detected signals, and sensing a value of the averaged reflected signal.

9. The method of claim 1, wherein detecting the presence of an object proximate the mobile robot comprises detecting a reflected signal by a plurality of sensors disposed on the mobile robot in a pattern to accommodate a variation in object reflectivity.

10. The method of claim 1, further comprising varying power of the emitted signal.

11. The method of claim 1, further comprising varying sensitivity of at least one sensor emitting the signal.

12. The method of claim 1, wherein the emitted signal comprises light having at least one of a visible wavelength and an infrared wavelength.

13. The method of claim 1, wherein the emitted signal comprises an acoustic wave having at least one of an audible frequency and an ultrasonic frequency.

14. The method of claim 1, wherein detecting the presence of an object proximate the mobile robot comprises:

emitting a directed signal emission; and

detecting the reflected signal emission within a detection field of view;

wherein the directed signal emission and the detection field of view at an angle with respect to each other and have an intersection region occurring at a distance away from the robot.

15. The method of claim 1, wherein the sensed value corresponds to at least one of a distance to the object and an albedo of the object.

16. A method for operating a mobile robot, the method comprising the mobile robot:

detecting a transition between a reflection state and a non-reflection state of an emitted infrared signal for determining the presence and absence of an object proximate the mobile robot, respectively;

sensing a value of the reflected infrared signal corresponding to the object;

comparing the sensed value to a threshold value corresponding to a detected surface having a threshold level of reflectivity;

in response to the comparison of the sensed value and the threshold value, causing the robot to move a travel distance in a first direction with respect to the detected object and to rotate in a second direction about a fixed point; and

updating the threshold value upon the occurrence of an event, the event comprising at least one of a physical contact between the mobile robot and the object and when the updated threshold value is less than the non-updated threshold value.

17. The method of claim 16, wherein the travel distance moved by the mobile robot relates at least in part to an offset distance from a sensor located on the robot to a robot wheel axis.

18. The method of claim 16, wherein the first direction is defined at least in part by a direction of motion of the robot prior to detecting the absence of the object.

19. The method of claim 16, wherein the fixed point comprises a point between a first wheel of the robot and the object.

20. The method of claim 16, further comprising ceasing rotation upon detecting a presence of an object.

21. The method of claim 16, further comprising ceasing rotation upon contacting an object.

22. The method of claim 16, further comprising moving in a third direction.