Methods and apparatus for position estimation using reflected light sources

• US 20050213082A1
• Filed: 03/25/2005
• Published: 09/29/2005
• Est. Priority Date: 03/29/2004
• Status: Active Grant

• Current Assignee: iRobot Corporation
• Original Assignee: Evolution Robotics Inc. (iRobot Corporation)
• Inventors: Pirjanian, Paolo, DiBernardo, Enrico
• Granted Patent: US 7,720,554 B2
• Time in Patent Office: Days
• US Class Current: 356/139.30
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01C 3/06 Use of electric means to obtain final indication
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70

Abstract

The invention is generally related to the estimation of position and orientation of an object with respect to a local or a global coordinate system using reflected light sources. A typical application of the method and apparatus includes estimation and tracking of the position of a mobile autonomous robot. Other applications include estimation and tracking of an object for position-aware, ubiquitous devices. Additional applications include tracking of the positions of people or pets in an indoor environment. The methods and apparatus comprise one or more optical emitters, one or more optical sensors, signal processing circuitry, and signal processing methods to determine the position and orientation of at least one of the optical sensors based at least in part on the detection of the signal of one or more emitted light sources reflected from a surface.

Claims

1. A position estimation system for estimating a position of an object in an area defined by a wall having a surface, the system comprising:

a light spot at a substantially fixed location on the surface;

a detector mounted on the object for detecting a reflected light from the light spot; and

a data processing unit mounted on the object for estimating the position of the object using the reflected light detected by the detector.

2. The position estimation system of claim 1, wherein the wall having the surface on which the light spot is projected comprises a ceiling.

3. The position estimation system of claim 1, wherein the light spot is the projection of a light source.

4. The position estimation system of claim 1, wherein the detector comprises a position sensing detector (PSD), and wherein a centroid of the reflected light incident on the PSD is used to estimate the position of the object.

5. The position estimation system of claim 1, wherein the light spot comprises two light spots, and the reflected light comprises two reflected lights respectively from the two light spots, and wherein the data processing unit estimates the position of the object using a distance between locations on which the two reflected lights are respectively incident, on the detector.

6. The position estimation system of claim 1, wherein the data processing unit also estimates an angular orientation of the object.

7. The position estimation system of claim 3, wherein the object further comprises an optical filter for filtering lights having wavelengths that are different from a wavelength of the light spot projected by the light source.

8. The position estimation system of claim 2, wherein the light source comprises two light sources and the light spot comprises two light spots, wherein the two light sources generate lights that have different characteristics from each other, such that the two light spots can be distinguished from each other by the detector and/or the data processing unit.

9. The position estimation system of claim 8, wherein the different characteristics comprise different light intensity patterns.

10. The position estimation system of claim 8, wherein the different characteristics comprise different modulations.

11. The position estimation system of claim 1, wherein the light spot is encoded with a bit pattern to include information that can be extracted by the data processing unit.

12. The position estimation system of claim 1, wherein the surface comprises a reflecting surface for reflecting at least a portion of the light spot projected thereon.

13. A method of estimating a position of an object in an area defined by a wall having a surface, the method comprising:

projecting a light spot at a substantially fixed location on the surface;

detecting a reflected light from the light spot using a detector mounted on the object; and

estimating the position of the object with a data processing unit mounted on the object using the reflected light detected by the detector.

14. The method of claim 13, wherein the projecting a light spot comprises projecting the light spot on the surface of the wall comprising a ceiling.

15. The method of claim 13, wherein the projecting a light spot is accomplished by a light source.

16. The method of claim 13, wherein the detector comprises a position sensing detector (PSD), and wherein the estimating the position comprises estimating the position using a centroid of the reflected light incident on the PSD.

17. The method of claim 13, wherein the light spot comprises two light spots, and the reflected light comprises two reflected lights respectively from the two light spots, and wherein estimating the position comprises estimating the position of the object using a distance between locations on which the two reflected lights are respectively incident, on the detector.

18. The method of claim 13, further comprising estimating an angular orientation of the object.

19. The method of claim 15, further comprising filtering lights having wavelengths that are different from a wavelength of the light spot projected by the light source.

20. The method of claim 15, wherein the light source comprises two light sources and the light spot comprises two light spots, wherein the two light sources generate lights that have different characteristics from each other, such that the two light spots can be distinguished from each other by the detector and/or the data processing unit.

21. The method of claim 20, wherein the different characteristics comprise different light intensity patterns.

22. The method of claim 20, wherein the different characteristics comprise different modulations.

23. The method of claim 13, wherein the light spot can be encoded with a bit pattern to include information that can be extracted by the data processing unit.

24. The method of claim 16, wherein the surface comprises a reflecting surface for reflecting at least a portion of the light spot projected thereon.

25. A computer program embodied in a tangible medium for estimating a position of an object in an area defined by a wall having a surface, the computer program comprising:

a module with instructions configured to compute the location of a light spot at a substantially fixed location on the surface;

a module with instructions configured to compute the location of a reflected light recorded by a detector mounted on the object; and

a module with instructions configured to estimate the position of the object using the location of the light source and the location of the reflected light.

26. The computer program of claim 25, wherein the location of the light spot comprises two locations of two light spots, and the locations of the reflected light comprises two locations of two reflected lights respectively from the two light spots, and wherein the module with instructions configured to estimate the position of the object estimates the position of the object using a distance between locations on which the two reflected lights are respectively incident on the detector.

27. The computer program of claim 25, wherein the module with instructions configured to estimate the position of the object also estimates an angular orientation of the object.