Methods and apparatus for position estimation using reflected light sources

• US 7,720,554 B2
• Filed: 03/25/2005
• Issued: 05/18/2010
• Est. Priority Date: 03/29/2004
• Status: Expired due to Fees

• Current Assignee: iRobot Corporation
• Original Assignee: Evolution Robotics Inc. (iRobot Corporation)
• Inventors: Pirjanian, Paolo, DiBernardo, Enrico
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Brainard; Timothy A
• Application Number:
  US11/090,621
• Publication Number:
  US 20050213082A1
• Time in Patent Office: 1,880 Days
• Field of Search: 356/139.03, 356/3.06, 356/3.12
• US Class Current: 700/56
• 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:

two light sources configured to project two light spots at a substantially fixed location on the surface;

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

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

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, wherein the different characteristics comprise different modulations,

wherein the wall having the surface on which the two light spots are projected comprises a ceiling.

2. 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.

3. The position estimation system of claim 1, wherein 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.

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

5. The position estimation system of claim 1, wherein the object further comprises an optical filter for filtering lights having wavelengths that are different from a wavelength of the two light spots projected by the two light sources.

6. The position estimation system of claim 1, wherein the different characteristics comprise different light intensity patterns.

7. The position estimation system of claim 1, wherein at least one of the two light spots is encoded with a bit pattern to include information that can be extracted by the data processing unit.

8. The position estimation system of claim 1, wherein the surface comprises a reflecting surface for reflecting at least a portion of at least one of the two light spots projected thereon.

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

projecting two light spots at a substantially fixed location on the surface;

detecting a reflected light from the two light spots 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,

wherein the projecting of the two light spots is accomplished by two light sources,

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,

wherein the different characteristics comprise different modulations.

10. The method of claim 9, wherein the projecting two light spots comprises projecting the two light spots on the surface of the wall comprising a ceiling.

11. The method of claim 9, 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.

12. The method of claim 11, wherein the surface comprises a reflecting surface for reflecting at least a portion of the two light spots projected thereon.

13. The method of claim 9, wherein 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.

14. The method of claim 9, further comprising estimating an angular orientation of the Object.

15. The method of claim 9, further comprising filtering lights having wavelengths that are different from a wavelength of the two light spots projected by the two light sources.

16. The method of claim 9, wherein the different characteristics comprise different light intensity patterns.

17. The method of claim 9, wherein the two light spots can be encoded with a bit pattern to include information that can be extracted by the data processing unit.

18. A position estimation system for estimating a position of an object, the system comprising:

one or more light sources configured to project at least light spots onto a surface;

a detector affixed to the object configured to detect the at least two light spots, wherein the at least two light spots comprise reflected light from the one or more light sources; and

a data processing unit configured to determine the position of the object based on the location of the at least two light spots,

wherein the at least two light spots comprise two or more light spots that differ with respect to an optical characteristic, and wherein the detector is configured to distinguish the two or more light spots based on the optical characteristic,

wherein the optical characteristic is light modulation, and

wherein the system is configured to extract a modulation signal using a band-pass filter with lower and upper frequencies.

19. The position estimation system of claim 18, wherein:

the at least two light spots comprise two or more light spots that are separated by a distance and differ with respect to an optical characteristic;

the optical characteristic is a light intensity, light pattern, light modulation, wavelength, or combination thereof;

the system is configured to distinguish the two or more light spots based on the optical characteristic;

the system is configured to determine the position of the object in two or more dimensions;

the detector comprises a plurality of photo detectors, wherein the plurality of photo detectors are configured so that a centroid of the reflected light of the at least two light spots is identifiable by the system;

the system is configured to determine the position of the object using the identification of the centroid, wherein the position includes a heading, orientation, distance measurement, speed of the object, or combination thereof;

the one or more light sources comprises at least one light-emitting diode (LED), infrared light device, polarized light device, laser diode, or combination thereof;

the object is an autonomous robot; and

the system is configured to determine the robot'"'"'s position relative to a reference coordinate system for localization.

20. The position estimation system of claim 18, wherein the detector comprises a plurality of photo detectors.

21. The position estimation system of claim 20, wherein the plurality of photo detectors is configured to identify a centroid of the reflected light of a first light spot, and the data processing unit is configured to determine the position of the object based on the centroid.

22. The position estimation system of claim 18, wherein the at least two light spots comprise two or more projected light spots that are separated by a distance.

23. The position estimation system of claim 18, wherein the optical characteristic is a light intensity, light pattern, light modulation, wavelength, or combination thereof.

24. The position estimation system of claim 18, wherein the position of the object determined by the data processing unit includes a heading, orientation, distance measurement, speed of the object, or combination thereof.

25. The position estimation system of claim 18, wherein the one or more light sources comprises at least one infrared light device.

26. The position estimation system of claim 18, wherein the object is an autonomous robot, the one or more light sources comprises a plurality of light-emitting diodes removably attachable to a wall outlet, and the data processing unit determines the robot'"'"'s position relative to a reference coordinate system for localization.

27. The position estimation system of claim 18, wherein a first of the light sources is to be situated in a first room and to project a first light spot with a first optical characteristic, a second of the light sources is to be situated in a second room and to project a second light spot with a second optical characteristic different than the first optical characteristic, and the data processing unit is configured to build a topological map of the first and second rooms and the connectivity of the first and second rooms via detection of the first optical characteristic and the second optical characteristic.

28. The position estimation system of claim 18, wherein a first of the light sources projects a light spot onto a ceiling above a docking station via which the object can dock for charging.

29. The position estimation system of claim 18, further comprising an optical filter configured to constrain wavelengths of light that reach the detector to reduce the effect of ambient light, to narrow a range of light to match a wavelength of the light coming from at least a first light source, and/or to limit an amount of light projected onto the detector.

30. The position estimation system of claim 18, wherein the data processing unit is configured to determine a ceiling height and a distance between a first light spot and a second light spot.

31. The position estimation system of claim 18, wherein the one or more light sources comprises at least two light sources in a single housing, wherein the two light sources generate lights that have different characteristics from each other, such that light spots projected by each the two light sources can be distinguished from each other by the system.

32. The position estimation system of claim 18, wherein the data processing unit is configured to determine the position the object in three dimensions.

33. The position estimation system of claim 18, wherein:

the system is configured to determine the position of the object in two or more dimensions;

the detector comprises a plurality of photo detectors, wherein the plurality of photo detectors are configured so that a centroid of the reflected light of the at least two light spots is identifiable by the system;

the system is configured to determine the position of the object using the identification of the centroid, wherein the position includes a heading, orientation, distance measurement, speed of the object, or combination thereof;

the one or more light sources comprises at least one light-emitting diode (LED), infrared light device, polarized light device, laser diode, or combination thereof;

the object is an autonomous robot; and

the system is configured to determine the robot'"'"'s position relative to a reference coordinate system for localization.