Methods and apparatus for position estimation using reflected light sources

• US 7,996,097 B2
• Filed: 05/14/2010
• Issued: 08/09/2011
• Est. Priority Date: 03/29/2004
• Status: Expired due to Fees

• Current Assignee: iRobot Corporation
• Original Assignee: Evolution Robotics Inc. (iRobot Corporation)
• Inventors: DiBernardo, Enrico, Pirjanian, Paolo
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Brainard; Timothy A
• Application Number:
  US12/780,746
• Publication Number:
  US 20100228421A1
• Time in Patent Office: 452 Days
• Field of Search: 701/23, 701/25, 701/200, 701/206, 701207-223, 701/300, 700 56- 59
• 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 location estimation system for estimating a location of a self-propelled object, the system comprising:

a modulator;

a first light source coupled to the modulator,

wherein the modulator is configured to modulate light from the first light source,

wherein the first light source is configured to project modulated light,

whereby at least one light spot is projected onto a surface at an area substantially directly above the first light source when the first light source is positioned for operation with the self-propelled object;

a detector configured to detect the at least one light spot based at least in part on the modulation; and

a data processing unit configured to;

determine a direction of the detected at least one light spot with respect to a first reference point, and

determine the location of the self-propelled object based at least in part on the determined direction,

wherein the first light source projects light in a fixed direction.

2. The location estimation system of claim 1, wherein the first light source includes a plurality of light emitters, and the at least one light spot includes at least two light spots.

3. The location estimation system of claim 1, wherein the first light source includes a first plurality of light emitters configured to project at least two light spots,

wherein the modulator is configured to cause light projected to form a first of the two light spots to be modulated differently than light projected to form a second of the two light spots;

and

the location estimation system is configured to distinguish between the first light spot and the second light spot based on the respective modulations used to form the first light spot and the second light spot.

4. The location estimation system of claim 1, wherein the first light source includes a first plurality of light emitters configured to project at least two light spots,

wherein the modulator is configured to:

cause a first of the two light spots to have a first light pattern; and

cause a second of the two light spots to have a second light pattern, wherein the second light pattern is different than the first light pattern.

5. The location estimation system of claim 1, wherein determining the location further comprises determining an orientation of the self-propelled object.

6. The location estimation system of claim 1, wherein determining the location further comprises determining:

a distance of the self-propelled object from another object; and

a bearing of the self-propelled object.

7. The location estimation system of claim 1, wherein determining the location further comprises determining a pose of the self-propelled object.

8. The location estimation system of claim 1, wherein the first light source is an infrared light source.

9. The location estimation system of claim 1, wherein the location estimation system is configured to:

project at least two light spots;

detect the at least two light spots;

based at least in part on the detection of the at least two light spots, determine a position associated with the detector in two dimensions in a first plane; and

determine a rotation associated with the detector around an axis normal to the first plane.

10. The location estimation system of claim 1, wherein the detector includes position sensing detector configured to measure the centroid of at least one light spot.

11. The location estimation system of claim 1, wherein the detector includes a two-dimensional array of photodetectors.

12. The location estimation system of claim 1, wherein the detector includes a plurality of photodetectors.

13. The location estimation system of claim 1, wherein the detector is configured to measure light intensity and position.

14. The location estimation system of claim 1, wherein the detector includes a sensor, a lens, and a filter, wherein the filter is configured to narrow a range of light received by the sensor to correspond to the light projected by the first light source.

15. The location estimation system of claim 1, further comprising a second light source configured to project light with a different modulation than the first light source, wherein the first light source is housed separately from the second light source, and

wherein the location estimation system is configured to:

associate the modulation associated with the first light source with a first room and the modulation associated with the second light source with a second room; and

to build a topological map including connectivity of the first room and the second room.

16. The location estimation system of claim 1, wherein the at least one light spot includes at least two light spots, and the location estimation system is configured to measure a distance between at least a first light spot and a second light spot and a distance corresponding to a distance between the detector and the surface.

17. The location estimation system of claim 1, wherein the location estimation system is configured to maintain a history of paths traversed by the self-propelled object.

18. The location estimation system of claim 1, wherein the first light source further comprises a collimating lens.

19. The location estimation system of claim 1, wherein the self-propelled object is a floor cleaner.

20. A location estimation system for estimating a location of a self-propelled object, the system comprising:

a modulator;

a first light source coupled to the modulator,

wherein the modulator is configured to modulate light from the first light source,

wherein the first light source is configured to project modulated light,

whereby at least one light spot is projected onto a surface at an area substantially directly above the first light source when the first light source is positioned for operation with the self-propelled object;

a detector configured to detect the at least one light spot based at least in part on the modulation; and

a data processing unit configured to;

determine a direction of the detected at least one light spot with respect to a first reference point, and

determine the location of the self-propelled object based at least in part on the determined direction,

wherein the detector is configured to detect the at least one light spot without having a line of sight view of the first light source.

21. A location estimation system for estimating a location of a self-propelled object, the system comprising:

a modulator;

a first light source coupled to the modulator,

wherein the modulator is configured to modulate light from the first light source

wherein the first light source is configured to project modulated light,

whereby at least one light spot is projected onto a surface at an area substantially directly above the first light source when the first light source is positioned for operation with the self-propelled object;

a detector configured to detect the at least one light spot based at least in part on the modulation; and

a data processing unit configured to;

determine a direction of the detected at least one light spot with respect to a first reference point, and

determine the location of the self-propelled object based at least in part on the determined direction,

wherein the first light source includes a first plurality of light emitters configured to project at least two light spots,

wherein the modulator is configured to;

cause light projected to form a first of the two light spots to be modulated at a first frequency; and

cause light projected to form a second of the two light spots to be modulated at a second frequency different than the first frequency.

22. A location estimation system for estimating a location of a self-propelled object, the system comprising:

a modulator;

a first light source coupled to the modulator,

wherein the modulator is configured to modulate light from the first light source,

wherein the first light source is configured to project modulated light,

whereby at least one light spot is projected onto a surface at an area substantially directly above the first light source when the first light source is positioned for operation with the self-propelled object;

a detector configured to detect the at least one light spot based at least in part on the modulation; and

a data processing unit configured to;

determine a direction of the detected at least one light spot with respect to a first reference point, and

determine the location of the self-propelled object based at least in part on the determined direction;

a data processing unit included in the self-propelled object, wherein;

the modulator is configured to encode a command for the self-propelled object in the light projected from the first light source; and

the data processing unit included in the self-propelled object is configured to decode the command.

23. The location estimation system of claim 22,

wherein the command is configured to command the self-propelled object to go to a docking station;

and

the data processing unit included in the self-propelled object is configured to receive the command and in response, cause the self-propelled object to go to the docking station.

24. A location estimation system for estimating a location of a self-propelled object, the system comprising:

a modulator;

a first light source coupled to the modulator,

wherein the modulator is configured to modulate light from the first light source,

wherein the first light source is configured to project modulated light,

whereby at least one light spot is projected onto a surface at an area substantially directly above the first light source when the first light source is positioned for operation with the self-propelled object;

a detector configured to detect the at least one light spot based at least in part on the modulation; and

a data processing unit configured to;

determine a direction of the detected at least one light spot with respect to a first reference point, and

determine the location of the self-propelled object based at least in part on the determined direction,

wherein the first light source is included in a docking station configured to charge the self-propelled object,

wherein the first light source is positioned so at to project the modulated light to a surface above the docking station when the docking station is positioned to receive the self propelled object.

25. The location estimation system of claim 24, wherein:

the detector is included in the self-propelled object.

26. A location estimation system for estimating a location of a self-propelled object, the system comprising:

a modulator;

a first light source coupled to the modulator,

wherein the modulator is configured to modulate light from the first light source,

wherein the first light source is configured to project modulated light,

whereby at least one light spot is projected onto a surface at an area substantially directly above the first light source when the first light source is positioned for operation with the self-propelled object;

a detector configured to detect the at least one light spot based at least in part on the modulation; and

a data processing unit configured to;

determine a direction of the detected at least one light spot with respect to a first reference point, and

determine the location of the self-propelled object based at least in part on the determined direction,

wherein the at least one light spot includes at least two light spots, and wherein the location estimation system is configured to assign a first unique identifier to a first of the at least to spots and to assigned a second identifier to a second of the at least two spots.

27. A location estimation system for estimating a location of a self-propelled object, the system comprising:

a first light source configured to;

project a first light spot having a first characteristic onto a surface;

project a second light spot having a second characteristic onto the surface,

wherein the first characteristic is different than the second characteristic;

a detector configured to;

identify the first light spot based at least in part on the first characteristic;

identify the second light spot based at least in part on the second characteristic; and

a data processing unit configured to determine the location of the self-propelled object based at least in part on;

the identification of the first light spot; and

the identification of the second light spot.

28. The location estimation system of claim 27, wherein the first characteristic comprises a first light intensity pattern and the second characteristic comprises a second light intensity pattern.

29. The location estimation system of claim 27, wherein the first characteristic comprises a first modulation and the second characteristic comprises a second modulation.

30. A method of estimating a location of a self-propelled object, the system comprising, the method comprising:

projecting a first light spot having a first characteristic onto a surface;

projecting a second light spot having a second characteristic onto the surface,

wherein the first characteristic is different than the second characteristic;

detecting the first light spot;

detecting the second light spot;

identifying the first light spot based at least in part on the first characteristic;

identifying the second light spot based at least in part on the second characteristic; and

determining the location of the self-propelled object based at least in part on;

the identification of the first light spot; and

the identification of the second light spot.