Systems and Methods for Use of Optical Odometry Sensors In a Mobile Robot

• US 20160144511A1
• Filed: 09/16/2015
• Published: 05/26/2016
• Est. Priority Date: 11/26/2014
• Status: Active Grant

• Current Assignee: iRobot Corporation
• Original Assignee: iRobot Corporation
• Inventors: Romanov, Nikolai, Case, James Philip, Griest, Kenneth, Swett, David O.
• Granted Patent: US 9,744,670 B2
• Time in Patent Office: Days
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G05B 2219/50393 Floor conveyor, AGV automatic guided vehicle
• CPC Class Codes: G05D 1/0253 extracting relative motion information from a plurality of images taken successively, e.g. visual odometry, optical flow determining position or orientation from images G06T7/70
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: Y10S 901/01 Mobile robot
• CPC Class Codes: Y10S 901/47 Optical

Abstract

Systems and methods for use of optical odometry sensor systems in a mobile robot. The optical odometry sensor system is positioned within a recessed structure on an underside of the mobile robot body and configured to output optical odometry data. The optical odometry sensor system includes an optical odometry camera that includes a telecentric lens configured to capture images of a tracking surface beneath the body and having a depth of field that provides a range of viewing distances at which a tracking surface is captured in focus from a first distance within the recessed structure to a second distance below the underside of the mobile robot body.

Claims

1. A mobile robot configured to navigate an operating environment, comprising:

a body containing;

a drive configured to translate the robot in a direction of motion;

at least one processor;

memory containing a navigation application;

an optical odometry sensor system positioned within a recessed structure on an underside of the body and configured to output optical odometry data, where the optical odometry sensor system comprises an optical odometry camera including a telecentric lens configured to capture images of a tracking surface beneath the body and having a depth of field that provides a range of viewing distances at which a tracking surface is captured in focus from a first distance within the recessed structure to a second distance below the underside of the mobile robot body; and

a gyroscope configured to output gyroscope measurement data.

2. The mobile robot of claim 1, wherein the navigation application directs the processor to:

actuate the drive mechanism and capture;

optical odometry data from the optical odometry sensor system; and

gyroscope measurement data from the gyroscope sensor system;

estimate a distance travelled using the captured optical odometry data;

estimate a direction travelled using the gyroscope measurement data; and

update a pose estimate using the estimated distance travelled and direction travelled.

3. The mobile robot of claim 2, wherein the navigation application directs the processor to estimate a distance travelled using captured wheel odometry data.

4. The mobile robot of claim 2, wherein the navigation application directs the processor to compare the pose estimate against a VSLAM pose determination calculated using imaged features detected by an camera mounted under a top surface of the mobile robot.

5. The mobile robot of claim 3, wherein the navigation application directs the processor to reset the pose estimate if the VLSAM pose determination indicates the mobile robot has drifted from a heading.

6. The mobile robot of claim 1, wherein the telecentric lens has a depth of field in which objects are in focus at distances including distances between negative 5 to 20 mm from a bottom surface of the robot body.

7. The mobile robot of claim 1, further comprising a plurality of lighting elements disposed about the telecentric lens and comprising a plurality of LEDs for illuminating the tracking surface.

8. The mobile robot of claim 7, wherein each of the plurality of LEDs are positioned at an acute angle relative to the optical axis of the camera

9. The mobile robot of claim 7, wherein the plurality of LEDs comprises at least four LEDs positioned at different positions around the camera.

10. The mobile robot of claim 9, wherein pairs of LEDs are positioned on opposite sides relative to the camera.

11. The mobile robot of claim 9, wherein the LEDs are positioned in a spiral pattern offset from the optical axis of the camera.

12. The mobile robot of claim 1, wherein the drive mechanism comprises a plurality of wheels and the mobile robot further comprises a wheel odometry sensor system that outputs wheel odometry data based upon rotation of each of the plurality of wheels.

13. The mobile robot of claim 3, wherein:

the optical odometry sensor system also outputs a quality measure, where the quality measure indicates the reliability of optical odometry data; and

the navigation application directs the processor to estimate a distance travelled using the captured optical odometry data, when a quality measure satisfies a threshold.

14. The mobile robot of claim 13, wherein the quality measure is based on a number of valid features detected in an image.

15. A mobile robot configured to navigate an operating environment, comprising:

a body containing;

a drive configured to translate the robot in a direction of motion;

at least one processor;

memory containing a navigation application;

an optical odometry sensor system positioned within a recessed structure on an underside of the body and configured to output optical odometry data, where the optical odometry sensor system comprises an optical odometry camera positioned at a height between 40 to 60 mm from the floor surface, the optical odometry camera including a telecentric lens configured to capture images of a tracking surface beneath the body and having a depth of field in which objects are in focus at distances including distances between negative 5 to 20 mm from a bottom surface of the robot body; and

a gyroscope configured to output gyroscope measurement data.

16. The mobile robot of claim 15, wherein the recessed structure has an opening with a diameter between 10 mm and 40 mm.

17. The mobile robot of claim 15, wherein the body comprises a top surface that is at most 110 mm from the floor surface.

18. The mobile robot of claim 15, wherein the depth of field of the optical odometry camera is proportional to a focal length of the optical odometry camera.

19. The mobile robot of claim 18, wherein the focal length of the optical odometry camera is between 15 to 25 mm.

20. The mobile robot of claim 15, further comprising four LEDs disposed about the telecentric lens for illuminating the tracking surface.