Autonomous mobile robot

• US 9,457,471 B2
• Filed: 12/30/2014
• Issued: 10/04/2016
• Est. Priority Date: 01/10/2014
• Status: Active Grant

• Current Assignee: iRobot Corporation
• Original Assignee: iRobot Corporation
• Inventors: Schnittman, Mark, Bushman, Thomas W.
• Primary Examiner(s): Tran, Dalena
• Application Number:
  US14/586,099
• Publication Number:
  US 20150197012A1
• Time in Patent Office: 644 Days
• Field of Search: 700/250, 700/245, 700/258, 700/253, 901/1, 901/46, 901/47, 701/23, 701/25, 701/28, 701/532, 318/568.12, 318/568.16, 318584-586
• US Class Current: 1/1
• CPC Class Codes: B25J 9/1694 characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion
• CPC Class Codes: G05D 1/0227 using mechanical sensing means, e.g. for sensing treated area
• 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: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00
• CPC Class Codes: Y10S 901/01 Mobile robot
• CPC Class Codes: Y10S 901/46 Sensing device
• CPC Class Codes: Y10S 901/49 Protective device

Abstract

An autonomous mobile robot includes a robot body, a drive system, a sensor system, and a controller. The drive system supports the robot body and maneuvers the robot over a floor surface. The sensor system includes an inertial measurement unit for measuring a pose of the robot and issues a sensor signal including data having information regarding a pose of the robot. The controller communicates with the drive and sensor systems and executes a behavior system. The behavior system receives the sensor signal from the sensor system and executes a behavior. The behavior system executes an anti-stasis behavior in response to sensor signals indicating that the robot is constrained to evaluate a state of constraint. In addition, the behavior system executes an anti-tilt behavior in response to sensor signals indicating that the robot is tilted with respect to a direction of gravity to evaluate a state of tilt.

Claims

1. An autonomous mobile robot comprising:

a robot body defining a forward drive direction;

a drive system supporting the robot body and configured to maneuver the robot over a floor surface;

a sensor system comprising wheel encoders and an inertial measurement unit for measuring a pose of the robot, the sensor system issuing sensor signals indicative of the pose of the robot; and

a controller in communication with the drive system and the sensor system and having a computing processor executing a behavior system, the behavior system receiving the sensor signals from the sensor system and executing an anti-stasis behavior comprising;

issuing a first wiggle drive command having a first wiggle angle, the first wiggle drive command directing the drive system to drive with a first wiggle motion by driving in alternating left and right directions angled with respect to each other by the first wiggle angle;

determining whether the robot exhibits the first wiggle motion by comparing sensor signals from the wheel encoders and/or the internal measurement unit to a commanded rate of travel; and

when the robot fails to exhibit the first wiggle motion, issuing a second wiggle drive command having a corresponding second wiggle angle to drive with a corresponding second wiggle motion, the second wiggle angle greater than the first wiggle angle.

2. The robot of claim 1, wherein the behavior system executes an anti-tilt behavior in response to sensor signals indicating that the robot is tilted with respect to a direction of gravity to evaluate a state of tilt of the robot body.

3. The robot of claim 1, wherein the controller determines that the robot is in a stasis state when the sensor signals from the wheel encoders and/or the internal measurement unit fail to satisfy an allowable tolerance relative to the commanded rate of travel.

4. The robot of claim 3, wherein the controller issues an anti-stasis command to the drive system when signals of the inertial measurement unit and/or the wheel encoder fail to satisfy the allowable tolerance relative to the commanded rate of travel.

5. The robot of claim 3, wherein the controller is configured to:

monitor whether a command rate of change, an encoder rate of change, and a gyro rate of change with respect to an orientation of the robot satisfy the allowable tolerance relative to the commanded rate of travel; and

determine that the robot is in the stasis state when the command rate of change, the encoder rate of change, or the gyro rate of change with respect to the orientation of the robot fail to satisfy corresponding allowable tolerances relative to the commanded rate of travel.

6. The robot of claim 5, wherein the controller determines that the robot is in the stasis state when the robot is tilted at a tilt angle greater than a threshold angle for more than a threshold period of time.

7. The robot of claim 6, wherein the threshold angle is greater than 15 degrees and the threshold period of time is greater than 3 seconds.

8. The robot of claim 1, wherein the behavior system executes the anti-stasis behavior in response to sensor signals indicating that the robot is constrained to evaluate a constraint state, the constraint state comprising the robot entering or being in a wedged position with respect to an object.

9. The robot of claim 8, wherein the sensor signals comprise:

a bump signal indicating contact of the robot with the object; and

a wheel drop signal indicating movement of a wheel of the drive system away from the robot body.

10. The robot of claim 1, wherein the anti-stasis behavior causes execution of a drive command that backs the robot away from an impediment or turns the robot away from a side of the robot experiencing constraint.

11. The robot of claim 10, wherein the anti-stasis behavior further causes execution of a drive command that drives the robot in an arcuate trajectory.

12. The robot of claim 1, wherein the behavior system executes an anti-tilt behavior in response to sensor signals indicating that the robot is tilted with respect to a direction of gravity for at least a threshold period of time.

13. The robot of claim 12, wherein the anti-tilt behavior causes execution of a forward drive command when the robot is pitched up with respect to the direction of gravity and the forward drive direction, and causes execution of a reverse drive command when the robot is pitched down with respect to the direction of gravity and the forward drive direction.

14. The robot of claim 1, wherein the behavior system executes an anti-tilt behavior in response to sensor signals indicating that the robot is tilted with respect to a direction of gravity at an angle greater than a threshold angle.

15. The robot of claim 14, wherein the anti-tilt behavior causes execution of a forward drive command when the robot is pitched up with respect to the direction of gravity and the forward drive direction, and causes execution of a reverse command when the robot is pitched down with respect to the direction of gravity and the forward drive direction.

16. The robot of claim 1, further comprising a mechanical switch disposed on a bottom surface of the robot forward of a driven wheel of the drive system, the mechanical switch activated when an obstacle contacts the mechanical switch.

17. The robot of claim 16, wherein the behavior system executes the stasis behavior when the mechanical switches are activated to evaluate a state of stasis.

18. The robot of claim 17, further comprising a cleaning system for cleaning or treating the floor surface.

19. The robot of claim 18, wherein the behavior system executes an anti-ingestion behavior when the mechanical switches are activated and the sensor system detects motion, the anti-ingestion behavior causing issuance of a cleaning stop command for stopping a cleaning behavior and issuance of a wiggle command having a wiggle angle, the wiggle command comprising drive commands to drive in alternating left and right drive directions angled with respect to each other by the wiggle angle.

20. The robot of claim 19, wherein the behavior system executes a wheel jam behavior when the controller receives a signal from the sensor system indicating that the wheels of the robot are stalling at a stalling rate less than a stalling threshold rate, the wheel jam behavior causing issuance of the wiggle command for releasing a stalled wheel of the robot.

21. The robot of claim 20, further including a driven roller brush extending parallel to a transverse axis X and rotatably supported by the robot body to contact a floor surface, the driven roller brush rotating in a first direction about the X axis, wherein the anti-ingestion behavior causes biasing of the roller brush to passively rotate in a second direction opposite the first direction.

22. The robot of claim 1, wherein the sensor system includes at least one of obstacle detection obstacle avoidance sensors, communication sensors, navigation sensors, proximity sensors, contact sensors, a camera, a sonar, a radar, a LIDAR, or a LADAR.

23. A control system for an autonomous mobile robot, the control system comprising:

a control arbitration system executing on a computing processor and issuing commands to resources of the robot;

a drive system comprising right and left drive wheels, the drive system supporting the robot body and configured to maneuver the robot over a floor surface;

a sensor system comprising wheel encoders tracking revolution of both dive wheels and an inertial measurement unit measuring a pose of the robot, the sensor system issuing a sensor signal indicative of the pose of the robot; and

a controller in communication with the drive system and the sensor system, the controller having a computing processor executing a behavior system, the behavior system receiving the sensor signals from the sensor system and executing an anti-stasis behavior comprising;

issuing a first wiggle drive command having a first wiggle angle, the first wiggle drive command directing the drive system to drive with a first wiggle motion by driving in alternating left and right directions angled with respect to each other by the first wiggle angle;

determining whether the robot exhibits the first wiggle motion by comparing sensor signals from the wheel encoders and/or the internal measurement unit to a commanded rate of travel; and

when the robot fails to exhibit the first wiggle motion, issuing a second wiggle drive command having a corresponding second wiggle angle to drive with a corresponding second wiggle motion, the second wiggle angle greater than the first wiggle angle.

24. The control system of claim 23, wherein the behavior system executes an anti-tilt behavior in response to sensor signals indicating that the robot is tilted with respect to a direction of gravity to evaluate a state of tilt.

25. A method of operating an autonomous mobile robot, the method comprising:

receiving, at a computing processor, sensor signals from a sensor system of the robot, the sensor signals including odometry signals and inertial measurement signals indicative of a pose of the robot; and

executing on the computing processor a behavior system, the behavior system receiving the sensor signals from the sensor system and executing an anti-stasis behavior comprising;

issuing a first wiggle drive command having a first wiggle angle, the first wiggle drive command directing the robot to drive with a first wiggle motion by driving in alternating left and right directions angled with respect to each other by the first wiggle angle;

determining whether the robot exhibits the first wiggle motion by comparing the odometry signals and/or the internal measurement signals to a commanded rate of travel; and

when the robot fails to exhibit the first wiggle motion, issuing a second wiggle drive command having a corresponding second wiggle angle to drive with a corresponding second wiggle motion, the second wiggle angle greater than the first wiggle angle.