Magnetic field localization and navigation

Patent metadata

Field	Value
Publication number	US-2016377688-A1
Application number	US-201514799319-A
Country	US
Kind code	A1
Filing date	Jul 14, 2015
Priority date	Jun 5, 2015
Publication date	Dec 29, 2016
Grant date	—

Abstract

A mobile robot includes a body movable over a surface within an environment, a calibration coil carried on the body and configured to produce a calibration magnetic field, a sensor circuit carried on the body and responsive to the calibration magnetic field, and a controller carried on the body and in communication with the sensor circuit. The sensor circuit is configured to generate calibration signals based on the calibration magnetic field. The controller is configured to calibrate the sensor circuit as a function of the calibration signals, thereby resulting in a calibrated sensor circuit configured to detect a transmitter magnetic field within the environment and to generate detection signals based on the transmitter magnetic field. The controller is configured to estimate a pose of the mobile robot as a function of the detection signals.

First claim

What is claimed is:

1 . A mobile robot comprising:
a body movable over a surface within an environment; a calibration coil carried on the body and configured to produce a calibration magnetic field; a sensor circuit carried on the body and responsive to the calibration magnetic field, the sensor circuit configured to generate calibration signals based on the calibration magnetic field; and a controller carried on the body and in communication with the sensor circuit, the controller configured to calibrate the sensor circuit as a function of the calibration signals, thereby resulting in a calibrated sensor circuit configured to detect a transmitter magnetic field within the environment and to generate detection signals based on the transmitter magnetic field, wherein the controller is configured to estimate a pose of the mobile robot as a function of the detection signals.

2 . The mobile robot of claim 1 , wherein the robot is a robot lawnmower, the surface comprises a lawn, and the robot further comprises a cutting mechanism below the body, and
wherein the controller is configured to exchange information with a remote device to cause the body to move across the lawn while cutting the lawn using the cutting mechanism, the information comprising a position of the mobile robot relative to a point on the lawn and instructions for movement across the lawn.

3 . The mobile robot of claim 1 , wherein the robot is a cleaning robot and the surface comprises a floor of a room, and
wherein the controller is configured to exchange information with a remote device to cause the body to move across the floor to clean the floor using a floor cleaning mechanism or cleaning pad of the robot, the information comprising a position of the mobile robot in the room and instructions for movement throughout the room.

4 . The mobile robot of claim 1 , wherein the sensor circuit comprises a filter circuit and sensor coils responsive to the transmitter magnetic field; and
the controller is configured to determine coefficients for the filter circuit based on data representing the calibration signals, and apply the coefficients to the filter circuit to normalize a difference in gains of frequency channels corresponding to different frequencies detected by the sensor coils.

5 . The mobile robot of claim 1 , wherein the sensor circuit comprises an amplifier circuit; and
the controller is configured to determine gains of the amplifier circuit based on data representing the calibration signals, and apply the gains to the amplifier circuit to enable dynamic changes to amplitudes of the calibration signals.

6 . The mobile robot of claim 1 , wherein the sensor circuit comprises three sensor coils defining different coil axes and arranged to be responsive to different components of the transmitter magnetic field.

7 . The mobile robot of claim 6 , wherein the coil axes are orthogonal in three dimensions; and wherein the sensor coils are arranged to approximate at least part of an outline of a sphere.

8 . The mobile robot of claim 1 , wherein the controller is configured to calibrate the sensor circuit as a function of the calibration signals and pre-calibration data representing the transmitter magnetic field.

9 . The mobile robot of claim 8 , wherein the controller is configured to compare, to a threshold, a difference between an amplitude of the calibration magnetic field and an amplitude of the transmitter magnetic field, and calibrate the sensor circuit based on the difference.

10 . The mobile robot of claim 1 , wherein the calibrated sensor circuit is configured to generate the detection signals in response to detecting frequencies of components of the transmitter magnetic field between maximum and minimum magnetic field frequencies based on an output of the calibration coil.

11 . The mobile robot of claim 1 , wherein the controller is configured to estimate the pose of the mobile robot by performing operations comprising:
performing a transform using data representing the detection signals to obtain a phase and an amplitude of the transmitter magnetic field; and determining a drift of the phase over time to detect changes in relative orientations of transmission coils that transmit the transmitter magnetic field and sensor coils in the sensor circuit that detect the transmitter magnetic field.

12 . An autonomous robot system comprising:
a magnetic field transmitter comprising transmitter coils configured to generate a transmitter magnetic field; and a robot configured to autonomously maneuver about an environment relative to the magnetic field transmitter, the robot comprising:
a calibration coil configured to generate a calibration magnetic field;
a magnetic field receiver comprising sensor coils responsive to the transmitter magnetic field and to the calibration magnetic field; and
a position determination circuit configured to determine a position of the robot relative to the magnetic field transmitter, based on detection of the transmitter magnetic field by the magnetic field receiver,
wherein the position determination circuit is configured to perform a self-calibration based on data representing the calibration magnetic field as sensed by the magnetic field receiver.

13 . The system of claim 12 , wherein the magnetic field transmitter comprises three transmission coils, each of the three transmission coils defining a transmitter coil axis and being configured to generate a component of the transmitter magnetic field, wherein the transmitter coil axes are orthogonal in three dimensions, and wherein the transmission coils are arranged to approximate at least part of an outline of a first sphere; and
wherein the magnetic field receiver comprises three sensor coils, each of the three sensor coils defining a sensor coil axis and being responsive to a component of the transmitter magnetic field, wherein the sensor coil axes are orthogonal in three dimensions, and wherein the sensor coils are arranged to approximate at least part of an outline of a second sphere, the second sphere being smaller in diameter than the first sphere.

14 . The system of claim 13 , wherein the calibration coil defines an equal angle with respect to each of the sensor coils.

15 . The system of claim 13 , wherein the robot and magnetic field transmitter are physically disconnected.

16 . A method of estimating pose as performed by a mobile robot, the method comprising:
producing a calibration magnetic field using a calibration coil of the mobile robot; detecting the calibration magnetic field using a sensor circuit of the mobile robot; calibrating the sensor circuit based on calibration data representing the calibration magnetic field, thereby resulting in a calibrated sensor circuit; detecting a transmitter magnetic field using the calibrated sensor circuit; and estimating a pose of the mobile robot based on data representing the transmitter magnetic field, as detected using the calibrated sensor circuit.

17 . The method of claim 16 , wherein the sensor circuit comprises a filter circuit and sensor coils responsive to the transmitter magnetic field; and
wherein calibrating the sensor circuit comprises determining coefficients for the filter circuit based on the calibration data, and applying the coefficients to the filter circuit to normalize a difference in gains of frequency channels corresponding to different frequencies received by the sensor coils.

18 . The method of claim 16 , wherein the sensor circuit comprises an amplifier circuit; and
wherein

Assignees

• Irobot Corp

Inventors

• Kleiner Alexander D
• Romanov Nikolai
• Hook Frederic D

Classifications

• G01R33/0035 Primary

  Calibration of single magnetic sensors, e.g. integrated calibration · CPC title

• Y10S901/30

  End effector · CPC title

• G01S1/00

  Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith (position fixing by co-ordinating a plurality of determinations of direction or position lines G01S5/00) · CPC title

• Y10S901/46

  Sensing device · CPC title

• B25J9/1694

  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 title