TECHNICAL FIELD

This specification relates to magnetic navigation systems, in particular, for autonomous mobile robots.

BACKGROUND

An autonomous mobile robot can navigate about a floor surface in the environment. The robot can perform various tasks in the environment, such as cleaning or patrolling. The robot can include various powered systems, such as a drive system controlled by the robot to propel the robot across the floor surface. The robot can have a battery that supplies energy to the robot to use these powered systems. When the battery of the robot is depleted, the robot can return to a charging station that replenishes the energy stored on the battery.

SUMMARY

An autonomous mobile robot can be charged when the robot is docked to a charging station. The robot can include two magnetic field antennae that respond to magnetic field signals, e.g., pulses, emitted by a charging station. During a docking operation in which the robot moves toward the charging station to dock to the charging station, responses of the antennae may differ from one another and indicate that a forward drive direction of the robot is not aligned with the charging station. When the responses differ from one another, the robot can reorient itself relative to the charging station such that the robot can continue to advance in the forward drive direction toward the charging station during the docking operation.

In one aspect, an autonomous mobile robot is featured. The autonomous mobile robot includes a drive system to maneuver the autonomous mobile robot about an environment, a first magnetic field antenna system responsive to a magnetic field pulse to generate a first signal, and a second magnetic field antenna system responsive to the magnetic field pulse to generate a second signal. The magnetic field pulse is emitted by a magnetic field emitter system in the environment. The autonomous mobile robot further includes a controller to execute instructions to perform operations including reorienting the autonomous mobile robot based on the first signal and the second signal.

In some implementations, the operations can include moving, in a docking operation, the autonomous mobile robot toward a charging station until the autonomous mobile robot is within a distance from the charging station. The operations can include reorienting the autonomous mobile robot based on the first signal and the second signal includes reorienting, in the docking operation, the autonomous mobile robot relative to the charging station in response to the autonomous mobile robot being within the distance from the charging station and based on the first signal and the second signal.

In some implementations, the operations can include after reorienting the autonomous mobile robot relative to the charging station in response to the autonomous mobile robot being within the distance from the charging station, moving the autonomous mobile robot toward the charging station and reorienting the autonomous mobile robot relative to the charging station such that a difference between distances of the first and second magnetic field antenna systems to the magnetic field emitter system decreases.

In some implementations, the autonomous mobile robot can further include a battery configured to be charged at a charging station including the magnetic field emitter system. The operations can include initiating a docking operation to move the autonomous mobile robot to the charging station to charge the battery. Reorienting the autonomous mobile robot can include reorienting the autonomous mobile robot during the docking operation.

In some implementations, reorienting the autonomous mobile robot can include reorienting the autonomous mobile robot in response to determining the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station.

In some implementations, reorienting the autonomous mobile robot in response to determining the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station can include reorienting the autonomous mobile robot in response to the first signal and the second signal indicating that the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station.

In some implementations, a strength of the magnetic field pulse detected at the first magnetic field antenna system can be greater than a strength of the magnetic field pulse at the second magnetic field antenna system.

In some implementations, the first signal generated by the first magnetic field antenna system can include a clipped portion, and the second signal generated by the second magnetic field antenna system can include a clipped portion. A duration of the clipped portion of the first signal can be greater than a duration of the clipped portion of the second signal.

In some implementations, the operations can further include obtaining a first value by extrapolating a declining portion of the first signal, obtaining a second value by extrapolating a declining portion of the second signal, and determining that the first signal and the second signal indicate that the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station based on the first value being greater than the second value.

In some implementations, the battery can be configured to be charged by a magnetic field emitted by the magnetic field emitter system of the charging station.

In some implementations, initiating the docking operation to move the autonomous mobile robot to the charging station to charge the battery can include initiating the docking operation to move the autonomous mobile robot to a charging position in which the autonomous mobile robot is positioned above at least a portion of the magnetic field emitter system of the charging station.

In some implementations, in the charging position, the autonomous mobile robot can be positioned above an inductive coil of the magnetic field emitter system of the charging station.

In some implementations, the magnetic field emitter system can be a first magnetic field emitter, and the battery can be configured to be charged by a second magnetic field emitter system of the charging station.

In some implementations, the operations can further include moving the autonomous mobile robot in response to determining that the autonomous mobile robot is misaligned with the charging station as the charging station performs a charging operation to charge the battery of the autonomous mobile robot.

In some implementations, the operations can further include as the charging station performs a charging operation to charge the battery of the autonomous mobile robot, periodically communicating with the charging station to indicate a presence of the autonomous mobile robot at the charging station.

In some implementations, the operations can further include as the charging station performs a charging operation to charge the battery of the autonomous mobile robot, communicating with the charging station to indicate a presence of the autonomous mobile robot at the charging station. Communicating with the charging station can include producing a capacitance change detectable by the charging station.

In some implementations, the autonomous mobile robot can include a navigation sensor configured to generate mapping data as the autonomous mobile robot moves about the environment. The operations can include navigating the autonomous mobile robot toward the magnetic field emitter system based on the mapping data, and then navigating, in response to determining that the autonomous mobile robot is within a distance from the magnetic field emitter system, the autonomous mobile robot based on outputs of the first magnetic field antenna system and outputs of the second magnetic field antenna system.

In some implementations, the magnetic field pulse can include a first magnetic field pulse. The first magnetic field antenna system can be responsive to a second magnetic field pulse to generate a third signal. The second magnetic field pulse can be emitted by the magnetic field emitter system. The second magnetic field antenna system can be responsive to the second magnetic field pulse to generate a fourth signal.

In some implementations, reorienting the autonomous mobile robot based on the first signal and the second signal can include moving the autonomous mobile robot in a first direction in response to the first signal and the second signal indicating that the first magnetic field antenna system is closer to a charging station than the second magnetic field antenna system is to the charging station. The charging station can include the magnetic field emitter system, and the operations can further include moving the autonomous mobile robot in a second direction in response to the third signal and the fourth signal indicating that the second magnetic field antenna system is closer to the charging station than the first magnetic field antenna system is to the charging station.

In some implementations, the first magnetic field antenna system can be positioned on a first lateral half of the autonomous mobile robot, and the second magnetic field antenna system can be positioned on a second lateral half of the autonomous mobile robot.

In some implementations, the drive system can further include a first drive wheel and a second drive wheel operable to move the autonomous mobile robot about the environment. The first magnetic field antenna system can be adjacent to the first drive wheel, and the second magnetic field antenna system can be adjacent to the second drive wheel.

In some implementations, a distance between the first magnetic field antenna system and a rightmost edge of the autonomous mobile robot can be no more than 5% to 15% of an overall width of the autonomous mobile robot, and a distance between the second magnetic field antenna system and a leftmost edge of the autonomous mobile robot can be no more than 5% to 15% of the overall width of the autonomous mobile robot.

In some implementations, the first magnetic field antenna system can include a first inductive coil responsive to the magnetic field pulse, and the second magnetic field antenna system can include a second inductive coil responsive to the magnetic field pulse.

In another aspect, a charging station for an autonomous mobile robot is featured. The charging station includes a housing, a magnetic field emitter system supported by the housing, and a controller operably connected to the magnetic field emitter system. The controller is configured to execute instructions to perform operations. The operations include operating the magnetic field emitter system to emit magnetic field pulses to guide the autonomous mobile robot to a docking position above at least a portion of the magnetic field emitter system, and operating the magnetic field emitter system to charge a battery of the autonomous mobile robot.

In some implementations, operating the magnetic field emitter system to emit the magnetic field pulses can include initiating emission of a series of magnetic field pulses, in which a pulse repetition period to emit the series of magnetic field pulses is between 100 and 300 milliseconds.

In some implementations, the charging station can further include a current sensor configured to detect a metallic object proximate to the magnetic field emitter system.

In some implementations, the current sensor can be configured to detect a resonant capacitance change produced by the autonomous mobile robot. The resonant capacitance change can be indicative of the autonomous mobile robot being in the docking position.

In some implementations, the magnetic field emitter system can include a first magnetic field emitter and a second magnetic field emitter. Operating the magnetic field emitter system to emit the magnetic field pulses to guide the autonomous mobile robot to the docking position above at least the portion of the magnetic field emitter system can include operating the first magnetic field emitter to emit the magnetic field pulses to guide the autonomous mobile robot to a docking position above at least the portion of the magnetic field emitter system. Operating the magnetic field emitter system to charge the battery of the autonomous mobile robot can include operating the second magnetic field emitter to charge the battery of the autonomous mobile robot.

In another aspect, a method is featured. The method includes generating, by a first magnetic field antenna system of an autonomous mobile robot, a first signal in response to detecting a magnetic field pulse emitted by a magnetic field emitter system in an environment; generating, by a second magnetic field antenna system of the autonomous mobile robot, a second signal in response to detecting the magnetic field pulse; and reorienting the autonomous mobile robot based on the first signal and the second signal.

In some implementations, the method can further include moving, in a docking operation, the autonomous mobile robot toward a charging station until the autonomous mobile robot is within a distance from the charging station, and reorienting the autonomous mobile robot based on the first signal and the second signal can include reorienting, in the docking operation, the autonomous mobile robot relative to the charging station in response to the autonomous mobile robot being within the distance from the charging station and based on the first signal and the second signal.

In some implementations, the method can further include after reorienting the autonomous mobile robot relative to the charging station in response to the autonomous mobile robot being within the distance from the charging station, moving the autonomous mobile robot toward the charging station and reorienting the autonomous mobile robot relative to the charging station such that a difference between a value of the first signal and a value of the second signal decreases.

In some implementations, the method can further include initiating a docking operation to move the autonomous mobile robot to a charging station to charge a battery of the autonomous mobile robot. Reorienting the autonomous mobile robot can include reorienting the autonomous mobile robot during the docking operation.

In some implementations, reorienting the autonomous mobile robot can include reorienting the autonomous mobile robot in response to determining the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station.

In some implementations, reorienting the autonomous mobile robot in response to determining the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station can include reorienting the autonomous mobile robot in response to the first signal and the second signal indicating that the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station.

In some implementations, a strength of the magnetic field pulse detected at the first magnetic field antenna system can be greater than a strength of the magnetic field pulse at the second magnetic field antenna system.

In some implementations, the first signal generated by the first magnetic field antenna system can include a clipped portion, and the second signal generated by the second magnetic field antenna system can include a clipped portion. A duration of the clipped portion of the first signal can be greater than a duration of the clipped portion of the second signal.

In some implementations, the method can include obtaining a first value by extrapolating a declining portion of the first signal, obtaining a second value by extrapolating a declining portion of the second signal, and determining that the first signal and the second signal indicate that the first magnetic field antenna system is closer to the charging station than the second magnetic field antenna system is to the charging station based on the first value being greater than the second value.

In some implementations, the method can include docking the autonomous mobile robot to the charging station such that the battery of the autonomous mobile robot is charged by a magnetic field emitted by the magnetic field emitter system of the charging station.

In some implementations, initiating the docking operation to move the autonomous mobile robot to the charging station to charge the battery can include initiating the docking operation to move the autonomous mobile robot to a charging position in which the autonomous mobile robot is positioned above at least a portion of the magnetic field emitter system of the charging station.

In some implementations, in the charging position, the autonomous mobile robot can be positioned above an inductive coil of the magnetic field emitter system of the charging station.

In some implementations, the magnetic field emitter system can be a first magnetic field emitter, and the method can further include docking the autonomous mobile robot to the charging station such that the battery of the autonomous mobile robot is charged by a second magnetic field emitter system of the charging station.

In some implementations, the method can include moving the autonomous mobile robot in response to determining that the autonomous mobile robot is misaligned with the charging station as the charging station performs a charging operation to charge the battery of the autonomous mobile robot.

In some implementations, the method can further include as the charging station performs a charging operation to charge the battery of the autonomous mobile robot, periodically communicating with the charging station to indicate a presence of the autonomous mobile robot at the charging station.

In some implementations, the method can further include as the charging station performs a charging operation to charge the battery of the autonomous mobile robot, communicating with the charging station to indicate a presence of the autonomous mobile robot at the charging station. Communicating with the charging station can include producing a resonant capacitance change detectable by the charging station.

In some implementations, the method can further include navigating the autonomous mobile robot toward the magnetic field emitter system based on mapping data produced by the autonomous mobile robot, and then navigating, in response to determining that the autonomous mobile robot is within a distance from the magnetic field emitter system, the autonomous mobile robot based on outputs of the first magnetic field antenna system and outputs of the second magnetic field antenna system.

In some implementations, the magnetic field pulse can include a first magnetic field pulse. The first magnetic field antenna system can be responsive to a second magnetic field pulse to generate a third signal. The second magnetic field pulse can be emitted by the magnetic field emitter system. The second magnetic field antenna system can be responsive to the second magnetic field pulse to generate a fourth signal.

In some implementations, reorienting the autonomous mobile robot based on the first signal and the second signal can include moving the autonomous mobile robot in a first direction in response to the first signal and the second signal indicating that the first magnetic field antenna system is closer to a charging station than the second magnetic field antenna system is to the charging station. The charging station can include the magnetic field emitter system. The method can further include moving the autonomous mobile robot in a second direction in response to the third signal and the fourth signal indicating that the second magnetic field antenna system is closer to the charging station than the first magnetic field antenna system is to the charging station.

In some implementations, the first magnetic field antenna system can be positioned on a first lateral half of the autonomous mobile robot, and the second magnetic field antenna system can be positioned on a second lateral half of the autonomous mobile robot.

In some implementations, a distance between the first magnetic field antenna system and a rightmost edge of the autonomous mobile robot can be no more than 5% to 15% of an overall width of the autonomous mobile robot. A distance between the second magnetic field antenna system and a leftmost edge of the autonomous mobile robot can be no more than 5% to 15% of the overall width of the autonomous mobile robot.

In some implementations, the first magnetic field antenna system can include a first inductive coil responsive to the magnetic field pulse, and the second magnetic field antenna system can include a second inductive coil responsive to the magnetic field pulse.

Advantages of the foregoing may include, but are not limited to, those described below and herein elsewhere.

In some implementations, an autonomous mobile robot can use magnetic field pulses emitted by a magnetic field emitter system into an environment to precisely move towards the magnetic field emitter system. In particular, the magnetic field pulses allow the robot to easily align with the magnetic field emitter system. In implementations in which the magnetic field emitter system is part of a charging station for the robot, the charging station can emit the magnetic field pulses to precisely direct the robot to a docking position above the charging station to facilitate charging of the robot.

In some implementations, an autonomous mobile robot can detect the magnetic field pulses emitted by the magnetic field emitter system using low-cost magnetic field antenna systems. The magnetic field antenna systems can be capable of detecting magnetic fields along a single axis and do not need to detect magnetic fields along multiple axes. The costs of these magnetic field antenna systems can thus be low compared to magnetic field antenna systems that detect magnetic fields along multiple axes. Also, instead of relying on high-resolution magnetic field antenna systems that could be costly, the robot can use its controller to operate the magnetic field antenna systems to allow these systems to detect magnetic fields for a large range of field amplitudes. For example, the controller can adjust gains of the magnetic field antenna systems as the robot moves about the environment to increase the range of field amplitudes detectable by the magnetic field antenna systems.

In some implementations, the magnetic field emitter system can be used for multiple purposes, thus decreasing the number of components necessary to guide the robot, charge the robot, and detect foreign objects near the magnetic field emitter system. The magnetic field emitter system can, for example, emit pulses of magnetic fields using an inductive coil, and these pulses can be used to guide the robot to the magnetic field emitter system. This same inductive coil can be used to emit pulses of magnetic fields to charge the robot. In implementations in which the magnetic field emitter system is on a charging station, the charging station need not have both an inductive coil for emitting magnetic field pulses to guide the robot toward the charging station and a separate inductive coil for emitting magnetic field pulses to charge the robot. Furthermore, the magnetic field emitter system can also emit magnetic field pulses to detect foreign objects proximate to the magnetic field emitter system.

The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other potential features, aspects, and advantages will become apparent from the description, the drawings, and the claims.

