Disclosed is a method for calibrating at least one gap sensor, the at least one gap sensor being provided on a magnetic bearing supporting a floating body in a non-contact manner by an electromagnetic force, the at least one gap sensor being configured to detect a gap between the floating body and a reference object that serves as a positional reference for position control of the floating body. The method includes: constructing a transformation formula for transforming an output of the at least one gap sensor into the gap using three or more constraints that are set as conditions for associating the gap with the output of the at least one gap sensor.

Head-mounted augmented reality (AR) devices can track pose of a wearer's head or pose of a hand-held user input device to enable wearer interaction in a three-dimensional AR environment. A pose sensor (e.g., an inertial measurement unit) in the user input device can provide data on pose (e.g., position or orientation) of the user input device. An electromagnetic (EM) tracking system can also provide pose data. For example, the handheld user input device can include an EM emitter that generates an EM field, and the head-mounted AR device can include an EM sensor that senses the EM field. The AR device can combine the output of the pose sensor and the EM tracking system to reduce drift in the estimated pose of the user input device or to transform the pose into a world coordinate system used by the AR device. The AR device can utilize a Kalman filter to combine the output of the pose sensor and the EM tracking system.

Head-mounted augmented reality (AR) devices can track pose of a wearer's head or pose of a hand-held user input device to enable wearer interaction in a three-dimensional AR environment. A pose sensor (e.g., an inertial measurement unit) in the user input device can provide data on pose (e.g., position or orientation) of the user input device. An electromagnetic (EM) tracking system can also provide pose data. For example, the handheld user input device can include an EM emitter that generates an EM field, and the head-mounted AR device can include an EM sensor that senses the EM field. The AR device can combine the output of the pose sensor and the EM tracking system to reduce drift in the estimated pose of the user input device or to transform the pose into a world coordinate system used by the AR device. The AR device can utilize a Kalman filter to combine the output of the pose sensor and the EM tracking system.

An apparatus and method for determining position and orientation (PnO) of an object within an environment and for automatically determining a hemisphere of the object relative to a source location using an electromagnetic tracking system and a non-magnetic tracking device. The method involves seeding two candidate PnO solutions, one in each hemisphere, based on initial data from the magnetic tracker. Then, as the sensor moves within the tracking volume, both the magnetic tracker and the non-magnetic tracking device are used to track changes in each of the candidate PnO solutions and to determine a correct one of the candidate PnO solutions.

A method and apparatus for reducing magnetic tracking error in the position and orientation determined in a magnetic tracking system having a magnetic field generator. In some embodiments, the measured position and orientation of a sensor is compared to an expected theoretical position and orientation. Any error is assumed to be from “floor distortion,” i.e., eddy currents in the floor caused by the magnetic field generated by the magnetic field transmitter. The floor distortion is modeled as being caused by eddy currents caused by a second magnetic field transmitter that is a reflection of the actual transmitter. An algorithm iteratively searches over a parameter space to minimize the difference between the measured position and orientation and the theoretical position and orientation, and applies a correction to the measured position and orientation. The measurements and corrections of the position and orientation run in real-time with no additional hardware or calibration required.

A calibration device comprising: a plurality of magnetic sensors positioned at the calibration device, the plurality of magnetic sensors defining a space; a controller configured to be positioned in the space defined by the plurality of magnetic sensors, wherein the controller includes a magnetic transmitter; and one or more processors configured to: cause the magnetic transmitter to generate magnetic fields; receive signals from the plurality of magnetic sensors that are based on characteristics of the magnetic fields received at the plurality of magnetic sensors; calculate, based on the signals received from the plurality of magnetic sensors, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the magnetic transmitter; and determine whether the calculated positions and orientations of the plurality of magnetic sensors are within one or more threshold limits of known positions and orientations of the plurality of magnetic sensors.

A calibration device comprising: a plurality of magnetic sensors positioned at the calibration device, the plurality of magnetic sensors defining a space; a controller configured to be positioned in the space defined by the plurality of magnetic sensors, wherein the controller includes a magnetic transmitter; and one or more processors configured to: cause the magnetic transmitter to generate magnetic fields; receive signals from the plurality of magnetic sensors that are based on characteristics of the magnetic fields received at the plurality of magnetic sensors; calculate, based on the signals received from the plurality of magnetic sensors, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the magnetic transmitter; and determine whether the calculated positions and orientations of the plurality of magnetic sensors are within one or more threshold limits of known positions and orientations of the plurality of magnetic sensors.

A magnetic tracking system for determining position and orientation of an object in three-dimensional space, the system including an electromagnet assembly including first and second electromagnets that are coaxial, non-coincident, and spaced from each other by a fixed distance, at least one magnetometer positioned at a movable location relative to the electromagnet assembly and configured to measure three orthogonal components of a magnetic field vector, and a microcontroller unit operably connected to the at least one magnetometer. The microcontroller unit is configured to control measurement of magnetic fields by the at least one magnetometer and compute a relative position and orientation of the electromagnet assembly and the at least one magnetometer in five degrees of freedom using at least two equations with two unknowns and coordinate transformation equations relating the coordinate frames of the electromagnet assembly and the at least one magnetometer.

A magnetic tracking system for determining position and orientation of an object in three-dimensional space, the system including an electromagnet assembly including first and second electromagnets that are coaxial, non-coincident, and spaced from each other by a fixed distance, at least one magnetometer positioned at a movable location relative to the electromagnet assembly and configured to measure three orthogonal components of a magnetic field vector, and a microcontroller unit operably connected to the at least one magnetometer. The microcontroller unit is configured to control measurement of magnetic fields by the at least one magnetometer and compute a relative position and orientation of the electromagnet assembly and the at least one magnetometer in five degrees of freedom using at least two equations with two unknowns and coordinate transformation equations relating the coordinate frames of the electromagnet assembly and the at least one magnetometer.

Magnetic sensor synchronization techniques for pose tracking in artificial reality systems include managing and sending, by one or more primary magnetic sensors, a wireless synchronization signal to other magnetic sensors to trigger sensing sampling. The primary magnetic sensor may generate and send sensor data to a wireless data hub that operates as a sensor data collector and transmits data for pose tracking in the system. Each of the other (non-primary) magnetic sensors, in response to receiving the wireless synchronization signal, updates its sampling starting clock based on new synchronization timing. Each of the magnetic sensors sends generated sensor data to its corresponding primary sensor or wireless data hub according to a different schedule to avoid conflicts between the various magnetic sensors. The synchronization process may be repeated a number of times if a sensor fails to receive or respond to a synchronization signal.