Self-leveling magnetic source
AssigneeALKEN Inc.
InventorsRobert F. Higgins, Allan G. Rodgers, Jr.
Life of this patent
Estimating the term…
Abstract
A method for calibrating a magnetic source of an electromagnetic tracking system for tracking a position and orientation of an object using an inertial motion unit (IMU) mounted to the magnetic source and aligned with the coil array of magnetic source. Pitch and rolls angles of the coil array are calibrated using the IMU.
Claims16
A method for calibrating a transmitter circuit of an electromagnetic tracking system for tracking a position and orientation of a first object relative to a second object, wherein the transmitter circuit includes a plurality of transmitter coils aligned at different transmitter axes and an actuating circuit configured to actuate the transmitter coils to generate a time-multiplexed or frequency-multiplexed magnetic field, wherein a receiver circuit including a plurality of sensing elements aligned at different receiver axes is mounted to the first object, and wherein the sensing elements are configured to detect respective components of the magnetic field generated by the plurality of transmitter coils, the method comprising:
- aligning an azimuth angle of the transmitter circuit to a reference point so that an azimuth angle of an inertial motion unit (IMU) mounted to the transmitter circuit is aligned within a reference frame of the second object, wherein each of a pitch angle offset and a roll angle offset of the IMU relative to a gravitational force is adjusted so that a reference frame of the IMU is aligned with a reference frame of the transmitter circuit;
- and
- mounting the transmitter circuit to the second object while the azimuth angle of the IMU is aligned within the reference frame of the second object.
A method for calibrating an orientation of a first element of an electromagnetic tracking system pair for tracking a position and orientation of a second element of the electromagnetic tracking system pair, wherein the first element includes a plurality of magnetic field sensing or transmitting elements adapted to sense or transmit magnetic field components along three mutually orthogonal magnetic field axes in a first frame of reference, and an inertial motion unit (IMU) adapted to detect at least one of linear acceleration or angular rotation along first, second and third IMU axes in a second frame of reference, the second frame of reference having a known orientation relative to the first frame of reference, the method comprising:
- affixing the second element of the electromagnetic tracking system pair to a base having a fixed orientation in a third frame of reference while the base has a known orientation relative to a gravitational force, such that that a first IMU axis is aligned with a reference point of the third frame of reference within a plane having a known angle relative to the gravitational force;
- while the second element of the electromagnetic tracking system pair is affixed to the base, measuring, by the inertial motion unit (IMU), the gravitational force along the second and third IMU axes;
- and
- based at least in part on the measured gravitational force along the second and third IMU axes, performing at least one of:
- determining at least part of a transform between the second frame of reference and the third frame of reference;
- or
- mechanically adjusting an orientation of the second element of the electromagnetic tracking system pair relative to the base so that the second frame of reference lies in a predetermined orientation relative to the third frame of reference of the platform, and affixing the second element of the electromagnetic tracking system pair to the base in the predetermined orientation.
Dependencies are inferred from the claim text.