Method and apparatus for reducing magnetic tracking error

A method of reducing magnetic tracking error in a determined position and orientation of a receiver in an electromagnetic tracking system, comprising:

• generating a magnetic field from a plurality of source magnetic coils in a transmitter;
• generating magnetic sensor data by sensing the magnetic field using a plurality of sensor magnetic coils in a receiver;
• generating inertial measurement data from first and second inertial measurement units, one inertial measurement unit in the transmitter and the other inertial measurement unit in the receiver;
• determining by a processor that there is error in a determined position and orientation of the receiver relative to the transmitter as represented by a first signal matrix computed using the magnetic sensor data from the sensor magnetic coils;
• determining by the processor that the error in the position and orientation of the receiver represented by the first signal matrix exceeds a predetermined threshold;
• determining by the processor a first correction factor to compensate for the error in the position and orientation of the receiver relative to the transmitter as represented by the first signal matrix, and computing by the processor a second signal matrix by applying the first correction factor to the first signal matrix;
• determining by the processor that error in the position and orientation of the receiver represented by the second signal matrix exceeds the predetermined threshold;
• determining by the processor a second correction factor to compensate for the error in the position and orientation of the receiver relative to the transmitter as represented by the second signal matrix, and computing by the processor a third signal matrix by applying the second correction to the second signal matrix;
• and
• determining by the processor an error-corrected position and orientation of the receiver by blending positions and orientations derived from the first, second and third signal matrices.

A non-transitory computer readable storage medium having embodied thereon instructions for causing a computing device to execute a method for reducing magnetic tracking error in the position and orientation of a receiver in an electromagnetic tracking system, the method comprising:

• determining by a processor that there is error in a determined position and orientation of the receiver relative to the transmitter as represented by a first signal matrix created using the magnetic sensor data from the sensor magnetic coils;
• determining by the processor that the error in the position and orientation of the receiver represented by the first signal matrix exceeds a predetermined threshold;
• determining by the processor a first correction factor to compensate for the error in the position and orientation of the receiver represented by the first signal matrix, and computing by the processor a second signal matrix by applying the first correction factor to the first signal matrix;
• determining by the processor that error in the position and orientation of the receiver represented by the second signal matrix exceeds the predetermined threshold;
• determining by the processor a second correction factor to compensate for the error in the position and orientation of the receiver represented by the second signal matrix, and computing by the processor a third signal matrix by applying the second correction to the second signal matrix;
• and
• determining by the processor an error-corrected position and orientation of the receiver by blending positions and orientations derived from the first, second and third signal matrices.

A system for reducing magnetic tracking error in a determined position and orientation of a receiver in an electromagnetic tracking system, comprising:

• a transmitter having a plurality of source magnetic coils configured to generate a magnetic field, and an inertial measurement unit;
• a receiver having a plurality of sensor magnetic coils configured to sense the magnetic field and generate magnetic sensor data, and an inertial measurement unit;
• and
• a processor configured to:
• determine that there is error in the determined position and orientation of the receiver relative to the transmitter as represented by a first signal matrix created using the magnetic sensor data from the sensor magnetic coils;
• determine that the error in the position and orientation of the receiver represented by the first signal matrix exceeds a predetermined threshold;
• determine a first correction factor to compensate for the error in the position and orientation of the receiver represented by the first signal matrix, and compute a second signal matrix by applying the first correction factor to the first signal matrix;
• determine that error in the position and orientation of the receiver represented by the second signal matrix exceeds the predetermined threshold;
• determine a second correction factor to compensate for the error in the position and orientation of the receiver represented by the second signal matrix, and compute a third signal matrix by applying the second correction to the second signal matrix;
• determine an error-corrected signal matrix by blending the first, second and third signal matrices;
• and
• derive an error-corrected position and orientation of the receiver from the error-corrected signal matrix.

A method of reducing magnetic tracking error in a determined position and orientation of a receiver in an electromagnetic tracking system, comprising:

• generating a magnetic field from a plurality of source magnetic coils in a transmitter;
• generating magnetic sensor data by sensing the magnetic field using a plurality of sensor magnetic coils in a receiver;
• generating inertial measurement data from first and second inertial measurement units, one inertial measurement unit in the transmitter and the other inertial measurement unit in the receiver;
• determining by a processor that there is error in a determined position and orientation of the receiver relative to the transmitter as represented by a first signal matrix computed using the magnetic sensor data from the sensor magnetic coils;
• determining by the processor that the error in the position and orientation of the receiver represented by the first signal matrix exceeds a predetermined threshold;
• determining by the processor a first correction factor to compensate for the error in the position and orientation of the receiver relative to the transmitter as represented by the first signal matrix, and computing by the processor a second signal matrix by applying the first correction factor to the first signal matrix;
• determining by the processor that error in the position and orientation of the receiver represented by the second signal matrix exceeds the predetermined threshold;
• determining by the processor a second correction factor to compensate for the error in the position and orientation of the receiver relative to the transmitter as represented by the second signal matrix, and computing by the processor a third signal matrix by applying the second correction to the second signal matrix;
• determining by the processor an error-corrected signal matrix by blending the first, second and third signal matrices;
• and
• deriving an error-corrected position and orientation of the receiver from the error-corrected signal matrix.

A system for reducing magnetic tracking error in a determined position and orientation of a receiver in an electromagnetic tracking system, comprising:

• a transmitter having a plurality of source magnetic coils configured to generate a magnetic field;
• a receiver having a plurality of sensor magnetic coils configured to sense the magnetic field and generate magnetic sensor data, and an inertial measurement unit;
• and
• a processor configured to:
• calculate a proportion of error in an uncorrected position and orientation of the receiver relative to the transmitter as represented by a signal matrix created using the magnetic sensor data from the sensor magnetic coils;
• determine a corrected position and orientation of the receiver relative to the transmitter as represented by a signal matrix created using the magnetic sensor data and constrained by data from the inertial measurement unit;
• calculate a proportion of error in the corrected position and orientation of the receiver relative to the transmitter;
• determine a probability for the uncorrected position and orientation of the receiver and the corrected position and orientation of the receiver using the proportions of error;
• and
• determine a position and orientation of the receiver relative to the transmitter by interpolating between the uncorrected position and orientation and the corrected position and orientation based upon the determined probabilities of each.

A method of reducing magnetic tracking error in a determined position and orientation of a receiver in an electromagnetic tracking system, comprising:

• generating a magnetic field from a plurality of source magnetic coils in a transmitter;
• generating magnetic sensor data by sensing the magnetic field using a plurality of sensor magnetic coils in a receiver;
• generating inertial measurement data from an inertial measurement unit in the receiver;
• calculating by a processor a proportion of error in an uncorrected position and orientation of the receiver relative to the transmitter as represented by a signal matrix created using the magnetic sensor data from the sensor magnetic coils;
• determining by the processor a corrected position and orientation of the receiver relative to the transmitter as represented by a signal matrix created using the magnetic sensor data and constrained by the inertial measurement data;
• calculating by the processor a proportion of error in the corrected position and orientation of the receiver relative to the transmitter;
• determining by the processor a probability for the uncorrected position and orientation of the receiver and the corrected position and orientation of the receiver using the proportions of error;
• and
• determining by the processor a position and orientation of the receiver relative to the transmitter by interpolating between the uncorrected position and orientation and the corrected position and orientation based upon the determined probabilities of each.

A non-transitory computer readable storage medium having embodied thereon instructions for causing a computing device to execute a method for reducing magnetic tracking error in the position and orientation of a receiver in an electromagnetic tracking system, the method comprising:

• receiving magnetic sensor data representing the sensing by sensor magnetic coils in the receiver of a magnetic field generated by source magnetic coils in a transmitter, and inertial measurement data from an inertial measurement unit in the receiver;
• calculating a proportion of error in an uncorrected position and orientation of the receiver relative to the transmitter as represented by a signal matrix created using the magnetic sensor data from the sensor magnetic coils;
• determining a corrected position and orientation of the receiver relative to the transmitter as represented by a signal matrix created using the magnetic sensor data and constrained by the inertial measurement data;
• calculating by the processor a proportion of error in the corrected position and orientation of the receiver relative to the transmitter;
• determining a probability for the uncorrected position and orientation of the receiver and the distortion-corrected position and orientation of the receiver using the proportions of error;
• and
• determining a position and orientation of the receiver relative to the transmitter by interpolating between the uncorrected position and orientation and the distortion-corrected position and orientation based upon the determined probabilities of each.