Penumbra, Inc.

Michael D Collins

Oded Y Zur

Alejandro Santiago Diaz

Ron Barak

Amir Rubin

Cameron J Mahon

Ran Bar-On

Branislav Vasilijevic

A method and apparatus for determining pose of a transmitter, and by extension the pose of one or more receivers, in an electromagnetic tracking system when the transmitter is allowed to move freely in the physical environment. The method operates in a system that incorporates two separate tracking technologies and an Inertial Measurement Unit, one determining the pose of a device relative to a global reference frame and another determining the pose of the same device relative to a local reference frame, thereby avoiding the latency problem and resulting inaccuracy of pose determinations of known prior approaches.

Orienting a moving electromagnetic tracking reference frame via external localizing data on an electromagnetic sensor using IMU data

Automatic synchronization of a magnetic field transmitter and receiver is performed to resolve phase ambiguity so that phase information, used in determining the position and orientation of the receiver, may be derived and maintained. Inertial measurement unit (IMU) information is used to infer gravity-relative orientations of the transmitter and receiver, which are then used as constraints in the synchronization process to determine the position and orientation of the receiver from all four possible solutions or variations. The variation that best conforms to the IMU orientations is chosen as the sync candidate.

Automatically synchronizing a transmitter and receiver in a magnetic tracking system using information from an inertial measurement unit

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.

Method and apparatus for reducing magnetic tracking error due to floor distortion

A method and apparatus for reducing magnetic tracking error in the position and orientation determined in an electromagnetic tracking system is disclosed. In some embodiments, a corrected position and orientation is blended with an uncorrected position and orientation based upon the calculated probability of each. To determine a corrected position and orientation, data from an IMU in the receiver is used to obtain a constraint on the orientation. In other embodiments, the amount of detected error due to electromagnetic distortion is measured. Any error is first assumed to be from 'floor distortion,' and a correction is applied. If the error is still deemed too great, a constraint is again obtained from IMU data. Using this constraint, another correction for the distortion is made. The solution from this correction may be blended with a standard solution and the solution from the floor distortion to arrive at a final solution.

Method and apparatus for reducing magnetic tracking error

A system and method for performing synchronization of a magnetic field transmitter and receiver to resolve received signal phase ambiguity based upon the phases of the magnetic fields. Three orthogonal field frequencies are selected. A Fourier transform extracts the sine and cosine of the received signal, which provides the received signal phases and results in a complex signal matrix ('Sigmat'). A search is made for a phase rotation of the frequencies to achieve convergence of the Sigmat at a point it is real-valued; the search may be limited by aligning the Sigmat such that the major element becomes real-valued and rotating the other two frequencies. The correct phase is the one in which the Sigmat has a positive determinant and minimizes any remaining imaginary portion. A transmitter and receiver may be calibrated to account for any analog phase shift. Distortion of the magnetic field may also be detected and corrected.

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Santa Cruz, CA, United States of America

Michael D Collins