Patent ID: 7089148
Filing Date: 2006-08-08
Classification: A61B,G01C,G06F

Abstract:
1. A method of tracking the orientation of a sensor, the method comprising: a) measuring an angular velocity of the sensor to generate angular rate values; b) integrating the angular rate values; c) normalizing the integrated angular rate values to produce an estimate of sensor orientation; d) measuring a magnetic field vector to generate local magnetic field vector values; e) measuring an acceleration vector to generate local gravity vector values; and f) correcting the estimate of sensor orientation using the local magnetic field vector and local gravity vector; g) determining a measurement vector from the local magnetic field vector values and the local gravity vector values; h) calculating a computed measurement vector from the estimate of sensor orientation; i) comparing the measurement vector with the computed measurement vector to generate an error vector that defines a criterion function; j) performing a mathematical operation without calculating the criterion function that results in the minimization of the criterion function and outputs an error estimate; k) integrating the error estimate; l) normalizing the integrated error estimate to produce a new estimate of sensor orientation; and m) repeating steps a)–m), wherein the new estimate of sensor orientation is used for h), calculating a computed measurement vector until tracking is no longer desired.