A system for tracking and positioning a moving object, the system including a plurality of transmitters operative to transmit alternating electromagnetic fields within a three-dimensional space and at least one sensor arranged to be fixed to at least one corresponding portion of a moving object whose position it is sought to monitor. Each of said at least one sensors includes an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of the alternating electromagnetic fields, an accelerometer to independently measure at least one component of the acceleration of the moving object; and a digital signal processor. The digital signal processor is adapted to store at least one characteristic of the electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer, and to transmit the stored characteristics to a Kalman filter, and to compute therefrom an estimate of at least one component of the position and orientation of the moving object.
RELATED APPLICATIONS
This application may be related to (1) U.S. patent application Ser. No. 09/384,314, filed Aug. 27, 1999, LOCALIZATION AND TRACKING SYSTEM; (2) U.S. patent application Ser. No. 09/345,189, filed Jun. 30, 1999, A SYSTEM FOR THREE DIMENSIONAL POSITIONING AND TRACKING; (3) U.S. patent Application Ser. No. 09/503,436, filed Feb. 14, 2000, A SYSTEM FOR THREE DIMENSIONAL POSITIONING AND TRACKING WITH DYNAMIC RANGE EXTENSION.
One embodiment the invention includes a method of determining an orientation of a sensor. The method includes measuring a local magnetic field vector and a local gravity vector and using those measurements to determine the orientation of the sensor. Embodiments can include measuring the magnetic field vector and the local gravity vector using quaternion coordinates. Another embodiment includes measuring a local magnetic field vector, a local gravity vector, and the angular velocity of the sensor. These three vectors are processed to determine the orientation of the sensor. In one embodiment the three vectors can all be measured in quaternion coordinates. Another method embodiment includes determining a local gravity vector by providing a acceleration detector, moving the detector from a start point to an end point over a time period, and summing acceleration measurements over the time period. The local gravity vector is calculated using the summed acceleration measurements.
An unknown location for a transmitter/receiver is determined using a calibration process. An area is established with reference receivers at known locations and a mobile transmitter provides a location signal. An alternative embodiment uses reference transmitters and a mobile receiver. For calibration, the transmitter is placed at multiple measured locations and signal measurements are taken to generate a calibration map. Multiple signal measurements may be taken at each receiver, and multiple receivers may be used. In one embodiment, signal measurements include a near-field phase. In operation, one or more location signals are measured at one or more receivers. The measured signals are compared with the calibration maps to generate a set of comparison maps which are combined to generate a likelihood map. A likely region and most likely location are determined from the likelihood map and may be displayed relative to a map of the environment.
A motion capture system includes a motion capture detecting device with sensor coils that are sequentially selected by a control section. Signals are communicated between respective input coils of input elements of an input device and the sensor coils by electromagnetic coupling. The signals received by each of the selected coils are detected by a detecting section. Three-dimensional coordinates and directions of each of the input elements are calculated by a control section so that the input elements become continuous, based on the detected signals by the detecting section.
A system and method for electromagnetic position determination utilizing a calibration process. For calibration, a transmitter is positioned at multiple locations in an area of interest and multiple receivers receive and record signal characteristics from the transmitter to generate a calibration data set. The unknown position of a transmitter may be determined by receiving signals from the transmitter by multiple receivers. A locator data set is generated based on the comparison between two received signal characteristics determined for each receiver. The locator data set is compared with the calibration data set to determine the unknown position. In one embodiment, the signal comparisons are the differences between electric and magnetic field phase. Further embodiments utilize signal amplitude differences. A reciprocal method utilizing a single receiver and multiple transmitter locations is disclosed. A further method is disclosed for determining position by utilizing signals available from existing installed wiring such as power wiring.
A system and method for electromagnetic position determination utilizing a calibration process. For calibration, a transmitter is positioned at multiple locations in an area of interest and multiple receivers receive and record signal characteristics from the transmitter to generate a calibration data set. The unknown position of a transmitter may be determined by receiving signals from the transmitter by multiple receivers. A locator data set is generated based on the comparison between two received signal characteristics determined for each receiver. The locator data set is compared with the calibration data set to determine the unknown position. In one embodiment, the signal comparisons are the differences between electric and magnetic field phase. Further embodiments utilize signal amplitude differences. A reciprocal method utilizing a single receiver and multiple transmitter locations is disclosed. A further method is disclosed for determining position by utilizing signals available from existing installed wiring such as power wiring.
