Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2001-03-29
2003-09-02
Shah, Kamini (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C324S207170, C342S463000, C600S409000, C600S424000
Reexamination Certificate
active
06615155
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to vector field tracking of a moving object and, more particularly, to a method of tracking a moving object with a small number (one or two) of vector field sensors attached thereto.
It is known to track the position and orientation of a moving object with respect to a fixed frame of reference, by equipping the moving object with a transmitter that transmits low frequency electromagnetic radiation, placing a receiver in a known and fixed position in the fixed frame of reference, and inferring the continuously changing position and orientation of the object from signals transmitted by the transmitter and received by the receiver. Equivalently, by the principle of reciprocity, the moving object is equipped with a receiver, and a transmitter is placed in a known and fixed position in the fixed frame of reference. Alternatively, the moving object is equipped with a generator that generates a static magnetic field, and a magnetometer is substituted for the receiver. Again, by the principle of reciprocity, the moving object may be equipped with a magnetometer, and a generator of a static magnetic field may be placed in a known and fixed position in the fixed frame of reference. Typically, the transmitter includes three orthogonal magnetic dipole transmitting antennas; the receiver includes three orthogonal magnetic dipole receiving sensors; and the transmitter and the receiver are sufficiently close to each other, and the frequencies of the signals are sufficiently low, that the signals are near field signals. Such orthogonal transmitting antennas also can be used to generate a static magnetic field; the magnetometer in that case typically is a three component vector magnetometer. Representative prior art patents in this field include U.S. Pat. No. 3,868,565, U.S. Pat. No. 3,983,474, U.S. Pat. No. 4,017,858 and U.S. Pat. No. 4,742,356, to Kuipers; U.S. Pat. No. 4,054,881, U.S. Pat. No. 4,314,251 and U.S. Pat. No. 4,346,384, to Raab; U.S. Pat. No. 4,287,809 and U.S. Pat. No. 4,394,831, to Egli et al.; U.S. Pat. No. 4,328,548, to Crow et al.; U.S. Pat. No. 4,396,885, to Constant; U.S. Pat. No. 4,613,866 and U.S. Pat. No. 4,849,692, to Blood; U.S. Pat. No. 4,737,794 and U.S. Pat. No. 5,307,072, to Jones; and U.S. Pat. No. 5,646,525, to Gilboa.
For the most part, these patents assume point dipole transmitters/generators and, in the electromagnetic embodiments, point dipole receivers. Jones (U.S. Pat. No. 4,737,794 and U.S. Pat. No. 5,307,072) and Egli et al. (U.S. Pat. No. 4,394,831) discuss multipole corrections to the basic point dipole model. Blood (U.S. Pat. No. 5,600,330), Acker et al. (U.S. Pat. No. 5,752,513) and Ben-Haim et al. (WO 96/05768) also treat spatially extended transmitters/receivers.
Also, for the most part, the prior art in this field requires a simultaneous determination of both the position and the orientation of the moving object. Acker, in U.S. Pat. No. 5,729,129, shows how the theoretical expressions describing the fields produced by point dipoles can be used to solve for the position and orientation of the moving object, given any combination of point dipole transmitters and point dipole receivers that provide enough equations to solve for all six unknowns (three position coordinates and three orientation angles). Similar theoretical expressions for the fields produced by spatially extended generators and transmitters can be obtained based on Ampere's law (Blood, U.S. Pat. No. 5,600,330) or the Biot-Savart law (Gilboa et al., EP 922,966). Blood also shows how the position alone of the object can be obtained, without also computing the orientation of the object, in the case of three magnetic field generators and a three-component magnetometer. Gilboa et al., EP 922,966, provide expressions for the three position coordinates and the three orientation angles of a three component receiver in terms of signals received from three spatially extended transmitters.
There are circumstances in which the restricted space, in which the moving object moves, imposes the constraint that the moving object can be equipped with only one transmitter component or only one receiver component. For example, a borehole logging tool must be slender enough to move through a borehole, and a catheter must be slender enough to move through a blood vessel. In both these cases, there is room in the object for only one transmitter or receiver coil, aligned with the longitudinal axis of the object. Rorden et al. (U.S. Pat. No. 4,710,708), Bladen et al. (WO 94/04938), Dumoulin et al. (U.S. Pat. No. 5,377,678) and Schneider (U.S. Pat. No. 6,073,043) all show how to derive the combined position and orientation of the object from signals transmitted by a single component transmitter on board the object or from signals received by a single component receiver on board the object. Bladen et al. are of particular note as showing, in the case of point dipole transmitters and a single component receiver, how an imprecise estimate of the object's position can be calculated independently of the object's orientation; this imprecise estimate then is used as an initial position estimate in an iterative combined calculation of both position and orientation. Nevertheless, the prior art does not teach how the exact position of a single-component receiver can be obtained without also computing the orientation of the receiver. Furthermore, even in the case of a three component receiver and a three component transmitter, algorithms such as Blood's for determining only the position of the receiver presuppose the availability of theoretical expressions for the fields generated by the transmitters.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method of tracking an object that moves in three dimensions, including the steps of: (a) providing the object with at least one vector field component sensor for measuring a respective component of a vector field; (b) for each at least one vector field component sensor, empirically determining parameters of a set of equations that relate the respective component only to a position of the object with respect to a reference frame; (c) providing a plurality of vector field generators for generating respective instances of the vector field, each generator having a fixed respective position in the reference frame; (d) for each generator: (i) generating the respective instance of the vector field, and (i) for each at least one sensor, measuring the respective component of the respective instance of the vector field; and (e) solving the set of equations for the position of the object.
According to the present invention there is provided a method of tracking an object that moves in three dimensions, including the steps of: (a) providing the object with at most two vector field component sensors for measuring respective components of a vector field; (b) for each at most two vector field component sensors, determining parameters of a set of equations that relate the respective component only to a position of the object with respect to a reference frame; (c) providing at least three vector field generators for generating respective instances of the vector field, each generator having a fixed respective position in the reference frame; (d) for each generator: (i) generating the respective instance of the vector field, and (i) for each at most two sensors, measuring the respective component of the respective instance of the vector field; and (e) solving the set of equations for the position of the object.
According to the present invention there is provided a system for tracking an object that moves in three dimensions, including: (a) at least one vector field component sensor, associated with the object, for measuring a respective component of a vector field; (b) a processor for solving a set of equations that relate, for each at least one sensor, the respective component of the vector field only to a position of the object with respect to a reference frame; (c) a memor
Friedman Mark M.
Shah Kamini
Super Dimension Ltd.
LandOfFree
Object tracking using a single sensor or a pair of sensors does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Object tracking using a single sensor or a pair of sensors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Object tracking using a single sensor or a pair of sensors will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3018949