Distortion-immune position tracking using frequency extrapolation
First Claim
1. A method for tracking a position of an object in the presence of a metal distortion, comprising:
- establishing a predetermined frequency range;
using at least one field generator, generating alternating current (AC) magnetic fields at two or more frequencies in the predetermined frequency range in a vicinity of the object;
using a field sensor associated with the object, sensing the AC fields and producing corresponding AC data points that are indicative of amplitudes and directions of the AC fields at the field sensor in the predetermined frequency range, wherein at least some of the sensed AC fields are subject to the metal distortion;
extrapolating a dependence of the AC data points on the frequencies of the AC fields and fitting to a target frequency within the predetermined frequency range so as to determine the amplitudes and directions of the AC fields with a reduced level of the metal distortion, wherein the target frequency corresponds to an equivalent DC field strength that is substantially free of metal distortion; and
calculating position coordinates of the object relative to the at least one field generator responsively to the extrapolated data points based on the equivalent DC field strength.
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Abstract
A method for tracking a position of an object includes generating alternating current (AC) magnetic fields at two or more frequencies in a vicinity of the object using at least one field generator. The AC fields are sensed using a field sensor associated with the object. Corresponding AC data points that are indicative of amplitudes and directions of the AC fields at the field sensor are produced, wherein at least some of the sensed AC fields are subject to a distortion. A dependence of the AC data points on the frequencies of the AC fields is extrapolated to a target frequency so as to determine the amplitudes and directions of the AC fields with a reduced level of the distortion. Position coordinates of the object relative to the at least one field generator are calculated responsively to the extrapolated data points.
37 Citations
21 Claims
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1. A method for tracking a position of an object in the presence of a metal distortion, comprising:
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establishing a predetermined frequency range; using at least one field generator, generating alternating current (AC) magnetic fields at two or more frequencies in the predetermined frequency range in a vicinity of the object; using a field sensor associated with the object, sensing the AC fields and producing corresponding AC data points that are indicative of amplitudes and directions of the AC fields at the field sensor in the predetermined frequency range, wherein at least some of the sensed AC fields are subject to the metal distortion; extrapolating a dependence of the AC data points on the frequencies of the AC fields and fitting to a target frequency within the predetermined frequency range so as to determine the amplitudes and directions of the AC fields with a reduced level of the metal distortion, wherein the target frequency corresponds to an equivalent DC field strength that is substantially free of metal distortion; and calculating position coordinates of the object relative to the at least one field generator responsively to the extrapolated data points based on the equivalent DC field strength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for tracking a position of an object in the presence of a metal disturbance, comprising:
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at least one field generator, which is configured to generate alternating current (AC) magnetic fields at two or more frequencies within a predetermined frequency range in a vicinity of the object; a field sensor associated with the object, which is configured to sense the AC fields and to produce corresponding AC data points that are indicative of amplitudes and directions of the AC fields at the field sensor in the predetermined frequency range, wherein at least some of the sensed AC fields are subject to the metal distortion, wherein the target frequency corresponds to an equivalent DC field strength within the predetermined frequency range that is substantially free of metal distortion; and a processor, having the predetermined frequency stored therein and which is configured to extrapolate a dependence of the AC data points on the frequencies of the AC fields and fit to a target frequency so as to determine the amplitudes and directions of the AC fields with a reduced level of the metal distortion, and to calculate position coordinates of the object relative to the at least one field generator responsively to the extrapolated data points based on the equivalent DC field strength. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A system for tracking a position of an object in the presence of a metal disturbance, the system comprising at least one field generator and field sensor and a processor having a predetermined frequency range stored therein, the processor configured to control the at least one field generator so as to generate alternating current (AC) magnetic fields at two or more frequencies in the predetermined frequency range in a vicinity of the object,
to accept from the field sensor associated with the object AC data points indicative of amplitudes and directions of the respective AC fields sensed by the field sensor, wherein at least some of the sensed AC fields are subject to the metal distortion, to extrapolate a dependence of the AC data points on the frequencies of the AC fields and fit to a target frequency so as to determine the amplitudes and directions of the AC fields with a reduced level of the metal distortion, wherein the target frequency corresponds to an equivalent DC field strength within the predetermined frequency range that is substantially free of metal distortion; - and
to calculate position coordinates of the object relative to the at least one field generator responsively to the extrapolated data points based on the equivalent DC field strength.
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Specification