System and method for electromagnetic navigation in the vicinity of a metal object
First Claim
1. A system for determining the position and orientation of an object, said system comprising:
- a transmitter assembly comprising at least two transmitters, each said transmitter capable of simultaneously emitting plural magnetic fields at different frequencies, wherein said transmitters are configured to;
simultaneously emit navigation magnetic fields, wherein the navigation magnetic field emitted by each said transmitter is at a frequency different than the frequencies of the navigation magnetic fields emitted by the other said transmitters; and
with each said transmitter, simultaneously with the navigation magnetic field emitted by said transmitter, emit a plurality of surveillance magnetic fields, the surveillance magnetic fields being at different frequencies and at frequencies less than the frequencies at which said transmitters emit the navigation magnetic fields wherein the surveillance magnetic fields are sequentially emitted by said transmitters so that, after a first said transmitter emits the surveillance magnetic fields, a second said transmitter emits the surveillance magnetic fields;
at least two sensors, each sensor configured to measure the strength of a composite magnetic field that is the sum of the navigation magnetic fields and the surveillance magnetic fields emitted by said transmitters that are received by the sensor and to generate a sensor signal representative of the strength of the received composite magnetic field; and
a processor connected to said sensor to receive the sensor signals, said processor is further configured to;
for each sensor signal, based on the sensor signal from said sensor, determine the strengths of the navigation magnetic fields and the strengths of the surveillance magnetic fields received by said sensor;
based on the strengths of the surveillance magnetic fields that are transmitted with each navigation magnetic field, determine the strength of eddy current induced magnetic field as a function of field frequency;
for the navigation magnetic field emitted with the surveillance magnetic fields, based on the strength of the eddy current induced magnetic fields as a function of field frequency and the frequency of the navigation magnetic field, determine an error value for the navigation magnetic field;
for the navigation magnetic field emitted with the surveillance magnetic fields received by each sensor, based on the strength of the navigation magnetic field and the error value for the navigation magnetic field, generate a corrected measurement of navigation magnetic field strength; and
based on the corrected measurements of navigation magnetic field strengths for the plurality of navigation magnetic fields that are received by said plurality of sensors, compute position and orientation data for the sensors.
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Abstract
A system and method for performing object localization based on the emission of electromagnetic fields. The electromagnetic fields are simultaneously emitted from different transmitters. One electromagnetic field is emitted at a base frequency; the remaining waves are emitted at frequencies that are harmonics of the base frequency. The composite magnetic fields are measured by sensors. The signal generated by each sensor is subject to a Fourier analysis to determine the strengths of the individual electromagnetic fields forming the composite electromagnetic field. These individual measure field strength data are then used to determine the position and orientation of the sensors relative to the transmitters.
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Citations
20 Claims
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1. A system for determining the position and orientation of an object, said system comprising:
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a transmitter assembly comprising at least two transmitters, each said transmitter capable of simultaneously emitting plural magnetic fields at different frequencies, wherein said transmitters are configured to; simultaneously emit navigation magnetic fields, wherein the navigation magnetic field emitted by each said transmitter is at a frequency different than the frequencies of the navigation magnetic fields emitted by the other said transmitters; and with each said transmitter, simultaneously with the navigation magnetic field emitted by said transmitter, emit a plurality of surveillance magnetic fields, the surveillance magnetic fields being at different frequencies and at frequencies less than the frequencies at which said transmitters emit the navigation magnetic fields wherein the surveillance magnetic fields are sequentially emitted by said transmitters so that, after a first said transmitter emits the surveillance magnetic fields, a second said transmitter emits the surveillance magnetic fields; at least two sensors, each sensor configured to measure the strength of a composite magnetic field that is the sum of the navigation magnetic fields and the surveillance magnetic fields emitted by said transmitters that are received by the sensor and to generate a sensor signal representative of the strength of the received composite magnetic field; and a processor connected to said sensor to receive the sensor signals, said processor is further configured to; for each sensor signal, based on the sensor signal from said sensor, determine the strengths of the navigation magnetic fields and the strengths of the surveillance magnetic fields received by said sensor; based on the strengths of the surveillance magnetic fields that are transmitted with each navigation magnetic field, determine the strength of eddy current induced magnetic field as a function of field frequency; for the navigation magnetic field emitted with the surveillance magnetic fields, based on the strength of the eddy current induced magnetic fields as a function of field frequency and the frequency of the navigation magnetic field, determine an error value for the navigation magnetic field; for the navigation magnetic field emitted with the surveillance magnetic fields received by each sensor, based on the strength of the navigation magnetic field and the error value for the navigation magnetic field, generate a corrected measurement of navigation magnetic field strength; and based on the corrected measurements of navigation magnetic field strengths for the plurality of navigation magnetic fields that are received by said plurality of sensors, compute position and orientation data for the sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of determining the position and orientation of an object, said method including the steps of:
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simultaneously emitting navigation magnetic fields from a plurality of transmitters wherein, the navigation magnetic field emitted by each transmitter is at different frequency than the navigation magnetic fields emitted by the other transmitters; when emitting the navigation magnetic fields from the transmitters, from each transmitter, simultaneously emitting with the navigation magnetic field a plurality of surveillance magnetic fields, wherein, the surveillance magnetic fields are emitted at different frequencies and at frequencies less than the frequencies at which the transmitters emit the navigation magnetic fields wherein, the surveillance magnetic fields are emitted sequentially by the transmitters so that, after a first transmitter emits the surveillance magnetic fields, a second transmitter emits the surveillance magnetic fields; simultaneously measuring the strengths of the magnetic fields with a plurality of sensors wherein, each sensor receives the navigation magnetic fields simultaneously emitted by the transmitters and the surveillance magnetic fields sequentially emitted by the transmitters; determining the strengths of each navigation magnetic field and surveillance magnetic field received by each sensor; based on the strengths of the surveillance magnetic fields measured by a sensor, determining the strength of eddy current induced magnetic fields measured by the sensor as a function of field frequency; for the navigation magnetic field emitted by a transmitted when the transmitter emits the surveillance magnetic fields, based on the strength of the eddy current induced magnetic fields as a function of field frequency and the frequency of the navigation magnetic field, determining an error value for the navigation magnetic field measured by the sensor; for the navigation magnetic field emitted by a transmitter when the transmitter emits surveillance magnetic fields, based on the determined strength of the navigation magnetic field received by a sensor and the error value, generating a corrected measurement of navigation magnetic field strength; and based on the corrected measurements of navigation magnetic field strength for the navigation magnetic fields emitted by the transmitters and received by the sensors, compute position and orientation data for the sensors. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification