Method and device for magnetic measurement of the position and orientation of a mobile object relative to a fixed structure
First Claim
1. A method of magnetic measurement of the position and the orientation of a mobile object with respect to a fixed structure, in which a first emitter assembly includes at least two orthogonal coils for emitting magnetic fields, integral with said fixed structure, which define a reference frame, and means of emission for injecting predetermined emission currents into said coils at first frequencies, in which a second sensor assembly includes at least two orthogonal coils for detecting magnetic fields, integral with said mobile object, sensor channels with servocontrol loops for producing in feedback coils coupled to said detection coils feedback magnetic fields by injection of measurement currents and a calibration channel for elaborating at least one calibration voltage, and in which at least one acquisition channel is provided for extracting measurement values of said emission channels, said sensor channels and said calibration channel and means of calculation and of processing estimate, on the basis of said measurement values, the magnetic fields detected in the second sensor assembly and deduce therefrom the position and the orientation of said mobile object in said reference frame, wherein the calibration voltage comprises only terms with at least two frequencies distinct from said first frequencies and comprising:
- injecting calibration currents and voltages into said channels of the sensor so as to produce calibration measurement values identified by their frequency, estimating by the means of calculation the transfer function of each of the sensor channels and deducing by said means of calculation the magnetic fields detected on the basis of said measurement values and of the inverse of said estimated transfer functions.
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Accused Products
Abstract
A method and device for magnetic measurement of the position and orientation of a mobile object relative to a fixed structure are described. The device comprises, integral with the structure, a magnetic fields emitter assembly having three orthogonal emission coils defining a reference frame and a sensor assembly, integral with the mobile object, having three channels for measuring the field received on three orthogonal detection coils, these channels each incorporating a feedback loop providing an output voltage and a measurement current. A calibration voltage, at frequencies differing from the useful frequencies of the fields, is injected into the channels of the sensor without disturbing the continuous measurement by measurement acquisition channels, while a calibration current is superimposed on the measurement resistors. It is thus possible to identify the variable components of the system and correct the measurements through the inverse of the respective transfer functions of the channels of the sensor.
25 Citations
7 Claims
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1. A method of magnetic measurement of the position and the orientation of a mobile object with respect to a fixed structure, in which a first emitter assembly includes at least two orthogonal coils for emitting magnetic fields, integral with said fixed structure, which define a reference frame, and means of emission for injecting predetermined emission currents into said coils at first frequencies, in which a second sensor assembly includes at least two orthogonal coils for detecting magnetic fields, integral with said mobile object, sensor channels with servocontrol loops for producing in feedback coils coupled to said detection coils feedback magnetic fields by injection of measurement currents and a calibration channel for elaborating at least one calibration voltage, and in which at least one acquisition channel is provided for extracting measurement values of said emission channels, said sensor channels and said calibration channel and means of calculation and of processing estimate, on the basis of said measurement values, the magnetic fields detected in the second sensor assembly and deduce therefrom the position and the orientation of said mobile object in said reference frame, wherein the calibration voltage comprises only terms with at least two frequencies distinct from said first frequencies and comprising:
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injecting calibration currents and voltages into said channels of the sensor so as to produce calibration measurement values identified by their frequency, estimating by the means of calculation the transfer function of each of the sensor channels and deducing by said means of calculation the magnetic fields detected on the basis of said measurement values and of the inverse of said estimated transfer functions. - View Dependent Claims (2, 3, 4)
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5. A device for the magnetic measurement of the position and the orientation of a mobile object with respect to a fixed structure, comprising:
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a first emitter assembly including at least two orthogonal coils for emitting magnetic fields, integral with said fixed structure and defining a reference frame, and means of emission for injecting predetermined currents into said coils at first frequencies and constituting with said coils at least two emission channels;
a second sensor assembly including at least two orthogonal coils for detecting magnetic fields, integral with said mobile object, means of measurement by servocontrol loops, for producing in feedback coils coupled to said detection coils feedback magnetic fields by injection of measurement currents and for constituting with said detection coils at least two sensor channels, and means of calibration comprising a calibration channel for elaborating at least one calibration voltage at second frequencies;
at least one acquisition channel for measurements for extracting measurement values of said emission channels, said sensor channels and said calibration channel; and
means of calculation and processing for estimating, on the basis of said measurement values, the magnetic fields detected in the second sensor assembly and deducing therefrom the position and the orientation of said mobile object in said reference frame, wherein said second frequencies are distinct from said first frequencies, in that said means of calibration are provided so as to inject calibration currents and voltages into said sensor channels so as to produce calibration measurement values identified by their frequencies and addressed to said means of calculation by the acquisition channel or channels and in that said means of calculation and processing are provided so as to estimate the transfer function of each of the sensor channels and to deduce the magnetic fields detected from said measurement values and from the inverse of said estimated transfer functions. - View Dependent Claims (6, 7)
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Specification