Patent ID: 7285951

Claim:
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; 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; and outputting a signal representing the position and orientation of the mobile object based on the deduced magnetic fields.