A new method for magnetic position and orientation tracking

The method is based on two-axis generation of a quasi-static rotating magne tic field and three-axis sensing. Two mutually orthogonal coils fed with ph ase-quadrature currents comprise the excitation source, which is equal to a mechanically rotating magnetic dipole. The resulting excitation field rota tes elliptically at any position in the near-field region. The ac part of t he squared field magnitude is a sinusoidal wave at twice the excitation fre quency. The following set of parameters uniquely characterize the excitatio n at the sensor's position: the phase of the squared field waveform, relati ve to the excitation currents, the minimum field value, the ratio of the fi eld extremes, and the orientation of the excitation field plane. Simple and explicit analytical expressions are given which relate the first three par ameters to the azimuth, elevation, and distance from the source to the sens or, respectively. The orientation of the sensor axes, relative to the plane of the excitation, can easily be determined by comparing the phase and amp litude of the measured signals against the phase and amplitude of the excit ation field at the sensor's position. Apart from simplicity, the proposed m ethod increases the speed of tracking; a single period of excitation is in principle sufficient to obtain all of the information needed to determine b oth the sensor's position and orientation. A continuous sinusoidal excitati on mode allows an efficient phase-locking and accurate detection of the sen sor output It also improves the electromagnetic compatibility of the method .