An Improved Magnetic Tracking Method Using Rotating Uniaxial Coil With Sparse Points and Closed Form Analytic Solution

A set of triaxial magnetic transmitting coils fed with low frequency sinusoidal signals can be tracked with a rotating uniaxial sensing coil. This is because the specific output signal of the sensing coil will reach a maximum value when the direction of its induced magnetic field points to the transmitting coils. Usually, a rotating method is used to find the maximum output direction based on the output signals from the sensing coil. This method needs a horizontal rotation phase and a vertical rotation phase to search for the maximum output and its accuracy depends on the rotation step size. In order to simplify the rotation process while maintaining the accuracy without reducing the rotation step size, an improved magnetic tracking method is proposed in this paper. It is found that when the sensing coil rotates in the horizontal plane, the specific output signals compose a sinusoidal curve. By extracting the amplitude, phase, and dc component of this sinusoidal signal, the distance and direction information between the sensing coil and transmitting coils can be estimated and no vertical rotating phase is needed. Another advantage of this method is that the tracking accuracy does not depend on the rotation step size once the sampling rate fulfills the Nyquist–Shannon sampling theorem. Therefore, we can use sparse points to reconstruct the sinusoidal signal. Experimental results will show the effectiveness of this tracking method.