Axial resolver based on the orientation dependent permeability of a grain-oriented silicon steel using multiple 8 -shaped coils

We have tested orthogonally stacked figure-of-eight flexible coils to detect the rotation angle of a rotor made of the grain oriented silicon steel. In this scheme, an angle between the axis of the uniaxial anisotropy pertaining to the rotor and the prefixed axis of a flexible coil is related to the orientation dependent permeability. A 15 mm by 15 mm size flexible coil is placed closely to the rotor and the other side of the coil is covered with an amorphous tape working as a back yoke. One of the figure-of-eight coils is used as an excitation coil and the other is for a sensing coil of magnetic fluxes passing through the rotor. With an excitation current of frequency 16 kHz and 50 mA, a demodulated output of a sinusoidal waveform under the constant rate of revolution of 3000 rpm was obtained with a rotor of 7.6 cm in diameter. The scheme was further developed to obtain two phase outputs by combining two sets of the flexible coils, where coils in one group is 45 degree angle rotated from those in the other group. Basic characteristics of a developed axial resolver were investigated.