Position detection for shaft-type linear motor by measurement of shaft surface magnetic flux

A low-cost position sensing method for shaft-type linear motors is proposed. The proposed position sensor consists of a Hall element array and an analog circuit. The mover is equipped with this array, which measures the magnetic flux of the shaft surface. Each output of the Hall element is multiplied by given coefficients and summed by the analog circuit. This circuit generates a two-phase sinusoidal signal with respect to the mover position, even though the surface flux is spatially distorted. Position information with good linearity and precision is achieved using this signal. The proposed sensor configuration and circuit simplification are described and the experimental results are discussed.