J. -H. Im and J. Hur, "Proposing New Planar-Type Search Coil for Permanent Magnet Synchronous Motor: Design and Application for Position Estimation," in IEEE Access, vol. 9, pp. 129078-129087, 2021, doi: 10.1109/ACCESS.2021.3113384.

ABSTRACT Conventional position sensors for permanent magnet synchronous motor, such as optical encoder, resolver, or hall sensor, can get fault by the stress. The fault of the motor position sensor may cause serious accidents. Thus, to prevent damages by the position sensor failure, adding a redundancy sensor such as wound search coil is recommendable. In this paper, a new planar search coil design that can be used as a position sensor for permanent magnet synchronous motor is proposed. This new design is a planar coil based on a exible-printed circuit board that converts airgap ux to a back-electromotive force signal. Unlike the wound search coil design, the proposed design is advantageous for manufacturing and slot-space preservation. Also, this new design is distant from the motor main winding. As a result, the exposure of the electrical and thermal stresses to the sensing coil can be decreased. This research shows the mathematical model for the design of the new planar-shaped airgap ux search coil design. In addition, the position estimation algorithm based on the new search coil design is shown. Finally, the position estimation using the new search coil design is presented.