Homopolar permanent-magnet-biased action magnetic bearing with an integrated rotational speed sensor

Abstract

Radial poles are placed around a radial actuator target mounted on a body. The poles are separated from a cylindrical surface of the target by radial gaps and adapted to communicate a magnetic flux with it. The radial poles are equipped with electrical control windings and magnetically coupled to form magnetic control circuits. A flux return pole is adjacent to the body, separated from it by an air gap and adapted to communicate a magnetic flux with the radial actuator target. A permanent magnet generates a magnetic bias flux in the magnetic bias circuit formed by the radial actuator target, the radial poles and the magnetic flux return pole. A radial force is exerted on the actuator when the control windings are energized with a current. A Hall effect sensor measures bias magnetic field in the air gap between the magnetic flux return pole and the body. A feature on a body is adapted to produce a circumferentially local discontinuity in the magnetic field measured by the Hall effect sensor as the body rotates.