CONTACTLESS MEASUREMENT OF THE SECONDARY POSITION IN LINEAR RELUCTANCE MOTORS

A new method of measuring the position of the secondary in a linear re luctance motor (LRM) is described, based on sampled measurements of th e primary phase currents and the airgap flux density at the primary su rface. Corrections must be applied for primary slot openings, primary end and currents effects, induced in a conducting barrier between the primary and the secondary. A static positional accuracy of +/-1 degree s, representing +/-0.55% of the pole pitch, has been achieved in an ex perimental machine with load angles of up to 30 degrees. The method is particularly suited to applications where the LRM is used for materia ls handling in a sealed containment system, since the secondary positi on can be determined from measurements made on the primary side of a c onducting barrier. It should be capable of accurate position measureme nt at speeds of up to 1 m/s, which is the nominal upper limit for syst ems of this kind.