A linear magnetic gear

Abstract

Linear magnetic gears, when coupled with a linear permanent magnet machine, are a high-efficiency, high-reliability and force-dense alternative to traditional linear actuation solutions. It is shown that the force density of a linear magnetic gear is affected by the required output stroke and gear ratio. A technique based on lumped parameter magnetic circuits is presented. It is employed for prediction of the flux density waveforms and the thrust force of the magnetic gear, which are in good agreement with those predicted by magnetostatic finite element analysis. A prototype 3.25:1 linear magnetic gear is described. It is shown that the force capability of the linear magnetic gear can be very sensitive to manufacturing tolerances, in particular those related to the spacing between the pole-piece rings.