It　is　a　key　to　realizing　stable　suspension　operation　of　bearingless　motor　that　the　rotor　radial　displacement　information　is　acquired　accurately.　Sensor　applications　are　sensitive　to　environments,　limiting　to　scenarios,　and　increasing　costs.　Herein,　a　radial　displacement　sensorless　control　method　in　the　full　speed　range　for　single-winding　bearingless　flux-switching　permanent　magnet　motor　is　proposed.　First,　an　eccentric　modulation　function　is　presented,　and　the　flux　linkage　equation　of　each　winding　with　rotor　eccentricity　is　derived　based　on　the　air-gap　magnetic　field　modulation　theory.　Therein,　the　phase　inductance　and　flux　are　functions　of　the　rotor　displacement.　Second,　the　bias-flux　equations　of　the　symmetric　windings　are　deduced,　and　the　rotor　displacement　observer　of　the　medium-high　speed　is　established　based　on　the　bias-flux　amplitude.　Due　to　flux　information　being　difficult　to　extract　at　low　speed,　the　high-frequency　current　signal　is　injected　into　the　dT-axis　of　the　torque　plane.　The　rotor　displacement　observer　of　the　zero-low　speed　is　established　based　on　the　high-frequency　bias-induced　EMF　amplitude.　Besides,　a　novel　smooth　switching　process　is　designed.　Finally,　the　observers　are　analyzed,　and　the　radial　displacement　sensorless　control　strategy　is　built.　The　experimental　results　verified　the　validity　of　the　proposed　method.　©　1986-2012　IEEE.