In　this　study,　a　novel　sensorless　control　of　the　surface-mounted　permanent-magnet　synchronous　motor　(PMSM)　is　proposed.　Firstly,　by　taking　the　derivative　of　the　back　electromotive　force　(EMF),　the　high-order　voltage　equations　of　PMSM,　in　which　the　dominant　time-changing　parts　of　back-EMF　are　separated　and　modelled,　are　deduced.　Then　a　generalised　extended　state　observer,　which　possesses　the　preferable　tracking　ability　for　time-varying　states,　is　designed　to　estimate　the　back-EMF.　Also,　since　the　difference　between　the　measured　stator　resistance　and　its　real　value,　which　changes　with　temperature,　will　lead　to　position　errors,　a　resistance　estimation　scheme　is　proposed.　Compared　with　the　conventional　sensorless　method　of　PMSM,　the　proposed　method　can　provide　a　more　accurate　and　smooth　position　and　speed　estimation　under　resistance　uncertainty　without　extra　filter　and　compensator.　Furthermore,　since　the　effects　of　speed　and　current　change　rate　are　taken　into　consideration,　the　application　of　the　proposed　scheme　is　broadened.　The　effectiveness　of　the　proposed　method　is　verified　by　the　experiments　in　different　cases.　©　2020　Institution　of　Engineering　and　Technology.　All　rights　reserved.