Sensorless　technology　cannot　only　reduce　the　cost　of　motor　drive　system,　but　also　improve　system　reliability.　In　the　sensorless　direct　torque　control　(DTC)　drive　system　of　permanent　magnet　brushless　dc　motor　(BLDCM),　the　estimations　of　instantaneous　electromagnetic　torque　and　stator　flux　linkage　are　two　key　issues.　Additionally,　some　BLDCMs　with　salient-pole　phenomenon　make　the　estimations　of　torque　and　flux　linkage　even　harder.　A　sensorless　salient-pole　BLDCM-DTC　drive　system　is　proposed　in　this　paper.　A　stator　current　estimator　with　back　electromotive-force　(EMF)　self-adaptation　is　first　constructed　according　to　stator　current　state　equations　and　the　back　EMF　is　obtained　by　adaptive　law.　Then,　a　phase-locked　loop　is　used　to　output　smooth　estimated　value　of　rotor　position　angle　based　on　the　identified　back　EMF.　At　last,　according　to　the　estimated　rotor　position　angle,　the　torque　and　stator　flux　linkage　are　calculated　to　realize　saliency　BLDCM-DTC　running　smoothly.　Experimental　results　show　that　the　estimated　torque　and　stator　flux　linkage　are　very　close　to　their　actual　values.　The　novel　sensorless　DTC　drive　system　has　nice　dynamic　and　static　performances,　and　the　lowest　steady-state　speed　can　be　decreased　to　33　r/min.　©　1986-2012　IEEE.