An　internal　model　control-based　observer　was　derived　to　estimate　uncertainties　for　current　loops　caused　by　parameter　variations　and　disturbances　in　permanent　magnet　synchronous　motor　(PMSM).　Specifically,　a　state-space　model　for　current　loops　was　set　up　as　an　internal　model　under　the　condition　that　the　coupling　term　and　the　back　electromotive　force　were　compensated　completely,　and　an　augmented　model　was　constructed　by　introducing　the　error　variable　between　a　real　current　and　the　internal　model　current.　Then,　a　control　law　for　the　augmented　model　was　derived　by　the　state　feedback　control　theory.　Finally,　observer　parameters　were　optimized　by　the　pole　placement.　Through　simulations　and　experiments,　the　superior　control　performance　on　suppressing　current　ripple　for　better　speed　regulation　in　PMSM　is　verified.　©　2016　Chin.　Soc.　for　Elec.　Eng.