For　the　rapid　positioning　air　ball　movement　system,　the　simplified　model　was　built　and　the　influences　to　the　servo　performance　were　analyzed,　including　changes　of　the　system,　external　disturbance　and　uncertain　factors.　A　robust　control　strategy　based　on　combining　the　disturbance　observer(DOB)and　PD　controller　was　proposed.　It　can　ensure　the　robust　performance　of　the　system.　The　theory　analysis　and　simulation　experiment　results　show　that　the　robust　feedback　controller　based　on　DOB　can　overcome　the　influences　of　the　uncertainties,　such　as　external　disturbance,　un-modeled　dynamics　and　the　parameters　perturbation　and　so　on,　and　the　robust　performance　is　improved　greatly.　©　2011　IEEE.