A　mode　switching　control　scheme　is　proposed　to　achieve　fast　and　precise　set-point　tracking　in　motor　servo　systems.　The　control　scheme　incorporates　a　composite　nonlinear　feedback　(CNF)　control　law　into　the　framework　of　proximate　time-optimal　servomechanism　(PTOS).　The　CNF　control　law　consists　of　a　linear　feedback　part　for　achieving　fast　response　and　a　nonlinear　feedback　part　for　suppressing　the　overshoot,　so　as　to　improve　the　transient　performance　in　short　span　positioning,　while　the　PTOS　control　law　is　responsible　for　fast　acceleration　and　deceleration　when　the　tracking　error　is　large.　A　reduced-order　extended　state　observer　is　designed　to　estimate　the　unmeasured　velocity　and　unknown　disturbance　for　feedback　and　compensation.　The　closed-loop　stability　is　analyzed　theoretically.　The　control　scheme　is　then　applied　to　the　position-velocity　control　loop　in　a　permanent　magnet　synchronous　motor　servo　system.　Experimental　studies　have　been　carried　out　using　the　TMS320F2812　digital　signal　controller　board.　The　results　verify　that　the　controlled　system　is　capable　of　tracking　a　wide　range　of　target　positions　fast,　smoothly,　and　accurately,　with　some　degrees　of　performance　robustness　against　disturbance　and　uncertainty.　©　1993-2012　IEEE.