Servo bandwidth and positioning accuracy design for high track density disk drives

Possibility of achieving positioning accuracy to meet the areal density of 40 Gb/in(2) has been studied. Stationary and nonstationary position errors are shown, and the servo design approaches have been proposed, A precise mo del of head-positioning system has been developed, and the required open lo op servo bandwidth is estimated using the model. The experimental results u sing 2.5-inch HDD show that 750 Hz to I kHz servo bandwidth (open loop cros sover frequency) is effective to achieve 40 nm positioning accuracy during track-following to meet 60 kTPI for 40 Gb/in(2).