In this paper, we introduce a systematic method of designing a track-follow
ing servo system for hard disk (HD) drives using discrete-time linear-quadr
atic Gaussian/loop-transfer recovery (LQG/LTR) design technique, and some s
tatistical knowledge on disturbances. Newly designed controller was impleme
nted on a commercial HD drive and its performance was compared to the resid
ed compensator. An improvement of 10% in track misregistration (TMR) budget
was observed.