A generalized KYP lemma based control design and application for 425 kTPI servo track writing

The recently developed generalized Kalman-Yakubovic-Popov (KYP) Lemma establishes the equivalence between a frequency domain property and a linear matrix inequality (LMI), and allows to solve a certain class of system design problems with multiple specifications on gain/phase properties over several frequency ranges. This paper applies the KYP lemma in a control design for microactuator to suppress the narrow-band disturbances through shaping sensitivity functions in data storage systems such as servo track writers for hard disk drives (HDDs). The KYP Lemma is applied together with the Youla parameterization approach to allow a convex optimization for achieving the desired specifications of sensitivity functions. Both LDV based experiment and implementation in a servo track writer demonstrate the effectiveness of the design method in rejecting specific frequency disturbances. In particular, the design method improves the track density of the servo track writer with 425k track-per-inch (TPI).