A data-based approach is presented for modeling and controller design of a dual-stage servo actuator in a hard disk drive. The servo actuator in this hard disk drive consists of a conventional voice coil motor and a piezo-electrically actuated suspension. A weighted Hankel matrix based realization algorithm that uses frequency domain data is applied to estimate a discrete-time model of the voice coil motor and the piezoelectric actuator. Based on the discrete-time models, different dual-stage

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... ack-following controllers were designed using classic and H ∞ loop shaping techniques. The controllers were implemented in real-time in the investigated hard disk drive. A stable feed-back control and good agreement between measurements and simulations show the promising result of data based modeling and control.