The study and development of automatic data acquisition system for spin-stand imaging and drive independent recovery of hard disk data

Abstract

In this thesis, an automatic data acquisition system for spin-stand imaging and drive independent data recovery is developed. This system enables a user to perform data acquisition of on-track hard disk data by using a commercial spin-stand. At the heart of this system are the three techniques: the track-centering technique, the dynamic track-following technique and the servo-based track-following technique. By using the track-centering technique, we are able to efficiently make the center of the prewritten data tracks coincide with the rotational center of the spin-stand spindle so that the track eccentricity can be eliminated. Both the dynamic track-following and servo-based track-following techniques utilize a small piezoelectric actuator (PZT) as the micro-positioning device. The former is of an open-loop controlling scheme, and the desired tracking trajectory is extracted from the whole-track spin-stand images. The latter is of a closed-loop feedback control scheme, and the feedback signals are from the existing servo patterns on the disk. The former deals with PZT hysteresis by using a special algorithm based on the Preisach model while the approach taken by the latter is based on iterative compensation. By using the developed techniques, we are able to perform spin-stand microscopy on hard disks with longitudinal and perpendicular modes of recording taken from latest commercial hard disk drives (HDDs) with ultra-high areal densities (as high as 131.5 Gbits/in2). The automatic data acquisition system has been successfully applied to recover actual hard disk data from failed HDDs.