D. Abramovitch et al., AN OVERVIEW OF THE PES PARETO METHOD FOR DECOMPOSING BASE-LINE NOISE SOURCES IN HARD-DISK POSITION ERROR SIGNALS, IEEE transactions on magnetics, 34(1), 1998, pp. 17-23
This paper gives an overview of the PES Pareto Method, a useful tool f
or identifying and eliminating key contributors to uncertainty in the
Position Error Signal (PES) of a magnetic disk drive servo system [1,
2, 3]. Once identified and ranked according to their overall effect on
PES, the top-ranking sources can be worked on first, either by findin
g ways to reduce their magnitude or by altering system components to r
educe sensitivity to the contributors. The PES Pareto Method is based
on three ideas: (1) an understanding of how Bode's Integral Theorem [4
] applies to servo system noise measurements, a measurement methodolog
y that allows for the Isolation of individual noise sources, and tem m
odel that allows these sources to be recombined to simulate the drive'
s Position Error Signal. The method requires the measurement of freque
ncy response functions and output power spectra for each servo system
element. Each input noise spectrum can then be inferred and applied to
the closed loop model to determine its effect on PES uncertainty. The
PES Pareto Method is illustrated by decomposing PES signals that were
obtained from a hard disk drive manufactured by Hewlett-Packard Compa
ny. In this disk drive, it is discovered that the two most significant
contributors to PES baseline noise are the turbulent wind flow genera
ted by the spinning disks (''Windage'') and the noise involved in the
actual read-back of the Position Error Signal (''Position Sensing Nois
e'').