The PES Pareto Method: Uncovering the Strata of Position Error Signals in Disk Drives

This paper and the two that accompany it will describe a method of breaking down the Position Error Signal (PES) of a magnetic disk drive to its contributing components. Once these components are identified, they can be ranked in terms of their overall effect on PES and thus the most critical ones can be worked on first. This method is based on three things: an understanding of how Bode’s Integral Theorem[1] ties into noise measurements, a measurement methodology that allows for the isolation of individual noise sources, and a system model that allows these sources to be recombined to form the drive’s Position Error Signal. We have found this method to be dramatically useful in identifying the key contributors to PES noise.