Hybrid Position Error Signal Generation for Disk File
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
A head-positioning servo system for a multi-disk file derives a hybrid position error signal (PES) from continuous position information on a dedicated servo surface and from sampled intermittent position information on the data surfaces. The hybrid PES is essentially the dedicated PES adjusted, after every sample, to the value of the data PES. However, since both component position error signals represent displacement from the nearest track center and the data PES is linear over less than one track width, offsets of more than half a track between servo and data heads could result in the incorrect data track being followed. To avoid this, Gray-coded track-type information is included in the servo samples and compared with track-type information derivable from the dedicated PES to determine any necessary correction.