Head positioning servo design for the IBM 3344/3350 disk files

The 3344/3350 disk files have significantly increased both the recording areal density and total storage capacity per spindle in comparison to previous disk file products, such as the 3340. Parameters directly related to the head positioning systems are compared. Three areas of the head positioning servo system that required design changes for increased performance are described: (1) the encoding used on the servo disk to obtain position information, (2) the compensation technique employed in the track following controller to reduce steady state positioning error and (3) implementation of the phase plane trajectory for improved accuracy and settling as well as decreased access time.