Track-follow control for tape storage

Lateral tape motion (LTM) in tape storage systems is the main contributor to the position error signal (PES) and thereby the limiting factor to track density on a magnetic tape. The characteristics of LTM disturbances and their effect on track-follow performance are identified. The power spectral density of LTM contains many periodic components at the so-called “once around” roller-frequencies and their harmonics. Another contributor to LTM is originated by the stack shift effects. Stack shifts are low frequency disturbances that degrade the track-follow performance, especially in tape paths with flangeless rollers. Control design concepts are evaluated that improve the track-follow performance of tape storage systems.