Track-following system optimization for future magnetic tape data storage

Abstract

Recently, the increase of track density has been shown to be one of the most effective methods to increase the areal bit density and thus the cartridge capacity of future magnetic tape data storage systems. Increasing the track density poses stringent positioning requirements to the tape track-following control system. In this work, we investigate four novel timing-based servo patterns, and the impact of their geometrical properties, i.e. azimuthal angle and subframe length, on the position estimation resolution, the system delay and track-following performance. First, the resolution of the patterns versus reader width is assessed by analyzing the noise floor in the power spectrum of the lateral position estimation. This methodology is used to determine the optimal reader width for each pattern. Second, the system delay for each of the new patterns is identified by measuring the frequency response of the track-following actuator. An analytical model of the delay is derived and verified with experimental data. Finally, the impact of resolution and delay on the track-following performance is investigated. The best track-following performance, characterized by a standard deviation of the position-error signal of 4.2nm, was achieved using a pattern with a 36°azimuthal angle. The performance could be further improved down to 4.0nm by time averaging the position estimates.