Skew estimation and feed-forward control in flangeless tape drives

An enhanced skew follow control system is presented to more accurately and reliably control the tape-to-head skew in tape systems with flangeless rollers. It features a novel feed-forward skew control system, based on a new skew estimation technique that allows obtaining skew from the information provided by one servo channel only. A disturbance observer provides an estimate of the lateral tape motion, which is used to estimate the absolute tape skew. The feed-forward controller utilizes that skew estimate to enhance the performance of a traditional feedback skew-following system and to enable skew follow operation if only one servo channel is active. The performance of the enhanced skew following method is illustrated by experimental results, both in combined operation with the classical feedback system and the feed-forward system and in stand-alone feed-forward mode. © 2013 IFAC.