Initial resolution of head position and skew uncertainty in control systems for flangeless tape drives

Tape drive operation with flangeless rollers in the tape path has been introduced in tape drives to extend the lifetime of drive and medium and to achieve nanometer positioning accuracy in track following by mitigating high-frequency lateral tape motion. However, the use of flangeless rollers requires dynamic-skew compensation to keep the head perpendicular to the direction of tape motion in the presence of large lateral tape excursions. Furthermore, a large uncertainty on the initial values of the tape-to-head skew and of the head lateral position must be resolved prior to track following for write/read operation. In this paper, we consider a control system for a two-degree-of-freedom head actuator using a dual synchronous servo channel to provide lateral position and tape-to-head skew feedback. The initial uncertainty on the tape-to-head skew and on the data band being spanned by the head at the beginning of drive operation is resolved by testing hypotheses related to different tape-to-head skew angles with an ad hoc metric obtained by the dual servo channel. Simulation results are presented to illustrate the performance of the proposed method.