Control of lateral tape motion using extrapolated position estimation

Magnetic tapes are still widely used for long term archival storage because of their high capacity, low cost, and high reliability. A major challenge to increasing their storage capacity is lateral tape motion (LTM), which can cause the tape to strike flanges on the tape reel, damaging the fragile tape edge. In this paper we present a method for steering the tape onto the reel to prevent such damage. Since the tape radius is changing, we must estimate the tape position by extrapolating from two photonic sensors. Actuation is provided by a tilted rotary guide. We present a method for calibrating the sensors to compensate for nonlinearities as the tape moves in two dimensions within the gap of the sensor while the reel winds and unwinds. We then show how to combine the identified dynamics at the two sensors to estimate the position at the tape nip and how to implement a complex proportional integral lead controller to compensate for LTM. Experimental results show significant reduction in LTM at the reel.