Track-following high frequency lateral motion of flexible media

Lateral motion of the magnetic tape in data storage applications misaligns the flexible medium relative to the recording head and reduces the potential for decreasing data track width and spacing, and thereby the achievable data storage density. In order to reduce the effect of misalignment between the tape and the recording head, the bead is mounted on a track-follow actuator that can compensate for the position error up to a frequency that is governed partly by its mechanical resonances; this bandwidth is typically 1 kHz or less for conventional voice-coil based actuators. This paper introduces the design and implementation of a track-following actuator that is piezo-electrically actuated in order to achieve a significant increase of bandwidth up to several kilo-Hertz. A proof-of-concept is prototyped and experimental results are presented. A controller is designed and implemented to compensate for typical disturbances such as periodic runout of packs and rollers, or non-periodic flange impacts. Preliminary closed-loop experimental results demonstrate a reduction in position error standard deviation to less than 80 nm, with simulations indicating a potential for further improvement down to nearly 20 nm or less.