Nanoscale track-following for tape storage

Abstract

Track-density scaling is projected to be the key driver for increasing the areal density and cartridge capacity in future tape storage systems. To achieve very high track densities, positioning control down to the nanometer scale will be essential. In this paper, the positioning accuracy of the tape track-following control system is investigated and advances in several elements of the system are presented. First, we introduce an optimized servo channel that combined with an experimental timing-based servo pattern provides lateral position estimates with nanoscale resolution. Second, a newly developed prototype head actuator and an experimental tape transport system were developed. The lateral tape motion (LTM) disturbance in the experimental tape path and the measurement noise in the position estimate were fully characterized and used to optimize the design of the track-following controller using the H∞ control framework. Finally, the hardware platform used to implement the servo channel and track-following control loop was optimized to minimize loop delay. Combining these technologies with a high-SNR magnetic tape based on perpendicularly-oriented barium ferrite (BaFe) particles, we were able to demonstrate a position error signal (PES) with a standard deviation of less than 10 nm over a wide range of tape velocities.