Identification of MIMO transport systems in tape drives

As tape storage aims at cartridge capacities beyond 100 terabytes, advanced control systems for tape transport are key to achieve a larger volumetric recording density. Reliable and ultra-precise tape transport servomechanisms are required to enable tape-drive operation with thinner tape and to support higher areal data densities by minimizing tape-speed variations, tape deformation, and lateral motion effects during tape operation. In this paper, a new identification method is presented for a multiple-input multiple-output (MIMO) tape-transport system for tape drives as the basis for improved control concepts. The characterization of the tape-transport system is obtained in the frequency domain during closed-loop operation of the tape-transport servomechanism. The output system variables are the primary tape velocity and the tape-tension variation, which are estimated from the information obtained by reading pre-formatted servo information, as well as the tape velocities at the supply and take-up reel provided by Hall sensors. Experimental results are presented to illustrate the proposed identification method.