Frequency domain subspace identification of a tape servo system

As capacity demands for magnetic tape storage systems grow, servo actuator design for tracking data on high density tape media presents new modeling and control design challenges. In this paper a frequency weighted subspace identification algorithm is presented for control relevant model estimation of a tape servo actuator. Common to other subspace identification methods, the proposed algorithm is based on linear algebra techniques providing means for model order selection and model computation. The proposed subspace identification also allows for frequency dependent weightings to emphasize frequency data around the cross-over frequency to find models relevant for control design. The algorithm is applied to data obtained from a tape storage device, demonstrating model order selection and the estimation of servo actuator dynamics with control relevant model fit criteria.