Lateral Tape Motion Control With Robust Performance Evaluation Based on RBode Plot

Magnetic tapes are still widely used in data storage facilities. A novel approach is presented for reducing the lateral tape motion (LTM) at the reel and thus for preventing the impacts between tape and reel flanges, which can easily damage the fragile tape edges. To measure the LTM, photonic sensors are employed, which have to be calibrated to compensate for nonlinearities and for the shift of the tape path between sensor probes while the reel winds and unwinds. Moreover, since a sensor cannot be placed as close to the reel as desired, the lateral tape position at the reel is estimated by extrapolating from two sensors. Actuation is provided by a tilted rotary guide. In this paper, first, the identified dynamics at the two sensors are combined to estimate the dynamics at the tape nip, and a complex proportional-integral-lead controller is implemented to compensate for the LTM at the extrapolated location. Then, the robust performance characteristics of the implemented controller is evaluated using the robust Bode plot, which accounts for the uncertainties embedded in the used system identification method based on frequency response data. Finally, the experimental results show a significant reduction above 60% in LTM at the reel.