Active tape steering control system

Lateral tape motion (LTM) in tape drives hinders accurate servo head positioning and can cause damage to the tape. It is one of the major obstacles toward developing high density, high performance tape drives. This thesis is primarily concerned with the development of analytical tools, algorithms, and hardware to reduce LTM with an active tape steering control system.; The first major contribution of the thesis is the hardware for active tape steering. The hardware consists of a tilted tape guide mounted on a rotary voice coil motor for actively altering the tape path. The hardware also includes A/D and D/A converters, an optical sensor, and power electronics for implementing control algorithms and for collecting data.; The second major contribution of this thesis is the development of the Robust Bode plot (abbreviated as the RBode plot), in which a robust performance criterion for single-input/single-output systems is translated into boundary functions on the open-loop Bode plot. The boundary functions partition the conventional Bode plots into regions that do and do not meet specific robust performance criteria. These boundary functions incorporate both phase and magnitude information, and are useful for analysis and for classical loop shaping for systems subject to uncertainties.; Development of the Circle Criterion Bode plot (abbreviated as the CBode plot) is the third major contribution of this thesis. The CBode plot translates the Circle Criterion for memoryless system nonlinearities into boundary functions on the open-loop Bode plot so the Bode plot is thus partitioned into regions that do and do not meet the Circle Criterion. By using the CBode plot, one can design and analyze a controller for a nonlinear system with classical loop shaping.; RBode and CBode plots are applied in the controller design process for the active tape steering system. A thorough system identification-based modeling extraction process followed by controller simulation and implementation constitutes the fourth major contribution of this thesis.; The results from tape steering experiments on the tape transport show the effectiveness of both the hardware design and the RBode and CBode plots as analytical controller design tools.