| In the field of computer data storage, tape libraries are used for long-term archive, backup, and restoration of financial information, medical records, geophysical data, satellite imagery, and electronic intelligence. Such data is stored for decades, often under regulatory requirements, and its value increases with time. During the past fifty years, the volumetric storage density for this technology has grown by six orders of magnitude, partly due to advances in the mechanical design of the path, guides, cartridge, and servo mechatronics. As data is written to the tape, or read from it, the head assembly is actively positioned in the cross-track (or lateral) direction over a data track that itself is only microns wide and that moves down-track (or axially) at several meters per second. Lateral vibration can be excited by disturbances in the form of pack runout, flange impacts, precurvature of the tape in its natural unstressed state, contact with nonlinear guides, fictional vibration transmission from the positioning of the read/write head over a data track, and spiral stacking as tape winds onto the take-up pack. The undesirable lateral vibration of the tape can inhibit reading or writing by the read/write head, and must be mitigated in order to further increase its volumetric storage density.;This thesis is motivated by the need to mitigate lateral tape vibration in order to increase the volumetric storage density of magnetic tape. A system level model of magnetic tape transport and three submodels of components within magnetic tape systems are developed in order to simulate the lateral tape motion, guiding forces, and position error during operation of a magnetic tape drive. The specific issues that are addressed, and the major contributions, include: (1) A system level model of lateral tape motion, servo tracking, and position error is developed. The model includes the non-straight natural shape of the tape, viscoelastic damping of the tape, the non-straight position of the pre-written servo track, frictional coupling between the read/write head and the tape, nonlinear guides, pack runout, and flange impacts. The model is applied to investigate how several design parameters, including the nonlinear guides' preload and clearance and the taper of the take-up pack's flanges, effects the impacts of the take-up pack's flanges on the position error between the head and the servo track, and the edge forces acting on the tape. (2) A model for vibration transmission from a laterally oscillating surface to a traveling tensioned beam is developed as an analog of the interaction between a moving read/write head and magnetic tape. For a surface having a constant radius of curvature, vibration transmission from the surface to the beam can be minimized for a specific vibration mode by choosing an engagement length that is approximately an integer multiple of the mode's wavelength. In certain applications where it may not be feasible to implement surfaces of such width for the lower vibration modes, this approach may be useful to limit excitation of higher-frequency modes which can be more problematic in the present application. (3) A model for the vibration of a traveling string in contact with a piecewise-linear constraint is developed as an analog of the interaction between magnetic tape and a guide in data storage systems. There are critical bifurcation thresholds, below which the system exhibits period one, symmetric behavior, and above which the system contains asymmetric, higher periodic motion with windows of chaotic behavior. These bifurcation thresholds are particularly pronounced for the transport speed, flange clearance, and guide position. (4) A model of guide tilt with friction and arbitrary force-deflection constitutive relationship is developed in order to calculate the change in displacement, slope, bending moment, and shear force for a segment of tape wrapped around a tilted guide. The model is validated by measurements and is compared to a previously existing model of guide tilt. |
