Lateral Vibration and Read/Write Head Servo Dynamics in Magnetic Tape Transport

摘要

Magnetic tape is a flexible mechanical structure having dimensions that are orders ofnmagnitude different in its thickness, width, and length directions. In order to position thentape relative to the read/write head, guides constrain the tape’s lateral motion, but evennthe modest forces that develop during guiding can cause wear and damage to the tape’snedges. This paper presents a tensioned axially-moving viscoelastic Euler–Bernoulli beamnmodel used to simulate the tape’s lateral dynamics, the guiding forces, and the positionnerror between the data tracks and the read/write head. Lateral vibration can be excitednby disturbances in the form of pack runout, flange impacts, precurvature of the tape in itsnnatural unstressed state, and spiral stacking as tape winds onto the take-up pack. Thenguide model incorporates nonlinear characteristics including preload and deadbands inndisplacement and restoring force. A tracking servo model represents the ability of thenread/write head’s actuator to track disturbances in the tape’s motion, and the actuator’snmotion couples through friction with the tape’s vibration. Low frequency excitation aris-ning from pack runout can excite high frequency position error because of the nonlinearncharacteristics of the guides and impacts against the pack’s flanges. The contact forcendeveloped between the tape and the packs’ flanges can be minimized without significantlynincreasing the position error by judicious selection of the flanges’ taper angle.