Lateral Friction Behavior of a Thin, Tensioned Tape Wrapped Over a Grooved Roller: Experiments and Theory

Effects of friction forces on the lateral dynamics of a magnetic recording tape, wrapped around a grooved roller are investigated experimentally and theoretically. Tape is modeled as a viscoelastic, tensioned beam subjected to belt-wrap pressure and friction forces. Including the effects of stick and slip and velocity dependence of the friction force render the tape's equation of motion nonlinear. In the experiments, tape was wrapped under tension around a grooved roller in a customized tape path. The tape running speed along the axial direction was set to zero, thus only the lateral effects were studied. The grooved roller was attached to an actuator, which moved the roller across the tape. Tests were performed in slow and fast actuation modes. The slow mode was used to identify an effective static, or breakaway, friction coefficient. In the fast mode, the roller was actuated with a 50 Hz sinusoid. The same effective friction coefficient was deduced from the fast actuation mode tests. This test mode also revealed a periodic stick–slip phenomenon. The stick-to-slip and slip-to-stick transitions occurred when the tape vibration speed matched the roller actuation speed. Both experiments and theory show that upon slip, tape vibrates primarily at its natural frequency, and vibrations are attenuated relatively fast due to frictional and internal damping. This work also shows that an effective friction coefficient can be described that captures the complex interactions in lateral tape motion (LTM) over a grooved roller.

On Coupled Dynamics of Frictional Guides in Tape Transport Systems

Stationary guides introduce friction on to a travelling tape in the longitudinal and lateral directions. The longitudinal friction increases the tape tension and the lateral friction dampens the lateral tape motion (LTM). A comprehensive mathematical model of the coupled longitudinal and lateral tape dynamics is developed. Frictional effects over a cylindrical guide are modeled as concentrated loads in both longitudinal and lateral directions. In the range of tape transport velocities that are of interest to data tape recording, it was shown that frictional damping causes reduction of resonant frequencies and resonance amplitudes. Positioning of the guiding elements could significantly influence the dynamic response of LTM.

Control of Time-Varying Lateral Tape Motion in a Linear-Tape-Open Drive via Adaptive Regulation

This extended abstract summarizes a methodology along with the experimental results to adaptively reduce time-varying lateral tape motion (LTM) in a Linear Tape-Open (LTO) drive. For the adaptive regulation, the LTO actuator dynamics is modeled with a Linear Time Invariant (LTI) model and control of time-varying LTM disturbances is done via an adaptable linear feedback controller. Adaptive regulation is done via the direct estimation of a perturbation on the feedback controller. By simultaneously minimizing the variance of the Position Error Signal (PES) and the control output signal, the direct estimation of the controller perturbation is formulated as a weighted estimation problem that is implemented recursively for real-time implementation. The experimental results show a significant reduction of the variance of the PES over different tape cartridges and a constant PES variance during a complete reel-in/out operation of the tape drive.

Piezo-Elastic Actuation for Micro-Positioning of Lateral Tape Motion

In this paper, development of a prototypical microcontroller controlled ultrasonic actuator system incorporating a plate-like piezoelectric actuator is discussed to provide an alternative means in actively guiding the tape laterally. Structural vibration modes are first experimentally examined through standard modal analyses. Method of modal superposition is used in programming the micro-controller so as to provide excitations to the PZT actuator resulted in traveling waves in the plate-like structure. Promising results are demonstrated in the proposed system that have rich implications in providing active guiding mechanism to minimize and even actively control the tape’s lateral motion.