Motion Of Tape Research Articles

Track-Following High Frequency Lateral Motion of Flexible Magnetic Media With Sub-100 nm Positioning Error

Lateral motion of the magnetic tape in data storage applications misaligns the flexible medium relative to the recording head and reduces the potential for decreasing data track width and spacing, and thereby the achievable data storage density. In order to reduce the effect of misalignment between the tape and the recording head, the head is mounted on a track-following actuator that can compensate for the position error up to a frequency that is governed partly by its mechanical resonances; this bandwidth is typically 1 kHz or less for conventional voice coil-based actuators. This paper introduces the design and implementation of a track-following actuator that is piezo-electrically actuated in order to potentially achieve a significant increase of bandwidth and positioning precision. A proof-of-concept is prototyped and experimental results are presented. An H∞ controller is designed and implemented to compensate for typical disturbances such as periodic runout of packs and rollers, or non-periodic flange impacts. Preliminary closed loop experimental results with an experimental low lateral motion tape path, and conventional servo format and media demonstrate a reduction in positioning error standard deviation to 74.5 nm, with simulations indicating a potential for further improvement to 20.6 nm with the use of improved media and servo format.

High frequency lateral tape motion and the dynamics of tape edge contact

Lateral motion of magnetic tape is investigated on roller and porous air-bearing type tape drives. The lateral tape motion signal is high-pass filtered and the spectral components are analyzed. Time-frequency analysis is also performed. The effect of dynamic tension changes during high frequency lateral motion events is examined, and the tension difference across the tape head is found to be correlated to the lateral motion of tape near the head. The effect of lateral motion of tape on tape pack winding is investigated and the frequencies observed during edge contact are analyzed.

Characterization of lateral tape motion and disturbances in the servo position error signal of a linear tape drive

Lateral tape displacement in a tape drive is believed to be one of the critical limiting factors in achieving high track density in tape storage media. For improving track density, servo control systems can be designed on the basis of information from a position error signal to improve the track following capabilities in a tape drive. In this paper, we consider the characterization of lateral tape motion and additional disturbances that contribute to the position error signal. From a commercially available tape drive, the position error signal is measured electronically and lateral tape motion of the magnetic tape is measured using an optical edge sensor. This information is used to characterize the filtering effects of the disturbance rejection transfer function that determines the lateral tape motion and disturbances present in the position error signal. The disturbance rejection transfer function is characterized by two different methods. In the first method, we model the disturbance rejection transfer function as a simple high pass filter. Using lateral motion measurements as an input to this system, the position error signal is simulated and compared with the measured position error signal. In the second method, system identification methods are used to estimate a detailed high order filter that models the essential components of the disturbance rejection transfer function. Using these models, the position error signal is simulated and predicted and the effects of additional disturbances such as the servo track variability can be separated from the effects of the lateral tape motion. It is shown that the position error signal exhibits contributions from lateral tape motion and additional disturbances that differ significantly at higher frequencies.

Motional influences on magnetic reproduction: An analysis based on the reciprocity theorem

Motional influences in magnetic reproduction are analyzed with the aid of the reciprocity theorem of magnetic recording theory. Alternative expressions for the induced READ voltage are derived for the case of a carrier (disk or tape) of spatially recorded magnetization in rigid (translatory and/or rotary) motion. The expressions exhibit, through different physical interpretations, the influence of the motion of a magnetic tape or disk on the induced READ voltage.

An experimental model for simulating the motion of magnetic tape in a tape drive

The capstan-control system can induce tape vibrations in a magnetic tape drive. This paper describes an analytical model for predicting the motion of magnetic tape through a tape drive, including the structural dynamics of the tape and its interaction with the control system. The model includes all significant effects related to the tape and the tape path. The roles of the air bearings, the vacuum column, and the magnetic tape were evaluated by a series of experiments to measure the input mechanical impedance of tape in an actual tape path. These experiments and a derived lumped-mass analytical model showed that the vacuum column added two acoustical resonators to the tape path, that the air bearing added considerable damping, and that the Coulomb friction did not significantly affect the dynamics of the tape.

Viscoelastic Behavior of Computer Tape Subjected to Periodic Motion

The purpose of this study was to develop a theoretical means for predicting the longitudinal motion of computer tape in a high-performance tape drive. In particular, this paper treats the motion that is governed by traveling velocity-stress wave reflections, attenuations, and interactions in the length of tape between the tangency point at the capstan and the tangency point at the stubby column in the drive. The motion of the tape was determined by solving the classical, damped, one-dimensional wave equation subject to the appropriate boundary conditions. J. C. Snowdon's low-damping constitutive model was used to describe the viscoelastic behavior of the tape. The solutions for simple boundary conditions were experimentally verified by mechanical impedance techniques. More complex boundary conditions, such as those for vacuum columns, were experimentally studied to determine the true mathematical boundary conditions. This paper also discusses simple unreflected harmonic waves, simple reflected harmonic waves, and general periodic reflected waves as examples. The significance of the wave interactions in the design of tape drives is considered.