Frequency Domain Characterization of Take-Up Reel Air-Entrainment in Low-Tension and High-Speed Tape Transport

Abstract

Air entrainment in tape spooling is important because it affects the tape stacking quality and the dynamics for which the transport controller must be designed. Accurate estimates of the air film thickness between the layers of tape are difficult to obtain by direct measurement. In this paper, a new frequency domain method is presented where the length of the entrained air film is estimated by determining the spring constant of the unsupported tape span. Using multi-input single-output (MISO) frequency based system identification, the resonant frequency of the system associated with the longitudinal mode of the tape is derived. These data are compared to predictions from the well known nip height equation. The utility of these equations is discussed.

Control Methods in Data-Storage Systems

“…The phenomenon of air entrainment, whereby friction draws a thin layer of air into the take-up reel, causing several layers of tape to be wound loosely, has been studied extensively both in steady state [44], [45] and during transients [46]. As the tape velocity increases, air entrainment increases the effective length of the tape path, thus lowering the spring constant of the tape and hence the resonance frequency of the transport system.…”

Robust lyapunov-based feedback control of nonlinear web-winding systems

“…Air entrainment in the takeup reel changes the length of web media that is free to vibrate, which is called the "unsupported tape length" L(t) in tape systems [8]. This leads to nonlinearities because according to structural mechanics the spring and damping parameters vary inversely with L(t):…”

“…These constants might be determined by experiments similar to [3] or modeling approaches like [3], [8]. In this paper D(·) ∈ D is considered an unknown and time-varying parameter.…”

“…This allows a greater length of the media to vibrate, effectively making the spring and damping parameters time-varying. Little has been published about the dynamics of air entrainment, though some work has been done investigating the steady-state phenomenon [3], [8].…”