Johan B. C. Engelen

Flat-Profile Tape–Head Friction and Magnetic Spacing

The friction and magnetic spacing between magnetic tape and a recording head are measured as a function of the wrap angle at several tape speeds and tape tensions for two tape samples with different roughnesses. An increase in friction and a decrease in magnetic spacing are measured for: 1) increasing wrap angle; 2) decreasing tape speed; and 3) increasing tape tension. The relation between the magnetic spacing and friction is fixed when varying the tape tension or wrap angle. For the rougher tape sample, reducing the tape speed (and adjusting the tape tension and wrap angle accordingly) reduces the magnetic spacing without increasing the friction. Although the smoother tape experiences more friction for a fixed wrap angle and tape tension, a smaller magnetic spacing at a specified friction is measured for it than for the rougher tape.

Where Tape and Hard-Disk Technology Meet: The HDD Head–Tape Interface

In this paper, we study the mechanical interface between a hard-disk drive (HDD) head and magnetic recording tape to enable the use of HDD heads to investigate future tape operating points. Tape surface height measurements were obtained using an interferometer microscope for varying wrap angle configurations, tape velocities, and tape tensions. Simultaneously, the readback signal from the read element of the HDD head was captured to study the quality of the contact between the tape and the head. The signal-to-noise ratio (SNR) and bit-error rate (BER) performance of pseudorandom bit sequence (PRBS) data readback experiments are presented. An analytical model is described for estimating the magnetic spacing from the PRBS readback spectrum. In contrast to current commercial tape heads, the HDD head surface has a pronounced topography containing cavities. When tape passes in close proximity, subambient pressures are formed inside these cavities and the resulting pressure differences force the tape toward the head and deform the tape into remarkable shapes. For the topography of the HDD head used, the shape of tape is predominantly determined by the leading and trailing wrap angles. Readback was obtained only in the backward direction (i.e., opposite to the direction of operation in an HDD), with positive leading but negative trailing wrap angles. Better readback is obtained for shallow wrap angles, lower tape velocity, and higher tape tension. Good readback is obtained for leading and trailing wrap angles ~0.3° and -0.2°, respectively. Fits of the analytical model to the spectrum of the readback signal of PRBS data lead to a magnetic spacing estimate of ~30 nm. At 600 kb/in linear density, we measured 11 dB SNR and 7 × 10-3 BER for PRBS data on perpendicularly oriented particulate barium-ferrite tape.

Planar Thin-Film Servo Write Head for Magnetic Tape Recording

We present a planar thin-film servo write head for writing timing-based servo patterns. The planar head operates at low current ( ~ 100 mA) with nanosecond switching times. The planar head can handle dc current, enabling trailing-edge writing. Magnetic force microscopy measurements of the transitions written by the planar head and a conventional commercial servo write head on longitudinal metal particle and nonoriented barium ferrite media were made to assess the quality of the written transitions. The transition response width PW50 is found to be independent of the tape velocity during write for the planar head. For the conventional head, PW50 is larger and increases with the tape write velocity. The reduced PW50 results in larger readback signal amplitude and hence an improved track-follow performance. The faster switching capability of the planar head enables formatting at higher tape velocity.

Multimodal Aerial Locomotion : An Approach to Active Tool Handling 10 Author

The research focus in aerial robotics is shifting from contactless inspection toward interaction and manipulation, with the number of potential applications rapidly increasing [1]. Eventually, aerial manipulators, i.e., unmanned aerial vehicles (UAVs) equipped with manipulators, will likely take on hazardous maintenance tasks now performed by humans. For this to happen, aerial manipulators must be able to perform all the different operations required in these maintenance routines.

A Model for Head/Tape Friction for Smooth Media

We present a model for calculating the friction at the head/tape interface as a function of wrap angle, tape speed, tension and head dimensions. The model is based on the Euler–Bernoulli beam equation and the Reynolds equation. Several refinements relative to previous implementations are introduced: specifically a multi-coefficient slip-flow correction is implemented to deal with the reduction of spacing, the skiving-edge profile is modeled using interferometer microscope measurements to account for edge rounding, and the tension asymmetry due to friction is accounted for. Results from the model are compared with experimental measurements of friction versus wrap angle and tape velocity. The model and the experiment show excellent agreement under the range of conditions studied.

A Novel Approach To Surface Operations With Multirotor UAVs

This video shows the indoor experimental evaluation of our latest aerial manipulation system which is capable of brushing surfaces. This is enabled by means of two innovations. The first innovation is a special tool that ‘drives’ over the surface using the friction generated by the interaction forces, while simultaneously applying a tool (here a brush) with a constant force on the surface using a spring. The second innovation is in the control theory, which stabilizes the UAV while allowing this movement. The experiment in the video shows how these innovations are applied to clean a patch on a surface, and is the validation step of the system before working on moving it outdoors towards the realistic scenario.

Tape-Head With Sub-Ambient Air Pressure Cavities

A new tape-head design with surface cavities is presented as an alternative to the conventional skiving-edge flat-profile head design. The new head design is referred to as the vacuum head, inspired by the sub-ambient air pressure that develops in the surface cavities during operation. Two prototype head modules, a writer and a reader, were fabricated by modifying commercial tape-head modules and are compared with unmodified reference modules. A finite-element model is presented to simulate the head-tape interface and aid in the surface topography design of the vacuum head prototypes. The modeling results correspond qualitatively with experimental data from interferometer measurements of the shape of tape as it passes over the vacuum heads. The vacuum heads are operated successfully in data read/write experiments, with a slightly reduced signal-to-noise ratio performance compared with the reference heads. An indirect measure of head friction is obtained from tape velocity spectra that show a much reduced friction-induced compressional wave tape resonance for the vacuum modules compared with that for the reference modules. The results presented in this paper show that the new vacuum head design is a promising candidate for future heads with low friction, enabling the use of very smooth media for reduced magnetic spacing and increased areal densities.

Side-Reading Effects in High-Track-Density Tape Recording

Aggressive track-density scaling in linear magnetic tape recording has been identified as a key means of sustaining capacity scaling. As the reader width decreases, the relative signal contribution of the written track region outside the lateral extent of the reader increases. We model, analyze and quantify side-reading effects of shielded magneto-resistive read heads reading narrow tracks on perpendicular-oriented tape media. We compare results from extended analytical models with experimental data. An understanding of these effects will be important in designing track misregistration budgets and SNR margins for future operating points of parallel-channel tape recording systems.