The dynamic characteristics of a slider flying over various servo patterns on a disk surface were investigated. The investigation shows that the air-flow field is disturbed and causes flying modulation during the transition from grooved longitudinal discrete tracks to a transversal and near-random pattern in the servo field. The effects of the parameters that define the servo pattern — including land area ratio of burst patterns, groove depth, servo-pattern frequency, and the lengths of synchronization (sync), servo address mark (SAM), postamble (PAD) blocks, and burst pattern type — on the flying height responses were evaluated. The evaluation results indicate that the flying-height modulation depends on servo-pattern frequency, burst land-area ratio, groove depth, and the lengths of the sync, SAM, and PAD block and burst pattern type. Modulation of a slider flying over a servo pattern therefore can be reduced by optimizing the servo-pattern design from the viewpoint of these parameters.

The static and dynamic properties of tilting-pad journal bearings with controllable radial oil injection are investigated. The tilting pads are modelled as flexible structures and their dynamics are described using a three dimensional finite element framework and linear elasticity. The oil film pressure and flow are considered to follow the modified Reynolds equation, which includes the contribution from controllable radial oil injection. The Reynolds equation is solved using a two dimensional finite element mesh. The rotor is considered to be rigid. The servo-valve flow is governed by a second order ordinary differential equation, where the right hand side is controlled by an electronic input signal. The constitutive flow pressure relationship of the injection nozzles is that of a fully developed laminar velocity profile and the servo-valve is introduced into the system of equations by a volume conservation consideration. The Reynolds equation is linearized with respect to displacements and velocities of the nodal degrees of freedom. When all nodal points satisfy the static equilibrium condition, the system of equations is dynamically perturbed and subsequently condensed to a 2 by 2 system, keeping only the lateral motion of the rotor. As expected, rotor stability is heavily influenced by the control parameters.

The air bearing steady-state flying characteristics on patterned media has been studied with a proprietary air bearing simulation code. Variation of minimum fly height with relative pattern-to-slider skew has been characterized at slider positions (ID, MD, OD). The results show that at the steady state minimum fly heights drop with introducing the pattern. Furthermore, the pattern-to-slider skew angle has a noticeable effect on the fly height drop, while the maximum fly height drop occurs on radial servo patterns.

Advances in various areas of precision mechanics, such as semi-conductor manufacturing equipment, MEMS/NEMS, biomechanics, nano-imprint and nano-technology, have required ultraprecise positioning techniques with nanometer scale accuracy to be developed. To meet such specific needs, many different kinds of actuator capable of ultraprecise motions have recently been produced. However, each actuator has some inherent problems; for example, actuators containing piezoelectric elements have been reported to cause hysteresis errors, thermal drifts, deterioration, and destruction. Based on this background, highly reliable and accurate actuators are strongly required.

Higher TPI HDD requires lower disturbance and higher error rejection capability. One of the limitations to achieve high error rejection capability is the dynamics of the actuator. Dual stage actuator (DSA) has been considered to replace single stage actuator (SSA) someday because of system dynamics difference and more freedom in servo design that may avoid the constraint of single stage actuator dynamics on servo. SSA and DSA were compared based on their dynamics, servo designs, and TMR benefits. The extendibility and limitations of both systems were studied. The criteria on when DSA would be implemented are also discussed.

To achieve higher data track density of a hard-disk drive (HDD), a microactuator that is placed between suspension beam and a slider and moves slider relative to suspension was investigated. This paper presents new microactuator design, “bipolar microactuator” and its performance in a hard-disk drive.