Dynamic Flying Height Adjustment in Hard Disk Drives Through Feedforward Control

Boettcher, Uwe; Li, Hui; Callafon, Raymond A. de; Talke, Frank E.

doi:10.1109/tmag.2011.2136328

Cited by 27 publications

(6 citation statements)

References 20 publications

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“…The height should be close enough for dense data storage, but sufficiently high to avoid striking the disk surface. Performance drivers linked to capacity and read/write speed have driven the flying height from about 20 microns in the first commercial devices to a few nanometers today [219,220].…”

Section: Flying Height Of Read-write Heads Of Rigid Disk Drivesmentioning

confidence: 99%

A review of selected topics in interferometric optical metrology

Groot

2019

Rep. Prog. Phys.

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This review gathers together 15 special topics in modern interferometric metrology representing a sampling of historical, current and future developments. The selected topics cover a wide range of applications, including distance and displacement measurement, the testing of optical components, interference microscopy for surface structure analysis, form and dimensional measurements of industrial parts, and recent applications in semiconductor manufacturing and consumer electronics. Techniques range from laser Fizeau systems to dynamic ellipsometry using polarized heterodyne interferometry.

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Section: Flying Height Of Read-write Heads Of Rigid Disk Drivesmentioning

confidence: 99%

A review of selected topics in interferometric optical metrology

Groot

2019

Rep. Prog. Phys.

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“…On the other hand, in current HDDs, we have a thermal flying-height control (TFC) system. For this TFC system, the magnetic head has a heater located in a vertical direction of read/write elements in order to control flying height of the read/write elements with thermal expansion (Shiramatsu et al, 2008;Ookubo et al, 2010;Boettcher et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Two-degree-of-freedom control scheme for flying-height and tracking-position controls with thermal actuators in HDDs

Atsumi

2018

JAMDSM

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To improve positioning accuracy of a magnetic head in hard disk drives (HDDs), a triple-stage-actuator system was proposed with a thermal positioning actuator for a magnetic head positioning system. This positioning system has three types of actuators: a voice coil motor (VCM), piezoelectric (PZT) actuators, and the thermal positioning actuator. In this system, a magnetic head has a heater located in a horizontal direction of read/write elements as the thermal positioning actuator. By using this structure, the control system can move the position of read/write elements of the magnetic head in a horizontal direction with thermal expansion induced by the heater with an electric current. The thermal actuator systems have simple characteristics without mechanical resonant modes even in a high frequency range. This means that the thermal actuator is good for positioning control in high frequency range. As a result, the triple-stage-actuator system enable us to improve the positioning accuracy during a trackfollowing control from conventional dual-stage-actuator systems. However, the thermal positioning actuator causes flying height fluctuations of the magnetic head that could lead to fall of magnetic recording performances. In HDDs, the magnetic head has another heater located in a vertical direction of read/write elements in order to control flying height of the read/write elements. This control system is called thermal flying height control system. In the previous study, we can compensate for the flying-height fluctuations by using a feedforward control scheme of the TFC system. However, the feedforward control has little robustness against the plant perturbations. To address this issue, this paper employs a two-degree-of-freedom (TDOF) control scheme for the coordinated control with the TPC and the TFC systems. By using proposed TDOF method, we can compensate for the flying-height fluctuations against the plant perturbations. Simulation results showed that the proposed method is able to improve robust performance against the plant perturbations.

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“…The immense spread of internet and cloud computing requires a constant development of data storage devices. Nowadays, discoveries such as giant magnetoresistance (GMR), 1,2 tunneling magnetoresistance (TMR) 3,4 and innovations like dynamic flying height (DFH) 5 or perpendicular magnetic recording (PMR) [6][7][8] made possible the continuous increase of stored information on a unit surface area. However, exceeding 1 Tbit per inch 2 storage density is not possible with the latter techniques 9 and hence further developments are essential.…”

Section: Introductionmentioning

confidence: 99%

Evolution of magnetism on a curved nano-surface

et al. 2015

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To design custom magnetic nanostructures, it is indispensable to acquire precise knowledge about the systems in the nanoscale range where the magnetism forms. In this paper we present the effect of a curved surface on the evolution of magnetism in ultrathin iron films. Nominally 70 Å thick iron film was deposited in 9 steps on 3 different types of templates: a) A monolayer of silica spheres with 25 nm diameter b) a monolayer of silica spheres with 400 nm diameter and for comparison a flat silicon substrate. The in-situ iron evaporation took place in an ultrahigh vacuum chamber using molecular beam epitaxy technique. After the evaporation steps, time differential nuclear forward scattering spectra, grazing incidence small angle X-ray scattering images and X-ray reflectivity curves were recorded. In order to reconstruct and visualize the magnetic moment configuration in the iron cap formed on top of the silica spheres, micromagnetic simulations were performed for all iron thicknesses. We found a great influence of the template topography on the onset of the magnetism and on the developed magnetic nanostructure. We observed individual magnetic behaviour for the 400 nm spheres which was modelled by vortex formation and collective magnetic structure for the 25 nm spheres where magnetic domains spread over several particles. Depth selective nuclear forward scattering measurements showed that the formation of magnetism begins at the top region of the 400 nm spheres contrary to the 25 nm particles were the magnetism first appears in the region where the spheres are in contact with each other.

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Dynamic Flying Height Adjustment in Hard Disk Drives Through Feedforward Control

Cited by 27 publications

References 20 publications

A review of selected topics in interferometric optical metrology

A review of selected topics in interferometric optical metrology

Two-degree-of-freedom control scheme for flying-height and tracking-position controls with thermal actuators in HDDs

Evolution of magnetism on a curved nano-surface

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