The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
Roberto Horowitz - One of the best experts on this subject based on the ideXlab platform.
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robust controller design of a dual stage Disk drive servo system with an instrumented suspension
IEEE Transactions on Magnetics, 2005Co-Authors: Xinghui Huang, Roberto HorowitzAbstract:This paper proposes a robust track-following controller design method for a dual-stage servo system in Magnetic Hard Disk drives (HDDs). The method formulates the problem of minimizing track misregistration (TMR) in the presence of plant uncertainty and variation as a multiobjective optimization problem. Tracking error minimization is naturally formulated as an H/sub 2/ norm minimization problem, while the robust stability issue is addressed by some H/sub /spl infin// norm bounds. This mixed H/sub 2//H/sub /spl infin// control problem can then be formulated as a set of linear matrix inequalities (LMIs) and be efficiently solved through convex optimization algorithms. To enhance the system's tracking performance and stability robustness, the method explicitly takes attenuation of airflow-excited suspension vibration into consideration by an inner loop fast rate damping and compensation controller that utilizes the output of a strain gauge sensor on the suspension surface. Analysis and simulation show that a system designed by this method can achieve good tracking performance while still keeping stability robustness to plant variation and high-frequency spillover.
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track following controller design of mems based dual stage servos in Magnetic Hard Disk drives
International Conference on Robotics and Automation, 2000Co-Authors: Roberto HorowitzAbstract:A decoupled controller architecture and discrete time pole placement design methodology is proposed for dual-stage servo controller design of Magnetic Hard Disk drives. The methodology was applied to the controller design of a dual-stage servo with a MEMS microactuator (MA) which rotates the slider relative to the gimbal. MIMO and SIMO controllers were designed for cases when the microactuator's relative position error signal is respectively available and not available to the control system. The effects of MA resonance variations on the stability and performance of the controller were analyzed for both cases.
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closed loop control of a microfabricated actuator for dual stage Hard Disk drive servo systems
American Control Conference, 1998Co-Authors: David A Horsley, D Hernandez, Roberto Horowitz, A K Packard, Albert P PisanoAbstract:This paper examines a dual-stage actuation scheme for Magnetic Hard Disk-drives. The secondary actuator in this dual-stage design is a microfabricated, electrostatic actuator which has been used to position a Disk-drive slider over a 2.5 kHz closed-loop bandwidth. Actuation tests were performed using laser-Doppler vibrometer measurements of slider displacement, and both phase-lead and proportional-derivative controllers were implemented. The experimental results verify that the device has excellent linearity, suggesting that the dual-stage control system may use an observer to estimate the actuator displacement, resulting in significantly reduced implementation complexity. To this end, a SIMO dual-stage control system which uses only position error signal (PES) measurements is presented, and compared to a MIMO control system which utilizes both the PES and measurements of the micro-actuator displacement.
Michael J Carey - One of the best experts on this subject based on the ideXlab platform.
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State-of-the-Art Magnetic Hard Disk Drives
MRS Bulletin, 2006Co-Authors: Iain R Mcfadyen, Eric E. Fullerton, Michael J CareyAbstract:Magnetic recording has progressed dramatically over the last 50 years, with an increase of almost eight orders of magnitude in the amount of information stored per unit area of Disk space. Two key enablers of this progress have been the recording medium and the read-back head. This article reviews the current state of the art in multilayer thin-film longitudinal recording media and giant magnetoresistive (GMR) read heads, with particular emphasis on the nanostructured Magnetic materials that are key to today's high-performance Hard Disk drives.
Guoxiao Guo - One of the best experts on this subject based on the ideXlab platform.
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a new approach to the design of mode switching control in Hard Disk drive servo systems
Control Engineering Practice, 2002Co-Authors: Venkatakrishnan Venkataramanan, Ben M Chen, Tong Heng Lee, Guoxiao GuoAbstract:In a modern large-capacity Magnetic Hard Disk drive (HDD), both fast track seeking and perfect positioning of the read/write head are required. Mode switching control (MSC) approaches are widely used to meet these requirements. This paper proposes a new approach in designing MSC with an application to HDD servo systems. The proposed scheme uses a proximate time-optimal servomechanism in the track seeking mode, and a robust perfect tracking (RPT) controller in the track following mode. Unlike the conventional MSC approaches, the new method does not require an initial value compensation during mode switching. This is because the RPT controller in the second stage is capable of rendering the Lp-norm ð1ppoNÞ of the resulting tracking error arbitrarily small in the presence of external disturbances and initial conditions. Simulation and experimental results show that the proposed method improves the seek and settling time by about 10% over the conventional approaches. r 2002 Elsevier Science Ltd. All rights reserved.
Iain R Mcfadyen - One of the best experts on this subject based on the ideXlab platform.
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State-of-the-Art Magnetic Hard Disk Drives
MRS Bulletin, 2006Co-Authors: Iain R Mcfadyen, Eric E. Fullerton, Michael J CareyAbstract:Magnetic recording has progressed dramatically over the last 50 years, with an increase of almost eight orders of magnitude in the amount of information stored per unit area of Disk space. Two key enablers of this progress have been the recording medium and the read-back head. This article reviews the current state of the art in multilayer thin-film longitudinal recording media and giant magnetoresistive (GMR) read heads, with particular emphasis on the nanostructured Magnetic materials that are key to today's high-performance Hard Disk drives.
J Windeln - One of the best experts on this subject based on the ideXlab platform.
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raman spectroscopy measurements of dc magnetron sputtered carbon nitride a c n thin films for Magnetic Hard Disk coatings
Diamond and Related Materials, 2000Co-Authors: M Neuhaeuser, H Hilgers, P Joeris, R White, J WindelnAbstract:Abstract As a protective coating for Hard Disks in Magnetic storage applications, amorphous carbon nitride (a-C:N) thin films have proved superior to DLC (diamond-like carbon) a-C:H films in terms of durability, wear-resistance and adhesion properties. In this study, we present Raman spectroscopy investigations of a-C:N films which were produced by DC-magnetron sputtering systems. The layers were deposited with a variable nitrogen content, thickness and substrate temperature. Raman measurements were carried out with two different excitation lasers at wavelengths of 488 and 532 nm. The spectra show that besides the typical carbon D- and G-bands, two other characteristic bands are present at approximately 690 and 1090 cm−1. The meaning and identification of these bands is not clear in the literature. In order to obtain more information, the films were also characterized by various analytical techniques, e.g. time-of-flight secondary ion mass spectrometry (ToF-SIMS), Auger electron spectroscopy (AES), ellipsometry, and n+k optical measurements. The Raman G-band position shows a systematic shift with the varying nitrogen content of the films. A comparison of layer thickness and the total area of D-, G- and 1090 cm−1 bands also shows a significant correlation. The results offer Raman spectroscopy as a possible monitoring tool for carbon nitride coatings in the production of Magnetic Hard Disk drives.
