• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.26-28
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• 2004

The sliding mode control law provides a robust solution for general control problems. Most real systems which use a portable hard disk drive have to overcome disturbances and model uncertainties for proper operation. The chattering effect caused from unexpected oscillation can make the system be unstable. Therefore, we propose a robust control algorithm for the nonlinear second order systems with model uncertainties and disturbances. The proposed algorithm is designed following a sliding mode and observer based control. Thus the proposed algorithm has more expanded bounded region of control. Simulation results show the robustness of the proposed controller.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.174-185
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• 2005

This paper presents the design, fabrication, and testing results of a dual stage actuator system for a fine positioning of magnetic heads in magnetic disk drives. A novel rotary microactuator which is electrostatically driven and utilized as a secondary actuator was designed. The stator and rotor electrodes in the microactuator was revised to have the optimal shapes and hence produces much higher rotational torque compared with the conventional comb-shape electrodes. The microactuators were successfully fabricated using SoG(silicon on glass) processing technology, which is known as being cost-effective. The fabricated microactuator has the structural thickness of $45{\mu}m$ with the gap width of approximately $3{\mu}m$. The dynamic characteristic of microactuator/slider assembly was investigated, and its natural frequency and DC gain were measured to be 3.4kHz and 32nm/V, respectively. The microactuator/slider assembly was integrated into a HDD model V10 of Samsung Electronics Co. and a dual servo algorithm was tested to explore the tracking performance of dual stage actuator system where the LDV signals instead of magnetic head signals were used. Experimental results indicate that this system achieves the tracking accuracy of 30nm. This value corresponds to a track density of 85,000 track per inch(TPI), which is about 3 times greater than that of current hard disk drives.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.832-936
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• 1996

In this paper, we study a dynamic characteristics of HDD. HDD is constructed by spindle motor/disk unit, cover, base, E-block arm/suspension unit, and rotary actuator/voice coil motor. First, we make a FE model of spindle motor/disk unit and analyzed natural frequency/mode analytically and experimentally. Especially, the change of natural frequecy of spindle motor unit according to change of B.C is considered. Second, FE model of cover, base is made. Third, we assemble the above three FE mode, we get HEE assembly and dynamic analysis of HDD assembly is accomplished.

• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.13-18
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• 2011

As a standard of optical disk drive (ODD) was determined to Blu-ray diks (BD), researches for securing slim drive thickness, high data transfer rate and high capacity have been progressed. The actuator for applying BD is also required to have high performances, such as compatibility, slim thickness and 3-axis motion. In this paper, an asymmetric dual lens actuator is proposed to satisfy abovementioned performances. To design the actuator in a limited space, stress analysis and design of experiment (DOE) are performed to reduce weight of moving part and increase driving force and flexible mode frequency. Consequently, the final model, which is satisfied with specifications, is secured.

• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.243-250
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• 2007

This paper presents a systematic method of estimating a velocity disturbance occurring in the fine seek control system of an optical disk drive. A fine seek loop gain adjustment algorithm is introduced to accurately estimate the velocity disturbance in spite of the uncertainties of the fine actuator. The velocity disturbance can be estimated from a measurable velocity, a fine seek controller output, and a compensated fine actuator model. A robust fine seek controller can be designed by considering a minimum fine seek open-loop gain, calculated by the estimated velocity disturbance. The proposed controller design method is applied to the fine seek control system of a DVD rewritable drive and is evaluated through the experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1087-1096
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• 2011

The purpose of current study is to develop and verify the newly developed solver for analyzing rotor flow using the open-source code. The algorithm of standard solver, OpenFOAM, is improved to analyze the rotor inflow with and without fuselage. For the calculation of the rotor thrust, the virtual blade method based on the blade element method is employed. The inflow velocities on the rotor disk used to specify the effective angle of attack, have been included in the solver. The results of the current rotor inflow analysis are verified by comparing with other experimental and numerical results. It was confirmed that the modified solver provides satisfactory results for rotor-fuselage interaction problem.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.120-124
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• 2007

Helicopters and rotary-wing vehicles encounter a wide variety of complex aerodynamic phenomena and these phenomena present substantial challenges for computational fluid dynamics(CFD) models. This investigation presents the rotor aerodynamic analysis items for the helicopter development and variety aerodynamic analysis methods to provide the better solution to researchers and helicopter developers between aerodynamic problems and numerical aerodynamic analysis methods. The numerical methods to make an analysis of helicopter rotor are as below - CFD Modelling : actuator disk model, BET model, fully rotor model,... - Grid : sliding mesh, chimera mesh / structure mesh, unstructure mesh,... - etc. : panel method periodic boundary, quasi-steady simulation, incompressible,... The choice of CFD methodology and the numerical resolution for the overall problem have been driven mostly by available computer speed and memory at any point in time. The combination of the knowledge of aerodynamic analysis items, available computing power and choice of CFD methods now allows the solution of a number of important rotorcraft aerodynamics design problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.217-224
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• 2000

This paper proposes a new type of HDD suspension integrated with shape memory alloy(SMA) actuator in order to prevent the friction between the slider and the disk. A finite element analysis is undertaken to investigate modal characteristics of the proposed self loading/unloading slider. The dynamic model is formulated and its validity is proved by comparing the predicted displacement transmissibility with the measured one. A control model is then established by integrating experimentally-obtained SMA actuator dynamics. Subsequently, a sliding mode controller is designed to achieve non-contact start/stop(Non CSS) modes, and control results are presented in time domain.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.541-549
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• 2007

In the case of control for mechanical systems, it is highly useful to be able to provide a compact model of the mechanical system to control engineers using the smallest number of state variables, while still providing an accurate model. The reduced mechanical model can then be inserted into the complete system models and used for extended system-level dynamic simulation. In this paper, moment-matching based model order reductions (MOR) using Krylov subspaces, which reduce the number of degrees of freedom of an original finite element model via the Arnoldi process, are presented to study the eigenvalue and frequency response problems of a HDD actuator and suspension system.

• Journal of Institute of Convergence Technology
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• v.1 no.2
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• pp.6-15
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• 2011

This paper reports the design and fabrication of a micro-electro-mechanical-system(MEMS)-based electrostatic angular microactuator for a dual-stage servo. The proposed actuator employs a novel electrode pattern named "skewed electrode array(SEA)" scheme. It is shown that SEA has better linearity than a parallel plate type actuator and stronger force than a comb-drive based actuator. The moving and the fixed electrodes are arranged to make the driving force perpendicular to the rotating moment of arm. By changing the electrode overlap length, the magnitude of electrostatic force and stable displacement will be changed. In order to optimize the design, an electrostatic FE analysis was carried out and an empirical force model was established for SEA. A new assembly method which will allow the active electrodes to be located beneath the slider was developed. The active electrodes are connected by inner and outer rings lifted on the base substrate, and the inner and outer rings are connected to platform on which the slider locates. Electrostatic force between active electrodes and platform can be used for exiting out of plane modes, so this provides the possibility of the flying height control. A microactuator that can position the pico-slider over ${\pm}0.5{\mu}m$ using under 20 volts for a 2 kHz fine-tracking servo was designed and fabricated using SoG process.