• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.846-852
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• 2004

This paper proposes a method to calculate the characteristics of a coupled hydrodynamic journal and thrust bearing of a HDD spindle motor. The governing equations for the journal and thrust bearings are the two dimensional Reynolds equations in ${\theta}z$ and $r\theta$ planes, respectively. Finite element method is appropriately applied to analyze the coupled journal and thrust bearing by satisfying the continuity of mass and pressure at the interface between the journal and thrust bearings. The pressure in a coupled bearing is calculated by applying the Reynolds boundary condition and compared with that by using the Half-Sommerfeld boundary condition. The static characteristics are obtained by integrating the pressure along the fluid film. The flying height of spindle motor is measured to verify the proposed analytical result. This research shows that the proposed method can describe HDB in a HDD system more accurately and realistically than the separate analysis of a journal or thrust bearing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.748-752
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• 2004

Fluid dynamic bearings (FDBs) have been replacing ball bearings of the HDD spindle motor very rapidly. But there are several demerits of HDB, such as high friction torque, variable viscosity of the fluid lubricant depending on operating temperature, low stiffness, and etc. Eccentricity is one of the major parameters which affects the static and dynamic characteristics. As the static eccentricity is larger, the stiffness and the damping coefficients become bigger. But friction torque is relatively unaffected by the static eccentricity. This research proposes a new type of journal bearing with asymmetric journal grooves which results in better dynamic characteristics. The static and dynamic characteristics of the new journal bearing are investigated by solving the Reynolds' equation with FEM, and the transient analysis is performed to predict the dynamic behavior of rotor by solving the equations of motion of a HDD spindle system with Runge-Kutta method. The result shows that the proposed Journal bearings have much bigger stiffness and damping coefficients compared with the conventional symmetric ones. And consequently, it has smaller whirl radius and tilting angle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.319.1-319
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• 2002

A frequency-domain PES estimation and its prediction method are proposed for the tightly-coupled servo/mechanical design of high-TPI HDD system above 100kTPI. The major two disturbance energies which are related with mechanical vibrations inside of HDD are used to predict the drive-level PES, while considering closed-loop servo dynamics. One is the torque disturbance which mainly comes from aerodynamic excitation of HSA system and the other is the displacement disturbance from disk-spindle dynamics. (omitted)

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.852-859
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• 2003

In order to meet the growing demands for higher storage density as well as lower noise level, the spindles in hard disk drives are to be supported by hydrodynamic bearings in place of conventional ball-type ones. However, the existing models are inappropriate to apply to accurate prediction of vibration characteristics because the HDD spindle tends to take quite a complex shape to secure its performance and cost-effectiveness. In this context, this paper treats analysis of free and forced vibrations of such-designed HDD spindles based on more sophisticated models and validations via experiments. Remarkably, to this end all the components in the system are modeled as elastic adopting the finite element method.

• Journal of KSNVE
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• v.9 no.5
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• pp.1029-1035
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• 1999

This paper relates to the flexural vibration analysis of slender spindle systems with multiple thin disks, supported by the ball bearings by means of the finite element method. Each system component is analytically modeled taking into account its flexibility and also the centrifugal effect especially for the disk. In order to show the rapid convergence rate and accuracy of the proposed approach, an experimental set-up is built to be versatile. In two distinct cases, its natural modes are numerically computed using only a small number of total element meshes as the shaft rotational speed is varied, and verified through experimental frequency response function obtained by the impact test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.598-604
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• 2003

In order to meet the growing demands for higher storage density as well as lower noise level, the spindles In hard disk drives are to be supported by hydrodynamic bearings in place of conventional ones. However, the existing models are inappropriate to apply to accurate Prediction or vibration characteristics because the Inn spindle tends to take quite a complex shape to secure the performance of the new type bearings. In this context, this paper treats analysis of free and forced vibrations of such-designed HDD spindles based on more sophisticated models and validation by means of experiments. Remarkably, to this end each component in the system is modeled as elastic adopting the finite element method.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.23-31
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• 2011

Recently, Solid state disk is mainly used because this device has lower power consumption as well as higher response time. But it features higher price and lower performance at delete and write operations compared with HDD. To compensate this defect, Hybrid hard disk with internal non-volatile flash memory was issued. This NVCache is used as a kind of cache for disk blocks. In this paper, an I/O scheme for H-HDD is proposed for improving low power consumption as well as response time. Our method is to use this NVCache as read cache mainly and write cache when write requests are concentrated. In read cache operation, disk blocks with higher priority determined on basis of time as well as spatial localities are prefetched, which can improve response time. The write operation is conducted only at write peak time as disk spindle up costs higher battery power as well as response time. Experiments results show that the suggested method can improve response time of H-HDD and lower the power consumption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.122-127
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• 2002

A frequency-domain PES estimation and its prediction method are proposed for the tightly-coupled servo/mechanical design of high-TPI HDD system above 100 kTPI. The major two disturbance energies which are related with mechanical vibrations inside of HDD are used to predict the drive-level PES, while considering closed-loop servo dynamics. One is the torque disturbance which mainly comes from aerodynamic excitation of HSA system and the other is the displacement disturbance from disk-spindle dynamics. In order to obtain the accurate error transfer function of closed-loop servo control, the plant model is measured by accurate experiment. The measured PES is compared with predicted one in terms of frequency-domain PES spectrum and its standard variation value. It is proved that the proposed frequency-domain PES estimation/prediction method is capable of predicting drive-level PES of high-TPI hard disk drive.

• KSTLE International Journal
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• v.4 no.1
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• pp.18-26
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• 2003

Recently, fluid dynamic bearings (EDBs) have important applications in miniature rotating machines such as those found in the computer information storage industry, due to their outstanding low acoustic noise and NRRO (Non-Repeatable Run Out) characteristics. This research investigates the dynamic behavior of fluid dynamic bearings composed of hydrodynamic herringbone groove journal and spiral groove thrust bearing. The five degrees of freedom of FDB are considered to describe the real motion of a general rotor bearing system. The Reynolds equation and five nonlinear equations of motion for the dynamic behavior are solved simultaneously, The incompressible Reynolds equation is solved by using the finite element method (FEM) in order to calculate the pressure distribution in a fluid film and the five equations of motion by using the Runge-Kutta method. The reaction forces and moments are obtained by integrating the pressure along the fluid film. Numerical results are validated by comparing with the previously published experimental and numerical results. As a result the dynamic behavior of FDB spindle such as orbit, floating height, and angular orbit is investigated by considering the conical motion under the static and dynamic load conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.339.2-339
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• 2002

In recent years, the demand of mobile device, such as digital camera, camcoder and PDA, increases remarkably. So, requirements of the mobile information data storage used in the mobile devices increase noticeably also. 1" micro storage is a kind of mobile storage, which has a CF type II form factor, and the similar structure of the general 3.5" HDD. In this paper, we performed the vibration analysis and experimental study of disk-spindle system in 1 " micro storage, such as measurement of the NRRO of the disk, and modal analysis. (omitted)