Disk Spindle Research Articles

Influence of temperature on the rheological behavior of industrialized honey

In the present work, the effect of temperature on the rheological properties of the industrialized honey of three different high-trade brands in the northern, central and southern Lima markets was studied. The physicochemical characteristics of water activity, specific gravity, moisture content, brix degrees, refractive index and pH were analyzed. No significant difference was found between the values ​​of the physicochemical properties within and between the groups of the commercial brands analyzed (p> 0.05). The industrialized honey was tested with a Brookfield RVDV-E concentric viscometer using a flat disk spindle at five temperature levels from 20 ºC to 60 ºC, and the influence of temperature with dynamic or absolute viscosity was studied. Through the rheogram, a behavior of a Newtonian fluid was observed. For all samples it was found that the mean absolute viscosity decreases with temperature at 20 ºC (7430 mPa∙s), 30 ºC (2636 mPa∙s), 40 ºC (955 mPa∙s), 50 ºC (440 mPa∙s) and 60 ºC (267 mPa∙s). The dependence of the viscosity with the temperature was described by a mathematical exponential model of three constants proposed in this investigation that gave a good fit, obtaining a coefficient of determination of 0.9999. The activation energy value calculated and within the temperature range tested was 68.73±0.129 kJ.mol-1. The results obtained in this study are of great interest to the industry that manipulates and formulates edible foods based on this type of product.

TuA-2-3 Experimental and Numerical Investigation of Hydrocarbon Transfer Mechanism at the Head-Disk Interface

In hard disk drives, hydrocarbon oils are used to lubricate the disk spindle and the actuator pivot. During disk drive usage, oil molecules can escape, resulting in contamination of the head-disk interface. In this study, experimental investigation and molecular dynamics simulations are used to study hydrocarbon contamination at the head-disk interface in hard disk drives. A "two-step" transfer mechanism is assumed: Hydrocarbon molecules first condense onto the disk surface from the vapor phase, and then transfer to the slider surface in the absence of head-disk contacts. Experimental results and molecular dynamics simulations verify the assumed transfer mechanism.

Influence of dietary fiber addition on some properties of yoghurt

AbstractThe objective of this work was to study the effect of different dietary fibers on rheological properties of yoghurts fortified with these fibers [1, 2, 3]. Commercial fibers from apple and inulin were used. The effect of addition of dietary fibers in yoghurt [4, 5] was investigated by a rotational viscometer, Brookfield viscometer (Brookfield Engineering Inc., Model RV-DV I Prime) with RV spindles. The Brookfield viscometer DV I Prime with disk spindles represents an easy and cheap method for rheological characterization of non-Newtonian fluids, in this case of yoghurt. Syneresis and pH did not show any difference, while only apple fiber yoghurt showed colour differences compared to control.

저전력과 응답시간 향상을 위한 하이브리드 하드디스크의 입출력 기법

최근 전력소모와 읽기 성능이 우수한 Solid state disk(SSD)가 많이 사용되고 있으나 가격이 고가이고 삭제 및 쓰기 연산의 효율이 낮은 것이 단점이다. 이것을 보완하기 위한 저장장치의 일종이 하이브리드 하드디스크 (H-HDD: Hybrid Hard disk drive)인데 하드디스크 내부에 플래시 메모리(NVCache: Non-volatile Cache)를 장착하여 디스크블록의 캐시로 사용한다. 본 논문에서는 H-HDD의 저전력과 응답시간을 향상시키기 위해 NVCache의 선반입 및 관리 기법을 제안한다. 제안하는 기법은 NVCache를 읽기 캐시를 위주로 사용하고 쓰기캐시는 디스크 헤드와 스핀들의 상황에 따라 쓰기 연산을 지원한다. 읽기 캐시의 경우 시간적, 지역적 지역성을 동시에 고려하여 선반입을 통해 응답시간과 전력 소모를 감소시키고 쓰기 캐시의 경우 디스크 스핀들의 동작 상태에 따라 NVCache에 쓰기를 실시하여 저전력과 응답성을 향상시키고자한다. 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.

Thermal Analysis and Design of Disk-Spindle Radial Repeatable Runout in Spinning Data Storage Devices

This paper presents structure thermal mechanics analysis of spindle disk assembly used in spinning magnetic data storage hard disk drives (HDDs). With the view toward understanding the underlying physics and to minimize the corresponding repeatable run-out (RRO) of track following position error signal (PES) in high track per inch (TPI) magnetic disk drives, analytical representation of thermal expansion mismatch between disk and spindle hub structure formulated in form of operators and finite element analyses (FEA) are employed in this paper. Parameter studies with analyses taken at different operational temperatures suggest that RRO can be minimized significantly when location of spindle notch, which is can be the internal feature used to position bearings to the hub structure, is properly located. RRO harmonics resulted from the thermal expansion mismatch and structure misalignments having ramping characteristics from disk outer diameter to inner diameter are studied and concluded with simple algebraic expression related to number of fasteners used in disk-spindle assembly.

Decoupled Control of a Disk-Type Rotor Equipped With a Three-Pole Hybrid Magnetic Bearing

Recently, there has been an increasing need for development of active magnetic bearing (AMB) systems of smaller size and lower energy consumption than ever, as AMBs seek for applications in compact, portable rotating machines such as hard disk spindle and artificial heart blood pump. Among others, the three-pole AMB configuration turns out to be more profitable in terms of compactness in design and low power loss than the conventional four- or eight-pole AMB. However, one of the inherent drawbacks in controller design of three-pole AMB is the strong coupling in magnetic flux between magnetic poles. It leads to the strongly nonlinear system behavior, when the equation of motion is formulated in the conventional Cartesian coordinates. In this paper, we propose use of the redundant bearing coordinates to describe the three-pole AMB system behavior, so that the potential difference controllers can be easily designed, based on the decoupled linearized control model for each pole. The proposed method is applied to control of a five-axis AMB system, which consists of a three-pole radial AMB for stabilization in the radial direction and a ring-type permanent magnet bearing for levitation in the axial and tilt directions. It is shown that simplistic equation of motion for the five-axis AMB system can be derived in the proposed redundant bearing coordinates and the resulting control equations become completely decoupled. Experiments are also carried out with the five-axis disk-type AMB system equipped with Hall diodes for measurement of the radial displacement and it is confirmed that the proposed control scheme succeeds in the run-up test.

Thermal analysis of helium-filled enterprise disk drive

Enterprise hard disk drives (HDDs) are widely used in high-end storage systems for data center. One of key performance requirements for enterprise HDDs is data access rate, which demands very high rotational speed (e.g. 15 k rpm or more) to permit fast access time. To reach such high speed, the disk spindle motor draws more power to spin and hence the temperature of HDD enclosure increases due to large windage loss. It has been known, temperature rise is one of the most fundamental factors that affect the reliability of the disk drive. In order to develop high reliable enterprise HDDs, thermal management of enterprise HDDs needs to be optimized to improve heat dissipation. One possible approach is to fill disk drive with helium because of its lower density and higher thermal conductivity. This paper investigates thermal performances of helium-filled enterprise disk drives through FEM simulations with experimental validations. Windage loss and heat convection of the HDD filled with helium and air are analysed. The simulated and measured temperature distributions of one commercial enterprise HDD with helium-filled and helium-air mixture are compared with those of an air-filled one. The results show 41% reduction of temperature rise of HDD enclosure can be achieved by filling with helium in comparison with that of air-filled HDD. It is also projected that in terms of equivalent cooling capability like air-filled HDD at 15 k rpm, helium-filled HDD spindle can spin up to 19 k rpm, which will greatly increase data access rate by 25% for future enterprise applications.

Write Failure Analysis for Bit-Patterned-Media Recording and Its Impact on Read Channel Modeling

In this paper, we present a write failure analysis for bit-patterned media recording (BPMR) with formulas derived to calculate its probability for a given set of system parameters. The write failure model derived in this work includes the effect of the recording head and media characteristics and that of a hard disk spindle motor speed variations. Such a model can help assess the performance of the writing strategy for BPMR. It is also found that since the media local parameters associated with each bit directly affect both the write failure rate and read-back signal, the read-back signal actually contains information regarding whether a bit is correctly recorded. This may be exploited by coding and detection schemes to reduce the impact of write failure on bit-error-rate performance.

Feasibility of Modeling Air Bearing as Linear Springs in Hard Disk Drive Dynamics Simulation

A model to predict the shock response of a 1.8-inch hard disk drive (HDD) is developed and validated by experiment. The head-actuator assembly (HAA), spindle disk and flexible base are included in the proposed model. The feasibility of modeling the air bearing as linear springs is investigated for HDD operating shock simulation. Result shows that as far as the vibration of the arm-suspension assembly is concerned, the air bearing between the disk and slider can be modeled by linear springs to speed up the simulation. However, if head/disk interface is concerned, the air bearing should not be modeled as linear springs in the studies of head-disk interface.

A Model for a Hard Disk Drive for Vibration and Shock Analysis

We propose a model for a hard disk drive (HDD) based on a flexible multibody dynamics formulation. All the main components in the HDD, i.e., the spindle head actuator, spindle disk, and base are considered flexible components connected by bearing joints. The model takes into account nonlinearity and discontinuity caused by the contact between the dimple and flexure. The air bearing force is obtained by solving the Reynolds equation using the finite volume method and considering Intermolecular force. We found that the intermolecular force will lower the flying height. We investigated the effect of the base stiffness on the shock tolerance of the HDD and found that a stiffer base will benefit the increase of the shock tolerance.

Reducing position error signal (PES) due to disk vibration using an air shroud

The advances in magnetic recording technology demand higher magnetic head positioning accuracy and faster disk rotation speed. However, the higher rotational speed of disk generates the greater flow-induced vibration known as disk flutter, which causes the increase of the track misregistration (TMR). To overcome the issue, an air shroud is presented to reduce disk vibration and position error signal (PES) for magnetic recording. Computational fluid mechanics simulations are performed to study the flow pattern surrounding a disk with an air shroud for different openings. The air-bearing stiffness and damping effects of the disk spindle assembly with an air shroud are evaluated. Based on the computational fluid dynamics (CFD) simulation, the air shroud is prototyped and the disk vibrations with and without the air shroud at different disk rotation speeds are experimentally investigated using a laser Doppler vibrometer (LDV). Significant disk vibration reductions are attained while a shroud is installed onto a disk at certain disk rotation speeds. PESs are also measured for the cases with and without an air shroud during servo implementation. Reductions of PESs are observed when an air shroud is installed at some disk rotation speeds.

Study of a Head Suspension with Dynamic Absorber

This paper describes a new Dynamic Absorber Suspension (DAS) structure which has a significant damping effect for the flow-induced sway mode and second torsion mode. First we designed the DAS structure for a practically used suspension by Finite Element Analysis. From frequency response function of DAS, we found that magnification factor of sway mode can be reduced to 14 dB, and that of second torsion mode is 5 dB. Next, we fabricated the DAS and measured the frequency characteristics by laser Doppler vibrometer using a hydrostatic air-bearing jig and a 3.5 inch disk spindle. As a result, we found that the DAS has a remarkable damping effect on the sway mode and second torsion mode compared with a conventional suspension with a damper sheet.

Nonplanar modeling and experimental validation of a spindle–disk system equipped with an automatic balancer system in optical disk drives

Non-planar dynamic modeling and experimental validation of a spindle–disk system equipped with an automatic ball-type balancer system (ABS) in optical disc drives are performed in this study. Recent studies about planar dynamic modeling and analysis have shown the capability of the ABS in spindle–disk assembly via counteracting the inherent imbalance. To extend the analysis to be practical, non-planar dynamic modeling are conducted in this study to re-affirm the pre-claimed capability of the ABS system, along with experiments being designed and conducted to validate the theoretical findings. Euler angles are first utilized to formulate potential and kinetic energies, which is followed by the application of Lagrange’s equation to derive governing equations of motion. Numerical simulations are next carried out to explore dynamic characteristics of the system. It is found that the levels of residual runout (radial vibration), as compared to those without the ABS, are significantly reduced, while the tilting angle of the rotating assembly can be kept small with the ABS installed below the inherent imbalance of the spindle–disk system. Experimental study is also conducted, and successfully validates the aforementioned theoretical findings. It is suggested that the users of the ABS need to cautiously operate the spindle motor out of the speeds close to the resonances associated with various degrees of freedom. In this way, the ABS could hold the expected capability of reducing vibration in all important directions, most importantly in radial directions.

Finite element modal analysis of an HDD considering the flexibility of spinning disk–spindle, head–suspension–actuator and supporting structure

This paper presents a finite element method to analyze the free vibration of a flexible HDD (hard disk drive) composed of the spinning disk–spindle system with fluid dynamic bearings (FDBs), the head–suspension–actuator with pivot bearings, and the base plate with complicated geometry. Finite element equations of each component of an HDD are consistently derived with the satisfaction of the geometric compatibility in the internal boundary between each component. The spinning disk, hub and FDBs are modeled by annular sector elements, beam elements and stiffness and damping elements, respectively. It develops a 2-D quadrilateral 4-node shell element with rotational degrees of freedom to model the thin suspension efficiently as well as to satisfy the geometric compatibility between the 3-D tetrahedral element and the 2-D shell element. Base plate, arm, E-block and fantail are modeled by tetrahedral elements. Pivot bearing of an actuator and air bearing between spinning disk and head are modeled by stiffness elements. The restarted Arnoldi iteration method is applied to solve the large asymmetric eigenvalue problem to determine the natural frequencies and mode shapes of the finite element model. Experimental modal testing shows that the proposed method well predicts the vibration characteristics of an HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head–suspension–actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of an HDD and to design a robust HDD against shock.

Vibration of hard disk drive spindle systems with distributed journal bearing forces

This paper is to analyze vibration of fluid dynamic bearing spindles with distributed journal bearing forces. The dynamical model is developed to predict the transverse vibration of the disk–spindle systems in HDD where an aspect ratio of the bearing width to the shaft length is significant and the shaft is likely flexible. In such spindles the journal bearing functions as a continuous support, providing the distributed restoring and damping forces, and is therefore modeled as distributed linear spring and damping forces through distribution functions of dynamic coefficients. Vibration analysis reveals that the spindle model with distributed bearing forces predicts the same natural frequencies for all transverse modes but higher modal damping of the rocking modes, when compared to the values predicted by the conventional model with discrete bearing forces. The difference in damping prediction is clearer for the flexible-shaft spindle whose ratio of the bearing width to the shaft length becomes larger.

Finite element modal analysis of a rotating disk–spindle system in a HDD with hydrodynamic bearings considering the flexibility of a complicated supporting structure

This paper presents a method to analyze the free vibration of a rotating disk–spindle system in a HDD with hydrodynamic bearings (HDBs) considering the flexibility of a complicated base structure by using finite element method. Finite element equations of each component of a HDD spindle system from the spinning flexible disk to the flexible base plate are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between the sleeve and hydrodynamic bearings to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. The validity of the proposed method is verified by comparing the calculated damped natural frequencies and modes with the experimental results. This research also shows that the supporting structure which includes the stator, housing and base plate plays an important role in determining the natural frequencies and mode shapes of a HDD spindle system

Experimental Evaluation of Stability and Stiffness to Unbalance Force of Disk Spindle Supported by a Plain Journal Bearing and a Pivot Bearing

We have proposed a simple disk spindle model supported by a plain journal fluid bearing at the upper part of shaft and a spherical grooved pivot bearing at the bottom of shaft and made clear that this spindle system can be stabilized by the gyro effect theoretically. In this study we manufactured three prototypes of the disk spindle composed of two 3.5 inch disk platters, a plain journal bearing and a spherical grooved pivot bearing. Then we measured radial and axial vibrations at rotational speed up to 9150 rpm. We confirmed the stability of the spindle and found that the averaged amplitude of half frequency whirl is about 30 nm. We also evaluated the NRRO and found that the tracking error due to NRRO is comparable to the conventional one. Unbalance stiffness is estimated to be larger than the conventional one if the bearing size is identical.

真円流体軸受ディスクスピンドルの実験的検証(情報機器コンピュータメカニクス2 -機構・制御,IIP2004 情報・知能・精密機器部門講演会)

We proposed a simple disk spindle assembly supported by a full cylindrical fluid journal bearing at the top of shaft and a spherical grooved pivot bearing at the bottom of shaft and made clear that the gyro effect can make this spindle stable. In this study we manufactured three prototypes of the disk spindle composed of two 3.5 inch disk platters, a full cylindrical journal fluid bearing and a spherical grooved pivot bearing. Then we measured radial vibration and axial vibration at rotational speed up to 9150 rpm. We found that the amplitude of half frequency whirl is about 30nm. We also evaluated the NRRO and bearing stiffness to unbalance force.

Non-planar dynamic modeling for the optical disk drive spindles equipped with an automatic balancer

This study presents non-planar dynamic modeling and analysis of the spindle–disk system equipped with an Automatic Ball-type Balancer (ABB) system for optical disk drives. Recent studies have shown that the ABB system owns the capability for reducing radial vibrations of the rotating spindle–disk assembly by counter-acting the inherent imbalance. To extend the analysis to be practical, non-planar dynamic modeling and analysis are conducted in this study to re-affirm the pre-claimed capability of the ABB system. Euler angles are first utilized to formulate potential and kinetic energies. Lagrange’s equations are next applied to derive governing equations of motion. Numerical simulations of non-planar motions are finally carried out to calculate two performance indices, the level of residual radial vibration and the tilting angle of the rotating assembly. It is obtained that the levels of residual vibration as compared to those without the ABB, are significantly reduced. On the other hand, the tilting angle of the rotating assembly can be kept small if the ABB is installed below the inherent imbalance of the spindle–disk system.

FREE VIBRATION ANALYSIS OF A SPINNING FLEXIBLE DISK–SPINDLE SYSTEM SUPPORTED BY BALL BEARING AND FLEXIBLE SHAFT USING THE FINITE ELEMENT METHOD AND SUBSTRUCTURE SYNTHESIS

Free vibration of a spinning flexible disk–spindle system supported by ball bearing and flexible shaft is analyzed by using Hamilton's principle, FEM and substructure synthesis. The spinning disk is described by using the Kirchhoff plate theory and von Karman non-linear strain. The rotating spindle and stationary shaft are modelled by Rayleigh beam and Euler beam respectively. Using Hamilton's principle and including the rigid body translation and tilting motion, partial differential equations of motion of the spinning flexible disk and spindle are derived consistently to satisfy the geometric compatibility in the internal boundary between substructures. FEM is used to discretize the derived governing equations, and substructure synthesis is introduced to assemble each component of the disk–spindle–bearing–shaft system. The developed method is applied to the spindle system of a computer hard disk drive with three disks, and modal testing is performed to verify the simulation results. The simulation result agrees very well with the experimental one. This research investigates critical design parameters in an HDD spindle system, i.e., the non-linearity of a spinning disk and the flexibility and boundary condition of a stationary shaft, to predict the free vibration characteristics accurately. The proposed method may be effectively applied to predict the vibration characteristics of a spinning flexible disk–spindle system supported by ball bearing and flexible shaft in the various forms of computer storage device, i.e., FDD, CD, HDD and DVD.