Optimal Design of HDD Air-Lubricated Slider Bearings for Improving Dynamic Characteristics and Operating Performance

2000 ◽  
Vol 123 (3) ◽  
pp. 541-547 ◽  
Author(s):  
Tae-Sik Kang ◽  
Dong-Hoon Choi ◽  
Tae-Gun Jeong
Keyword(s):  
Steady State ◽  
Dynamic Characteristics ◽  
Optimization Technique ◽  
Operating Performance ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Weighting Method ◽  
Lubrication Equation ◽  
Target Values

Flying attitudes of the slider, which are flying height, pitch, and roll, are affected by air-flow velocity, skew angle, and manufacturing tolerances. In the traditional design process of air-bearing surfaces, we have considered only the steady state flying attitude over the recording band. To reduce the flying height variation during track seek as well as in steady state, we design a new shape for air-bearing surfaces. An optimization technique is used to improve the dynamic characteristics and operating performance of the new air-bearing surface shapes. The quasistatic approach is used in the numerical simulation of the track seek operation because the skew angle effect dominates the inertial effect even at high seek velocities. The perturbation method is applied to the lubrication equation to obtain the air-bearing stiffness. We employ the method of modified feasible directions and use the weighting method to solve the multicriteria optimization problem. The optimally designed sliders show enhanced flying and dynamic characteristics. The steady state flying heights are closer to the target values and the flying height variations during track seek operation are smaller than those for the original ones. The pitch and roll angles are kept within suitable ranges over the recording band during track seek operation as well as in steady state. The air-bearing stiffnesses of the optimally designed sliders are larger than those of the original ones.

Design Optimization of the Taper-Flat Slider Positioned by a Rotary Actuator

1995 ◽  
Vol 117 (4) ◽  
pp. 588-593 ◽  
Author(s):  
Sang-Joon Yoon ◽  
Dong-Hoon Choi
Keyword(s):  
Optimization Technique ◽  
Leading Edge ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Optimum Configuration ◽  
Rotary Actuator ◽  
Design Variables ◽  
Augmented Lagrange Multiplier ◽  
Typical Configuration

In this paper, an optimization technique is utilized to find an optimum configuration of the taper-flat slider positioned by a rotary actuator for enhanced static air-bearing characteristics. The aim of optimization consists in simultaneously minimizing the variation in flying height from a target value, maximizing the smallest pitch angle, and minimizing the largest roll angle, over the entire magnetic recording band. As the design variables, the leading edge taper angle and rail width of a taper-flat slider, and the skew angle at the inside track are chosen since they seem to be the most influential parameters on air-bearing characteristics. The optimum design variables are automatically obtained by using the augmented Lagrange multiplier method, and the static characteristics of the optimally designed sliders are found to be superior to those of the taper-flat sliders of typical configuration over the entire recording band. Results obtained for three taper-flat slider models are reported, showing the effectiveness of the proposed design scheme.

Heater AC Voltage Induced Flying Height Modulations

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Wei Hua ◽  
Kang Kee Ng ◽  
Shengkai Yu ◽  
Weidong Zhou ◽  
Kyaw Sett Myo
Keyword(s):  
Electrostatic Force ◽  
Laser Doppler Vibrometer ◽  
Drive Level ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Frequency Method ◽  
Disk Interface ◽  
Height Control ◽  
Disk Contact

For a thermal flying-height control (TFC) slider, its heater is usually provided with DC voltage. However, recently, both DC and AC voltages may be supplied to the heater. Unlike supplying AC voltage to the slider and disk in the past, the AC voltage to the heater will not only produce a thermal protrusion on the slider, but also leaves a part of the AC voltage on the slider/disk interface. The voltage acts as the electrostatic force and can be used for further control of the slider, even in the drive level. Simulations show that the flying height modulation is highly related to the AC frequency. By sweeping the AC frequencies while monitoring the flying height and pitch angle modulations, the first and second pitch modes of air bearing frequencies can be experimentally obtained without slider/disk contact. The roll mode frequency is also obtainable when the skew angle is not zero. The simulation results agree well with the experimental results obtained by a laser Doppler vibrometer (LDV). Therefore, the sweeping AC frequency method provides a practical scheme to obtain the air bearing frequencies without any slider/disk contact, even in the drive level.

Numerical Solution of the Boltzmann Based Lubrication Equation for the Air-Bearing Interface Between a Skewed Slider and a Disk With Discrete Data Tracks

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
James White
Keyword(s):  
Numerical Solution ◽  
Data Storage ◽  
Knudsen Number ◽  
Numerical Solutions ◽  
Disk Surface ◽  
Air Bearing ◽  
Skew Angle ◽  
Lubrication Equation ◽  
Highly Nonlinear ◽  
Discrete Track

Discrete track recording (DTR) is a method for increasing the recording density of a data storage disk by use of a pattern arrangement of discrete tracks. The DTR track structure consists of a pattern of very narrow concentric raised areas and recessed areas underneath a magnetic recording layer. In order to design the air-bearing slider platform that houses the magnetic transducer for DTR application at very low fly heights, the influence of the disk surface topography as a surface roughness effect must be taken into account. This paper is focused on the numerical solution of the roughness averaged lubrication equation reported recently in the work of White (2010, “A Gas Lubrication Equation for High Knudsen Number Flows and Striated Rough Surfaces,” ASME J. Tribol., 132, p. 021701) and is specialized for the influence of discrete disk data tracks on the recording head slider-disk air-bearing interface subject to a nonzero skew angle formed between the slider longitudinal axis and the direction of disk motion. The generalized lubrication equation for a smooth surface bearing and appropriate for high Knudsen number analysis is quite nonlinear. And including the averaging process required for treatment of a nonsmooth disk surface, as well as the rotational transformation required to allow for a nonzero skew angle, increases further the nonlinearity and general complexity of the lubrication equation. Emphasis is placed on development of a numerical algorithm that is fast, accurate, and robust for air-bearing analysis of complex slider surfaces. The numerical solution procedure developed utilizes a time integration of the lubrication equation for both steady-state and dynamic analyses. The factored-implicit scheme, a form of the more general alternating-direction-implicit numerical approach, was chosen to deal with the two-dimensional and highly nonlinear aspects of the problem. Factoring produces tightly banded coefficient matrices and results in an algorithm that is second-order accurate in time while requiring only the solution of tridiagonal systems of linear equations in advancing the computation from one time level to the next. Numerical solutions are presented that demonstrate the performance of the computational scheme and illustrate the influence of some discrete track parameters on skewed air-bearing performance as compared with a flat surface data storage disk.

STATIC AND DYNAMIC ANALYIS OF AIR BEARING SLIDER FOR SMALL FORM FACTOR DRIVES

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1391-1396 ◽  
Author(s):  
B. J. SHI ◽  
D. W. SHU ◽  
B. GU ◽  
G. X. LU ◽  
M. R. PARLAPALLI ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Hard Disk Drives ◽  
Flying Height ◽  
Outer Diameter ◽  
Air Bearing ◽  
Skew Angle ◽  
Rotating Speed ◽  
Air Bearing Slider ◽  
Small Form Factor ◽  
Shock Simulation

As the areal recording density increases in hard disk drives (HDDs), the flying physical spacing between the head and the disk decreases and the likelihood of head-disk contact during full speed rotation increases. Therefore, the simulation and modeling of the air bearing slider with ultra-low flying heights becomes an important issue for the operational shock simulation. The static/dynamic properties, including the influence of the radial position and the skew angle of the slider, the rotating speed of the disk, and the shock simulation, of the air bearing slider were analyzed. Generally speaking, for a given rotating speed of the disk, as the slider moves from the inner diameter to the outer diameter, the maximum contact pressure, the skew angle, the pitch angle, and the maximum air bearing pressure increase; while the flying height decreases. These trends are strengthened by a faster rotating speed of the disk. There are obvious oscillations in the air bearing force and the minimum spacing when contact occurs during a shock.

Flying Characteristics of the Transverse and Negative Pressure Contour (“TNP”) Slider Air Bearing

1997 ◽  
Vol 119 (2) ◽  
pp. 241-248 ◽  
Author(s):  
J. W. White
Keyword(s):  
Negative Pressure ◽  
Ambient Pressure ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Disk Radius ◽  
Pressure Contour ◽  
Side Rail ◽  
Slider Air Bearing ◽  
Bearing Stiffness

The TNP contour air bearing slider is composed of oversized transverse pressure contour (TPC) outer rails and a central negative pressure (NP) cavity. The NP cavity is separated from the TPC rails by an ambient pressure reservoir which serves two functions. First, it prevents direct hydrodynamic interaction between the various component air bearing surfaces and thus, eliminates pressure distortion and dilution, common causes of problems related to flying height and roll angle control. Second, the ambient reservoir allows the TPC rails and NP cavity to be configured and dimensioned independently so that they will track each other with a nearly constant force difference, resulting in a flying height that has significantly reduced sensitivity to altitude change. The multi-function TPC sections of the outside rails are able to overcome the effects of a changing radius and wide skew angle variation over the disk radius as well as a changing vacuum load and asymmetry of the NP cavity pressure, in order to provide a truly constant low flying height over the entire data surface. The combination of a high air bearing stiffness and a gradually developing cavity vacuum as disk velocity increases produces a rapid slider take-off from the disk surface. Dynamic stability of the TNP slider air bearing is enhanced by the unusual combination of a high air bearing stiffness and high air film damping in each of the three slider excursion modes. Finally, the TNP slider experiences a reduced sensitivity of flying height to manufacturing and operational tolerances as compared to non-NP type sliders. The entire TNP slider air bearing is created by a two-etch process. A shallow etch creates the TPC sections and leading edge step. A deeper etch forms the NP cavity, ambient pressure reservoir, and outermost edge of each side rail.

Air Bearing Flying Characteristics on Patterned Media

2007 ◽  
Author(s):  
Wei Peng ◽  
Robert M. Crone ◽  
Emil Esmenda ◽  
Yiao-Tee Hsia
Keyword(s):  
Steady State ◽  
Air Bearing ◽  
Skew Angle ◽  
Simulation Code ◽  
Noticeable Effect ◽  
Patterned Media ◽  
Fly Height ◽  
Height Drop

The air bearing steady-state flying characteristics on patterned media has been studied with a proprietary air bearing simulation code. Variation of minimum fly height with relative pattern-to-slider skew has been characterized at slider positions (ID, MD, OD). The results show that at the steady state minimum fly heights drop with introducing the pattern. Furthermore, the pattern-to-slider skew angle has a noticeable effect on the fly height drop, while the maximum fly height drop occurs on radial servo patterns.

Air Bearing Models and Solutions for Sub-5 nm Spacings

2001 ◽  
Author(s):  
D. B. Bogy ◽  
Lin Wu
Keyword(s):  
Boundary Condition ◽  
Slip Velocity ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Asperity Contact ◽  
Air Bearing ◽  
Lubrication Equation ◽  
New Equation ◽  
Physical Phenomena ◽  
Flying Attitude

Abstract When the flying height is below 5 nm, some physical phenomena that can be ignored for higher flying sliders need to be included in the modeling equations. Another challenging issue is the unavoidable asperity contact problem. It is known that zero spacing at asperities may cause some of the existing modified Reynolds equations to predict unphysical unbounded contact pressure singularities. In this paper we first review the source of these pressure singularities, showing which models have this problem and which do not. We also review here a new derivation of a compressible lubrication equation by using a different slip velocity boundary condition, in which additional slippage at the gas-solid interface due to pressure gradient is introduced. The new equation is free of any contact singularity [1]. Next we review our recent work on the non-negligible effect of the intermolecular forces on the slider’s flying attitude when the spacing is below 5 nm [2]. The additional force is attractive until the spacing is below about 0.1 nm for example and then it is repulsive. Finally we show the effect of these new force contributions on the flying attitude of a low flying slider.

An Optimum Design of the Transverse Pressure Contour Slider for Enhanced Flying Characteristics

1997 ◽  
Vol 119 (3) ◽  
pp. 520-524 ◽  
Author(s):  
Sang-Joon Yoon ◽  
Dong-Hoon Choi
Keyword(s):  
Optimum Design ◽  
Design Method ◽  
Optimization Technique ◽  
Flying Height ◽  
Step Width ◽  
Skew Angle ◽  
Sqp Method ◽  
Design Synthesis ◽  
Transverse Pressure ◽  
Design Variables

This paper proposes a design method for determining the configuration of a TPC slider by using an optimization technique in order to meet the desired flying characteristics over the entire recording band. The desired flying characteristics considered in this study are to minimize the variation in flying height from a target value, to maintain the pitch angle as large as possible, to keep the roll angle as small as possible, and to keep the outside rail to fly lower than the inside rail. The design variables selected are left-side step width, pad width, right-side step width, side step depth, front taper height, and pivot offset in the transverse direction of the slider. The sequential quadratic programming (SQP) method in Automated Design Synthesis (ADS) is used to efficiently find the optimum design variables which simultaneously meet all the desired flying characteristics. To validate the suggested design method, a computer program is developed and applied to the configuration design of two TPC slider models positioned by a rotary actuator. The optimum configurations of each slider model are automatically obtained for three different target flying heights with the same predefined skew angle range without any difficulty. This shows the effectiveness of the proposed design method in comparison with the conventional one based on the parametric study.

Study of Temperature Effect on Servovalve-Controlled Fuel Metering Unit

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Bin Wang ◽  
Haocen Zhao ◽  
Ling Yu ◽  
Zhifeng Ye
Keyword(s):  
Steady State ◽  
Temperature Variation ◽  
Dynamic Characteristics ◽  
Numerical Study ◽  
Step Response ◽  
Fuel Temperature ◽  
Wide Range ◽  
Fuel Rate ◽  
Testing Condition ◽  
The Given

It is usual that fuel system of an aero-engine operates within a wide range of temperatures. As a result, this can have effect on both the characteristics and precision of fuel metering unit (FMU), even on the performance and safety of the whole engine. This paper provides theoretical analysis of the effect that fluctuation of fuel temperature has on the controllability of FMU and clarifies the drawbacks of the pure mathematical models considering fuel temperature variation for FMU. Taking the electrohydraulic servovalve-controlled FMU as the numerical study, simulation in AMESim is carried out by thermal hydraulic model under the temperatures ranged from −10 to 60 °C to confirm the effectiveness and precision of the model on the basis of steady-state and dynamic characteristics of FMU. Meanwhile, the FMU testing workbench with temperature adjustment device employing the fuel cooler and heater is established to conduct an experiment of the fuel temperature characteristics. Results show that the experiment matches well with the simulation with a relative error no more than 5% and that 0–50 °C fuel temperature variation produces up to 5.2% decrease in fuel rate. In addition, step response increases with the fuel temperature. Fuel temperature has no virtual impact on the steady-state and dynamic characteristics of FMU under the testing condition in this paper, implying that FMU can operate normally in the given temperature range.

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