Bifurcation Analysis of the Load/Unload Systems With Multiple Flying Height States

2006 ◽  
Vol 128 (3) ◽  
pp. 665-669 ◽  
Author(s):  
Pyung Hwang ◽  
Polina V. Khan
Keyword(s):  
Disk Drive ◽  
Stability Diagram ◽  
Numerical Continuation ◽  
Continuation Methods ◽  
Flying Height ◽  
Air Bearing ◽  
Bearing Force ◽  
Characteristic Values ◽  
The Stability ◽  
The Relationship

The load/unload behavior of the hard disk drive slider is studied in terms of the air bearing static characteristics. The application of numerical continuation methods to calculate spacing diagrams is proposed. The algorithm that detects multiple flying height states and fold points is developed. The relationship between suspension force x-offset and critical preload is found for femto size sliders. The second fold corresponding to the critical preload for unloading is found in the negative air bearing force area. The range of x-offsets and preloads where bi-stable phenomenon exists is depicted on the stability diagram. The perturbation method is used to check the dynamic system characteristic values near the fold points and to determine the stability of the solution branches. The present procedure can be employed to study the multiple flying height states in the terms of any other pair of parameters besides the preload and x-offset.

Bifurcation Approach to the Analysis of Multiple Flying Height States in Load/Unload Hard Disk Drive Systems

2005 ◽  
Author(s):  
Pyung Hwang ◽  
Polina V. Khan
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Numerical Continuation ◽  
Continuation Methods ◽  
Multiple Equilibrium ◽  
Flying Height ◽  
Drive Systems ◽  
The Relationship ◽  
Force Equilibrium

The application of numerical continuation methods to calculate suspension force-equilibrium position curve for hard disk drive sliders is proposed. The method efficiently detects multiple equilibrium positions. The relationship between suspension force offset and critical preload is found for the femto slider.

Analysis of Pressure Distribution on Head Disk Air Bearing Slider Involved Van der Waals Force

2013 ◽  
Vol 419 ◽  
pp. 111-116
Author(s):  
Hong Rui Ao ◽  
Ming Dong ◽  
Xi Chao Wang ◽  
Hong Yuan Jiang
Keyword(s):  
Pressure Distribution ◽  
Van Der Waals ◽  
Disk Drive ◽  
Van Der Waals Force ◽  
Flying Height ◽  
Force Model ◽  
Air Bearing ◽  
Analysis Process ◽  
Before And After ◽  
Bearing Force

This paper focuses on the pressure distribution on the surface of slider in hard disk drive when its flying height is in nanoscale. The gas rarefaction effect and van der Waals force are involved in the analysis process. Here the air bearing force model is based on F-K model and we establish the equation of van der Waals force between the head and disk. Using the finite element method, the modified Reynolds equation and the van der Waals force were obtained. The air bearing force on slider before and after the van der Waals force involved were compared. The results illustrate that the effect of van der Waals force on the air bearing force is different according to the slider shapes and flying heights. As a result, van der Waals force plays an important role when the flying height of slider is below 10 nm.

Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part II—Dependence of the Stability on Hamaker Constant, Suspension Preload and Pitch Angle

2005 ◽  
Vol 128 (1) ◽  
pp. 203-208 ◽  
Author(s):  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Pitch Angle ◽  
Dynamic Performance ◽  
Hard Disk Drives ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Total Force ◽  
Air Bearing ◽  
Force Increase ◽  
The Stability ◽  
Fly Height

Intermolecular and surface forces contribute significantly to the total forces acting on air bearing sliders for flying heights below 5 nm. Their contributions to the total force increase sharply with the reduction in flying height, and hence their existence can no longer be ignored in air bearing simulation for hard disk drives. Various experimentally observed dynamic instabilities can be explained by the inclusion of these forces in the model for low flying sliders. In this paper parametric studies are presented using a 3-DOF model to better understand the effect of the Hamaker constants, suspension pre load and pitch angle on the dynamic stability/instability of the sliders. A stiffness matrix is used to characterize the stability in the vertical, pitch, and roll directions. The fly height diagrams are used to examine the multiple equilibriums that exist for low flying heights. It has been found that the system instability increases as the magnitude of the van der Waals force increases. It has also been found that higher suspension pre load and higher pitch angles tend to stabilize the system.

Air Bearing Pushback in Heat Assisted Magnetic Recording

2019 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Chanh Nguyen ◽  
Youfeng Zhang ◽  
Yeoungchin Yoon
Keyword(s):  
Magnetic Recording ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Flying Height ◽  
Air Bearing ◽  
Magnetic Media ◽  
Heat Assisted Magnetic Recording ◽  
Height Control ◽  
Different Dimensions

Abstract The air bearing surface is critical to the spacing control in current hard disk drives (HDDs). Thermal protrusions, including thermal flying height control (TFC) and writer coil protrusion, drive the reader/writer elements closer to the magnetic media. The spacing control actuation efficiency depends on the air bearing push back response after the TFC or writer protrudes. In the next generation hard disk drive technology, heat assisted magnetic recording (HAMR), laser induced protrusions further complicate the spacing control. The laser induced protrusions, such as the localized NFT protrusion and a wider change of the crown and camber, have very different dimensions and transient characteristics than the traditional TFC and writer protrusion. The dimension of the NFT protrusion is relatively smaller, and the transient is much faster than the TFC protrusion. However, it is found that the NFT protrusion is large enough to generate an air bearing push back effect, which changes the read and write spacing when the laser is powered on. To accurately control spacing in HAMR, this push back effect has to be taken into account.

Effects of Surface Roughness on the Fly-Ability of a Thermal Protrusion Air Bearing Slider

2009 ◽  
Author(s):  
Wei Hua ◽  
Bo Liu ◽  
Shengkai Yu ◽  
Weidong Zhou ◽  
Leonard Gonzaga
Keyword(s):  
Surface Roughness ◽  
Electrostatic Force ◽  
Flying Height ◽  
Total Force ◽  
Air Bearing ◽  
Intermolecular Force ◽  
Average Roughness ◽  
Thermal Protrusion ◽  
Bearing Force ◽  
Air Bearing Slider

A femto air bearing slider with thermal protrusion is studied based on three groups of surface roughness. It is observed that the air bearing force and the contact force are proportional to the value of average roughness in the minimum flying height region studied, while the intermolecular force or the electrostatic force is the smallest for the smoothest surfaces when the minimum flying height is above a certain value. As a result, the total force on the slider is the largest on the smoothest surfaces in a certain minimum flying height region. When the minimum flying height is designed in that region, the fly-ability of the slider is maximized.

Simulating the Air Bearing Flying Height in a Humid Environment

2007 ◽  
Author(s):  
Shuyu Zhang ◽  
Brian Strom ◽  
Sungchang Lee ◽  
George Tyndall
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Flying Height ◽  
Test Cases ◽  
Air Bearing ◽  
Humid Environment ◽  
Bearing Design ◽  
Flying Attitude ◽  
Saturation Vapor

For a hard disk drive operating in a humid environment, the water vapor in the slider’s air bearing is typically compressed beyond its saturation vapor pressure, causing the vapor to condense. Consequently, the air bearing pressure decreases and the slider’s flying attitude adjusts to balance the forces from the suspension. A method for calculating this air bearing response to humid air is presented. Using one particular air bearing design as an example, several test cases are analyzed to illustrate the air bearing response for various temperatures and humidity levels. The calculated flying heights agree with those measured in commercial hard disk drives.

Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part II — Dependence of the Stability on Hamaker Constant, Suspension Preload and Pitch Angle

2004 ◽  
Author(s):  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Pitch Angle ◽  
Dynamic Performance ◽  
Hard Disk Drives ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Air Bearing ◽  
Parametric Studies ◽  
The Stability ◽  
Hamaker Constants ◽  
Fly Height

Intermolecular and surface forces contribute significantly to the total forces acting on air bearing sliders for flying heights below 5nm. Their contributions to the total forces increase sharply with the reduction in flying height, and hence their existence can no longer be ignored in air bearing simulation for hard disk drives. Various experimentally observed dynamic instabilities can be explained by the inclusion of these forces in the model for low flying sliders. In this paper parametric studies are presented using a 3-DOF model to better understand the effect of the Hamaker constants, suspension pre load and pitch angle on the dynamic stability/instability of the sliders. A stiffness matrix is used to characterize the stability in the vertical, pitch and roll directions. The fly height diagrams are used to examine the multiple equilibriums that exist for low flying heights. It has been found that the system instability increases as the magnitude of the van der Waals force increases. It has also been found that higher suspension pre load and higher pitch angles tend to stabilize the system.

Loading Velocity Effect in the Load/Unload Systems With Multiple Flying Height States

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Polina V. Khan ◽  
Pyung Hwang
Keyword(s):  
Dynamic Loading ◽  
Continuation Method ◽  
Leading Edge ◽  
Disk Drive ◽  
Numerical Continuation ◽  
Flying Height ◽  
Disk Contact ◽  
Air Lubrication ◽  
Velocity Effect ◽  
In The Beginning

The effect of the loading velocity on the loading process in the computer hard disk drive air slider system with multiple flying height states was studied numerically. The results of the static analysis were compared with the dynamic loading trajectories. The air lubrication problem was solved using the finite-element method. The static flying height states for variable suspension forces were considered as solution branches and were found by using a numerical continuation method. The dynamic loading trajectory was obtained iteratively by applying the Newmark method for the slider position and an implicit scheme for the air film pressure. Close agreement was found between the solution branches and the trajectories of dynamic loading with a velocity of 5 mm/s. At the higher velocities, the unstable negative pitching motion and the slider-disk contact at the slider’s leading edge were detected. Increasing the x-offset of the suspension point made it possible to complete loading with 10 mm/s. At the same time, increasing the x-offset led to the slider-disk contact at the slider’s trailing edge in the beginning of loading with a velocity exceeding 25 mm/s.

Analysis of Thermal Flying-Height Control System About Humid Air Condition in Hard Disk Drive

2014 ◽  
Author(s):  
Jonghak Choi ◽  
No-Cheol Park ◽  
Young-Pil Park ◽  
Kyoung-Su Park ◽  
Eo-Jin Hong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Disk Drive ◽  
Flying Height ◽  
Air Bearing ◽  
Saturation Vapor Pressure ◽  
Humid Air ◽  
Height Control ◽  
Flying Attitude ◽  
Saturation Vapor

This research investigates to analyze the effect of humid air on TFC system. Required parameters of humid air and flying attitude of slider are calculated. Condensation of air bearing at over the saturation vapor pressure is considered. Heat transfer coefficient for humid air condition is calculated. TFC simulation about humid air is conducted.

Flying Height Modulation Due to Disk Waviness of Sub-5 nm Flying Height Air Bearing Sliders

2002 ◽  
Vol 124 (4) ◽  
pp. 762-770 ◽  
Author(s):  
Brian H. Thornton ◽  
A. Nayak ◽  
D. B. Bogy
Keyword(s):  
Disk Drive ◽  
Flying Height ◽  
Mode Shapes ◽  
Air Bearing ◽  
Bearing Surface ◽  
Dynamic Effects ◽  
Complex Phase ◽  
Edge Response ◽  
Percent Decrease ◽  
Geometric Effects

Two new air bearing slider designs are presented for storage densities greater than 100 Gb/in2 in hard disk drive (HDD) applications. Their dynamic frequencies and mode shapes are characterized, and they are used to study the flying height modulation (FHM) over wavy disks due to geometric effects as opposed to dynamic effects. It is found that low pitch designs experience large FHM at wavelengths on the order of the length of the sliders to one-eighth the length of the sliders due to a complex phase shift in the sliders trailing edge response as compared to the disk waviness. FHM due to disk waviness wavelengths from 2 mm to 0.16 mm was found to be a function of the sliders’ attitude (pitch angle) and the air bearing surface (ABS) geometry (pressure distribution over the ABS). The results presented suggest that the pitch should be greater than 100 μrad for the ABS designs presented and attention needs to be focused on the ABS design and disk morphology to avoid unacceptable FHM. An ABS design was introduced to reiterate the findings on geometric FHM showing an 83 percent decrease in geometric FHM. The FHM due to geometric effects of the slider designs studied in this paper could possibly be predicted by the disk morphology alone.

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