Design and Evaluation of Damped Air Bearings at Head-Disk Interface

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu ◽  
Yuki Shimizu ◽  
Masayuki Honchi ◽  
Kyosuke Ono ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Length Distribution ◽  
Low Frequency ◽  
Air Bearing ◽  
Modal Shape ◽  
Disk Interface ◽  
Stiffness Reduction ◽  
Parametric Studies ◽  
Bearing Stiffness ◽  
Pitch Mode

Perturbation and modal-analysis methods were employed to systematically study a damped slider’s dynamic characteristics, including an air-bearing slider’s stiffness, damping coefficient, frequency response to translation and wavy motion, natural frequencies, damping ratios, and modal shape-node line. We found that a design with grooves distributed on a trailing pad effectively improved the slider’s damping ratio in the second pitch mode; however, parametric studies revealed that the damping ratio was dependent on the number of grooves, their depth, location, width, length, distribution, orientation, and types. A higher damping ratio could be obtained by optimizing these parameters. The femto slider we designed with distributed damped grooves on a trailing pad had a higher damping ratio in the second pitch mode, and hence, its responses in the second pitch mode were greatly reduced, which were clarified through simulation and an experiment. Some issues on air-bearing stiffness reduction and negative damping at low frequency and contamination and lube pickup on the damped grooves were also evaluated in the experiment. No degradation could be found in the damped slider.

Stability and Dynamics of Non-Linear Slider Behaviour Due to Disk Waviness in the Presence of Intermolecular and Electrostatic Forces

2005 ◽  
Author(s):  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Resonance Frequency ◽  
Equations Of Motion ◽  
Disk Surface ◽  
Air Bearing ◽  
Electrostatic Forces ◽  
Disk Interface ◽  
Non Linear ◽  
Bearing Stiffness ◽  
Stiffness And Damping ◽  
Nonlinear Nature

In this paper we present a theoretical investigation of the stability and the dynamics of the non-linear behavior of a slider at very low head media spacing. A single DOF head disk interface (HDI) model, with constant air bearing stiffness and damping has been used to study the effect of disk waviness on the nonlinear slider dynamics in the presence of intermolecular and electrostatic forces. A variational approach based on the principle of least action was used to derive the equations of motion of the slider. Further, a stability criteria was derived that helped to better understand the instabilities that appear in slider when the slider is flying in close proximity to the disk surface. Due to extremely nonlinear nature of the interaction between the slider and the disk, we observed some strange features of the motion of the slider. In particular the effects of the nonlinear interaction force, air bearing stiffness and damping on the instabilities of the periodic motions of the slider are discussed in detail. We found that the branch associated to the disk waviness frequencies larger than the resonance frequency is always stable and the branch associated to the disk waviness frequencies smaller than the resonance frequency exhibits two stable domains and one unstable domain. This analysis was further extended to include the nonlinear nature of air bearing stiffness and damping as well as contact at the HDI.

Numerical Analysis of Microwaviness-Excited Vibrations of a Flying Head Slider at Touchdown

2017 ◽  
Author(s):  
Kyosuke Ono
Keyword(s):  
Adhesion Force ◽  
Hard Disk Drives ◽  
Force Model ◽  
Air Bearing ◽  
Single Degree Of Freedom ◽  
Disk Interface ◽  
Head Slider ◽  
Bearing Stiffness ◽  
Bearing Force ◽  
Parameter Values

As an extension of the study presented in ISPS 2016, vibration characteristics of a commercially used head slider in hard disk drives at touchdown are analyzed by using a single degree-of-freedom (DOF) slider model, improved asperity adhesion force model, and air-bearing force model. Using parameter values at the head/disk interface, the total interfacial force was evaluated for various air bearing stiffness ratios r. Microwaviness (MW)-excited slider vibration was simulated near the boundary of instability onset (r = 2.4), and slight instability conditions at r = 2. It was found that the simulated results at r = 2.4 and 2 agree well with the touchdown vibrations of actual slider at ID and MD, respectively. The possibility of surfing recording is discussed.

Design of Damped Air Bearings at Head Disk Interface

2009 ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu ◽  
Yuki Shimizu ◽  
Masayuki Honchi ◽  
Kyosuke Ono
Keyword(s):  
Modal Analysis ◽  
Small Perturbation ◽  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Length Distribution ◽  
Effective Solution ◽  
Air Bearings ◽  
Head Disk Interface ◽  
Disk Interface ◽  
The Third

Small perturbation and modal-analysis methods were employed to systematically study a damped slider’s dynamic characteristics. We found that a design with grooves distributed on a trailing pad effectively improved the slider’s damping at higher frequencies, and the damping ratio was dependent on the number of grooves, their depth, location, width, length, distribution, orientation, and types. A higher damping ratio could be obtained by optimizing these parameters. The femto slider with distributed damping grooves on a trailing pad had a higher damping ratio in the third mode, and hence, its responses to disk parallel and wavy motion were greatly reduced. This new design for the damped slider was an effective solution reducing the slider’s modulation.

Dynamic Stability and Spacing Modulation of Sub-25 nm Fly Height Sliders

1997 ◽  
Vol 119 (4) ◽  
pp. 646-652 ◽  
Author(s):  
Yong Hu ◽  
David B. Bogy
Keyword(s):  
Dynamic Stability ◽  
Hard Disk Drives ◽  
Dynamics Simulation ◽  
Inertia Force ◽  
Roll Motion ◽  
Air Bearing ◽  
Skew Angle ◽  
Disk Interface ◽  
Bearing Stiffness ◽  
Fly Height

Designing a reliable sub-25 nm spacing head/disk interface for today’s magnetic hard disk drives demands a greater dynamic stability and a smaller spacing modulation. An air bearing dynamic simulator with multiple features is developed to investigate the dynamic characteristics of three shaped-rail negative pressure sub-25 nm fly height sliders. Various simulations including air bearing stiffness, impulse response, surface roughness induced spacing modulation, bump response, and track seeking dynamics are performed. The results indicate that the roughness induced spacing modulation decreases with the increase of the air bearing stiffness and the decrease of the slider size. The suspension dynamics is integrated into the air bearing dynamics simulation for the track accessing motion by modal analysis. It is concluded that the fly height modulation during a track accessing event is attributed to many factors such as the effective skew angle, the seeking velocity, and the roll motion caused by the inertia of the moving head. The extent of the roll motion effect depends on the air bearing roll stiffness and the level of the inertia force of the moving head. Larger roll stiffness and smaller inertia force produce a smoother track accessing performance.

Effects of Air Bearing Stiffness on a Hard Disk Drive Subject to Shock and Vibration

2003 ◽  
Vol 125 (2) ◽  
pp. 343-349 ◽  
Author(s):  
Eric M. Jayson ◽  
J. Murphy ◽  
P. W. Smith ◽  
Frank E. Talke
Keyword(s):  
Finite Element ◽  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Element Model ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Wide Range ◽  
Bearing Stiffness

A finite element model of a hard disk drive (HDD) is developed to investigate the transient response of an operational HDD subject to shock and vibration. The air bearing stiffness of the head disk interface is determined from a finite element solution of the Reynolds equation and approximated with linear springs. The structural response is analyzed for several types of sliders with a wide range of air bearing stiffness. Results show the response of the head-disk interface subject to shock and the modes excited by vertical and lateral vibrations of the HDD.

Analysis of Bouncing Vibrations of a 2-DOF Model of Tripad Contact Slider Over a Random Wavy Disk Surface

2000 ◽  
Vol 123 (1) ◽  
pp. 159-167 ◽  
Author(s):  
Kohei Iida ◽  
Kyosuke Ono
Keyword(s):  
Contact Stiffness ◽  
Damping Ratio ◽  
Disk Surface ◽  
Design Parameters ◽  
Air Bearing ◽  
Continuous Contact ◽  
Design Concepts ◽  
The Coefficient Of Friction ◽  
Bearing Stiffness ◽  
Contact Slider

We numerically analyzed the bouncing vibrations of a two-degree-of-freedom (2-DOF) model of a tri-pad contact slider with air bearing pads over a random wavy surface and manifested the design conditions of a contact slider. The effects of the design parameters such as air bearing stiffness, contact damping ratio, the coefficient of friction, and the characteristics of the disk surface waviness on dynamic behavior and the contact sliding ability of the slider have been investigated. As a result, we found that friction force decreases the contact sliding ability at the boundary of the intermittent and continuous contact sliding. We also found that the distance between the rear air bearing center and the contact pad has a significant effect on the contact sliding ability. If the contact pad is apart from the rear air bearing center, the contact pad tends to separate from the disk. Based on this analytical study, we have proposed two design concepts: (1) Make the distance between the rear air bearing center and the contact pad as small as possible; in this case, the larger the rear air bearing stiffness results are, the better the contact ability is; (2) If some distance between the rear air bearing center and the contact pad is inevitable, then make the rear air bearing stiffness much smaller than the contact stiffness.

Analysis of Bouncing Vibrations of a 2-DOF Tripad Contact Slider Model With Air Bearing Pads Over a Harmonic Wavy Disk Surface

1999 ◽  
Vol 121 (4) ◽  
pp. 939-947 ◽  
Author(s):  
Kyosuke Ono ◽  
Kan Takahashi
Keyword(s):  
Contact Stiffness ◽  
Disk Surface ◽  
Design Parameters ◽  
Air Bearing ◽  
Static Contact ◽  
Tracking Ability ◽  
The Coefficient Of Friction ◽  
Bearing Stiffness ◽  
Perfect Contact ◽  
Contact Slider

In this study, the authors numerically analyzed the bouncing vibrations of a two-degree-of-freedom (2-DOF) model of a tripad contact slider with air bearing pads over a harmonic wavy disk surface. The general features of bouncing vibrations were elucidated in regard to the modal characteristics of a 2-DOF vibration system and design parameters such as contact stiffness, contact damping, air hearing stiffness, the rear to front air bearing stiffness ratio, static contact force and the coefficient of friction. The design of a contact slider was discussed in terms of tracking ability and wear durability. In addition, two sample designs of a perfect contact slider with sufficient wear durability were also presented.

Air-Bearing Design Towards Super Stable Head-Disk Interface

2006 ◽  
Author(s):  
Bo Liu ◽  
MingSheng Zhang ◽  
Yijun Man ◽  
Shengkai Yu ◽  
Gonzaga Leonard ◽  
...  
Keyword(s):  
Air Bearing ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Bearing Design

Numerical Investigation of Bouncing Vibrations of a Partial Contact Slider

2007 ◽  
Author(s):  
Du Chen ◽  
David D. Bogy
Keyword(s):  
Hard Disk Drives ◽  
Disk Surface ◽  
Air Bearing ◽  
Nonlinear Dynamic Model ◽  
Frequency Spectra ◽  
Disk Interface ◽  
Partial Contact ◽  
Adhesion Contact ◽  
Contact Situation ◽  
Contact Slider

A nonlinear dynamic model is developed to analyze the bouncing vibration of a partial contact air bearing slider, which is designed for the areal recording density in hard disk drives of 1 Tbit/in2 or even higher. In this model the air bearing with contact is modeled using the generalized Reynolds equation modified with the Fukui-Kaneko slip correction and a new second order slip correction for the contact situation [1]. The adhesion, contact and friction between the slider and the disk are also considered in the model. It is found that the disk surface roughness, which moves into the head disk interface (HDI) as the disk rotates, excites the bouncing vibrations of the partial contact slider. The frequency spectra of the slider’s bouncing vibration have high frequency components that correspond to the slider-disk contact.

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