Experimental and Analytical Study of Bouncing Vibrations of a Flying Head Slider in a Near-Contact Regime

2005 ◽  
Vol 127 (2) ◽  
pp. 376-386 ◽  
Author(s):  
Kyosuke Ono ◽  
Masami Yamane ◽  
Hiroshi Yamaura
Keyword(s):  
Degrees Of Freedom ◽  
Analytical Study ◽  
Adhesion Force ◽  
Ambient Pressure ◽  
Frictional Coefficient ◽  
Flying Height ◽  
Air Bearing ◽  
Height Range ◽  
Head Slider ◽  
Rough Surface Contact

This paper presents an experimental and analytical study of bouncing vibrations of a flying head slider in near-contact and contact regimes. In our experiment we showed that, by reducing the ambient pressure, the slider begins to touch-down and exhibit bouncing vibrations, and by increasing the ambient pressure thereafter, the slider continues to vibrate until an ambient pressure higher than the touch-down pressure. In the analysis we used a two-degrees-of-freedom slider model with linear front and rear air-bearing springs and dashpots. In a numerical simulation of slider dynamics, we considered rough surface contact of the trailing air-bearing pad with a disk, including bulk deformation, adhesion force of lubricant and friction force. The disk is assumed to have no microwaviness. From the simulation of decreasing and increasing nominal flying height, we found that the slider exhibits a bouncing vibration and touch-down/take-off hysteresis as seen in the experiment. The frequency spectrum characteristics of the bouncing vibration agree well between numerical analysis and the experiment. From a parametric study of the bouncing vibration excited by initial spacing deviation, we found that the unstable flying height range can be decreased by increasing the air-bearing stiffness and can be completely eliminated if the lubricant adhesion force or the frictional coefficient is decreased to certain small values.

Improved Analysis of Unstable Bouncing Vibration and Stabilizing Design of Flying Slider in Near-Contact Regime

2005 ◽  
Author(s):  
Kyosuke Ono ◽  
Masami Yamane
Keyword(s):  
Parametric Study ◽  
Adhesion Force ◽  
Design Method ◽  
Contact Stiffness ◽  
Frictional Coefficient ◽  
Disk Surface ◽  
The Self ◽  
Air Bearing ◽  
Excited Vibration ◽  
Bearing Stiffness

We proposed a design method of a flying head slider that can suppress the bouncing vibration in a near-contact regime, based on parametric study using an improved slider and contact models. At first, we numerically calculated the characteristics of contact force and adhesive force between air bearing pad and disk surface under the current small roughness conditions and found that the contact characteristics can be modeled by constant contact stiffness, a constant adhesion force and the separations of beginning and end of contact. Next we numerically computed the slider dynamics of a 2-DOF slider model by using these contact characteristics and nonlinear air-bearing stiffness. As a result, we could get the self-excited bouncing vibration whose general characteristics are more similar to the experimented results compared to our previous study. Parametric study shows that the frictional coefficient, attractive force and contact stiffness should be decreased and front and rear air-bearing stiffness and ratio of rear to front air-bearing stiffness should be increased in order to realize a stable flying slider in a smallest possible spacing. Moreover, we elucidated the effect of micro-waviness on the self-excited vibration of the slider.

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.

Experimental and Theoretical Investigation of Bouncing Vibrations of a Flying Head Slider in the Near-Contact Region

2006 ◽  
Vol 129 (2) ◽  
pp. 246-255 ◽  
Author(s):  
Kyosuke Ono ◽  
Masami Yamane
Keyword(s):  
Vibration Amplitude ◽  
Contact Region ◽  
Ambient Pressure ◽  
Disk Surface ◽  
Flying Height ◽  
Trailing Edge ◽  
Detailed Measurement ◽  
Head Slider ◽  
Pitch Frequency ◽  
Two Degree Of Freedom

We experimentally and theoretically investigated in detail bouncing vibrations of a flying head slider in the near-contact region between the head and disk surface. By changing the Z-height in the experiment, we evaluated the effect of the pitch static angle on the ambient pressure at which unstable bouncing vibration starts and stops. We found that the touch-down and take-off pressure hysteresis decreased as the pitch static angle increased even though the flying height at the trailing edge decreased slightly. From detailed measurement of the slider dynamics at the threshold of the bouncing vibration, we found that the trailing edge of the slider was first attracted to the disk. As the pitch static angle decreased, the magnitude of the first drop of the trailing edge increased and the bouncing vibration amplitude increased more rapidly. We also measured the mode of the bouncing vibration by using two laser Doppler vibrometers simultaneously. By using an improved two-degree-of-freedom slider model, in which the small micro-waviness and the shearing force of the lubricant were taken into account, we could analyze the touch-down/take-off hysteresis, mode, and destabilization process of the bouncing vibration similar to the experimental results. We also theoretically found that either self-excited bouncing vibration with lower pitch frequency or forced vibration with higher pitch frequency was generated, depending on the magnitudes of the micro-waviness and the disturbance.

The Double Dimple Magnetic Recording Head Suspension and Its Effect on Fly Height Variability

1995 ◽  
Vol 117 (2) ◽  
pp. 267-271
Author(s):  
J. C. Harrison ◽  
K. P. Hanrahan
Keyword(s):  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Flying Height ◽  
Air Bearing ◽  
Bearing Surface ◽  
Percent Reduction ◽  
Recording Head ◽  
Head Gimbal Assembly ◽  
Magnetic Recording Head ◽  
Fly Height

A gimbal forming modificaton is presented which, when implemented, leads to significant reduction in air bearing surface (ABS) static attitude and flying height variability within head-gimbal assembly (HGA) populations. The modification requires no additional parts or steps in the manufacture of the suspension assembly. An experimental test of the concept is described, along with the procedure on which it is based. The resulting reduction in product variability is obtained without measurement of (or tailoring to) the initial conditions of the constitutive parts of each HGA. A ≈ 50 percent reduction in static attitude variability, and a ≈ 33 percent reduction in flying variability, was experimentally shown to result from the adoption of the Double Dimple design concept, in all flying degrees of freedom.

3403 Surface Potential on Air Bearing of Magnetic Head Slider with Thermal Actuator for Flying Height Control

2007 ◽  
Vol 2007.5 (0) ◽  
pp. 317-318
Author(s):  
Masayuki KURITA ◽  
Toshiya SHIRAMATSU ◽  
Koji MIYAKE ◽  
Atsushi KATO ◽  
Mike SUK ◽  
...  
Keyword(s):  
Surface Potential ◽  
Thermal Actuator ◽  
Flying Height ◽  
Air Bearing ◽  
Magnetic Head ◽  
Height Control ◽  
Head Slider

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.

Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part I—Effect of Initial Excitations and Slider Form Factor on the Stability

2005 ◽  
Vol 128 (1) ◽  
pp. 197-202 ◽  
Author(s):  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Dynamic Instability ◽  
Dynamic Performance ◽  
Areal Density ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Air Bearing ◽  
Height Range ◽  
Dynamic Simulator ◽  
The Stability ◽  
Fly Height

The mechanical spacing between the slider and the disk has to be reduced to less than 5 nm in order to achieve an areal density of 1Tbit∕in2. Certain physical phenomena, such as those that can be caused by intermolecular and surface forces, which do not have a significant effect at higher flying heights, become more important at such low head-media separations. These forces are attractive for head-media separation as low as 0.5 nm, which causes a reduction in the mechanical spacing as compared to what would be the case without them. Single degree of freedom models have been used in the past to model these forces, and these models have predicted unstable flying in the sub-5-nm flying height range. Changes in the pitch and the roll angles were not accounted for in such models. A 3-DOF air bearing dynamic simulator model is used in this study to investigate the effect of the intermolecular forces on the static and dynamic performance of the air bearing sliders. It is seen that the intermolecular forces increase the level of flying height modulations at low flying heights, which in turn results in dynamic instability of the system similar to what has also been observed in experiments. The effect of initial vertical, pitch, and roll excitations on the static and dynamic flying characteristics of the slider in the presence of the intermolecular forces has also been investigated. A stiffness matrix is defined 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. Finally, a study was carried out to compare the performance of pico and femto designs based on the hysteresis observed during the touchdown-takeoff simulations.

Study of Contact Bouncing Vibration of Flying Head Slider in Near-Contact Regime

2005 ◽  
Author(s):  
Masami Yamane ◽  
Kyosuke Ono
Keyword(s):  
Pitch Angle ◽  
Degrees Of Freedom ◽  
Air Bearing ◽  
Coupled Vibration ◽  
3 Dimensional ◽  
Head Slider ◽  
Strong Shear ◽  
Small Phase ◽  
Bearing Stiffness ◽  
Slider Motion

We experimentally and analytically investigated detailed characteristics of the bouncing vibrations of a flying head slider in a near-contact regime. In the experiment, we found that the hysteresis of touch-down and take-off pressure and the rate of instability become small as the pitch angle increases. Moreover, we measured the 3-dimensional slider motion by using two laser Doppler vibrometers simultaneously and found that the bouncing vibration is a coupled vibration between translation and pitch with a small phase shift. These experimental features can be explained analytically if we consider strong shear force due to lubricant and small amount of microwaviness for the previous two-degrees of freedom slider model with nonlinear air bearing stiffness.

Performance of Sliders Flying Over Discrete-Track Media

2007 ◽  
Vol 129 (4) ◽  
pp. 712-719 ◽  
Author(s):  
Jianhua Li ◽  
Junguo Xu ◽  
Yuki Shimizu
Keyword(s):  
Estimation Method ◽  
Simulation Method ◽  
Measured Data ◽  
Flying Height ◽  
Height Loss ◽  
Air Bearing ◽  
Slider Air Bearing ◽  
Discrete Track ◽  
Flying Attitude ◽  
Manufacturing Variation

A simulation method in which grooves are virtually distributed on the slider air bearing instead of on the grooved medium surface has been developed and used to investigate the performance of sliders flying over the surface of a discrete-track medium. The simulated flying height loss due to a discrete-track medium coincides well with the measured data, whereas the average-estimation method overestimates flying height loss. Among the characteristics of a slider flying over the surface of a discrete-track medium that were studied are the flying attitude, the effect of groove parameters on flying profile, and the flying height losses due to manufacturing variation and altitude. The results indicate that when a slider is flying over the surface of a discrete-track medium, it will have a higher 3σ of flying height, be more sensitive to altitude, and will have a greater flying height loss.

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.

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