An Insight Into the Nonlinear Touchdown Dynamics of TFC Active Slider

2013 ◽  
Author(s):  
Gang (Sheng) Chen ◽  
Jianfeng Xu ◽  
J.-Y. Chang
Keyword(s):  
Nonlinear Dynamics ◽  
Hard Disk Drives ◽  
Disk Surface ◽  
Flying Height ◽  
Disk Drives ◽  
Height Control ◽  
Intermittent Contact ◽  
Fly Height ◽  
Insight Into ◽  
Small Spacing

Storage of 10 Tb/in 2 in hard disk drives within the next decade requires a significant change to reduce the physical spacing as little as 0.25 nm at the read-write transducer location. A lot of tribology issues exist to such a low flying height, the touch down and take off instability and hysteresis, the flying height avalanche, the influences of surface topography and morphology, the lubricant modulation and pick-up, robust air bearing surface and suspension design, just to name a few. Understandings of the complex tribo-dynamics issues in the near contact and contact states are very important to further reduce the flying height. At such a small spacing intermittent contact between the slider and disk surface becomes inevitable and the current MEMS-based thermal fly-height control (TFC) technology needs further improvement to satisfy the future needs. How to control the slider to reduce touchdown instability and eventually eliminate bouncing has been a pressing and challenging research topic. Most of existing work on touchdown dynamics applied conventional nonlinear dynamics theory and spectrum as well as harmonics analysis, which could suffer from the assumptions of small nonlinearity and stationary. This study presents a concurrence plot and Lyapunov exponent analysis which could offer an insight to the problem in the context of contemporary nonlinear dynamics theory.

Nano Wear of Thermal Flying Height Control Sliders

2014 ◽  
Author(s):  
Andreas Hegetschweiler ◽  
Liane Matthes ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drives ◽  
Disk Surface ◽  
Flying Height ◽  
Disk Drives ◽  
Heater Power ◽  
Heater Element ◽  
Height Control ◽  
Thermal Flying Height Control ◽  
Intermittent Contact ◽  
Peak Value

To increase the storage density in hard disk drives (HDDs), the clearance between the read/write head and the disk has to be reduced. In current HDDs, the flying height of the slider is about 1–2 nm, which is on the same order as the peak to peak value of the disk surface roughness. As a consequence, intermittent contact between the slider and the disk might occur. Intermittent head-disk contacts are undesirable since they can result in wear of the slider or lubricant transfer [1]–[5]. To achieve flying-heights of 1–2 nm, thermal flying height control (TFC) sliders have been introduced in HDDs [6]. TFC sliders contain a small heater element close to the read and write element. Energizing the heater element results in thermal expansion of the slider body and a thermal protrusion is formed. An increase in heater power increases this protrusion, thereby bringing the read and write element closer to the disk (Fig. 1).

Contact and temperature rise of thermal flying height control sliders in hard disk drives

2012 ◽  
Vol 18 (9-10) ◽  
pp. 1693-1701 ◽  
Author(s):  
Liane Matthes ◽  
Uwe Boettcher ◽  
Bernhard Knigge ◽  
Raymond de Callafon ◽  
Frank E. Talke
Keyword(s):  
Temperature Rise ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Flying Height ◽  
Disk Drives ◽  
Height Control ◽  
Thermal Flying Height Control

scholarly journals Servo signal processing for flying height control in hard disk drives

2011 ◽  
Vol 17 (5-7) ◽  
pp. 937-944 ◽  
Author(s):  
Uwe Boettcher ◽  
Christopher A. Lacey ◽  
Hui Li ◽  
Kensuke Amemiya ◽  
Raymond A. de Callafon ◽  
...  
Keyword(s):  
Signal Processing ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Flying Height ◽  
Disk Drives ◽  
Height Control ◽  
Servo Signal

Thermal Fly-Height Controlled Glide for Disk Defect Detection and In-Situ Defect Size Estimation for Disk Drives

2013 ◽  
Author(s):  
Aravind N. Murthy ◽  
Karl A. Flechsig ◽  
Wes Hillman ◽  
Keith Conard ◽  
Remmelt Pit
Keyword(s):  
Hard Disk Drives ◽  
Sem Analysis ◽  
Disk Drives ◽  
Size Estimation ◽  
Optical Surface ◽  
Force Microscopy ◽  
Height Control ◽  
Atomic Force ◽  
Fly Height

Current hard disk drives (HDD’s) use thermal fly-height control (TFC) during read/write operations. In this study, we use TFC technology during the disk glide process to determine sub-5nm height defects. We also utilize TFC to measure the height of the defect during glide operation. Addtionally, we magnetically mark the disk locations where defects are detected for further post-processing of the defects using optical surface analysis (OSA), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The defect height estimation during the glide was confirmed to be accurate by AFM and SEM analysis. Finally, we will present the TFC glide sensitivity showing capability of detecting smaller defects than conventional non-TFC glide technologies.

Investigation of Head Burnishing of Thermal Flying Height Control Sliders

2013 ◽  
Author(s):  
Liane Matthes ◽  
Ralf Brunner ◽  
Bernhard Knigge ◽  
Frank E. Talke
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Flying Height ◽  
Disk Drives ◽  
Lubricant Transfer ◽  
Height Control ◽  
Thermal Flying Height Control ◽  
Disk Spacing

The head-disk spacing in current hard disk drives is approximately 1–2 nm. This distance is on the same order as the peak to valley surface roughness of a typical thin film disk. If one attempts to reduce the head-disk spacing even more, intermittent contacts between the slider and the disk are more likely to occur. Intermittent contacts are undesirable since they can result in slider and disk wear, lubricant transfer or degradation of the read and write elements.

The Simulation of Laser Cleaning of Magnetic Head with Different Temporal Pulses

2015 ◽  
Vol 1101 ◽  
pp. 446-452 ◽  
Author(s):  
Narongpun Rungcharoen ◽  
Mongkol Wannapapra ◽  
Wanchai Pijitrojana
Keyword(s):  
Hard Disk Drives ◽  
Disk Surface ◽  
Laser Cleaning ◽  
User Requirements ◽  
Particle Removal ◽  
Disk Drives ◽  
Magnetic Head ◽  
Small Particles ◽  
Fly Height ◽  
Non Destructive

Nowadays, hard disk drives (HDD) technology are being developed continuously in order to increase the capacity, and reduce the size of HDD to meet user requirements. To increase the capacity which is equivalent to increasing read/write ability, the flying clearance must be reduced. Current new HDD models show that the fly height is lower than 0.3 μm. If the height of a particle or contamination is higher than 0.3 μm, the magnetic head will scratch the magnetic disk surface. However the process of cleaning in the HDD industry cannot remove particles with size smaller than 0.3 μm [1]. Therefore laser cleaning is selected first because this method can remove small particles [2]. and it does not damage the magnetic head. This research compares the range of temperature needed for cleaning the magnetic head between two types of heat source’s profile. The technique used is the heat transfer by finite element: FEM[3]. This technique provides an important factor of the laser cleaning method that increases the efficiency of particle removal. It is also a non-destructive method for cleaning the surface of the magnetic head slider.

Flying Clearance Distribution With Thermal Flying Height Control in Hard Disk Drives

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Sung-Chang Lee ◽  
George W. Tyndall ◽  
Mike Suk
Keyword(s):  
Temperature Compensation ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Flying Height ◽  
Disk Drives ◽  
Disk Interface ◽  
Height Control ◽  
Thermal Flying Height Control ◽  
Height Change ◽  
The Individual

Flying clearance distribution with thermal flying height control (or thermomechanical actuation) is characterized. Especially, factors contributing to variation in the flying clearance are identified based on the flying height change profiles taken from the burn-in process of hard disk drives and Gage R&R (repeatability and reproducibility) test of touch down repeatability. In addition, the effect of static temperature compensation scheme on the flying clearance distribution is investigated, and the disadvantage of static adaptation to temperature change is identified. In order to avoid early catastrophic head-disk interface failures due to poor static temperature compensation, dynamic clearance adjustment is necessary whenever environmental condition changes. Otherwise, static temperature compensation using the individual temperature sensitivity values of each head needs to be applied.

Flying Height Control for a 2-DOF Tripad Slider in Hard Disk Drives With Switched Regulator

2005 ◽  
Author(s):  
Zhizheng Wu ◽  
Foued Ben Amara
Keyword(s):  
Control Method ◽  
Hard Disk Drives ◽  
Surface Profile ◽  
Hard Disk ◽  
Disk Surface ◽  
Switched System ◽  
Flying Height ◽  
Disk Drives ◽  
The Stability ◽  
Adaptive Regulator

Maintaining a constant small flying height of the read/write head is an important target in the design of the ultra high storage density hard disk drives. One effective way to achieve this goal is to use a feedback regulator to suppress the flying height variations. For low flying heights, the read/write head enters into intermittent contact with the disk surface, which results in a switched system regulation problem. In this paper a new control method is proposed to maintain the flying height at its desired value based on the switched system models, despite the unknown microwaviness in the disk surface profile and the unpredictability in the switching times. First, a switched system model is constructed. Then, a Q parameterized set of switched regulators is constructed and the stability of the resulting switched closed loop system is analyzed. Online adaptive regulator tuning is then performed by adjusting the Q parameter in the controller to achieve regulation. Simulation results are presented to illustrate the effectiveness of the proposed method.

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