Optimizing Vibration Isolation of Flex Circuits in Hard Disk Drives

2004 ◽  
Vol 127 (2) ◽  
pp. 165-172 ◽  
Author(s):  
M. R. Brake ◽  
J. A. Wickert
Keyword(s):  
Vibration Isolation ◽  
Hard Disk Drives ◽  
Experimental Studies ◽  
Hard Disk ◽  
Disk Drive ◽  
Design Stage ◽  
Vibration Transmission ◽  
Write Heads ◽  
Vibration Coupling

A “flex circuit” is a laminate of polyimide substrate, adhesive, and copper conductors that is used to connect the stationary electronic components in a computer hard disk drive to the rotating arm that positions read/write heads above the disks. The flex circuit’s transverse and longitudinal vibrations couple with the arm, and those motions, although seemingly small, degrade performance during seek operations from one data track to another. The flex circuit and arm mechanism is defined by a number of geometric parameters, and some latitude is available at the design stage for choosing dimensions and angles so as to minimize vibration transmission from the flex circuit to the arm. In this paper, the results of parameter, optimization, and experimental studies are discussed with a view toward improving isolation of the arm from vibration of the flex circuit in one or several modes. Particularly for the mechanism’s odd modes, the flex circuit’s free length and the relative attachment angle between the arm’s centerline and the circuit can each be chosen to significantly reduce vibration transmission. A genetic algorithm was applied to minimize a metric of vibration coupling in several vibration modes, and, in the case study examined, vibration isolation was improved by over 80%.

Optimizing Vibration Isolation of Flex Circuits in Hard Disk Drives

2003 ◽  
Author(s):  
M. Brake ◽  
J. A. Wickert
Keyword(s):  
Vibration Isolation ◽  
Longitudinal Vibration ◽  
Hard Disk Drives ◽  
Experimental Studies ◽  
Hard Disk ◽  
Disk Drive ◽  
Vibration Modes ◽  
Disk Drives ◽  
Electronic Components ◽  
Write Heads

Flex circuits are a laminate of polyimide substrate, adhesive, and copper conductors, and they are used to connect the (stationary) electronic components in a hard disk drive to the (rotating) arm that positions the read/write heads above the disk. The transverse and longitudinal vibration of flex circuits couples with motion of the read/write heads and contributes to increased settling time and residual vibration following repositioning of the arm from one data track to another. In this paper, the results of parameter, optimization, and experimental studies are discussed with a view toward increasing the isolation of vibration between the flex circuit to the arm in terms of a metric involving one or several important vibration modes.

Pressure Fluctuations and Flow-Induced Vibration Measurements in a Hard Disk Drive under Different Rotation Speeds

2012 ◽  
Vol 197 ◽  
pp. 292-296 ◽  
Author(s):  
He Qun Min ◽  
Xiao Yang Huang ◽  
Qi De Zhang
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Hard Disk Drives ◽  
Experimental Studies ◽  
Laser Doppler Vibrometer ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Drives ◽  
Flow Induced Vibration ◽  
Causal Nexus

Flow-induced vibration (FIV) of a head gimbals assembly (HGA) in hard disk drives (HDDs) limits the positioning accuracy of magnetic head in the HGA for higher HDD magnetic recording density. The pressure fluctuations characterize turbulent fluctuations exciting the HGA off-track vibration (HGA-OTV). In this paper, experimental studies have been carried out to investigate the spectrum characteristics correspondence between pressure fluctuations around an HGA and the simultaneous HGA-OTV under different HDD rotation speeds. A practical and effective experimental setup has been implemented to enable the simultaneous measurements on both the pressure fluctuation and HGA-OTV signals, where pressure fluctuations are measured with a pressure transducer through a small hole on the HDD top cover and the direct HGA-OTV signals are detected through a laser Doppler vibrometer. Results under conditions of three different HDD rotation speeds of 7200, 9000, 10800 rpm have been investigated and compared. It is shown that the HGA off-track vibration spectra are highly associated with those of the pressure fluctuations in terms of principal peaks in four frequency bands around 1.8 kHz, 2.5-3.5 kHz, 7-7.5 kHz and 11.5-12.5 kHz. With increasing HDD rotation speed, it is shown that the spectrum magnitudes of both the pressure fluctuation and the HGA off-track vibration increase correspondingly, while the principal peak positions in spectra of either pressure fluctuation or the HGA off-track vibration always hold the line. This study demonstrates a causal nexus from the pressure fluctuation to the HGA off-track vibration and suggests the feasibility of controlling the HGA-OTV through suppression of pressure fluctuations around the HGA.

scholarly journals Design and Analysis of Shock and Random Vibration Isolation of Operating Hard Disk Drive in Harsh Environment

2009 ◽  
Vol 16 (2) ◽  
pp. 143-154 ◽  
Author(s):  
Hendri Harmoko ◽  
Fook Fah Yap ◽  
Nader Vahdati ◽  
Chuan Li
Keyword(s):  
Random Vibration ◽  
Vibration Isolation ◽  
Hard Disk Drives ◽  
Evaluation Criteria ◽  
Hard Disk ◽  
Disk Drive ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Severe Shock ◽  
Isolation Systems

An effective vibration isolation system is important for hard disk drives (HDD) used in a harsh mechanical environment. This paper describes how to design, simulate, test and evaluate vibration isolation systems for operating HDD subjected to severe shock and random vibrations based on military specifications MIL-STD-810E. The well-defined evaluation criteria proposed in this paper can be used to effectively assess the performance of HDD vibration isolation system. Design concepts on how to achieve satisfactory shock and vibration isolation for HDD are described. The concepts are tested and further enhanced by the two design case studies presented here. It is shown that an effective vibration isolation system, that will allow a HDD to operate well when subjected to severe shock and random vibration, is feasible.

Superlubricity Relevant in Hard Disk Drive Applications

2016 ◽  
Author(s):  
Shou-Mo Zhang ◽  
Cuong-C. Vu ◽  
Qun-Yang Li ◽  
Norio Tagawa ◽  
Quan-Shui Zheng
Keyword(s):  
Temperature Dependence ◽  
Hard Disk Drive ◽  
Large Scale ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Force Sensor ◽  
Lubricant Layer ◽  
Single Crystalline ◽  
Crystalline Graphite

Reduction of head-media spacing (HMS) keeps crucial during the increase of areal density of hard disk drives (HDD). The design of hard disk drive with a superlubric interface is reported with two schemes for HDI design to realize superlubricity. For the first scheme, the DLC layer is kept on the disk while removing the lubricant layer. The DLC layer on the transducer is replaced by graphene-like layer. The direct contact between head and disk could reduce the HMS to about 2.3 nm. For the second scheme, the DLC layer on disk is further replaced by graphene and the HMS could be reduced to below 1 nm. For the first scheme, the basic proof of concept experiments are conducted using micro-scale graphite island samples. Ultralow COF, with the average of 0.0344 on the interface of single crystalline graphite surface and DLC substrate is demonstrated by AFM. What’s more, the temperature dependence of friction between single crystalline graphite and DLC is measured by micro-force sensor mounted on micro-manipulator. The results show that heating helps to significantly decrease the friction. Desorption of contaminants along the interface is speculated to be the key mechanism for temperature dependence of friction. This work provides the concept of large-scale superlubricity relevant in HDD applications, which could be a promising technology to ultimately reduce HMS for future HDI development.

scholarly journals Strain Sensing With Piezoelectric Zinc Oxide Thin Films for Vibration Suppression in Hard Disk Drives

2008 ◽  
Author(s):  
Sarah Felix ◽  
Stanley Kon ◽  
Jianbin Nie ◽  
Roberto Horowitz
Keyword(s):  
Vibration Suppression ◽  
Transfer Functions ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Strain Sensing ◽  
Linear Quadratic ◽  
H2 Control ◽  
Hard Drives ◽  
Optimization Methodology

This paper describes the integration of thin film ZnO strain sensors onto hard disk drive suspensions for improved vibration suppression for tracking control. Sensor location was designed using an efficient optimization methodology based on linear quadratic gaussian (LQG) control. Sensors were fabricated directly onto steel wafers that were subsequently made into instrumented suspensions. Prototype instrumented suspensions were installed into commercial hard drives and tested. For the first time, a sensing signal was successfully obtained while the suspension was flying on a disk as in normal drive operation. Preliminary models were identified from experimental transfer functions. Nominal H2 control simulations demonstrated improved vibration suppression as a result of both the better resolution and higher sensing rate provided by the sensors.

scholarly journals Data Sanitization Framework for Computer Hard Disk Drive: A Case Study in Malaysia

2019 ◽  
Vol 10 (11) ◽  
Author(s):  
Nooreen Ashilla Binti Yusof ◽  
Siti Norul ◽  
Mohamad Firham ◽  
Nor Zarina ◽  
Monaliza Binti
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Data Sanitization

scholarly journals Design and Implementation of Dual-Stage Track-Following Control for Hard Disk Drives

2009 ◽  
Author(s):  
Jianbin Nie ◽  
Roberto Horowitz
Keyword(s):  
Hard Disk Drives ◽  
Servo System ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Drives ◽  
Outer Loop ◽  
Servo Systems ◽  
Design And Implementation ◽  
Integral Action ◽  
Dual Stage

This paper discusses the design and implementation of two track-following controllers for dual-stage hard disk drive servo systems. The first controller is designed by combining an outer loop sensitivity-decoupling (SD) controller with an inner loop disturbance observer (DOB). The second is designed by combining mixed H2/H∞ synthesis techniques with an add-on integral action. The designed controllers were implemented and evaluated on a disk drive with a PZT-actuated suspension-based dual-stage servo system. Position error signal (PES) for the servo system was obtained by measuring the slider displacement with an LDV and injecting a simulated track runout.

Optimization of Air Bearing Contours for Shock Performance of a Hard Disk Drive

2003 ◽  
Author(s):  
Eric M. Jayson ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Element Model ◽  
Time Dependent ◽  
Air Bearing ◽  
Disk Interface ◽  
Shock Response ◽  
Shock Event

Hard disk drives must be designed to withstand shock during operation. Large movements of the slider during shock impulse can cause reading and writing errors, track misregistration, or in extreme cases, damage to the magnetic material and loss of data. The design of the air bearing contour determines the steady state flying conditions of the slider as well as dynamic flying conditions, including shock response. In this paper a finite element model of the hard disk drive mechanical components was developed to determine the time dependent forces and moments applied to the slider during a shock event. The time dependent forces and moments are applied as external loads in a solution of the dynamic Reynolds equation to determine the slider response to a shock event. The genetic algorithm was then used to optimize the air bearing contour for optimum shock response while keeping the steady flying conditions constant. The results show substantial differences in the spacing modulation of the head/disk interface after a shock as a function of the design of the air bearing contour.

Flying Clearance Distribution With Thermo-Mechanical Actuation of Hard Disk Drive

2008 ◽  
Author(s):  
Sung-Chang Lee ◽  
George W. Tyndall ◽  
Mike Suk
Keyword(s):  
Environmental Change ◽  
Temperature Change ◽  
Temperature Sensitivity ◽  
Temperature Compensation ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Drives ◽  
Compensation Scheme ◽  
Mechanical Actuation

Flying clearance distribution with thermo-mechanical actuation is characterized. Especially, what factors contributing to variation of flying clearance are identified based on thermo-mechanical actuation profiles taken from burn-in process of hard disk drives and Gage R&R test of touch down repeatability. In addition, the effect of static temperature compensation scheme on flying clearance distribution is investigated and disadvantages of static adaptation to temperature change are identified. In order to avoid catastrophic early HDI failures due to poor static temperature compensation, we need to dynamically adjust flying clearance whenever environmental change is detected. Otherwise we need to utilize individual temperature sensitivity values of each flying head to adjust thermo-mechanical actuation amount accordingly with temperature change.

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