Narrowband Performance of Active Control on Flow-Induced Vibrations Inside Hard Disk Drives

2013 ◽  
Author(s):  
Hequn Min ◽  
Xiaoyang Huang ◽  
Qide Zhang ◽  
Xin Xia
Keyword(s):  
Active Control ◽  
Hard Disk Drives ◽  
Laser Doppler Vibrometer ◽  
Hard Disk ◽  
Disk Drive ◽  
Modal Testing ◽  
Disk Drives ◽  
Feedback Error ◽  
Flow Induced Vibrations ◽  
Narrow Bands

This paper presents an experimental study of digital narrowband active control on the flow-induced vibrations (FIV) on the head gimbals assembly (HGA) in a working hard disk drive (HDD). Firstly, the modal testing on the HDD was carried out, in which the disk modes were analyzed with a 1-D laser Doppler vibrometer (LDV) and the HGA vibration modes with a 3-D LDV. Secondly, a digital feedback control close-loop was implemented in experiments to suppress the FIV spectrum peaks on the HGA. In this close-loop, the HGA vibrations detected by the LDV were used as feedback error signals, then the signals was passed through a digital controller to generate feedback signals to drive a piezoelectric disk to actuate feedback acoustic pressure around the HGA. Active control experiments were conducted in narrow bands on five principal peaks in the HGA off-plate vibration spectrum, around 1256Hz, 1428Hz, 2141Hz, 2519Hz and 3469Hz, respectively. It is shown that distinct suppression of at least 10 dB can be achieved on all these HGA vibration peaks.

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.

Numerical Modeling of Flow-Induced Suspension Vibrations in Hard Disk Drives

2003 ◽  
Author(s):  
Mohammad Kazemi ◽  
Hossein Haj-Hariri ◽  
Joseph A. C. Humphrey
Keyword(s):  
Vibration Analysis ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Positioning Error ◽  
Disk Drives ◽  
Magnetic Head ◽  
Aerodynamic Loads ◽  
Head Positioning ◽  
Flow Induced Vibrations

The problem of flow-induced vibrations of suspensions in a hard disk drive is studied numerically. The 2D unsteady flow field is calculated by solving the continuity and momentum equations for a fluid with constant physical properties. In addition, a 2D vibration analysis is employed to study the flowinduced oscillations of the suspension. The calculated aerodynamic loads are used to determine the response of the suspension and, consequently, the magnetic head positioning error.

Narrowband performance of active control on flow-induced vibrations inside hard disk drives

2014 ◽  
Vol 20 (8-9) ◽  
pp. 1557-1563 ◽  
Author(s):  
Hequn Min ◽  
Xiaoyang Huang ◽  
Qide Zhang
Keyword(s):  
Active Control ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drives ◽  
Flow Induced Vibrations

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.

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.

A Near Zero Skew Actuation Mechanism for Hard Disk Drives

2013 ◽  
Author(s):  
Zhimin He ◽  
Jianqiang Mou ◽  
Kheong Sann Chan ◽  
Suet Hoi Lam ◽  
Boon Long See ◽  
...  
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Outer Diameter ◽  
Disk Drives ◽  
Skew Angle ◽  
Link Mechanism ◽  
Tracking Direction ◽  
The Difference ◽  
Zero Skew

One of the issues in VCM rotary actuation in hard disk drives (HDDs) is the excessive sensitivity of the system to the skew angle. The rotation of the VCM from the inner diameter (ID) to the outer diameter (OD) of the disk results in an angle of skew between the read/write head and the track. The difference in skew angle, between the ID to the OD can be as large as 25 to 30 degrees in conventional 3.5″ and 2.5″ HDDs. A large skew angle affects the slider’s flying performance and off-track capability, causing an increase in side reading and writing, and thus reduces the achievable recording density. Large skewed actuation also complicates the position error signal calibration process in the hard disk drive servo loop. This paper presents a 4 link mechanism which can be designed to achieve near zero skew actuation in hard disk drives. The profiles of the arm, suspension, and links can be designed and optimized such that the skew angle is close to zero while the VCM actuator rotates from the ID to the OD. Study shows that the 4-link mechanism does not degrade the resonance performance along the tracking direction compared to a conventional actuator.

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.

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