硬盘介绍(英文)

Experiment Details: Dual Element Confocal Transducer
600 kHz broadband (>100 kHz bandwidth) 70 mm focal length; 1 mm focus spot size Confocal (concentric elements with different frequencies) Inner disk fixed at f1=550 kHz Outer ring swept sine f2=551–570 kHz Difference frequency of ∆f = 1 kHz – 20 kHz Caused excitation of suspension Dual beams mean essentially silent operation since frequencies only combine at small spot on suspension
Hard Drive HGA Suspension
HGA (Head Gimbal Assembly) suspension holds hard drive read/write heads Read/write head is attached to the flexure Flexure can gimbal around dimple Head flies over spinning disk surface Hinge and load beam provide downward force to balance lift from flying head Suspension length about 10-14.5 mm , thickness of 25-100 µm Typical width about 4-6 mm
Experiment Details: Amplitude Modulated Excitation
Instead of two transducer elements producing the two frequencies, an alternate method is an amplitude-modulated signal to cause excitation
Leading Manufacturer: Hutchinson Technology
Headquarters in Hutchinson, MN (about 50 miles west of Minneapolis) Manufacturinห้องสมุดไป่ตู้ plants in Hutchinson and Plymouth, MN, Sioux Falls, SD, Eau Claire, WI. Typical production rate of 14 million suspensions per week Worldwide market leader of suspension assemblies Virtually all shipped to other countries for integration into hard drives Production monitoring involves resonance testing of small fraction of suspensions Suspension mounted on mechanical shaker for excitation (1-20 kHz) Laser doppler vibrometer used for non-contact measurement R&D measurements of resonance frequency and deflection shapes
Ultrasound excitation of HGA Suspension
Goal: To determine whether vibrational resonances of suspension can be excited using ultrasound radiation force To simulate an operational disk, end of suspension clamped the gimbal head was simply supported on flat surface Confocal ultrasound transducer used to excite modes from 1 kHz to 50 kHz Vibrometer measured resonance frequencies and deflection shapes at several ultrasound focus positions Brüel & Kjær mechanical shaker used for comparison
Ultrasound Stimulated Vibrometry for Suspensions
Pair of ultrasound frequencies directed at suspension One ultrasound frequency differs from the other by frequency ∆f that may be in the audio range or higher frequency Difference frequency ∆f between ultrasound beams produces radiation force that causes vibration of object Vibrations were detected using a Polytec laser Doppler vibrometer In some experiments, comparison of ultrasound excitation and mechanical shaker
Dual sideband, carrier suppressed amplitude modulated signal centered, for example, at 550 kHz Difference frequency of ∆f = 1 kHz – 20 kHz between the two frequency components caused excitation Better for excitation since entire transducer producing the same signal (no need for mixing near surface). Unfortunately, small fraction of both frequencies are combined in transducer, so some audio emitted
Hard Drive HGA Suspension
Head slider flies about ~10 nm above surface of the disk Human hair ~50 m (or 50,000 nm) in diameter Scale to macroscopic size – equivalent to 747 flying about 1mm above ground In operating hard drive, vibration of head (pitch, roll, or sway) may cause loss of data or head crash Instead of damping vibrations, suspensions are engineered to have specific vibrational frequencies
Weaknesses in current shaker/vibrometer test protocol
Smaller hard drives require smaller suspensions Requires modal testing between 1 kHz to about 50 kHz Existing mechanical shakers not useful above 20 kHz Fixture modes: vibrations of support assembly unrelated to suspension Use of shaker assembly eliminates possibility of in-situ testing of operating hard drive
Can ultrasound radiation force be used for non-contact excitation?
Ultrasound Stimulated Radiation Force Excitation
Vibro-Acoustography Developed in 1998 at Mayo Clinic Ultrasound Research Lab by Fatemi & Greenleaf Difference frequency between two ultrasound sources causes excitation of object. Detection by acoustic reemission Technique has been used for imaging in water and tissue (Thursday AM Session 4aBB: Acoustic Radiation Force Methods for Medical Imaging and Tissue Evaluation) Recently, we have also used the ultrasound radiation force for modal testing of organ reeds and MEMS devices in air
Introduction
Overview of hard drives and head-gimbal-assembly suspensions Non-contact, ultrasound stimulated excitation Overview Selective excitation by varying focus position Selective excitation of neighboring parts Selective excitation by phase shift In-Situ measurements of suspension vibration Conclusions
Photos of Setup
Comparison of Shaker and Ultrasound Excitation
Ultrasound excitation: 501 – 520 kHz swept sine and 500 kHz fixed tone (red curve) Brüel & Kjær mechanical shaker (blue curve) Ultrasound excitation reproduces the resonances measured using mechanical shaker Ultrasound excitation produces a cleaner spectrum than shaker