Ultra sensitive in-situ acoustic characterization system for HDD head disc interface defectoscopy

Abstract

An ultra sensitive drive level acoustic characterization system has been developed for in-situ Head Disc Interface defectoscopy. Multimode acoustic emission (AE) sensor installed on the drive cover is designed for tracking air bearing (AB) and slider modes. Monitored modal changes at the AB and slider bandwidth correlate to the weak head disc interface (HDI) interactions such as lubricant modulation and particles induced defects. Two or three orders of magnitude increase in sensitivity can be achieved by a combination of advanced sensors, data acquisition hardware and digital signal processing algorithms. Continuous and Discrete Wavelet Transform and Joint Time-Frequency analyses are implemented for the AB modal data mining process. Performance of the newly developed technology is demonstrated on a normally operating hard disc drive (HDD).

Passive acoustic monitoring of head disc interface interactions

“…6, was discussed in detail by Daugela et al (2007). This system is a synergy of AE sensors, a high performance data acquisition system, and digital AE signal processing routines.…”

“…This fact suggests that a drive level ultra sensitive in situ AE monitoring technique is capable of capturing weak HDI interactions caused by degrading lubricant and particle induced slider and disc interference (e.g. Daugela et al 2007) as well as head thermal protrusion induced contact detect.…”

“…A discrete wavelet filtering technique for individual HDI fingerprinting and weak HDI interactions monitoring was introduced by Daugela et al (2007). In the present work the adaptive discrete wavelet (ADW) filtering technique is used to characterize contact detection events during head thermal protrusion process.…”

Sensing and Identification of Nonlinear Dynamics of Slider with Clearance in Sub-5 Nanometer Regime

“…Actually, all of the current simulations on slider dynamics have used nonlinear physics models. However, all of the related experimental characterizations have used Fourier transform or wavelet transform to interpret data [1,2,5,6,92,93]. There are certain limits in these applications as the obvious gap between the simulation and experiment exists.…”

“…The experimental investigations of transient dynamics of sliders have been widely conducted using laser Doppler vibrometer (LDV) signal, acoustic emission (AE)/PZT signal, and read/write signal. The analyses of nonstationary and nonlinear signals of slider dynamics have been implemented by using Fourier analysis-based time-frequency analysis (TFA) and wavelet transformation (WT) in HDDs area by industry and university labs [1,2,5,6,92,93]. For slider dynamics in nanometer clearance regime, the effects of air-bearing, intermolecular adhesion, contact and lubricant effect, as well as other factors yield nonlinear responses.…”