Jon D. Trantham

HAMR Drive Performance and Integration Challenges

The commercialization of heat-assisted magnetic recording (HAMR) presents some significant technical challenges that need to be resolved before the widespread adoption of the technology can begin. In this paper, we present some HAMR data from prototype drives and discuss some of the challenges related to protrusion management, recording performance optimization, and drive power requirements within the drive.

Entropy-Based Multi-Resolution Head/Media Contact Detection for Hard Disk Drive

A double entropy-based characterization methodology is proposed for the hard disk drive (HDD) head/media contact detection operation. At first, signal entropy minimization is used to extract the head/media modulation-induced proximity sensor response converting it into four compact and descriptive parameters derived from an adaptive discrete wavelet transform (ADWT). The second stage and the head/media contact decision process involve statistical screening of moving entropies derived from the four ADWT parameters. This double entropy methodology provides significantly improved head/media contact decision fidelity and targets modern HDD products.

Multi-Resolution HDD Contact Detection Technique for Low SNR Applications

A quick and reliable active flying height calibration is critical in today’s hard disc drive short product development and high volume production cycles. In addition to the servo signals, passive HDI acoustic and proximity monitoring techniques are tracking equilibrium of the head gimble assembly and air bearing modes. Passive acoustic HDI monitoring had been proven to be capable in active head protrusion detection applications [1] where derived passive and active Air Bearing flying profiles help to set active flying clearance. With enhanced sensitivity, passive acoustic techniques such as AE can detect embedded particles [2]. The drawback of this technique is that noisy HDD environment causes loss of detectability of the useful AE signal [3]. Special attention has to be paid for extracting desirable HDI information. On the other hand, recording head based proximity probes are immune to torsional HDI modes and operate on pitch mode induced modulation. Advanced HDD today uses a combination of recording head based proximity sensors that are designed to sense HDI modulation at close proximity to the disc. It has to be pointed out that interpretation of proximity probe contact signatures always has been challenging.Copyright