Head instability detection method and apparatus

Details Head instability detection method and apparatus Head instability detection method and apparatus

1998-05-13

2001-06-19

Sniezek, Andrew L. (Department: 2651)

Dynamic magnetic information storage or retrieval

Monitoring or testing the progress of recording

C360S075000, C324S210000

Reexamination Certificate

active

06249392

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to disc drive servo systems. In particular, the present invention relates to servo read signals in servo systems.
BACKGROUND OF THE INVENTION
Magnetic storage devices store data on magnetic media using write heads that generate small magnetic fields. As a write head passes over a medium, its small magnetic field alters localized magnetic moments on the medium. Data is retrieved from magnetic media using read heads that sense transitions in the localized magnetic fields generated by each of these magnetic moments. In response to each of these transitions, a read head generates electrical pulses that are part of a series of pulses forming a read signal. The pulses are either positive or negative depending on the direction of the magnetic moment transition.
Ideally, a read head produces identically shaped pulses for each transition in the magnetic moment. In general, these pulses should be symmetric about their peaks and should have the same general shape during the entire life of the head. However, improperly manufactured heads or heads that have suffered damage may produce excessively asymmetric pulses, may produce different pulse shapes over time, or may produce inconsistent pulse shapes.
New heads that produce excessively asymmetric pulses or existing heads that begin to produce different or inconsistent pulse shapes are sometimes referred to as unstable heads. An unstable head, although functional, is undesirable since it is more likely to fail or “crash”. In fact, before crashing, many stable heads become unstable for a period of time.
Since data can be lost when a head crashes, it is desirable to identify unstable heads before they crash. However, the prior art has not provided a method of detecting unstable but functional heads.
The present invention addresses these and other problems, and offers other advantages over the prior art.
SUMMARY OF THE INVENTION
A method and apparatus detects pulse asymmetries in a read signal of a data storage device. The read signal is rectified through multiplication with a rectification signal to produce a product signal. The product signal is integrated to produce integrands indicative of pulse asymmetry. In some embodiments of the present invention, the integrands are compared against a baseline value to determine a performance characteristic of a read head in the data storage device.
In preferred embodiments of the present invention, the performance of the head is measured several times over the life of the data storage device. Each measurement produces a performance value and excessive changes in the performance values over time indicate that the head is unstable.


REFERENCES:
patent: 5117408 (1992-05-01), Weispfenning et al.
patent: 5301080 (1994-04-01), Ottesen et al.
patent: 5367409 (1994-11-01), Ottesen et al.
patent: 5586144 (1996-12-01), Kahlman et al.
patent: 5677802 (1997-10-01), Saiki et al.
patent: 6025712 (2000-02-01), Mian
patent: 359033618A (1984-02-01), None
patent: 360070552A (1985-04-01), None

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