Harmonic Sensor Fly Height Control via Frequency Domain Analysis
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Solution Overview
Problem
Existing methods for determining the fly height of a read/write head in hard disk drives are inefficient, as they rely on detecting predetermined patterns, which can lead to inaccurate data storage and potential physical damage due to either excessive or insufficient head-medium separation.
Innovation Solution
A fly height control system that employs a weighting function module to apply coefficients to digital samples, allowing harmonic sensors to estimate frequencies in the frequency domain, enabling precise determination and adjustment of the read/write head's height based on the ratio of first and third harmonic magnitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If predetermined patterns are used for fly height detection, then the detection method is simple to implement, but the measurement precision deteriorates due to inaccurate fly height determination
Solution Approach 1:
The patent transforms the detection approach by changing the parameter domain from time-domain pattern recognition to frequency-domain harmonic analysis. By converting the read signal through Fourier transform and analyzing the ratio of harmonic magnitudes (first harmonic to third harmonic), the system achieves more accurate fly height measurement without requiring predetermined patterns on the storage medium.
2Ease of operation
If fly height is not accurately maintained, then the system operation is simple, but the reliability deteriorates due to potential data loss or physical damage
Solution Approach 1:
The patent implements a feedback mechanism where the harmonic sensor continuously monitors the fly height by analyzing the ratio of first and third harmonic magnitudes from the read signal. This feedback information is fed to the controller, which adjusts the head position accordingly. This closed-loop control maintains reliable data storage by preventing both excessive fly height (which would cause read errors) and insufficient fly height (which would cause head-medium contact and physical damage).
Data Source
AI summary
A system including a weighting function module, a frequency sensor module, and a control module. The weighting function module is configured to receive a plurality of samples of data, the data having been obtained based on a head having read the data from a storage medium while the head was at a given height above the storage medium, and to apply a weighting function to the plurality of samples to generate weighted samples. The frequency sensor module is configured to estimate, based on the weighted samples, (i) a first magnitude of a first frequency component, and (ii) a second magnitude of a second frequency component. The control module is configured to estimate, based on the first magnitude and the second magnitude, the height of the head above the storage medium.