Disk Surface Irregularity Detection Using VGA Profiles
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Solution Overview
Problem
Conventional methods for detecting surface irregularities in rotating magnetic disks are prone to false indications due to noise and variations, leading to manufacturing inefficiencies and potential data reading/writing errors.
Innovation Solution
The implementation of a surface irregularity detection process using Variable Gain Amplifier (VGA) values, filtered with Gaussian or differential Gaussian filters, to generate profiles that are compared to adaptive thresholds, reducing false indications and improving the detection of significant irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional detection methods are used, then the detection process is simple, but false indications increase due to noise and variations
Solution Approach 1:
The patent applies preliminary action by performing multiple measurements at different radial positions and averaging the results before threshold comparison. This pre-processing of data reduces the impact of noise and variations, thereby reducing false indications while maintaining a relatively simple detection architecture.
Solution Approach 2:
The patent implements feedback by adaptively adjusting the threshold based on the measured VGA values and their variations. The threshold is not fixed but is determined from the actual measurement data, allowing the system to compensate for noise and variations dynamically, thus improving detection reliability without requiring complex additional hardware.
2Manufacturing precision
If the fly height is reduced to improve data density, then storage capacity increases, but sensitivity to surface irregularities increases causing errors
Solution Approach 1:
The patent performs preliminary detection of surface irregularities by measuring VGA values at multiple radial positions and averaging them before making a determination. This preliminary averaging action smooths out the signal and reduces the impact of small surface irregularities, allowing the system to operate at lower fly heights without excessive sensitivity to contaminants or warping.
3Measurement precision
If detection thresholds are set low to detect all irregularities, then detection sensitivity increases, but false positives increase due to noise
Solution Approach 1:
The patent applies preliminary action by measuring and averaging VGA values across multiple radial positions before comparing against the threshold. This averaging process acts as a filter that reduces noise while preserving genuine irregularities, allowing the use of lower thresholds without proportionally increasing false positives.
Solution Approach 2:
The patent uses partial action by only comparing the averaged VGA values against the threshold rather than analyzing every individual measurement point. This partial averaging approach provides sufficient noise reduction to lower the threshold without creating excessive false positives, striking an optimal balance between sensitivity and reliability.
Data Source
AI summary
Detecting surface irregularities on a disk of a data storage device (DSD) includes reading data from a first side of the disk using a first head of the DSD. A first set of variable gain amplifier (VGA) values is generated which is related to the reading of data from the first side using the first head. Data is read from a second side of the disk using a second head of the DSD and a second set of VGA values is generated which is related to the reading of data from the second side using the second head. A profile for the disk is determined using the first set of VGA values and the second set of VGA values. The profile is compared to at least one threshold to detect surface irregularities on the disk.