Disk Drive Track Trajectory Optimization for AC Squeeze
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Solution Overview
Problem
Conventional disk drives face inefficiencies in shingled recording due to excessive track pitch margins, which reduce data capacity and radial density, as they compensate for worst-case AC track squeeze, leading to unnecessary spacing between data tracks.
Innovation Solution
The solution involves estimating and adjusting the track pitch for each data segment to achieve a target track pitch, using quality metrics like sector error rate and signal-to-noise ratio to generate track trajectories that minimize off-track deviations, thereby reducing the margin added to the track pitch and increasing data capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If track pitch margins are increased to compensate for worst-case AC track squeeze, then tracking reliability is improved, but data capacity and radial density deteriorate
Solution Approach 1:
The patent applies local quality by transitioning from uniform track pitch margins across the entire disk to variable track pitch margins specific to each radial zone. Each zone's track pitch is individually optimized based on its specific AC track squeeze characteristics, allowing minimal margins where needed and larger margins only where physically necessary, thereby maximizing data capacity while maintaining tracking reliability.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the track pitch parameter for each radial zone based on measured AC track squeeze characteristics. The servo controller modifies track pitch values in different zones rather than using a fixed global value, enabling optimization of both reliability and capacity through parameter adaptation to local conditions.
2Device complexity
If uniform track pitch is used across all radial zones, then device complexity is reduced, but manufacturing precision deteriorates due to inability to compensate for zone-specific AC track squeeze variations
Solution Approach 1:
The patent applies segmentation by dividing the disk surface into multiple radial zones, each with its own optimized track pitch value. This segmentation allows the system to account for zone-specific AC track squeeze variations without requiring a completely complex custom configuration for every location, as the segmentation into manageable zones simplifies the overall control structure while improving precision.
Solution Approach 2:
The patent implements local quality by assigning different track pitch values to different radial zones based on their specific AC track squeeze characteristics. Each zone receives a tailored track pitch configuration that matches its physical conditions, achieving high manufacturing precision through localized optimization rather than uniform treatment.
3Measurement precision
If excessive track pitch margins are added to compensate for AC track squeeze, then head positioning accuracy is improved, but radial density deteriorates
Solution Approach 1:
The patent implements parameter changes by adjusting the track pitch parameter for each radial zone based on measured AC track squeeze characteristics. The servo controller modifies track pitch values in different zones rather than using a fixed global value, enabling optimization of both reliability and capacity through parameter adaptation to local conditions.
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments. First data is written to data segments of a first data track, and second data is written to data segments of a second data track. After writing the second data, the first data is read at multiple off-track offsets of the first data track to measure an average off-track read capability (OTRC) of the first data track. A cross-track profile is generated for a first data segment of the first data track, and at least part of the cross-track profile is correlated with the measured average OTRC.