Frequency Preamble Head Positioning for Disk Drive Intertrack Interference
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Solution Overview
Problem
Existing data storage devices face challenges in accurately positioning the head over data tracks due to vibrations during write operations, leading to off-track writes and subsequent intertrack interference, which can result in unrecoverable data sectors during read operations.
Innovation Solution
The implementation of different frequency preambles written to adjacent data tracks allows for the generation of a jog value and preamble position error signal (PES) to adjust the head's position, enabling retry reads and improved tracking accuracy by evaluating frequency components to determine the correct jog direction and magnitude, and using the preamble PES for servoing the head during read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the head is positioned over a target data track during write operations, then data can be written to the intended track, but vibrations cause off-track writes leading to intertrack interference
Solution Approach 1:
The system performs preliminary actions by writing preambles with specific frequency signatures to each track before normal data writing. These preambles serve as reference markers that enable later identification and compensation of track position deviations caused by vibrations during write operations.
Solution Approach 2:
The system uses feedback by reading back the preambles written to tracks, comparing the actual frequency content with expected frequencies, and generating position error signals. These feedback signals are used to adjust head positioning and compensate for off-track writes, thereby reducing intertrack interference.
2Ease of operation
If traditional servo methods are used for head positioning, then head position can be controlled, but off-track writes due to vibrations cannot be compensated in real-time
Solution Approach 1:
The system replaces traditional mechanical servo positioning methods with a signal-processing-based approach. By using frequency analysis of preambles and generating electronic position error signals, the system achieves more precise and responsive head positioning control that can compensate for vibrations in real-time.
Solution Approach 2:
The system changes the parameter used for positioning feedback from traditional servo marks to frequency-based preamble signatures. By analyzing the frequency content of read preambles and comparing it with expected frequencies, the system can detect track position deviations and generate appropriate correction signals.
3Productivity
If data sectors are read from tracks with intertrack interference, then read operations can proceed, but unrecoverable errors occur reducing data reliability
Solution Approach 1:
The system extracts the harmful intertrack interference by using frequency-selective filtering. By identifying the frequency signature of the interfering adjacent track preamble and filtering it out, the system recovers the clean signal from the target track, enabling successful data recovery even in the presence of vibrations.
Data Source
AI summary
A data storage device is disclosed comprising a disk comprising a plurality of data tracks each comprising a plurality of data sectors, and a head actuated over the disk. A first frequency preamble is written to a first data sector of a first data track and a second frequency preamble is written to a second data sector of a second data track, wherein the first frequency is different from the second frequency and the first data track is adjacent to the second data track.