Dual Read Element Head Radial Offset Servo Tracking
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Solution Overview
Problem
Existing disk drives face challenges in accurately positioning the head over servo tracks due to corrupted servo bursts, leading to unnecessary write aborts and increased manufacturing time, especially when dealing with a large number of servo tracks.
Innovation Solution
The implementation of a dual-read element system, where a secondary read element confirms shock events and adjusts position error signals to prevent write aborts, and the use of multiple read elements with varying radial offsets to enhance servo system augmentation and multi-signal processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single read element is used to read servo bursts for head positioning, then the device complexity is low, but the reliability of servo positioning deteriorates due to corrupted servo bursts causing unnecessary write aborts
Solution Approach 1:
The patent divides the single read element function into multiple read elements (first read element and second read element). The first read element reads servo bursts from a first servo track while the second read element reads servo bursts from a second servo track. This segmentation allows independent verification of servo data, improving reliability by confirming whether position error signals are due to actual shock events or corrupted servo bursts.
Solution Approach 2:
The second read element acts as an intermediary verification mechanism. It reads servo bursts from a different servo track to provide reference data that mediates the validation process. By comparing readings from both read elements, the system can distinguish between genuine positioning errors and corrupted servo data, preventing unnecessary write aborts.
2Reliability
If multiple read elements with radial offset are implemented to confirm shock events, then the reliability of write operations improves, but the device complexity increases
Solution Approach 1:
The patent introduces a radial dimension offset between the first and second read elements. The read elements are offset radially by at least one servo track width at all radial locations, creating a spatial dimension difference. This dimensional separation allows each read element to independently sample servo bursts from different tracks, enabling cross-validation of shock events without requiring complex temporal sequencing.
3Productivity
If a single read element is used, then the manufacturing cost is low, but the manufacturing time increases due to increased write aborts
Solution Approach 1:
The system performs preliminary verification of shock events using the second read element before executing write aborts. By pre-validating whether a detected shock event is genuine or due to corrupted servo bursts, the system avoids premature write aborts that would otherwise reduce manufacturing throughput. This preliminary action ensures that write operations only abort when truly necessary.
4Measurement precision
If dual read elements offset by at least one servo track are used, then servo system accuracy improves, but the head structure complexity increases
Solution Approach 1:
The patent applies local quality by giving each read element a specific radial position and function. The first read element is positioned to read from a first servo track while the second read element is radially offset to read from a second servo track. Each read element has specialized local characteristics (different radial positions) that enable them to perform complementary functions in validating head position measurements.
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk surface comprising a plurality of servo tracks, wherein the head comprises at least two read elements including a first read element and a second read element, and at least two of the read elements are offset radially relative to a center of the two read elements by at least a width of a servo track at all radial locations of the head over the disk surface. First servo data recorded in a first servo track is read using the first read element to generate a first read signal, and second servo data recorded in a second servo track is read using the second read element to generate a second read signal. The head is servoed over the disk surface based on at least the first read signal and the second read signal.