PES Offset Servo Segments for Track Position Encoding
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Solution Overview
Problem
Conventional servo systems for patterned media struggle to accurately read track IDs due to asymmetric features incompatible with self-assembled patterns, leading to poor track location resolution during seek operations in high-density magnetic disk drives.
Innovation Solution
The solution involves systematically varying the downtrack length of the PES offset portion by a fraction of the track pitch, allowing the servo system to encode track position information even when the track ID code cannot be read, and using redundant track IDs and preamble timing marks to enhance reading accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional servo patterns with symmetric features are used on patterned media, then the patterns are compatible with self-assembled fabrication methods, but the track ID reading accuracy deteriorates due to asymmetric feature requirements
Solution Approach 1:
The patent introduces asymmetric features into the servo pattern design by offsetting the PES bursts from the track centerline by a fraction of the track pitch. This asymmetric offset portion allows the pattern to maintain compatibility with self-assembled fabrication while enabling improved track location resolution through the systematic variation of offset length, thereby resolving the contradiction between manufacturing compatibility and measurement precision.
Solution Approach 2:
The patent adds a new dimension to the servo pattern by systematically varying the downtrack length of the offset portion according to track position. This length encoding provides additional information about track location that complements the traditional track ID fields, allowing the system to achieve accurate track identification even when conventional reading methods fail due to fabrication constraints.
2Measurement precision
If track ID fields are made readable during seek operations, then track location resolution improves, but the servo pattern complexity increases due to additional encoding requirements
Solution Approach 1:
The patent encodes track position information in the downtrack length of the offset portion, adding a temporal/dimensional dimension to the servo pattern. This length-based encoding provides coarse track location information during seeks without requiring complex additional fields, as the varying length itself carries the positional information that simplifies the overall pattern design.
Solution Approach 2:
The offset portion acts as an intermediary element between the track centerline and the PES bursts. By systematically varying its length, it provides intermediate positional information that bridges the gap between coarse track identification during seeks and fine positioning during data operations, reducing the need for more complex encoding schemes.
3Loss of information
If the downtrack length of PES offset portion is systematically varied to encode track position, then track position information is improved, but the servo pattern design complexity increases
Solution Approach 1:
The patent uses the downtrack length dimension of the offset portion to encode track position information. This approach transforms a spatial parameter (length) into an information carrier, allowing the servo pattern to convey positional data without adding more elements or complex structures. The systematic variation of length provides a straightforward encoding scheme that is easier to implement than alternative methods.
Solution Approach 2:
The patent changes the physical parameter of the offset portion's downtrack length to encode track position. By systematically varying this parameter according to track position, the system stores and communicates positional information through a single geometric parameter, avoiding the need for multiple separate encoding fields or complex pattern arrangements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves track position resolution and reading accuracy, enabling the servo system to maintain head positioning precision across the disk, even in high-density patterned media, with increased likelihood of successful track ID reading and reduced seek and settle time.
Implementation Method 1
systematically varying the downtrack length of the PES offset portion according to the track position to provide information about the track position
Implementation Method 2
After the e-beam patterning, block copolymer self-assembly can be used to improve the uniformity of the e-beam dots and to fill-in missing dots. Self-assembled structure fills in the gaps as the self-assembled polymer minimizes the energy of the system.
Implementation Method 3
The servo fields, which encode positional information, are permanently written onto the disk during the manufacturing process. The servo information is processed by an electronics control system that adjusts the physical position of the actuator on which the heads are mounted.
Data Source
AI summary
Patterned discrete track magnetic media compatible with the constraints imposed by the use of self-assembly technology are described in which the PES servo portion of each servo sector has at least one offset segment used for the position error signal (PES). The downtrack length of the PES offset segment systematically varies according to the track position to encode information about the track position usable by the servo system. The downtrack length of the offset segment and, therefore, the time between the corresponding signal shifts is systematically varied from the inner diameter (ID) to the outer diameter (OD) according to the track position to provide coarse information to the servo system even if part of the track ID code cannot be read. Alternative embodiments include a preamble timing mark formed by another offset segment. A self-servo writing method is described using the preamble timing marks.