Magnetic Disk Head Spiral Speed Adjustment for Cylinder Offset
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Solution Overview
Problem
In magnetic disk devices, positional differences between reference and copy spiral servo patterns can occur due to structural errors, leading to potential misalignment and reduced reliability during the self servo write (SSW) process.
Innovation Solution
The magnetic disk device adjusts the spiral speed of heads based on measured cylinder offset amounts to ensure accurate alignment and writing of servo patterns, using a system controller to manage the process and minimize positional differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spiral servo patterns are written by multiple heads on different surfaces, then productivity is improved through parallel writing, but manufacturing precision deteriorates due to cylinder offset between heads
Solution Approach 1:
The system performs preliminary measurement of cylinder offset between heads before the actual servo pattern writing process. This advance measurement allows the control unit to calculate and apply appropriate spiral speed adjustments beforehand, ensuring that patterns written by different heads will align correctly without requiring rework or correction after writing.
Solution Approach 2:
The invention changes the spiral writing speed parameter dynamically based on measured cylinder offset values. By adjusting the spiral speed of individual heads according to their specific positional deviations, the system compensates for mechanical inaccuracies and achieves precise pattern alignment across multiple surfaces, resolving the contradiction between parallel writing efficiency and alignment precision.
2Ease of operation
If cylinder offset is not corrected, then ease of operation is maintained by using fixed spiral speed, but reliability deteriorates due to positional differences between reference and copy patterns
Solution Approach 1:
The system implements a feedback mechanism where the actual cylinder offset between heads is measured and this information is fed back to the control unit. The control unit then automatically adjusts the spiral writing speed based on this feedback, creating a closed-loop control system that maintains high reliability without requiring manual intervention or complex operational procedures from the user.
Data Source
AI summary
According to one embodiment, a magnetic disk device comprises a disk, a first head, a second head, a controller. The disk includes a first surface and a second surface different from the first surface. The first head carries out read and write of data from and to the first surface. The second head carries out read and write of data from and to the second surface. The controller adjusts a spiral speed of at least one of the first head and the second head according to a cylinder offset amount corresponding to a positional difference between the first head and the second head. The spiral speed is a speed at which spiral servo patterns are to be written.