Self-Servo-Write Non-Integer Wedge Ratio
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Solution Overview
Problem
Current self-servo-write (SSW) systems in hard disk drives (HDDs) are limited by the ratio of final wedges to servo spirals, where the number of final wedges that can be written is constrained by the number of spirals, and overwriting spirals reduces the available timing and positioning information, affecting accuracy.
Innovation Solution
The SSW system employs a non-integer ratio of final wedges to servo spirals, allowing more than S final wedges to be written by selecting a ratio greater than 1, with fewer spirals overwritten, using a timing control module, position control module, and error processing to generate and synchronize control signals for writing final servo wedges in circles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an integer ratio of final wedges to servo spirals is used, then the writing process is simpler, but the number of final wedges that can be written is limited and spiral overwriting reduces timing and positioning information
Solution Approach 1:
The patent changes the ratio parameter from an integer to a non-integer value (e.g., 5:3 or 8:5). This parameter change allows the system to write more final wedges relative to the number of servo spirals while reducing the overlap and preservation of timing information. Specifically, when F/S > 1, more final wedges are written per spiral, and the non-integer nature ensures better distribution and reduced information loss.
2Manufacturing precision
If more final wedges are written, then servo accuracy is improved, but spiral overwriting increases reducing available timing information
Solution Approach 1:
By implementing a non-integer ratio F/S where F > S, the patent achieves higher servo writing accuracy through increased final wedge density while simultaneously reducing spiral overwriting. The specific non-integer ratio ensures optimal balance between writing capacity and information preservation, allowing precise servo patterns without excessive loss of timing data from the underlying spirals.
Data Source
AI summary
A self-servo-write system including a timing control module and a position control module. The timing control module is configured to generate (i) timing information of a first set of servo spirals and (ii) timing control signals for writing a second set of final servo wedges based on the timing information. The position control module is configured to generate (i) position information of the first set of servo spirals and (ii) positioning control signals for writing the second set of final servo wedges based on the timing information. Less than half of the servo spirals in the first set of servo spirals are over-written while writing the second set of final servo wedges. A ratio of a first number of final servo wedges in the second set of final servo wedges to a second number of servo spirals in the first set of servo spirals is a non-integer greater than one.