Disk Drive Servo Track Pitch Control via Spiral Slope Calculation
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Solution Overview
Problem
Existing methods for writing servo data in disk drives using spiral servo patterns result in varying track densities due to changes in the slope of the spiral patterns, leading to inconsistent positioning and data recording.
Innovation Solution
A method and apparatus that calculate the slope of spiral servo patterns to determine the track pitch of target servo patterns, allowing for the writing of servo tracks at regular intervals, independent of the slope, ensuring stable density and consistent positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spiral servo patterns are written on the disk medium, then servo data can be recorded, but the track density varies due to changes in the slope of the spiral patterns
Solution Approach 1:
The patent changes the parameter of track pitch determination from being slope-dependent to being explicitly calculated and set. By calculating the track pitch based on the number of revolutions of the spiral servo patterns rather than relying on the slope, the system achieves stable track density despite variations in spiral pattern slope. This parameter transformation resolves the contradiction by making track pitch independent of slope variations.
2Measurement precision
If the track pitch is determined from the slope of spiral servo patterns, then servo tracks can be written, but the positioning consistency deteriorates when slope changes
Solution Approach 1:
The patent implements a feedback mechanism where the actual slope of the spiral servo patterns is measured and detected. This measured slope information is then used to calculate and adjust the track pitch accordingly. By incorporating feedback about the actual spiral pattern characteristics, the system can compensate for slope variations and maintain consistent positioning accuracy across different spiral patterns.
Solution Approach 2:
The patent performs preliminary calculation of the track pitch based on the detected slope of spiral servo patterns before writing the target servo pattern. By calculating the appropriate track pitch in advance, taking into account the actual spiral pattern characteristics, the system ensures that subsequent positioning operations will be accurate. This preliminary action prevents positioning errors before they occur.
Data Source
AI summary
According to one embodiment, a method of writing a target servo pattern constituting concentric servo tracks on a disk medium provided in a disk drive. In the method, a cumulative amplitude value of the waveform of each spiral servo pattern reproduced by the head of the disk drive is calculated, a slope of each spiral servo pattern is calculated from the cumulative amplitude value, and a pitch at which the head should be moved to write the target servo pattern is determined on the basis of the slopes of the spiral servo patterns.