Magnetic Disk RRO Learning with Skipped Radial Measurements
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Solution Overview
Problem
Repeatable run-out (RRO) causes positional deviations in magnetic head positioning due to fluctuations in synchronization with the rotation of the magnetic disk, leading to positioning errors in magnetic disk apparatuses, which are not effectively addressed by conventional correction methods.
Innovation Solution
A magnetic disk apparatus that measures RRO correction values at selected positions, skipping measurements at specific positions to reduce the time required for RRO learning, and uses interpolation to estimate correction values at unmeasured positions, thereby enhancing positioning accuracy and reducing the overall measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RRO correction values are measured at all radial positions, then positioning accuracy is improved, but measurement time increases
Solution Approach 1:
The patent segments the radial positions into two groups: specific positions where RRO correction values are measured, and other positions where values are estimated through interpolation. This segmentation allows the system to measure correction values at only critical positions rather than all positions, thereby reducing measurement time while maintaining positioning accuracy through mathematical estimation at unmeasured positions.
Solution Approach 2:
The system uses the measured RRO correction values at specific positions to automatically generate estimated correction values at other positions through interpolation algorithms. This self-service mechanism eliminates the need for manual or time-consuming measurements at all positions, as the system autonomously computes the necessary correction values based on the measured data and mathematical relationships.
2Reliability
If RRO correction values are measured at all radial positions, then correction completeness is improved, but productivity decreases
Solution Approach 1:
The patent divides the radial positions into specific measurement positions and other positions, measuring RRO correction values only at the segmented specific positions. This selective measurement approach maintains correction completeness for critical positions while significantly improving RRO learning efficiency by reducing the total number of measurements required.
Solution Approach 2:
The system performs partial measurement by measuring RRO correction values at only some radial positions rather than all positions. This partial action is sufficient to achieve effective RRO correction because the measured values are used to estimate correction values at unmeasured positions through interpolation, thereby improving productivity without sacrificing correction effectiveness.
3Loss of time
If measurement process is simplified by skipping positions, then measurement time is reduced, but measurement precision may worsen
Solution Approach 1:
The patent introduces interpolation as an intermediary mechanism that bridges the gap between measured positions and unmeasured positions. By using mathematical interpolation based on measured RRO correction values at specific positions, the system generates accurate estimates for correction values at other positions, thereby maintaining positioning accuracy despite skipping measurements at certain radial positions.
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
The solution improves the efficiency of RRO correction value measurement by skipping unnecessary measurements, thereby reducing the time required for RRO learning and enhancing the positioning accuracy of the magnetic head in magnetic disk apparatuses.
Implementation Method 1
acquiring a first position error signal by the read head while keeping the read head at the fourth position
Implementation Method 2
perform write access to the magnetic disk
Data Source
AI summary
According to one embodiment, multiple first positions are set in a radial direction of a magnetic disk. The multiple first positions include multiple second positions and a third position different from the multiple second positions. A controller of a magnetic disk apparatus executes a first process in which an RRO correction value is measured at each of the multiple second positions and measurement of an RRO correction value at the third position is skipped. After the first process, the controller executes a second process of performing write or read access to multiple tracks. The second process includes acquiring a position error signal by a read head during the write or read access, and calculating an RRO correction value for the third position based on the position error signal.