Multi-Head RRO Correction for Magnetic Disk Positioning
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Solution Overview
Problem
Existing magnetic disk devices face challenges in efficiently correcting the position of the head due to repeatable runout (RRO) errors, particularly in two-dimensional magnetic recording systems, where measuring RRO across multiple radial positions increases measurement time and complexity.
Innovation Solution
A magnetic disk device with multiple read heads simultaneously acquires correction data, writes first and second correction data to the disk, and corrects the head position based on this data, utilizing a system controller to execute RRO learning and position correction processes efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RRO is measured at multiple different positions in the radial direction to improve correction accuracy, then head position correction accuracy is improved, but measurement time increases
Solution Approach 1:
The disk surface is divided into multiple radial regions, and RRO measurement is performed simultaneously at multiple segmented positions using multiple read heads. This segmentation allows parallel measurement across different radial positions, maintaining high measurement precision while reducing total measurement time.
Solution Approach 2:
Multiple read heads are combined to perform RRO measurement simultaneously at different radial positions. By merging the measurement capabilities of multiple heads, the system achieves both high precision (through multiple measurement points) and efficiency (through simultaneous operation).
2Productivity
If multiple read heads are used to simultaneously acquire RRO data to reduce measurement time, then productivity is improved, but device complexity increases
Solution Approach 1:
Multiple read heads, which are already present in TDMR systems for their primary reading function, are made multi-functional by also using them for simultaneous RRO measurement. This universal use of existing components improves productivity without adding dedicated measurement hardware, thereby limiting complexity increase.
3Measurement precision
If RRO measurement is performed at multiple radial positions to improve correction accuracy, then head position correction accuracy is improved, but the number of measurement operations increases
Solution Approach 1:
RRO measurement is performed in advance at multiple radial positions using multiple read heads before actual data writing. This preliminary simultaneous measurement establishes correction data for all radial positions upfront, improving correction accuracy while avoiding the need for sequential measurements during operation.
Data Source
AI summary
According to one embodiment, a magnetic disk device, includes a disk including a track including a plurality of servo sectors, a head including a write head which writes data to the disk and a plurality of read heads which read the data from the disk, and a controller configured to simultaneously acquire a plurality of pieces of correction data for repeatable runout of the disk by the read heads, acquire a first correction data and a second correction data based on the correction data, write the first correction data and the second correction data to the disk, and correct a position of the head based on the first correction data and the second correction data.