Magnetic Disk Read Head Positioning for Skew Angle Compensation
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Solution Overview
Problem
In two-dimensional magnetic recording (TDMR)-type magnetic disk devices, the cross track separation between read heads changes with skew angles, requiring precise head positioning to accurately read data, which is challenging due to variations in cross track separation and skew angles across different regions of the disk.
Innovation Solution
The magnetic disk device employs a configuration with multiple read heads and a controller that positions the read heads and a middle portion at specific track centers based on cross track separation and skew angle measurements, adjusting the read heads' positions to minimize error rates and ensure accurate data reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple read heads are used in TDMR-type magnetic disk devices, then data reading capability is improved, but head positioning precision deteriorates due to varying cross track separation and skew angles across different disk regions
Solution Approach 1:
The patent divides the disk into multiple regions (first region and second region) with different cross track separation characteristics. For each region, a specific read head configuration is selected: the middle portion of read heads is positioned at the track center in the first region, while individual read heads are positioned at track centers in the second region. This regional differentiation allows optimal reading performance adapted to local cross track separation conditions, resolving the contradiction between using multiple read heads and maintaining positioning precision.
Solution Approach 2:
The patent implements dynamic head positioning by adjusting the position of read heads based on the disk region being accessed. The controller dynamically selects whether to position the middle portion or individual read heads at track centers depending on the cross track separation characteristics of the current region. This dynamic adaptation enables the system to maintain optimal positioning precision across different disk regions while utilizing multiple read heads for improved data reading capability.
2Measurement precision
If read heads are positioned to accommodate varying cross track separation, then reading accuracy is improved, but device complexity increases due to region-dependent positioning control
Solution Approach 1:
The patent implements region-specific positioning strategies where the control method differs between first and second regions. In the first region, the middle portion of read heads is positioned at track centers, while in the second region, individual read heads are positioned at track centers. This localized approach optimizes reading accuracy for each region's specific cross track separation characteristics while keeping the control logic relatively simple through clear regional differentiation.
3Reliability
If head positioning is optimized for specific disk regions, then error rate is reduced, but adaptability across different regions deteriorates
Solution Approach 1:
The patent reduces error rates by implementing region-optimized positioning: in the first region with smaller cross track separation, the middle portion of read heads is positioned at track centers, while in the second region with larger cross track separation, individual read heads are positioned at track centers. This localized optimization minimizes reading errors for each region's specific characteristics.
Solution Approach 2:
The system maintains cross-region adaptability through dynamic positioning control that automatically adjusts head positions based on the accessed disk region. The controller dynamically selects the appropriate positioning strategy (middle portion at center or individual heads at centers) depending on whether the first or second region is being accessed, enabling the system to adapt to different cross track separation conditions across regions while maintaining low error rates.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk, a head including a write head that writes data to the disk, and a first read head and a second read head that read data from the disk, and a controller that, in reading a first track of a first region of the disk, positions a middle portion of the first read head and the second read head at a first track center of the first track, and in reading a second track of a second region of the disk different from the first region, positions any one of the first read head and the second read head at a second track center of the second track.