Dual Read Head Magnetic Disk Positioning via Radial Signal Differential
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Solution Overview
Problem
Magnetic disk drives face challenges in accurately reading data due to non-linearity and mechanical properties causing data misalignment, leading to decreased signal-to-noise ratios when vibrations affect servo processing, necessitating the development of a system that can effectively read and track data written off-target positions.
Innovation Solution
A magnetic disk drive configuration with multiple read heads and a controller that positions the heads based on signals from both read heads, one positioned at a reference point and the other separated radially, to improve tracking accuracy and SNR by adjusting the radial position of the read heads based on the read signals from each head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single read head is positioned at the target position, then the device structure is simple, but the signal-to-noise ratio decreases when data is written off-target due to vibrations or mechanical non-linearity
Solution Approach 1:
The read function is segmented into multiple read heads positioned at different radial locations (first read head at reference position, second read head at separated radial position). This segmentation allows the system to read data from multiple positions simultaneously, enabling the controller to determine the actual written position and correct positioning errors, thereby improving data reading reliability without excessive complexity
Solution Approach 2:
The controller acts as an intermediary that receives signals from multiple read heads, processes the information to determine the actual written position, and calculates correction amounts. This intermediary processing enables the system to compensate for vibrations and mechanical non-linearity by using the differential information from multiple read heads to reconstruct the accurate data position
2Measurement precision
If the read head position is fixed at the target position, then the positioning system is simple, but tracking accuracy decreases when data is written off-target
Solution Approach 1:
The system transitions from a static fixed-position read head to a dynamic positioning system where the controller actively adjusts the read head position based on real-time feedback from multiple read heads. The controller calculates correction amounts based on signal differences and dynamically repositions the read head to track the actual written position, improving measurement precision while managing complexity through intelligent control
Solution Approach 2:
The system implements feedback by continuously monitoring signals from the first and second read heads, comparing their outputs to determine position deviations, and using this information to correct the read head position. This closed-loop feedback mechanism enables precise tracking of off-target written data while maintaining manageable system complexity through automated correction
3Reliability
If multiple read heads are used to read off-target data, then the signal-to-noise ratio improves, but the device complexity increases
Solution Approach 1:
The reading function is segmented into multiple read heads positioned at different radial locations, with the first read head at a reference position and the second read head at a separated radial position. This segmentation enables the system to read data from multiple positions simultaneously, improving the signal-to-noise ratio by providing redundant reading paths while keeping the number of read heads manageable
Solution Approach 2:
The signals from multiple read heads are merged and processed by the controller to determine the actual written position and calculate correction amounts. By combining the information from the first and second read heads, the system achieves improved signal-to-noise ratio through signal diversity while managing device complexity through unified processing in the controller
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk including a plurality of servo data items, a head including a write head which writes data to the disk, and a first read head and a second read head which read data from the disk, and a controller configured to position the head based on a first signal in which write data positioned between the servo data items of the disk is read by the first read head, and a second signal in which the write data is read by the second read head separated from the first read head in a radial direction of the disk.