Magnetic Head Fly-Height Control for Disk Surface Bumps
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Solution Overview
Problem
Magnetic heads in hard disk drives (HDDs) face damage and performance degradation due to collisions with microscopic protrusions on the recording medium surface, leading to reduced fly height and slowed data processing.
Innovation Solution
Incorporation of a heat resistance sensor to detect and measure protrusions, allowing for the setting of recording inhibited tracks and adjusting the magnetic head's flying height to avoid collisions, thereby improving recording density and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gap between the magnetic head and recording medium is reduced to improve recording density, then recording density is improved, but the magnetic head may collide with microscopic protrusions causing damage
Solution Approach 1:
The system performs preliminary detection of bump locations and heights before normal recording operations. The controller stores bump information and uses it to adjust the magnetic head's flying height or skip affected tracks, preventing collisions before they occur. This advance preparation resolves the contradiction by enabling safe operation at reduced gaps.
Solution Approach 2:
The magnetic head's flying height is dynamically adjusted based on detected bump characteristics. The controller modifies the gap distance in real-time or pre-configured settings based on stored bump data, allowing the system to maintain optimal recording density while adapting to surface irregularities, thus preventing collisions.
2Reliability
If the magnetic head flies higher to avoid collisions with bumps, then collision risk is reduced, but the amount of fly increases causing slower seek operations
Solution Approach 1:
Instead of uniformly increasing the flying height across all tracks, the system applies localized adjustments only to tracks or sectors containing bumps. The controller uses stored bump location data to selectively modify the magnetic head's flight path, maintaining normal flying height in safe zones and increasing height only where necessary, thus minimizing impact on seek performance.
Solution Approach 2:
When bumps are detected in the seek path, the controller skips those specific tracks or sectors by adjusting the flying height temporarily during the seek operation. This allows the magnetic head to quickly bypass problematic areas without maintaining an elevated flight path throughout the entire operation, preserving seek speed while avoiding collisions.
3Reliability
If multiple tracks are inhibited due to bumps, then magnetic head safety is improved, but recording capacity and data processing speed are reduced
Solution Approach 1:
The system applies recording inhibition locally only to specific tracks or sectors where bumps are detected, rather than inhibiting entire surfaces or large regions. The controller uses precise bump location data to target only the necessary areas, minimizing the impact on overall recording capacity and data processing speed while still protecting the magnetic head.
Solution Approach 2:
The system performs preliminary detection and mapping of bump locations before recording operations begin. By storing this information in advance and using it to selectively inhibit only affected tracks, the system avoids unnecessary recording inhibitions, thereby maintaining higher data processing speeds while still ensuring magnetic head safety.
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 effectively reduces the number of recording inhibit tracks by up to 60-75% and enhances data processing speed by minimizing collisions with protrusions, maintaining recording capacity and quality.
Implementation Method 1
incorporation of a heat resistance sensor to detect and measure protrusions
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a rotatable disk-shaped recording medium including a plurality of concentric recording tracks, a magnetic head including a write element which writes data to the recording tracks, a heating element, and a sensor which detects a surface condition of the recording medium, and a controller including an inspection circuit which detects, based on an sensor output of the sensor, presence or absence of a bump on a surface of the recording medium, a height and a width of the bump, and a memory which records the detected height and width of the bump.