Magnetic Disk Fly Height Control for Surface Roughness
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Solution Overview
Problem
Magnetic disk devices face challenges in maintaining optimal fly height during data writing and reading, leading to writing quality issues due to surface roughness and variations in the magnetic medium, which can result in errors and reduced reliability.
Innovation Solution
A magnetic disk device with a controller circuit that dynamically adjusts the fly height based on the write location, employing two set values for writing and reading operations, and incorporating a backup recording method to verify data integrity and reliability by increasing the fly height in areas prone to errors, thereby maintaining high writing quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the fly height is fixed during writing and reading operations, then the device complexity is reduced, but the writing quality deteriorates due to surface roughness and medium variations
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed fly height to a dynamically adjustable fly height that changes based on the operational mode (seeking, writing, reading) and surface conditions. The controller dynamically switches between multiple fly height levels to optimize writing quality while maintaining acceptable device complexity through structured control logic.
Solution Approach 2:
The patent implements local quality by selecting different fly height values for different operational contexts and surface regions. The controller determines the appropriate fly height based on local surface roughness characteristics and operational requirements, allowing optimized writing parameters for each specific writing location rather than using a uniform fly height throughout.
2Adaptability or versatility
If the fly height is changed frequently during seeking operations, then the adaptability to surface variations is improved, but the reliability of data writing deteriorates due to potential instability
Solution Approach 1:
The patent applies preliminary action by performing DFH control during the seeking operation before the actual writing operation begins. The controller switches to a first fly height level during seeking to adapt to surface variations, then switches to a second, more stable fly height level before writing starts. This preliminary adjustment allows the system to accommodate surface variations while ensuring writing reliability is not compromised by frequent changes during the actual writing process.
Solution Approach 2:
The patent uses dynamics by implementing a multi-level fly height control system that dynamically switches between different fly height values based on the operational phase. During seeking, the system uses one fly height level for adaptability, while during writing, it switches to another level for stability and reliability, creating a dynamic control strategy that optimizes both adaptability and reliability at different times.
3Reliability
If the fly height is increased to compensate for surface roughness, then the reliability of data writing is improved, but the recording density deteriorates
Solution Approach 1:
The patent implements local quality by selectively increasing the fly height only when and where necessary to compensate for surface roughness, rather than uniformly increasing it across all operations. The controller determines based on surface conditions and operational mode whether to use a higher fly height for reliability or maintain a lower fly height for high recording density, allowing the system to optimize each parameter locally where needed.
Solution Approach 2:
The patent applies parameter changes by switching between multiple discrete fly height levels (first fly height level for seeking/adaptability, second fly height level for writing reliability) based on operational requirements. This parameter switching allows the system to optimize reliability when needed while maintaining high recording density during normal operations, resolving the contradiction between these two parameters through controlled parameter variation.
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 enhances data writing reliability by adapting fly height settings to surface roughness, preventing errors and ensuring high-quality data storage without significant reduction in recording density, and provides a backup mechanism to verify correct data writing, especially in system areas with frequent access.
Implementation Method 1
a magnetic head that writes data on and reads data from the magnetic disk
Implementation Method 2
The DFH function changes a voltage applied to a DFH element (a thermal actuator) included in the magnetic head
Data Source
AI summary
A magnetic disk device includes a magnetic head that writes data on and reads data from the magnetic disk, and a controller circuit. The controller circuit is configured to control a gap between the magnetic head and the magnetic disk, and select one of two or more gap values for the fly height, based on a write location in the magnetic disk of data to be written by the magnetic head.