Flying Height Measurement Using Dedicated Servo Fields
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Solution Overview
Problem
Existing flying height measurement techniques in disk drives are inadequate for accurately measuring the flying height of a head over specific tracks and radial positions on the disk surface, leading to potential damage and errors due to uneven surfaces and varying disk speeds.
Innovation Solution
Incorporating dedicated flying height fields within servo sectors on the disk, allowing for real-time measurement of the flying height using read back signals from these fields, which include fundamental and third harmonic frequency data, and employing a system with a frequency detection module, qualifier module, and averaging module to calculate precise flying height values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated flying height measurement tracks are used, then flying height can be measured, but the measurement is not accurate for specific tracks and radial positions due to uneven disk surfaces and varying disk speeds
Solution Approach 1:
The patent applies local quality by incorporating dedicated flying height fields (FH fields) directly into servo sectors at specific radial positions on the disk. This allows the measurement system to account for local variations in disk surface and speed at each radial position, rather than using a single dedicated track that assumes uniform conditions across the entire disk. Each FH field provides localized measurement data that reflects the actual conditions at that specific location.
Solution Approach 2:
The patent segments the disk surface into multiple radial positions, each with its own servo sector containing FH fields. This segmentation allows independent measurement and optimization of flying height at each radial position, accommodating the varying conditions (surface unevenness, speed variations) that exist at different locations on the disk.
2Reliability
If flying height is increased to prevent head-disk contact, then head damage is prevented, but magnetic field strength decreases affecting read/write accuracy
Solution Approach 1:
The patent implements feedback by continuously measuring flying height at each radial position using FH fields and using this information to adjust the operating parameters. The system can detect when the head is too high or too low and make real-time adjustments to maintain optimal flying height, ensuring both head safety and read/write accuracy are maintained throughout the disk's operation.
Solution Approach 2:
The patent applies dynamics by making the flying height adjustment adaptive rather than static. The system continuously monitors actual flying height conditions at each radial position and dynamically adjusts the head position or operating parameters to maintain optimal performance, rather than using a fixed flying height that may be inappropriate for varying local conditions.
3Measurement precision
If flying height is decreased to improve magnetic field strength, then read/write accuracy improves, but head-disk contact risk increases
Solution Approach 1:
The feedback mechanism continuously monitors flying height and provides real-time information about the head's proximity to the disk surface. This allows the system to adjust operating parameters dynamically, maintaining low enough flying height for accurate read/write operations while preventing contact through continuous monitoring and adaptive control.
Solution Approach 2:
The system dynamically adjusts flying height based on real-time conditions at each radial position. Rather than using a fixed low flying height that risks contact, the system adapts the height to the specific local conditions, maintaining optimal accuracy while preventing head-disk contact through continuous adjustment.
4Measurement precision
If multiple FH fields are read during disk rotation, then accurate flying height measurement is achieved, but measurement time increases
Solution Approach 1:
The patent applies continuity of useful action by integrating FH field reading into the normal disk operation. The head reads FH fields during the same rotation cycle used for data operations, rather than requiring separate measurement passes. This continuous reading approach maintains measurement accuracy while minimizing additional time loss by utilizing existing operational time.
Solution Approach 2:
The FH fields serve multiple functions: they provide flying height measurement data while being read during normal data operations. This multi-functionality allows the measurement system to operate simultaneously with data read/write operations, reducing the need for separate measurement cycles and minimizing time loss.
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
This approach enables accurate and precise flying height measurement at any radial position and track, improving head positioning and reducing the risk of damage by providing real-time, accurate data for maintaining optimal flying height.
Implementation Method 1
a head configured to generate a read back signal based on the predetermined pattern in the first flying height field
Implementation Method 2
detecting magnitudes of fundamental frequencies and third harmonic frequencies of the read back signals corresponding to each of the flying height fields
Data Source
AI summary
Some of the embodiments of the present disclosure provide a disk drive system comprising a disk drive system comprising a disk having a track upon a surface of the disk, the track including a first data-storing sector and a second data storing sector, and a servo sector located between the first data-storing sector and the second data-storing sector, the servo sector including a first flying height (FH) field having a predetermined pattern. Other embodiments are also described and claimed.