Fly Height Actuator Calibration for Heat-Assisted Magnetic Recording
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Solution Overview
Problem
Conventional data storage devices face challenges in determining the appropriate fly height setting for the head in heat-assisted magnetic recording (HAMR) systems, as excessive laser power can lead to data erasure in adjacent tracks and insufficient power results in under-saturation of the magnetic media, while maintaining optimal recording reliability.
Innovation Solution
A calibration procedure is implemented to determine the optimal fly height actuator (FHA) setting based on calibrated write laser power, involving measurements at different laser power settings and generating a curve to adjust the FHA setting, ensuring a target fly height for both write and read operations, thereby compensating for the heating effect of the laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser power is increased to improve recording quality, then magnetic media saturation improves, but data erasure in adjacent tracks occurs
Solution Approach 1:
The patent applies parameter changes by adjusting the fly height based on the laser power setting. As laser power increases to improve magnetic saturation, the fly height is dynamically modified to compensate for thermal expansion and maintain appropriate spacing between the head and disk surface, preventing data erasure in adjacent tracks while preserving recording reliability.
2Reliability
If fly height is decreased to improve signal quality, then write/read signal quality improves, but head-disk contact risk increases
Solution Approach 1:
The patent implements dynamics by making the fly height adjustable and dependent on operating conditions, specifically laser power settings. Rather than using a fixed fly height, the system dynamically modifies the fly height to optimize signal quality while preventing head-disk contact, allowing the head to operate at optimal spacing under different recording conditions.
3Device complexity
If conventional fixed fly height is used to simplify control, then device complexity is reduced, but recording reliability under varying laser power deteriorates
Solution Approach 1:
The patent resolves this contradiction by implementing parameter changes that link fly height to laser power settings. The system maintains recording reliability under varying laser power by automatically adjusting fly height based on the active laser power level, ensuring optimal head-disk spacing without requiring complex manual intervention or overwhelming complexity.
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 ensures optimal recording reliability by maintaining a consistent fly height during write operations and preventing data erasure, while avoiding damage to write components by executing the calibration process on non-production disk drives and loading the results into production drives.
Implementation Method 1
heating the disk surface with a laser during write operations in order to decrease the coercivity of the magnetic medium
Implementation Method 2
heating the disk surface with a laser during write operations
Implementation Method 3
a heater which controls fly height through thermal expansion
Implementation Method 4
a piezoelectric (PZT) actuator
Data Source
AI summary
A data storage device is disclosed comprising a disk, a head comprising a laser, and a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting. A first fly height of the head is measured at a first laser power setting, and a second fly height of the head is measured at a second laser power. A FHA write setting is generated based on a calibrated write laser power, the first and second fly height measurements, and a first function representing a nominal FHA delta setting between a read touchdown FHA setting and a write touchdown FHA setting relative to a delta in a fly height of the head due to a corresponding change in laser power applied to the laser, where the FHA write setting is applied to the FHA during the write operation.