Fly Height Actuator Calibration via Read Mode Touchdown Resistance
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Solution Overview
Problem
Conventional data storage devices face challenges in determining the appropriate dynamic fly height (DFH) setting for the head to ensure reliable data recording and retrieval, as existing methods may cause damage to write components due to thermal expansion during write operations in heat-assisted magnetic recording (HAMR) systems.
Innovation Solution
The solution involves using a touchdown sensor to estimate the write touchdown fly height actuator (FHA) setting by measuring resistance changes, allowing the head to maintain a target fly height without actual write mode touchdown, thereby avoiding component degradation. This is achieved through various techniques such as extrapolation, linear fitting, and calculating a delta between read and write mode resistances to determine the optimal FHA setting for both read and write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touchdown procedures are used to determine DFH setting, then the head contacts the disk to achieve target fly height, but write components may be damaged due to thermal expansion during HAMR write operations
Solution Approach 1:
The patent performs touchdown calibration in read mode before actual write operations, establishing the DFH setting in advance without exposing write components to the harmful thermal expansion conditions that would occur during write-mode touchdown procedures
Solution Approach 2:
The patent uses read mode as an intermediary state to perform the touchdown calibration, allowing the touchdown sensor to measure resistance changes and determine the correct DFH setting without the write coil being actively heated, thus protecting write components from damage
2Reliability
If actual write mode touchdown is performed to calibrate DFH, then accurate fly height setting is achieved, but thermal expansion during write operations causes component degradation
Solution Approach 1:
The calibration is performed in advance during read mode operations, establishing reliable DFH settings before write operations begin, thereby ensuring data recording reliability without subjecting components to repeated thermal stress that would reduce their lifespan
Solution Approach 2:
The patent creates a copy of the touchdown calibration process by performing it in read mode rather than write mode, obtaining the necessary calibration data without exposing components to the harmful thermal conditions of actual write operations
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 reliable data recording and retrieval by maintaining a consistent fly height, minimizing the risk of component damage and ensuring adequate signal-to-noise ratio, while avoiding the need for actual write mode touchdown procedures.
Implementation Method 1
measuring resistance changes
Implementation Method 2
a heater which controls fly height through thermal expansion
Implementation Method 3
heating the disk surface with a laser during write operations
Implementation Method 4
an actuator arm which is rotated about a pivot by a voice coil motor (VCM)
Data Source
AI summary
A data storage device is disclosed comprising a disk, a head comprising a touchdown sensor, and a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting. The data storage device is configured into a read mode, and while in the read mode, the FHA setting is adjusted until the head contacts the disk and a touchdown read mode resistance of the touchdown sensor is measured. The data storage device is configured into a write mode and the FHA setting is adjusted so the head is not contacting the disk. While in the write mode, a non-touchdown write mode resistance of the touchdown sensor is measured, and a write touchdown FHA setting that will cause the head to contact the disk while in the write mode is estimated based on the touchdown read mode resistance and the non-touchdown write mode resistance.