HAMR Fly Height Compensation via Dual Temperature Models
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Data storage devices using heat-assisted magnetic recording (HAMR) face challenges in maintaining accurate fly height control due to laser-induced head protrusions, which affect the spacing between the head and the storage medium, leading to reduced field strength and accuracy in writing and reading data.
Innovation Solution
Implementing a dual temperature state model for fly height compensation, using a short-term model to track immediate laser-induced heating and a long-term model to account for prolonged heating effects, allowing for precise adjustment of the fly height actuator's power to maintain optimal spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single temperature state model is used for fly height compensation, then the response speed is fast, but the long-term thermal effects are not accurately tracked
Solution Approach 1:
The temperature state model is segmented into two distinct models: a short-term model with a first time constant for rapid response to immediate thermal changes, and a long-term model with a second time constant for tracking prolonged thermal effects. This segmentation allows the system to simultaneously capture both fast transient behavior and slow cumulative thermal drift, resolving the contradiction between response speed and tracking accuracy.
2Manufacturing precision
If laser power is increased to improve write quality, then data recording accuracy improves, but head protrusion increases reducing fly height control
Solution Approach 1:
The system implements feedback control by continuously monitoring the thermal state through the dual temperature models and adjusting the fly height actuator power accordingly. The compensation amount is dynamically calculated based on the predicted thermal expansion from both short-term and long-term models, allowing the system to maintain accurate fly height control even when laser power is increased for improved write quality.
3Measurement precision
If fly height is decreased to improve field strength, then write and read accuracy improves, but risk of head contact increases
Solution Approach 1:
The system performs preliminary thermal compensation by predicting the thermal expansion effect before it fully manifests. The dual temperature state models continuously estimate the thermal protrusion, and the fly height actuator is proactively adjusted in advance to counteract the expected thermal expansion, allowing the system to safely operate at lower fly heights for improved field strength without increasing head contact risk.
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 enhances the reliability and accuracy of data storage operations by effectively managing laser-induced protrusions, ensuring consistent and accurate data recording and retrieval in HAMR systems.
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
heat the non-volatile storage medium
Implementation Method 3
fly height actuators may include heaters which control fly height through thermal expansion
Implementation Method 4
piezoelectric (PZT) actuators which may deflect the head relative to the storage device when energized
Data Source
AI summary
Example systems, data storage devices, and methods to provide long-term spacing compensation for heat assisted magnetic recording are described. The data storage device includes a storage medium with data tracks and a head that can be positioned for reading and writing those tracks. The head includes a laser for heat assisted magnetic recording and a fly height actuator. Based on the operation of the laser, both a short-term fly height compensation parameter and a long-term fly height compensation parameter are determined based on different temperature state models. The operating power of the fly height actuator is determined, at least in part, based on the short-term and long-term height compensation parameters.