Fly Height Actuator Calibration for Multi-Head Data Storage Devices
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Solution Overview
Problem
Conventional data storage devices face challenges in efficiently calibrating fly height actuators for multiple heads across disk surfaces, especially in changing environmental conditions and head tribology, which affects write/read signal quality and requires frequent recalibration.
Innovation Solution
Implementing a fly height calibration process that utilizes multiple calibration patterns on each disk surface, allowing for simultaneous calibration of all heads during a single disk revolution, using a control circuitry to read and adjust fly height patterns across multiple heads, and incorporating different patterns to compensate for thermal decay and settle intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration processes are used for multiple heads, then each head must be calibrated separately over multiple revolutions, but this results in excessive calibration time and reduced productivity
Solution Approach 1:
The patent combines the calibration processes for multiple heads into a single revolution by reading calibration patterns from multiple disk surfaces simultaneously. The control circuitry coordinates multiple heads to read their respective calibration patterns during one disk revolution, eliminating the need for sequential multi-revolution calibration and significantly reducing calibration time while maintaining accuracy
Solution Approach 2:
The patent positions all heads at predetermined calibration track locations before the disk rotation begins. By pre-positioning heads at the correct radial locations for their respective disk surfaces, the system ensures that all calibration readings occur during a single revolution without requiring intermediate seeking operations, thus maximizing calibration efficiency
2Reliability
If fly height calibration is performed frequently to compensate for environmental changes and head tribology, then signal quality is maintained, but operational time is reduced due to frequent recalibration interruptions
Solution Approach 1:
The patent uses multiple calibration patterns with different characteristics (e.g., different radial positions, different pattern densities) on different disk surfaces to capture various operational conditions. By calibrating against these diverse patterns during normal operation, the system adapts to environmental changes and tribology effects without requiring complete recalibration, thus maintaining signal quality while minimizing operational interruptions
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 expedites the fly height actuator calibration process, ensuring consistent signal quality by calibrating all heads quickly and efficiently, reducing the need for frequent recalibrations and improving operational stability across varying conditions.
Implementation Method 1
a heater which controls fly height through thermal expansion
Implementation Method 2
a piezoelectric (PZT) actuator
Data Source
AI summary
A data storage device is disclosed comprising a first head actuated radially over a first disk surface, and a second head actuated radially over a second disk surface. A seek operation seeks the first head to a first fly height calibration track and seeks the second head to a second fly height calibration track. During a revolution of the first and second disk surfaces the first head is used to read the first fly height calibration track in order to calibrate a first fly height actuator for the first head, and after switching from the first head to the second head, the second head is used to read the second fly height calibration track in order to calibrate a second fly height actuator for the second head.