Disk Drive Fly Height Control Using Temperature-Sensitive Sensor
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Solution Overview
Problem
Conventional disk drive head positioning systems face challenges in accurately maintaining fly height over varying disk topography, particularly due to magnetic property variations and clamp sputter shadow effects, which affect signal quality and measurement accuracy.
Innovation Solution
A temperature-sensitive fly height sensor (TSS) is used in conjunction with a fly height actuator and a feed-forward controller to generate a conversion function that converts fly height signals into corresponding fly height measurements, enabling precise fly height control and adaptation to disk topography variations, thereby improving signal quality and measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetoresistive heads with fly height actuators are used, then fly height control is achieved, but measurement accuracy deteriorates due to magnetic property variations and clamp sputter shadow effects
Solution Approach 1:
The patent replaces the magnetic-based measurement system with a temperature-sensitive resistor-based system. Instead of using magnetic property variations to measure fly height, the invention uses the temperature coefficient of resistance of a resistor to detect fly height changes, eliminating the harmful magnetic interference effects.
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to measure fly height. The temperature-sensitive resistor converts fly height changes into temperature-related resistance changes, providing a measurement path that is independent of magnetic property variations and clamp sputter shadow effects.
2Measurement precision
If feed-forward control is implemented to compensate for disk topography, then fly height control accuracy improves, but device complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing compensation values in a lookup table during system initialization or calibration. The feed-forward controller retrieves pre-computed compensation values based on disk radius and position, avoiding the need for complex real-time calculations and reducing computational complexity during operation.
Solution Approach 2:
The patent applies dynamics by making the control system adaptive to varying operating conditions. The feed-forward controller dynamically adjusts compensation values based on real-time detection of disk topography and magnetic property variations, allowing the system to optimize performance across different radial positions and operational states.
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
The TSS-based system enhances fly height control accuracy and signal quality by minimizing errors and residual amplitudes, providing improved head positioning and data read/write performance across the disk radius, even in areas with magnetic property variations.
Implementation Method 1
a heater which controls fly height through thermal expansion
Implementation Method 2
a piezoelectric (PZT) actuator
Data Source
AI summary
A disk drive is disclosed comprising a head actuated over a disk, wherein the head comprises a fly height actuator (FHA) operable to actuate the head vertically over the disk. The head further comprises a temperature sensitive fly height sensor (TSS) operable to generate a fly height signal (FHS) representing a fly height of the head over the disk. An FHA actuation curve is measured for the FHA, and a conversion function is configured based on the FHA actuation curve, wherein the conversion function is operable to convert the FHS in first units (e.g., volts) into a corresponding fly height (FH) of the head in second units (e.g., nm).