Disk Device Gap Measurement Using Third-Order Signal Component
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Solution Overview
Problem
Existing methods for measuring the gap change between a magnetic head and a recording medium in magnetic disk devices suffer from significant errors due to thermal relaxation, especially in long-term measurements, and require moving the magnetic head between tracks, increasing processing time and latency.
Innovation Solution
A disk device that records a gap measurement signal with high-frequency components on a disk-shaped recording medium and uses a magnetic head with a write head, read head, and heater, along with a controller that generates a reference signal and measures component amplitudes to adjust the gap between the recording medium and the magnetic head, minimizing the effect of thermal relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signals are recorded on two tracks to correct thermal relaxation, then measurement precision is improved, but processing time increases due to head movement between tracks
Solution Approach 1:
The patent extracts only the necessary information (third-order component amplitude) from the reproduced signal to correct thermal relaxation effects, eliminating the need to move the magnetic head between tracks and process signals from multiple tracks. This allows accurate gap measurement while maintaining the head in a single track position.
Solution Approach 2:
The patent changes the approach from using multiple tracks with different recording frequencies to using a single track and analyzing specific frequency components (third-order component) of the reproduced signal. This parameter change in the measurement method eliminates the need for track switching while maintaining correction capability.
2Manufacturing precision
If the gap between magnetic head and recording medium is reduced, then recording density is improved, but reliability deteriorates due to increased contact risk from gap change
Solution Approach 1:
The patent implements a feedback mechanism where the gap change is measured using the reproduced signal's third-order component amplitude, and this measurement is used to correct thermal relaxation effects. This allows continuous monitoring and adjustment of the gap to prevent contact while maintaining optimal recording density.
Solution Approach 2:
The patent performs preliminary measurement of gap change using the reproduced signal before actual recording operations. By measuring the gap change in advance and correcting for thermal relaxation effects, the system can prevent potential contact issues before they occur during recording.
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 solution allows for accurate and efficient measurement of gap changes with reduced thermal relaxation errors, enabling faster processing and maintaining high recording accuracy by using the third-order component amplitude of the reproduced signal for gap measurement.
Implementation Method 1
the gap can be reduced by causing part of the slider, the read head, and the write head to bulge toward the surface of the recording medium by means of the thermal actuator
Implementation Method 2
a magnetic head that records and reproduces data on the magnetic recording layer of the recording medium
Data Source
AI summary
According to one embodiment, a disk device includes a disk-shaped recording medium, a magnetic head including a write head, a read head, and a heater, and a controller including a reference signal generator outputting a reference signal having a constant voltage amplitude at the same frequency as a high-frequency component of a gap measurement signal recorded in the recording medium, a measurer measuring a component amplitude of a reproduced signal of the gap measurement signal and an amplitude of the reference signal, and a heater controller controlling a power value of heater power supplied to the heater based on the measured values of the component amplitude and the amplitude of the reference signal.