Dynamic Head Flying Height Control for Disk Drive Bump Detection
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Solution Overview
Problem
Existing hard disk devices face challenges in accurately detecting and avoiding media bumps during the manufacturing process, as a fixed head flying height can lead to either head deterioration or insufficient detection of minute bumps.
Innovation Solution
A method is implemented to dynamically control the head flying height by detecting contact with the disk, increasing the height when contact occurs, and decreasing it when contact is not detected, using a heater element and a magneto-resistive sensor to adjust the slider's position and prevent collisions with bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flying height of the head is set greater to avoid contact with large bumps, then head deterioration is prevented, but the gap between the magnetic disk and the head increases, causing minute bumps to be undetected
Solution Approach 1:
The patent implements dynamic adjustment of the head flying height during the bump detection process. The control unit continuously monitors for head-disk contact and adjusts the flying height in real-time, transitioning from a fixed height approach to a dynamic one that adapts to detected bump conditions, thereby resolving the contradiction between avoiding head contact and maintaining detection sensitivity
Solution Approach 2:
The patent changes the flying height parameter dynamically during the detection process. By adjusting this critical parameter based on real-time feedback from contact detection, the system optimizes the balance between head protection and detection accuracy, allowing the head to fly at different heights at different times during the scanning process
2Measurement precision
If the flying height of the head is fixed at a lower setting for accurate bump detection, then minute bumps can be detected, but the head contacts large bumps frequently, leading to head deterioration
Solution Approach 1:
The patent implements a feedback mechanism where the control unit monitors for head-disk contact events and uses this information to adjust the flying height. This closed-loop control allows the system to respond to actual contact conditions, preventing future contacts by raising the head when contact is detected, thus protecting the head while maintaining detection capability
Solution Approach 2:
The patent performs preliminary bump detection at a lower flying height to identify bump locations, then uses this information to adjust the flying height for subsequent scanning. This preliminary action allows the system to gather detection data first, then optimize the flying height to avoid head contact with detected bumps
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 reduces the number of collisions with bumps, prevents head deterioration, and allows for accurate detection of both large and small bumps by optimizing the gap between the disk and the head.
Implementation Method 1
using a heater element and a magneto-resistive sensor to adjust the slider's position
Implementation Method 2
using a heater element and a magneto-resistive sensor to adjust the slider's position
Data Source
AI summary
According to one embodiment, a head flying height control method includes detecting a contact of a head with a disk while floating the head from the disk and moving the head in a radial direction of the disk, increasing a flying height of the head after detecting the contact of the head with the disk, and decreasing the flying height of the head after a state where the contact of the head with the disk is not detected continues.