Magnetic Disk Servo Mark Detection Failure Handling
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Solution Overview
Problem
Magnetic disk devices face positioning accuracy issues due to failed detection of servo marks, which prevents demodulation of burst patterns and affects head positioning, especially when servo marks are defective.
Innovation Solution
The magnetic disk device employs a controller to perform a second demodulation on servo data without detecting the servo mark, specifically in cases where the first demodulation fails, allowing for continued demodulation of burst patterns and maintaining positioning accuracy by switching to short demodulation operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic disk device uses servo mark detection to determine demodulation timing, then positioning accuracy is maintained under normal conditions, but positioning accuracy deteriorates when servo marks are defective
Solution Approach 1:
The system performs preliminary detection of servo marks before demodulation, and prepares alternative demodulation timing methods in advance. When servo mark detection fails, the pre-prepared alternative timing determination method is immediately activated, ensuring continuous operation without positioning accuracy deterioration.
Solution Approach 2:
The system introduces an intermediary timing determination method that bridges the gap between servo mark detection and burst pattern demodulation. This intermediary mechanism uses alternative reference points or timing calculations to determine demodulation timing when servo marks are defective, preventing direct failure propagation.
2Measurement precision
If the magnetic disk device requires successful servo mark detection for burst pattern demodulation, then demodulation accuracy is high under normal conditions, but demodulation fails when servo marks are defective
Solution Approach 1:
The system changes the timing parameter for burst pattern demodulation based on servo mark detection results. When servo marks are defective, the system adjusts the demodulation timing parameter to use alternative reference points, maintaining demodulation accuracy despite the change in timing reference.
Solution Approach 2:
The demodulation timing determination is made dynamic rather than fixed. The system adapts the timing determination method based on real-time servo mark detection status, switching between normal timing (when marks are detectable) and alternative timing (when marks are defective), ensuring continuous reliable operation.
3Device complexity
If the magnetic disk device uses a fixed demodulation timing based on servo mark detection, then the control logic is simple, but the system cannot handle servo mark defects
Solution Approach 1:
The timing determination process is segmented into multiple independent methods: normal timing based on servo mark detection, and alternative timing based on other reference points. The system selects the appropriate segment based on detection results, maintaining simplicity in each segment while achieving robustness through segmentation.
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 enables the magnetic disk device to maintain positioning accuracy even when servo marks are not correctly detected, thereby reducing the deterioration of head positioning and ensuring reliable data access.
Implementation Method 1
a magnetic head performs write/read of data to/from the magnetic disk
Data Source
AI summary
According to an embodiment, a magnetic disk has a plurality of second servo sectors and a plurality of third servo sectors each arranged between two second servo sectors of the plurality of second servo sectors, in which the second and third servo sectors are arranged in a circumferential direction. A controller performs a first demodulation for detecting a servo mark and demodulating a burst pattern on the servo data in each second servo sector. The controller performs a second demodulation for demodulating the burst pattern without detecting the servo mark, on the servo data in each third servo sector. The controller performs the second demodulation on the servo data in a fourth servo sector which is one of the plurality of second servo sectors in a case where the detection of the servo mark fails when the first demodulation is performed on the servo data in the fourth servo sector.