Magnetic Disk Servo Writing with Adaptive Sync Mark Frequency
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Solution Overview
Problem
Manufacturing variations in magnetic disk devices result in inconsistent data write widths of magnetic heads, leading to reduced read areas and signal components of sync marks, which can cause errors in servo pattern tracking accuracy.
Innovation Solution
A controller writes adjustment patterns with varying frequencies and detects the number of sync marks in the read signal to select an optimal frequency for writing servo patterns, ensuring accurate tracking by adjusting the seek speed and pattern frequency based on detected signal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a narrow spiral pattern is written due to manufacturing variations, then the data write width becomes smaller, but the read area of the magnetic head becomes smaller and the signal component of the sync mark becomes smaller, causing errors in tracking
Solution Approach 1:
The patent applies dynamics by making the seek speed variable rather than constant. The controller dynamically adjusts the seek speed based on the detected number of sync marks. When the read area is small and sync mark signals are weak, the system changes the motion parameters (seek speed) to compensate for the reduced signal strength, ensuring reliable tracking despite manufacturing variations in magnetic head write width.
Solution Approach 2:
The patent implements feedback by detecting the number of sync marks in the read signal and using this information to adjust the seek speed. The controller continuously monitors the signal quality (number of detected sync marks) and modifies the seeking operation accordingly. This closed-loop control ensures that tracking accuracy is maintained even when manufacturing variations cause narrow spiral patterns and reduced read areas.
2Productivity
If the seek speed is increased to improve productivity, then the writing process becomes faster, but the accuracy of detecting sync marks and tracking spiral patterns deteriorates
Solution Approach 1:
The patent applies dynamics by making the seek speed variable rather than constant. The controller dynamically adjusts the seek speed based on the detected number of sync marks. When the read area is small and sync mark signals are weak, the system changes the motion parameters (seek speed) to compensate for the reduced signal strength, ensuring reliable tracking despite manufacturing variations in magnetic head write width.
Solution Approach 2:
The patent changes the operational parameter (seek speed) based on detected conditions. Instead of using a fixed seek speed, the system adjusts this parameter dynamically according to the number of sync marks detected. This parameter adaptation allows the system to optimize between speed and accuracy by slowing down when signal quality is poor and maintaining higher speeds when conditions are favorable.
3Ease of manufacture
If the magnetic head write width varies due to manufacturing variations, then some heads write narrow patterns reducing read area, but changing each head's characteristics increases device complexity
Solution Approach 1:
The patent applies universality by using a single controller that performs multiple functions: it manages all magnetic heads, detects sync marks from any head's read signal, and adjusts seek operations for the entire system. This unified approach handles manufacturing variations across different heads without requiring complex individual calibration mechanisms for each head, maintaining ease of manufacture while compensating for variations through a centralized adaptive control system.
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 method ensures accurate detection of sync marks and reduces errors in servo pattern writing, maintaining high accuracy and consistency across different seek positions on the magnetic disk.
Implementation Method 1
reads each of the written adjustment patterns by each of the magnetic heads, and detects the number of signal components of the sync mark included in the read signal of each of the magnetic heads
Implementation Method 2
writes a plurality of adjustment patterns including a sync mark in each predetermined cycle with different frequencies, to each of the magnetic disks by each of the magnetic heads
Data Source
AI summary
According to one embodiment, a magnetic disk device including a controller. The controller writes adjustment patterns, reads the written adjustment patterns, and detects the number of signal components of the sync mark included in the read signal, selects a frequency of an adjustment pattern from which the detected number larger than or equal to a threshold value is obtained, among the read adjustment patterns, as a write frequency of each of magnetic heads, writes spiral patterns including the sync mark in each predetermined cycle with the same frequency as each of the selected write frequencies, and writes a servo pattern, while tracking each of the written spiral patterns.