Magnetic Disk Head Positioning via Phase Correction
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Solution Overview
Problem
Magnetic disk devices face challenges in accurately positioning the magnetic head due to timing deviations in the burst demodulation window, leading to incorrect demodulation positions and reduced accuracy in positioning control, especially in short servo sectors where the burst demodulation window is likely to deviate from intended timing.
Innovation Solution
The magnetic disk device configures the burst pattern with a recording frequency ⅔ times the preamble frequency, allowing the controller to determine the burst demodulation window and perform sampling at the servo clock frequency, and corrects the demodulation position based on the phase information to distinguish between positional deviations and timing deviations, thereby improving positioning control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the burst demodulation window is used in short servo sectors, then the demodulation process can be simplified by skipping servo mark demodulation, but timing deviations occur causing incorrect demodulation positions and reduced positioning control accuracy
Solution Approach 1:
The patent changes the recording frequency parameter of the burst pattern to 1/L times the servo clock frequency, where L is a positive integer. This parameter modification ensures that the burst pattern completes an integer number of cycles within the demodulation window, eliminating timing deviations and enabling accurate positioning control while maintaining simplified demodulation processing in short servo sectors
2Measurement precision
If the burst pattern recording frequency is increased to match servo clock frequency, then timing accuracy improves, but the unwritable area capacity is reduced
Solution Approach 1:
The patent optimizes the burst pattern recording frequency to 1/L times the servo clock frequency, where L is a positive integer greater than 1. This parameter setting achieves the minimum necessary frequency for accurate timing measurement while maximizing the usable capacity of the unwritable area, balancing positioning accuracy with storage efficiency
Data Source
AI summary
According to an embodiment, a magnetic disk is provided with a servo sector in which a preamble and a burst pattern are recorded. A recording frequency of the preamble is different from an even multiple of a recording frequency of the burst pattern. A controller determines a demodulation period of the burst pattern while a magnetic head passes through the servo sector. The controller acquires a first phase of a demodulation signal of the burst pattern and acquires first position information of the magnetic head, by demodulating the burst pattern in the demodulation period. The controller corrects the first position information on the basis of the first phase. The controller executes positioning control of the magnetic head on the basis of second position information that is post-correction first position information.