Disk Drive Overlapping Servo Zones for Seamless Zone Crossing
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Solution Overview
Problem
The existing zoned servo sector format in disk drives can lose synchronization during seek operations when crossing servo zone boundaries due to incorrect adjustments in servo control parameters, leading to potential loss of disk drive synchronization.
Innovation Solution
The implementation of overlapping, zoned servo sectors with adjustable servo parameters and a timing control loop that adjusts the servo gate and sync window during transitions between servo zones, ensuring seamless head positioning and data access across varying servo data rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If zoned servo sectors with varying data rates are used to improve disk capacity, then servo sector area is reduced and disk drive capacity is enhanced, but synchronization is lost during seek operations when crossing servo zone boundaries
Solution Approach 1:
The patent applies preliminary action by creating an overlapping transition zone before the actual zone boundary is reached. The first servo zone extends beyond its nominal boundary into a transition zone, and the second servo zone similarly extends into this transition zone. This preliminary extension allows the system to prepare for zone crossing by maintaining servo information from both zones in the transition area, preventing synchronization loss before it occurs.
Solution Approach 2:
The transition zone acts as an intermediary region between the first and second servo zones. It contains servo information from both zones, serving as a buffer that mediates the transition. When the head crosses from one zone to another, the transition zone provides continuous valid servo information from both zones, preventing synchronization loss and allowing smooth parameter transitions.
2Measurement precision
If servo control parameters are adjusted during zone transitions, then head positioning accuracy is maintained across zones, but synchronization can be lost due to incorrect adjustments
Solution Approach 1:
The patent implements feedback by continuously monitoring the head position and determining when the head is within the transition zone. Based on this feedback, the system selectively applies servo information from the first or second zone and adjusts servo control parameters accordingly. This closed-loop feedback ensures that parameter adjustments are made at the appropriate times, maintaining positioning accuracy while preventing synchronization loss.
Solution Approach 2:
The system dynamically switches between using servo information from the first zone and the second zone based on head position. The servo control parameters are dynamically adjusted as the head moves through the transition zone. This dynamic adaptation allows the system to maintain optimal head positioning accuracy while crossing zone boundaries, preventing synchronization issues that would occur with static parameter settings.
3Productivity
If the timing control loop is synchronized to varying data rates in different zones, then data access efficiency is improved, but synchronization is lost when the timing adjustments are incorrect
Solution Approach 1:
The timing control loop is prepared for rate changes in advance by having the transition zone contain servo information from both zones. When entering the transition zone, the system can preliminarily adjust the timing control loop parameters based on which zone is being left and which is being entered, ensuring smooth transitions without synchronization loss and maintaining data access efficiency.
Data Source
AI summary
A disk drive is disclosed comprising a head actuated over a disk, the disk comprising a plurality of servo sectors defining a plurality of servo tracks, wherein the servo tracks form a plurality of servo zones. A servo data rate of servo sectors in a first servo zone is different than a servo data rate of servo sectors in a second servo zone. A boundary of a first servo zone overlaps with a boundary of a second servo zone over a transition zone. The servo sectors of the first servo zone are interleaved with the servo sectors of the second servo zone within the transition zone. At least one servo parameter is adjusted when the head is over the transition zone in order to transition between the first servo zone and the second servo zone.