Burst Correction Values for Disk Head Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing data storage devices face errors in writing servo sectors, particularly in servo bursts, leading to repeatable run-out (RRO) errors and track misregistration (TMR) during head positioning, due to imperfections in the servo writing process.
Innovation Solution
Generating and writing burst correction values at specific radial locations on the disk, which are then used to adjust the position error signal (PES) and reduce RRO errors by interpolating servo correction values based on these corrections, allowing precise head positioning over data tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If servo sectors are written using conventional servo writing processes, then data storage operations can be performed, but repeatable run-out errors and track misregistration occur due to writing imperfections
Solution Approach 1:
The patent applies preliminary action by pre-calculating and writing burst correction values to the disk during a calibration process before normal data storage operations. These correction values are stored in servo sectors and subsequently used to compensate for writing imperfections, thereby improving head positioning accuracy without requiring changes to the main servo writing process.
Solution Approach 2:
The patent implements feedback by measuring the actual head position using servo bursts, calculating correction values based on the measured position errors, and writing these correction values back to the disk. This closed-loop feedback mechanism continuously compensates for writing imperfections, resolving the contradiction between reliability and manufacturing precision.
2Reliability
If burst correction values are written at multiple radial locations, then RRO errors are reduced, but the complexity of the servo writing process increases
Solution Approach 1:
The patent applies segmentation by dividing the disk surface into multiple radial locations and writing separate burst correction values at each location. This segmentation allows the system to capture position errors specific to different radial positions, improving PES accuracy while managing process complexity through systematic organization of correction data.
Solution Approach 2:
The patent uses parameter changes by varying the radial location where burst correction values are written and measured. By changing this spatial parameter, the system captures position error characteristics at different points across the disk, enabling more accurate RRO compensation without fundamentally changing the servo writing process architecture.
3Measurement precision
If servo bursts are written with high precision, then head positioning accuracy improves, but the servo writing process becomes more difficult to implement
Solution Approach 1:
The patent introduces an intermediary element - the burst correction values - that mediates between the imperfect servo burst writing process and the required high precision head positioning. These correction values act as a compensating layer that improves measurement precision without requiring the physical servo bursts to be written with extremely high precision, thus maintaining ease of manufacture.
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by servo bursts. The head is positioned at a first radial location over the disk and a first burst correction value is generated by reading at least one of the servo bursts. The head is positioned at a second radial location over the disk and a second burst correction value is generated by reading at least one of the servo bursts. The head is positioned at a third radial location over the disk and the first burst correction value and the second burst correction value are written at the third radial location. The head is servoed over the disk by reading the first and second burst correction values.