Servo Frame Interval Correction for Disk Drive Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic disk drives experience positioning errors due to servo frame deviations from the center of rotation, leading to irregular intervals and increased seek time, which affects access times and drive performance.
Innovation Solution
A servo frame interval correction apparatus that detects and corrects estimated positions by calculating differentials between detected and reference time intervals, using a detection unit, acquiring unit, differential calculation unit, and correction unit to update servo frame intervals and correct positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic disk drive positioning control is used, then the magnetic head can be controlled based on equal-spaced servo frame intervals, but positioning errors accumulate gradually due to servo frame deviations from the center of rotation
Solution Approach 1:
The patent implements feedback by detecting the actual time interval between consecutive servo frames and comparing it with the reference time interval. The difference (deviation) is fed back to the control system, which then adjusts the position calculation accordingly. This continuous feedback loop ensures that positioning errors are corrected rather than accumulated, resolving the contradiction between maintaining equal-spaced interval assumptions and dealing with actual servo frame deviations.
Solution Approach 2:
The patent changes the parameter from a fixed reference time interval to a dynamic, actually measured time interval. By updating the time interval parameter based on real detection results and using this updated parameter in subsequent position calculations, the system adapts to the actual servo frame spacing. This parameter change allows the system to maintain positioning accuracy despite deviations from the ideal equal-spaced arrangement.
2Speed
If servo frames are detected at irregular intervals due to decentering, then the magnetic head traces an elliptic track, but seek velocity and seeking accuracy are reduced
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between time interval deviations and position corrections in a lookup table or pre-computed data structure. When servo frames are detected at irregular intervals, the system queries this pre-prepared data to obtain the appropriate correction, rather than performing complex real-time calculations. This allows the system to maintain high seeking accuracy even at high seek velocities, as the correction is applied instantly based on pre-computed relationships.
Solution Approach 2:
The patent replaces the mechanical assumption of equal-spaced servo frames with a digital correction system. Instead of relying on the physical geometry of the servo frame arrangement, the system uses digital signal processing to measure actual time intervals and applies computational corrections to the position calculations. This substitution of mechanical assumptions with digital correction mechanisms allows the system to maintain accuracy despite elliptic track geometry caused by decentering.
3Productivity
If the variation in servo frame detection time intervals is not corrected, then the control system assumes equal-spaced intervals, but positioning errors increase with higher seek velocities
Solution Approach 1:
The patent uses feedback to continuously monitor the actual time intervals between servo frame detections and adjust position calculations accordingly. By feeding back the measured time interval deviations and applying them as corrections to the position estimation, the system maintains positioning precision even during high-velocity seek operations. This feedback mechanism ensures that access time is not compromised by positioning errors, as corrections are applied in real-time during the seek operation.
Data Source
AI summary
One aspect of the embodiment utilizes a servo frame interval correction apparatus which includes a detection unit for detecting a first servo frame formed on said recording medium. The apparatus includes an acquiring unit acquiring a detection time interval between said first servo frame and a second servo frame detected subsequently to the first servo frame from a table storing a detection time interval between a specific servo frame and a servo frame detected subsequently to the specific servo frame. The apparatus includes a differential calculation unit calculating a differential between the detection time interval acquired by said acquiring unit and a reference time interval; and a correction unit correcting an estimated position of said second servo frame based on the differential calculated by said differential calculation unit.