Servo Sector Compensation for Disk Drive Positioning
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Solution Overview
Problem
Existing disk drive systems face disturbances such as repeatable runout and 'written-in' errors in servo sectors due to eccentricity and environmental changes, which affect head positioning accuracy and require compensation to maintain performance over the life of the disk drive.
Innovation Solution
A method is introduced where compensation values for servo sectors are continuously updated using Position Error Signals (PES) generated during each revolution, allowing real-time correction of repeatable disturbances like repeatable runout and 'written-in' errors, enabling precise head positioning and tracking performance improvement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If compensation values are updated for each servo sector using PES signals, then tracking performance and positioning accuracy are improved, but manufacturing time and processing complexity increase
Solution Approach 1:
The patent divides the disk surface into multiple servo sectors, each with its own compensation value. By segmenting the compensation process into individual sector updates rather than processing the entire disk at once, the system can update compensation values incrementally during normal operation, reducing manufacturing time while maintaining positioning accuracy.
Solution Approach 2:
The patent applies compensation values to servo sectors before they are fully written or during the writing process. By performing preliminary compensation updates using PES signals generated during servo sector reading, the system prepares compensation data in advance, reducing the time needed for final positioning calibration during manufacturing.
2Reliability
If compensation values are updated in real-time during disk operation, then tracking performance improves, but system complexity and computational load increase
Solution Approach 1:
The patent uses Position Error Signals (PES) generated during normal servo sector reading to update compensation values in real-time. The PES provides feedback about head positioning errors, which is processed to adjust compensation values for subsequent servo sectors. This feedback mechanism improves tracking performance without requiring complex external calibration equipment.
Solution Approach 2:
The system updates its own compensation values using PES signals generated during normal operation. The servo control system performs self-calibration by processing its own positioning error signals, eliminating the need for separate complex calibration procedures or external intervention, thereby reducing overall system complexity.
3Manufacturing precision
If compensation is applied for repeatable disturbances, then positioning accuracy is maintained, but processing time and computational resources increase
Solution Approach 1:
The patent applies compensation values locally to individual servo sectors based on their specific positioning errors. Rather than processing the entire disk uniformly, the system updates compensation values only for the specific servo sector being read, using its PES signal. This localized approach maintains positioning accuracy while minimizing processing overhead and preserving data processing speed.
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 approach minimizes the time needed for manufacturing by updating compensation values on a servo sector basis, improving tracking performance and reducing the impact of repeatable disturbances, ensuring accurate head positioning and data access even under varying conditions.
Implementation Method 1
a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk
Implementation Method 2
The read signal from the first servo sector is processed to generate a position error signal
Data Source
AI summary
A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by servo sectors. The head is positioned over a first servo track, and a first position error signal (PES) by reading a first servo sector during a first revolution of the disk and in response to a first compensation value. A second compensation value is updated for a second servo sector based on the first PES during the first revolution of the disk. A second PES is generated by reading the second servo sector during the first revolution of the disk and in response to the updated second compensation value. The first compensation value is updated for the first servo sector based on the second PES during the first revolution of the disk. The head is actuated over the disk in response to the first PES and the second PES.