Disk Drive Runout Update via Servo Interval Temperature Compensation
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Solution Overview
Problem
Existing disk drive technologies face challenges in accurately measuring and updating disk-runout information due to external impacts, such as disk shifts, which affect the dynamic offset control function, especially when temperature changes influence servo-interval changes.
Innovation Solution
A disk drive system that calculates servo-interval changes considering temperature variations, detects disk shifts from these changes, and updates disk-runout information using an SGI-temperature table to compensate for temperature effects, ensuring accurate dynamic offset control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If disk runout is measured during manufacture and stored in memory, then the DOC function can operate with initial accuracy, but the disk-runout information becomes outdated when disk shift occurs due to external impacts
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors servo interval changes during operation and compares them against reference values. When deviations indicate disk shift, the system automatically updates the disk runout information stored in memory, ensuring the DOC function always uses current accurate data without requiring manual remeasurement.
Solution Approach 2:
The disk drive system performs self-diagnosis and self-updating of disk runout information by detecting servo interval changes and automatically calculating updated runout values. This eliminates the need for external intervention or disassembly to remeasure disk runout after disk shift occurs, allowing the system to maintain accuracy autonomously.
2Productivity
If servo-interval change is used to calculate disk runout, then the measurement can be performed during operation, but temperature changes also affect servo-interval change making the measurement inaccurate
Solution Approach 1:
The patent extracts and separates the temperature effect from the servo interval change by introducing a temperature compensation value. The system measures both servo interval change and temperature, then removes the temperature-related component to isolate the true disk runout information, enabling accurate measurement during operation despite thermal variations.
Solution Approach 2:
The system changes the parameter being measured from raw servo interval change to temperature-compensated servo interval change. By adjusting for temperature variations through compensation values stored in lookup tables or calculated algorithms, the system transforms the affected parameter into an accurate indicator of disk runout that reflects only mechanical displacement.
3Adaptability or versatility
If the magnetic head is positioned at different radial positions on the disk, then different tracks can be accessed, but the skew angle of the actuator changes requiring offset adjustment
Solution Approach 1:
The patent creates a universal disk runout compensation value that works across all radial positions and tracks on the disk. Instead of maintaining separate offset values for each track or radial position, the system uses a single updated runout parameter set that can be applied universally, simplifying the control mechanism while maintaining adaptability to all tracks.
Solution Approach 2:
The system performs preliminary updating of disk runout information by detecting servo interval changes and calculating compensation values before actual data read/write operations. This pre-computation allows the DOC function to be ready with accurate offset values whenever the magnetic head needs to access any track, eliminating the need for complex real-time calculations during data operations.
Data Source
AI summary
According to one embodiment, a disk drive has a disk, a CPU and a memory. The CPU measures servo intervals between the servo areas provided on the disk, and calculates changes of the servo intervals, which have resulted from a temperature change. The CPU detects a disk shift from the changes of the servo intervals. The CPU updates the disk-runout information stored in the memory, in accordance with the disk shift detected.