Disk Drive Burst Metric Evaluation for Head Positioning
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Solution Overview
Problem
Current disk drive technologies face challenges in accurately positioning the head over servo tracks due to variations in servo bursts and tracks per inch (TPI), leading to inefficiencies in data access and writing operations.
Innovation Solution
The implementation of burst metrics, such as alpha, beta, and harmonic metrics, generated from reading amplitude and phase-based servo bursts, allows for the selection of an optimal servo tracks per inch (TPI) to improve head positioning accuracy and efficiency, using calibration servo tracks to determine the best TPI for writing servo sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional head positioning methods are used without burst metrics, then the system is simpler to implement, but head positioning accuracy deteriorates due to variations in servo bursts and tracks per inch
Solution Approach 1:
The patent applies preliminary action by performing burst metric evaluation and optimal servo TPI selection during the calibration phase before actual data operations. Calibration servo tracks are written with multiple servo TPI values, and burst metrics (alpha, beta, harmonic) are pre-calculated to determine the optimal TPI for each track radius, eliminating the need for real-time adjustments during data access
Solution Approach 2:
The patent applies parameter changes by introducing burst metrics (alpha metric, beta metric, harmonic metric) as new evaluation parameters to determine optimal servo TPI. These metrics quantify signal characteristics by reading calibration servo bursts at different radial positions and comparing amplitude ratios and harmonic content, enabling systematic optimization of head positioning accuracy across varying disk conditions
2Measurement precision
If calibration is performed for multiple servo TPI values, then optimal TPI selection improves positioning accuracy, but calibration time increases
Solution Approach 1:
The patent applies partial action by evaluating burst metrics at selectively chosen servo TPI values during calibration rather than exhaustively testing all possible TPI values. The system writes calibration servo tracks at a limited set of candidate TPI values and selects the optimal one based on burst metric evaluation, reducing calibration time while maintaining positioning accuracy
Solution Approach 2:
The patent performs calibration operations in advance during manufacturing or initialization, writing multiple calibration servo tracks with different servo TPI values and determining optimal TPI for each radial position before actual disk operations begin. This preliminary calibration eliminates time loss during normal data access operations
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 enhances the accuracy and efficiency of head positioning, reduces calibration time, and maintains signal quality by selecting the optimal servo TPI based on burst metrics, thereby improving data access and writing operations.
Implementation Method 1
a read element and a write element... at least one servo burst is read from the disk to generate a burst read signal
Data Source
AI summary
A disk drive is disclosed comprising a disk and a head actuated over the disk. A burst metric is generated in response to a burst read signal. The burst metric comprises at least one of an alpha metric comprising a ratio of a first burst amplitude of a first phased based servo burst measured at a first radial offset to a second burst amplitude of a second phased based servo burst measured at a second radial offset, a harmonic metric comprising a ratio of a first harmonic of the burst read signal as the head is moved radially over the disk to a higher harmonic of the burst read signal as the head is moved radially over the disk, and a spiral track crossing metric comprising a first and second interval each representing a partial duration of the read element crossing a spiral track.