Hard Disk Drive Read Sensor Track Following Using Signal Asymmetry Metrics
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Solution Overview
Problem
Current sector servo schemes in hard disk drives are blind to disturbances between servo sectors and inaccuracies in data-track following, leading to read throughput loss due to the lack of effective mechanisms for monitoring and correcting signal asymmetry metrics during read-back operations.
Innovation Solution
A method and system that utilize signal asymmetry metrics monitored during read-back to correct and guide the position of a read sensor in hard disk drives, combining these metrics with position error signals to enhance track following, employing a servo circuit that estimates data signal asymmetry and integrates this information with position error weighting and logic to adjust the read sensor's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional sector servo schemes are used, then the system is simple to implement, but track following accuracy deteriorates due to blindness to disturbances and signal asymmetry
Solution Approach 1:
The patent implements feedback by monitoring signal asymmetry metrics during read-back operations and using this information to adjust the read sensor position. The servo circuit receives feedback signals containing asymmetry metrics and position error signals, processes them to determine optimal sensor position, and continuously adjusts tracking to compensate for disturbances between servo sectors.
Solution Approach 2:
The patent introduces signal asymmetry metrics as an intermediary parameter that mediates between the read sensor and the written track. These metrics serve as a bridge to detect track deviations and guide position corrections, enabling enhanced track following without requiring direct complex measurements of track position.
2Manufacturing precision
If signal asymmetry metrics are monitored during read back, then track following accuracy is improved, but read throughput may be affected due to additional processing
Solution Approach 1:
The patent performs preliminary action by monitoring signal asymmetry metrics during the read-back process itself, rather than requiring separate calibration or measurement steps. The asymmetry metrics are extracted and processed in real-time as data is being read, allowing track following corrections to be made without stopping the read operation or significantly delaying it.
Solution Approach 2:
The patent merges the track following correction function with the data read-back operation. The servo circuit combines position error signals with asymmetry metric extraction and processing, integrating multiple functions into a unified system that corrects track position while maintaining data retrieval operations.
3Reliability
If position error signals are used alone, then the system is straightforward, but it fails to correct inaccuracies in data-track following
Solution Approach 1:
The patent exploits signal asymmetry as a key indicator of track position deviations. By analyzing asymmetry metrics in the read-back signals, the system detects disturbances and track following inaccuracies that would otherwise be invisible to traditional symmetric servo schemes. This asymmetry-based detection enables reliable correction of track position to maintain data integrity.
Data Source
AI summary
A method, apparatus, and system are provided for implementing track following using signal asymmetry metrics monitored during read back in hard disk drives (HDDs). Signal asymmetry metrics monitored during read back are used together with a position error signal (PES) to correct and guide the position of a read sensor with respect to a written track in the HDD.