Dynamic Track Trajectories for Data Storage Head Positioning
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Solution Overview
Problem
Existing data storage devices face challenges in accurately positioning heads over disk tracks due to vibrations and defects, leading to deviations from ideal centerlines and adjacent track interference, which affect signal-to-noise ratio and data recovery.
Innovation Solution
The implementation of a servo control system that generates dynamic read and write track trajectories based on position error signals (PES) to compensate for deviations, using half or average PES values to adjust track centerlines and reduce interference between adjacent tracks, and incorporating repeatable runout compensation to maintain data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional fixed track centerlines are used for head positioning, then the servo control system is simple to implement, but head positioning accuracy deteriorates due to vibrations and defects causing deviations from ideal centerlines
Solution Approach 1:
The patent applies dynamics by transitioning from fixed static track centerlines to dynamic track trajectories. The track trajectory is generated by filtering position error signals (PES) using a low-pass filter, allowing the trajectory to adapt dynamically to vibrations and defects while maintaining simplicity through automated filtering processes.
Solution Approach 2:
The patent implements feedback by using position error signals (PES) read during write operations to generate and update track trajectories. The PES values are filtered and applied to adjust subsequent write and read operations, creating a closed-loop system that continuously improves positioning accuracy without increasing overall system complexity.
2Measurement precision
If dynamic track trajectories are generated using PES values to compensate for deviations, then head positioning accuracy is improved, but adjacent track interference increases due to trajectory adjustments
Solution Approach 1:
The patent applies local quality by differentiating between write track trajectories and read track trajectories. Write trajectories use full PES values to compensate for deviations, while read trajectories use filtered PES values to reduce interference. This localized differentiation optimizes each operation's trajectory quality without causing harmful interference.
Solution Approach 2:
The patent changes the parameter of PES value application by using different weighting factors for write and read operations. Write operations use unfiltered PES values for maximum compensation, while read operations use low-pass filtered PES values to smooth out high-frequency variations that cause adjacent track interference, thus optimizing both operations independently.
3Object-generated harmful factors
If low-pass filtering is applied to PES values to reduce high-frequency variations, then adjacent track interference is reduced, but response time to correct positioning errors increases
Solution Approach 1:
The patent applies partial action by selectively filtering PES values based on the operation type. Read operations use low-pass filtered PES values to reduce interference, while write operations use unfiltered PES values for immediate correction. This partial application of filtering maintains fast response where needed while reducing interference where appropriate.
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 data storage accuracy by improving signal-to-noise ratio and ensuring successful data recovery by dynamically adjusting track trajectories in real-time, effectively mitigating the impact of vibrations and defects.
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)
Implementation Method 2
The servo sectors comprise groups of servo bursts 14 (e.g., N and Q servo bursts), which are recorded with a predetermined phase relative to one another and relative to the servo track centerlines. The phase based servo bursts 14 provide fine head position information used for centerline tracking
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, including consecutive data tracks N−1, N, and N+1. Data is written to data track N using a position error signal (PES) generated by reading the servo data, and a read track trajectory for data track N is generated based on the PES of the write. Data is read from data track N based on the read track trajectory for data track N.