Multi-Actuator Shock Threshold Calibration for Disk Drive Data Integrity
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Solution Overview
Problem
Data storage devices face challenges in accurately positioning heads over disk tracks due to shock events, which can lead to off-track writing and data corruption, especially when multiple actuators are operating simultaneously, as existing systems lack effective methods to dynamically adjust shock thresholds based on actuator performance and operational modes.
Innovation Solution
The implementation of a shock sensor system that generates shock signals and adjusts shock thresholds for each actuator based on its performance and the operational mode of other actuators, using a control circuitry to inhibit writes during potential off-track conditions and calibrate sensitivity to prevent data corruption, while employing servo control systems to compensate for coupling disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single shock threshold is used for all actuators, then the device complexity is reduced, but the reliability of data writing is compromised when multiple actuators operate simultaneously
Solution Approach 1:
The patent divides the single shock threshold into multiple actuator-specific shock thresholds. Each actuator has its own calibrated threshold that reflects its individual performance characteristics and coupling effects. This segmentation allows the system to account for variations in actuator behavior while maintaining manageable complexity through automated calibration procedures.
Solution Approach 2:
The patent dynamically adjusts shock threshold parameters based on actuator operational mode (seeking vs. tracking) and actuator-specific calibration data. The control circuitry modifies the threshold values to optimize protection against off-track writing while accommodating the different performance characteristics of multiple actuators operating in different modes.
2Reliability
If shock threshold sensitivity is increased to detect all potential shock events, then data protection is improved, but false positives increase causing unnecessary write inhibitions
Solution Approach 1:
The patent applies different shock threshold sensitivity levels to different actuators based on their local performance characteristics and coupling effects. Each actuator receives a customized threshold that is calibrated to its specific operational environment, allowing high sensitivity where needed while maintaining productivity elsewhere through actuator-specific optimization.
Solution Approach 2:
The system uses feedback from actuator operational mode (seeking or tracking) and shock sensor data to dynamically adjust threshold application. The control circuitry monitors actuator behavior and only applies write inhibition when a shock event actually threatens data integrity, reducing false positives while maintaining protection when needed.
3Measurement precision
If actuator coupling effects are ignored, then the control system complexity is reduced, but positioning accuracy deteriorates during multi-actuator operations
Solution Approach 1:
The patent performs preliminary calibration of shock thresholds for each actuator before normal operation. During calibration, the system characterizes the coupling effects between actuators and stores this information for use during operational mode detection. This preliminary action captures the complex coupling behavior without requiring real-time computation during data writing operations.
Solution Approach 2:
The control system changes operational parameters (shock thresholds) based on detected actuator operational modes. When one actuator is seeking and another is tracking, the system adjusts the tracking actuator's shock threshold to account for coupling disturbances from the seeking actuator, thereby maintaining positioning accuracy through parameter adaptation rather than complex real-time control.
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 solution effectively prevents data corruption by dynamically adjusting shock thresholds, ensuring accurate head positioning and reliable data writing even during shock events, thereby enhancing the robustness and reliability of data storage operations in multi-actuator systems.
Implementation Method 1
control circuitry comprising a shock sensor configured to generate a shock signal
Implementation Method 2
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 3
A position error signal (PES) is generated by reading the servo bursts 14, wherein the PES represents a measured position of the head relative to a centerline of a target servo track
Data Source
AI summary
A data storage device is disclosed comprising a first actuator configured to actuate a first head over a first disk comprising a first plurality of tracks defined by first servo sectors, and a second actuator configured to actuate a second head over a second disk comprising a second plurality of tracks defined by second servo sectors. The first actuator is controlled based on the first servo sectors in order to first write data to the first disk, and the second actuator is controlled based on the second servo sectors in order to second write data to the second disk. The first writing is inhibited when a shock signal generated based on a shock sensor exceeds a first shock threshold, and the second writing is inhibited when the shock signal exceeds a second shock threshold different from the first shock threshold.