Spindle Motor Speed Control via PES-Based Mode Switching
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Solution Overview
Problem
Existing disk drive servo control systems are affected by disturbances such as repeatable runout (RRO) and non-repeatable runout (NRRO), which can lead to positioning errors and reduced accuracy in head positioning due to spindle motor imperfections and environmental changes.
Innovation Solution
The spindle motor speed is dynamically controlled by toggling between AC and DC modes based on position error signals (PES), with the AC speed being disabled when excessive NRRO is detected to maintain stable head positioning, using band-pass filtering and variance thresholds to adjust the target speed and prevent transient disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC speed swinging is applied to the spindle motor, then head positioning accuracy is improved by compensating for RRO, but NRRO errors are magnified due to speed variations
Solution Approach 1:
The system dynamically switches between AC mode (with speed swinging for RRO compensation) and DC mode (without speed swinging) based on real-time PES monitoring. When PES exceeds a threshold indicating NRRO magnification, the system transitions from AC to DC mode, making the speed control adaptable to current operating conditions rather than fixed
Solution Approach 2:
The system uses position error signals (PES) as feedback to monitor head positioning accuracy in real-time. When PES exceeds a predetermined threshold, indicating that NRRO errors are being magnified, the feedback mechanism triggers a mode switch from AC to DC speed control, eliminating the harmful effect while preserving the beneficial RRO compensation when conditions are favorable
2Measurement precision
If AC mode is used continuously for RRO compensation, then positioning accuracy improves, but the system becomes vulnerable to NRRO magnification under certain conditions
Solution Approach 1:
The system transforms from a static AC-mode-only approach to a dynamic hybrid AC/DC mode system that adapts to changing conditions. The mode switching capability allows the system to maintain reliability by abandoning AC mode when it becomes harmful, while preserving its RRO compensation benefits when conditions are favorable
Solution Approach 2:
Real-time monitoring of position error signals provides feedback on system performance. When PES exceeds the predetermined threshold, the feedback triggers a protective mode switch to DC control, preventing NRRO magnification and maintaining system stability. This feedback mechanism ensures the system responds adaptively to deteriorating conditions
3Manufacturing precision
If DC mode is used without speed swinging, then NRRO errors are not magnified, but RRO compensation effectiveness is reduced
Solution Approach 1:
The system dynamically selects between AC and DC modes based on real-time performance monitoring. Rather than being fixed in DC mode with constant limited RRO compensation, the system transitions to AC mode when conditions favor RRO compensation effectiveness, making the trade-off adaptive rather than static
Data Source
AI summary
A data storage device is disclosed comprising a disk comprising servo data, a spindle motor configured to rotate the disk, and a head actuated over the disk. A position error signal (PES) is generated based on the servo data, and the head is actuated over the disk based on the PES. While swinging a speed of the spindle motor, the swinging is disabled based on the PES.