Disk Drive Touchdown Detection via Frequency Response Analysis
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Solution Overview
Problem
Existing disk drive technologies face challenges in accurately calibrating the fly height of the head over the disk surface due to contaminants, which can lead to incorrect positioning and signal quality issues during write/read operations, and existing methods struggle to differentiate between true touchdown events and contaminant-induced events during calibration.
Innovation Solution
A method involving a periodic fly height control signal applied to the fly height actuator, where the frequency response of a touchdown metric is measured to detect touchdown events, allowing discrimination between true head contact and contaminant contact by evaluating phase shifts relative to the control signal, thereby improving fly height calibration and identifying potential defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touchdown detection methods are used during fly height calibration, then the calibration process can be completed, but the system cannot reliably differentiate between true head contact and contaminant-induced contact events
Solution Approach 1:
The patent applies mechanical vibration by periodically oscillating the fly height actuator at a specific frequency during the touchdown calibration process. This vibration causes the head to periodically contact the disk surface, creating a measurable response signal. The frequency and amplitude of this mechanical oscillation are controlled to detect touchdown events while distinguishing them from contaminant contacts based on the characteristic response pattern at the oscillation frequency.
Solution Approach 2:
The system implements feedback by continuously monitoring the response signal from the fly height actuator and comparing it against expected patterns. The controller adjusts the fly height control signal based on the detected phase relationship between the control signal and the response signal, creating a closed-loop system that can identify true touchdown events versus contaminant contacts through their distinct feedback characteristics.
2Device complexity
If fly height calibration is performed without vibration-based detection, then the calibration process is simpler, but the accuracy of detecting true touchdown events is reduced due to contaminant interference
Solution Approach 1:
The patent introduces mechanical vibration of the fly height actuator at a controlled frequency during calibration. This vibration creates a distinctive periodic response when true touchdown occurs, allowing the system to differentiate it from contaminant contacts which do not produce the same frequency-specific response pattern, thereby improving detection accuracy.
Solution Approach 2:
The system employs periodic action by applying a periodic control signal to the fly height actuator during calibration. This periodic modulation of the fly height creates repeating touchdown cycles that generate a characteristic frequency response, enabling the controller to identify true touchdown events through their consistent periodic pattern rather than relying on simpler, less accurate single-event detection.
3Manufacturing precision
If the head is positioned closer to the disk surface during calibration, then fly height calibration precision improves, but the risk of contaminant contact increases
Solution Approach 1:
By applying mechanical vibration to the fly height actuator, the system creates a periodic contact pattern that produces a measurable frequency response. This allows the head to be positioned very close to the disk surface for precise calibration while the vibration-based detection method can distinguish between intentional periodic contact and unwanted contaminant contact, reducing the harmful effects of contamination.
Solution Approach 2:
The feedback mechanism monitors the response signal characteristics and can identify when contaminant contact occurs versus when the head is properly contacting the disk during periodic vibration. This feedback allows the system to maintain precise fly height calibration positioning while detecting and flagging contaminant events, preventing false calibration results.
Data Source
AI summary
A disk drive is disclosed comprising a head actuated over a disk, and a fly height actuator operable to control a fly height of the head over the disk. A periodic control signal is applied to the fly height actuator, a frequency response of a touchdown metric at a frequency of the periodic control signal is measured, and a touchdown event is detected in response to the frequency response of the touchdown metric.