Disk Drive Touchdown Threshold Control via Slope Analysis
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Solution Overview
Problem
Conventional disk drives face challenges in accurately determining the dynamic fly height (DFH) setting for the head to achieve the target fly height over the disk, which affects the quality of write/read signals due to noisy touchdown signals and varying noise levels.
Innovation Solution
The implementation of a control circuitry that determines an operating touchdown threshold by evaluating the slope of the DFH setting relative to a TD threshold, adjusting it to detect head contact with minimal margin above noise, using a combination of bandpass filtering and counter mechanisms to refine the touchdown detection, and employing piezoelectric actuators for precise fly height control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed touchdown threshold is used for head contact detection, then the detection is simple, but the noise level varies and causes inaccurate touchdown detection
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed touchdown threshold to a dynamic threshold that adapts to varying noise levels. The system determines the threshold based on the slope of the DFH setting relative to the threshold, allowing the threshold to change dynamically according to operating conditions and noise characteristics, thereby maintaining accurate detection without requiring complex manual calibration.
Solution Approach 2:
The patent implements feedback by using the detected touchdown signal to adjust and refine the threshold determination process. The system continuously monitors the relationship between DFH setting and touchdown detection, using this feedback to optimize the threshold selection and ensure accurate head contact detection under varying noise conditions.
2Measurement precision
If the touchdown threshold is set low to detect minimal contact, then detection sensitivity is improved, but noise interference increases and causes false detections
Solution Approach 1:
The patent applies partial action by setting the touchdown threshold at an optimal point that is high enough to filter out noise but low enough to detect genuine head contact. The system determines this optimal threshold based on the slope characteristics of the DFH setting, using a portion of the available signal range to achieve both sensitivity and noise rejection.
Solution Approach 2:
The patent implements preliminary action by pre-determining the optimal touchdown threshold based on the relationship between DFH setting and noise characteristics before actual touchdown detection occurs. This preliminary threshold selection, based on slope analysis, prepares the system to accurately distinguish between noise and genuine contact events.
3Reliability
If dynamic fly height control is used to optimize signal quality, then write/read signal quality is improved, but the system complexity increases
Solution Approach 1:
The patent applies self-service by implementing a self-regulating fly height control system that automatically determines optimal DFH settings based on detected touchdown conditions. The system uses the touchdown detection mechanism to feedback-adjust the DFH setting, allowing the system to self-optimize signal quality without requiring external intervention or complex manual control mechanisms.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the DFH setting based on the determined touchdown threshold and slope characteristics. The system changes the fly height parameter in response to detected contact conditions, optimizing the signal quality parameter while managing system complexity through automated parameter adaptation.
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 ensures accurate and reliable detection of head touchdown, optimizing the DFH setting for improved signal quality by minimizing noise interference and maintaining precise fly height control, thereby enhancing the overall performance of disk drives.
Implementation Method 1
employing piezoelectric actuators for precise fly height control
Implementation Method 2
An air bearing forms between the head and the disk due to the disk rotating at high speeds
Data Source
AI summary
A disk drive is disclosed comprising a head actuated over a disk, and a dynamic fly height (DFH) actuator for controlling a fly height of the head over the disk in response to a DFH setting. A touchdown (TD) threshold is initialized, and the DFH setting that causes a TD signal to exceed the TD threshold is determined. The TD threshold is adjusted, and the DFH setting that causes the TD signal to exceed the adjusted TD threshold is determined. A slope of the DFH setting relative to the TD threshold is determined, and an operating TD threshold is determined in response to a change in the slope.