Embedded Contact Sensor Flying Height Control in Hard Disk Drives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current hard-disk drive (HDD) systems lack a mechanism for continuous flying height monitoring and control during operation, relying on pre-calculated corrections for temperature and pressure changes, which can lead to inefficient head-disk interface management and potential contact issues.
Innovation Solution
The implementation of an embedded contact sensor (ECS) to characterize the microwaviness of the magnetic-recording disk at various flying heights, using disk topography data for active flying height control through thermal flying height control (TFC) and interface voltage control (IVC) systems, enabling continuous monitoring and feedback loop adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-calculated corrections to TFC settings are applied due to temperature or pressure changes, then the system can maintain basic flying height control, but continuous flying height monitoring and control during operation is not achieved
Solution Approach 1:
The patent implements a feedback mechanism where the embedded contact sensor (ECS) continuously monitors the flying height by detecting contact between the slider and disk surface. The ECS signal is fed back to the controller, which automatically adjusts the TFC heater current to maintain optimal flying height. This closed-loop feedback system replaces open-loop pre-calculated corrections, enabling continuous monitoring and automatic adjustment during operation.
Solution Approach 2:
The system uses the existing ECS, originally designed only for touchdown detection, to also perform continuous flying height monitoring. The ECS inherently provides flying height information through its contact signals, and the system leverages this self-generated data for automatic control adjustments, eliminating the need for separate sensing mechanisms.
2Productivity
If the head is flown closer to the disk for effective operation, then reading and writing efficiency improves, but the risk of physical contact and potential damage increases
Solution Approach 1:
The ECS provides real-time feedback on the proximity of the head to the disk surface. When the head approaches too closely or makes contact, the ECS generates a signal that is immediately fed back to the controller. The controller responds by adjusting the TFC heater current to increase thermal expansion of the slider, thereby increasing the flying height and preventing contact. This continuous feedback-control loop enables the system to operate at optimal close distances while maintaining safety margins.
3Device complexity
If the embedded contact sensor is used only for touchdown detection, then the system design remains simple, but flying height monitoring during operation is not achieved
Solution Approach 1:
The patent makes the ECS multi-functional by using it for both its original purpose (touchdown detection) and a new function (continuous flying height monitoring). The ECS signal processing is enhanced to extract flying height information during operation, not just at touchdown events. This eliminates the need for additional dedicated flying height sensors, maintaining system simplicity while achieving precise continuous monitoring capability.
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 allows for precise and continuous management of the head slider's flying height, measuring writer-induced protrusion without repeated touchdowns, and maintaining optimal head-disk spacing, enhancing the reliability and efficiency of HDD operations.
Implementation Method 1
ECS elements sense physical contact of the slider with the disk based on the ECS element's resistance, e.g., the amount of voltage across the element, which is affected by the temperature change caused by such physical contact
Implementation Method 2
providing electrical current to a heater element which causes the surrounding slider materials to expand and therefore protrude outward closer to the disk and then slightly reducing the current to the heater element to cause the surrounding slider materials to consequently contract away from the direction of the disk
Data Source
AI summary
Approaches for a flying height control scheme in a hard-disk drive (HDD) device. The flying height control scheme utilizes an embedded contact sensor (ECS) to characterize the topography of a magnetic-recording disk at various flying heights of a head slider over a corresponding disk. A relation between a particular flying height and a corresponding ECS value which characterizes the media topography at that particular flying height is represented in disk topography data. The disk topography data is accessed and used for active flying height control for the head-disk interface in view of the current ECS value.