Disk Drive Head Heater Control for Flying Height Stability
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Solution Overview
Problem
Maintaining the head flying height within an acceptable range becomes increasingly difficult in disk drives as data storage density increases, leading to potential read/write errors and damage due to variations in air density and head temperature.
Innovation Solution
A controller determines the upcoming pattern of data sectors to be written and adjusts the heater signal to maintain a constant head temperature and pole tip protrusion by considering the time constant delay between heater signal changes and resulting pole tip protrusion, thereby controlling the head flying height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data storage density is increased by narrowing tracks and flying height gaps, then storage capacity is improved, but head flying height control becomes more difficult and error rates increase
Solution Approach 1:
The controller determines the upcoming pattern of data sectors to be written in advance and proactively adjusts the heater signal before the actual writing occurs. This preliminary action allows the system to anticipate heating effects and maintain constant head temperature, thereby maintaining stable flying height and preventing read/write errors that would otherwise occur with high-density narrow-track operation
Solution Approach 2:
The system dynamically adjusts the heater signal based on the determined upcoming write pattern rather than using a static heating approach. The controller modifies heating in real-time response to varying write patterns (contiguous vs. alternating sectors), enabling adaptive compensation that maintains flying height stability across different operational conditions required for high-density storage
2Productivity
If head temperature is allowed to vary during writing operations, then writing speed is improved, but pole tip protrusion changes causing flying height instability
Solution Approach 1:
The controller uses feedback from the determined upcoming write pattern to continuously adjust the heater signal. By monitoring what sectors will be written and anticipating the resulting heating, the system applies compensatory heating control that maintains constant head temperature and stable pole tip protrusion, thereby maintaining flying height stability while allowing high-speed writing operations to proceed
Solution Approach 2:
The system changes the heater signal parameter dynamically based on the upcoming write pattern. Instead of maintaining a fixed heating level, the controller adjusts heating parameters (signal magnitude and timing) in response to the determined pattern of contiguous or alternating sector writes, enabling the system to maintain thermal stability despite varying write intensities that occur during high-speed operation
3Manufacturing precision
If heater signal is adjusted rapidly to compensate for temperature changes, then flying height control is improved, but instability increases due to time constant delay
Solution Approach 1:
By determining the upcoming write pattern in advance, the controller can apply preliminary heating adjustments that account for the thermal time constant delay. This proactive approach allows the system to initiate heating changes before temperature deviations occur, achieving precise flying height control without the instability that would result from reactive, rapid adjustments to an already-changing temperature
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 stable head flying height maintenance during varying writing and non-writing patterns, reducing the risk of errors and damage by anticipating and compensating for heating effects, thus ensuring consistent data storage performance.
Implementation Method 1
The controller controls a heater signal to control heating of the head by a heater element
Implementation Method 2
The heads can fly in close proximity to the surfaces of the disks upon air bearings
Data Source
AI summary
A disk drive includes a rotatable data storage disk, a head, a heater element, and a controller. The disk includes a plurality of data sectors between servo spokes. The head is configured to fly on an air cushion relative to the rotating disk while writing data on the data sectors. The heater element is attached to the head and configured to controllably heat the head responsive to a heater signal. The controller determines an upcoming pattern of selected ones of the data sectors on which data is to be written through the head in response to at least one write command from a host device, and controls the heater signal in response to the determined upcoming pattern of data sectors on which data is to be written.