Read/Write Head Residual Temperature Estimation for Flying Height Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Maintaining the flying height of read/write elements in disk drives within an acceptable range becomes increasingly difficult as data storage densities increase, leading to potential bit error rates and contact issues due to temperature variations and air density changes, making it challenging to estimate and control head temperature across multiple heads in disk drives.

Innovation Solution

A method and circuit that estimate the residual temperature of a read/write head based on its idle period using a head idle timer and temperature estimator, allowing for controlled flying height adjustment through a heater controller, reducing the need for continuous estimation models across all heads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If continuous temperature estimation models are run for all heads, then flying height control accuracy is improved, but computation time and power consumption increase

Engineering Contradiction:

Improveflying height control accuracyVSAvoidcomputation time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent divides the heads into two categories: currently active head and idle heads. Temperature estimation is performed continuously only for the active head, while idle heads use a simplified estimation based on idle time. This segmentation reduces overall computation while maintaining necessary accuracy for each group.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying full continuous temperature estimation to all heads, the patent applies partial action by using simplified idle-time-based estimation for inactive heads. This reduces computation time and power consumption while still providing sufficient accuracy for flying height control when heads are switched.

Inventive Principle:

Principle #16Partial or excessive action

2Measurement precision

If continuous temperature estimation models are run for all heads, then flying height control accuracy is improved, but power consumption increases

Engineering Contradiction:

Improveflying height control accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent segments heads into active and idle categories, applying different estimation strategies. Only the active head receives continuous temperature estimation, while idle heads use computationally lighter idle-time-based estimation, thereby reducing overall power consumption.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by using simplified estimation for idle heads instead of full continuous estimation. This reduces power consumption significantly while maintaining adequate temperature estimation accuracy for when the heads are eventually activated.

Inventive Principle:

Principle #16Partial or excessive action

3Quantity of substance

If flying height range is reduced to maintain acceptable bit error rate, then data storage density is improved, but control difficulty increases

Engineering Contradiction:

Improvedata storage densityVSAvoidflying height control difficulty

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The patent implements feedback by continuously monitoring head temperature and idle time, then adjusting flying height control accordingly. When a head is switched, the system uses the stored idle time information to estimate residual temperature and adjust flying height, ensuring the read/write element remains within the narrow acceptable range despite reduced margin.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary action by pre-calculating and storing idle time for each head. When a head switch occurs, this pre-stored information is immediately used to estimate temperature and adjust flying height, preventing control issues that would arise from the reduced acceptable flying height range.

Inventive Principle:

Principle #10Preliminary action

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 minimizes computation time and power while maintaining accurate flying height control, ensuring reliable data storage by estimating and adjusting the flying height of read/write elements efficiently, even when switching between heads, thus reducing bit error rates and preventing head-disk contact.

Implementation Method 1

Some disk drives use a heater to controllably heat the tip of the head in order to vary the flying height of the read/write elements

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The heads can fly in close proximity to the surfaces of the disks upon air bearings

Methodology Applied

Scientific EffectAir bearing: Air Lubrication

Data Source

PatentUS7453662B2Estimating residual temperature for flying height adjustment of read/write heads

Publication Date: 2008.11.18 SEAGATE TECH LLC

AI summary

Methods of estimating a flying height of a read/write head include determining an idle period of the head since a last selection of the head as a working head, estimating the residual temperature of the head in response to the idle period, and estimating the flying height of the head in response to the estimated residual temperature of the head.