Magnetic Head Touchdown Detection via Staggered Actuator Control

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Solution Overview

Problem

Existing magnetic disk devices face challenges in accurately controlling the flying height of magnetic heads over magnetic disks due to difficulties in detecting touchdowns, which affects recording density and data access precision.

Innovation Solution

The magnetic disk device employs a dual actuator system with independent control of magnetic heads and a controller that synchronizes the detection of touchdowns across both systems, allowing for precise measurement and control of flying height by varying the power supplied to a heater in the magnetic heads, thereby preventing simultaneous touchdowns and improving detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple magnetic heads are moved by multiple actuator systems simultaneously, then data access efficiency is improved, but touchdown detection accuracy deteriorates due to simultaneous touchdowns causing disturbances

Engineering Contradiction:

Improvedata access efficiencyVSAvoidtouchdown detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent divides the touchdown detection process into separate sequential operations for each actuator system. The controller detects touchdowns for the first actuator system, then detects touchdowns for the second actuator system at a different timing, preventing simultaneous touchdowns and eliminating mutual disturbances while maintaining the ability to serve multiple heads

Inventive Principle:

Principle #1Segmentation

2Quantity of substance

If magnetic head flying height is reduced to increase recording density, then recording density is improved, but touchdown detection becomes more difficult due to closer proximity to disk surface

Engineering Contradiction:

Improverecording densityVSAvoidtouchdown detection difficulty

Core Design Contradiction:

Quantity of substanceVSDifficulty of detecting and measuring

Solution Approach 1:

The patent employs feedback mechanisms where the controller continuously monitors touchdown status of magnetic heads and adjusts detection timing accordingly. By receiving feedback from touchdown detections of the first actuator system, the controller optimizes the detection timing for the second actuator system, enabling accurate detection even at reduced flying heights

Inventive Principle:

Principle #23Feedback

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 enhances the accuracy of touchdown detection and flying height control, improving data recording density and access precision by ensuring that each magnetic head's touchdown is measured individually and at different times, reducing disturbances and improving overall system performance.

Implementation Method 1

varying the power supplied to a heater in the magnetic heads, thereby preventing simultaneous touchdowns

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11475914B2Touchdown detection for multiple actuators on magnetic recording device

Publication Date: 2022.10.18 KK TOSHIBA

AI summary

According to an embodiment, a controller of a magnetic disk device executes control such that detection of touchdowns of one or more first magnetic heads and detection of touchdowns of one or more second magnetic heads are executed at different timings. In addition, the controller executes control such that touchdowns of the one or more first magnetic heads are detected at different timings and touchdowns of the one or more second magnetic heads are detected at different timings.