Embedded Contact Sensor Calibration via Interface Voltage Control

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Solution Overview

Problem

The existing methods for calibrating embedded contact sensors (ECS) in magnetic recording heads are inadequate, as the ECS signal is heavily influenced by thermal fly-height control (TFC) power, making it difficult to accurately determine head/disk clearance without causing unintended contact or damage.

Innovation Solution

A method involving the application of various interface voltages to alter head/disk clearance, calculating the corresponding ECS signals, and establishing a relationship between the changes in clearance and ECS signals, allowing for accurate calibration and adjustment of head/disk spacing without relying on TFC power variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If TFC power is applied to adjust head/disk clearance, then the transducers are moved closer to the disk surface, but the ECS signal becomes heavily influenced by thermal effects making accurate calibration difficult

Engineering Contradiction:

Improvehead/disk clearanceVSAvoidECS signal accuracy

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent introduces interface voltage as an intermediary parameter to control head/disk clearance. Instead of directly using TFC power which creates thermal interference with ECS measurement, the interface voltage serves as a mediator that can adjust clearance without the same thermal side effects, allowing more accurate ECS-based calibration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the thermal-based TFC mechanism with an electrical field-based interface voltage mechanism for clearance control during calibration. This substitution eliminates the thermal interference that corrupts ECS signals, allowing accurate measurement and calibration of head/disk clearance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If TFC power is increased to reduce head/disk clearance, then proper reading and writing is enabled, but unintended contact or damage may occur

Engineering Contradiction:

Improvereading and writing functionVSAvoidtouchdown events and damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where ECS signals are continuously monitored to determine actual head/disk clearance. This feedback allows the system to adjust interface voltage to maintain optimal clearance, preventing both excessive clearance that would degrade reading/writing and insufficient clearance that would cause touchdown events and damage.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the head/disk clearance dynamic and adjustable through interface voltage control during operation. This allows the system to adaptively maintain optimal clearance based on real-time ECS feedback, rather than using fixed TFC power settings that could lead to unintended contact.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If interface voltage is used to control head/disk clearance, then accurate calibration is achieved, but additional control parameters are required

Engineering Contradiction:

ImproveECS calibration accuracyVSAvoidcontrol parameters

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent leverages the existing interface voltage, which is already part of the magnetic head's electrical architecture, and gives it an additional calibration function. This existing electrical parameter serves dual purposes: normal operational function and clearance control during calibration, avoiding the need for entirely new hardware components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enables precise calibration and maintenance of head/disk clearance, reducing the number of touchdown events and minimizing potential damage, while providing a more accurate and reliable method for monitoring and adjusting head/disk spacing during operation.

Implementation Method 1

applying different interface voltages to cause changes in the head/disk clearance

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 2

The ECS typically is constructed of a resistive film which detects contact through a change in resistance based on a change in temperature

Methodology Applied

Scientific EffectResistive temperature detection: Electrical Resistance

Implementation Method 3

heating the components of the reader/writer causing thermal expansion of the materials, which results in the reader/writer transducers protruding closer to the surface of the hard disk

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8976480B1Method to convert and calibrate the embedded contact sensor signal to clearance and spacing information using interface voltage control

Publication Date: 2015.03.10 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

Embodiments of the present invention generally relate to a method for obtaining head/disk clearance based on ECS signal. The ECS is calibrated by applying different interface voltages to cause changes in the head/disk clearance, the ECS signal at each interface voltage is obtained, and the relationship between the change in head/disk clearance and the ECS signal is calculated. From this relationship, the head/disk clearance may be obtained based on ECS signal.