Microactuator Conductive Joint Impedance Mitigation

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Solution Overview

Problem

Dual stage actuators experience increased impedance at interconnection joints due to oxidation, microcracks, corrosion, and material migration, especially when dissimilar metals are used, leading to reduced accuracy and stability in microactuator control efforts.

Innovation Solution

A control circuit applies a bi-directional transition signal with stepwise voltage changes to the conductive input junction of microactuating elements to mitigate impedance changes, using specially configured voltage profiles that minimize mechanical disturbance and restore the joint to its normal state without inducing significant movement of the control object.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dissimilar metals are used in the conductive input junction, then electrical conductivity and signal transmission are improved, but impedance increases due to oxidation, microcracks, corrosion, and material migration

Engineering Contradiction:

Improveelectrical conductivityVSAvoidimpedance increase

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control circuit applies a cleaning signal before normal operation to prevent oxidation and impedance buildup. This preliminary action removes contaminants and stabilizes the junction, preventing the harmful effects from developing during subsequent operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit periodically applies cleaning signals during normal operation to continuously remove oxidation and maintain low impedance. This periodic maintenance action counteracts the gradual buildup of harmful effects that occur during normal electrical operation.

Inventive Principle:

Principle #19Periodic action

2Reliability

If a cleaning signal is applied to reduce junction impedance, then electrical conductivity is restored, but mechanical displacement of the control object may occur

Engineering Contradiction:

Improveimpedance stabilityVSAvoidcontrol accuracy

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The cleaning signal is designed with specific characteristics (amplitude, duration, frequency) that are optimized for removing oxidation from the junction without causing excessive mechanical displacement. This localized optimization of signal parameters allows the same signal to perform both cleaning and maintain control accuracy.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The cleaning signal applies a controlled amount of voltage that is sufficient to remove oxidation and reduce impedance but limited enough to avoid causing large mechanical displacements. This partial action achieves the necessary cleaning effect without excessive disturbance to the control object.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If the microactuator control loop operates at high gain, then positioning precision is improved, but stability is reduced due to impedance variations at the conductive joint

Engineering Contradiction:

Improvepositioning precisionVSAvoidcontrol loop stability

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The control circuit monitors the impedance of the conductive joint and adjusts the cleaning signal frequency and amplitude based on detected impedance levels. This feedback mechanism allows the system to maintain optimal cleaning action while adapting to changing junction conditions, thereby preserving both precision and stability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control circuit dynamically changes the parameters of the cleaning signal (voltage amplitude, pulse duration, frequency) based on the operating conditions and detected impedance levels. These parameter adjustments optimize the cleaning effect at different stages of operation while maintaining control loop stability.

Inventive Principle:

Principle #35Parameter changes

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

The solution effectively reduces impedance changes in microactuator joints, maintaining control loop stability and accuracy, preventing unwanted positioning errors and potential damage from large mechanical displacements, while being compatible with existing servo control systems.

Implementation Method 1

A control circuit is adapted to apply a bi-directional transition signal to the conductive input junction to reduce an increased impedance of the junction

Methodology Applied

Scientific EffectImpedance change mitigation: Electrical Resistance

Data Source

PatentUS8891200B1Impedance mitigation of a microactuator conductive joint

Publication Date: 2014.11.18 SEAGATE TECH LLC

AI summary

Apparatus and method for mitigating impedance changes in a microactuator conductive joint. In accordance with some embodiments, a microactuating element has a conductive input junction, the junction having dissimilar metals in contact with one another. The microactuating element is adapted to mechanically deform to displace a control object responsive to a micractuation control signal that is applied to the junction. A control circuit applies a bi-directional transition signal to the conductive input junction to reduce an increased impedance of the junction.