Capacitance Measurement for Dielectric Elastomers

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Solution Overview

Problem

Existing methods for measuring the capacitance of dielectric elastomers, which deform elastically with applied voltage, face challenges in reliability due to structural restrictions and shape deformation, especially when trying to accurately quantify elastic deformation states.

Innovation Solution

A device and method that include a power source for variable voltage control, a current detector, and a capacitance estimating unit which samples energizing current during a current reduction period to estimate capacitance using a correlation model, allowing for reliable capacitance measurement even with varying voltages and external forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a displacement sensor is used to directly measure the elastic deformation of the elastomer, then the amount of elastic deformation can be obtained, but the sensor placement causes structural restrictions and the flexible nature of the elastomer makes reliable measurement difficult

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidstructural restrictions

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical displacement sensor system with an electrical measurement system. Instead of using a physical sensor to directly measure elastomer deformation, the system measures the capacitance change of the elastomer itself, which varies with its deformation state. This substitution eliminates the need for external sensors and their associated structural constraints, while providing reliable measurement through electrical property changes that occur naturally with elastomer deformation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If the voltage applied to the elastomer is variably manipulated to control stiffness, then the elastomer can be controlled to a required target state, but the capacitance measurement reliability is compromised due to voltage changes affecting the measurement

Engineering Contradiction:

Improvestiffness controlVSAvoidcapacitance measurement reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs periodic voltage manipulation with superimposed vibration components on the base voltage. By applying small amplitude periodic vibrations to the voltage signal, the system can distinguish between capacitance changes caused by intentional stiffness control and those caused by external disturbances. The periodic action creates a characteristic response pattern that allows the measurement system to filter out noise and reliably extract the elastomer's deformation state even during variable voltage operation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system implements feedback control by continuously monitoring the capacitance of the elastomer and using this information to adjust the applied voltage. The capacitance measurement serves as feedback about the elastomer's current state, allowing the control system to maintain the desired stiffness while compensating for measurement uncertainties. This closed-loop approach ensures that variable voltage manipulation achieves the target stiffness state while maintaining measurement reliability through continuous verification.

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

Enables precise and reliable measurement of capacitance, maintaining the elastomer's state with minimal structural restrictions, and accounting for changes due to external forces, thus effectively controlling the elastomer's stiffness and deformation.

Implementation Method 1

the dielectric elastomer is compressed by Maxwell stresses in the direction of an electric field attributable to the applied voltage

Methodology Applied

Scientific EffectMaxwell stresses: Electric Field

Implementation Method 2

the elastomer is an electrical insulator and therefore functions as a capacitive element

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

a transient response phenomenon causes the energizing current of the elastomer to suddenly increases and then gradually decreases... the time-dependent change of the actual energizing current... has a high correlation with the capacitance of the elastomer

Methodology Applied

Scientific EffectTransient response phenomenon: Capacitance

Data Source

PatentUS10036674B2Capacitance measuring device and capacitance measurement method for dielectric elastomer

Publication Date: 2018.07.31 HONDA MOTOR CO LTD

AI summary

A device capable of measuring the capacitance of a dielectric elastomer by variably manipulating the voltage applied to the dielectric elastomer includes a capacitance estimating unit that acquires current detection values at a plurality of sampling times in a current reduction period in which, when an output voltage of a power source changes, an energizing current of a dielectric elastomer increases and then gradually decreases according to the change in the output voltage, and estimates the capacitance of the dielectric elastomer on the basis of a model representing a correlation between the time-dependent change of the energizing current and the capacitance of the dielectric elastomer in the current reduction period, and the current detection values.