Force Detection Sensor Using Interdigital Electrode SAW Resonator

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing force detection sensors face challenges in accurately detecting minor changes in pressing force due to limitations in amplitude signal output, resulting in a low force detection property.

Innovation Solution

A force detection sensor configuration featuring a base member with a pressure receiving surface and a placement surface having an inter-digital electrode, where the pitch change of the electrode fingers alters the surface acoustic wave frequency, enabling precise detection of small force changes, utilizing a piezoelectric material like quartz crystal for enhanced temperature characteristics and mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional vibrator-based force detection sensor is used, then the structure is simple, but the force detection property is low and minor force changes are hard to detect

Engineering Contradiction:

Improveforce detection propertyVSAvoidsensor structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the conventional vibrator-based mechanical detection system with a surface acoustic wave (SAW) resonator system. The inter-digital electrode excites surface acoustic waves on the piezoelectric substrate, and force detection is achieved through frequency measurement rather than amplitude measurement, fundamentally changing the detection mechanism to achieve higher precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from amplitude (in conventional sensors) to frequency (in SAW resonator). The resonance frequency of the surface acoustic wave changes in response to applied force, and this frequency shift is used as the detection signal, providing superior sensitivity for detecting minor force changes.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If amplitude-based detection is used in conventional sensors, then the detection mechanism is simple, but minor force changes produce minimal signal variation

Engineering Contradiction:

Improvedetection accuracyVSAvoidsignal sensitivity

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent transitions from amplitude-based detection to frequency-based detection. The resonance frequency of the surface acoustic wave is highly sensitive to changes in mass loading and mechanical stress, allowing even minor force changes to produce measurable frequency shifts, thereby dramatically improving detection accuracy and signal sensitivity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a piezoelectric material is used for the base member, then temperature characteristics and mechanical strength are improved, but the material selection becomes more restricted

Engineering Contradiction:

Improvetemperature characteristicsVSAvoidmaterial selection

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs a composite structure consisting of a piezoelectric substrate (such as quartz crystal, lithium niobate, or lithium tantalate) combined with metal inter-digital electrode fingers. This composite approach leverages the excellent temperature characteristics and mechanical strength of piezoelectric materials while maintaining manufacturability through standard thin-film deposition techniques.

Inventive Principle:

Principle #40Composite materials

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 sensor achieves higher accuracy in detecting both small and large forces, improving force detection property and reliability, suitable for use in robots and other applications.

Implementation Method 1

surface acoustic wave excited in the surface of the base member (the resonance frequency of an SAW resonator)

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Implementation Method 2

the second surface includes a surface of a piezoelectric material

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 3

the second surface deforms when the first surface is subjected to the force

Methodology Applied

Scientific EffectDeformation: Deformation

Data Source

PatentUS10545063B2Force detection sensor having a base member with a force receiving surface and another surface with an interdigital electrode

Publication Date: 2020.01.28 SEIKO EPSON CORP

AI summary

A force detection sensor includes a base member having a first surface subjected to an external force and a second surface having a normal direction different from the first surface, and an inter-digital electrode placed on the second surface. Further, the second surface deforms when the first surface is subjected to the force. Furthermore, the second surface includes a part formed by a surface of a piezoelectric material and the inter-digital electrode is placed in the part. The piezoelectric material is quartz crystal. The second surface is parallel to an electrical axis of the quartz crystal.