Resonant Coil Displacement Sensing Without Optical Elements

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Solution Overview

Problem

Existing displacement amount detection technologies for movable members, such as musical keyboard keys, rely on delicate optical elements that are sensitive to shock, vibration, and contamination, leading to long-term reliability issues.

Innovation Solution

A displacement amount detection apparatus utilizing a first resonant circuit mounted to a movable member and a second resonant circuit on a support member, generating a magnetic field to output a detection signal based on relative position, with equivalent circuits simulating infinite and zero distance states to correct and calculate displacement amounts, eliminating the need for optical elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical elements (e.g., grayscale) are used to detect displacement amount, then measurement precision can be achieved, but reliability deteriorates due to sensitivity to shock, vibration, and contamination

Engineering Contradiction:

Improvedisplacement amount detection precisionVSAvoidlong-term reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the optical detection system with an electromagnetic detection system. Specifically, it uses a resonant circuit comprising a coil and capacitor that generates electromagnetic signals to detect the displacement amount of keys. This substitution eliminates the use of optical elements (grayscale, optical sensors) that are sensitive to shock, vibration, and contamination, thereby improving reliability while maintaining measurement precision through electromagnetic field-based detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from optical transmission to electromagnetic resonance characteristics. By measuring changes in resonance frequency or impedance of the resonant circuit as keys are pressed, the system achieves displacement detection without relying on optical properties. This parameter change makes the detection system immune to optical interference while preserving measurement accuracy.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If delicate optical elements are used for displacement detection, then measurement precision is improved, but device complexity increases due to sensitivity requirements

Engineering Contradiction:

Improvedisplacement amount detection precisionVSAvoidoptical element complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the complex optical detection system with a simpler electromagnetic resonant circuit. The resonant circuit consists of basic electrical components (coil, capacitor, resistor) that are inherently more robust and easier to manufacture than delicate optical elements. This substitution reduces device complexity while achieving comparable or superior measurement precision through electromagnetic resonance detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If optical elements are used to detect key depression, then measurement precision can be achieved, but ease of manufacture deteriorates due to assembly difficulty

Engineering Contradiction:

Improvekey depression detection precisionVSAvoidassembly ease

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the optical detection system with an electromagnetic resonant circuit that can be more easily integrated into the keyboard structure. The coil and capacitor can be mounted directly on or near the key mechanisms, eliminating the need for precise optical alignment and complex assembly procedures. This substitution significantly improves ease of manufacture while maintaining key depression detection precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution provides long-term reliability by accurately determining displacement amounts with reduced error due to variations in circuit characteristics, enhancing the durability and precision of displacement detection.

Implementation Method 1

a second resonant circuit that includes a second coil that generates a magnetic field upon supply of an electric current

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12072214B2Displacement amount detection apparatus, displacement amount detection method, and manipulation information output apparatus

Publication Date: 2024.08.27 YAMAHA CORP

AI summary

An apparatus includes a first resonant circuit including a first coil mounted to a movable member; a second resonant circuit including a second coil facing the first coil and generating a magnetic field upon supply of an electric current and outputs a detection signal of a voltage level depending on a relative position of the second coil to a position of the first coil; and a first equivalent circuit equivalent to the second resonant circuit in a case where a distance between the first and second coils is infinite and a second equivalent circuit equivalent to the second resonant circuit in a case where the distance is zero. A processor corrects the detection signal based on an output signal output from the first equivalent circuit and an output signal output from the second equivalent circuit, and calculates, based on the corrected detection signal, a displacement amount of the movable member.