Capacitive Sensor Auxiliary Structure for Position Detection

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Solution Overview

Problem

Capacitive sensing systems for human machine interfaces (HMIs) face challenges in detecting the position of control actuators and user touch events due to weak responses from conductive structures or a user's finger, particularly in capacitive position detection for rotary and linear control elements.

Innovation Solution

The described user interface control apparatus incorporates conductive capacitor plate structures, a movable auxiliary conductive structure, and an interface circuit that performs mutual and self-capacitance tests to enhance sensitivity and robustness in detecting the position of a user's finger or control actuator, using a combination of capacitive and optical sensing methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If capacitive sensing is used for position detection, then long life time and low implementation costs are achieved, but weak response from conductive structures or user's finger occurs

Engineering Contradiction:

Improvelong life timeVSAvoidsensitivity of detection

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

An auxiliary conductive structure is introduced as an intermediary element to enhance the capacitive coupling between the capacitor plate structures and the target object (user's finger or control actuator). This auxiliary structure acts as a mediator that amplifies the weak capacitive response signals, thereby improving measurement precision without compromising the reliability and cost benefits of capacitive sensing

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If capacitive sensing is used for position detection, then ease of use as sealed control element is achieved, but weak response from conductive structures occurs

Engineering Contradiction:

Improveease of use as sealed control elementVSAvoidsensitivity of detection

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The auxiliary conductive structure serves as a mediator that enhances the capacitive coupling between the sealed capacitor plate structures and the target object. This allows the sealed control element to maintain its ease of operation while improving the sensitivity of detection by amplifying the weak capacitive responses through the intermediary auxiliary structure

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If mutual capacitance test and self-capacitance test are performed, then position detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improveposition detection accuracyVSAvoidinterface circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The interface circuit is designed to perform multiple functions using the same hardware components. The same capacitor plate structures and auxiliary conductive structures are utilized for both mutual capacitance testing and self-capacitance testing. This multi-functional approach improves position detection accuracy through multiple measurement modes while minimizing the increase in device complexity by reusing existing circuit elements

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 solution improves the sensitivity and robustness of capacitive sensing, allowing for accurate detection of user touch events and control apparatus position, even in environments with explosives or chemical processes, by utilizing mutual and self-capacitance measurements with auxiliary conductive structures.

Implementation Method 1

an interface circuit to provide excitation signals to, and receive sense signals from, the conductive capacitor plate structures to perform a mutual capacitance test and a self-capacitance test of individual ones of the conductive capacitor plate structures to determine a position of the second structure or a user's finger

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11473938B2Enhancing sensitivity and robustness of mechanical rotation and position detection with capacitive sensors

Publication Date: 2022.10.18 TEXAS INSTRUMENTS INC

AI summary

Described example user interface control apparatus includes a first structure, with a first side, conductive capacitor plate structures spaced along a first direction on the first side, a movable second structure with an auxiliary conductive structure, and an interface circuit to provide excitation signals to, and receive sense signals from, the conductive capacitor plate structures to perform a mutual capacitance test and a self-capacitance test of individual ones of the conductive capacitor plate structures to determine a position of the second structure or a user's finger relative to the first structure along the first direction.