Capacitive Rotation Sensing with Dynamic Reference Updates

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Solution Overview

Problem

Existing electrostatic capacitance detection methods for touch panels face challenges in accurately detecting rotation direction, rotation amount, and rotation angle due to component rattle and time-related capacitance changes, leading to inappropriate detection of electrostatic capacitance ratios.

Innovation Solution

An electronic apparatus with a first, second, and third detection electrode group, a rotating member, and a detection unit that determines rotation direction, amount, or angle using electrostatic capacitances and threshold values, while updating reference values based on the smallest detected capacitance to mitigate rattle-induced errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If electrostatic capacitance detection method is used for touch panels, then simultaneous multipoint detection can be performed with ease, but component rattle and time-related capacitance changes cause inaccurate detection of rotation direction, rotation amount, and rotation angle

Engineering Contradiction:

Improvesimultaneous multipoint detection capabilityVSAvoidrotation detection accuracy

Core Design Contradiction:

Extent of automationVSMeasurement precision

Solution Approach 1:

The system performs preliminary action by detecting and updating reference capacitance values before actual rotation detection occurs. The determination unit continuously monitors electrostatic capacitances and updates reference values in advance, so that when rotation detection is needed, accurate reference data is already available to compensate for component rattle and time-related changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by using the detection unit to continuously monitor electrostatic capacitances of multiple detection electrodes, comparing current measurements against stored reference values, and updating the reference values based on detected changes. This closed-loop feedback mechanism ensures that drift and rattle-induced errors are continuously corrected, maintaining accurate rotation detection despite environmental changes.

Inventive Principle:

Principle #23Feedback

2Reliability

If gain control is used to absorb electrostatic capacitance changes, then time-related capacitance variations can be compensated, but component rattle during operation causes inappropriate electrostatic capacitance ratio detection

Engineering Contradiction:

Improvecapacitance change compensationVSAvoidelectrostatic capacitance ratio accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system segments the detection process by dividing the detection electrodes into multiple groups (first detection electrode group, second detection electrode group, third detection electrode group) with different reference values. Each group is independently monitored and updated, allowing the system to detect rotation based on relative capacitance changes across segments rather than relying on a single gain-controlled measurement, thereby eliminating rattle-induced ratio errors.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system applies parameter changes by dynamically updating reference capacitance values for each detection electrode group based on actual measured values. Instead of using fixed gain control, the system adjusts the reference parameters (capacitance values) to match current conditions, allowing accurate rotation detection even when component rattle causes temporary capacitance fluctuations.

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

This solution enables accurate detection of rotation direction, amount, and angle, even with component rattle and capacitance changes, by updating reference values and using threshold values to improve the reliability of electrostatic capacitance measurements.

Implementation Method 1

a detection unit that detects electrostatic capacitances of the first to third detection electrode groups

Methodology Applied

Scientific EffectElectrostatic capacitance detection: Capacitance

Implementation Method 2

a rotating member configured to move among positions in which the rotating member faces the first to third detection electrode groups

Methodology Applied

Scientific EffectElectrostatic induction: Electrostatic Induction

Data Source

PatentUS10171718B2Capacitive rotation sensing apparatus and method

Publication Date: 2019.01.01 CANON KK

AI summary

An electronic apparatus includes a first detection electrode group, a second detection electrode group, a third detection electrode group, a rotating member for moving among positions in which the rotating member faces the first to third detection electrode groups, a detection unit for detecting electrostatic capacitances of the first to third detection electrode groups, a determination unit for determining a rotation direction, a rotation amount, or a rotation angle of the rotating member in accordance with the electrostatic capacitances of the first to third detection electrode groups and threshold values for the first to third detection electrode groups, and an updating unit for updating a reference value of one of the first to third detection electrode groups corresponding to a selected smallest electrostatic capacitance using the selected smallest electrostatic capacitance.