Capacitance Sensor Drift Correction for Collaborative Robots
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Solution Overview
Problem
Capacitance sensors used in collaborative robots are prone to sensing drift due to ambient temperature and humidity changes, especially when the sensing range is set long, compromising detection accuracy.
Innovation Solution
A capacitance sensor with a detection electrode and a reference electrode that switches between open and coupled states to correct sensing drift, and a configuration that includes a detection sensor and a reference sensor at different positions to calculate and correct for dielectric constant changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference electrode is used to correct sensing drift, then detection accuracy is improved, but device complexity increases due to special arrangement requirements
Solution Approach 1:
The patent combines the reference electrode function with the detection electrode structure by providing the reference electrode on the same substrate. This integration eliminates the need for separate reference electrode arrangements and shielding structures, thereby reducing device complexity while maintaining the drift correction capability that improves detection accuracy.
Solution Approach 2:
The substrate serves multiple functions: it supports both the detection electrode and the reference electrode, and acts as the sensing surface itself. This multi-functionality reduces the need for additional components and complex arrangements, resolving the contradiction between achieving accurate drift correction and maintaining simple device configuration.
2Length of stationary object
If sensing range is extended, then detection capability is improved, but sensing drift increases due to ambient conditions
Solution Approach 1:
The patent implements feedback by continuously monitoring the capacitance between the detection electrode and reference electrode, comparing it with a reference value, and automatically adjusting the detection threshold based on the calculated drift amount. This feedback mechanism enables the sensor to maintain high detection accuracy over extended sensing ranges by compensating for ambient condition-induced drift in real-time.
Solution Approach 2:
The patent dynamically adjusts the detection threshold parameter based on measured drift conditions. By changing the threshold parameter according to the calculated drift amount, the system maintains accurate detection performance across varying sensing ranges and ambient conditions, resolving the trade-off between extended range and precision.
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 solution effectively corrects sensing drift caused by ambient conditions, maintaining detection accuracy and simplifying the sensor configuration by eliminating the need for additional shielding arrangements.
Implementation Method 1
a detection sensor that includes a detection electrode and outputs a sensed value representing a capacitance created between the detection electrode and an object
Implementation Method 2
a reference electrode provided to face the detection electrode and coupled to a reference potential via a switch... corrects the sensed value measured in the first state with the sensed value measured in the second state
Implementation Method 3
a reference sensor provided at a position that is different from a position of the detection electrode and including electrodes paired via ambient air. The capacitance sensor further includes a processing device that calculates a dielectric constant of the ambient air based on an output from the reference sensor and that corrects the sensed value with the dielectric constant
Data Source
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AI summary
A capacitance sensor (6) is capable of correcting an object detection result irrespective of changes in ambient air conditions and capable of simplifying a configuration for the correction. The capacitance sensor (6) includes a detection sensor (11) including a detection electrode (25) and configured to output a sensed value representing a capacitance created between the detection electrode (25) and an object such as a human worker (H). The sensor includes a reference electrode (12) provided to face the detection electrode (25) and coupled to a reference potential via a switch (30b). The sensor also includes a processing device (13) that controls opening/closing of the switch (30b) to transition between a first state in which the reference electrode (12) is opened and a second state in which the reference electrode (12) is coupled to the reference potential.