Switched Reference Electrode for Capacitance Sensor Drift Correction
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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 operating over long detection ranges, compromising detection accuracy.
Innovation Solution
A capacitance sensor with a detection electrode and a reference electrode coupled via a switch, allowing for switching between open and closed states to correct sensed values, and a separate reference sensor to calculate dielectric constants for ambient air correction.
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 arrangements and shielding requirements
Solution Approach 1:
The invention extracts the reference electrode from the detection electrode structure, positioning it on a different member (such as the base) rather than integrating it into the same robotic component. This separation eliminates the need for complex shielding arrangements around the reference electrode, as it no longer needs to prevent objects from being detected by the reference electrode itself. The reference electrode independently measures ambient dielectric constant changes, which are then used to correct detection signals from the detection electrode.
Solution Approach 2:
The invention introduces an intermediary processing step where the reference electrode's measurement of ambient dielectric constant serves as a mediator to correct the detection electrode's output. Instead of directly comparing signals from co-located electrodes, the system uses the reference electrode to characterize environmental conditions (dielectric constant of air) and applies this characterization as a correction factor to the detection signal, thereby eliminating the need for complex physical arrangements.
2Length of stationary object
If the sensing range is extended, then detection capability is improved, but sensing drift increases due to ambient temperature and humidity changes
Solution Approach 1:
The invention implements a feedback mechanism where the reference electrode continuously monitors ambient dielectric constant changes caused by temperature and humidity variations. This monitoring provides real-time feedback information that is used to correct the detection electrode's measurements. The correction process compensates for environmental drift effects, allowing the system to maintain detection accuracy even when operating over extended sensing ranges where ambient conditions have greater influence.
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 is configured to output a sensed value representing a capacitance created between the detection electrode and an object
Implementation Method 2
The processing device of the capacitance sensor calculates a dielectric constant of ambient air based on an output from the reference sensor and corrects the sensed value with the dielectric constant
Data Source
AI summary
A capacitance sensor 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 includes a detection sensor including a detection electrode and configured to output a sensed value representing a capacitance created between the detection electrode and an object such as a human worker. The sensor includes a reference electrode provided to face the detection electrode and coupled to a reference potential via a switch. The sensor also includes a processing device that controls opening/closing of the switch to transition between a first state in which the reference electrode is opened and a second state in which the reference electrode is coupled to the reference potential.