Capacitive Detection Guarding for Angled Surfaces
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Solution Overview
Problem
Existing contactless human-machine interfaces using capacitive detection technology are ineffective when applied to appliances with parts forming a non-zero angle, as they suffer from interference and reduced detection range due to electrostatic field interference.
Innovation Solution
A device employing capacitive detection with guarded measurement electrodes and maintaining parts at a guard potential to eliminate parasitic coupling capacitances and control detection direction, allowing for precise three-dimensional interaction at a greater distance without contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive detection technology is used on appliances with parts forming a non-zero angle, then contactless interaction is enabled, but detection precision deteriorates due to electrostatic field interference
Solution Approach 1:
The patent introduces a guard electrode as an intermediary element between the measurement electrode and the interfering part. This guard electrode is maintained at a guard potential that is intermediate between the measurement electrode potential and the interfering part potential, thereby mediating the electrostatic field interactions and preventing direct interference from degrading measurement precision while preserving contactless interaction capability
Solution Approach 2:
The patent changes the electrical potential parameter by introducing a guard potential that is different from both the measurement electrode potential and the interfering part potential. This parameter change (introducing intermediate potential levels) allows the system to maintain adaptability for contactless interaction while improving measurement precision by controlling the electrostatic field distribution
2Device complexity
If measurement electrodes are used without guarding, then device complexity is reduced, but detection precision deteriorates due to parasitic coupling capacitances
Solution Approach 1:
The guard electrode serves as an intermediary that is electrically connected to both the measurement electrode and the interfering part. This intermediary structure allows the system to maintain lower complexity compared to fully shielded designs while still achieving improved detection precision by eliminating parasitic coupling capacitances through the guard electrode's potential control
3Area of stationary object
If detection is performed in all directions around the electrode, then detection coverage is maximized, but detection precision deteriorates due to unwanted directionality
Solution Approach 1:
The patent applies local quality by making the electrostatic field properties directionally selective through the guard electrode. The guard electrode is positioned and potential-controlled to create a localized field distribution that enhances detection in desired directions while suppressing detection in unwanted directions, thereby achieving both adequate coverage and improved precision through spatially differentiated field characteristics
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
Enables more precise and extended-range contactless interaction on appliances with non-zero angle configurations, avoiding interference and improving detection accuracy by controlling detection direction and reducing parasitic capacitance effects.
Implementation Method 1
at least one first and one second means, named guard means, for eliminating the parasitic coupling capacitances which distort the capacitive measurement
Implementation Method 2
said first detection means comprising several capacitive electrodes, named measurement electrodes; at least one, preferably each, of said measurement electrodes being guarded, by a first means, named guard means, at an alternating potential, named guard potential
Data Source
AI summary
A device is provided for interacting without contact, via at least one command object, with a user appliance, including at least one first and one second part which, in use, form between them a non-zero angle, the device including: at least one first mechanism of detection by capacitive technology, and without contact, of the at least one command object with respect to a first control surface defined with respect to the first part of the user appliance, the first detection mechanism including several measurement electrodes; at least one, of the measurement electrodes being guarded, by a guard mechanism, at a guard potential, different from a ground potential, of the at least one command object, and substantially identical to the potential of the measurement electrode; and at least one second guard mechanism, for guarding the second part of the user appliance at least partially at the guard potential.