Car Door Capacitive Sensor Layout to Prevent Water False Triggers
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Solution Overview
Problem
Existing capacitive sensors used for locking and unlocking motor vehicle doors inadvertently trigger actions due to water projection from rain or washing, as they cannot distinguish between water effects and user hand approaches.
Innovation Solution
A capacitive sensor system with three electrodes, where the processing unit detects capacitance variations across two electrodes while one remains fixed, ensuring user intent is confirmed, and differentiates user action from water projection by ensuring a hand only covers a limited number of electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a capacitive sensor is used to detect user hand approach for door locking/unlocking, then convenience of operation is improved, but reliability deteriorates due to false triggering by water projection
Solution Approach 1:
The capacitive sensor is divided into three separate electrodes arranged in a triangular pattern, allowing the system to analyze capacitance variations across multiple discrete sensing points rather than a single aggregated sensor, enabling differentiation between water projection and hand approach
Solution Approach 2:
Different regions of the sensor surface (different electrodes) are given different spatial positions and sensitivities, with the processing unit analyzing local capacitance variations at each electrode to determine the nature of the approaching object based on the spatial distribution pattern
2Ease of operation
If a capacitive sensor detects any capacitance variation to trigger door action, then ease of operation is improved, but measurement precision deteriorates due to inability to distinguish water from hand
Solution Approach 1:
The sensor is segmented into three electrodes that independently measure capacitance variations, allowing the processing unit to compare patterns across multiple measurement points to accurately identify hand approach versus water projection based on the distinct spatial distribution characteristics of each
Solution Approach 2:
The processing unit continuously monitors capacitance variations across all three electrodes and uses this feedback information to determine whether the detected object is a hand or water, only triggering the door locking/unlocking action when the pattern matches hand approach 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
Prevents unintended locking or unlocking by accurately distinguishing between user hand approaches and water effects, ensuring secure and reliable door operation.
Implementation Method 1
a capacitive sensor to detect a hand or a finger of a user of the vehicle. As the human body is made up of two thirds of water, the approach of the user's finger or hand towards the capacitive sensor varies its capacity.
Implementation Method 2
the projection of a mass of water on the door, for example during a rain shower or washing the vehicle, can be interpreted by the capacitive sensor as an action of the user and triggers the locking or unlocking of the sash inadvertently. This is explained by the resemblance of the electrical effects induced.
Data Source
Figure 1~4
AI summary
The invention relates to a device for triggering an action on an opening panel of a motor vehicle. The device (1) comprises in particular: a capacitive sensor (C) for detecting a variation in capacitance, comprising at least three electrodes (E1, E2, E3), said at least three electrodes (E1, E2, E3) forming a detection pattern (M); and a processing unit (2) connected to the capacitive sensor (C) for processing output signals from the capacitive sensor (C), said output signals being representative of the capacitance of each of the electrodes (E1, E2, E3). The triggering device (1) is characterised in that: the positioning of the electrodes (E1, E2, E3) is defined such that at least one of the electrodes (E1, E2, E3) is not covered by a hand approaching the detection pattern (M), and the processing unit (2) is designed to perform a triggering action on the opening panel of the motor vehicle when a hand approaches said detection pattern (M).