Capacitive Door-Edge Sensing for Small-Object Jam Detection
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Solution Overview
Problem
Existing capacitive jam protection systems for dual doors are insensitive to small objects, such as fingers, due to interference from opposing door signals, making it difficult to detect human presence effectively.
Innovation Solution
A capacitive sensor system with two movable sensors, each integrated into a door section, uses different measurement modes to differentiate between signal attenuation caused by objects and environmental interference, allowing for higher sensitivity and accurate detection of objects between doors, even when doors are close.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single capacitive sensor with shield is used in each door section, then the device structure is simple and easy to manufacture, but the sensitivity to detect small objects is insufficient due to signal interference from opposing doors
Solution Approach 1:
The sensor system is segmented into two distinct capacitive sensors (first sensor and second sensor) positioned in opposite door sections. Each sensor independently measures signal attenuation, allowing the system to differentiate between interference from opposing doors and actual objects by comparing measurements from both sensors.
Solution Approach 2:
The patent combines the measurements from both the first sensor and second sensor to achieve accurate object detection. By merging the data from both sensors and analyzing the difference in signal attenuation, the system achieves high sensitivity while maintaining a relatively simple overall structure.
2Reliability
If both doors are close to each other during closing, then the door closure function is achieved, but the signal from one door directly influences the other making detection insensitive
Solution Approach 1:
Each sensor is configured to measure signal attenuation locally in its respective door section. The first sensor measures attenuation in the first door section while the second sensor measures attenuation in the second door section. This localized measurement approach allows the system to distinguish between signal changes caused by door proximity versus those caused by objects.
Solution Approach 2:
The control unit continuously monitors and compares the measurements from both sensors. By analyzing the feedback from both sensors simultaneously, the system can adaptively determine when signal attenuation is caused by door closure versus when it indicates the presence of an object, maintaining reliable detection even during door closing operations.
3Area of stationary object
If a long sensor covering the whole door edge is used, then the detection coverage is complete, but the sensor is more susceptible to interference and harder to integrate into standard door sealing
Solution Approach 1:
Instead of using a single long sensor, the patent divides the detection function into two separate sensors positioned in opposite door sections. Each sensor can be a shorter, more manageable length that is easier to integrate into standard door sealing structures, while collectively providing complete detection coverage through their combined measurement capability.
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 system achieves enhanced sensitivity in detecting objects between dual doors by correlating signal attenuations from two measurement modes, enabling reliable detection of human presence and door position, thus preventing jamming and improving safety.
Implementation Method 1
a capacitive sensor which comprises a signal line and a reference conductor, wherein the signal line and the reference conductor are insulated and distant from each other
Implementation Method 2
an electrical shield is provided to reduce effects of the window on the electrical field of the conductor
Data Source
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AI summary
Device for detecting the presence of an object close to or within an door opening defined by two door sections comprising at least one sensor at each door sec- tion. Each sensor comprising at least one reference conductor and at least one sensing line insulated and distant from the at least one reference conductor. The at least one sensing line being connected to an amplifier generating an output signal indicating the signal strength and/or attenuation of a signal at the at least one sensing line. A control circuit is provided, further comprising a signal genera- tor and a switch unit having at least a first output and a second output, whereas in a first measurement mode A, the first output is connected to the signal gener- ator and the second output is connected to ground, and in a second measure- ment mode B, the first output is connected to ground and the second output is connected to the signal generator. An evaluation unit is provided for correlating an output signal measured in mode A with an output signal measured in mode B.