Capacitance Sensor with Reducing Electrode for Occupant Detection
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Solution Overview
Problem
Existing capacitance-based sensors in vehicle seats face accuracy issues in determining the occupant state due to variations in the measured capacitance caused by differences in seat size and material, leading to inaccurate air bag deployment decisions.
Innovation Solution
The implementation of a capacitance-based sensor system with an occupant sensing electrode, an empty seat capacitance reducing electrode, and an electric current sensing device, which includes a dielectric layer and a drive device to reduce the empty seat capacitance, allowing for precise occupant detection by isolating the capacitance generated through the human body from the existing empty seat capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance-based sensor measures the total capacitance between the occupant sensing electrode and vehicle ground, then the sensor can detect the presence of an occupant, but the measurement includes both the occupant-generated capacitance and the empty seat capacitance, causing variations in measurement accuracy
Solution Approach 1:
The patent divides the capacitance measurement into two separate components: the empty seat capacitance (Co) measured when no occupant is present, and the occupant-generated capacitance (Cb) measured when an occupant is present. By segmenting the measurement process and subtracting Co from the total capacitance, the system isolates the actual occupant signal, thereby improving measurement precision and reliability.
Solution Approach 2:
The patent extracts and removes the empty seat capacitance component from the total capacitance measurement. By measuring Co separately and subtracting it from the total capacitance, the system eliminates the interfering empty seat capacitance effect, allowing for more accurate detection of the occupant's presence and characteristics.
2Measurement precision
If the empty seat capacitance is reduced by positioning the electric current sensing device between the occupant sensing electrode and the empty seat capacitance reducing electrode, then the measurement accuracy improves, but the device complexity increases
Solution Approach 1:
The patent introduces an empty seat capacitance reducing electrode as an intermediary element positioned between the occupant sensing electrode and the vehicle ground. This intermediary electrode helps to reduce the empty seat capacitance effect by providing a reference potential, thereby improving measurement accuracy without requiring complex external adjustment mechanisms.
Solution Approach 2:
The sensor system performs self-calibration by automatically measuring the empty seat capacitance Co during initialization and using this value to compensate for empty seat effects in subsequent measurements. This self-service approach eliminates the need for manual factory adjustments, reducing device complexity while maintaining high measurement precision.
3Adaptability or versatility
If multiple electrode configurations are used to cover various seating patterns, then the adaptability improves, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent designs the occupant sensing electrode and empty seat capacitance reducing electrode with large surface areas and strategic positioning to create a universal sensing field that can detect occupants in various seating positions and postures. This multi-functional electrode configuration covers diverse seating patterns without requiring multiple separate sensor systems, thereby maintaining adaptability while controlling device complexity.
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
This solution enhances the accuracy of occupant determination, reduces the need for factory adjustments, and ensures reliable air bag deployment decisions by effectively distinguishing between empty, CRS-installed, and occupied states, while minimizing noise interference and electrode damage.
Implementation Method 1
an electric field is created between the first electrode 512 and the second electrode 513
Implementation Method 2
a capacitance between the two electrodes of the capacitance-based sensor varies depending on the type of the interposed object
Implementation Method 3
the capacitance-based sensor senses a disturbance in a weak electric field generated by an electrode and outputs the sensed result as the corresponding electric current or electric voltage
Data Source
AI summary
An occupant sensing electrode is embedded in a seat. An empty seat capacitance reducing electrode is placed between the occupant sensing electrode and a seat frame of the seat in an opposed relationship to the occupant sensing electrode. A dielectric base film may be interposed between the occupant sensing electrode and the empty seat capacitance reducing electrode. The occupant sensing electrode may include a plurality of electrode portions. The electrode portions may include high potential electrode portions and low potential electrode portions.