Dual Electrode Occupant Detection System for Humidity Compensation
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Solution Overview
Problem
Occupant detection systems using electric fields face interference from environmental conditions like humidity, leading to inaccurate distinctions between 'Allow airbag deployment' and 'Inhibit airbag deployment' signals, potentially mischaracterizing occupants, especially in the presence of seat-heaters, and adding humidity sensors increases system cost.
Innovation Solution
A dual-electrode system with a first and second electrode, each generating signals based on excitation signals and occupant proximity, using high and low frequency signals applied selectively to one or both electrodes, and a controller determines occupant presence by analyzing these signals to compensate for environmental variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrode is used for occupant detection, then the system structure is simple, but environmental conditions like humidity interfere with detection accuracy
Solution Approach 1:
The single electrode is divided into two separate electrodes (first electrode and second electrode) with different geometries and positions. This segmentation allows each electrode to have distinct sensitivity characteristics to environmental factors, enabling the system to differentiate between humidity effects and actual occupant presence through comparative analysis of their respective signals.
Solution Approach 2:
The first and second electrodes are designed with different local qualities - different areas, shapes, and positions within the seat assembly. The first electrode has a larger area while the second electrode has a smaller area, creating different electric field distributions. This local quality differentiation makes each electrode respond differently to environmental conditions, providing redundant information for accurate occupant detection despite humidity interference.
2Reliability
If driven shield layers are added to increase separation between 'Allow' and 'Inhibit' conditions, then detection reliability improves, but device complexity and cost increase
Solution Approach 1:
Instead of adding driven shield layers, the patent changes the parameters of the electrodes themselves - specifically their areas, shapes, and positions. By optimizing these geometric parameters, the system achieves sufficient signal separation between 'Allow' and 'Inhibit' conditions using only two simple electrodes, avoiding the complexity of driven shield structures while maintaining reliable detection.
3Measurement precision
If a humidity sensor is added to compensate for environmental interference, then detection accuracy improves, but system cost increases
Solution Approach 1:
The system uses its own detection electrodes to self-compensate for environmental interference. By comparing the signals from the first and second electrodes, which have different sensitivities to humidity, the system can mathematically differentiate between humidity-induced signal changes and actual occupant presence, eliminating the need for separate humidity sensors while achieving environmental compensation.
Solution Approach 2:
The first and second electrodes serve multiple functions: they detect occupant presence, characterize occupant type (child/adult), and simultaneously provide environmental condition information through their differential responses. This multi-functionality eliminates the need for dedicated environmental sensors, reducing system cost and complexity while maintaining detection accuracy.
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 provides accurate and reliable occupant presence detection, reducing mischaracterization and environmental interference without the need for additional humidity sensors, thus maintaining system cost-effectiveness.
Implementation Method 1
occupant detection systems that use an electrode located proximate to a seating surface to radiate an electric field and thereby detect occupant presence
Implementation Method 2
The first electrode is configured to generate an electrode signal having a signal value dependent on an excitation signal applied to the first electrode and a proximity of the occupant
Data Source
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AI summary
A dual-electrode occupant (12) detection system (10) configured to determine an occupant (12) presence on a seat assembly (32). The system (10) includes two electrodes (20, 28) that each generates an electric field in response to an applied excitation signal (50). The two electrode signals arising therefrom can be measured individually and/or combined to detect more reliably an occupant (12). Such a configuration advantageously avoids the added expense and complication of an electrode arrangement that relies on an underlying shield layer to reduce electrode signal (24) degradation caused by a seat heater element.