Resonant Frequency Occupant Detection Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing occupant detection systems in vehicles are adversely affected by varying humidity levels, leading to inaccurate measurements, especially when the seat is wet, which can result in unreliable detection of an occupant's presence.
Innovation Solution
A system utilizing an electrode and an electrical network configured as a resonant circuit, where the resonant frequency is indicative of an occupant's presence, and the network signal magnitude at this frequency provides information about humidity levels, allowing for accurate detection regardless of environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric field impedance measurement is used for occupant detection, then occupant presence can be detected, but measurement accuracy deteriorates under varying humidity conditions
Solution Approach 1:
The patent changes the measurement parameter from electric field impedance to resonant frequency. The resonant frequency of the RC circuit is determined by the capacitance of the electrode-occupant system and the resistance of the circuit, but is independent of humidity-induced resistance changes in the seat materials. This parameter transformation eliminates humidity interference while maintaining occupant detection capability.
Solution Approach 2:
The patent replaces the traditional electric field impedance measurement system with a resonant frequency measurement system. By using an RC circuit where the resonant frequency depends on capacitance rather than resistance, the system substitutes a measurement method that is inherently insensitive to humidity effects, thereby resolving the contradiction between detection accuracy and humidity sensitivity.
2Reliability
If traditional impedance measurement is used, then occupant detection is possible, but reliability deteriorates when liquid is present on the seat
Solution Approach 1:
The patent transforms the measurement from impedance-based to resonant frequency-based. When liquid is present on the seat, it affects the resistance and dielectric properties, but the resonant frequency of the RC circuit remains stable because it is primarily determined by the capacitance of the electrode-occupant system, which is less affected by surface liquid contamination.
3Ease of operation
If electric field impedance measurement is used, then occupant presence can be detected, but the system becomes sensitive to environmental humidity variations
Solution Approach 1:
The patent changes the measured parameter from electric field impedance to resonant frequency of an RC circuit. This parameter change maintains the simplicity of the detection method while eliminating environmental sensitivity, as resonant frequency is determined by circuit components (capacitance and resistance) rather than environmental conditions like humidity.
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 effectively determines the presence of an occupant and humidity levels independently, ensuring reliable operation even in wet conditions, thereby enabling precise control of airbag deployment and other vehicle features.
Implementation Method 1
detecting a resonant frequency arising in response to the excitation signal
Implementation Method 2
measuring an electric field impedance about the electrode
Data Source
AI summary
An occupant detection system that includes an electrode arranged proximate to an expected location of an occupant for generating an electric field between the electrode and the occupant proximate thereto. An electrical network coupled to the electrode forms a resonant circuit that includes the occupant as part of the resonant circuit. A controller coupled to the resonant circuit is configured to determine a resonant frequency of the resonant circuit indicative of an occupant presence, and a network signal magnitude at the resonant frequency indicative of a humidity value proximate to the electrode. 7. A method for detecting a vehicle applies an excitation signal to the resonant circuit, determine a resonant frequency of the resonant circuit and determines a humidity value based on a network signal magnitude at the resonant frequency.