Capacitive Sensor Resonant Network Frequency Control
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Solution Overview
Problem
Capacitive sensing systems for vehicle seats face challenges in accurately determining occupancy without interfering with electromagnetic radiation levels and avoiding electromagnetic interference, particularly when the resonance frequency varies over a large range, which can exceed critical frequency bands and cause interference with other electronic devices.
Innovation Solution
A capacitive sensor system that includes a resonant network with a heating element acting as an antenna electrode, using a capacitive sensing network with reactive components that can be activated or deactivated to adjust the resonance frequency within a narrow band, allowing for direct comparison of capacitance and resistance values and minimizing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the resonance frequency is allowed to vary over a large range, then the capacitive sensing system can operate across different conditions and adaptability is improved, but electromagnetic interference with other electronic devices increases and radiation standards may be exceeded
Solution Approach 1:
The patent implements dynamic frequency selection by providing multiple resonant circuits with different resonance frequencies and selectively activating them based on operating conditions. The control unit dynamically switches between frequency bands to maintain compliance with electromagnetic radiation standards while adapting to different sensing requirements, thus resolving the contradiction between adaptability and electromagnetic interference.
Solution Approach 2:
The system changes the operating frequency parameter by selecting from multiple predefined resonance frequencies. By adjusting this key parameter based on the detected environment and occupancy conditions, the system achieves adaptability without continuously varying frequency, thereby limiting electromagnetic interference to acceptable levels while maintaining versatility.
2Object-generated harmful factors
If the resonance frequency is confined within a narrow band, then electromagnetic interference is reduced and radiation compliance is improved, but measurement accuracy may be affected due to limited frequency adjustment capability
Solution Approach 1:
The patent segments the frequency spectrum into multiple discrete narrow bands, each with its own resonant circuit. By dividing the overall frequency range into separate segments and selecting appropriate segments for different measurement conditions, the system maintains narrow band operation for interference compliance while achieving accurate measurements through selective frequency matching.
Solution Approach 2:
The control unit employs feedback mechanisms to monitor measurement quality and select the optimal resonant frequency from available options. Based on feedback regarding signal quality, occupancy detection results, and environmental conditions, the system adjusts frequency selection to maintain measurement precision within the constrained narrow frequency bands.
3Adaptability or versatility
If multiple reactive components are used to adjust resonance frequency, then frequency control flexibility is improved, but device complexity increases
Solution Approach 1:
The system achieves frequency control flexibility through dynamic switching between predefined resonant circuits rather than continuously adjusting individual reactive components. This dynamic approach provides adaptability while avoiding the complexity of real-time component adjustment mechanisms.
Solution Approach 2:
Each resonant circuit is designed to serve multiple functions: frequency selection, signal generation, and measurement. By making the resonant circuits multi-functional, the system reduces the need for separate frequency adjustment components, thereby achieving frequency control flexibility without proportionally increasing 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
The system effectively determines occupancy by confining the resonance frequency within a narrow band, reducing electromagnetic interference and ensuring compliance with radiation standards, while maintaining accurate measurements.
Implementation Method 1
a heating element (10) connected between a first node (21) and a second node (22) to dissipate heat when a heating current is caused to flow between the first and second nodes, across the heating element
Implementation Method 2
the heating element (10) is operated as a sensing antenna electrode that is capacitively coupled to a counterelectrode to form a capacitance
Implementation Method 3
the capacitive sensing network (30) includes at least one inductor (16, 236.1-236.4) and a plurality of reactive components (36) arranged to form a resonant network with the capacitance
Data Source
AI summary
A capacitive sensor includes a sensing antenna electrode for capacitively coupling to a counterelectrode to form a capacitance, this capacitance being responsive to an electric-field-influencing property of an object or person proximate to the antenna electrode. The counterelectrode may be part of the capacitive sensor. The capacitive sensor also includes a capacitive sensing network connected to the antenna electrode to apply an oscillating signal thereto and to determine the capacitance based upon characteristics of the oscillating signal. The capacitive sensing network includes at least one inductor and a plurality of reactive components arranged to form a resonant network together with the capacitance, the plurality of reactive components being activatable and deactivatable in such a way as to modify a resonance frequency of the resonant network.