Capacitive Occupant Sensor with Load-Dependent Antenna Area
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Solution Overview
Problem
Vehicle seat occupant detection systems based on capacitive sensors face challenges in correctly classifying seat occupancy, particularly with vehicle-grounded objects like electric devices or child restraint seats, due to misclassification caused by changes in electric fields and capacitance measurements.
Innovation Solution
A capacitive sensor member with a first and second electrically conductive antenna member, an electrically conductive bridging member, and an elastic spacer, where the bridging member provides galvanic contact only when a mechanical load exceeds a predetermined value, distinguishing between adult occupants and grounded objects by varying capacitance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If capacitive sensors are used for seat occupancy detection, then the system achieves easy integration and field robustness, but misclassification occurs with vehicle-grounded objects due to electric field changes
Solution Approach 1:
The patent applies the dynamics principle by making the antenna area dynamically adjustable through elastic spacer members that compress under mechanical load. When a sufficient load is detected, the spacers compress to allow conductive bridging members to contact the antenna, thereby increasing the antenna area. This dynamic adjustment enables the system to differentiate between grounded objects (no significant load) and actual occupants (significant load), resolving the misclassification issue while maintaining ease of integration
Solution Approach 2:
The patent changes the physical parameter of antenna area based on mechanical load conditions. By using elastic spacer members with specific stiffness and conductive bridging members, the system transitions the antenna from a smaller initial area to a larger area when load is applied. This parameter change allows the capacitive sensor to adapt its sensitivity and measurement characteristics based on the presence of an occupant versus a grounded object, improving classification accuracy
2Measurement precision
If mechanical load sensors are added to distinguish occupants from grounded objects, then occupancy classification accuracy improves, but device complexity and costs increase
Solution Approach 1:
The patent merges the functions of capacitive sensing and mechanical load detection into a single integrated system. The elastic spacer members serve dual purposes: they are structural components of the capacitive sensor assembly and simultaneously function as mechanical load sensors through their compression characteristics. The conductive bridging members provide both electrical connection and load-dependent activation. This merging eliminates the need for separate mechanical load sensors, reducing device complexity and costs while maintaining improved occupancy classification 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
Enables reliable classification of seat occupancy by differentiating between adult occupants and grounded objects, such as electric devices or ISOFIX child restraint seats, without the need for additional mechanical load sensors, improving accuracy and reducing hardware complexity and costs.
Implementation Method 1
at least one elastic spacer member that has elastic mechanical properties at least in the specified direction
Implementation Method 2
a first electrically conductive antenna member that is electrically connectable to a capacitance measurement circuit for determining a capacitance of the capacitive sensor member
Data Source
AI summary
A capacitive sensor member of a vehicle seat occupant detection and classification device that includes a first electrically conductive antenna member and at least a second electrically conductive antenna member that is adjacently arranged to the first electrically conductive antenna member without any mutual galvanic connection. At least one electrically conductive bridging member is fixedly attached to at least one elastic spacer member that has elastic mechanical properties in a specified direction. If a mechanical load is applied to the capacitive sensor member in the specified direction that is equal to or larger than a predetermined value for the mechanical load, the at least one electrically conductive bridging member provides at least one galvanic contact between the first electrically conductive antenna member and the second electrically conductive antenna member.