Vehicle Seat Occupancy Sensing With Interdigitated Capacitive Sensors
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Solution Overview
Problem
Existing seat occupancy detection systems in vehicles suffer from long response times, susceptibility to disturbances, and lack of robustness, making them unsuitable for real-time applications and long-term reliability, especially in critical situations like accidents.
Innovation Solution
A method using interdigitated capacitive sensors on a vehicle seat to measure capacitance values, calculate averages and differences, and compare against reference and threshold values to determine occupancy status, with additional features for morphological type and age classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If camera or motion sensor devices are used for seat occupancy detection, then the system can detect occupancy status, but the response time becomes too long (several seconds) for real-time safety applications
Solution Approach 1:
The patent replaces optical/mechanical detection systems (camera, motion sensor) with an electrical field-based capacitive sensing system. The interdigitated capacitive sensors detect changes in capacitance caused by the presence of an occupant's body, providing instantaneous electrical signals that enable real-time response without the delays inherent in optical or mechanical detection methods.
Solution Approach 2:
The patent changes the detection parameter from optical/mechanical measurements to electrical capacitance measurements. By measuring capacitance values and their variations across multiple interdigitated sensors, the system achieves rapid detection of occupancy status and can distinguish between different occupant types (adult, child, empty seat) based on capacitance characteristics.
2Measurement precision
If camera or motion sensor devices are used for seat occupancy detection, then occupancy status can be determined, but the measurements become highly susceptible to disturbances and exhibit drift over time
Solution Approach 1:
The patent divides the detection system into multiple independent interdigitated capacitive sensors arranged in a grid pattern across the seat surface. Each sensor provides an independent capacitance measurement, and the system analyzes the pattern of measurements across all sensors to determine occupancy status. This segmentation provides redundancy and robustness against individual sensor disturbances or drift.
Solution Approach 2:
The patent implements a measurement and comparison process where capacitance values are continuously measured, compared against reference values stored in memory, and used to determine occupancy status. The system can adapt to gradual drift by using reference measurements taken at different times and comparing relative changes, providing long-term stability.
3Loss of information
If non-interdigitated capacitive sensors are used, then the system structure is simpler, but the ability to determine detailed occupancy information and morphological characteristics is reduced
Solution Approach 1:
The patent uses multiple interdigitated capacitive sensors arranged in specific patterns (e.g., three rows of two sensors each) across different zones of the seat (seat cushion, backrest). This segmented arrangement allows the system to detect not only occupancy presence but also determine occupant position, posture, and morphological characteristics by analyzing the spatial distribution of capacitance changes across the sensor array.
Solution Approach 2:
The interdigitated capacitive sensor configuration serves multiple functions simultaneously: detecting occupancy presence, determining occupant type (adult/child/empty), assessing occupant position and posture, and providing robust measurements resistant to disturbances. This multi-functionality is achieved through the specific interdigitated electrode geometry and arrangement, which creates sensitive electrical field patterns for comprehensive occupancy analysis.
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
Provides rapid, reliable, and robust determination of seat occupancy, enabling real-time adaptation of safety systems like airbags and seat belt pretensioners, with improved accuracy and long-term reliability.
Implementation Method 1
at least six interdigitated capacitive sensors carried by the seat... measuring at least three capacitance values by each interdigitated capacitive sensor
Data Source
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AI summary
The invention relates to a method for determining the occupancy status of a seat in a motor vehicle, the method being implemented by a determination system comprising a seat, six interdigitated capacitive sensors and a controller comprising a reference capacitance value and a threshold value for each interdigitated capacitive sensor, the method comprising a step of measuring three capacitance values for each interdigitated capacitive sensor, the following steps being implemented by the controller for the measured capacitance values: - calculation (46) of a resulting capacitance value from the measured capacitance values, - calculation (48) of the difference between the resulting capacitance value and the reference capacitance value, - comparison (49) of the calculated difference to the threshold value, - determination (50, 52, 56) of the occupancy status of the seat as a function of the result of the comparison.