Capacitive Seat Back Sensor for Occupant Classification
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Solution Overview
Problem
Current seat occupant classification systems rely on weight or pressure measurements, which are inefficient in differentiating between conductive objects and occupants, leading to unnecessary costs and potential system activation errors.
Innovation Solution
A capacitive or electric field-based system using separate electrodes in the seat back and bottom, with a controller and microprocessor to analyze impedance measurements, allowing for precise differentiation between occupants and objects by utilizing both in-phase and quadrature components of the current, and optionally integrating heating elements for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If weight or pressure measurements are used to differentiate occupants from objects, then object presence detection is achieved, but measurement precision deteriorates due to inability to distinguish conductive objects from occupants
Solution Approach 1:
The patent replaces mechanical weight/pressure measurement systems with a capacitive sensing system. The capacitive sensor detects changes in electrical capacitance caused by the presence of occupants versus objects, enabling more precise classification without relying on force-based measurements. This substitution fundamentally changes the measurement principle from mechanical to electrical field-based detection.
Solution Approach 2:
The patent changes the measurement parameter from weight/pressure to capacitance. By measuring electrical capacitance changes in the seat structure when occupants or objects are present, the system achieves better differentiation capability. The capacitive measurement parameter provides distinct signal characteristics for different types of objects, improving classification precision.
2Reliability
If weight-based measurement systems are implemented, then occupant detection is achieved, but device complexity increases due to additional sensors and calibration requirements
Solution Approach 1:
The capacitive sensor serves multiple functions simultaneously: it detects occupant presence, classifies occupant type (adult, child, object), and provides signals for both safety system activation and energy management. This multi-functionality reduces the need for separate sensor systems, thereby reducing overall device complexity while maintaining reliable detection capability.
Solution Approach 2:
The capacitive sensing system utilizes the seat's existing electrical structure and grounding system, eliminating the need for separate dedicated sensor housings or complex mounting structures. The sensor leverages the seat's own electrical properties and the natural capacitance changes caused by occupancy, reducing the complexity of sensor integration and system installation.
3Measurement precision
If capacitive sensors are used in the seat back, then measurement precision improves for occupant classification, but device complexity increases due to additional sensor locations
Solution Approach 1:
The patent adds a spatial dimension to the sensing system by placing capacitive sensors in the seat back in addition to the seat cushion. This creates a multi-zone detection system that measures capacitance changes at different locations, providing more information for accurate occupant classification. The seat back sensor detects objects that may rest on the backrest, complementing the cushion sensor.
Solution Approach 2:
The sensing system is segmented into multiple independent capacitive sensing zones: the seat cushion area and the seat back area. Each zone can independently detect capacitance changes, and the controller processes signals from both zones to make classification decisions. This segmentation allows the system to detect objects in different positions and improves overall 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 accurate classification of seat occupants, reducing false positives and unnecessary system activations, and providing more precise instructions to safety systems like airbag deployment and seat belt reminders, enhancing vehicle safety and reducing costs associated with weight-based measurement systems.
Implementation Method 1
a capacitive or electric field based occupant classification systems for automobile seats
Implementation Method 2
A capacitive or electric field-based system using separate electrodes in the seat back and bottom, with a controller and microprocessor to analyze impedance measurements
Data Source
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AI summary
A classification system for determining the occupancy state of a seat of a vehicle. The classification system includes a first sensing electrode located in a back portion of the seat and a a second sensing electrode located in a base portion of the seat. The system includes a measurement circuit configured to measure a first property associated with the first sensing electrode and a second property associated with the second electrode. A controller is configured to send an occupancy signal indicative of the occupancy state of the seat based on the measured properties associated with the first and second sensing electrodes. The controller may be configured to send the occupancy signal to a Seat Belt Reminder (SBR) system.