Seat Cushion Pressure Sensor Grid for Reliable Occupant Weight Sensing
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Solution Overview
Problem
Existing pressure sensing systems in vehicle seats have limited resolution due to the size and number of sensors, leading to unreliable weight measurements of occupants, especially when they shift or sit out of normal positions.
Innovation Solution
A pressure sensing system with a layer of electrically conductive foam and a flexible printed circuit, where horizontal and vertical sensing wires intersect to form multiple intersections, each acting as a pressure sensor, providing improved resolution and integration within the seat cushion to reduce mechanical stress and aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing sensors are used in the pressure sensing system, then the device structure is simple, but the sensing resolution is low and measurement precision is poor
Solution Approach 1:
The sensing system is segmented into multiple intersections formed by horizontal and vertical sensing wires. Each intersection acts as an independent pressure sensing unit, allowing the system to achieve high resolution through multiple distributed measurement points rather than using fewer large sensors.
Solution Approach 2:
The patent transitions from one-dimensional linear sensor arrays to a two-dimensional grid structure formed by intersecting horizontal and vertical wires. This dimensional change enables significantly higher sensing resolution across the seat surface while maintaining a relatively simple overall device structure.
2Measurement precision
If the number of sensors is increased to improve resolution, then the sensing resolution improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Multiple sensing functions are merged into a single integrated flexible printed circuit board. The horizontal and vertical sensing wires are combined on one substrate, forming multiple intersections that all function as pressure sensors. This merging approach enables high-resolution sensing while simplifying manufacturing compared to assembling numerous discrete sensors.
Solution Approach 2:
The flexible printed circuit board serves multiple functions simultaneously: it provides structural support, conducts electrical signals through its wire network, and creates the sensing intersections. This multi-functionality reduces the number of separate components needed, easing manufacturing while achieving high resolution.
3Reliability
If sensors are placed on the seat surface, then the sensing function is achieved, but relative movement causes mechanical stress and reduces reliability
Solution Approach 1:
The sensing system is merged with the seat cushion foam through insert-molding integration. The flexible printed circuit board with its sensing wire network is embedded within the foam structure, creating a unified assembly that eliminates relative movement between sensors and cushion, thereby reducing mechanical stress and improving reliability.
4Reliability
If a small number of large sensors are used, then the device complexity is low, but the reliability of weight measurement is poor when occupant position changes
Solution Approach 1:
The weight measurement function is segmented across multiple intersection points distributed throughout the seat surface. When an occupant shifts position, multiple segmented sensing points continue to provide data, ensuring reliable weight measurement regardless of occupant position. This segmentation approach simultaneously improves both reliability and measurement precision.
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 achieves higher sensing resolution and reliability in measuring occupant weight and distribution by generating real-time electric flux density values at each intersection, improving the accuracy of weight classification and airbag deployment decisions.
Implementation Method 1
When a pressure is applied to the layer of the electrically conductive foam, each intersection generates in real time an electric flux density value to reflect a degree of a compression caused by the pressure to a corresponding point of the electrically conductive foam
Data Source
AI summary
A pressure sensing system (24), seat cushion (20) incorporating the pressure sensing system, and method of sensing a weight group associated with an occupant of an automotive seat are described. The pressure sensing system includes a layer of an electrically conductive foam (28) and a flexible printed circuit (26) that includes a flexible substrate (26a) and N horizontal sensing wires (26b) and M vertical sensing wires (26c) securely placed on a top surface of the flexible substrate. The horizontal sensing wires intersect with the vertical sensing wires and form N×M intersections. The layer of an electrically conductive foam is placed on top of the N horizontal sensing wires and the M vertical sensing wires. When a pressure is applied to the layer of the electrically conductive foam, each intersection generates in real time an electric flux density value to reflect a degree of a compression caused by the pressure to a corresponding point of the electrically conductive foam.