Capacitance Seat Occupancy Sensor Using Near and Far Fields
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Solution Overview
Problem
Existing capacity-based systems for detecting vehicle seat occupancy, particularly those used in the USA to differentiate between child seats and adult occupants, face issues with seating comfort, sensor design restrictions, and service life, due to sensor placement below the seat cover and above the seat foam, and are influenced by environmental factors like humidity and temperature.
Innovation Solution
A capacitance-based system with transmitting and receiving electrode arrangements placed on the underside of the seat foam, utilizing electric near and far fields to distinguish between occupancy states, with the control and evaluation device determining the occupancy status based on the field strengths and their ratios, and optionally incorporating eddy current measurements for metal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor is arranged below the seat cover and above the seat foam, then the occupancy status can be detected, but the seating comfort is affected and the design of the seat cover and seat foam is restricted
Solution Approach 1:
The patent moves the sensor arrangement from a traditional single-plane location (below seat cover, above seat foam) to a new dimensional configuration by placing electrodes on the underside of the seat foam, creating near fields and far fields that extend in different spatial dimensions. This dimensional change allows detection functionality while eliminating interference with seating comfort and design freedom.
Solution Approach 2:
The patent divides the detection system into separate near field and far field components, each serving different detection purposes. The near field (extending only into seat foam surface area) handles local occupancy detection, while the far field (extending significantly above seat foam surface) provides additional detection capability. This segmentation allows the system to distinguish between different occupancy states without compromising comfort or design.
2Reliability
If the sensor is arranged below the seat cover and above the seat foam, then the occupancy status can be detected, but the service life of the sensor is reduced
Solution Approach 1:
The patent extracts the sensor (electrodes) from the traditional location between seat cover and seat foam, and relocates them to the underside of the seat foam. This extraction removes the sensor from the harmful environment where it would be subject to compression, moisture, and mechanical stress, thereby extending its service life while maintaining detection functionality through the near field and far field configuration.
3Measurement precision
If environmental conditions such as humidity and temperature fluctuate, then the measurement result is influenced, but distinguishing between different occupancy states becomes difficult
Solution Approach 1:
The patent introduces the seat foam as an intermediary medium between the electrodes and the external environment. The electrodes are placed on the underside of the seat foam, which acts as a protective barrier against humidity and temperature fluctuations. The near field and far field configurations allow the system to detect occupancy states while the seat foam intermediary shields the sensors from environmental harmful factors, maintaining 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
This design provides a more reliable distinction between occupancy states, minimizes environmental influence, maintains seating comfort, and allows for flexible seat foam design, ensuring accurate differentiation without affecting the seat's functionality or increasing costs.
Implementation Method 1
between the transmission electrode arrangement and the reception electrode arrangement there is at least one electric near field that essentially only extends into the area of the seat foam surface
Implementation Method 2
at least one electric field, in particular significantly above the Area of the seat foam surface setting far-reaching electric field
Implementation Method 3
a capacity-based system for detecting the occupancy status of a vehicle seat
Implementation Method 4
changes in the capacitive coupling in the area of the seat foam, for example caused by penetrating moisture or water on the seat, etc., affect a particular near field
Implementation Method 5
optionally incorporating eddy current measurements for metal detection
Data Source
Figure 1~2
Figure 3~4
AI summary
A capacitance-based system for detecting the occupancy status of a vehicle seat comprises a transmitting electrode arrangement (32) and a receiving electrode arrangement (34) located on the underside of the seat foam (20). The transmitting electrode arrangement (32) is energized and its structure is selected such that at least one near field (22) extending substantially only to the area of the seat foam surface (20') and at least one far field (24) extending significantly beyond the area of the seat foam surface (20') are established between the transmitting electrode arrangement (32) and the receiving electrode arrangement (34).In addition, a control and/or evaluation device (26) is provided which detects a respective occupancy state depending on both the respective field strength of the at least one near field (22) and the respective field strength of the at least one fem field (24).