Detection of Presence and Posture of Vehicle Occupants Using a Capacitance Sensing Mat 2019-01-1232
Capacitance sensing is the technology that detects the presence of nearby objects by measuring the changes in capacitance. A change in capacitance is triggered either by a change in the dielectric constant, area of overlap or the distance of separation between the electrodes of the capacitor. It is a technology that finds wide applications in touch screens, proximity sensing etc. Drawing motivation from such applications, this paper investigates how capacitive sensing can be employed to detect the presence and posture of occupants in vehicles. Compared to existing solutions, the proposed approach is low-cost, easy to deploy, and effective.
The sensing system comprises a capacitance-sensing mat which is embedded with copper foils that are arranged in rows and columns to form several touch-nodes across its surface. The system segregates row and column capacitances from each other and computes their tensor product to generate a grayscale capacitance-sensing image. The image is a pictorial representation of the capacitance at each touch-node. When the mat is placed on a vehicle seat and an occupant sits on it, there will be an increase in capacitance at those touch-nodes that are in contact with the occupant’s body. As a result, the capacitance-sensing image can capture the presence of occupants in the seat. In addition, through close observation of the image and feature analysis, it is also possible to identify the posture of the occupant in the seat, e.g., whether he or she is leaning backward or forward. The sensing system is implemented and tested on a vehicle seat and experimental results and analysis will be presented in this paper.
Rahul Prasanna Kumar, David Melcher, Pietro Buttolo, Yunyi Jia
Clemson University, Ford Motor Company