Capacitive passenger detection utilizing dielectric dispersion in human tissues

Occupant detection in vehicles is an application of particular importance for capacitive sensors. Information about the presence and behaviour of the passengers can help to improve automotive safety, for example by firing off airbags in an optimal way. This paper details the idea of sensing dielectric dispersion effects of biological tissues and utilizing these for occupant detection. This sensing principle allows us to design occupant detectors which are very sensitive to the presence of biological tissue, i.e. to seated passengers. An innovative impedance modeling approach is discussed which combines effects of electromagnetic field interactions with different sorts of tissue and with the automotive sensor environment. It is shown that the implementation of the passenger impedance model in an occupant detector provides an insight into model parameters and maximizes the amount of detector information.