Method and system for detecting an occupant in a vehicle seat

摘要

An occupant detection system comprises an electrode arrangement for placement into a seat of an automotive vehicle and an evaluation circuit operatively connected to the electrode arrangement. The latter includes a first electrode, a second electrode and an electric insulator layer sandwiched between the first and second electrodes. When the electrode arrangement is in place in the seat, the first electrode forms with vehicle ground a first capacitor having a first capacitance, the first electrode forms with the second electrode a second capacitor having a second capacitance and the second electrode forms a first plate of a third capacitor having a third capacitance. As a first indicator of the seat occupancy state, a measure of the first capacitance is determined while the second electrode is operated as a driven shield for the first electrode. The fluctuations of at least one of the first, second and third capacitances are measured and the frequency spectrum of the measured fluctuations is analysed, which yields a second indicator of the occupancy state. The derivation of the occupancy state of the seat is then based on both the first indicator and the second indicator.