Patent ID: 8698511
Filing Date: 2014-04-15
Classification: B60N,B60R

Abstract:
1. A capacitive occupant detection system, comprising: an antenna electrode; a sine signal generator configured to generate a sine voltage signal, said sine signal generator being operatively coupled to said antenna electrode to apply said sine voltage signal to said antenna electrode, a current measurement circuit configured to measure current signals, said current signals comprising amplitude and phase of a current flowing in said antenna electrode or in a separate sensing electrode, or a first and a second current component of said current, with said first and second current components being out of phase with one another by a phase difference which is not 180° or an integer multiple thereof; a control and evaluation unit operatively coupled to said current measurement circuit to determine an occupancy state based upon said measured current signals, and to output an output signal indicative of said occupancy state determined; wherein said sine signal generator is operatively coupled to said antenna electrode via an amplitude adjustment stage, configured to adjust the amplitude of said sine voltage signal applied to said antenna electrode to an amplitude selected among at least two discrete amplitudes; wherein said amplitude adjustment stage is operatively connected to said control and evaluation circuit; and wherein said control and evaluation circuit is configured to select one of said at least two discrete amplitudes at a time and to cause said amplitude adjustment stage to adjust the amplitude of said sine voltage signal applied to said antenna electrode to said selected amplitude; said control and evaluation circuit being configured to carry out an interference detection mode, said interference detection mode comprising measuring said current signals while a low one of said at least two discrete amplitudes is selected and determining whether said antenna electrode or said separate sensing electrode is exposed to interference, and an occupant detection mode, said occupant detection mode comprising measuring said current signals while a high one of said at least two discrete amplitudes is selected, determining said occupancy state based upon said current signals measured during said occupant detection mode and outputting said output signal indicative of said occupancy state determined.