Capacitive occupant detection system with interference detection
First Claim
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.
1 Assignment
0 Petitions
Accused Products
Abstract
A capacitive occupant detection system (10) comprises a sine signal generator (12) to apply a sine voltage signal to an antenna electrode (14) and a current measurement circuit (18, 20, 28, 30, 40) to measure current signals, based upon which a control and evaluation unit determines and outputs an occupancy state. The signal generator (12) is coupled to the antenna electrode via an amplitude adjustment stage (13), 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. The control and evaluation circuit selects one of the discrete amplitudes at a time and causes the amplitude adjustment stage to adjust the amplitude of said the voltage signal applied to the antenna electrode accordingly. The control and evaluation circuit carries out an interference detection mode and an occupant detection mode. In interference detection mode, the current signals are measured while a low one of the at least two discrete amplitudes is selected and it is determined whether the antenna electrode is exposed to interference. In occupant detection mode, the current signals are measured while a high one of the at least two discrete amplitudes is selected and occupancy state is determined based upon the current signals thus measured.
23 Citations
15 Claims
-
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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. Capacitive occupant detection method, comprising:
-
generating a sine voltage signal and applying said sine voltage signal to an antenna electrode; measuring 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, wherein said first current component is in phase with said sine voltage signal and said second current component is 90-degrees-phase-offset with respect to said sine voltage signal; determining an occupancy state based upon said measured current signals; and outputting an output signal indicative of said occupancy state determined; said method further including adjusting the amplitude of said sine voltage signal applied to said antenna electrode to an amplitude selected among at least two discrete amplitudes; wherein one of said at least two discrete amplitudes is selected at a time to carry out at least an interference detection mode and an occupant detection mode, respectively, 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, 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. - View Dependent Claims (14, 15)
-
Specification