Occupant detection system and method of determining occupant

Abstract

An occupant detection system for detecting an occupant on a seat of a vehicle includes an antenna electrode in a seat bottom of the seat, and an electronic unit connected to the antenna electrode and the vehicle. The electronic unit applies a load current to the antenna electrode so as to generate a weak electric field, and detects a potential current passing through the antenna electrode. The electronic unit detects an occupant based on an impedance and a phase difference, which are based on the load current and the potential current.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a side view showing a seat having an occupant detection system according to a first embodiment of the present invention;

FIG. 2 is a plan view of a seat bottom of the seat in FIG. 1;

FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2;

FIG. 4 is a diagram showing a remote detection of the system;

FIG. 5 is a diagram showing a proximity detection of the system;

FIG. 6 is a graph showing a relationship between a phase difference and an impedance for the remote detection;

FIG. 7 is a graph showing a relationship between a phase difference and an impedance for the proximity detection;

FIG. 8 is a flow chart of occupant detection in the first embodiment;

FIG. 9 is a graph showing a relationship between a conductance and a susceptance for a remote detection in an occupant detection system according to a second embodiment;

FIG. 10 is a graph showing a relationship between a conductance and a susceptance for a proximity detection in the second embodiment; and

FIG. 11 is a flow chart of occupant detection in the second embodiment.

Claims

1. An occupant detection system for detecting an occupant on a seat of a vehicle, the system comprising: an antenna electrode in a seat bottom of the seat; andan electronic unit connected to the antenna electrode and the vehicle, whereinthe electronic unit applies a load current to the antenna electrode so as to generate a weak electric field, and detects a potential current passing through the antenna electrode, andthe electronic unit detects an occupant based on a first impedance and a first phase difference, which are based on the load current and the potential current.

2. The occupant detection system according to claim 1, wherein: the electronic unit detects the occupant by comparing the first impedance and a threshold corresponding to the first phase difference.

3. The occupant detection system according to claim 1, wherein: the antenna electrode includes a proximity electrode for a proximity detection in the seat bottom; andthe electronic unit detects the occupant based on a second impedance and a second phase difference of the proximity detection.

4. The occupant detection system according to claim 1, wherein: the electronic unit includes a signal source for applying the load current; andthe potential current is measured in a shunt of the signal source.

5. An occupant detection system for detecting an occupant on a seat of a vehicle, the system comprising: an antenna electrode in a seat bottom of the seat; andan electronic unit connected to the antenna electrode and the vehicle, whereinthe electronic unit applies a load current to the antenna electrode so as to generate a weak electric field, and detects a potential current passing through the antenna electrode, andthe electronic unit detects an occupant based on a conductance and a susceptance of a first admittance, which is based on the load current and the potential current.

6. The occupant detection system according to claim 5, wherein: the electronic unit detects the occupant by comparing the susceptance and a threshold corresponding to the conductance.

7. The occupant detection system according to claim 5, wherein: the antenna electrode includes a proximity electrode for a proximity detection in the seat bottom; andthe electronic unit detects the occupant based on a second admittance of the proximity detection.

8. The occupant detection system according to claim 5, wherein: the electronic unit includes a signal source for applying the load current; andthe potential current is measured in a shunt of the electronic unit.

9. A method of determining an occupant on a seat of a vehicle, the method comprising: applying a load current to an antenna electrode in the seat so as to generate a weak electric field, wherein the load current is varied by the occupant;detecting a potential current generated by the electric field, wherein the potential current is varied by the occupant;calculating at least one of a set of an impedance and a phase difference, and a conductance and a susceptance of an admittance, based on the load current and the potential current; andcomparing the impedance and a threshold corresponding to the phase difference, or the susceptance and a threshold corresponding to the conductance.