Capacitance-based occupant detection system and occupant protection system

• US 20080198024A1
• Filed: 02/19/2008
• Published: 08/21/2008
• Est. Priority Date: 02/21/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kiribayashi, Shinichi, Yamanaka, Shoichi, Ishikawa, Masahiro, Kamizono, Tsutomu
• Granted Patent: US 8,040,241 B2
• Time in Patent Office: Days
• US Class Current: 340/573.1
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60N 2/003 characterised by the sensor mounting location in or on the seat
• CPC Class Codes: B60N 2/0035 characterised by the sensor data transmission, e.g. wired connections or wireless transmitters therefor; characterised by the sensor data processing, e.g. seat sensor signal amplification or electric circuits for providing seat sensor information
• CPC Class Codes: B60N 2210/12 Capacitive; Electric field
• CPC Class Codes: B60N 2210/50 Inertial sensors
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

A capacitance-based occupant detection system accurately determines seat occupancy and a failure of an electrode and between electrodes and includes an impedance calculation section, a Re/Im part calculation section, and a determination section. A first impedance Z1 is calculated including a main-body impedance Za between a main electrode and a vehicle body. The Re/Im part calculation section calculates real and imaginary parts of the first impedance Z1 based on the first impedance Z1 calculated by the impedance calculation section. The determination section determines the presence or absence of destruction of the main electrode and a guard electrode based on an imaginary part of the first impedance Z1 calculated by the Re/Im part calculation section.

Claims

1. A capacitance-based occupant detection system comprising:

a power supply section for generating an AC voltage;

a main electrode provided for a vehicle seat;

a main wiring section for connecting the power supply section with the main electrode;

a guard electrode provided between a seat frame electrically connected to a vehicle ground and the main electrode apart from and opposite to the main electrode;

an impedance calculation section for calculating a first impedance containing a main-body impedance between the main electrode and a vehicle body in an occupant detection mode for ensuring an equal electric potential for the main electrode and the guard electrode and for generating an electric field between the main electrode and the vehicle body electrically connected to the vehicle ground;

a Re/Im part calculation section for calculating real and imaginary parts of the first impedance based on the first impedance calculated by the impedance calculation section;

a failure determination section for determining presence or absence of destruction of the main electrode or a short circuit between the main electrode and the guard electrode based on the imaginary part of the first impedance calculated by the Re/Im part calculation section; and

an occupant determination section for determining the presence of an occupant on the seat in accordance with a determination result of the failure determination section in the occupant detection mode.

2. The capacitance-based occupant detection system according to claim 1

wherein the failure determination section further determines presence or absence of destruction of the main electrode or a short circuit between the main electrode and the guard electrode based on the real part of the first impedance calculated by the Re/Im part calculation section.

3. The capacitance-based occupant detection system according to claim 1,

wherein the failure determination section determines destruction of the main electrode or a short circuit between the main electrode and the guard electrode when the imaginary part of the first impedance calculated by the Re/Im part calculation section in the occupant detection mode is smaller than a predetermined imaginary part threshold value.

4. A capacitance-based occupant detection system comprising:

a power supply section for generating AC voltage;

a main electrode provided for a vehicle seat;

a main wiring section for connecting the power supply section with the main electrode;

a guard electrode that is provided between a seat frame electrically connected to a vehicle ground and the main electrode apart from and opposite to the main electrode;

an impedance calculation section for calculating a first impedance containing a main-body impedance between the main electrode and a vehicle body in an occupant detection mode for ensuring an equal electric potential for the main electrode and the guard electrode and generating an electric field between the main electrode and the vehicle body electrically connected to the vehicle ground;

a Re/Im part calculation section for calculating real and imaginary parts of the first impedance based on the first impedance calculated by the impedance calculation section;

a failure determination section for determining excessive wetting of the seat based on the real part of the first impedance calculated by the Re/Im part calculation section; and

an occupant determination section for determining the presence of an occupant on the seat in accordance with a determination result of the failure determination section in the occupant detection mode.

5. The capacitance-based occupant detection system according to claim 4,

wherein the failure determination section further determines presence or absence of excessive wetting of the seat based on the imaginary part of the first impedance calculated by the Re/Im part calculation section.

6. The capacitance-based occupant detection system according to claim 4,

wherein the failure determination section determines excessive wetting of the seat when the imaginary part of the first impedance calculated by the Re/Im part calculation section is greater than or equal to a predetermined real part threshold value.

7. The capacitance-based occupant detection system according to claim 6,

wherein the Re/Im part calculation section calculates the real part of the first impedance as a real upper bound when a range of calculating the real part is settled and the real part of the first impedance exceeds the real upper bound of the range;

and

wherein the real part threshold value is set to the real upper bound.

8. A capacitance-based occupant detection system comprising:

a power supply section for generating AC voltage;

a main electrode provided for a vehicle seat;

a main wiring section for connecting the power supply section with the main electrode;

a guard electrode that is provided between a seat frame electrically connected to a vehicle ground and the main electrode apart from and opposite to the main electrode;

a sub electrode provided apart from and adjacently to the main electrode;

an impedance calculation section for calculating a second impedance containing a main-sub impedance between the main electrode and the sub electrode in a wetting detection mode for generating an electric field between the main electrode and the sub electrode;

a Re/Im part calculation section for calculating real and imaginary parts of the second impedance based on the second impedance calculated by the impedance calculation section;

a failure determination section for determining destruction of the main electrode, destruction of the sub electrode, or a short circuit between the main electrode and the guard electrode based on the imaginary part of the second impedance calculated by the Re/Im part calculation section; and

an occupant determination section for determining the presence of an occupant on the seat in accordance with a determination result of the failure determination section in an occupant detection mode for ensuring an equal electric potential for the main electrode and the guard electrode and generating an electric field between the main electrode and the vehicle body electrically connected to the vehicle ground.

9. The capacitance-based occupant detection system according to claim 8,

wherein the failure determination section further determines presence or absence of destruction of the main electrode, destruction of the sub electrode, and a short circuit between the main electrode and the guard electrode based on the real part of the second impedance calculated by the Re/Im part calculation section.

10. The capacitance-based occupant detection system according to claim 8,

wherein the failure determination section determines destruction of the main electrode, destruction of the sub electrode, or a short circuit between the main electrode and the guard electrode when the imaginary part of the second impedance calculated by the Re/Im part calculation section in the wetting detection mode is smaller than a predetermined imaginary part threshold value.

11. A capacitance-based occupant detection system comprising:

a power supply section for generating AC voltage;

a main electrode provided for a vehicle seat;

a main wiring section for connecting the power supply section with the main electrode;

a guard electrode that is provided between a seat frame electrically connected to a vehicle ground and the main electrode apart from and opposite to the main electrode;

a sub electrode provided apart from and adjacently to the main electrode;

an impedance calculation section for calculating a second impedance containing a main-sub impedance between the main electrode and the sub electrode in a wetting detection mode for generating an electric field between the main electrode and the sub electrode;

a Re/Im part calculation section for calculating real and imaginary parts of the second impedance based on the second impedance calculated by the impedance calculation section;

a failure determination section for determining excessive wetting of the seat based on the real part of the second impedance calculated by the Re/Im part calculation section; and

an occupant determination section for determining the presence of an occupant on the seat in accordance with a determination result of the failure determination section in an occupant detection mode for ensuring an equal electric potential for the main electrode and the guard electrode and generating an electric field between the main electrode and the vehicle body electrically connected to the vehicle ground.

12. The capacitance-based occupant detection system according to claim 11,

wherein the failure determination section further determines presence or absence of excessive wetting of the seat based on the imaginary part of the second impedance calculated by the Re/Im part calculation section.

13. The capacitance-based occupant detection system according to claim 11,

wherein the failure determination section determines excessive wetting of the seat when the real part of the second impedance calculated by the Re/Im part calculation section in the wetting detection mode is greater than or equal to a predetermined real part threshold value.

14. The capacitance-based occupant detection system according to claim 13,

wherein the Re/Im part calculation section calculates the real part of the second impedance as a real upper bound when a range of calculating the real part is settled and the real part of the second impedance exceeds the real upper bound of the range;

and

wherein the real part threshold value is set to the real upper bound.

15. A capacitance-based occupant detection system comprising:

a power supply section for generating AC voltage;

a main electrode provided for a vehicle seat;

a main wiring section for connecting the power supply section with the main electrode;

a guard electrode that is provided between a seat frame electrically connected to a vehicle ground and the main electrode apart from and opposite to the main electrode;

a sub electrode provided apart from and adjacently to the main electrode;

an impedance calculation section for calculating a second impedance containing a main-sub impedance between the main electrode and the sub electrode in a wetting detection mode for generating an electric field between the main electrode and the sub electrode;

a Re/Im part calculation section for calculating real and imaginary parts of the second impedance based on the second impedance calculated by the impedance calculation section;

a failure determination section for determining presence or absence of a short circuit between the main electrode and the sub electrode based on one of the real part and the imaginary part of the second impedance calculated by the Re/Im part calculation section; and

an occupant determination section for determining the presence of an occupant on the seat in accordance with a determination result of the failure determination section in an occupant detection mode for ensuring an equal electric potential for the main electrode and the guard electrode and generating an electric field between the main electrode and the vehicle body electrically connected to the vehicle ground.

16. The capacitance-based occupant detection system according to claim 15,

wherein the failure determination section further determines a short circuit between the main electrode and the sub electrode when the real part of the second impedance calculated by the Re/Im part calculation section in the wetting detection mode is greater than or equal to a predetermined real part threshold value.

17. The capacitance-based occupant detection system according to claim 16,

wherein the Re/Im part calculation section calculates the real part of the second impedance as a real upper bound when a range of calculating the real part is settled and the real part of the second impedance exceeds the real upper bound of the range;

and

wherein the real part threshold value is set to the real upper bound.

18. The capacitance-based occupant detection system according to claim 15,

wherein the failure determination section further determines a short circuit between the main electrode and the sub electrode when the imaginary part of the second impedance calculated by the Re/Im part calculation section in the wetting detection mode is greater than or equal to a predetermined imaginary part threshold value.

19. The capacitance-based occupant detection system according to claim 18,

wherein the Re/Im part calculation section calculates the imaginary part of the second impedance as the imaginary upper bound when a range of calculating the imaginary part is specified and the imaginary part of the second impedance exceeds an imaginary upper bound of the range;

and

wherein the imaginary part threshold value is set to the imaginary upper bound.

20. An occupant protection system comprising:

a power supply section for generating an AC voltage;

a main electrode provided for a vehicle seat;

a main wiring section for connecting the power supply section with the main electrode;

a guard electrode provided between a seat frame electrically connected to a vehicle ground and the main electrode apart from and opposite to the main electrode;

an impedance calculation section for calculating a first impedance containing a main-body impedance between the main electrode and a vehicle body in an occupant detection mode for ensuring an equal electric potential for the main electrode and the guard electrode and for generating an electric field between the main electrode and the vehicle body electrically connected to the vehicle ground;

a Re/Im part calculation section for calculating real and imaginary parts of the first impedance based on the first impedance calculated by the impedance calculation section;

a failure determination section for determining presence or absence of destruction of the main electrode or a short circuit between the main electrode and the guard electrode based on the imaginary part of the first impedance calculated by the Re/Im part calculation section;

an occupant determination section for determining the presence of an occupant on the seat in accordance with a determination result of the failure determination section in the occupant detection mode; and

a control apparatus for controlling an occupant protection apparatus based on one or more determination results of one or more of the failure determination section and the occupant determination section.