Multiple sensor vehicle occupant detection for air bag deployment control

• US 20040196150A1
• Filed: 04/23/2003
• Published: 10/07/2004
• Est. Priority Date: 03/02/2001
• Status: Active Grant

• Current Assignee: Nidec Elesys Americas Corporation (Nidec Corporation)
• Original Assignee: Elesys North America Incorporated (Nidec Corporation)
• Inventors: Shieh, Shiuh-An, Thompson, Gregory T.
• Granted Patent: US 7,084,763 B2
• Time in Patent Office: Days
• US Class Current: 340/501
• 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 2/0025 by using weight measurement
• CPC Class Codes: B60N 2/0033 mounted on or in the foam cushion
• 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 2230/30 Signal processing of sensor data
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

A passenger detection system is provided. The passenger detection system utilizes an oscillation circuit that causes an antenna electrode to emit an electric field that is disrupted by the electrical characteristics of an object placed on the seat. This disruption alters the current and phase of the signal in the antenna electrode. By comparing the current flowing in the antenna electrode and/or the difference between the phase of the signal in the antenna electrode and the oscillation circuit output signal with predetermined threshold values, it is possible to detect the presence of a passenger in a reliable and inexpensive manner. Environmental sensors are used to make the determination more accurate. Humidity, moisture and/or grounding condition are detected and used to alter processing, values or calculations.

Claims

1. A vehicle passenger detection system for sensing a passenger in a passenger seating area, the system comprising:

a passenger detection system; and

a humidity sensor connected with the passenger detection system;

wherein the passenger detection system is responsive to the humidity sensor.

2. The system of claim 1 wherein the passenger detection system comprises a capacitive sensing system.

3. The system of claim 1 wherein the passenger detection system comprises:

at least one electrode; and

circuitry operable to detect a current in the at least one electrode.

4. The system of claim 3 wherein the circuitry comprises a controller operative to determine the characteristic of the passenger as a function of data from the at least one electrode.

5. The system of claim 1 wherein the humidity sensor comprises a solid state capacitive humidity sensor.

8. The system of claim 1 further comprising:

an oscillator operatively connected with the humidity sensor; and

a voltage detector operatively connected with the humidity sensor.

9. The system of claim 8 wherein the voltage detector comprises:

two resistors connected in series between the humidity sensor and the oscillator; and

a buffer connected between the two resistors.

10. The system of claim 1 wherein a measured value of the passenger detection system is altered as a function of an output of the humidity sensor.

11. The system of claim 1 wherein a table for the passenger detection system is selected as a function of an output of the humidity sensor.

12. The system of claim 1 wherein the passenger detection system operatively connects with an air bag control system.

6. The system of claim I wherein the humidity sensor is positioned in a seat.

7. The system of claim 6 wherein the passenger detection system comprises an electrode in the seat.

13. A vehicle passenger detection method for sensing a passenger in a passenger seating area, the method comprising the acts of:

(a) measuring a humidity; and

(b) determining a presence of the passenger in the passenger seating area;

wherein (b) is a function of the measured humidity.

14. The method of claim 13 wherein (b) comprises determining the presence with a capacitive sensing system.

15. The method of claim 13 wherein (b) comprises detecting a current in the at least one electrode.

16. The method of claim 15 further comprising:

(c) determining a characteristic of the passenger as a function of data from the at least one electrode.

17. The method of claim 13 wherein (a) comprises measuring a humidity sensitive capacitance.

18. The method of claim 13 wherein (a) comprises measuring with a sensor positioned in a seat.

19. The method of claim 18 wherein (b) comprises determining in response to a signal in an electrode in the seat.

20. The method of claim 13 wherein (a) comprises:

(a1) applying an oscillating signal to a humidity sensor; and

(a2) detecting a voltage connected with the humidity sensor.

21. The method of claim 13 wherein a measured value is altered as a function of an output of the humidity sensor.

22. The method of claim 13 wherein a table is selected as a function of an output of the humidity sensor.

23. The method of claim 13 further comprising:

(c) controlling an air bag system in response to (b).

24. A vehicle passenger detection system for sensing a passenger in a passenger seating area, the system comprising:

a passenger detection system; and

a moisture sensor connected with the passenger detection system;

wherein the passenger detection system is responsive to the moisture sensor.

25. The system of claim 24 wherein the passenger detection system comprises a capacitive sensing system.

26. The system of claim 24 wherein the passenger detection system comprises:

at least one electrode; and

circuitry operable to detect a current in the at least one electrode.

27. The system of claim 26 wherein the circuitry comprises a controller operative to determine the characteristic of the passenger as a function of data from the at least one electrode.

28. The system of claim 24 wherein the moisture sensor comprises two conductors connected by absorbent material.

29. The system of claim 24 wherein the moisture sensor is positioned in a seat.

30. The system of claim 29 wherein the passenger detection system comprises an electrode adjacent to the moisture sensor in the seat.

31. The system of claim 28 further comprising circuitry to measure a resistance between the two conductors.

32. The system of claim 24 further comprising a processor operable to determine a moisture level as a function of transmissions at different frequencies.

33. The system of claim 24 wherein a measured value of the passenger detection system is altered as a function of a moisture level.

34. The system of claim 24 wherein a table for the passenger detection system is selected as a function of a moisture level.

35. The system of claim 24 wherein detected moisture generates a fault condition of the passenger detection system.

36. The system of claim 24 wherein the passenger detection system operatively connects with an air bag control system.

37. A vehicle passenger detection method for sensing a passenger in a passenger seating area, the method comprising the acts of:

(a) measuring moisture; and

(b) determining a presence of the passenger in the passenger seating area;

wherein (b) is a function of the measured moisture.

38. The method of claim 37 wherein (b) comprises determining the presence with a capacitive sensing system.

39. The method of claim 37 wherein (b) comprises detecting a current in the at least one electrode.

40. The method of claim 39 further comprising:

(c) determining a characteristic of the passenger as a function of data from the at least one electrode.

41. The method of claim 37 wherein (a) comprises measuring a resistance.

42. The method of claim 37 wherein (a) comprises measuring with a sensor positioned in a seat.

43. The method of claim 42 wherein (b) comprises determining in response to a signal in an electrode adjacent the sensor in the seat.

44. The method of claim 37 wherein (a) comprises:

(a1) applying first and second oscillating signals at first and second frequencies, respectively; and

(a2) calculating a moisture level as a function of signals responsive to (a).

45. The method of claim 37 wherein a measured value is altered as a function of the measured moisture.

46. The method of claim 37 wherein a table is selected as a function of the measured moisture.

47. The method of claim 37 further comprising:

(c) controlling an air bag system in response to (b).

48. The method of claim 47 wherein (b) comprises sending a fault signal where a moisture level exceeds a threshold.

49. A vehicle passenger detection method for sensing a passenger in a passenger seating area, the method comprising the acts of:

(a) connecting a first electrode to ground;

(b) measuring a first signal at a second electrode while the first electrode is connected to ground;

(c) disconnecting the first electrode from ground;

(d) measuring a second signal at the second electrode with the second electrode is disconnected from ground; and

(e) determining a grounded state of the passenger as a function of the first and second signals.

50. The method of claim 49 wherein (c) comprises allowing the first electrode to float.

51. The method of claim 49 wherein (c) comprises applying a signal to the first electrode.

52. The method of claim 51 further comprising:

(f) applying an oscillating signal to the second electrode during (d);

wherein (c) comprises applying the oscillating signal to the first electrode.

53. The method of claim 49 further comprising:

(f) repeating (a)-(d) for different combinations of electrodes.

54. The method of claim 49 wherein (b) and (d) are sequentially performed.

55. The method of claim 49 wherein (e) comprises comparing the first signal to the second signal.

56. The method of claim 55 further comprising:

(f) altering the first signal when the first signal is substantially different than the second signal.

57. The method of claim 56 wherein (f) comprises altering as a function of a distance from the second electrode to the passenger seating area.

58. The method of claim 55 wherein (e) comprises determining that the passenger is grounded where an amplitude of the first signal is substantially the same as the amplitude of the second signal.

59. The method of claim 55 further comprising:

(f) selecting a table when the first signal is substantially different than the second signal.

60. A vehicle passenger detection system for determining a ground state of a passenger in a passenger seating area, the system comprising:

first and second electrodes;

a switch operable to connect the first electrode to ground; and

a means for measuring first and second signals at the second electrode when the first electrode is connected to ground and when the first electrode is disconnected from ground, respectively.

61. The system of claim 60 wherein the switch is operable to connect the first electrode to ground and to open the connection between the first electrode and other conductors.

62. The system of claim 60 wherein the switch is operable to connect the first electrode to ground and to an oscillator.

63. The system of claim 60 further comprising a processor connected with the means for measuring, the processor operable to compare the first signal with the second signal.