Vehicle occupant presence and position sensing system

• US 6,292,727 B1
• Filed: 12/22/1998
• Issued: 09/18/2001
• Est. Priority Date: 11/23/1993
• Status: Expired due to Fees

• Current Assignee: Peter Norton
• Original Assignee: Peter Norton
• Inventors: Norton, Peter
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US09/218,231
• Time in Patent Office: 1,001 Days
• Field of Search: 701/36, 701/45, 701/46, 701/47, 340/436, 340/438, 340/667, 340/669, 307/9.1, 307/10.1, 280/235, 280/727, 280/734, 280/735, 180/271, 180/274, 180/282
• US Class Current: 701/45
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors
• CPC Class Codes: B60R 21/01554 Seat position sensors
• CPC Class Codes: B60R 21/01556 Child-seat detection systems

Abstract

A vehicle seat occupant presence and position sensing system for vehicles equipped with air bags comprises means for measuring the magnitude and Q of capacitance between electrodes in the seat. The magnitude and Q are combined by a microprocessor to characterize the seat occupant and, if the occupant is a person, ascertain the distance of the back of the person from the back of the seat thereby distinguishing between a seat occupied by a normally seated person and certain other circumstances in which deployment of air bags is not desired. A microprocessor prevents air bag deployment when the seat has not held a normally seated person immediately prior to an accident. The position of the occupant relative to the seat, the track position and recline angle of the vehicle seat and vehicle deceleration during a crash are used to estimate the position of the occupant relative to a deploying air bag during the crash. Knowing the position of the occupant enables a highly accurate determination of the best usage to make of an air bag.

Claims

1. In a vehicle having occupant protection means responsive to a crash, the improvement comprising:

a vehicle seat having a seat back, a seat cushion and sensing means producing a signal categorizing the distance of the back of a seated occupant from the surface of the seat back into at least three categories, and including

control means responsive to said signal for controlling said response.

2. The invention as defined by claim 1 wherein:

said sensing means comprises an electrode in said seat cushion and an electrode in said seat back and means for producing a first signal indicating the capacitance between said electrodes, and

said signal categorizing the distance is said first signal.

3. The invention as defined by claim 1 wherein:

said sensing means comprises;

an electrode in said seat cushion, an electrode in said seat back, and means for producing a first signal indicating the capacitance between said electrodes and a second signal indicating the Q of said capacitance between said electrodes, and including

means responsive to said first signal and said second signal by producing said signal categorizing the distance.

4. The invention as defined by claim 3 wherein:

said first signal is substantially proportional to the logarithm of said capacitance.

5. The invention as defined by claim 3 wherein:

said first signal is a function of said capacitance such that measurement points plotted on an x-y plot having said first signal as one coordinate and said second signal as the other coordinate form groups, and

each of said groups comprise data points characteristic of a seat occupant and the position of that occupant.

6. The invention as defined by claim 5 wherein:

said first and second signals are also functions of said capacitance and Q such that each of said groups approximate a straight line having a characteristic midpoint, length and orientation.

7. The invention as defined by claim 6 and including:

means for associating a measurement point on said x-y plot having said first signal as one coordinate and said second signal as the other coordinate with one of said groups, whereby the content of said vehicle seat is categorized.

8. The invention as defined by claim 7 wherein:

said means for associating a measurement point with one of said groups comprises;

computing means for computing a first vector dot product of a first vector defined for each group at the time of manufacture and a vector from said characteristic midpoint for each said group to said measurement point,

computing means for computing a second vector dot product of a second vector defined for each said group at the time of manufacture and said vector from said characteristic midpoint for each said group to said measurement point,

computing means for squaring said first and second vector dot products and adding the squared dot products together to obtain a sum, and

means for selecting the group for which said sum is smallest.

9. The invention as defined by claim 7 wherein:

said signal categorizing the distance also categorizes said seat as empty or containing a rear facing baby seat and said control means prevents airbag activation when said signal categorizing the distance indicates said seat is empty or contains a rear facing baby seat.

10. In an occupant protection system of a vehicle comprising an occupant restraint, an accelerometer responsive to axial deceleration of said vehicle, and a microprocessor processing information from said accelerometer and controlling the activation of said occupant restraint, the improvement comprising:

a vehicle seat having a seat back, a seat cushion and occupant position sensing means for producing an occupant position signal categorizing the distance of the back of an occupant of said seat from said seat back into at least three categories, said occupant position sensing means being connected with said microprocessor for transmitting said occupant position signal thereto,

seat position sensing means for producing a seat position signal indicating the position of said seat relative to a reference position fixed with respect to said vehicle, said seat position sensing means being connected with said microprocessor for transmitting said seat position signal thereto, and wherein

said microprocessor being responsive to said occupant position signal and said seat position signal when controlling said activation of said occupant restraint.

11. The invention as defmed by claim 10 and including,

an electrode in said seat cushion, an electrode in said seat back and means for producing a first electrical signal indicating the capacitance between said electrodes and a second electrical signal indicating the Q of said capacitance, and wherein said occupant position sensing means derives said occupant position signal from said first signal and said second signal.

12. The invention as defined by claim 10 and including:

means for combining said distance and said position of said seat to compute the position of the torso of said occupant relative to said reference position, and wherein

said means responsive to said information is responsive to said position of said torso.

13. The invention as defined by claim 10 and wherein:

said microprocessor including code for combining said distance of the back of said occupant from said seat back and said position of said seat to compute the position of said occupant relative to a reference frame fixed with respect to said vehicle, and including

means responsive to said position of said occupant relative to said reference frame for ascertaining when said activation of said occupant restraint is warranted.

14. In a vehicle having occupant protection means responsive to a crash, the improvement comprising:

a vehicle seat having a seat back, a seat cushion, an electrode in the seat back, and an electrode in the seat cushion,

capacitance sensing means for producing a first signal indicating the capacitance between said electrodes, and

control means responsive to said first signal for controlling said response to a crash.

15. The invention as defined by claim 14 wherein:

said capacitance sensing means also comprises means for producing a second signal indicating the Q of said capacitance, and

said control means being responsive to both said first signal and said second signal for controlling said response to said crash.

16. The invention as defined by claim 15 and including:

means responsive to said first signal and said second signal by producing a seat occupant category signal that indicates to which of a set of at least three categories the occupant of the seat belongs, and wherein

said control means being responsive to said seat occupant category signal for controlling said response to said crash.

17. The invention as defined by claim 15 wherein:

said first and second signals are functions of said capacitance and Q respectively such that points on an x-y plot having said first signal as one coordinate and said second signal as the other coordinate form groups, and

each of said groups comprising data points characteristic of a seat occupant and the position of that occupant.

18. The invention as defined by claim 17 wherein:

said first and second signals are finctions of said capacitance and Q respectively such that said groups approximate straight lines, each group being approximated by a straight line having a characteristic midpoint, length and orientation.

19. The invention as defined by claim 17 wherein:

said first signal is substantially proportional to the logarithm of said capacitance.

20. The invention as defined by claim 17 and including:

means for associating a measurement point on said x-y plot having said first signal as one coordinate and said second signal as the other coordinate with one of said groups, whereby the content of said vehicle seat is categorized.

21. The invention as defined by claim 20 wherein:

each of said groups has a characteristic point on said x-y plot and said means for associating a measurement point with one of said groups comprises;

computing means for computing for each of said groups a first vector dot product of a first vector defined for the group at the time of manufacture and a vector from said characteristic point of the group to said measurement point,

computing means for computing for each of said groups a second vector dot product of a second vector defined for the group at the time of manufacture and said vector from said characteristic point of the group to said measurement point, and

computing means for computing for each of said groups the squares of said first and second vector dot products and adding said squares together to obtain a sum for each group, and wherein

said means for associating comprises means for selecting the group for which said sum is least.

22. The invention as defmed by claim 15 and including:

means for determining from said first signal and said second signal if said seat is empty or contains a rear facing baby seat for enabling said control means to not activate said airbag when said means for determining determines that said seat is empty or contains a rear facing baby seat.