Vehicle occupant characterization method based on sensed occupant weight

• US 6,246,936 B1
• Filed: 10/05/1999
• Issued: 06/12/2001
• Est. Priority Date: 10/05/1999
• Status: Expired due to Term

• Current Assignee: Aptiv Technologies Limited (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Lee, Chiutsun Albert, Thayer, Peter Alan, Gray, Charles A., Little, David R., Kaltenbacher, Phillip E II, Sullivan, Stuart Stites, Nunan, Douglas Allen, Fortune, Duane Donald, Roe, Pamela Ann, Murphy, Morgan Daniel
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US09/412,936
• Time in Patent Office: 616 Days
• Field of Search: 280/734, 280/735, 280/801.1, 280/802, 701/35, 701/45, 701/46, 701/47, 180/271, 180/282, 180/268, 180/273, 177/209, 297/DIG.3, 297/452.41, 297/195.12, 297/284.6, 340/436, 340/666, 340/665, 340/667
• US Class Current: 701/45
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01556 Child-seat detection systems
• CPC Class Codes: G01G 19/4142 for controlling activation of safety devices, e.g. airbag systems electrical circuits for triggering safety arrangements in case of vehicle accidents B60R21/015

Abstract

An improved weight-based occupant characterization method that can inexpensively and reliably distinguish between a child or small adult and a tightly cinched child seat. When the sensed weight is in a specified range that could be produced by a tightly cinched child seat, the system characterizes the occupant based on a detected variation in sensed weight during movement of the vehicle. If the variance of the sensed weight is below a threshold for a predetermined interval, the occupant is characterized as a child seat, since a tightly cinched seat belt severely restricts variance. If the variance exceeds the threshold for a predetermined interval, the occupant is characterized as a child or small adult. A correlative factor that can be used in distinguishing between a child seat and a child or small adult is determined by computing a slope reversal rate, or frequency, of the measured weight. In this case, a child seat is indicated by the combination of low variance and a high frequency, whereas a child or small adult is indicated by the combination of high variance and a low frequency. Additionally, movement of the vehicle can be detected when the variance of the sensed weight is within a predetermined range for at least a predetermined interval.

Claims

1. A method of distinguishing between a vehicle occupant and a cinched child seat in an occupant weight detection system that provides an output signal responsive to weight applied to a vehicle seat, the method comprising the steps of:

computing a variance of the output signal and a running average of said variance;

detecting vehicle movement;

comparing the average variance to a predefined threshold when vehicle movement is detected and the output signal is within a range that could be produced by either a vehicle occupant or a cinched child seat;

determining that a cinched child seat is present if the average variance is below the predefined threshold; and

determining that a vehicle occupant is present if the average variance is above the predefined threshold.

2. The method of claim 1, including the steps of:

disabling deployment of a an air bag if it is determined that a cinched child seat is present; and

enabling deployment of the air bag is it is determined that a vehicle occupant is present.

3. The method of claim 2, including the steps of:

setting a cinched child seat latch when it is determined that a cinched child seat is present; and

inhibiting the step of enabling deployment of the air bag if the cinched child seat latch is set and it is subsequently determined that a vehicle occupant is present.

4. The method of claim 3, including the steps of:

setting an occupant latch when it is determined that an occupant is present; and

inhibiting the step of disabling deployment of the air bag if the occupant latch is set and it is subsequently determined that a cinched child seat is present.

5. The method of claim 4, including the step of:

resetting the occupant latch and the cinched child seat latch when vehicle movement is not detected.

6. The method of claim 1, wherein the step of detecting vehicle movement includes the steps of:

measuring a time interval for which the variance is within a predefined range characteristic of vehicle movement; and

detecting vehicle movement if the measured interval exceeds a first predefined time interval.

7. The method of claim 6, including the step of:

resetting the measured time interval and detecting a lack of vehicle movement if the variance is less than the predefined range for at least a second predefined time interval which is shorter than said first predefined time interval.

8. A method of distinguishing between a vehicle occupant and a cinched child seat in an occupant weight detection system that provides an output signal responsive to weight applied to a vehicle seat, the method comprising the steps of:

computing an average variance of the output signal;

computing a frequency of the output signal;

detecting vehicle movement;

when vehicle movement is detected and the output signal is within a range that could be produced by either a vehicle occupant or a cinched child seat;

determining that a cinched child scat is present if the frequency is above a predefined frequency threshold and the average variance is below a predefined variance threshold; and

determining that a vehicle occupant is present if the frequency is below the predefined frequency threshold and the average variance is above the predefined variance threshold.

9. The method of claim 8, including the steps of:

measuring an interval for which vehicle movement is detected and the output signal is within a range that could be produced by either a vehicle occupant or a cinched child seat; and

determining that a cinched child seat is present if the frequency is above the predefined frequency threshold and the measured interval is longer than a predetermined interval.

10. The method of claim 8, including the steps of:

measuring an interval for which vehicle movement is detected and the output signal is within a range that could be produced by either a vehicle occupant or a cinched child seat; and

determining that a vehicle occupant is present if the frequency is below the predefined frequency threshold and the measured interval is longer than a predetermined interval.

11. A method of distinguishing between a vehicle occupant and a cinched child seat in an occupant weight detection system that provides an output signal responsive to weight applied to a vehicle seat, the method comprising the steps of:

computing an average variance of the output signal;

detecting vehicle movement;

measuring an interval for which vehicle movement is detected and the output signal is within a range that could be produced by either a vehicle occupant or a cinched child seat;

comparing the average variance to a predefined threshold when the measured interval exceeds a predefined interval;

determining that a cinched child seat is present if the average variance is below the predefined threshold; and

determining that a vehicle occupant is present if the average variance is above the predefined threshold.

12. A method of distinguishing between a vehicle occupant and a cinched child seat in an occupant weight detection system that provides an output signal responsive to weight applied to a vehicle seat, the method comprising the steps of:

computing an average variance of the output signal;

computing a frequency of the output signal;

detecting vehicle movement;

measuring an interval for which vehicle movement is detected and the output signal is within a range that could be produced by either a vehicle occupant or a cinched child seat;

when the measured interval exceeds a first predefined interval;

determining that a cinched child seat is present if the frequency is above a predefined frequency threshold and the average variance is below a predefined variance threshold; and

determining that a vehicle occupant is present if the frequency is below the predefined frequency threshold and the average variance is above the predefined variance threshold.

13. The method of claim 12, including the step of:

determining that a cinched child seat is present if the frequency is above the predefined frequency threshold and the measured interval is longer than a second predefined interval which is longer than said first predefined interval.

14. The method of claim 12, including the step of:

determining that a vehicle occupant is present if the frequency is below the predefined frequency threshold and the measured interval is longer than a second predefined interval which is longer than said first predefined interval.