System and method for drift compensation in a seat load sensing system

• US 20060175096A1
• Filed: 02/09/2005
• Published: 08/10/2006
• Est. Priority Date: 02/09/2005
• Status: Active Grant

• Current Assignee: TRW Automotive USLLC (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Automotive USLLC (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: David, Raymond J., Hibner, Christopher J.
• Granted Patent: US 7,363,184 B2
• Time in Patent Office: Days
• US Class Current: 177/144
• 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: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/0152 using strain gauges
• 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

A method (60) for adjusting a sensed load W(s)of a vehicle seat weight sensing system (10) includes the step (64) of determining a rate of change {dot over (W)}(t),{dot over (W)}_avg in the sensed load. The method (60) also includes the step (66) of determining the likelihood of drift in the sensed load W(s) in response to the determined rate of change {dot over (W)}(t),{dot over (W)}_avg.

Claims

1. A method for adjusting a sensed load of a vehicle seat weight sensing system, the method comprising the steps of:

determining a rate of change in the sensed load; and

determining the likelihood of drift in the sensed load in response to the determined rate of change.

2. The method of claim 1, further comprising the step of adjusting the sensed load in response to the determined likelihood drift in the sensed load.

3. The method of claim 1, wherein said step of determining a rate of change comprises the steps of:

filtering the sensed load;

sampling the filtered load;

determining a sensed load change as the difference between different samples of the filtered load; and

determining the rate of change as the sensed load change over the period of time between the different samples.

4. The method of claim 3, wherein said step of filtering the sensed load comprises the step of implementing a moving average filter.

5. The method of claim 1, wherein said step of determining a rate of change comprises the steps of:

filtering the sensed load;

sampling the filtered load;

averaging samples of the filtered load over an interval;

determining a sensed load change as the difference between different sample averages; and

determining the rate of change as the sensed load change over the period of time between the different sample averages.

6. The method of claim 1, wherein said step of determining the likelihood of drift in the sensed load comprises the steps of:

comparing the rate of change to predetermined categorical thresholds; and

determining the likelihood of drift in the sensed load based on the threshold category into which the rate of change falls.

7. The method of claim 6, further comprising the step of adjusting the categorical thresholds in response to determining that the sensed load change and a sensed load adjustment value have the same signs.

8. The method of claim 2, wherein said step of adjusting the sensed load in response to the determined likelihood of drift in the sensed load comprises the steps of:

determining a sensed load change;

determining a load change coefficient in response to the likelihood of drift in the sensed load;

multiplying the sensed load change by the load change coefficient to determine a sensed load adjustment value; and

adjusting the sensed load by said sensed load adjustment value.

9. The method of claim 2, wherein said steps of determining a rate of change, determining the likelihood of drift, and adjusting the sensed load are repeated throughout an ignition cycle of the vehicle.

10. A method for adjusting a sensed load of a vehicle seat weight sensing system, the method comprising the steps of:

determining a rate of change in the sensed load; and

adjusting the sensed load compensate for drift in the sensed load in response to the determined rate of change in the sensed load.

11. A vehicle seat weight sensing system comprising:

a seat weight sensor associated with a vehicle seat;

a controller operative to determine a sensed weight on the vehicle seat in response to a sensed load provided by said seat weight sensor, said controller comprising;

means for determining a rate of change in the sensed load;

means for determining the likelihood of drift in the sensed load in response to the determined rate of change.

12. The system of claim 11, wherein said controller further comprises means for adjusting the sensed load in response to the determined likelihood drift in the sensed load.

13. The system of claim 11, wherein said means for determining a rate of change further comprises:

means for filtering the sensed load;

means for sampling the filtered load;

means for determining a sensed load change as the difference between different samples of the filtered load; and

means for determining the rate of change as the sensed load change over the period of time between the different samples.

14. The system of claim 13, wherein said means for filtering the sensed load comprises a moving average filter.

15. The system of claim 11, wherein said means for determining a rate of change further comprises:

means for filtering the sensed load;

means for sampling the filtered load;

means for averaging samples of the filtered load over an interval;

means for determining a sensed load change as the difference between different sample averages; and

means for determining the rate of change as the sensed load change over the period of time between the different sample averages.

16. The system of claim 11, wherein said means for determining the likelihood of drift in the sensed load comprises:

means for comparing the rate of change to predetermined categorical thresholds; and

means for determining the likelihood of drift in the sensed load based on the threshold category into which the rate of change falls.

17. The system of claim 16, wherein said controller further comprises means for adjusting the categorical thresholds in response to determining that the sensed load change and a sensed load adjustment value have the same signs.

18. The system of claim 12, wherein said means for adjusting the sensed load in response to the determined likelihood of drift in the sensed load comprises:

means for determining a sensed load change;

means for determining a load change coefficient in response to the likelihood of drift in the sensed load;

means for multiplying the sensed load change by the load change coefficient to determine a sensed load adjustment value; and

means for adjusting the sensed load by said sensed load adjustment value.