Weight measurement system, method and weight sensor

• US 6,725,165 B1
• Filed: 08/10/2000
• Issued: 04/20/2004
• Est. Priority Date: 08/10/2000
• Status: Expired due to Fees

• Current Assignee: Autoliv ASP Incorporated (Autoliv Incorporated)
• Original Assignee: Autoliv ASP Incorporated (Autoliv Incorporated)
• Inventors: Kopitzke, Daniel F., Knox, Matthew J.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US09/636,154
• Time in Patent Office: 1,349 Days
• Field of Search: 702/42, 73/626.27, 340/667, 340/573.1, 340/666, 280/735, 280/2, 180/268, 180/271, 701/45, 709/49, 296/65.18, 177/144
• US Class Current: 702/42
• 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 2021/01211 Expansion of air bags
• CPC Class Codes: B60R 2021/01218 control of expansion speed
• CPC Class Codes: B60R 21/013 including means for detecting collisions, impending collisions or roll-over
• CPC Class Codes: B60R 21/01504 detecting bag displacement
• 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
• CPC Class Codes: G01G 23/01 Testing or calibrating of weighing apparatus

Abstract

A weight measurement system for automatically calibrating weight sensors installed on a motor vehicle seat. The system performs a calibrate operation whenever a valid weight measurement window is found. A valid weight measurement window is defined by the seat being empty, an associated door being open and an associated seat buckle being unlatched. The system operates in a factory install mode to establish a reference zero set value and in a diagnostic mode to establish a temporary zero set value that reflects drift of the weight sensors. The temporary zero set value is used by a weight management program to control occupant restraint devices. The weight sensor has an integral body with two lands connected by an elastomeric beam. The elastomeric beam has a pair of opposed surfaces that define a region of minimum thickness and one or more regions of maximum thickness. A resistive strain gauge element is disposed on the region of minimum thickness. The system measures changes in the resistance of the weight sensor caused by weight of the seat.

Claims

1. A method of automatically calibrating a characteristic of a weight sensor installed to sense weight of a seat in a motor vehicle that has a door and a seat belt with a buckle associated with the seat, said method comprising:

(a) determining that the seat is empty and that a condition is present, where the condition is a member of the group consisting of the door being open and the seat belt being unbuckled;

(b) if step (a) determines that the seat is empty and that said condition is present, establishing a set of values of said characteristic that define a zero set value; and

(c) presenting the set of values that define a zero set value for in seat weight measurements.

2. The method of claim 1, further comprising:

(d) repeating steps (a), (b) and (c) so long as the seat is installed in the motor vehicle.

3. The method of claim 2, further comprising:

(e) retaining a first set of values established by a first performance of step (b) as a reference set of values.

4. The method of claim 3, further comprising:

(f) retaining a second set of values as a temporary set of values, if the second set of values (i) is established by step (b) after the reference set of values is established and (ii) exceeds a predetermined deviation from the reference set of values; and

wherein step (c) presents the temporary set of values as defining a modified zero set value for said in seat weight measurements.

5. The method of claim 4, wherein the temporary set of values is one of a plurality of the temporary sets of values established by separate performances of step (b), and wherein step (c) presents the most recently established one of the temporary sets of values for the in seat weight measurements.

6. The method of claim 5, wherein the weight sensor is one of a plurality of weight sensors installed to sense said weight of the seat, and wherein the sets of values established by step (b) are derived from measurements of said characteristic of each of said plurality of weight sensors.

7. The method of claim 6, further comprising:

(g) limiting the number of times steps (a) through (h) are performed during the time the open door condition is found present.

8. The method of claim 1, further comprising:

(d) if step (a) determines that either the seat is not empty or the condition is not present, establishing the set of values;

(e) if the seat is still empty or the condition is still not present, rejecting the set of values;

(f) repeating steps (d) and (e) up to n times, where n is an integer greater than one;

(g) if the seat is found empty and the condition found present before step (e) is performed an nth time, retaining the set of values established by step (d); and

(h) performing step (c) with the retained set of values.

9. The method of claim 1, further comprising:

(d) comparing the set of values with a specified set of values to produce a deviation;

(e) if the deviation exceeds a specified deviation, rejecting the set of values;

(f) repeating steps (d) and (e) up to n times, where n is an integer greater than one;

(g) if the deviation is found to be less than the specified deviation before step (e) is performed an nth time, retaining the set of values established by step (d); and

(h) performing step (c) with the retained set of values.

10. The method of claim 7, wherein said characteristic is an electrical characteristic.

11. The method of claim 10, wherein said electrical characteristic is resistance.

12. The method of claim 11, wherein the weight sensor includes an electrical resistance element that has three or more electrical contacts, wherein said set of values is determined from measurements of the resistance values between the three or more terminals.

13. A seat weight measurement system for a seat in a motor vehicle, the motor vehicle having door and a seat belt with a buckle, said system comprising:

a weight sensor installed in said seat, said weight sensor having a characteristic that varies with the weight of said seat;

one or more detectors that detect if the seat is empty, if the door is open and the seat belt is unbuckled;

a computer controller for automatically calibrating said weight sensor by performing the steps of;

(a) determining that the seat is empty and that a condition is present, where the condition is a member of the group consisting of the door being open and the seat belt being unbuckled;

(b) if step (a) determines that the seat is empty and that said condition is present, establishing a set of values of said characteristic that define a zero set value; and

(c) presenting the set of values that define a zero set value for in seat weight measurements.

14. The seat weight measurement system of claim 13, wherein the computer controller performs the further step of:

(d) repeating steps (a), (b) and (c) so long as the seat is installed in the motor vehicle.

15. The seat weight measurement system of claim 14, wherein the computer controller performs the further step of:

(e) retaining a first set of values established by a first performance of step (b) as a reference set of values.

16. The seat weight measurement system of claim 15, wherein the computer controller performs the further step of:

(f) retaining a second set of values as a temporary set of values, if the second set of values (i) is established by step (b) after the reference set of values is established and (ii) exceeds a predetermined deviation from the reference set of values; and

wherein step (c) presents the temporary set of values as defining a modified zero set value for said in seat weight measurements.

17. The seat weight measurement system of claim 16, wherein the temporary set of values is one of a plurality of the temporary sets of values established by separate performances of step (b), and wherein step (c) presents the most recently established one of the temporary sets of values for the in seat weight measurements.

18. The seat weight measurement system of claim 17, wherein the temporary set of values is one of a plurality of the temporary sets of values established by separate performances of step (b), and wherein step (c) presents the most recently established one of the temporary sets of values for the in seat weight measurements.

19. The seat weight measurement system of claim 18, wherein the computer controller performs the further step of:

(g) limiting the number of times steps (a) through (h) are performed during the time the open door condition is found present.

20. The seat weight measurement system of claim 13, wherein the computer controller performs the further steps of:

(d) if step (a) determines that either the seat is not empty or the condition is not present, establishing the set of values;

(e) if the seat is still empty or the condition is still not present, rejecting the set of values;

(f) repeating steps (d) and (e) up to n times, where n is an integer greater than one;

(g) if the seat is found empty and the condition found present before step (e) is performed an nth time, retaining the set of values established by step (d); and

(h) performing step (c) with the retained set of values.

21. The seat weight measurement system of claim 13, wherein the computer controller performs the further steps of:

(d) comparing the set of values with a specified set of values to produce a deviation;

(e) if the deviation exceeds a specified deviation, rejecting the set of values;

(f) repeating steps (d) and (e) up to n times, where n is an integer greater than one;

(g) if the deviation is found to be less than the specified deviation before step (e) is performed an nth time, retaining the set of values established by step (d); and

(h) performing step (c) with the retained set of values.

22. The seat weight measurement system of claim 19, wherein said characteristic is an electrical characteristic.

23. The seat weight measurement system of claim 22, wherein said electrical characteristic is resistance.

24. The seat weight measurement system of claim 23, wherein the weight sensor includes an electrical resistance element that has three or more electrical contacts, wherein said set of values is determined from measurements of the resistance values between the three or more terminals.

25. A memory medium for controlling a computer controller of a seat weight measurement system for a motor vehicle having a seat, a door and a seat belt with a buckle, said memory medium comprising:

means for controlling the computer controller to perform the steps of;

(a) determining that the seat is empty and that a condition is present, where the condition is a member of the group consisting of the door being open and the seat belt being unbuckled;

(b) if step (a) determines that the seat is empty and that said condition is present, establishing a set of values of said characteristic that define a zero set value; and

(c) presenting the set of values that define a zero set value for in seat weight measurements.

26. The memory medium of claim 25, further comprising:

means for controlling the computer controller to perform the further step of;

(d) repeating steps (a), (b) and (c) so long as the seat is installed in the motor vehicle.

27. The memory medium of claim 26, further comprising:

means for controlling the computer controller to perform the further step of;

(e) retaining a first set of values established by a first performance of step (b) as a reference set of values.

28. The memory medium of claim 27, further comprising:

means for controlling the computer controller to perform the further step of;

(f) retaining a second set of values as a temporary set of values, if the second set of values (i) is established by step (b) after the reference set of values is established and (ii) exceeds a predetermined deviation from the reference set of values; and

wherein step (c) presents the temporary set of values as defining a modified zero set value for said in seat weight measurements.

29. The memory medium of claim 28, wherein the temporary set of values is one of a plurality of the temporary sets of values established by separate performances of step (b), and wherein step (c) presents the most recently established one of the temporary sets of values for the in seat weight measurements.

30. The memory medium of claim 29, wherein the weight sensor is one of a plurality of weight sensors installed to sense said weight of the seat, and wherein the sets of values established by step (b) are derived from measurements of said characteristic of each of said plurality of weight sensors.

31. The memory medium of claim 30, further comprising:

means for controlling the computer controller to perform the further step of;

(g) limiting the number of times steps (a) through (h) are performed during the time the open door condition is found present.

32. The memory medium of claim 25, further comprising:

means for controlling the computer controller to perform the further steps of;

(d) if step (a) determines that either the seat is not empty or the condition is not present, establishing the set of values;

(e) if the seat is still empty or the condition is still not present, rejecting the set of values;

(f) repeating steps (d) and (e) up to n times, where n is an integer greater than one;

(g) if the seat is found empty and the condition found present before step (e) is performed an nth time, retaining the set of values established by step (d); and

(h) performing step (c) with the retained set of values.

33. The memory medium of claim 25, further comprising:

means for controlling the computer controller to perform the further steps of;

(d) comparing the set of values with a specified set of values to produce a deviation;

(e) if the deviation exceeds a specified deviation, rejecting the set of values;

(f) repeating steps (d) and (e) up to n times, where n is an integer greater than one;

(g) if the deviation is found to be less than the specified deviation before step (e) is performed an nth time, retaining the set of values established by step (d); and

(h) performing step (c) with the retained set of values.

34. The memory medium of claim 31, wherein said characteristic is an electrical characteristic.

35. The memory medium of claim 34, wherein said electrical characteristic is resistance.

37. The memory medium of claim 34, wherein the weight sensor includes an electrical resistance element that has three or more electrical contacts, wherein said set of values is determined from measurements of the resistance values between the three or more terminals.

36. A method of automatically calibrating a characteristic of a weight sensor installed to sense weight of a seat in a motor vehicle, said method comprising:

(a) determining that the seat is empty;

(b) if step (a) determines that the seat is empty, establishing a set of values of said characteristic that define a zero set value; and

(c) presenting the set of values that define a zero set value for in seat weight measurements.