Center of weight sensor

• US 5,821,633 A
• Filed: 01/08/1997
• Issued: 10/13/1998
• Est. Priority Date: 01/08/1997
• Status: Expired due to Term

• Current Assignee: Trustees of Boston University
• Original Assignee: Trustees of Boston University
• Inventors: Hubbard, James E. Jr., Burke, Shawn E.
• Primary Examiner(s): Elms, Richard T.
• Application Number:
  US08/780,435
• Time in Patent Office: 643 Days
• Field of Search: 307/10.1, 307/9.1, 307/121, 280/734, 280/735, 180/271, 180/282, 180/273, 340/436, 340/438, 340/669, 364/424.055-424.057, 701/45-47
• US Class Current: 307/10.1
• 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 21/01526 using piezoelectric elements
• 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: G06V 40/10 Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands

Abstract

A sensor system preferably for use in a vehicle airbag deployment system employs spatial shading techniques and centroiding analysis to calculate an equivalent point load in two dimensional space. The location of the equivalent point load, as well as the weight of the passenger as determined from the sensors, are used to construct a set of fuzzy set logic boundaries defining different modes of deploying the airbag. The fuzz set logic boundaries may include a full deployment, soft deployment, no deployment and other intermediate deployment zones. In the event of a vehicle airbag incident, the airbag is deployed in accordance with the fuzzy set logic boundary in which the weight and equivalent point load of the vehicle occupant are located.

Claims

1. A sensing system for determining the magnitude and localized equivalent point load position in two-dimensional space of a distributed load comprising:

(a) a plurality of sensing elements each having a predetermined area and located in a two-dimensional area subject to distributed loads, each sensing element further producing an output signal proportional to an integral of the applied stress over the area of the sensing element; and

(b) means for approximating the center of force or position of the equivalent point load in said two-dimensional area by weighting and summing the output signals from said sensing elements that approximate the output of two idealized sensors extending respectively to the X and Z boundaries of said two-dimensional space and each of said two idealized sensors producing an output signal that is weighted along the X and Z axes respectively to get two numerators, and dividing each of said numerators by a denominator which is obtained by summing the output signals from said sensing elements that approximate the output of one idealized sensor extending to the X and Z boundaries of said two-dimensional space and which produces an output signal that is uniformly weighted over both the X and Z directions.

2. The sensing system of claim 1, said numerator signals weighted to obtain spatial moments above n>

1.

3. The sensing system of claim 1, said numerator signals linearly weighted along the X and Z axes.

4. The sensing system of claim 1, said numerator signals weighted to at least the second power along the X and Z axes.

5. The sensing system of claim 1, said plurality of sensing elements comprising three sensors located in said two-dimensional area.

6. The sensing system of claim 1, further comprising means for continuously determining the position and equivalent point load of the distributed load.

7. The sensing system of claim 1, further comprising a plurality of sensors disposed in a seat of an automobile.

8. The sensing system of claim 7, wherein the distributed load is generated by a vehicle occupant seated in said seat, said plurality of sensors positioned in an aperture outlining the boundaries in which the distributed load of the vehicle occupant is located.

9. The sensing system of claim 7, said means for approximating further comprising:

(a) means for determining the position of an equivalent point load along at least one axis of a distributed load created by a vehicle occupant sitting in the seat, said position of said equivalent point load approximating the position of the vehicle occupant; and

(b) means for controlling the deployment of an airbag upon occurrence of an airbag incident depending upon the weight and the position along said at least one axis of said equivalent point load.

10. The sensing system of claim 1, said plurality of sensors positioned in an aperture in which the distributed point load is applied, said aperture having a portion of which is not covered with sensors.

11. The sensing system of claim 10, at least two of said plurality of sensing elements overlapping with one another.

12. A sensing system according to claim 1, wherein said sensing elements are variably shaped and spaced such that the output signals from two subcombinations of the sensing elements are added together with unity weighting by the approximating means to obtain said numerators.

13. A sensing system according to claim 12, wherein each sensing element includes a film transducer having a patterned electrode on one surface thereof such that the output signal produced by each sensing element is a function of the area and shape of the patterned electrode.

14. A sensing system according to claim 1, wherein said sensing elements are of uniform shape and spacing such that the output signals from two subcombinations of the sensing elements are added together with variable weighting by the approximating means to obtain said numerators, and the output signals from a third subcombination of the sensing elements are added together with uniform weighting by the approximating means to obtain said denominator.

15. A sensing system for controlling the deployment of an airbag in an automobile comprising:

(a) at least three sensors disposed in a seat of the automobile, each sensor producing an output signal varying over a range that is a function of the magnitude of the stress applied over the area of the sensor in response to a vehicle occupant sitting in the seat;

(b) means for determining from said sensor output signals the weight of the vehicle occupant and the position of an equivalent point load along at least one axis of a distributed load created by the vehicle occupant sitting in the seat, said position of said equivalent point load approximating the position of the vehicle occupant; and

(c) means for controlling the deployment of the airbag upon occurrence of an airbag incident depending upon the determined weight and position.

16. The sensor system according to claim 15 further comprising means for determining the position of the equivalent point load of the vehicle occupant along two axes.

17. The sensor system according to claim 15 further comprising means for continuously determining the position of the equivalent point load of the vehicle occupant.

18. The sensor system according to claim 17 further comprising means for determining the position of the equivalent point load of the vehicle occupant in two-dimensional space.

19. The sensor system according to claim 15 further comprising a plurality of sensors disposed in the seat of the vehicle.

20. The sensor system according to claim 19, said plurality of sensors positioned in an aperture outlining the boundaries in which the distributed load of the vehicle occupant is located.

21. The sensor system according to claim 20, at least two of said plurality of sensors overlapping one another.

22. The sensor system according to claim 20, said aperture comprising a rectangular aperture and said plurality of sensors comprising four sensors positioned in respective quadrants of said aperture.

23. The sensor system according to claim 22, said aperture having a portion of which is not covered with sensors.

24. A sensor system according to claim 15, wherein said sensors are variably shaped and spaced such that the output signals from two subcombinations of the sensors are added together with unity weighting by the determining means in determining the weight of the vehicle occupant and the position of the equivalent point load of the vehicle occupant.

25. A sensing system according to claim 24, wherein each sensor includes a film transducer having a patterned electrode on one surface thereof such that the output signal produced by each sensor is a function of the area and shape of the patterned electrode.

26. A sensor system according to claim 15, wherein said sensors are of uniform shape and spacing such that the output signals from two subcombinations of the sensors are added together with variable weighting by the determining means in determining the weight of the vehicle occupant and the position of the equivalent point load of the vehicle occupant.

27. A sensor system according to claim 15, wherein the analog output signal from each sensor is proportional to the integral of the stress applied over the area of the sensor.

28. A method for controlling the deploying of an airbag in a vehicle comprising the steps of:

(a) providing at least three sensors disposed in a passenger seat of the vehicle, each sensor producing an output signal varying over a range that is a function of the magnitude of the stress applied over the area of the sensor in response to a vehicle occupant sitting in the seat;

(b) determining from said sensor output signals the weight of the vehicle occupant and the position of an equivalent point load of the vehicle occupant, said equivalent point load describing the position of the vehicle occupant relative to the airbag; and

(c) controlling the deployment of the airbag upon occurrence of an airbag incident depending on the determined weight and position.

29. The method according to claim 28 further comprising the step of deactivating the airbag when the position of said equivalent point load of the center of the vehicle occupant is located in the firing zone of the airbag.

30. The method according to claim 28 further comprising the step of deactivating the airbag when the weight of the vehicle occupant is less than a predetermined value.

31. The method according to claim 28 further comprising the step of continuously determining the position of the equivalent point load of the vehicle occupant.

32. The method according to claim 28 further comprising the step of determining the position of the equivalent point load of the vehicle occupant in two-dimensional space.

33. A method according to claim 28, wherein said sensors are variably shaped and spaced such that the output signals from two subcombinations of the sensing elements are added together with unity weighting in determining the weight of the vehicle occupant and the position of the equivalent point load of the vehicle occupant.

34. A method according to claim 33, wherein each sensor includes a film transducer having a patterned electrode on one surface thereof such that the output signal produced by each sensor is a function of the area and shape of the patterned electrode.

35. A method according to claim 28, wherein said sensors are of uniform shape and spacing such that the output signals from two subcombinations of the sensors are added together with variable weighting in determining the weight of the vehicle occupant and the position of the equivalent point load of the vehicle occupant.

36. A method according to claim 28, wherein the analog output signal from each sensor is proportional to the integral of the stress applied over the area of the sensor.

37. A method for determining the magnitude and localized equivalent point load position in two-dimensional space of a dynamic or static load comprising:

(a) providing a plurality of sensing elements each having a predetermined area and each located in a two-dimensional area subject to distributed loads;

(b) sensing an output signal of the sensing elements, said output signal proportional to an integral of the applied stress over the area of the sensing element;

(c) approximating the center of force in said two-dimensional area by weighting and summing the output signals from said sensing elements that approximate the output of two idealized sensors extending respectively to the X and Z boundaries of said two-dimensional space, each of said two idealized sensors producing an output signal that is weighted along the X and Z axes respectively to get two numerators; and

(d) dividing each of said numerators by a denominator which is obtained by summing the output signals from said sensing elements that approximate the output of one idealized sensor extending to the X and Z boundaries of said two-dimensional space and which produces an output signal that is uniformly weighted over both the X and Z direction.

38. A method of controlling the deployment force of an airbag in an automobile, comprising the steps of:

calculating the weight of an occupant of a seat in the automobile;

calculating the location of an equivalent point load of the occupant;

calculating the location and extent of at least two deployment zones of the airbag based on the weight and equivalent point load of the occupant, a first deployment zone being associated with a first predetermined deployment force of the airbag and a second deployment zone being associated with a second predetermined deployment force of the airbag different from the first predetermined deployment force;

determining whether the equivalent point load is located in the first deployment zone, and if so enabling the air bag for deployment at the first deployment force; and

determining whether the equivalent point load is located in the second deployment zone, and if so enabling the air bag for deployment at the second deployment force.