Center of weight sensor

Details Center of weight sensor Center of weight sensor

1998-10-09

2001-05-01

Noori, Max (Department: 2855)

Measuring and testing

Dynamometers

Responsive to multiple loads or load components

Reexamination Certificate

active

06223606

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to the field of sensors, and particularly to a sensor architecture preferably utilized in a vehicle airbag control system which determines the weight and two dimensional spatial location of an equivalent point load as representing the passenger. The location and weight of the passenger are used to construct airbag firing zones which determine whether and how the airbag will deploy.
Frontal airbags are now a standard feature in most modern automobiles. The recent trend in modern airbag design is moving towards sophisticated systems that implement energy management, i.e., the application of less than 100% of the airbag's potential cushioning force upon deployment of the airbag. It has been desirable for some time to manage the speed of the airbag's deployment based on factors such vehicle speed, intensity of the collision, and passenger weight. Until now, such objectives have not been achieved.
It has been for some time the goal of design engineers to manage the energy of the deploying airbag so that they deploy at variable rates ranging anywhere from less than 50% of the potential cushioning effect of the airbag to 100% of the cushioning effect of the airbag. These considerations are important inasmuch as the characteristics of the driver or passenger may range in weight from a small infant to a large adult.
Today's airbags deploy at only one rate: 100% force. Typically, airbags are deployed at speeds approaching 200 m.p.h. An object or passenger struck by an airbag inflating at such speeds absorbs forces approaching 2500 lbf In order to be deployed at anything less than 100% force, there is a need for more intelligent, highly integrated, low-cost, high performance electronic sensor technologies.
Under ideal firing conditions, the airbag should fully deploy or be nearly fully deployed before the passenger's body moves forward as a result of the accident so that the force of deployment is not absorbed by the occupant. In practice, however, the airbag often strikes the vehicle occupant before being fully deployed. This is due to the fact that each passenger in a vehicle, whether the driver or otherwise, assumes a unique ergonomic position and are of different sizes and weights. Vehicle occupants who are tall usually adjust their seats rearwardly and may even recline their seats. This creates an ideal body position for purposes of complete airbag deployment inasmuch as the passenger will likely not be struck by the airbag while it is deploying.
In the case of shorter passengers, on the other hand, the seats are often adjusted forward, placing the passenger in the firing zone of the airbag. Likewise, when the passenger is an infant of small child in a rear facing child seat, the deployment of the airbag often causes a violent collision and subsequent rearward force applied to the backside of the seat.
Furthermore, the weight of the occupant is an important factor in the ability of a child or small adult to sustain the trauma delivered by airbag deployment. Children and small adults are particularly susceptible to injury not only due to being situated in the zone of the deployment, but also as a virtue of their size they are unable to sustain the large impact force delivered by the airbag.
In order to evaluate whether an individual is situated in the firing zone of an airbag, or whether, given the weight of the individual, the deployment of the airbag would cause more injury than non-deployment, “smart” sensors are needed. However, to date, no such sensors are commercially available which are capable of providing both a means of continuously determining whether a vehicle occupant is positioned in the airbag deployment zone and the weight of the occupant.
These and other problems are sought to be overcome by the invention of the preferred embodiments.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a sensor system capable of taking a distributed load and reducing it to an equivalent point load in two spatial dimensions.
It is a further object of the present invention to provide a sensor system capable of determining the weight of the distributed load.
It is a further object of the present invention to provide a sensor system capable of continuously updating the position of the equivalent point load under both static and dynamic operating conditions.
It is a further object of the present invention to provide a sensor system for use in a vehicle airbag system to determine whether a vehicle occupant as represented by an equivalent point load is in the firing zone of the airbag and, if so, to selectively control the deployment of the airbag or deactivate the airbag altogether depending upon the position of the vehicle occupant.
It is still further yet an object of the present invention to provide a sensor system for use in a vehicle airbag system to determine whether a vehicle occupant weighs less than a predetermined value and, if so, to selectively control the deployment of the airbag or deactivate the airbag altogether depending upon the weight and location of the vehicle occupant.
These and other objects of the present invention are accomplished by a sensor system comprising a plurality of discrete and/or distributed sensing elements each having a predetermined area and located in a two-dimensional area subject to distributed loads. Each sensing element provides an output signal proportional to the integral of the applied stress over the two dimensional area of the sensing element. The center of force of a distributed load in the two dimensional area is calculated by summing the weighted or shaded output signals from the sensing elements extending respectively to the X and Z boundaries of the two-dimensional area to obtain two numerators and dividing the numerators by a denominator which is obtained by summing uniformly weighted or shaded output signals from the discrete sensing elements.
At least three sensors are needed in order to gather the center of force and weight information of the distributed load in a given sensing aperture. The sensor system preferably controls an automotive airbag system. The sensor system is preferably disposed in the seat of the automobile. The point load and its location represented by the center of force and weight information is used to construct fuzzy set logic boundaries. The fuzzy set logic boundaries control whether and how the airbag will be deployed. At least two, but preferably three fuzzy set logic boundaries, and possibly more, are established, including “FULL DEPLOY”, “SOFT DEPLOY” and “NO DEPLOY” boundaries or zones. The “FULL DEPLOY” zone would typically be occupied by a grown adult or large child sitting against the seat back and out of the firing zone of the airbag. However, even the grown adult could enter the “SOFT DEPLOY” or even the “NO DEPLOY” zones if the passenger adjusted his or her position so that their equivalent point load moved in the direction of the dashboard and hence into the airbag firing zone.
The “SOFT DEPLOY” zone is typically occupied by a small adult or child when sitting against the seat back. However, if the small adult or child adjusted his or her position so that their equivalent point load moved in the direction of the dashboard, the passenger could enter the “NO DEPLOY” zone. Finally, the “NO DEPLOY” zone is typically occupied by a small child or a baby sitting in a car seat, or by an empty or unoccupied car seat. The equivalent point load and weight of a small child or baby seated to in a car seat is such that the “FULL DEPLOY” and “SOFT DEPLOY” fuzzy set logic boundaries collapse, leaving the small child or baby in the “NO DEPLOY” zone.
These and other objects, features and advantages of the present invention will become readily apparent to one of ordinary skill in the art when reading the Detailed Description of the Preferred Embodiments in conjunction with the drawings.


REFERENCES:
patent: 4565940 (1986-01-01), Hubbard, Jr.
patent: 4621533 (1986-11-01), Gindy
patent: 4626730 (1986-12-01), Hubbard, Jr.
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