U.S. patent application number 09/814904 was filed with the patent office on 2001-08-02 for vehicle occupant position detector and airbag control system.
Invention is credited to Blakesley, Patrick B., Osmer, William, Wills, Michael R..
Application Number | 20010010424 09/814904 |
Document ID | / |
Family ID | 23478522 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010010424 |
Kind Code |
A1 |
Osmer, William ; et
al. |
August 2, 2001 |
Vehicle occupant position detector and airbag control system
Abstract
An automobile seat occupant sensor and airbag control system for
detecting the location and weight of a person in a car and a seat
inclination angle. The system includes an airbag and an airbag
deployment mechanism for deploying the airbag. Several sensors are
fixedly located in a weight path of the vehicle seat. The sensors
are located between a seat bottom and a vehicle floor. A controller
is connected between the airbag deployment mechanism and the
sensors for controlling deployment of the airbag. The controller
calculates a center of gravity of the seat occupant, weight of the
occupant and a seat inclination angle and uses this information to
control deployment of the airbag.
Inventors: |
Osmer, William; (Granger,
IN) ; Wills, Michael R.; (Richmond, MI) ;
Blakesley, Patrick B.; (Goshen, IN) |
Correspondence
Address: |
Mark P. Bourgeois
CTS Corporation
905 West Boulevard North
Elkhart
IN
46514
US
|
Family ID: |
23478522 |
Appl. No.: |
09/814904 |
Filed: |
March 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09814904 |
Mar 22, 2001 |
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09374870 |
Aug 16, 1999 |
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6250671 |
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Current U.S.
Class: |
280/735 ;
280/728.2 |
Current CPC
Class: |
B60R 21/01516 20141001;
G01G 19/4142 20130101; B60R 21/0152 20141001 |
Class at
Publication: |
280/735 ;
280/728.2 |
International
Class: |
B60R 021/16; B60R
021/32 |
Claims
What is claimed is:
1. A vehicle airbag control system for sensing the weight and
position of an occupant in a vehicle seat and controlling an
airbag, comprising: a) an airbag; b) airbag deployment means for
deploying the airbag; c) a plurality of sensors, fixedly located in
a weight path of the vehicle seat, the sensors located between a
seat bottom and a vehicle floor, the sensors further located
substantially near an outer perimeter of the seat, each sensor
providing an electrical output signal representative of the weight
applied by the vehicle occupant at the sensor location, the sensors
having strain gauge resistors mounted to a cantilevered beam; (d) a
seat zone located within the outer perimeter of the seat, the seat
zone defined as a region of the seat which when the occupant is
positioned within the airbag can be safely deployed; and (e)
controller means, connected between the airbag deployment means and
the sensors for controlling deployment of the airbag in response to
the electrical output signals, the controller means calculating a
center of gravity of the seat occupant to locate the position of
the occupant in the seat and determining if the center of gravity
of the occupant is in a first position located inside the seat zone
where the airbag is allowed to deploy or is in a second position
located outside the seat zone where the airbag is prevented from
deploying.
2. The vehicle airbag control system according to claim 1, wherein
the controller means calculates weight of the seat occupant.
3. The vehicle airbag control system according to claim 1, wherein
the controller means allows deployment of the airbag if the
occupants weight is above a first magnitude and prevents deployment
of the airbag if the occupants weight is below the first
magnitude.
4. A method for controlling deployment of an air bag, comprising:
a) providing a plurality of seat weight sensors attached between a
vehicle seat and a vehicle floor, the sensors located substantially
at an outer perimeter of the seat, the sensor s being strain gage
resistors mounted to a cantilevered beam between the seat and a
vehicle floor; b) providing an airbag controller; c) seating an
occupant into the seat; d) generating a plurality of electrical
signals from the seat weight sensors proportional to the weight and
location of the seat occupant; e) providing the electrical signal
to an airbag controller that is connected to the airbag; f)
calculating a center of gravity and weight of the seat occupant
from the electrical signals to locate the position of the occupant
in the seat; g) determining if the occupant is in a first position
within the outer perimeter of the seat where the airbag is allowed
to deploy or is in a second position outside the outer perimeter of
the seat where the airbag is prevented from deploying; and h)
determining if the occupant weight is above a first magnitude where
the airbag is allowed to deploy or is below the first magnitude
where the airbag is prevented from deploying.
5. The method for controlling deployment of an air bag according to
claim 4 wherein, the airbag is deployed with maximum force, If a
heavy occupant is detected in the seat and the airbag is deployed
at less than maximum force, If a light occupant is detected in the
seat.
6. The method for controlling deployment of an air bag according to
claim 5, wherein, airbag deployment is prevented, If occupants
weight is less than a first magnitude.
7. The method for controlling deployment of an air bag according to
claim 4, further comprising: determining if the center of gravity
is located outside the vehicle seat.
8. A control system for controlling an airbag, the control system
controlling the airbag in relation to the weight and position of a
seat occupant, comprising: a) an airbag; b) an airbag inflator,
connected to the air bag, for inflating an airbag; c) a sensor,
attached to a seat, for sensing a weight of the seat occupant at a
sensor location, the sensor located substantially near an outer
perimeter of the seat and providing an electrical output signal
representative of the weight applied by the vehicle occupant at the
sensor location, the sensor including a plurality of strain gauge
resistors mounted to a substantially vertically oriented base; d) a
processor connected to the sensors and to the airbag inflation
means; e) software operative on the processor for: e1) calculating
the weight of the seat occupant; e2) determining if the weight of
the seat occupant is less than a first magnitude; e3) preventing
actuation of the airbag inflation means, if the weight of the seat
occupant is less than a first magnitude; and e4) allowing actuation
of the airbag inflation means, if the weight of the seat occupant
is greater than the first magnitude; f) calculating a center of
gravity of the seat occupant; g) determining if the center of
gravity is inside or outside a first area, the first area defined
as being substantially within the outer perimeter of the seat; h)
preventing actuation of the airbag inflation means, if the center
of gravity is outside the first area; and i) allowing actuation of
the airbag inflation means, if the center of gravity is inside the
first area.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an automobile seat occupant sensor
and airbag control for detecting the location and weight of a
person in car seat, and in particular to a sensor that can detect
the presence and location of an occupant using strain sensitive
resistors and provide an electrical signal to control activation of
an airbag.
[0003] 2. Description of the Related Art
[0004] Various devices are well known for their ability to measure
force, pressure, acceleration, temperature, position, etc. by using
a sensing structure combined with signal processing electronics.
One general type of sensor or transducer for such applications is a
resistive strain gauge sensor in which force or pressure is sensed
or measured based on strain placed on the resistors. Resistive
strain gauges function by generating changes in resistance
proportional to force which causes dimensional changes of the
resistor.
[0005] Many types of strain gauge sensors have been designed and
made commercially available. Various strain gauge sensors have
proven to be generally satisfactory. Prior art sensors; however,
have tended to be rather expensive and not suitable in certain
applications such as sensing the presence of an occupant in an
automobile seat. A sensor suitable for such an application must be
compact, robust, impervious to shock and vibration and yet
inexpensive.
[0006] Automobile seats can use sensors to activate air bags, which
would be deployed during an accident. Injury to infants or small
children from air bag deployment with excessive force is a current
industry problem. A weight sensor in the seat can be used to
control the deployment force during air bag activation. If a heavy
person is in the seat, the airbag is deployed at full force. If a
light person is in the seat, such as a child, the airbag is
deployed at a slower, less forceful rate.
[0007] Another problem with airbag deployment is determining the
position and posture of a person in a vehicle seat. If the seat
occupant is located in the front of the seat, it is desired to
activate the air bag with less force. If the seat occupant is
located in the rear of the seat, it is desired to activate the air
bag with more force. Similarly, if the seat back is an automobile
seat is reclined, it may be desired to control the activation of
the airbag based upon the seat back angle. For example, if the seat
back is reclined fully, it may be desired to activate the air bag
with more force. If the seat back is in an upright position, it may
be desired to activate the airbag with less force.
[0008] U.S. Pat. No. 5,573,269 discloses a system that uses
multiple sensors. Several weight sensors are placed in the seat,
the floor and a seat angle sensor is attached to the seat back.
This system has many disadvantages. It is expensive to produce and
install all the sensors. The weight sensor in the seat is attached
to the springs which can give inaccurate readings of weight
depending on the placement of the sensors in the seat.
[0009] Other seat occupant detection systems have been devised
based upon ultrasonic sensing technologies. The occupants distance
from the dashboard is measured by a sensor. Other sensors try to
measure the size of the occupant. Unfortunately, the ultrasonic
systems produce frequent errors in calculating the size of the
occupant as they have difficulty in interpreting an occupant
shifting in the seat, moving the seat forward or backward and
reclining the seat.
[0010] A current unmet need exists for a reliable, low cost, simple
and robust automobile seat weight sensor and system that is used to
control airbag deployment. A current unmet need also exists for an
air bag control system that can monitor occupant weight, seat
position and seat back angle with a minimum number of sensors at a
low cost.
[0011] 3. Related Art
[0012] Examples of patents that are related to the present
invention are as follows, and each patent is herein incorporated by
reference for the supporting teachings:
[0013] U.S. Pat. No. 5,573,269 is a apparatus for sensing and
restraining an occupant of a vehicle seat.
[0014] U.S. Pat. No. 4,556,598 is a porcelain tape for producing
porcelainized metal substrates.
[0015] U.S. Pat. No. 5,232,243 is an occupant sensing
apparatus.
[0016] U.S. Pat. No. 5,276,432 is a patient exit detection
mechanism for hospital bed.
[0017] U.S. Pat. No. 5,739,757 is an vehicle passenger weight
sensor.
[0018] The foregoing patents reflect the state of the art of which
the applicant is aware and are tendered with the view toward
discharging the applicant's acknowledged duty of candor in
disclosing information which may be pertinent in the examination of
this application. It is respectfully stipulated, however, that none
of these patents teach or render obvious, singly or when considered
in combination, the applicant's claimed invention.
SUMMARY OF THE INVENTION
[0019] It is a feature of the invention to provide a reliable and
cost-effective automobile seat occupant sensor and airbag control
system for detecting the location and weight of a person in car
seat, and in particular to a sensor that can detect the presence
and location of an occupant using strain sensitive resistors and
provide an electrical signal to control activation of an
airbag.
[0020] An additional feature of the invention is to provide a
vehicle airbag control system for sensing the weight and position
of an occupant in a vehicle seat and controlling an airbag, the
system includes an airbag and an airbag deployment means for
deploying the airbag. Several sensors are fixedly located in a
weight path of the vehicle seat. The sensors are located between a
seat bottom and a vehicle floor. The sensors are located
substantially near an outer perimeter of the seat, each sensor
provides an electrical output signal representative of the weight
applied by the vehicle occupant at the sensor location. A
controller means is connected between the airbag deployment means
and the sensors for controlling deployment of the airbag in
response to the electrical output signals. The controller means
calculates a center of gravity of the seat occupant to locate the
position of the occupant in the seat and determines if the occupant
is in a first position where the airbag is allowed to deploy or is
in a second position where the airbag is prevented from
deploying.
[0021] Another feature of the invention is to provide a control
system for controlling an airbag. The control system controls the
airbag in relation to the weight and position of a seat occupant.
The system includes an airbag and an airbag inflation means that
are connected to the air bag to inflate the airbag. A sensor means
is attached to a seat, for sensing a weight of the seat occupant at
a sensor location. A processor is connected to the sensors and to
the airbag inflation means. A software means operates on the
processor to calculate the weight of the seat occupant and
determine if the weight of the seat occupant is less than a first
magnitude. The software means also prevents actuation of the airbag
inflation means, if the weight of the seat occupant is less than a
first magnitude and allows actuation of the airbag inflation means,
if the weight of the seat occupant is greater than the first
magnitude. The software means further can calculate a center of
gravity of the seat occupant and determine if the center of gravity
is inside or outside a first area. This information is used to
prevent actuation of the airbag inflation means, if the center of
gravity is outside the first area; and allow actuation of the
airbag inflation means, if the center of gravity is inside the
first area. The software means can further be used to calculate a
seat inclination angle of the seat. This information is used to
determine if the seat inclination angle is greater than or less
than a first magnitude. The airbag inflation means is prevented
from actuating, if the seat inclination angle is less than the
first magnitude and allowed to actuate if the seat angle is greater
than the first magnitude.
[0022] The invention resides not in any one of these features per
se, but rather in the particular combination of all of them herein
disclosed and claimed and it is distinguished from the prior art in
this particular combination of all of its structures for the
functions specified. Other features of the present invention will
become more clear from the following detailed description of the
invention, taken in conjunction with the accompanying drawings and
claims, or may be learned by the practice of the invention.
[0023] There has thus been outlined, rather broadly, the more
important features of the invention in order that the detailed
description thereof that follows may be better understood, and in
order that the present contribution to the art may be better
appreciated. There are, of course, additional features of the
invention that will be described hereinafter and which will form
the subject matter of the claims appended hereto. Those skilled in
the art will appreciate that the conception, upon which this
disclosure is based, may readily be utilized as a basis for the
designing of other structures, methods and systems for carrying out
the several purposes of the present invention. It is important,
therefore, that the claims be regarded as including such equivalent
constructions insofar as they do not depart from the spirit and
scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a diagrammatic view of an air bag control
system.
[0025] FIG. 2 is a perspective view of the automobile seat of FIG.
1.
[0026] FIG. 3 is a perspective view of the automobile seat weight
sensor of FIG. 1.
[0027] FIG. 4 is a perspective view of an alternative embodiment of
the automobile seat weight sensor of FIG. 1.
[0028] FIG. 5 is a flow chart of a control routine for the air bag
control system.
[0029] It is noted that the drawings of the invention are not to
scale. The drawings are merely schematic representations, not
intended to portray specific parameters of the invention. The
drawings are intended to depict only typical embodiments of the
invention, and therefore should not be considered as limiting the
scope of the invention. The invention will be described with
additional specificity and detail through the use of the
accompanying drawings. In the drawings like numbering represents
like elements between the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] Referring to FIGS. 1, 2 and 3 there is a Vehicle Occupant
Position Detector and Airbag Control System 20 shown. System 20 has
an airbag assembly 22 mounted on part of a steering wheel or
dashboard 24 of a vehicle. Assembly 22 has an airbag 26 folded
within a housing 28. A cover 30 covers the airbag. An inert gas
source 32, typically generated by a combustion reaction is mounted
to the rear of housing 28. Gas source 32 fills airbag 26 upon
deployment to a filled or inflated position 26A. Airbag 26 cushions
an occupant in seat 33 in case of a collision or crash. An airbag
controller 36, usually incorporating a microcontroller and software
operating on the microcontroller, is connected to a conventional
crash sensor 38. Crash sensor 38 typically is an inertia switch or
an accelerometer. In a crash, the crash sensor 38 sends a signal
indicating a crash is taking place. The controller 36 then actuates
the gas source 32 which fills airbag 26.
[0031] The occupant seat 33 can be a driver seat, passenger seat or
rear seats in an automobile or other seats in a bus or truck. Seat
33 has a seat back 34, seat bottom 35, and head rest 43. A seat
pivot pin 41 allows seat back 34 to be adjusted to tilt at a chosen
seat back angle by the occupant. A conventional seat rail 44 is
attached to seat bottom 35 and allows seat 33 to be moved toward
and away from dashboard 24. Connected between seat rail 44 and
vehicle floor 39 are four weight sensors 50A, 50B, 50C and 50D.
Sensors 50 A,B,C and D are placed toward the outer perimeter of the
seats. Weight sensors 50 measure the weight that the seat occupant
places at the four corners of the seat. Sensors 50 have a
cantilevered beam or base 55 upon which several strain gage
resistors 60 are placed that are interconnected by conductors 62. A
dielectric (not shown) covers the surface of beam or base 55. The
resistors 60 may be arranged on the top, sides or bottom of sensor
50. Attached to resistors 60 are wires 58. Wires 58 are connected
to controller 36. Resistors 60 are arranged in a bridge circuit
(not shown) that is well known in the art. The base 55 is made of
steel. Resistors 60 and conductors 62 are formed from conventional
thick film materials. Upper support posts 54 connect between an end
51A of sensor 50 and seat rail 44. Lower support posts 52 connect
between an end 51B of sensor 50 and floor 39. Posts 52 and 54 are
formed from steel. Posts 52 and 54 may be welded to sensor 50 or
attached using conventional fasteners. Posts 52 and 54 connect seat
33 to floor 39 and allow the full seat weight to be applied as a
bending moment or strain through sensor 50. Upper post 54 and lower
posts 52 have apertures 53 into which bolts 64 are fastened to
attach the posts to the floor 39 and seat rail 44. If desired posts
52 and 54 could be welded to floor 39 and seat rail 44. When an
occupant sits on seat bottom 35, the occupants weight causes the
strain or bending force in sensor 50 to increase. A voltage is
applied through wires 58 to resistors 60. The force is measured by
resistors 60 as an electrical signal that changes with the
occupants weight and is transmitted over a wire harness 58 to air
bag controller 36. The voltage level of each resistor can be
correlated to a specific weight at each sensor location.
[0032] Referring to FIG. 4, an alternative embodiment of sensor 50
is shown. In FIG. 4, a sensor 80 is shown. Sensor 80 has a base 82
upon which several strain gage resistors 84 are placed that are
interconnected by conductors 86. A dielectric (not shown) covers
the surface of base 82. The resistors 84 may be arranged on the
either side of base 82. Attached to resistors 84 are wires 58.
Wires 58 are connected to controller 36. Resistors 84 are arranged
in a bridge circuit (not shown) that is well known in the art. The
base 82 is made of steel. Resistors 84 and conductors 86 are formed
from conventional thick film materials. Base 82 has an upper plate
88 and a lower plate 90 attached. Upper plate 88 connects sensor 80
to seat rail 44 using fasteners (not shown) through aperture 92.
Similarly, lower plate 90 connects between sensor 80 and floor 39
using fasteners (not shown) through aperture 92. Plates 88 and 90
allow the full seat weight to be applied as a bending moment or
strain through sensor 80. If desired, plates 88 and 90 could be
welded to floor 39 and seat rail 44. The operation of sensor 80 is
the same as that for sensor 50.
[0033] The air bag controller 36 controls deployment of airbag 22
based upon the occupants weight, position and the crash sensor
signal. The occupants total weight can be calculated by summing the
weights at the four individual sensors. The occupants position is
determined by calculating the center of gravity of the seat
occupant. The center of gravity is calculated by controller 36.
Calculating the center of gravity using four load cells is
disclosed in U.S. Pat. No. 5,276,432 and is specifically
incorporated by reference. In particular, the center of gravity
(Cg) is determined with respect to a set of Cartesian coordinates x
and y that correspond to the area occupied by the seat. The center
of gravity has coordinates of Xcg and Yxg and is calculated by the
following equations: 1 Xcg = i = 0 4 ( M ( i ) X ( i ) / TM ) Ycg =
i = 0 4 ( M ( i ) Y ( i ) / TM ) TM = i = 0 4 ( M ( i ) )
[0034] Where X(i) is the X coordinate for sensors 50, A, B, C and
D. Y(i) is the Y coordinate for sensors 50, A, B, C and D. M(i) is
the weight at each sensor location and TM is the total weight.
Controller 36 uses the location of the center of gravity (Xcg, Ycg)
to determine the occupants location in seat 33. If the occupant's
center of gravity is within a zone 37 of seat bottom 35, the air
bag is deployed with full force. If the center of gravity is
outside of zone 37, the air bag is deployed at reduced force or
prevented from deployment.
[0035] If the occupant's total weight is above a minimum weight,
the air bag is deployed with full force. If the weight is below the
minimum weight, the air bag is deployed at reduced force or
prevented from deployment.
[0036] The seat inclination angle is calculated by controller 36
using the weight values from the four sensors 50A, 50B, 50C and
50D. The weight values from the back two sensors 50A and 50B are
summed into a variable Y. The weight values from the front two
sensors 50C and 50D are summed into a variable X. The ratio X/Y is
compared to a chart stored in a memory in controller 36 that
contains measured X/Y ratios for various seat inclination angles.
For example, when the occupant is upright and seated in the middle
of the seat, x and y are equal and x/y= 1. As the occupant reclines
in the seat, the ratio of x/y will decrease as more weight is
placed on sensors 50A and 50B and less weight is placed on sensors
50C and 50D. Eventually, when the seat is reclined enough, the
force on the front sensors 50C and 50D will change from a
downwardly exerting force to an upwardly exerting force or negative
force. At this point x/y= 0. This value will be reached at a seat
angle of approximately 45 degrees from vertical. As the seat
continues to recline further, the ratio of x/y will be less than
zero as the front sensors 50C and 50D continue to measure and
upwardly acting force or negative weight. When the occupant is
seated upright, ie. x/y=1, the airbag may be deployed with less
force or prevented from deploying. As the occupant reclines and x/y
is between 0 and 1, the air bag force is increased. When x/y is
less than 0, the airbag is deployed with full force.
[0037] Referring to FIG. 5, a flow chart of a control routine for
the air bag control system 20 is shown. At step 100 the routine is
started. At step 102, sensors 50 A, B, C and D are scanned. At step
104, the controller uses the sensor data to calculate a center of
gravity, total weight and seat angle. At step 106, the center of
gravity is compared to determine if it is outside of zone 37. If it
is inside of zone 37, a no is returned and the air bag is set to
deploy at full pressure at step 107. If it is outside of zone 37, a
yes is returned and the routine goes to step 108. At step 108, the
seat angle is compared to determine if the seat is upright or
reclined. If it is reclined beyond a certain angle, a no is
returned and the air bag is set to deploy at full pressure at step
108. If it is upright or less than a certain angle, a yes is
returned and the routine goes to step 110. At step 110, the total
weight is compared to determine if it is above a minimum value. If
it is above a minimum value, a yes is returned and the air bag is
set to deploy at full pressure at step 107. If it is below a
minimum value, a no is returned and the air bag is set to deploy at
reduced pressure or prevented from deploying at all at step
112.
[0038] The airbag control system 20 is able to change the force
with which the airbag is deployed depending upon the occupants
weight, seat position, and how far the seat back is reclining.
These three control parameters are calculated from four resistive
strain gage weight sensors located toward the perimeter of the
vehicle seat.
VARIATIONS OF THE PREFERRED EMBODIMENT
[0039] Although the illustrated embodiment depicts using the airbag
control system to control as dashboard or steering wheel mounted
airbag, one skilled in the art will realize that the preferred
embodiment would work with other airbags such as side mounted or
rear seat airbags or head protection air bags.
[0040] Furthermore, the shape of sensor 50 could be varied to any
configuration that would transfer the weight from the car seat to
the floor and allow the strain sensitive resistors to be mounted.
For example sensor 50 could be Z-shaped or C-shaped or
S-shaped.
[0041] Although thick film resistors 60 were shown mounted on base
55, another variation of the weight sensor 50 would be to use
individual chip resistors mounted on base 55 or polymer resistors
or metal foil strain gauges.
[0042] Yet, a further variation, is to integrate sensor 50 into
seat rail 44.
[0043] Although the illustrated embodiment depicts using the airbag
control system to control airbags at two inflation rates. Other
rates of inflation could be controlled such as variable inflation
rates or multiple inflators.
[0044] While the invention has been taught with specific reference
to these embodiments, someone skilled in the art will recognize
that changes can be made in form and detail without departing from
the spirit and the scope of the invention. The described
embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
* * * * *