U.S. patent application number 10/303677 was filed with the patent office on 2004-05-27 for collision sensing system.
Invention is credited to Lin, Chin-Hsu, Neal, Mark O., Sala, Dorel M., Wang, Jenne-Tai.
Application Number | 20040102883 10/303677 |
Document ID | / |
Family ID | 32325059 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040102883 |
Kind Code |
A1 |
Sala, Dorel M. ; et
al. |
May 27, 2004 |
COLLISION SENSING SYSTEM
Abstract
A computer based method for activating a vehicular safety device
for passenger protection is disclosed. The method uses two
front-end acceleration sensors and a passenger compartment sensor.
When a collision situation is sensed, current acceleration data is
integrated to produce velocity and displacement values for the
sensor locations. The velocity and displacement values are
selectively used in at least three vehicle collision mode analyses.
Examples of such collision modes are a full frontal mode, an angle
mode and an offset deformable barrier mode. Each collision mode has
sub-modes corresponding to the desired levels of airbag inflation.
When appropriate threshold values are exceeded, device activation
for one or more activation stages is initiated.
Inventors: |
Sala, Dorel M.; (Troy,
MI) ; Wang, Jenne-Tai; (Troy, MI) ; Neal, Mark
O.; (Rochester, MI) ; Lin, Chin-Hsu; (Troy,
MI) |
Correspondence
Address: |
KATHRYN A MARRA
Gereral Motors Corporation
Legal Staff, Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
32325059 |
Appl. No.: |
10/303677 |
Filed: |
November 25, 2002 |
Current U.S.
Class: |
701/46 ; 180/282;
280/735; 701/45 |
Current CPC
Class: |
B60R 21/0136 20130101;
B60R 2021/01315 20130101; B60R 21/0132 20130101; B60R 21/0133
20141201 |
Class at
Publication: |
701/046 ;
701/045; 280/735; 180/282 |
International
Class: |
B60R 021/32 |
Claims
1. A method of activating a safety device for vehicular passenger
protection in a passenger compartment of a vehicle having a forward
direction of travel in which it is susceptible to collision
incidents in a frontal direction mode and in one or more angular
direction modes, said vehicle having at least right side and left
side acceleration sensors forward of said compartment, an
acceleration sensor in said passenger compartment and a computer
for continually processing acceleration signals from said sensors
during vehicle operation, said method being executed on said
computer and comprising the steps of: continually comparing at
least one of said acceleration signals with a predetermined
acceleration value indicative of a passenger threatening collision
and, if a said signal exceeds said value, proceeding with the
following steps; integrating each of said acceleration signals over
time to determine a current sequence of velocity values for each of
said sensor locations; integrating each of said velocity values
over time to determine current displacement values for each of said
sensor locations; comparing said velocity values with predetermined
threshold velocity values for said sensor locations as a basis for
determining whether a frontal mode collision situation requires
safety device actuation; comparing selected of said velocity and
displacement values with predetermined corresponding velocity and
displacement threshold values as a basis for determining whether an
angular mode collision situation requires safety device activation
and, if any one of said frontal or angular collision mode
comparisons requires activation; and activating said device.
2. A method as recited in claim 1 in which said device is an
inflatable air bag and said air bag is inflated by said activating
step.
3. A method as recited in claim 1 in which said device is an air
bag adapted to be inflated to a first stage of inflation and
further to a second stage of further inflation, and said air bag is
inflated only to said first stage following the steps of claim
1.
4. A method as recited in claim 3 comprising comparing selected of
said velocity and displacement values with predetermined
corresponding second stage threshold velocity and displacement
values as a basis for determining whether either said frontal or an
angular mode collision situation requires further safety device
activation and, if any one of collision mode comparisons requires
further activation, and activating said device to its second stage
of activation.
5. A method as recited in claim 1 in which only said velocity
values are used in determining whether said frontal mode collision
situation requires safety device activation and each said angular
mode uses a combination of said velocity values and said
displacement values as a basis for determining whether to activate
said device.
6. A method as recited in claim 2 in which only said velocity
values are used in determining whether said frontal mode collision
situation requires safety device activation and each said angular
mode uses a combination of said velocity values and said
displacement values as a basis for determining whether to activate
said device.
7. A method as recited in claim 3 in which only said velocity
values are used in determining whether said frontal mode collision
situation requires safety device activation and each said angular
mode uses a combination of said velocity values and said
displacement values as a basis for determining whether to activate
said device.
8. A method as recited in claim 4 in which only said velocity
values are used in determining whether said frontal mode collision
situation requires second stage safety device activation and each
said angular mode uses a combination of said velocity values and
said displacement values as a basis for determining whether to
activate said device.
9. A method as recited in claim 1 in which said device has been
activated to a first stage of activation by a frontal mode
collision situation, said method then further comprising the steps
of: comparing a current sequence of said velocity values with
second stage threshold velocity values for said right side, left
side and passenger compartment locations; and activating said
device to a second stage of activation providing said velocity
value at said passenger compartment exceeds its second stage
threshold velocity and at least one of said right side or left side
location velocity values exceeds its respective second stage
threshold velocity.
10. A method as recited in claim 2 in which said device has been
activated to a first stage of activation by a frontal mode
collision situation, said method then further comprising the steps
of: comparing a current sequence of said velocity values with
second stage threshold velocity values for said right side, left
side and passenger compartment locations; and activating said
device to a second stage of activation providing said velocity
value at said passenger compartment exceeds its second stage
threshold velocity and at least one of said right side or left side
location velocity values exceeds its respective second stage
threshold velocity.
11. A method as recited in claim 3 in which said device has been
activated to a first stage of activation by a frontal mode
collision situation, said method then further comprising the steps
of: comparing a current sequence of said velocity values with
second stage threshold velocity values for said right side, left
side and passenger compartment locations; and activating said
device to a second stage of activation providing said velocity
value at said passenger compartment exceeds its second stage
threshold velocity and at least one of said right side or left side
location velocity values exceeds its respective second stage
threshold velocity.
12. A method as recited in claim 1 in which said displacement
values for said left side and right side sensor locations are
compared with first stage threshold displacement values for said
locations and a velocity value for said passenger compartment
sensor location is compared with a first stage threshold velocity
for said location in an angle mode collision situation, and
activating said device to a first stage of activation providing at
least one of said displacement values exceeds its respective first
stage threshold value and said velocity value exceeds its threshold
first stage velocity value.
13. A method as recited in claim 2 in which said displacement
values for said left side and right side sensor locations are
compared with first stage threshold displacement values for said
locations and a velocity value for said passenger compartment
sensor location is compared with a first stage threshold velocity
for said location in an angle mode collision situation, and
activating said device to a first stage of activation providing at
least one of said displacement values exceeds its respective first
stage threshold value and said velocity value exceeds its threshold
first stage velocity value.
14. A method as recited in claim 3 in which said displacement
values for said left side and right side sensor locations are
compared with first stage threshold displacement values for said
locations and a velocity value for said passenger compartment
sensor location is compared with a first stage threshold velocity
for said location in an angle mode collision situation, and
activating said device to a first stage of activation providing at
least one of said displacement values exceeds its respective first
stage threshold value and said velocity value exceeds its threshold
first stage velocity value.
15. A method as recited in claim 12 in which said device has been
activated to a first stage of activation by an angle mode collision
situation, said method then further comprising the steps of:
comparing said velocity values with second stage threshold velocity
values for said right side and left side sensor locations;
comparing said displacement value for said passenger compartment
sensor location with a second stage threshold displacement value
for said location; and activating said device to a second stage of
activation providing said right side velocity value and said
displacement value exceed their corresponding second stage
threshold values or said left side velocity exceeds its
corresponding second stage threshold value.
16. A method as recited in claim 13 in which said device has been
activated to a first stage of activation by an angle mode collision
situation, said method then further comprising the steps of:
comparing said velocity values with second stage threshold velocity
values for said right side and left side sensor locations;
comparing said displacement value for said passenger compartment
sensor location with a second stage threshold displacement value
for said location; and activating said device to a second stage of
activation providing said right side velocity value and said
displacement value exceed their corresponding second stage
threshold values or said left side velocity exceeds its
corresponding second stage threshold value.
17. A method as recited in claim 14 in which said device has been
activated to a first stage of activation by an angle mode collision
situation, said method then further comprising the steps of:
comparing said velocity values with second stage threshold velocity
values for said right side and left side sensor locations;
comparing said displacement value for said passenger compartment
sensor location with a second stage threshold displacement value
for said location; and activating said device to a second stage of
activation providing said right side velocity value and said
displacement value exceed their corresponding second stage
threshold values or said left side velocity exceeds its
corresponding second stage threshold value.
18. A method as recited in claim 1 in which said displacement value
for said passenger compartment location and said velocity values
for said right side and left side sensor locations are compared
with corresponding first stage threshold displacement and velocity
values in an offset deformable barrier collision mode, and
activating said device to a first stage providing said passenger
compartment displacement value exceeds its first stage threshold
displacement value and at least one of said right side or left side
velocities exceed their corresponding first stage threshold
velocities.
19. A method as recited in claim 2 in which said displacement value
for said passenger compartment location and said velocity values
for said right side and left side sensor locations are compared
with corresponding first stage threshold displacement and velocity
values in an offset deformable barrier collision mode, and
activating said device to a first stage providing said passenger
compartment displacement value exceeds its first stage threshold
displacement value and at least one of said right side or left side
velocities exceed their corresponding first stage threshold
velocities.
20. A method as recited in claim 3 in which said displacement value
for said passenger compartment location and said velocity values
for said right side and left side sensor locations are compared
with corresponding first stage threshold displacement and velocity
values in an offset deformable barrier collision mode, and
activating said device to a first stage providing said passenger
compartment displacement value exceeds its first stage threshold
displacement value and at least one of said right side or left side
velocities exceed their corresponding first stage threshold
velocities.
21. A method as recited in claim 18 in which said device has been
activated to a first stage of activation by an offset deformable
barrier mode collision situation, said method then further
comprising the steps of: comparing said right side and left side
sensor location displacement values with second stage threshold
displacement values for said locations; comparing said passenger
compartment sensor location velocity value with a second stage
threshold velocity value for said location; and activating said
device to a second stage of activation providing said velocity
value exceeds its threshold value and at least one of said
displacement values exceeds its threshold value.
22. A method as recited in claim 19 in which said device has been
activated to a first stage of activation by an offset deformable
barrier mode collision situation, said method then further
comprising the steps of: comparing said right side and left side
sensor location displacement values with second stage threshold
displacement values for said locations; comparing said passenger
compartment sensor location velocity value with a second stage
threshold velocity value for said location; and activating said
device to a second stage of activation providing said velocity
value exceeds its threshold value and at least one of said
displacement values exceeds its threshold value.
23. A method as recited in claim 20 in which said device has been
activated to a first stage of activation by an offset deformable
barrier mode collision situation, said method then further
comprising the steps of: comparing said right side and left side
sensor location displacement values with second stage threshold
displacement values for said locations; comparing said passenger
compartment sensor location velocity value with a second stage
threshold velocity value for said location; and activating said
device to a second stage of activation providing said velocity
value exceeds its threshold value and at least one of said
displacement values exceeds its threshold value.
Description
TECHNICAL FIELD
[0001] This invention pertains to computer based methods for
determining whether a frontal or angular collision situation in a
vehicle may require activation of a safety device. More
specifically, this invention pertains to the placement of
acceleration sensors in a vehicle and the continuous selective use
of their integrated velocity and displacement signals in frontal
and angular collision situations to help to determine whether a
safety device, such as a passenger compartment air bag, is to be
activated and, if so, how it is to be activated.
BACKGROUND OF THE INVENTION
[0002] Safety devices for the protection of the operator and
passengers of automotive vehicles have been in use for many years.
Many safety features function in a collision situation without
external activation. Seat reinforcement, seat headrests, and
passenger compartment padding are examples of such safety items.
Other safety devices such as supplemental inflatable restraints,
popularly known as air bags, require external activation when a
collision event is apparently occurring.
[0003] Air bags comprise an inflatable bag, an electrically
actuated igniter and a gas generator. Each bag is folded and stored
with its igniter and gas generator in vehicle locations, such as,
the steering wheel pad, instrument panel, door panel or body
pillar. Air bags also require a collision detection system that
determines when the bags should be deployed and signals the
ignition of one or more charges (or stages) of the gas generator.
Some passive passenger protection systems, rely on acceleration
sensors (detecting abrupt vehicle deceleration) and a
micro-processor based controller. An acceleration sensor is a
device that continually senses accelerative forces and converts
them to electrical signals. The controller continually receives
acceleration signals from each sensor and processes them to
determine whether a collision situation is occurring that requires
air bag deployment.
[0004] The content of such a collision detection system for safety
device actuation usually depends upon the method or algorithm used
by the controller for assessing collision severity. Most systems
rely on an acceleration sensor placed in the passenger compartment,
close to the center of gravity of the vehicle. This sensor is often
put under the passenger seat as part of a sensing and diagnostic
module (SDM) of the vehicle collision sensing system. In addition,
some systems place one or more accelerometers at the center or
sides of the radiator cross-tie-bar (called electrical frontal
sensors, EFS) to detect vehicle front-end deceleration indicative
of a collision. The collision detection controller receives signals
from the acceleration sensor(s) and evaluates them in a
pre-programmed manner to determine whether air bag deployment is
necessary. The program may also determine the degree of deployment,
e.g., one or two inflation stages, of the bag.
[0005] The algorithms of collision sensing controllers have
involved differing degrees of complexity. For example, acceleration
values from a single sensor (e.g., the SDM sensor) have been
compared with a pre-determined threshold acceleration value as a
test for device deployment. Values from more than one sensor
location have been used in the collision sensing practices.
Acceleration values have been integrated over time to yield crush
velocities, and further integrated to yield crush displacement
values. Further, the derivative of acceleration values have been
determined as "jerk" values. Such velocity and displacement values,
and jerk values, have also been compared with respective
pre-determined threshold values as a more selective basis for
achieving timely air bag deployment. Also, acceleration data has
been used in combination with seat occupancy information and seat
belt usage to determine air bag deployment.
[0006] There are variants in vehicle front-end collision modes and,
of course, there can be considerable variation in the severity of a
collision depending upon the relative structure and mass of the
vehicle and its collision object as well as the relative velocities
at the onset of a collision. With respect to front-end collision
modes, a vehicle may collision head-on with another vehicle or
fixed object in a frontal collision mode. Front-end collisions of a
vehicle with other vehicles often occur in an angular mode between
head-on (zero degree) and a side-ways collision (ninety degrees). A
further distinction is often made between an angular collision with
a rigid or non-yielding object and an offset deformable barrier
(ODB mode). Exemplary vehicular collision testing reveals different
patterns of front end and passenger compartment crush velocities
and displacements associated with different collision modes. In
fact, considerable collision testing of a vehicle has been required
to provide the substantial database of threshold values of jerk,
acceleration, velocity and/or displacement over a collision period
for use by a collision sensing controller. Such data must be
compiled from suitably instrumented test vehicles over the relevant
duration of each test collision period. Depending upon the nature
and severity of a collision, an airbag deployment decision may be
made by the controller process at any time during a period of from
about 15 milliseconds (ms) to 70 ms or so from the onset of the
collision.
[0007] It would be desirable to further calibrate the control
systems for airbags and other such devices. It is common practice
in calibrating such control systems to develop the required
calibration data from measurements taken in exemplary collision
testing of each new vehicle model so that the control system
calibration for that model is established according to its
collision characteristics. It would be desirable to provide a
calibration method which does not require actual testing of
vehicles or reduces the need for testing of vehicles. In the prior
art, attempts have been made to discriminate the severity of the
collision event using acceleration and jerk signals which are
difficult to generate from computer simulations, such as finite
element analysis. It would be desirable to obtain a collision
sensing system algorithm that relies upon velocity based measures
which can be obtained without collision testing prototype vehicles
to calibrate the collision sensing system. Preferably, the velocity
based measures are obtained by use of computer or finite element
models for calibration of collision sensing systems.
[0008] Accordingly, it is an object of this invention to provide an
alternative method of activating an air bag or other
collision-responsive safety device that can utilize only velocity
and displacement values obtained from a suitable collision model.
It is a further object of this invention to provide an airbag
activation method that utilizes a consideration of more than one
vehicle collision mode in use of time integrated acceleration
sensor data.
SUMMARY OF THE INVENTION
[0009] This invention provides a vehicle collision sensing system
which helps to determine when to actuate a safety device. This is
accomplished by use of vehicle mounted accelerometers and an
associated signal processing algorithm in a microprocessor. The
collision sensing algorithm is composed of parallel assessment
branches or modules for detecting different collision modes, each
of which uses only current velocity and displacement measures
calculated by integrating the acceleration data recorded from
vehicle mounted accelerometers.
[0010] In accordance with the invention at least two front end
acceleration sensors are employed together with at least one sensor
in the passenger compartment. For example, two frontal acceleration
sensors (EFS), may be mounted at the left and right sides of the
radiator cross-tie-bar in the engine compartment of the vehicle for
sensing the acceleration of the tie-bar. The vehicle is also
provided with an accelerometer in the passenger compartment, such
as a location underneath the passenger seat as a part of a sensing
and diagnostic module (SDM) of the vehicle collision sensing
system. The vehicle collision sensing system detects and
discriminates the severity of the collision incidents by signals
derived from the front end (EFS) acceleration sensors and the SDM
acceleration sensor. Such derived signals are used in the signal
processing algorithm of this invention which is implemented in the
control program within the microcomputer of the collision sensing
system.
[0011] In a preferred embodiment of the invention, the control
method uses sensor data in a manner to determine air bag inflation
needs in each of a frontal collision mode, an angular collision
mode and an ODB collision mode. A different combination of
representative collision modes could be used but these three are
exemplified. In general, the collisions are classified into
different modes based on similar signal patterns. The name one
chooses for the modes is indicative of the main type of collisions
that fall into that classification, e.g. frontal mode characterizes
the events with patterns similar to the full frontal barrier
events, angle mode characterizes the events with patterns similar
to the angle barrier events, etc. Other type of collisions may have
similar patterns with the ones in the modes already chosen, e.g.
pole events may behave relatively similar to the ODBs or offset
rigid barrier events may behave similar to the full frontal events,
and accordingly are classified into those modes.
[0012] When activated by a representative acceleration value
indicative of a possible collision, the subject method proceeds by
integrating acceleration data from each of three sensors to obtain
corresponding velocity and displacement values for each sensor
location. Thus, the acceleration data recorded at both radiator tie
bar sensors (Al and Ar) and SDM (As) are used to calculate Vs, Vlm,
Vrm, Ss, Sl, and Sr. Here Vs and Ss denote the velocity and
displacement, at SDM, respectively; and Vlm, Vrm, Sl, and Sr denote
the maximum velocity and displacement at the left and right
front-end accelerometer locations, respectively. These values are
selectively used in a series of three parallel collision mode
calculations and logical tests, namely a frontal mode module, angle
mode module, and ODB (offset deformable barrier) mode module.
Preferably, each collision mode module has two sub-modules, i.e.
the 1.sup.st and 2.sup.nd stage airbag deployment modules.
[0013] Suitably, the sensing algorithm uses the acceleration
signals, As, from the SDM accelerometer to enable (or initiate)
operation of the collision sensing method of this invention. The
control method determines whether the acceleration, As, at the
passenger compartment location is equal to or greater than a
predetermined acceleration threshold which, for example, may be set
at 2 g's (g being the acceration due to gravity). If As is not
greater than the enable threshold, the program loops back to
monitoring the input. This controller cycle is repeated every
millisecond or so. If As is equal to or greater than the threshold,
the program advances to the next step, i.e. to initiate the system
clock and to calculate the several velocity and displacement
measures. The sensing system is reset for minor incidents by a
reset module which determines whether the velocity measure, Vs, is
equal to or greater than a predetermined threshold. If Vs is not
equal to or greater than the reset threshold, the program loops
back to monitoring the input. If Vs is greater than the threshold,
the program advances to the next step.
[0014] Once the collision severity determining method is enabled
the velocities and displacements are calculated and entered into
the three branching program modules; the frontal mode module, angle
mode module and ODB mode module. The module for which the 1.sup.st
stage thresholds are first exceeded initiates the deployment of the
airbag. Then its corresponding 2.sup.nd stage sub-module determines
the severity of the collision by comparing the measures with
another set of thresholds. The other modes are ignored after a
first stage deployment decision has been made.
[0015] In the frontal mode-first stage assessment, velocity values
are used. It has been observed that the velocity measures, Vs, Vlm
and Vrm are generally higher for severe frontal full-barrier-like
impact events. Accordingly, they are used in the method of this
invention to determine whether or not to trigger the deployment of
the first stage airbag inflator for this type of impact events. If,
and only if, all three velocity measures for an event are equal to
or greater than a set of velocity thresholds, pre-determined by
experiment or calculation for the vehicle, the program will send a
triggering signal out to ignite the first stage air bag
inflation.
[0016] If first stage air bag inflation has been commanded through
the frontal mode program module, the frontal mode--2nd stage
determination is made. Again, the velocity measures, Vs, Vlm and
Vrm are used here to determine whether or not to trigger the
deployment of the second stage airbag inflator for this type of
frontal full-barrier-like impact events. However, unlike the first
stage, an "or" logic is used to allow a second stage deployment
when either one of Vs or "Vlm and Vrm" meets the threshold
condition.
[0017] In parallel with its analysis of the frontal mode-first
stage the controller is also analyzing the angle (or angles)
collision mode--1st stage and the ODB collision mode-first stage.
As stated, results from any collision mode analysis can trigger
first stage air bag inflation.
[0018] In the case of the angle collision mode-first stage, it has
been found that either the passenger compartment velocity measure,
Vs, or the front end displacement measures, Sl and Sr (depending
upon which side of the vehicle is impacted) are generally high for
severe angle-like impact events. Accordingly, it is preferred to
use them in the angle mode to determine whether or not to trigger
the deployment of the first stage airbag inflator for this type of
impact events. In assessing the second stage of the angle mode a
suitably high left front end velocity measure, Vlm, can trigger the
second stage airbag inflator. In the alternative, a suitably high
velocity value at the right front end sensor, Vrm, in combination
with a suitably high SDM displacement, Ss, can trigger second stage
deployment for right angle-like collision events.
[0019] In the ODB mode-first stage a combination of displacement at
the SDM and velocity at the affected side are used in assessing the
severity of an ODB collision mode type event. Thus, a combination
of Ss and Vlm are used to determine whether to trigger deployment
of the first stage inflator for a left side and a combination of Ss
and Vrm for a right side event. For an ODB-second stage
determination Vs and Sl are used for discriminating left side
events and Vs and Sr for right side events.
[0020] Thus, this invention provides a collision severity
determination method that identifies distinct front end vehicle
collision modes and associates with these modes crush velocity and
displacement data from selected vehicle body acceleration sensor
locations. The collision detection controller continually compares
acceleration data with a predetermined threshold value indicative
of a collision possibility. The controller then determines current
values of crush velocity and displacement at sensor locations at
the front of the vehicle body and in the passenger compartment.
Suitable selections are made from these values to assess, in
parallel, each of at least three collision modes to determine
activation of an air bag or other safety device. This practice is
readily adaptable to managing two or more levels of device
activation.
[0021] A critical feature of a collision severity determination
method is the availability of suitable threshold velocity and
displacement values over a period of up to 100 ms for each
acceleration sensor and device activation. These threshold values
may be based on physical collision test data for the specific
vehicle, or collision model data, or a combination of test data and
modeling.
[0022] Other objects and advantages of the invention will become
apparent from a detailed description of illustrated embodiments
which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a process flow diagram for an air bag activation
controller receiving continuous acceleration signals and, following
the enabling process of FIG. 2, calculating current values of
velocity and displacement for the acceleration sensor sites. The
velocity and displacement values are applied in three parallel
collision mode modules; a frontal mode, an angular mode and an
offset deformable barrier mode; and the results, which may include
two stages of deployment, are used in determining whether air bag
activation is required.
[0024] FIG. 2 is a process flow diagram for an air bag activation
controller process for assessing acceleration data and determining
whether the process of FIG. 1 is to be initiated. Upon such
initiation, the process then calculates velocity and displacement
values for the FIG. 1 process.
[0025] FIG. 3 is a process flow diagram for assessing first stage
airbag deployment under the frontal vehicle collision mode.
[0026] FIG. 4 is a process flow diagram for assessing second stage
airbag deployment under the frontal collision mode.
[0027] FIG. 5 is a process flow diagram for assessing first stage
airbag deployment under the angles (or angle) vehicle collision
mode.
[0028] FIG. 6 is a process flow diagram for assessing second stage
airbag deployment under the angles vehicle collision mode.
[0029] FIG. 7 is a process flow diagram for assessing first stage
airbag deployment under the ODB vehicle collision mode.
[0030] FIG. 8 is a process flow diagram for assessing second stage
airbag deployment under the ODB vehicle collision mode.
[0031] FIGS. 9A-9F are graphs presenting illustrative threshold
values of time based velocity data in miles per hour, mph, for
frontal mode, first stage and second stage inflation, collision
analyses. The data is presented for SDM, EFS left side and EFS
right side sensor locations. The graphs also include velocity data
at the sensor locations obtained from representative frontal mode
collision events of a vehicle.
[0032] FIGS. 10A-10D are graphs presenting illustrative threshold
values of time based velocity data, mph, and displacement data in
centimeters, cm, for angle mode, first stage inflation, collision
analyses. The data is presented for SDM, EFS left side and EFS
right side sensor locations. The graphs also include velocity and
displacement data at sensor locations obtained from representative,
left side impact and right side impact, angle mode collision events
of a vehicle.
[0033] FIGS. 11A-11C are graphs presenting illustrative threshold
values of time based velocity data, mph, and displacement data, cm,
for angle mode, second stage inflation, collision analyses. The
data is presented for SDM, EFS left side and EFS right side sensor
locations. The graphs also include velocity and displacement data
obtained from representative, left side impact and right side
impact, angle mode collision events of a vehicle.
[0034] FIGS. 12A-12D are graphs presenting illustrative threshold
values of time based velocity data, mph, and displacement data, cm,
for OBD mode, first stage and second stage inflation, collision
analyses. The data is presented for SDM and EFS left side sensor
locations. The graphs also include velocity and displacement data
obtained from representative left side impact, OBD mode collision
events of a vehicle.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0035] This illustrative embodiment of the collision detection
algorithm of this invention uses three acceleration sensors. One
sensor is located at each end of the radiator tie bar at the front
of the vehicle engine compartment. They are sometimes referred to
as EFS left side and EFS right side in this specification. The
radiator tie bar is close to the front of the vehicle and it
extends cross-wise so that the left and right sensors can
experience different accelerations in impacts arising at an angle
to the forward direction of travel. A third accelerometer is
located under a front passenger seat in the passenger compartment
of the vehicle. This location is a common location for an
accelerometer that transmits data to the airbag inflation
controller. This acceleration sensor location is sometimes also
used for other vehicle or chassis control and/or diagnostic
purposes, as in the sensing and diagnostic module (SDM). The
acceleration sensors are electrically powered and continually
supply their signals to the collision detection controller during
vehicle operation. The controller includes a microprocessor that
continually receives and analyzes acceleration data from the three
sensors to determine whether a collision situation exists requiring
deployment of an airbag. This invention provides a reliable and
discerning process for such a determination.
[0036] In this embodiment of the invention three front end
collision modes of the vehicle are utilized. One collision mode is
a frontal mode representing a head-on collision of the vehicle with
another vehicle or a fixed object such as a concrete wall. The
second collision mode is an angular mode in which the object that
is struck is fairly rigid but is struck at an offset angle between
a head-on collision and a side impact. The third mode includes
collisions that produce crush velocity and displacement data at the
sensor locations representative of what is known in the collision
analysis art as a collision with an offset deformable barrier. This
type of collision typically has the characteristic of being
initially somewhat milder early in the event and more severe later
in the event.
[0037] FIG. 1 is a process flow diagram of a preferred three
collision mode algorithm executed by a collision detection
microprocessor in accordance with this invention. However, since
vehicles normally operate without collisioning, accelerometer data
is continually being generated without a need for execution of a
collision mode analysis. Accordingly, the sub-process of FIG. 2, an
enabling process for collision severity detection, is first
employed. Thus, the processing box 10 in FIG. 1 continually
receives acceleration data from the respective sensors as As, from
the under seat SDM sensor, Al from the sensor at the left end of
the radiator tie bar and Ar from the sensor at the right end of the
radiator tie bar. The continuous signals are filtered and
analog-digital converted in a known manner to provide discrete
signals at one millisecond processing intervals. The function of
processing block 10 is summarized in FIG. 2.
[0038] Referring to FIG. 2, the respective acceleration values
enter boxes 12, 14 and 16. The function in these boxes includes
analog signal to digital signal conversion (A/DC). Signal As is
filtered and digitized in box 12. Al is filtered and digitized in
box 14 and Ar is filtered and digitized in box 16. These signals
are sampled every millisecond. The As signal (originating from the
under seat location) is then sent to box 18 where its value of
acceleration is compared with a predetermined collision
acceleration threshold value. Such a value may be, for example, 2
g, or two times the magnitude of the acceleration due to gravity.
If, and as usually will be the case, the As value does not exceed 2
g, the enable signal in box 18 remains "off" and the collision
analysis does not proceed on this cycle. However, the current As,
Al and Ar values are sent to accumulation boxes 22, 24 and 28,
respectively. The function of accumulation boxes 22, 24, and 28 is
to each retain ten or so acceleration values (As, Al and Ar,
respectively) for integration as initial velocity values, Vo, in
the event the collision analysis is enabled. Thus each new
acceleration value displaces the oldest value from these
accumulator storage boxes 22, 24, 28 so that a current value of the
appropriate Vo is available in each box.
[0039] As stated, the basis of this enabling process is the under
seat accelerometer signal. It is closest to the center of gravity
of the vehicle and may be less sensitive to acceleration values
obtained on bumpy roads and the like. However, other sensor
locations could be selected for this enabling test function with a
suitable threshold acceleration value.
[0040] Thus, generally, the collision severity analysis of the FIG.
1 process is not executed. However, upon an As value being received
in block 18 that exceeds 2 g, or other suitable threshold value, an
enable signal is issued by box 18. The enable signal is forwarded
to modules 20, 26 and 30, as well as to accumulation boxes 22, 24
and 28. Enabled modules 20, 26, and 30 now allow the current and
future values of As, Al and Ar to flow to velocity calculation
boxes 32, 34 and 36, respectively. Accumulation boxes 22, 24 and 28
have been calculating current velocities, Vo, by adding
(integrating) the last ten acceleration values from the respective
sensors. The appropriate accumulation boxes are now sampled to
provide their respective Vo values to the three velocity
calculation boxes 32, 34 and 36.
[0041] Velocity calculation boxes 32, 34 and 36 use their initial
Vo values plus incoming acceleration values As, Al and Ar to
determine Vs, Vl and Vr respectively by integration. In velocity
box 32 the current value of the SDM sensor velocity Vs is thus
determined and output as signal (2).
[0042] A current time signal, to, counting from the enable event,
is output from enable box 18 as signal (1).
[0043] Time signals and Vs values are continually supplied to reset
box 44. Incoming Vs values are compared with immediate
predecessors. If the incoming value fails to exceed a predetermined
threshold, e.g., 0.5 mph, within a specified time window, for
example 10 ms, and its rate of increase is less than that
corresponding to an acceleration of about 1 g thereon, a reset
command is issued. Such a reset signal is sent to all relevant
process boxes in FIG. 2 as indicated by the RS indicia in the boxes
and the process is restarted with the next cycle. In other words,
the initial As value that enabled the process is attributed to a
non-collision related event.
[0044] A current velocity for the left front sensor location, Vl,
is output from box 34 and sent to a maximum velocity value box 46.
The current maximum value of Vl leaves box 46 as, Vlm, signal (6).
Similarly, a current velocity for the right front sensor location,
Vr, is output from box 36 and sent to a maximum velocity value box
48. The current maximum value of Vr leaves box 48 as, Vrm, signal
(7). The current maximum velocity values in boxes 46 and 48 are
also reset by a command from reset box 44.
[0045] The velocity calculation values Vs, Vlm and Vrm are also
forwarded to their respective displacement calculation boxes 38, 40
and 42. The underseat accelerometer displacement, Ss, is calculated
by integration of current and immediate past velocity values in
displacement calculation box 38 and output as, Ss, signal (3).
Similarly, the left front sensor displacement, Sl, is calculated in
displacement calculation box 40 and output as, Sl, signal (4). And
right front sensor displacement, Sr, is produced from displacement
calculation box 42 and output as, Sr, signal (5). It is noted that
front sensor displacements are calculated from the maximum velocity
values. These signals correspond with the signals at the right side
of the processing box 10 in FIG. 1.
[0046] Accordingly, the function of the sub-processing that is
carried out in FIG. 2 is to determine whether a collision situation
requiring air bag deployment may exist. This is determined by
continually comparing As values with a predetermined threshold
acceleration value. If the threshold value is exceeded, an enabling
signal is issued causing the microprocessor to start the process of
calculating the respective current values of velocity and
displacement for each of the three sensor locations. The enabling
signal is represented by fl in boxes 50, 52, 54 56, 58 and 60. The
respective process does not proceed in a box until it has been
enabled by a previous determination.
[0047] Referring again to FIG. 1, it is shown that the outputs of
the processing box 10, the summation of the processing in FIG. 2,
comprises seven current values: to, Vs, Ss, Vlm, Sl, Vrm and Sr.
Over the next several millisecond intervals the controller will
continue to update these values as the potential collision
situation develops. As they are determined the signals are used in
the three collision mode analyses of this process. The appropriate
time, velocity and displacement values are used for the first stage
determinations of the frontal, angles and ODB modes. These
calculations are illustrated and indicated in boxes 50, 52 and 54
respectively. These determinations are conducted generally in
parallel (to the extent permitted by controller operation) and the
specific analyses for the respective stage 1 boxes will now be
described in more detail.
[0048] FIG. 3 illustrates the analyses of the first stage of the
frontal mode, the detailed logic of the process indicated in box 50
of FIG. 1. The first stage of the frontal collision mode is
characterized by high values of Vs, Vrm and Vlm. These velocity
values together with the current time count are each forwarded to
respective comparison boxes 300, 302 and 304. In comparison box
300, the value of Vs is compared with a pre-determined threshold
velocity and, depending upon whether Vs is greater than the
threshold velocity, an output of 1 for yes or 0 for no is forwarded
to AND box 310. Similarly, the current value of Vlm is forwarded to
comparison box 302 where a similar comparison is made with a
suitable threshold velocity for the left end of the tie bar and a 0
for no or 1 for yes is forwarded to AND box 310. Likewise, the
current value of Vrm is compared in box 304 with a predetermined
threshold velocity value for the right end of the tie bar and a 1
or 0 is forwarded to AND box 310.
[0049] The threshold values are determined either by collision
testing or by computer modeling to provide values that are
reflective of a full frontal barrier collision under varying
vehicle velocities. For example, with respect to a particular
vehicle, suitable values of velocity thresholds are determined
based on the velocity values at the required deployment time
calculated from the beginning of a collision enabling event for a
period up to 100 ms or so. FIGS. 9A through 9C are graphs of
threshold values from zero to seventy-five milliseconds of SDM
velocity 900, EFS left side velocity 902 and EFS right side
velocity 904, respectively. The threshold velocity at the underseat
location (FIG. 9A, curve 900) for the frontal collision mode is
about one mile per hour at the required sensing time of six
milliseconds from the onset of the collision enabling signal, for a
severe collision event, and about five miles per hour at the
required sensing time of 12 ms for a less severe event. Thereafter,
the threshold values increase as per curve 900. Values selected
from curve 900 are used in comparison box 300 depending upon the
time, to, when the comparison is made. It will be appreciated that
all of the velocity curves are exemplary and may be different for
individual vehicles or collision situations or safety device
parameters.
[0050] The threshold velocity values (from curves 902 and 904,
respectively) for the frontal sensors, EFS left and EFS right,
which are in the crush zone of the vehicle during a frontal full
barrier collision, are set just below 15 miles per hour (for
example) regardless of the number of millisecond intervals from the
enabling signal.
[0051] Depending on the perceived severity of a collision, the
required time for a deployment decision may vary from a few
milliseconds to many milliseconds and, thus, threshold velocity and
displacement values are predetermined for up to about 100
milliseconds. In general, the threshold values continue to increase
over this period.
[0052] FIGS. 9A-9C also display exemplary full frontal mode
collision velocity data for the SDM sensor and the left and right
side EFS sensor locations. The dotted curves (912, 918 and 924) in
these figures represent the velocities experienced at the
respective sensor locations in a relatively low velocity impact--an
impact that may not require first stage air bag deployment. It is
seen that none of exemplary velocity curves 912, 918 or 924 exceeds
the corresponding threshold velocity curve, 900, 902 or 904. The
dashed line curves 914, 920 and 926 represent a higher velocity
frontal impact--one that may require first stage airbag deployment.
And each of curves 914, 920 and 926 exceeds the corresponding
threshold velocity curve, 900, 902 or 904 within about ten
milliseconds after the onset of the collision. Finally, the
dot-dash curves, 916, 922 and 928, are the velocities experienced
at the respective sensor locations during a high-speed full frontal
impact that may require quick first stage air bag deployment. It is
seen that the velocity at each of the sensors exceeds the
corresponding threshold velocity within a few milliseconds of the
collision.
[0053] Box 310 (FIG. 3) is an AND box which means that this first
stage frontal mode analysis will issue a "deploy" command only if
it receives a yes (or 1) signal from each of the velocity
comparisons. FIGS. 9A-9C illustrate exemplary collision data in
which the measured velocities at the SDM and EFS sensor locations
consistently reflect this AND modal analysis. Thus a collision mode
is characterized by a certain pattern of all the velocities and/or
displacements at all sensor locations. The output "yes or no" is
forwarded to the second stage-frontal mode comparison box 56, FIG.
1, and to the stage 1 deployment box 62. If the output from box 50
is yes, and it is the first collision mode comparison box to issue
a "yes" command, such signal will prompt a "deploy" command from
stage 1 deployment box 62 and air bag inflation will be initiated.
A timely "yes" output from box 50 will also initiate a second stage
frontal mode evaluation to be started in box 56. Also, box 62 will
issue a command stopping further collision evaluations in first
stage angles mode and ODB modes comparison boxes 52 and 54.
[0054] Thus, first stage deployment box 62 is an OR box and the
first deployment command to reach it from any of the collision mode
comparison boxes 50, 52 or 54 will prompt first stage air bag
inflation. As soon as a first stage deployment decision is reached
in one of the three collision modes, such decision comparisons are
terminated in the other two modes. Second stage deployment
comparisons are continued only in the collision mode that first
issues a first stage deployment command.
[0055] In the event that the first cycle of first stage frontal
mode comparisons result in a "no", and the other first stage
collision mode results are "no," new velocity and displacement
values are input to boxes 50, 52 and 54. The controller continues
to cycle through these collision mode determinations until a "yes"
is produced or until enough cycles elapse and it is concluded that
the event that started this processing does not require air bag
deployment.
[0056] The first stage-frontal mode analysis has been completed
above. The angle mode and ODB mode first stage analyses will now be
described.
[0057] The angles mode, first stage, analysis is illustrated in
FIG. 5. It is a detailed description of the analysis executed in
box 52 of FIG. 1. Angle(s) impact modes, first stage, are
characterized by relatively large displacement values at either the
right or left tie bar sensors and large velocity value at the
underseat SDM sensor. Accordingly, these values together with the
time count are used in the FIG. 5 angle mode, first stage
comparison. Current values of Sl and Sr enter comparison boxes 500
and 502 respectively. Vs signals enter comparison box 504. Values
of event time count to are used in each box.
[0058] FIGS. 10A-10D are graphs showing first stage threshold
values for SDM velocity in mph and EFS left and right displacements
in centimeters. Curve 1000 in FIGS. 10A and 10B presents SDM
threshold velocity values over the first 75 milliseconds of an
angle mode collision for an illustrative vehicle. Curves 1002 (FIG.
10C) and 1004 (FIG. 10D) present EFS left and EFS right threshold
displacement values.
[0059] The respective Sl, Sr and Vs comparisons with suitable
threshold values are made in comparison boxes 500, 502 and 504. If
either the Sl or Sr comparisons yields a "1" (yes), then 1 is
output from OR box 506 to AND box 508. The output from Vs
comparison box 504 is forwarded to AND box 508. AND box 508 must
receive "1" s from both comparison box 504 and OR box 506 to issue
a "1" to angle mode, first stage output, angle (1). The angle (1)
signal from box 52 is forwarded as input 2 to OR box 62, FIG. 1,
which is the first stage deployment decision box.
[0060] FIGS. 10A and 10C also present exemplary SDM velocity data
and EFS left displacement data for two left side, angle mode
impacts of increasing severity and a non-deploy full frontal
barrier event. In a left side angle impact the right side EFS
displacement is low and does not affect the analysis of FIG. 5.
Dotted line 1006 is a graph of SDM velocity data for the relatively
mild full frontal barrier impact and dotted line 1008 is the
corresponding displacement data for EFS left. This collision event
will not result in airbag deployment because only curve 1006
exceeds its threshold curve 1000. Curve 1008 does not exceed
threshold curve 1002.
[0061] Dashed line curves 1010 and 1012 represent SDM velocity and
EFS left displacement curves, respectively, for a more severe left
side angle impact. Both curves, 1010 and 1012, exceed their
corresponding threshold curves 1000 and 1002 and first stage air
bag deployment would be initiated by the analysis of FIG. 5.
Dot-dash curves 1014 and 1016 represent SDM velocity and EFS left
side displacement curves, respectively, for a still more severe
left side angle impact. Both curves, 1014 and 1016 exceed their
corresponding threshold curves 1000 and 1002 and first stage air
bag deployment would be initiated by the analysis of FIG. 5.
[0062] FIGS. 10B and 10D present exemplary SDM velocity data and
EFS right side displacement data for two right side angle impacts
of different severity and a non-deploy full frontal barrier event.
Although not all data is identical, the analysis parallels the
above discussion of the left side angle impacts. Dotted line curves
1018 (SDM velocity) and 1020 (EFS right side displacement) again
represent the relatively mild full frontal collision not requiring
airbag deployment. Dashed line curves 1022 (SDM velocity) and 1024
(EFS right side displacement) represent a more severe collision
initiating first stage deployment. Dot-dash curves 1026 (SDM
velocity) and 1028 (EFS right side displacement) represent a still
more severe collision that the FIG. 5 analysis will conclude
requires first stage deployment.
[0063] As stated above, the first positive deployment command to
reach box 62 initiates first stage air bag deployment. Otherwise,
comparison processing continues in each of the first stage
collision mode analyses.
[0064] FIG. 7 illustrates in detail the comparison analysis
executed in box 54 of FIG. 1 for ODB mode, first stage. In ODB
mode, first stage, the displacement of the underseat sensor, Ss, is
used as well as the values of Vlm and Vrm. These values are
forwarded, respectively, to comparison boxes 700, 702, and 704. The
corresponding time, to, is forwarded to each comparison box.
[0065] Threshold values for SDM displacement (curve 1200) and EFS
left side velocity (curve 1202) are presented in FIGS. 12A and 12B.
Also presented in these figures are exemplary SDM displacement data
(curves 1208, 1210, 1212, 1214) and EFS left side velocity data
(1216, 1218, 1220, 1222) from three ODB mode, left side impacts of
varying severity and a non-deploy full frontal barrier
collision.
[0066] Referring again to FIG. 7, Ss is compared with its time
based, threshold in box 700, and the output "1" or "0" forwarded to
AND box 708. Vlm is compared with its threshold value in box 702
and the output signal forwarded to OR box 706. Vrm is similarly
subjected to comparison in box 704 and the output signal sent to OR
box 706. Any positive result from OR box 706 is sent to AND box
708. Thus the requirement of the OBD mode, first stage is that Ss
and either Vlm or Vrm exceed their respective threshold values
before AND box transmits a deploy signal to ODB (1) and to air bag
stage 1 deployment decision box, 62 in FIG. 1.
[0067] SDM displacement dotted line curves 1208 and 1210 represent
a full frontal barrier collision and an OBD left side impact,
respectively, that exceed the displacement threshold curve 1200.
However, the EFS left side velocity data for these impacts, curves
1218 and 1216, respectively, do not exceed the velocity threshold,
curve 1202. In view of the analysis strategy of FIG. 7, these
dotted line impacts will not result in first stage airbag
deployment. The ODB impact reflected by dashed line SDM
displacement curve, 1212, and dashed line EFS left side velocity
curve 1220 both exceed their corresponding threshold curves 1200
and 1202 and first stage airbag inflation will occur. Similarly,
the OBD impact reflected by dot-dashed line SDM displacement curve,
1214, and dashed line EFS left side velocity curve 1222 both exceed
their corresponding threshold curves 1200 and 1202 and, again,
first stage airbag inflation will occur.
[0068] The frontal mode, second stage deployment analysis is shown
in FIG. 4. This analysis is executed in box 56 of FIG. 1. Current
values of Vs and t.sub.0 enter comparison box 400. Larger time
dependent threshold values are used in this second stage
comparison. FIG. 9D, curve 906 is a graph of the second stage,
threshold values of velocity (in mph) with respect to time for the
SDM sensor location. The result of the comparison in box 400 goes
to OR box 408.
[0069] Vlm and Vrm values enter comparison boxes 402 and 404. Each
is compared in this example with a constant velocity threshold
value, here 25 mph. The threshold velocity values for the EFS left
and right sensor locations are shown in FIGS. 9E and 9F, straight
horizontal line curves 908 and 910, respectively. The results from
comparison boxes 402 and 404 go to AND box 406. And the output from
AND box 406 enters OR box 408. Providing Vs exceeds its threshold,
or both Vlm and Vrm exceed their threshold, a deploy signal leaves
OR box 408 to fro2 output and to the second stage deployment
decision box 64 on FIG. 1. Otherwise, frontal mode, second stage
processing continues until a positive signal is obtained or a
specified time elapses.
[0070] FIGS. 9D-9F also illustrate exemplary velocity data in mph
for the SDM sensor location and the EFS left and EFS right
locations, respectively. SDM velocity curves 914 and 916 (FIG. 9D)
reflect the same data as the corresponding curves in FIG. 9A. The
collision events illustrated by curves 914 and 916 both exceeded
the threshold curve 900 for a stage-one airbag deployment. But only
the higher speed impact event reflected in curve 916 exceeds the
curve 906 and will contribute to a second stage inflation of the
airbag. Similarly, curves 920 and 926 do not exceed threshold
curves 908 and 910. Curves 920 and 926 summarize exemplary velocity
data for the EFS left side and EFS right side sensors,
respectively, for the same collision event that would have caused a
first stage airbag deployment but not a second stage deployment.
However, velocity curves 916, 922 and 928 for SDM, EFS left and EFS
right all exceed their second stage threshold curves 906, 908 and
910 and represent an exemplary collision that results in second
stage airbag deployment.
[0071] The angle mode, second stage comparison (executed in box 58
of FIG. 1) is illustrated in FIG. 6. Ss enters comparison box 600,
Vrm enters comparison box 602 and Vlm enters comparison box 604.
Current to values enter each comparison box. The respective signals
are compared with suitably higher, time based threshold values. The
results from comparison boxes 600 and 602 enter AND box 606 and its
result enters OR box 608. The result from comparison box 604 also
enters OR box 608. Assuming both Ss and Vrm exceed their threshold
values or Vlm exceeds it threshold a positive deployment signal ang
2 will leave OR box 608 and be transmitted to the second stage
deployment decision box 64 of FIG. 1
[0072] FIGS. 11A-11C show threshold values and illustrative
collision data values for the Angle mode second stage analysis. For
the right side angle impacts exemplary second stage threshold
values for SDM displacement and EFS right velocity with respect to
time are presented as curve 1100 in FIG. 11A and curve 1104 in FIG.
11C, respectively. The dashed line curves in FIGS. 11A and 11C
illustrate collision data for SDM displacement (curve 1106) and EFS
right velocity (curve 1114). This data is from the same angle mode
collision as the dashed line curves in FIGS. 10B and 10D. This data
did not result in a FIG. 6 analysis decision to order second stage
inflation of the airbag. The dot-dashed line curves in FIG. 11A
(curve 1108) and 11C (curve 1116) illustrate collision data for SDM
displacement and EFS right velocity. This data is from the same
angle mode collision as the dot-dashed line curves in FIGS. 10B and
10D. This data did result in a FIG. 6 analysis decision to order
second stage inflation of the airbag.
[0073] For the left side angle impacts exemplary second stage
threshold values for EFS left velocity with respect to time are
presented as curve 1102 in FIG. 11B. The dashed line curve in FIG.
11B represents collision data for EFS left velocity (curve 1110)
for the same angle mode collision illustrated as the dashed line
curves in FIGS. 10A and 10C. This data did not result in a FIG. 6
analysis decision to order second stage inflation of the airbag.
The dot-dashed line curve in FIG. 11B (curve 1112) represents
collision data for EFS left velocity for the same angle mode
collision illustrated as the dot-dashed line curves in FIGS. 10A
and 10C. This data did result in a FIG. 6 analysis decision to
order second stage inflation of the airbag.
[0074] The ODB mode, second stage analysis (executed in box 60,
FIG. 1) is shown in FIG. 8. Vs enters comparison box 800, Sl enters
comparison box 802 and Sr enters comparison box 804. Values of to
enter each of the three comparison boxes. Increased time based
threshold values are used in this second stage comparison. The
output of comparison box 800 goes to AND box 808. The outputs of
comparison boxes 802 and 804 go to OR box 806 and its output to AND
box 808. Providing that either Sl or Sr exceeds its threshold and
Vs exceeds its threshold a positive signal is issued from AND box
808. Signal ODB 2 is transmitted to second stage deployment
decision box 64 in FIG. 1.
[0075] FIGS. 12C and 12D provide time based, second stage OBD mode
threshold data for SDM velocity, curve 1204 and EFS left side
displacement, curve 1206. Data from the two left side OBD mode
collision events that initiated first stage airbag inflation in the
FIG. 7 OBD mode analysis are included in FIGS. 12C and 12D. Dashed
line curve 1224, SDM velocity data, and dashed line curve 1228, EFS
left side displacement data, both fail to exceed their
corresponding threshold curves 1204 and 1204. Accordingly, second
stage airbag inflation is not ordered by a FIG. 8 analysis. In
contrast, dot-dash line curve 1226, SDM velocity data, and dashed
line curve 1230, EFS left side displacement data, both exceed their
corresponding threshold curves 1204 and 1204. Accordingly, second
stage airbag inflation is ordered by a FIG. 8 analysis.
[0076] The second stage deployment decision box 64 acts like an OR
box. It receives signals from any of the second stage comparison
boxes 56, 58 or 60. But in any collision event, box 64 receives
signals from only the single activated second stage box from among
boxes 56, 58 and 60.
[0077] It will be appreciated that all of FIGS. 9A-12D merely show
exemplary values that are used for the purposes of explaining
certain embodiments of this invention. It is not suggested that
these are the actual threshold values or deployment levels that
should be used in practice for any particular vehicle since there
are numerous factors and trade-offs that must be considered for
each vehicle situation.
[0078] The invention has been described in terms of certain
preferred embodiments. However, it is apparent that other forms
could readily be adapted by one skilled in the art. Accordingly,
the scope of the invention is not to be limited only by the
following claims.
* * * * *