U.S. patent number RE37,260 [Application Number 09/534,154] was granted by the patent office on 2001-07-03 for method for identifying the presence and orientation of an object in a vehicle.
This patent grant is currently assigned to Automotive Technologies International Inc.. Invention is credited to David S. Breed, Wilbur E. DuVall, Andrew J. Varga.
United States Patent |
RE37,260 |
Varga , et al. |
July 3, 2001 |
Method for identifying the presence and orientation of an object in
a vehicle
Abstract
A method for determining the location of an object in a
passenger compartment of a vehicle in which ultrasonic waves are
transmitted from a first transducer into the passenger compartment,
waves reflected off an object in the passenger compartment are
received by the first transducer and a first distance from the
first transducer to the object is calculated based on the time
difference between the transmitted waves and reflected waves when
received by the first transducer. Further, different ultrasonic
waves are transmitted from a second transducer into the passenger
compartment which then receives reflected waves off the object and
a second distance from the second transducer to the object is
calculated based on the time difference between the transmitted
waves and reflected waves when received by the second transducer.
The approximate location of the object in the passenger compartment
is determined based on the first distance and the second
distance.
Inventors: |
Varga; Andrew J. (Farmington
Hills, MI), Breed; David S. (Boonton Township, Morris
County, NJ), DuVall; Wilbur E. (Kimberling City, MO) |
Assignee: |
Automotive Technologies
International Inc. (Denville, NJ)
|
Family
ID: |
27359414 |
Appl.
No.: |
09/534,154 |
Filed: |
March 23, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
798029 |
Feb 6, 1997 |
|
|
|
Reissue of: |
919823 |
Aug 28, 1997 |
05943295 |
Aug 24, 1999 |
|
|
Current U.S.
Class: |
367/99; 280/735;
367/96 |
Current CPC
Class: |
G01S
15/04 (20130101); G01S 15/42 (20130101); G06K
9/00362 (20130101); B60R 21/01536 (20141001); G01S
15/88 (20130101) |
Current International
Class: |
B60R
21/01 (20060101); G01S 15/04 (20060101); G01S
15/42 (20060101); G01S 15/00 (20060101); G06K
9/00 (20060101); G01S 15/88 (20060101); G01S
015/06 (); G01S 015/88 (); B60R 021/32 () |
Field of
Search: |
;367/99,96 ;280/735 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
3-42337 |
|
Feb 1991 |
|
JP |
|
99/14083 |
|
Mar 1999 |
|
WO |
|
Other References
Gorman et al.;"Analysis of Hidden Units in Layered Network Trained
to Classify Sonar Targets";1988; Neural Networks, vol. 1, pp.
75-89.* .
Gorman et al.; "Learning Classification of Sonar Targets Using a
Massively Parallel Network"; Jul. 1988, IEEE Transactions on
Acoustics, Speech and Signal Processing, vol. 36, pp. 1135-1140.*
.
Breed; "How Airbags Work"; Oct. 1992; Presented at the Canadian
Association of Road Safety Professionals.* .
Integrated CAE Modeling of Intelligent Restraint Systems, M. Murad
et al., SAE Technical Paper Series No. 2000-01-0606, Mar. 6-9,
2000..
|
Primary Examiner: Pihulic; Daniel T.
Attorney, Agent or Firm: Roffe; Brian
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent
application Ser. No. 08/798,029 filed Feb. 6, 1997 now
abandoned.Iadd., which claims priority under 35 U.S.C. .sctn.119(e)
of U.S. provisional patent application Ser. No. 60/011,351 filed
Feb. 8, 1996. This application also claims priority under 35 U.S.C.
.sctn.119(e) of U.S. provisional patent application Ser. No.
60/011,351 filed Feb. 8, 1996 through the parent
application.Iaddend..
Claims
We claim:
1. A method for determining the location of an object in a
passenger compartment of a vehicle, comprising the steps of:
arranging a first ultrasonic transducer on a ceiling of the vehicle
and a second ultrasonic transducer at a different location in the
vehicle such that a first axis connecting the first and second
transducers is substantially parallel to a second axis traversing a
volume in the passenger compartment above a seat in which the
object is situated,
transmitting ultrasonic waves from the first transducer into the
passenger compartment;
receiving ultrasonic waves reflected off an object in the passenger
compartment by means of the first transducer;
calculating a first distance from the first transducer to the
object based on the time difference between the transmitted waves
and reflected waves when received by the first transducer;
transmitting different ultrasonic waves from the second transducer
into the passenger compartment;
receiving ultrasonic waves reflected off the object in the
passenger compartment by means of the second transducer;
calculating a second distance from the second transducer to the
object based on the time difference between the transmitted waves
and reflected waves when received by the second transducer; and
determining an approximate location of the object in the passenger
compartment based on the first distance and the second
distance.
2. The method of claim 1, further comprising the steps of:
transmitting different ultrasonic waves from a third ultrasonic
transducer into the passenger compartment;
receiving ultrasonic waves reflected off the object in the
passenger compartment by means of the third transducer;
calculating a third distance from the third transducer to the
object based on the time difference between the transmitted waves
and reflected waves when received by the third transducer; and
determining the approximate location of the object in the passenger
compartment based on the first distance, the second distance and
the third distance.
3. The method of claim 2, further comprising the steps of:
transmitting different ultrasonic waves from a fourth ultrasonic
transducer into the passenger compartment;
receiving ultrasonic waves reflected off the object in the
passenger compartment by means of the fourth transducer;
calculating a fourth distance from the fourth transducer to the
object based on the time difference between the transmitted waves
and reflected waves when received by the fourth transducer; and
determining the approximate location of the object in the passenger
compartment based on the first distance, the second distance, the
third distance and the fourth distance.
4. The method of claim 1 wherein said first and second distance
calculation steps each comprise the step of using waves reflected
from multiple locations on the object.
5. The method of claim 4, wherein said first and second distance
calculation steps each further comprises the step of employing
pattern recognition techniques based on the time distribution of
the echo pattern of the reflected waves.
6. The method of claim 5, wherein said step of employing pattern
recognition techniques comprises the step of generating an
algorithm by means of a neural network computer program.
7. The method of claim 1, further comprising the steps of:
identifying a first volume within the passenger compartment
adjacent the airbag where occupancy by a human at the time of
airbag deployment would place the human in danger;
identifying a second volume within the passenger compartment where
occupancy by a human requires deployment of an airbag in a
sufficiently severe vehicle crash; and
defining the second axis as the axis connecting the centers of the
first and second volumes.
8. The method of claim 1, further comprising the step of:
positioning the second transducer on a dashboard of the
vehicle.
9. The method of claim 2, further comprising the steps of:
positioning the second transducer on a dashboard of the vehicle,
and
positioning the third transducer on or adjacent an interior side
surface of said passenger compartment.
10. The method of claim 3, further comprising the steps of:
positioning the second transducer on a dashboard of the
vehicle,
positioning the third transducer on an interior side surface of
said passenger compartment, and
positioning the fourth transducer on or adjacent an interior side
surface of said passenger compartment.
11. A method for identifying an object in a passenger compartment,
comprising the steps of:
mounting at least first and second ultrasonic transducers at
different locations in the passenger compartment;
conducting training identification tests on a plurality of
different classes of objects when situated in the passenger
compartment, each of said tests comprising the steps of
transmitting ultrasonic waves from the first transducer into the
passenger compartment, receiving waves reflected off the object by
means of the first transducer, transmitting different ultrasonic
waves from the second transducer into the passenger compartment,
receiving waves reflected off the object by means of the second
transducer, and associating an object class with data from each
test,
generating a pattern recognition algorithm from the training test
results and associated object classes such that the algorithm is
able to process information from the reflected waves from the first
and second transducers and provide the identification of the class
of the object;
transmitting ultrasonic waves from the first transducer into the
passenger compartment when identification of an object in the
passenger compartment is desired;
receiving waves reflected off the object by means of the first
transducer;
transmitting different ultrasonic waves from the second transducer
into the passenger compartment when identification of the object in
the passenger compartment is desired;
receiving waves reflected off the object by means of the second
transducer; and
applying the algorithm based on the first and second reflected
waves to identify the object in the passenger compartment.
12. The method of claim 11, wherein said object class is a child
seat in the rear facing position.
13. The method of claim 11, wherein said object class is an
out-of-position occupant.
14. The method of claim 11, further comprising the step of
normalizing the reflected waves.
15. The method of claim 11, further comprising the step of
performing a system diagnosis by transmitting waves from the first
transducer to the second transducer.
16. The method of claim 11, further comprising the step of
recording the reflected waves for subsequent analysis of a vehicle
event.
17. The method of claim 11, further comprising the step of
providing an output from the system to control another vehicle
system based on the identification results.
18. The method of claim 11, further comprising the step of
combining at least two sets of reflected waves prior to their use
in identifying an object.
19. The method of claim 17, further comprising the step of
comparing at least two identification cycles before the output is
provided to the another vehicle system.
20. The method of claim 11, further comprising the step of
compensating for changes in the speed of sound.
21. The method of claim 11, further comprising the step of:
selecting the different classes of objects to be rear facing child
seats, forward facing child set, adult passengers and infant
passengers.
22. The method of claim 11, further comprising the steps of:
positioning the first transducer on a ceiling of the vehicle,
and
positioning the second transducer on a dashboard of the
vehicle.
23. A method for determining the location of an object in a
passenger compartment of a vehicle, comprising the steps of:
arranging a first receiver on a ceiling of the vehicle and a second
receiver at a different location in the vehicle such that a first
axis connecting the first and second receivers is substantially
parallel to a second axis traversing a volume in the passenger
comment above a seat in which the object is situated;
mounting a third receiver at a different location in the passenger
compartment than the first and second receiver each receiver
comprising distance measurement means;
calculating a first distance from the first receiver to the object
based on the output of the first receiver;
calculating a second distance from the second receiver to the
object based on the output of the second receiver;
calculating a third distance from the third receiver to the object
based on the output of the third receiver; and
determining an approximate location of the object in the passenger
compartment based on the first distance, the second distance and
the third distance.
24. The method of claim 23, wherein said receivers are arranged to
receive ultrasonic radiation.
25. The method of claim 23, wherein said receivers are arranged to
receive electromagnetic radiation.
26. The method of claim 23, further comprising the steps of:
mounting a fourth receiver at a different location in the passenger
compartment, the fourth receiver comprising distance measurement
means,
calculating a fourth distance from the fourth receiver to the
object based on the output of the fourth receiver,
determining an approximate location of the object in the passenger
compartment based on the first distance, the second distance, the
third distance and the fourth distance.
27. The method of claim 23, wherein the first, second and third
receivers are of the same type.
28. A method for determining the location of an object in a
passenger compartment of a vehicle, comprising the steps of:
transmitting ultrasonic waves from a first transducer into the
passenger compartment;
receiving waves reflected off an object in the passenger
compartment by means of the first transducer;
calculating a first distance from the first transducer to the
object based on the time difference between the transmitted waves
and reflected waves when received by the first transducer;
transmitting different ultrasonic waves from a second transducer
into the passenger compartment;
receiving waves reflected off the object in the passenger
compartment by means of the second transducer;
calculating a second distance from the second transducer to the
object based on the time difference between the transmitted waves
and reflected waves when received by the second transducer; and
determining an approximate location of the object in the passenger
compartment based on the first distance and the second
distance;
said first and second distance calculation steps comprising the
step of applying an algorithm generated by means of a neural
network computer program based on the time distribution of the echo
pattern of the reflected waves in order to determine the distance
from the respective transducer to the object.
Description
This application is related to: (i) U.S. patent application Ser.
No. 08/505,036 now U.S. Pat. No. 5,653,462, entitled "Vehicle
Occupant Position And Velocity Sensor" filed Jul. 21, 1995, which
is a continuation of U.S. patent application Ser. No. 08/040,978
now abandoned, filed Mar. 31, 1993, which in turn is a continuation
of U.S. patent application Ser. No. 07/878,571 now abandoned, filed
May 5, 1992; (ii) U.S. patent application Ser. No. 08/239,978 now
abandoned, entitled "Vehicle Interior Identification and Monitoring
System" filed May 9, 1994; (iii) U.S. patent application Ser. No.
08/474,786 now U.S. Pat. No. 5,845,000, entitled "Optical
Identification and Monitoring System Using Pattern Recognition for
use with Vehicles" filed Jun. 7, 1995; (iv) U.S. patent application
Ser. No. 08/474,783 now U.S. Pat. No. 5,822,707, entitled
"Automatic Vehicle Seat Adjuster" filed Jun. 7, 1995; (v) U.S.
patent application Ser. No. 08/474,784 now U.S. Pat. No. 5,748,473,
entitled "Automatic Vehicle Seat Adjuster" filed Jun. 7, 1995; and,
(vi) U.S. patent application Ser. No. 08/474,782 now U.S. Pat. No.
5,835,613, entitled "Optical Identification and Monitoring System
Using Pattern Recognition for use with Vehicles" filed Jun. 7,
1995, which are all incorporated by reference herein.
FIELD OF THE INVENTION
The present invention relates to the field of sensing, detecting,
monitoring and identifying various objects, and parts thereof,
which are located within the passenger compartment of a motor
vehicle. In particular, by means of the present invention, an
efficient and highly reliable method for detecting a rear facing
child seat (RFCS) situated in the passenger compartment in a
location where it may interact with a deploying airbag or for
detecting an out-of-position occupant is attained permitting the
selective suppression of airbag deployment when the deployment may
result in greater injury to the occupant than the crash forces
themselves. This is accomplished in part through a method of
placement of transducers and novel analysis of the signals from the
transducers.
BACKGROUND OF THE INVENTION
1. Prior Art on out-of-position occupants and rear facing child
seats
Whereas thousands of lives have been saved by airbags, a large
number of people have also been injured, some seriously, by the
deploying airbag, and thus significant improvements need to be made
in this regard. As discussed in detail in one or more of the
copending patent applications cross-referenced above, for a variety
of reasons vehicle occupants may be too close to the airbag before
it deploys and can be seriously injured or killed as a result of
the deployment thereof. Also, a child in a rear facing child seat
which is placed on the right front passenger seat is in danger of
being seriously injured if the passenger airbag deploys. For these
reasons and, as first publicly disclosed in Breed, D. S. "How
Airbags Work" presented at the International Conference on
Seatbelts and Airbags in 1993, in Canada, occupant position sensing
and rear facing child seat detection is required in order to
minimize the damages caused by deploying airbags.
Initially these systems will solve the out-of-position occupant and
the rear facing child seat problems related to current airbag
systems and prevent unneeded and unwanted airbag deployments when a
front seat is unoccupied. However, airbags are now under
development to protect rear seat occupants in vehicle crashes and
all occupants in side impacts. A system will therefore be needed to
detect the presence of occupants, determine if they are
out-of-position and to identify the presence of a rear facing child
seat in the rear seat. Future automobiles are expected to have
eight or more airbags as protection is sought for rear seat
occupants and from side impacts. In addition to eliminating the
disturbance and possible harm of unnecessary airbag deployments,
the cost of replacing these airbags will be excessive if they all
deploy in an accident needlessly.
Inflators now exist which will adjust the amount of gas flowing to
the airbag to account for the size and position of the occupant and
for the severity of the accident, e.g., based on the rate of flow
of the inflating gas. The vehicle identification and monitoring
system (VIMS) discussed in co-pending application Ser. No.
08/239,978, now abandoned, among others, will control such
inflators based on the presence and position of vehicle occupants
or of a rear facing child seat. The instant invention is an
improvement on that VIMS system and uses an advanced ultrasonic
system comprising two or more ultrasonic transmitters/receivers
combined with a trained neural network pattern recognition system
as discussed in much greater detail below.
The automatic adjustment of the deployment rate of the airbag based
on occupant identification and position and on crash severity has
been termed "smart airbags". Central to the development of smart
airbags is the occupant identification and position system
described herein. To complete the development, an anticipatory
crash detecting system such as disclosed in U.S. patent application
Ser. No. 08/247,760 now abandoned, filed May 23, 1994 is desirable.
Prior to the implementation of anticipatory crash sensing, the use
of a neural network smart crash sensor which identifies the type of
crash and thus its severity based on the early part of the crash
acceleration signature should be developed and thereafter
implemented. U.S. patent application Ser. No. 08/476,076 now U.S.
Pat. No. 5,684,701, filed Jun. 7, 1995 describes a crash sensor
based on neural networks. This crash sensor, as with all other
crash sensors, determines whether or not the crash is of sufficient
severity to require deployment of the airbag and, if so, initiates
the deployment. A neural network based on a smart airbag crash
sensor could also be designed to identify the crash and categorize
it with regard to severity thus permitting the airbag deployment to
be matched not only to the characteristics and position of the
occupant but also the severity and timing of the crash itself
The need for an occupant out-of-position sensor has also been
observed by others and several methods have been disclosed in
certain U.S. patents for determining the position of an occupant of
a motor vehicle. Each of these systems will be discussed below and
unfortunately have significant limitations.
In White et al. (U.S. Pat. No. 5,071,160), for example, a single
acoustic sensor and detector is described and, as illustrated, is
mounted lower than the steering wheel. White et al. correctly
perceive that such a sensor could be defeated, and the airbag
falsely deployed, by an occupant adjusting the control knobs on the
radio and thus they suggest the use of a plurality of such sensors
but do not disclose where they would be mounted, other than on the
instrument panel below the steering wheel, or how they would be
combined to uniquely monitor particular locations in the passenger
compartment and to identify what is occupying those locations.
Mattes et al. (U.S. Pat. No. 5,118,134) describe a variety of
methods of measuring the change in position of an occupant
including ultrasonic, active or passive infrared and microwave
radar sensors, and an electric eye. Their use of these sensors is
to measure the change in position of an occupant during a crash and
use that information to assess the severity of the crash and
thereby decide whether or not to deploy the airbag. They are thus
using the occupant motion as a crash sensor. No mention is made of
determining the out-of-position status of the occupant or of any of
the other features of occupant monitoring as disclosed in the above
cross-referenced patent applications. It is interesting to note
that nowhere does Mattes et al. discuss how to use a combination of
ultrasonic sensors/transmitters to identify the presence of a human
occupant and then to find his/her location in the passenger
compartment.
The object of an occupant out-of-position sensor is to determine
the location of the head and/or chest of the vehicle occupant
relative to the airbag since it is the impact of either the head or
chest with the deploying airbag which can result in serious
injuries. Both White et al. and Mattes et al. disclose only lower
mounting locations of their sensors which are mounted in front of
the occupant such as on the dashboard or below the steering wheel.
Both such mounting locations are particularly prone to detection
errors due to positioning of the occupant's hands, arms and legs.
This would require at least three, and preferably more, such
sensors and detectors and an appropriate logic circuitry which
ignores readings from some sensors if such readings are
inconsistent with others, for the case, for example, where the
driver's arms are the closest objects to two of the sensors.
White et al. also describe the use of error correction circuitry,
without defining or illustrating the circuitry, to differentiate
between the velocity of one of the occupant's hands, as in the case
where he/she is adjusting the knob on the radio, and the remainder
of the occupant. Three ultrasonic sensors of the type disclosed by
White et al. might, in some cases, accomplish this differentiation
if two of them indicated that the occupant was not moving while the
third was indicating that he or she was moving. Such a combination,
however, would not differentiate between an occupant with both
hands and arms in the path of the ultrasonic transmitter at such a
location that they were blocking a substantial view of the
occupant's head or chest. Since the sizes and driving positions of
occupants are extremely varied, trained pattern recognition
systems, such as neural networks, are required when a clear view of
the occupant, unimpeded by his/her extremities, cannot be
guaranteed. White et al. do not suggest the use of such neural
networks.
Fujita et al., in U.S. Pat. No. 5,074,583, describe another method
of determining the position of the occupant but do not use this
information to suppress deployment if the occupant is
out-of-position, or if a rear facing child seat is present. In fact
the closer that the occupant gets to the airbag the faster the
inflation rate of the airbag is according to the Fujita patent,
which thereby increases the possibility of injuring the occupant.
Fujita et al. do not measure the occupant directly but instead
determine his or her position indirectly from measurements of the
seat position and the vertical size of the occupant relative to the
seat. This occupant height is determined using an ultrasonic
displacement sensor mounted directly above the occupant's head.
It is important to note that in all cases in the prior art, except
those assigned to the current assignee of the instant invention,
where ultrasonic sensors are used to determine displacement, only
the initial return of reflected waves is used so that only the
distance to the closest part of the object can be determined. In
contrast, in the instant invention, the return echo pattern over
several milliseconds corresponding to the entire portion of the
passenger compartment volume of interest is analyzed providing
distance information to many points on the items occupying the
passenger compartment
2. Definitions
The use of pattern recognition is central to the instant invention
as well as those cross-referenced patent applications above.
Nowhere in the prior art, except in that assigned to the current
assignee of the instant invention, is pattern recognition which is
based on training, as exemplified through the use of neural
networks, mentioned for use in monitoring the interior passenger
compartment or exterior environments of the vehicle.
"Pattern recognition" as used herein will mean any system which
processes a signal that is generated by an object, e.g.,
representative of a pattern of returned or received impulses, waves
or other physical property specific to and/or characteristic of
and/or representative of that object, or is modified by interacting
with an object, in order to determine to which one of a set of
classes that the object belongs. Such a system might determine only
that the object is or is not a member of one specified class, or it
might attempt to assign the object to one of a larger set of
specified classes, or find that it is not a member of any of the
classes in the set. The signals processed are generally a series of
electrical signals coming from transducers which are sensitive to
acoustic (ultrasonic) radiation.
A trainable or a trained pattern recognition system as used herein
means a pattern recognition system which is taught to recognize
various patterns constituted within the signals by subjecting the
system to a variety of examples. The most successful such system is
the neural network. Thus, to generate the pattern recognition
algorithm, test data is first obtained which constitutes a
plurality of sets of returned waves, or wave patterns, from an
object and an indication of the identify of that object, i.e., a
number of different objects are tested to obtain the unique wave
patterns from each object. As such the algorithm is generated, and
stored in a computer processor, and which can later be applied to
provide the identity of an object based on the wave pattern being
received during use by a receiver connected to the processor. For
the purposes, the identity of an object sometimes applies to not
only the object itself but also to its location in the passenger
compartment. For example, a rear facing child seat is a different
object than a forward facing child seat and an out-of-position
adult is a different object than a normally seated adult.
To "identify" as used herein will mean to determine that the object
belongs to a particular set or class. The class may be one
containing, for example, all rear facing child seats, one
containing all human occupants, or all human occupants not sitting
in a rear facing child seat depending on the purpose of the system.
In the case where a particular person is to be recognized, the set
or class will contain only a single element, i.e., the person to be
recognized.
An "occupying item" of a seat may be a living occupant such as a
human being or a dog, another living organism such as a plant, or
an inanimate object such as a box or bag of groceries.
"Out-of-position" as used for an occupant means that the occupant,
either driver or passenger, is sufficiently close to the airbag
prior to deployment that he or she is likely to be more seriously
injured by the deployment event itself than by the accident. This
typically occurs when the occupant's head or chest is closer than
some distance such as about 5 inches from the deployment door of
the airbag module. The actual distance value where airbag
deployment should be suppressed depends on the design of the airbag
module and is typically further for the passenger airbag than for
the driver airbag.
"Transducer" as used herein will in general mean the combination of
a transmitter and a receiver. In come cases, the same device will
serve both as the transmitter and receiver while in others two
separate devices adjacent to each other will be used.
In the description herein on anticipatory sensing, the term
"approaching" when used in connection with the mention of an object
or vehicle approaching another will mean the relative motion of the
object toward the vehicle having the anticipatory sensor system.
Thus, in a side impact with a tree, the tree will be considered as
approaching the side of the vehicle and impacting the vehicle. In
other words, the coordinate system used in general will be a
coordinate system residing in the target vehicle. The "target"
vehicle is the vehicle which is being impacted. This convention
permits a general description to cover all of the cases such as
where (i) a moving vehicle impacts into the side of a stationary
vehicle, (ii) where both vehicles are moving when they impact, or
(iii) where a vehicle is moving sideways into a stationary vehicle,
tree or wall.
3. Pattern recognition prior art
Japanese patent 3-42337 (A) to Ueno discloses a device for
detecting the driving condition of a vehicle driver comprising a
light emitter for irradiating the face of the driver and a means
for picking up the image of the driver and storing it for later
analysis. Means are provided for locating the eyes of the driver
and then the irises of the eyes and then determining if the driver
is looking to the side or sleeping. Ueno determines the state of
the eyes of the occupant rather than determining the location of
the eyes relative to the other parts of the vehicle passenger
compartment. Such a system can be defeated if the driver is wearing
glasses, particularly sunglasses, or another optical device which
obstructs a clear view of his/her eyes. Pattern recognition
technologies such as neural networks are not used.
U.S. Pat. No. 5,008,946 to Ando uses a complicated set of rules to
isolate the eyes and mouth of a driver and uses this information to
permit the driver to control the radio, for example, or other
systems within the vehicle by moving his eyes and/or mouth. Ando
uses natural light and illuminates only the head of the driver. He
also makes no use of trainable pattern recognition systems such as
neural networks, nor is there any attempt to identify the contents
of the vehicle nor of their location relative to the vehicle
passenger compartment. Rather, Ando is limited to control of
vehicle devices by responding to motion of the driver's mouth and
eyes.
U.S. Pat. No. 5,298,732 to Chen also concentrates in locating the
eyes of the driver so as to position a light filter between a light
source such as the sun or the lights of an oncoming vehicle, and
the driver's eyes. Chen does not explain in detail how the eyes are
located but does supply a calibration system whereby the driver can
adjust the filter so that it is at the proper position relative to
his or her eyes. Chen references the use of an automatic equipment
for determining the location of the eyes but does not describe how
this equipment works. In any event, there is no mention of
monitoring the position of the occupant, other that the eyes, of
determining the position of the eyes relative to the passenger
compartment, or of identifying any other object in the vehicle
other than the driver's eyes. Also, there is no mention of the use
of a trainable pattern recognition system.
U.S. Pat. No. 5,305,012 to Faris also describes a system for
reducing the glare from the headlights of an oncoming vehicle.
Faris locates the eyes of the occupant by the use of two spaced
apart infrared cameras using passive infrared radiation from the
eyes of the driver. Again, Faris is only interested in locating the
driver's eyes relative to the sun or oncoming headlights and does
not identify or monitor the occupant or locate the occupant, a rear
facing child seat or any other object for that matter, relative to
the passenger compartment or the airbag. Also, Faris does not use
trainable pattern recognition techniques such as neural networks.
Faris, in fact, does not even say how the eyes of the occupant are
located but refers the reader to a book entitled Robot Vision
(1991) by Berthold Horn, published by MIT Press, Cambridge, Mass.
Also, Faris uses the passive infrared radiation rather than
illuminating the occupant with ultrasonic radiation as in the
instant invention.
The use of neural networks as the pattern recognition technology is
central to this invention since it makes the monitoring system
robust, reliable and practical. The resulting algorithm created by
the neural network program is usually only a few lines of code
written in the C computer language as opposed to typically hundreds
of lines when the techniques of the above patents to Ando, Chen and
Faris are implemented. As a result, the resulting systems are easy
to implement at a low cost making them practical for automotive
applications. The cost of the ultrasonic transducers, for example,
is expected to be less than about $1 in automotive quantities.
Similarly, the implementation of the techniques of the above
referenced patents requires expensive microprocessors while the
implementation with neural networks and similar trainable pattern
recognition technologies permits the use of low cost
microprocessors typically costing less than about $5.
The present invention uses sophisticated trainable pattern
recognition capabilities such as neural networks. Usually the data
is preprocessed, as discussed below, using various feature
extraction techniques. A non-automotive example of such a pattern
recognition system using neural networks on sonar signals is
discussed in two papers by Gorman, R. P. and Sejnowski, T. J.
"Analysis of Hidden Units in a Layered Network Trained to Classify
Sonar Targets", Neural Networks, Vol. 1. pp. 75-89, 1988, and
"Learned Classification of Sonar Targets Using a Massively Parallel
Network", IEEE Transactions on Acoustics, Speech, and Signal
Processing, Vol. 36, No. 7, July 1988. Examples of feature
extraction techniques can be found in U.S. Pat. No. 4,906,940
entitled "Process and Apparatus for the Automatic Detection and
Extraction of Features in Images and Displays" to Green et al.
Examples of other more advanced and efficient pattern recognition
techniques can be found in U.S. Pat. No. 5,390,136 entitled
"Artificial Neuron and Method of Using Same and U.S. patent
application Ser. No. 08/076,601 entitled "Neural Network and Method
of Using Same" to Wang, S. T. Other examples include U.S. Pat. Nos.
5,235,339 (Morrison et al.), 5,214,744 (Schweizer et al), 5,181,254
(Schweizer et al), and 4,881,270 (Knecht et al). All of the above
references are included herein by reference.
4. Ultrasonics
Ultrasonics can be used in several configurations for monitoring
the interior of a passenger compartment of an automobile as
described in the cross referenced patents and patent applications.
In one known system, for example, two ultrasonic sensors are placed
on the A-pillar and in another system, a third sensor is
additionally placed in the headliner. It has been found in both of
these cases that even though the proper identification is made in a
high percentage of the cases, there are still a small but
significant number of cases where an error in diagnosis is made
based on the information received from the sensors. These systems,
although a significant improvement over the other prior art, still
fail to achieve the very high reliability desired by the automobile
manufacturers.
In the cases of the instant invention as will discussed in more
detail below, regardless of the number of transducers used, a
trained pattern recognition system, as defined above, is used to
identify and classify, and in some cases to locate, the illuminated
object and its constituent parts.
5. Applications
The applications for this technology are numerous as described in
the copending patent applications listed above. However, the main
focus of the instant invention is for the detection of the presence
of a child seat in the rear facing position or an out-of-position
occupant and the detection of an occupant in a normal seating
position. In the former two cases, deployment of the airbag will be
suppressed and in the latter, it will be enabled.
OBJECTS AND SUMMARY OF THE INVENTION
In general, it is an object of the present invention to provide an
new and improved method for identifying the presence and
orientation of an object in a vehicle.
It is another broad object of the present invention to provide a
method for accurately detecting the presence of a rear-facing child
seat in order to prevent an airbag from deploying, which airbag
would impact against the rear-facing child seat if deployed.
It is yet another broad object of the present invention to provide
a method for accurately detecting the presence of an
out-of-position occupant in order to prevent one or more airbags
from deploying, which airbag(s) would impact against the head or
chest of the occupant during its initial deployment phase causing
injury or possible death to the occupant.
This invention is a system to identify, locate and monitor
occupants, including their parts, and other objects in the
passenger compartment and in particular a child seat in the rear
facing position or an out-of-position occupant, by illuminating the
contents of the vehicle and objects outside of the vehicle with
ultrasonic radiation, e.g., by transmitting ultrasonic radiation
waves from an ultrasonic wave generating apparatus, and receiving
reflected ultrasonic radiation using two or more ultrasonic
transducers properly located in the vehicle passenger compartment,
and in specific predetermined optimum locations. More particularly,
this invention relates to a method for appropriately locating and
mounting the ultrasonic transducers and for analyzing the reflected
radiation, i.e., from any object to which the ultrasonic waves
impact, in order to achieve an accuracy of recognition heretofore
not possible. Outputs from the ultrasonic receivers, are analyzed
by appropriate computational means employing trained pattern
recognition technologies, to classify, identify and/or locate the
contents, and/or determine the orientation of, e.g., a rear facing
child seat. In general, the information obtained by the
identification and monitoring system is used to affect the
operation of some other system in the vehicle and particularly the
passenger and/or driver airbag systems, which may include a front
airbag, a side airbag, a knee bolster, or combinations of the same.
However, the information obtained can be used for a multitude of
other vehicle systems.
When the vehicle interior monitoring system of this invention is
installed in the passenger compartment of an automotive vehicle
equipped with a occupant protective device, such as an inflatable
airbag, and the vehicle is subjected to a crash of sufficient
severity that the crash sensor has determined that the protective
device is to be deployed, the system, in accordance with the
invention, has previously determined, (i.e., prior to the
deployment) whether a child placed in the rear facing position in
the child seat is present and if so, a signal has been sent to the
control circuitry that the airbag should be disabled, that is, not
deployed in the crash. The system of this invention also determines
the position of the vehicle occupant relative to the airbag and
disables deployment of the airbag if the occupant is positioned so
that he/she is likely to be injured by the deployment of the
airbag.
Principal objects and advantages of the methods in accordance with
the invention are:
1. To provide a reliable method for recognizing the presence of a
rear facing child seat on a particular seat of a motor vehicle and
to use this information to affect the operation of another vehicle
system such as the airbag system.
2. To provide a reliable method for recognizing the presence of a
human on a particular seat of a motor vehicle and to use this
information to affect the operation of another vehicle system such
as the airbag, heating and air conditioning, or entertainment
systems, among others.
3. To provide a reliable method for recognizing the presence of a
human on a particular seat of a motor vehicle and then to determine
his/her position and to use this position information to affect the
operation of another vehicle system.
4. To provide a reliable method for determining the position,
velocity or size of an occupant in a motor vehicle and to utilize
this information to control the rate of gas generation, or the
amount of gas generated by an airbag inflator system or other
aspects of the airbag system.
5. To provide a reliable method for determining in a timely manner
that an occupant is out of position, or will become out of
position, and likely to be injured by a deploying airbag and to
then output a signal to suppress the deployment of the airbag.
6. To provide a method for locating transducers within the
passenger compartment at specific locations such that the highest
reliability of classification of objects and their position is
obtained from the signals generated by the transducers.
These and other objects and advantages will become apparent from
the following description of the preferred embodiments of the
vehicle identification and monitoring system of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The following drawings are illustrative of embodiments of the
invention and are not meant to limit the scope of the invention as
encompassed by the claims. In particular, the illustrations below
are limited to the monitoring of the front passenger seat for the
purpose of describing the invention. Naturally, the invention
applies as well to the other seating positions in the vehicle and
particularly to the driver position.
FIG. 1 is a perspective view of a vehicle containing two adult
occupants on the front seat with the vehicle shown in phantom
illustrating one preferred location of the ultrasonic transducers
placed according to the methods taught in this invention.
FIG. 2 is a view as in FIG. 1 with the passenger occupant replaced
by a child in a forward facing child seat.
FIG. 3 is a view as in FIG. 1 with the passenger occupant replaced
by a child in a rearward facing child seat.
FIG. 4 is a view as in FIG. 1 with the passenger occupant replaced
by an infant in an infant seat.
FIG. 5 is a diagram illustrating the interaction of two ultrasonic
sensors and how this interaction is used to locate a circle is
space.
FIG. 6 is a view as in FIG. 1 with the occupants removed
illustrating the location of two circles in space and how they
intersect the volumes characteristic of a rear facing child seat
and a larger occupant.
FIG. 7 illustrates a preferred mounting location of a three
transducer system.
FIG. 8 illustrates a preferred mounting location of a four
transducer system.
FIG. 9 is a plot showing the target volume discrimination for two
transducers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, where like reference numbers
represent like or similar parts, a section of the passenger
compartment of an automobile is shown generally as 100 in FIG. 1. A
driver 101 of a vehicle sits on a seat 102 behind a steering wheel,
not shown, and an adult passenger 103 sits on seat 104 on the
passenger side. Two transmitter and receiver assemblies 110 and
111, also referred to herein as transducers, are positioned in the
passenger compartment 100, one transducer 110 is arranged on the
headliner adjacent or in proximity to the dome light and the other
transducer 111 is arranged on the center of the top of the
dashboard (the methodology leading to the placement of these
transducers is central to the instant invention as explained in
detail below). In this situation, the invention will reliably
detect that an occupant is sitting on seat 104 and deployment of
the airbag is enabled in the event that the vehicle experiences a
crash. Transducers 110,111 are placed with their separation axis
parallel to the separation axis of the head, shoulder and rear
facing child seat volumes of occupants of an automotive passenger
seat and in view of this specific positioning, are capable of
distinguishing the different configurations.
In FIG. 2, a forward facing child seat 120 containing a child 121
replaces the adult passenger 103 as shown in FIG. 1. In this case,
it is required that the airbag not be disabled in the event of an
accident. However, in the event that the same child seat is placed
in the rearward facing position as shown in FIG. 3, then the airbag
is required to be disabled since deployment of the airbag in a
crash can seriously injure or even kill the child. Furthermore, as
illustrated in FIG. 4, if an infant 131 in an infant carrier 130 is
positioned in the rear facing position of the passenger seat, the
airbag should be disabled for the reasons discussed above. It
should be noted that the disabling or enabling of the passenger
airbag relative to the item on the passenger seat may be tailored
to the specific application. For example, in some embodiments, with
certain forward facing child seats, it may in fact be desirable to
disable the airbag. The selection of when to disable or enable the
airbag, as a function of the item in the passenger seat and its
location, is made during the programming or training stage of the
sensor system and, in most cases, the criteria set forth above will
be applicable i.e., enabling airbag deployment for a forward facing
child seat and an adult in a proper seating position and disabling
airbag deployment for a rearward facing child seat and infant and
for any occupant who is out-of-position and in close proximity to
the airbag module. The sensor system in accordance with the
invention may however be programmed according to other
criteria.
Several systems have been devised to discriminate between the four
cases illustrated above but none have shown a satisfactory accuracy
or reliability of discrimination. Some of these systems appear to
work as long as the child seat is properly placed on the seat and
belted in. So called "tag systems", for example, whereby a device
is placed on the child seat which is electromagnetically sensed by
sensors placed within the seat have not proven reliable. They
function well as long as the child seat is restrained by a seat
belt but when this is not the case they have a high failure rate.
Since the seatbelt usage of the population of the United States is
only about 50% at the present time, it is quite likely that a
significant percentage of child seats will not be properly belted
into the seat and thus children will be subjected to injury and
death in the event of an accident.
The methodology of this invention was devised to solve this
problem. To understand this methodology, consider two ultrasonic
transmitters and receivers 110 and 111 (transducers) which are
connected by an axis AB in FIG. 5. Each transmitter radiates a
signal which is primarily confined to a cone angle with its origin
at the transmitter. For simplicity, assume that the transmitter and
receiver are the same device although in some cases a separate
device will be used for each function. When a transducer sends out
a burst of waves, to thereby illuminate the passenger compartment
with ultrasonic radiation, and then receives a reflection from some
object in the passenger compartment, the distance of the object
from the transducer can be determined by the time delay between the
transmission of the waves and the reception of the reflected
waves.
When looking at a single transducer, it is not possible to
determine the direction to the object which is reflecting the
signal but it is possible to know only how far that object is from
the transducer (i.e., a single transducer enables a distance
measurement but not a directional measurement). In other words, the
object may be at a point along a three-dimensional sphere having
its origin at the transducer and a radius equal to the distance. If
two transducers, such as 110 and 111 in FIG. 5, are used and both
transducers receive a reflection from an object, presumably the
same object which is facilitated by proper placement of the
transducers, which reflection depends on the distance from the
object to the respective transducer. If it is assumed for the
purposes of this analysis that the two transducers act
independently, that is, they only listen to the reflections of
waves which they themselves transmitted, then each transducer knows
the distance to the reflecting object but not its direction. If we
assume that the transducer radiates ultrasound in all directions,
each transducer knows that the object is located on a spherical
surface A'.B' a respective known distance from the transducer,
i.e., each transducer knows that the object is a specific distance
from that transducer which may or may not be the same distance
between the other transducer and the same object. Since now there
are two transducers, and the distance of the reflecting object is
known relative to each of the transducers, the actual location of
the object resides on a circle which is the intersection of the two
spherical surfaces A'.B'. This circle is labeled C in FIG. 5. At
each point along circle C, the distance to the transducer 110 is
the same and the distance to the transducer 111 is the same.
For many cases, the mere knowledge that the object lies on a
particular circle is sufficient since it is possible to locate the
circle such that the only time that an object lies on a particular
circle that its location is known. That is, the circle which passes
through the area of interest otherwise passes through an volume
where no objects can occur. Thus, the mere calculation of the
circle in this specific location, which indicates the presence of
the object along that circle, provides valuable information
concerning the object in the passenger compartment which may be
used to control or affect another system in the vehicle such as the
airbag system. FIG. 6 for example illustrates two circles D and E,
of interest which represent the volume which is usually occupied
when the seat is occupied by a person not in a child seat, C, or by
a forward facing child seat and the volume normally occupied by a
rear facing child seat, respectively. Thus, if the circle generated
by the system, i.e., by appropriate processor means which receive
the distance determination from each transducer and creates the
circle from the intersection of the spheres which represent the
distance from the transducers to the object, is at a location which
is only occupied by an adult passenger, the airbag would not be
disabled since its deployment in a crash is desired. On the other
hand, if a circle is at a location occupied only by a rear facing
child seat, the airbag would be disabled.
From the above discussion, a method of transducer location is
disclosed which provides unique information to differentiate
between (i) a forward facing child seat or a forward properly
positioned occupant where airbag deployment is desired and (ii) a
rearward facing child seat and an out-of-position occupant where
airbag deployment is not desired. In actuality, the algorithm used
to implement this theory does not directly calculate the surface of
spheres or the circles of interaction of spheres. Instead, a
pattern recognition system is used to differentiate
airbag-deployment desired cases from those where the airbag should
not be deployed. For the pattern recognition system to accurately
perform its function, however, the patterns presented to the system
must have the requisite information. That is, a pattern of
reflected waves from an occupying item in a passenger compartment
to various transducers must be uniquely different for cases where
airbag deployment is desired from cases where deployment is not
desired. The theory described above and in more detail below
teaches how to locate transducers within the vehicle passenger
compartment so that the patterns of reflected waves will be easily
distinguishable for cases where airbag deployment is desired from
those where deployment is not desired. In the case presented thus
far, it has been shown that in some implementations the use of only
two transducers can result in the desired pattern differentiation
when the vehicle geometry is such that two transducers can be
placed such that the circles D (airbag enabled) and E (airbag
disabled) fall outside of the vehicle (and thus cannot be occupied)
except where they are in the critical regions where positive
identification of the condition occurs.
For those cases where it is not possible to achieve this isolation,
a third transducer 112 can be used as shown in FIG. 7 which now
provides a third set of spherical surfaces relative to the third
transducer. Transducer 112 is positioned on the passenger side of
the A-pillar (which is a preferred placement if the system is
designed to operate on the passenger side of the vehicle). Three
spherical surfaces now intersect in only two points thus
substantially reducing the area of uncertainty. Finally, with the
addition of a fourth transducer 113 as shown in FIG. 8, even
greater accuracy is attained. Transducer 113 is positioned on the
ceiling of the vehicle close to the passenger side door. In FIG. 8,
lines connecting the transducers C and D and the transducers A and
B are substantially parallel permitting an accurate determination
of asymmetry and thereby object rotation. Thus, for example, if the
infant seat is placed on an angle as shown in FIG. 4, this
condition can be determined and taken into account when the
decision is made to disable the deployment of the airbag.
The discussion above has centered on determining whether the two
target volumes, that adjacent the airbag and that adjacent the
upper portion of the vehicle seat, are occupied. Other systems have
been described in the above referenced patents using a sensor
mounted on or adjacent the airbag module and a sensor mounted high
in the vehicle to monitor the space near the vehicle seat. Such
systems use the sensors as independent devices and do not use the
combination of the two sensors to determine where the object is
located. In fact, the location of such sensors is usually poorly
chosen so that it is easy blind either or both with a newspaper,
for example. Furthermore, no system has heretofore been disclosed
which uses more than two transducers in such a manner that one or
more can be blocked without causing serious deterioration of the
system. Again, the examples here have been for the purpose of
suppressing the deployment of the airbag when it is necessary to
prevent injury. The sensor system disclosed can be used for many
other purposes such as disclosed in the above mention patent
applications assigned to the same company as the instant invention.
The ability to use the sensors for these other applications in
generally lacking in the systems disclosed in the other referenced
patents.
Considering once again the condition of FIGS. 1 through 6 where two
transducers are used, a plot can be made showing the reflection
times of the objects which are located in the region of curve E and
curve F of FIG. 6. This plot is shown on FIG. 9 where the c's
represent reflections from rear facing child seats from various
tests where the seats were placed in a variety of different
positions and similarly the s's and h's represent shoulders and
heads respectively of various forward facing human occupants. Note
that there is a region of separation between corridors that house
the different object classes. It is this fact which is used in
conjunction with neural networks, as described in the above
referenced patent applications, which permit accurate
discrimination of rear facing child seats from forward facing
humans. Heretofore before the transducers were appropriately
located to separate these two zones, the entire discrimination task
was accomplished using neural networks. There was significant
overlap between the reflections from the various objects and
therefore separation was done based on patterns of the reflected
waves. By carefully orienting the transducers so as to create this
region of separation of the critical surfaces wherein all of the
rear facing child seat data falls within a known corridor, the task
remaining for the neural networks is substantially simplified with
the result that the accuracy of identification is substantially
improved.
Using two transducers as shown in FIGS. 1 through 6 an accuracy
based on a matrix comprising in excess of 15,000 tests for the
training set and 1000 tests for the test set yielded results of
approximately 100% accuracy for the training set and about 90% to
about 95% for the test set. When the third transducer was added,
the accuracy on the test set increased to in excess of about 99%
and with the fourth transducer the accuracy was measurably higher.
An exact determination of the accuracy cannot be done without a
significantly larger test series.
It is important to realize that these accuracies are based on a
data set which assigns the same weight to a normally belted rear
facing child seat as to one which is rotated about 45 degrees, is
at the extreme forward position of the seat and where the seat back
is down, for example. That is, the normal rear facing seat position
which in reality represents the majority of cases represents only a
single point in the test series while there are many extreme cases
which may never actually occur which have the same weight in the
test series. Thus the accuracy percentages quoted above are quite
conservative and the actual accuracy taking into account actual
passenger seat usage patterns is at least ten times higher.
Three general classes of child seats exist as well as several
models which are unique. First there is the infant only seat as
shown in FIG. 4 which is for occupants weighing up to about 20
pounds. This is supposed to be only placed in the rear facing
position. The second which is illustrated in FIGS. 2 and 3 is for
children from about 20 to about 40 pounds and can be used in both
the forward and rear facing position and the third is for use only
in the forward facing position and is for children weighing over
about 40 pounds. All of these seats as well as the unique models
were used as part of the 15,000 test set. For each child seat there
are several hundred unique tests representing virtually every
possible position of that seat within the vehicle. Tests are run,
for example, with the seat tilted 22 degrees, rotated 17 degrees,
placed on the front of the seat with the seat back fully up with
the seat fully back and with the window open as well as all
variations of there parameters.
A large number of cases is also run with various clothing, toys,
bottles, blankets etc. added to the child seat in an attempt to
defeat the system.
Similar variations are used for the occupants which include all
sizes of occupant with all manner of clothing and reading maps or
newspapers, leaning forward to adjust the radio, for example also
included are cases where the occupant puts his/her feet onto the
dashboard or otherwise assumes a wide variety of unusual positions.
When all of the above configurations are considered along with many
others not mentioned, the total number of configurations which are
used to train the pattern recognition system can equal 500,000 or
more. The goal is to include in the configuration training set
representations of all cases which positions occur in actual use.
Since the system is virtually 100% accurate in making the correct
decision for cases which are similar to those in the training set,
the total system accuracy increases as the size of the training set
increases. To collect data for 500,000 vehicle configurations is
not a formidable task. A trained technician crew can typically
collect data on in excess of 2000 configurations per hour. It is
important to note that it is not necessary to train on every
vehicle produced but rather on each platform. A platform is an
automobile manufacturer's designation of a group of vehicle models
which are built on the same vehicle structure.
More detail on the operation of the transducers and control
circuitry as well as the neural network is provided in the above
referenced patent applications and is included herein as if the
entire text of those patents were reproduced here. One particular
example of a successful neural network for the two transducer case
had 78 input nodes, 6 hidden nodes and one output node. The weights
of the network were determined by supervised training as described
in the referenced patent applications and in more detail in the
references cited therein.
Finally, the system is trained and tested with situations
representative of the manufacturing and installation tolerances
which occur during the production and delivery of the vehicle as
well as usage and deterioration effects. Thus, for example, the
system is tested with the transducer mounting positions shifted by
up to one inch in any direction and rotated by up to 15 degrees,
with an accumulation of dirt and other variations. This tolerance
to vehicle variation also permits the installation of the system
onto a different model vehicle with, in many cases, only minimal
retraining of the system.
The speed of sound varies with temperature, humidity, and pressure.
This is compensated for by using the fact that the geometry between
the transducers in known and the speed of sound can therefore be
measured. Thus, on vehicle startup and as often as desired
thereafter, the speed of sound is measured by one transducer, such
as transducer 110 in FIG. 4, sending a signal which is directly
received by another transducer and since the distance separating
them is known, the speed of sound can be calculated and the system
automatically adjusted to remove the variation due to the change in
the speed of sound. Therefore, the system operates with same
accuracy regardless of the temperature, humidity or atmospheric
pressure. It may even be possible to use this technique to also
automatically compensate for any effects due to wind velocity
through an open window. An additional benefit of this system is
that it can be used to determine the vehicle interior temperature
for use by other control systems within the vehicle since the
variation in the velocity of sound is a strong function of
temperature and a weak function of pressure and humidity.
Another important feature of this invention is the realization that
motion of the vehicle can be used in a novel manner to
substantially increase the accuracy of the system. Ultrasonic waves
reflect on most objects as light off a mirror. This is due to the
relatively long wave length of ultrasound as compared with light.
As a result certain reflections can overwhelm the receiver and
reduce the available information. When readings are taken while the
vehicle is in motion, and these readings averaged over several
transmission/reception cycles, the motion of the vehicle causes
various surfaces to change their angular orientation slightly but
enough to change the reflective pattern and reduce this mirror
effect. The net effect is that the average of several cycles gives
a much clearer image of the reflecting object than is obtainable
from a single cycle. This then provides a better image to the
neural network and significantly improves the identification
accuracy of the system.
Although most of the above discussion has been centered around the
rear facing child/human occupant discrimination problem, this same
methodology permits a better determination of the out-of-position
occupant. Since it is now possible to accurately discriminate
between the head and shoulders and other objects, the displacement
of the head and shoulders, as well as their initial position, can
be accurately monitored and if they get too close to the airbag
prior to deployment the deployment can be suppressed. This can of
course be done for both the driver and passenger and for all other
vehicle occupants.
Thus, to reiterate the more novel features of the invention, this
application discloses (1) the application of two-sensor pairs to
single-axis monitoring of target volumes; (2) the use of two-sensor
sites spanning a target volume to sense object positions (spanning
means that the sites extend beyond the objects along the axis
sensing object positions between the sites); (3) the orientation of
sensor axis for optimal target discrimination parallel to the axis
of separation of distinguishing target features; (4) the definition
of head and shoulders and supporting surfaces as defining humans
for rear facing child seat detection and forward facing human
detection; (5) the adjusting echo pattern sample delay and interval
to correspond to critical spatial target locations; (6) the
normalization of signals to eliminate calibration drift and
variation effects; (7) the correction of echo sample delay and
interval times by cross-checks of sensors; (8) an out-of-position
occupant sensing with same system; (9) the provision for recording
seat occupant position at time of crash; (10) the improvement of
system reliability by comparing successive series of decisions (to
enable/disable the airbag); (11) multi-shot signal to noise ratio
enhancement; and (12) the update of decision every 1 to 10
seconds.
Significant aspects of the invention are thus as follows:
1) Ultrasonic transducers are used singly to send and receive
ultrasonic waves for object and occupant detection in automotive
seats.
2) Ultrasonic transducers are used in pairs as sender and receiver
at a common location to send and receive ultrasonic waves with
respect to an automotive passenger seat.
3) Ultrasonic transducers are used singly or in pairs to send and
receive ultrasonic waves at two locations relative to an automotive
seat position thus defining a sensing axis defined as the line
extending between the transducers and allowing reflective surfaces
to be located in two dimensions relative to that axis.
4) Transducers at the end points of the axis defined by their
positions locate objects in two dimensions as being on circles
centered on the axis and the radius of the circle.
5) Cylindrical coordinates resulting from geometry described in 4)
locate objects to lie on the circles of the two-dimensional
coordinate system.
6) Two objects lying in a volume sensed by the above transducers
are distinguishable if they lie on separate and distinct circles of
the coordinate system.
7) The coordinate system is constructed to have unique and separate
coordinate circles pass through the locations of objects requiring
distinct identification.
8) Transducers lying at the end points of an axis defined by their
position in an automotive interior locate objects in two dimensions
as the flight time of ultrasonic waves to the objects and their
reflections back to the transducers.
9) Ultrasonic transducers may be used in the above geometries as a
sender receiver at each end of the referent coordinate axis.
10) The direct measure of the location of an object in the sensing
volume of the two transducers is the `time of flight` of an
ultrasonic pulse.
11) The time of flight converts to the geometric coordinate of 8)
by means of the speed of sound: Xi=Cs*Ti.
12) The Cylindrical and Linear coordinate systems correlate and
mutually transform.
13) To locate distinct objects the transducers are positioned to
define an axis which is placed to be parallel to the separation
axis of the objects to be distinguished. Two separate circles of
the cylindrical coordinate system uniquely intercept and locate the
two objects. The echo flight times for each transducer-object pair
are the practical measures of the system.
14) The aforementioned ultrasonic system is used to detect a
Rear-Facing Child Seat (RFCS) in the passenger seat of an
automotive vehicle.
15) The RFCS is distinguished from a Forward-Facing Human by virtue
of the head and shoulder volumes and their reflecting surfaces
and/or any support-protective surfaces around them.
16) Two transducers placed with their separation axis parallel to
the separation axis of the head and shoulder volumes of occupants
of an automotive passenger seat are capable of distinguishing the
different configurations.
17) The echo times are the measurable coordinates of choice for
distinguishing the object configurations.
18) A target volume is monitored by sending and receiving
ultrasonic pulses to be reflected from targets in the sensed
volume, the reflected pulse train being the 2-dimensional signature
of surfaces in the target volume.
19) The correspondence of echo times to geometric location of
critical, object-defining surfaces within the target volume means
the echo pattern contains identifying information regarding the
occupancy of the sensed target volume.
20) Pattern recognition techniques disclosed in prior applications
employing neural networks are used in a novel manner to correlate
the echo patterns with various conditions of seat occupancy.
21) Specific ranges of volume are monitored for critical Child Seat
information by limiting echo pattern analysis to time windows
corresponding to critical surfaces.
22) Echo signals are normalized to remove effects of sensor
calibration including drift.
23) Speed of sound varies with atmospheric temperature, pressure
and humidity. The changes affect the time-segmentation of echo
pattern data into correct, corresponding geometric coordinate
sample spaces. Speed of sound is correctly measured by the
measurement of direct time of flight of an echo pulse between a
pair of transducers at a known separation and is used to correct
the segmentation of the echo pattern. Standard temperature and
pressure (STP) is the normal reference point for the system.
24) The time delays and any echo pattern sample times are adjusted
to SIP conditions.
25) The communication of one transducer with another allows a
diagnostic of transducer function and calibration.
26) The above described-system can be trained to `recognize`
Out-of-Position occupants.
27) The above-described system can provide a record of pre-impact
occupant position to the crash-recording black box allowing
post-crash position analysis.
28) The system can update every 1 or more seconds or more
frequently if desired.
29) A time-record of measured seat occupancy, i.e., repeated shots
over time, can be summed, averaged or compared to provide more
reliable decisions.
30) Decisions confirmed by repeated position measurement are not
changed by just one unexpected change, but are used as part of the
time-averaged decision process further increasing the accuracy of
the decision system.
31) Many shots at one `moment` in time are averaged to improve
signal-to-noise ratios.
32) Motion of the vehicle is desirable to average out certain echo
patterns removing ultrasonic interference patterns. This fact is
used to further improve system accuracy.
33) The Rear Facing Child Seat Detector (RFCSD) system is
transferable from one vehicle model to another with minimum
retraining when the transducer geometry is referenced to the
passenger seat geometry.
34) The RFCSD system can be based on triangulation with three
transducers for improved reliability by means of triangulation.
35) The RFCSD system can be based on four transducers for
redundancy of information and allowing for soft failure of the
system--by means of two parallel axes spanning the target volume on
each of two sides.
The methods above have been described in connection with the use of
ultrasonic transducers. Many of the methods, however, are also
applicable to optical radar and other sensing systems and where
applicable, this invention is not limited to ultrasonic systems. In
particular, an important feature of this invention is the use of
three or more separately located receivers such that the system
still operates with high reliability if one of the receivers is
blocked by some object such as a newspaper. This feature is also
applicable to systems using electromagnetic radiation instead of
ultrasonic. With the use of electromagnetic radiation and the
advances which have recently been made in the field of very low
light level sensitivity, it is now possible in some implementations
to eliminate the transmitters and use background light as the
source of illumination along with using a technique such as
auto-focusing to obtain the distance from the receiver to the
object. Thus, only receivers would be required further reducing the
complexity of the system.
In the preferred embodiments described herein, each transducer
mounting location contains a single transmitter and receiver pair
or a device which functions both as a transmitter and a receiver.
In each case, the data entered into the pattern recognition
algorithm (in other words the data from which the pattern algorithm
was generated) was data obtained by receivers receiving reflections
from objects of waves sent by only the transmitters associated with
the respective receivers. Although this is the preferred
arrangement, a similar system can be designed based on reflections
from waves emitted from other transmitters which are not co-located
with the respective receivers.
Although implicit in the above discussion, an important feature of
this invention which should be emphasized is the distributed nature
of the transducer mountings. Other systems which have attempted to
solve the RFCS and out-of-position problems have relied on a single
or at most two transducer mounting locations. Such systems can be
easily blinded by a newspaper or by the hand of an occupant, for
example, which is imposed between the occupant and the transducers.
This problem is almost completely eliminated through the use of
three or more transducers which are mounted so that they have
distinctly different views of the passenger compartment volume of
interest. If four transducers are used as illustrated in the
distributed system of FIG. 8, for example, the system suffers only
a slight reduction in accuracy even if two of the transducers are
covered so as to make them inoperable.
Although several preferred embodiments are illustrated and
described above, there are other possible combinations using
different sensors located at different positions within the
automobile passenger compartment which measure either the same or
different characteristics of an occupying object to accomplish the
same or similar goals as those described herein. There are also
numerous additional applications in addition to those described
above including, but not limited to, monitoring the driver seat,
the center seat or the rear seat of the vehicle or for controlling
other vehicle systems in addition to the airbag system. This
invention is not limited to the above embodiments and should be
determined by the following claims.
* * * * *