ABM
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`A seated-state detecting unit for determining the occupancy of a seat in a
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`passenger compartment of a vehicle including wave transmitting sensors such as ultrasonic
`sensors for transmitting waves into the passenger compartment toward the seat and
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`receiving reflected waves from the passenger compartment and specifically from the seat
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`and its contents, 3 weight sensor for detecting weight applied onto the seat, and an
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`evaluation circuit to which outputs of the wave sensors and the weight sensors are input
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`and which evaluates a seated-state, based on the outputs from the wave sensors and
`weight sensor.
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`Hyundai Exhibit 1012
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`Page 1 of 30
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`Hyundai Exhibit 1012
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`ATI-170
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`SEATED-STATE DETECTING APPARATUS
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`W
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`FIELD OF THE INVENTION
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`5
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`The present invention relates to a seated-state detecting apparatus that evaluates
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`the seated state of an occupant in a compartment with a plurality of sensors such as
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`ultrasonic sensors, and affects the operation of another system in the vehicle in response to
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`the detected seated-state and more particularly to a seated-state detecting apparatus
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`suitable for use in a deployable occupant protection apparatus such as airbag systems.
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`BACKGRQQEQ OF THE INVENTION
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`Automobiles equipped with airbags are well known in the prior art. In such airbag
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`systems, the car crash is sensed and the airbags rapidly inflated thereby ensuring the safety
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`of an occupation in a car crash. Many lives have now been saved by such airbag systems.
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`However, depending on the seated state of an occupant, there are cases where his
`or her life cannot be saved even by present airbag systems, For example, when 8.
`passenger is seated on the front passenger seat in a position other than a forward facing,
`normal state, e.g., when the passenger is out ofposition and near the deployment door of
`the airbag, there will be cases when the occupant will be seriously injured or even killed by
`the deployment of the airbag.
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`Also, sometimes a child seat is placed on the passenger seat in a rear facing
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`position and there are cases where a child sitting in such a seat has been seriously injured
`or killed.
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`Furthermore, in the case of a vacant seat, there is no need to deploy an airbag, and
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`25
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`in such a case, deploying the airbag is undesirable due to a high replacement cost and
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`possible release of toxic gases into the passenger compartment. Nevertheless, most airbag '
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`systems will deploy the airbag in a vehicle crash even if the seat is unoccupied.
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`For these reasons, there has been proposed a seated-state detecting unit such as
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`disclosed in the following U, S. Patents and Patent applications, which are included herein
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`30
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`by reference, assigned to the current assignee of the present application: Breed et a1 (U.S.
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`Patent 5,563,462); Breed et a] (U.8. Patent application Serial No. 08/640,068 filed April
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`30, 1996); Breed et al (US. Patent application Serial No. 08/474,783 filed June 7, 1995):
`
`Breed et al (US. Patent application Serial No. 08/476,882 filed June 7, 1995; Breed et al
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`(US. Patent application Serial No. 08/474,784 filed June 7, 1995; and Varga et al (US.
`
`Patent application Serial No. 08/798,029 filed February 6, 1997). Typically, in some of
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`these designs four sets of ultrasonic sensors are installed at four points in a vehicle
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`passenger compartment for transmitting ultrasonic or electromagnetic waves toward the
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`passenger or driver’s seat and receiving the reflected waves, Using appropriate hardware
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`and software, the approximate configuration of the occupancy of either the passenger or
`driver seat can be determined thereby identifying and categorizing the occupancy of the
`relevant seat.
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`However, in the aforementioned prior art using ultrasonics, the pattern of reflected
`ultrasonic waves from an adult occupant who may be out of position is sometimes similar
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`to the pattern of reflected waves from a rear facing child seat, Also, it is sometimes
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`difficult to discriminate the wave pattern of a normally seated child with the seat in a
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`rearward position from an empty seat with the seat in a more forward position. In other
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`cases, the reflected wave pattern from a thin slouching adult can be similar to that from a
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`rear facing child seat. In still other cases, the reflected pattern from a passenger seat which
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`is in a forward position can be similar to the reflected wave pattern from a seat containing
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`a fonivard facing child seat or a child sitting on the passenger seat. In each of these cases,
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`the prior art ultrasonic systems can suppress the deployment of an airbag when
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`deployment is not desired or, alternately, can enable deployment when deployment is
`desired.
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`If the discrimination between these cases can be improved, then the reliability of
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`the seated-state detecting unit can be improved and more people saved from death or
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`serious injury. In addition, the unnecessary deployment of an airbag can be prevented.
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`Accordingly, it is a principal object of the present invention to provide a seated-
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`state detecting unit that evaluates the seated-state of a passenger or driver seat by a
`combination of ultrasonic sensors and additional sensors.
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`Another object of the present invention is to provide a seated-state detecting unit
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`which is capable of reliably performing discrimination between a normally seated
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`passenger and a forward facing child seat, discrimination between an abnormally seated
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`passenger and a rear facing child seat, and discrimination of whether or not the seat is
`empty.
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`Further objects of the present invention will become apparent from the following
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`discussion of the preferred embodiments of the invention.
`
`SUMMARY OF THE INVENTION
`
` OBJECTS OF THE INVENTION
`
`A seated-state detecting unit according to the present invention comprises; a
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`plurality of ultrasonic sensors for transmitting ultrasonic waves toward a seat and the
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`receiving reflected waves from the seat and its contents, if any; one or more weight
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`sensors for detecting weight of an occupant in the seat or an absence of weight applied
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`onto the seat indicative of a vacant seat; and processor means or an evaluation circuit to
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`which output of the ultrasonic sensors and the weight sensor(s) are inputted and which
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`processes the outputs to evaluate a seated-state based on the outputs. The evaluation
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`circuit may be implemented in hardware as an electronic circuit or in software as a
`computer program.
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`In certain embodiments, a correlation function or state between the output of the
`
`various sensors and the desired result (i.e., seat occupancy identification and
`
`categorization) is determined, e.g., by a neural network that may be implemented in
`hardware as a neural computer or in software as a computer program. The correlation
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`function or state that is determined by employing this neural network may also be
`
`contained in a microcomputer. In this case, the microcomputer can be employed as an
`evaluation circuit. The word circuit herein will be used to mean both an electronic circuit
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`and the functional equivalent implemented on a microcomputer using software.
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`The seated-state detecting unit may further comprise a seat track position
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`detecting sensor. This sensor determines the position of the seat on the seat track in the
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`forward and aft direction. In this case, the evaluation circuit evaluates the seated-state,
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`based on a correlation function obtain from outputs of the ultrasonic sensors, an output of
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`the one or more weight sensors, and an output of the seat track position detecting sensor.
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`With this structure, there is the advantage that the identification between the flat
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`configuration of a detected surface in a state where a passenger is not sitting in the seat
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`and the flat configuration of a detected surface which is detected when a seat is slid
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`backwards by the amount ofthe thickness of a passenger, that is, of identification of
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`whether a passenger seat is vacant or occupied by a passenger, can be reliably performed.
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`Furthermore, the seated-state detecting unit may also comprise a reclining angle
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`detecting sensor, and the evaluation circuit may also evaluate the seated-state based on a
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`correlation firnction obtained from outputs ofthe ultrasonic sensors, an output of the
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`weight sensor(s), and an output ofthe reclining angle detecting sensor. In this case, ifthe
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`tilted angle information of the back portion of the seat is added as evaluation information
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`for the seated-state, identification can be clearly performed between the flat configuration
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`of a surface detected when a passenger is in a slightly slouching state and the
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`configuration of a surface detected when the back portion of a seat is slightly tilted
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`forward and similar difiicult-to-discrirninate cases. This embodiment may even be
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`combined with the output from a seat track position detecting sensor to further enhance
`the evaluation circuit.
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`Moreover, the seated-state detecting unit may firrther comprise a comparison
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`circuit for comparing the output of the weight sensor(s) with a reference value. In this
`case, the evaluation circuit identifies an adult and a child based on the reference value.
`
`Preferably, the seated-state detecting unit comprises: a plurality of ultrasonic
`
`sensors for transmitting ultrasonic waves toward a seat and receiving reflected waves from
`
`the seat; one or more weight sensors for detecting weight of a passenger in the seat; a seat
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`track position detecting sensor; a reclining angle detecting sensor; and a neural network
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`circuit to which outputs of the ultrasonic sensors and the weight sensor(s), an output of
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`the seat track position detecting sensor, and an output of the reclining angle detecting
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`IO
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`sensor are inputted and which evaluates several kinds of seated-states, based on a
`correlation function obtained from the outputs.
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`The kinds of seated-states that can be evaluated and categorized by the neural
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`network include the following categories, among others, (i) a normally seated passenger
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`and a forward facing child seat, (ii) an abnormally seated passenger and a rear facing child
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`seat, and (iii) a vacant seat.
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`The seated—state detecting unit may further comprise a comparison circuit for
`
`comparing the output of the weight sensor(s) with a reference value and a gate circuit to
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`which the evaluation signal and a comparison signal from the comparison circuit are input.
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`This gate circuit, which may be implemented in software or hardware, outputs signals
`which evaluates several kinds of seated-states. These kinds of seated-states can include a
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`(i) normally seated passenger, (ii) a forward facing child seat, (iii) an abnormally seated
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`passenger, (iv) a rear facing child seat, and (v) a vacant seat. With this arrangement, the
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`identification between a normally seated passenger and a forward facing child seat, the
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`identification between an abnormally seated passenger and a rear facing child seat, and the
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`identification of a vacant seat can be more reliably performed.
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`The outputs of the plurality of ultrasonic sensors, the output of the weight
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`sensor(s), the outputs of the seat track position detecting sensor, and the outputs of the
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`reclining angle detecting sensor are inputted to the neural network or other pattern
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`recognition circuit, and the neural network circuit determines the correlation function,
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`based on training thereof during a training phase. The correlation function is then typically
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`implemented in or incorporated into a microcomputer. For the purposes herein, neural
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`network will be used to include both a single neural network, a plurality of neural
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`networks, and other similar pattern recognition circuits or algorithms and combinations
`thereof.
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`To provide the input from the ultrasonic sensors to the neural network circuit, it is
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`preferable that an initial reflected wave portion and a last reflected wave portion are
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`removed from each ofthe reflected waves of the ultrasonic sensors and then the output
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`3O
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`data is processed. The neural network circuit determines the correlation fimction by
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`perfomting a weighting process, based on output data from the plurality of ultrasonic
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`sensors, output data from the weight sensor(s), output data from the seat track position
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`detecting sensor if present, and/or on output data from the reclining angle detecting sensor
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`if present.
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`With this arrangement, the portions of the reflected ultrasonic wave that do not
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`contain useful information are removed from the analysis and the presence and recognition
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`of an object on the passenger seat can be more accurately performed
`
`In the method for determining the occupancy of a seat in a passenger compartment
`
`of a vehicle in accordance with the invention, waves such as ultrasonic waves are
`
`transmitted into the passenger compartment toward the seat, reflected waves from the
`
`passenger compartment are received by a component which then generates an output
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`representative thereof, the weight applied Onto the seat is measured and an output is
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`generated representative thereof and then the seated-state of the seat is evaluated based on
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`the outputs from the sensors and the weight measuring means.
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`The evaluation the seated-state of the seat may be accomplished by generating a
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`function correlating the outputs representative of the received reflected waves and the
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`measured weight and the seated-state of the seat, and incorporating the correlation
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`function into a microcomputer. In the alternative, it is possible to generate a function
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`correlating the outputs representative of the received reflected waves and the measured
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`weight and the seated—state of the seat in a neural network circuit, and execute the
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`function using the outputs representative of the received reflected waves and the measured
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`weight as input into the neural network circuit.
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`To enhance the seated-state determination, the position of a seat track of the seat
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`is measured and an output representative thereof is generated, and then the seated-state of
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`the seat is evaluated based on the outputs representative of the received reflected waves,
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`the measured weight and the measured seat track position. In addition to or instead of
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`measuring the seat track position, it is possible to measure the reclining angle of the seat,
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`i.e., the angle between the seat portion and the back portion of the seat, and generate an
`output representative thereof, and then evaluate the seated-state of the seat based on the
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`outputs representative of the received reflected waves, the measured weight and the
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`measured reclining angle of the seat (and seat track position, if measured).
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`Furthermore, the output representative of the measured weight may be compared
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`with a reference value, and the occupying object of the seat identified, e.g., as an adult or
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`a child, based on the comparison of the measured weight with the reference value.
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`BRIEF DESCRIPTION OF THE DRAWIN S
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`The present invention will be described in fin‘ther detail with reference to the
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`accompanying drawings wherein:
`
`FIG. 1 shows a seated-state detecting unit in accordance with the present invention
`
`and the connections between ultrasonic sensors, 21 weight sensor, a reclining angle
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`10
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`detecting sensor, a seat track position detecting sensor, a neural network circuit, and an
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`airbag system installed within a vehicle compartment;
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`FIG. 2 is a view of a passenger seat in the compartment showing the relative
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`layout of the ultrasonic sensors;
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`FIG. 3 is a circuit diagram of the seated-state detecting unit ofthe present
`invention;
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`FIGS. 4(a), 4(b) and 4(c) are each a diagram showing the configuration of the
`reflected wave of an ultrasonic wave transmitted from each transmitter of the ultrasonic
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`sensors toward the passenger seat, obtained within the time that the reflected wave arrives
`
`at a receiver, FIG. 4(a) showing an example of the reflected waves obtained when a
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`passenger is in a normal seated—state, FIG. 40)) showing an example of the reflected
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`waves obtained when a passenger is in an abnormal seated-state (where the passenger is
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`seated too close to the instrument panel), and FIG. 4(c) showing a transmit pulse;
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`FIG. 5 is a diagram of the data processing of the reflected wave of the ultrasonic
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`wave;
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`FIG. 6 is a flowchart showing the training steps of a neural network circuit;
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`FIG. 7(a) is an explanatory diagram of a process for normalizing the reflected
`wave and shows normalized reflected waves; and
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`FIG. 70)) is a diagram similar to FIG. 7(a) showing a step of extracting data based
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`on the normalized reflected waves and a step of weighting the extracted data by employing
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`
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`the data of the seat track position detecting sensor, the data of the reclining angle
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`detecting sensor, and the data ofthe weight sensor.
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`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`Referring to the accompanying drawings wherein like reference numbers designate
`
`the same or similar elements, FIG. 1 shows a passenger seat 1 to which a seated-state
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`detecting unit according to the present invention may be applied. The passenger seat 1
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`includes a horizontally situated seat portion 2 and a vertically oriented back portion 3.
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`The seat portion 2 is provided with one or more weight sensors 6 which determine the
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`weight of a passenger or object occupying the passenger seat. The coupled portion
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`between the seated portion 2 and the back portion 3 is provided with a reclining angle
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`detecting sensor 9, which detects the tilted angle of the back portion 3 relative to the seat
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`portion 2. The seat portion 2 is provided with a seat track position detecting sensor 10.
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`The seat track position detecting sensor 10 fulfills a role of detecting the quantity of
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`movement of the seat 1 which is moved fi'om a back reference position, indicated by the
`dotted chain line.
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`Weight measuring means such as the sensor 6 are associated with the seat, e.g.,
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`mounted into or below the seat portion 2, for measuring the weight applied onto the seat.
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`The weight may be zero is no occupant is present. Sensor 6 may represent a plurality of
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`difi'erent sensors which measure the weight applied onto the seat at different portions
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`thereof or for redundancy purposes, e.g., such as by means of an airbag 5 in the seat
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`portion 2. Such sensors may be in the form of force or pressure sensors which measure
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`the force or pressure on the seat or seat back, displacement measuring sensors which
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`measure the displacement of the seat surface or the entire seat such as through the use of
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`strain gages mounted on the seat structural members or other appropriate locations, or
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`systems which convert displacement into a pressure wherein a pressure sensor can be used
`as a measure of weight.
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`As shown in FIG. 2, there are provided four sets of ultrasonic sensors 11-14
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`mounted within the passenger compartment. Each set of ultrasonic sensors 11-14
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`comprises a transmitter and a receiver, which may be integrated into a single unit or
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`individual components separated fi'om one another. In this embodiment, the ultrasonic
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`sensor 11 is mounted on the upper portion of the front pillar, A—Pillar, of the vehicle. The
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`ultrasonic sensor 12 is mounted on the upper portion of the intermediate pillar, B-Pillar.
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`The ultrasonic sensor 13 is mounted on the roof ceiling portion or the headliner (FIG. 2).
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`The ultrasonic sensor 14 is mounted near the middle of an instrument panel 17 in front of
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`the driver's seat 16 (FIG, 2). Although sensors 11-14 are described as being ultrasonic
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`sensors, the invention is equally applicable for other types of sensors which emit waves
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`(other than ultrasonic waves) which will reflect from an object and can be received by
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`appropriate receivers and the received waves processed as described below.
`The ultrasonic sensors 11-14 are controlled or driven, one at a time or
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`simultaneously, by an appropriate driver circuit such as ultrasonic sensor driver circuit 18
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`shown in FIG. 3. The transmitters of the ultrasonic sensors 11-14 transmit respective
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`ultrasonic waves toward the passenger seat 1 and transmit pulses (see FIG. 4(c)) in
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`sequence at times t1, t2, t3 and t4 (t4> t3> t2> t1). The reflected waves of the ultrasonic
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`waves are received by the receivers ChA-ChD of the ultrasonic sensors 11-14. The
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`receiver ChA is associated with the ultrasonic sensor 13, the receiver ChB is associated
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`with the ultrasonic sensor 14, the receiver ChD is associated with the ultrasonic sensor 11,
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`’
`and the receiver ChD is associated with the ultrasonic sensor 12.
`FIGS. 4(a) and 4(b) show examples of the reflected ultrasonic waves USRW that
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`are received by receivers ChA—ChD. FIG. 4(a) shows an example of the reflected wave
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`USRW that is obtained when an adult passenger sits in a normally seated space on the
`passenger seat 1, while FIG, 4(b) shows an example of the reflected wave USRW that are
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`obtained when an adult passenger sits in a slouching state (one of the abnormal seated-
`states) in the passenger seat 1.
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`In the case of a normally seated passenger, as shown in FIG. 2, the location of the
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`ultrasonic sensor 12 is closest to the passenger A. Therefore, the reflected wave pulse P1
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`is received earliest afier transmission by the receiver ChD as shown in FIG. 4(a), and the
`width of the reflected wave pulse P1 is larger. Next, the distance from the ultrasonic
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`30
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`sensor 13 is closer to the passenger A, so a reflected wave pulse P2 is received earlier by
`the receiver ChA compared with the remaining reflected wave pulses P3 and P4 . Since
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`the reflected wave pauses P3 and P4 take more time than the reflected wave pulses P1 and
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`P2 to arrive at the receivers ChC and ChB, the reflected wave pulses P3 and P4 are
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`received as the timings shown in FIG. 4(a). More specifically, since it is believed that the
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`distance from the ultrasonic sensor 11 to the passenger A is slightly shorter than the
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`distance from the ultrasonic sensor 14 to the passenger A, the reflected wave pulse P3 is
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`received slightly earlier by the receiver ChC than the reflected wave pulse P4 is received
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`by the receiver ChB,
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`In the case where the passenger A is sitting in a slouching state in the passenger
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`seat 1, the distance between the ultrasonic sensor 11 and the passenger A is shortest.
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`Therefore, the time from transmission at time t3 to reception is shortest, and the reflected
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`wave pulse P3 is received by the receiver ChC, as shown in FIG. 4(b). Next, the distances
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`between the ultrasonic sensor 14 and the passenger A becomes shorter, so the reflected
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`wave pulse P4 is received earlier by the receiver ChB than the remaining reflected wave
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`pulses P2 and P1. When the distance from the ultrasonic sensor 13 to the passenger A is
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`compared with that from the ultrasonic sensor 12 to the passenger A, the distance from
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`the ultrasonic sensor 13 to the passenger A becomes shorter, so the reflected wave pulse
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`P2 is received by the receiver ChA first and the reflected wave pulse P1 is thus received
`last by the receiver ChD.
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`The configurations of the reflected wave pulses P 1-P4, the times that the reflected
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`wave pulses Pl-P4 are received, the sizes of the reflected wave pulses Pl-P4 are varied
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`depending upon the configuration and position of an object such as a passenger situated
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`on the front passenger seat 1‘ Figs 4(a) and (b) merely show examples for the purpose of
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`description and therefore it is a matter of course that the present invention is not limited to
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`these examples.
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`The outputs of the receivers ChA—ChD, as shown in FIG. 3, are input to a band
`pass filter 20 through a multiplex circuit 19 which is switched in synchronization with a
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`timing signal from the ultrasonic sensor drive circuit 18. The band pass filter 20 removes a
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`low frequency wave component fi'om the output signal based on each of the reflected
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`wave USRW and also removes some ofthe noise. The output signal based on each of the
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`reflected wave USRW is passed through the band pass filter 20, then is amplified by an
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`amplifier 21. The amplifier also removes the high frequency carrier wave component in
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`each of the reflected USRW and generates an envelope wave signal. This envelope wave
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`signal is input to an analog/digital converter (ADC) 22 and digitized as measured data.
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`The measured data is input to a processing circuit 28, which is controlled by the timing
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`signal which is in turn output from the ultrasonic sensor drive circuit 18.
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`The processing circuit 23 collects measured data at intervals of 7 ms, and 47 data
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`points are generated for each of the ultrasonic sensors 11-14. For each of these reflected
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`waves USRW, the initial reflected wave portion Tl and the last reflected wave portion T2
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`are cut off. The reason for this will be described when the training procedure of a neural
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`network circuit is described later, and the description is omitted for now. With this, 32
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`data points, 31 data points, 37 data points, and 38 data points will be sampled by the
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`ultrasonic sensors 11, 12, 13 and 14, respectively. The reason why the number of data
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`points differs for each of the ultrasonic sensors 1 1-14 is that the distance fiom the
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`passenger seat 1 to the ultrasonic sensors 11-14 differ from one another.
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`Each of the measured data is input to a normalization circuit 24 and normalized.
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`The normalized measured data is input to the neural network circuit 25 as wave data.
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`The output of the weight sensor(s) 6 is amplified by an amplifier 26 coupled to the
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`weight sensor(s) 6 and the amplified output is input to the analog/digital converter 27.
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`The reclining angle detecting sensor 9 and the seat track position detecting sensor
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`10, which each may comprise a variable resistor, are connected to constant-current
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`circuits, respectively. A constant-current is supplied from the constant-current circuit to
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`the reclining angle detecting sensor 9, and the reclining angle detecting sensor 9 converts a
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`change in the resistance value on the tilt of the back portion 3 to a specific voltage. This
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`output voltage is input to an analog/digital converter 28 as angle data, i.e., representative
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`of the angle between the back portion 3 and the seat portion 2. Similarly, a constant
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`current is supplied from the constant-current circuit to the seat track position detecting
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`sensor 10 and the seat track position detecting sensor 10 converts a change in the
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`resistance value based on the track position ofthe seat portion 2 to a specific voltage. This
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`output voltage is input to an analog/digital converter 29 as seat track data. Thus, the
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`outputs of the reclining angle detecting sensor 9 and the seat track position detecting
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`sensor 10 are input to the analog/digital converters 28 and 29, respectively. Each digital
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`data value from the ADCs 28,29 is input to the neural network circuit 25. Although the
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`digitized data of the weight sensor(s) 6 is input to the neural network circuit 25, the
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`output of the amplifier 26 is also input to a comparison circuit. The comparison circuit,
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`which is incorporated in the gate circuit algorithm, determines whether or not the weight
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`of an object on the passenger seat 1 is more than a predetermined weight, such as 60 lbs.,
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`for example. When the weight is more than 60 lbs, the comparison circuit outputs a logic
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`1 to the gate circuit to be described later. When the weight of the object is less than 60
`
`lbs., a logic 0 is output to the gate circuit.
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`10
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`The neural network circuit 25 recognizes the seated-state of a passenger A by
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`training as described in several books on Neural Networks referenced in the above
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`referenced patents and patent applications. Then after training the seated-state of the
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`
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`passenger A and developing the neural network weights, the system istested The training
`procedure and the test procedure ofthe neural network circuit 251\15:ei’1lhereaiter be
`described With a flowchart shown1n FIG. 6.
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`As diagrammed in FIG. 6, the first step is to mount the four sets of ultrasonic
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`sensors 11-14 , the weight sensor 6, the reclining angle detecting sensor 9, and the seat
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`track position detecting sensor 10 into a vehicle (step S 1). Next, in order to provide data
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`for the neural network circuit 25 to learn the patterns of seated states, data is recorded for
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`patterns of all possible seated states and a list is maintained recording the seated states for
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`which data was acquired. The data from the sensors/transducers 9-14, for a particular
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`occupancy of the passenger seat is called a vector (step S 2).
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`For the vectors of data, adults and children each with different postures, states of
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`windows etc. within the passenger compartment, and child seats were selected. The
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`selected adults include people with a variety of different physiques such as fat, lean, small,
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`large, tall, short, and glasses wearing persons. The selected children ranged from an infant
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`to a large child (for example, about 14 year old). In addition, the selected postures include,
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`for example, a sitting state with legs crossed on a seat, a sitting state with legs on an
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`instrument panel, a sitting state while reading a newspaper, a book, or a map, a sitting
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`state while holding a cup of coffee, a cellular telephone or a dictation machine, and a
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`25
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`30
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`slouching state. Furthermore, the selected compartment states include variations in the
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`seat track position, the window opening amount, headrest position, and varying positions
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`of a sun-visor. Moreover, a multitude‘of different models of child seats are used in the
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`forward facing position and, where appropriate, in a rear facing position. The range of
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`weights and the corresponding normalized values are as follows:
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`Class
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`Empty seat
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`10
`
`Rear Facing Child Seat
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`Forward facing Child Seat
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`Weight Range
`
`Normalized Value
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`0 to 2.2 lbs
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`22 to 60 lbs
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`22 to 60 lbs
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`0 to 001
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`0.01 to 0.27
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`0.01 to 0.27
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`Normal Position Adult
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`601bs and greater
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`.27 to 1
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`
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`25
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`Obviously, other weight ranges may also be used in accordance with the invention and
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`each weight range may be tailored to specific conditions, such as different vehicles.
`Various vehicle setups were prepared by a combination ofthese variations and, for
`
`in this embodiment, almost 100,000 or more vectors should be prepared for the patterns to
`be used as data for the neural network training.
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`Next, based on the training data from the reflected waves of the ultrasonic sensors
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`11-14 and the other sensors, the vector data is collected (step S 3). Next, the reflected
`waves P1-P4 are modified by removing the initial reflected waves with a short reflection
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`time from an object (period T1 in FIG. 5) and the last portion of the reflected waves with
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`a long reflection time from an object (period P2 in FIG, 5) (step S 4). It is believed that
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`the reflected waves with a short reflection time from an object is a due to cross-talk, that
`is, waves from the transmitters which leaks into each of their associated receivers ChA-
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`ChD. It is also believed that the reflected waves with along reflection time are reflected
`waves from an object far away from the passenger seat. Ifthese two reflected wave
`portions are used as data, they will add noise to the training process. Therefore, these
`reflected wave portions are eliminated from the data.
`
`As shown in FIG. 7(a), measured data is normalized by making the peaks ofthe
`reflected wave pulses P1~P4 equal (step S 5). This eliminates the effects of difl‘erent
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`reflectivities of different objects and people depending on the characteristics of their
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`surfaces such as their clothing Data from the weight sensor, seat track position sensor and
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`seat reclining angle sensor are also normalized based typically on fixed normalization
`parameters.
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`Therefore, the normalized data from the ultrasonic transducers the seat track
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`position detecting sensor 10, the reclining angle detecting sensor 9, and from the weight
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`sensor(s) 6 are input to the neural network circuit 25, and the neural network circui