Ulllted States Patent
`
`[19]
`
`[11] Patent Number:
`
`9
`9
`5 474 327
`
`
`Schousek
`[45] Date of Patent:
`Dec. 12, 1995
`
`llilllllllllllIllIlllllllll|||||||||||||||I
`USOO5474327A
`
`[54] VEHICLE OCCUPANT RESTRAINT WITH
`SEAT PRESSURE SENSOR
`
`Attomey, Agent, or Firm—Mark A. Navarre
`
`[75]
`
`Inventor: Theresa J. Schousek, Kokomo, Ind.
`
`[57]
`
`ABSTRACT
`
`E73] AS-Siglleei D9100 Electmflics C0YP0l‘ati011a
`Kokomo lnd.
`’
`
`[21] APPL NM 325,718
`[22] Filed:
`Jan. 10, 1995
`
`Int. Cl.“ ..................................................... B6011 21/32
`[51]
`
`[52] us‘ Cl‘ """"""""
`280,735; 180/268; 280/7301
`58
`Fi ld fS
`h ................................. 280/730.1, 732,
`[
`1
`E
`0
`earn
`230/735; 180,263
`
`[56]
`
`References Cited
`U.S- PATENT DOCUMENTS
`
`............................ 280/735
`5,074,583 12/1991 Fujita et al.
`5,161,820 11/1992 Vollmer
`- 280/730-1
`
`180/268
`5,172,790 12/1992 Ishikawa ct al.
`230,732
`5,232,243
`8/1993 Blackburn et al.
`
`OTHER PUBLICATIONS
`
`Alps Product Brochure (publication date unknown).
`Interlink Product Brochure (publication date unknown).
`
`An air bag restraint system is equipped with seal occupant
`.
`.
`sensing apparatus for a passenger seat which detects both
`infant seats and adults and distinguishes between rear and
`forward facing infant seats. Air bag deployment is inhibited
`when an occupied rear facing infant seat is present. The
`Sensing apparatus comprises eight variable resistance p,.es_
`sure sensor in the seat cushion The response of each sensor
`_
`'
`to occupant pressure is monitored by a microprocessor
`which calculated total weight and weight distribution. The
`weight is used to discriminate between an occupied infant
`seat, an adult and no occupant. The weight distribution is
`
`used to distinguish betwefin forward and rear facing infant
`seats. Another embodiment uses the occupant sensing along
`_
`_
`_
`_
`_
`_
`with seat belt fastening detection to indicate when a seat IS
`occupied and the belt is not fastened.
`
`Primary Examx'ner——Kenneth R. Rice
`
`11 Claimsv 4 Drawing Sheets
`
`INDICATOR
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`132
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` A
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`——I
`——I
`D—I
`I-I
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`CONTROL
`CIRCUIT
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`130
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`1
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`KMA-1 004
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`1
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`KMA-1004
`
`

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`U.S. Patent
`
`Dec. 12,1995
`
`Sheet 1 of4
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`5,474,327
`
`14
`ACCELEROMETEFI
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`20
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`\
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`FAULT INDICATOR
`18
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`DEPLOYMENT
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`S AIR BAG
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`0
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`5
`3
`5
`E
`5
`2
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`%
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`
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`Q
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`so 28
`ITIWVJ
`a r
`‘
`DECISION’
`5
`3
`3 mm:
`E
`30
`28
`_
`O
`8
`3°
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`+5V
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`24
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`26
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`.
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`25 .
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`'
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`2“
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`132
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`INDICATOR _
`
` CONTROL iii
`CIRCUIT %:
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`130
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`2
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`

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`U.S. Patent
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`Dec. 12, 1995
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`Sheet 2 of 4
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`5,474,327
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`3
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`

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`Patent
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`Dec. 12, 1995
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`Sheet 3 of 4
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`5,474,327
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`60
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`62
`
`FIG - 5A
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`
`
`LESS
`THAN ONE
`
`SECOND
`
`NO
`
`SAMPLE EACH SENSOR
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`54
`
`. 66
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`FORCE = CALIBRATION — SAMPLE
`
`CALCULATE TOTAL WEIGHT PARAMETER
`
`68
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`CALCULATE CENTER OF WEIGHT
`
`70
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`74
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`‘ADULT DETECTED
`.
`DEPLOY DECISION
`
`
`IS
`
`
`TOTAL WE'GHT>
`MAX INFANT SEAT
`THRE§HoLD
`
`
`
`
`
`
`72
`
`76
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`8 I
`
`
`
`
`
`
`TOTAL IIIISEIGHT‘
`
`w~=~-~Tsw
`THRE§HOLD
`
`
`
`* SEAT EMPTY
`NOT DEPLOY DECISION
`
`INFANT SEAT OR
`SMALL CHILD
`D ETECTED
`
`
`IS
`
`CENTER OF
`
`' REARWARD FACING
`WEIGHT FORWARD OF
`INFANT SEAT DETECTED
`CALIBRATED
`
`" NOT DEPLOY DECISION
`REFERENCE
`LINE ?
`
`
`
`
`
`
` ' FORWARD FACING
`INFANT SEAT DETECTED
`
`' DEPLOY DECISION
`
`
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`4
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`

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`U.S. Patent
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`Dec. 12, 1995
`
`Sheet 4 of 4
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`5,474,327
`
` 90
`
`STORE DECISION IN ARRAY
`
`FIG - 5B
`
`94
`
`
`
`
`
`HAVE
`LESS THAN
`5 DECISIONS BEEN
`STOORED
`
`
`
`INCREMENT DECISION COUNTER
`
`
`
`CLEAR DECISION COUNTER
`
`96
`
`
`
`
`
`
` TRANSMIT PREVIOUS DECISION
`
`
`TRANSMIT DECISION TO
`SIR MODULE
`
`10
`
`2
`
`CURRENT DECISION IS NOW
`THE PREVIOUS DECISION
`
`104
`
`ARE ALL 5
`DECISIONS THE
`SAME
`
`
`
`TO SIR MODULE
`
`CLEAR FAULTY DECISION
`CENTER
`
`INCREMENT FAULTY DECISION COUNTER
`
`
`
`IS
`FACULTY
`DECISION COUNTER
`> MAX ALLOWED UNSTABLE
`READINGS
`
`
`
`TRANSMIT FAULT TO
`SIR MODULE
`
`
`COUNTER
`
`
`CLEAR FAULTY DECISION
`
`
`
`RETURN
`
`5
`
`

`
`1
`VEHICLE OCCUPANT RESTRAINT WITH
`SEAT PRESSURE SENSOR
`
`FIELD OF THE INVENTION
`
`This invention relates to occupant restraints for vehicles
`and particularly to a restraint system having seat sensors to
`identify adult and infant seat occupancy.
`
`BACKGROUND OF THE INVENTION
`
`The expanding use of supplemental inflatable restraints
`(SIRs) or air bags for occupant protection in vehicles
`increasingly involves equipment for the front outboard pas-
`senger seat. The driver side air bag has been deployed
`whenever an imminent crash is sensed. The position and size
`of the driver is fairly predictable so that such deployment
`can advantageously interact with the driver upon a crash.
`The passenger seat, however, may be occupied by a large or
`a small occupant including a baby in an infant seat. It can not
`be assumed that a passenger of any size is at an optimum
`position (leaning against or near the seat back). An infant
`seat is normally used in a rear facing position for small
`babies and in a forward facing position for larger babies and
`small children. While the forward facing position approxi-
`mates the preferred position for air bag interaction, the rear
`facing position places the top portion of the infant seat close
`to the vehicle panel which houses the passenger side air bag.
`In the latter event, it may be desirable to prevent deployment
`of the air bag. Similarly, if a passenger in the seat is leaning
`forward, it may be desirable to prevent air bag deployment.
`It has been proposed to use a magnet or other special
`attachment on an infant seat and a special sensor in the seat
`or panelboard which detects the attachment and allows
`determination that an infant seat is present and is positioned
`in a pa.rticular way. Of course that arrangement is operable
`only with the specially equipped infant seats; other infant
`seats and passengers are not serviced. A separate sensing
`system would have to be employed to detect the position or
`presence of small children or adults.
`Seat belt restraint systems can also benefit by information
`about the presence of passengers. For example, by monitor-
`ing which belts are buckled and which seats are occupied, a
`warning display can inform the driver that some seat or a
`particular seat is occupied and the belt is not utilized. Where
`an infant seat is in a vehicle seat and the infant seat is
`occupied, this seat also should be belted in and the warning
`system employed to detect a failure to meet this condition.
`
`SUMMARY OF THE INVENTION
`
`It is therefore an object of the invention to detect a full
`range of vehicle passengers including occupied infant seats
`supported on a vehicle seat. Another object is to detect such
`passengers and to discriminate between rear facing and front
`facing infant seats. Another object is to control a restraint
`system in accordance with information developed by detect-
`ing the presence of occupants and the positions of occupants.
`A SIR system, as is well known, has an acceleration
`sensor to detect an impending crash, a rnicro-controller to
`process the sensor signal and to decide whether to deploy an
`air bag, and a deployment unit fired by the rniero-controller.
`An occupant detection system can determine if an occupant
`or infant seat is positioned in a way to not benefit from
`deployment,
`and then signalling the micro-controller
`whether to allow deploying the air bag.
`
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`A large array of many hundreds of pressure sensors in or
`on a vehicle seat cushion can reveal a pressure profile which
`is distinctive for each type of seat occupant and can also
`measure the weight of the occupant. An adult has one kind
`of profile, a front facing infant seat has another, and a rear
`facing infant seat has still another. These profiles indicate
`that the “center of gravity” or center of weight distribution
`is distinctive for each of these three conditions. Such an
`array of sensors, however, is very expensive and the elec-
`tronic equipment for servicing the array and analyzing the
`pressure information is also expensive.
`It has been found, however, that a very small number of
`sensors, judicially located in the seat, can gamer sufiicient
`pressure and distribution information to allow determination
`of the occupant type and infant seat position. This informa-
`tion, in turn, can be used as desired to inhibit SIR deploy-
`ment. Two sets of four sensors symmetrically arranged on
`either side of a seat centerline are adequate to gather the
`pressure data. In each set, two sensors are situated near the
`eenterline and near the back of the seat cushion, the other
`two are further forward and outboard, one on the wing of the
`cushion and the other just inboard of the wing. Each sensor
`is a very thin resistive device, having lower resistance as
`pressure increases. A microprocessor is programmed to
`sample each sensor, determine a total weight parameter by
`summing the pressures registered by the several sensors, and
`determine the center of weight distribution from the sum of
`the products of each sensed pressure and its distance from
`the rear of the seat, and dividing the product by the total
`weight.
`Based on the minimum weight of an occupied infant seat
`(about 10 pounds) and the maximum weight of an occupied
`infant seat (50 pounds), maximum and minimum thresholds
`are calibrated, and those are compared to the measured total
`weight parameter to determine whether the vehicle seat is
`holding an occupied infant seat, a larger person, or has no
`occupant. The center of weight distribution is used to
`determine the position of an infant seat, a rear facing seat
`having a weight center much further forward than a forward
`facing seat. Given the occupant information, it can then be
`decided whether to deploy the air bag during a crash. The
`decision depends on the desired results which may be
`dictated by the legal requirements where the vehicle is
`operated. Typically, the air bag deployment will be pre-
`vented at least in the case of an occupied rear facing infant
`seat.
`
`A sampling of the sensors and a deployment decision is
`made periodically, say each second, and the system is
`monitored for failure by testing consistency of the decisions.
`If five consecutive decisions are the same, that decision is
`validated and signalled to the SIR microcontrollerg if the five
`decisions are not the same, a failure is registered and the
`previous validated decision is maintained. In any event, a
`signal to enable or disable deployment is issued every five
`seconds. However the failures are counted and if a large
`number of failures occur, a failure signal is sent to the
`micro-controller.
`
`Another use of the seat pressure profile sensor in a
`restraint system is for a seat belt warning indicator to advise
`the vehicle operator whether any seat is occupied either by
`a baby in an infant seat or by a larger person, and the seat
`belt for that seat is not fastened.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above and other advantages of the invention will
`become more apparent from the following description taken
`
`6
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`
`5,474,327
`
`3
`
`in conjunction with the accompanying drawings wherein
`like references refer to like parts and wherein:
`FIG. 1 is a schematic diagram of a SIR system and an
`associated seat sensor system according to the invention;
`FIG. 2 is a top view of a vehicle seat cushion having
`pressure sensors positioned on the seat, according to the
`invention;
`FIG. 3 is an outline elevational view of a vehicle seat
`containing a rear facing infant seat illustrating an application
`of the invention;
`FIG. 4 is an outline elevational view of a vehicle seat
`containing a forward facing infant seat illustrating an appli-
`cation of the invention;
`
`FIGS. 5a, Sb and, in combination, comprise a flow chart
`representing a computer program for seat occupant detection
`and SIR control according to the invention; and
`FIG. 6 is a schematic diagram of a seat pressure sensor
`and seat belt system according to another embodiment of the
`invention.
`
`DESCRIPTION OF THE INVENTION
`
`Referring to FIG. 1, a SIR system includes a SIR module
`10 coupled to a seat occupant sensing system 12. The SIR
`module 10 includes an accelerometer 14 mounted on the
`vehicle body for sensing an impending crash, a micropro-
`cessor 16 for receiving a signal from the accelerometer and
`for deciding whether to deploy an air bag. An air bag
`deployment unit 18 is controlled by the microprocessor 16
`and fires a pyrotechnic or compressed gas device to inflate
`an air bag when a deploy command is received. A fault
`indicator 20, also controlled by the microprocessor 16 will
`show a failure of the seat occupant sensing system 12.
`The seat occupant sensing system 12 comprises a micro-
`processor 22 having a 5 volt supply and an enabling line 24
`periodically provided with a 5 volt enabling pulse, and a
`series of voltage dividers coupled between the enabling line
`24 and ground. Each voltage divider has a fixed resistor 26
`in series with a pressure sensor or variable resistor 28, and
`the junction point of each resistor 26 and variable resistor 28
`is connected to an AID port 30 of the microprocessor 22. The
`microprocessor 22 controls the pulse on enabling line 24 and
`reads each sensor 28 voltage during the pulse period. The
`microprocessor 22 analyzes the sensor inputs and issues a
`decision whether to inhibit air bag deployment and the
`decision is coupled to the microprocessor 16 by a line 32.
`The microprocessor 22 also monitors its decisions for con-
`sistency and issues a fault signal on line 34 to the micro-
`processor 16 if faults continue to occur over a long period.
`Each fixed resistor 26 is, for example, 17.4 kohms and the
`variable resistors vary between 2 kohms at high pressure and
`174 kohms at low pressure. Then the voltage applied to the
`ports 30 will vary with pressure from about 4.6 volts to 0.5
`volts. Each sensor is mounted between polymer film sheets
`and includes a pair of conductive electrodes about one inch
`in diameter separated by carbon layers such that the resis-
`tance between electrodes decreases as pressure increases.
`Such sensors are available as UniForce (TM) sensors from
`Force Imaging Technologies, Inc., Chicago, Ill. To minimize
`any deteriorating eifects of current through the sensors, short
`enabling pulses of 1 ms are applied once each second.
`The mounting arrangement of sensors 28 on a bottom
`bucket seat cushion 36 with lateral wings 37 is shown in
`FIG. 2. A first set 38 of four sensors 28 mounted on a
`common flexible circuit substrate 40 is located on the right
`
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`side of a seat center line and a second set 42 is symmetrically
`disposed on the left side of the center line. In each set, a
`sensor at position A is close to the centerline and near the
`back of the cushion, a sensor at position B is outboard of
`position A and further back. A third sensor 28 at position C
`is forward of position A and near the wing 37, and a fourth
`sensor at position D is on the wing 37 and forward of
`position C. Although weight distribution of an occupant may
`be assumed to be approximately balanced between left and
`right sides of the seat, having sensors on both sides of the
`seat allows good data collection and measurement of total
`weight and distribution in the event of unbalance. Weight
`distribution is centered somewhere within the confines of the
`sensor grouping and is calculated with reference to an
`arbitrary datum line 44 extending transversely of the seat.
`The particular center of weight distribution is determined by
`calculating the product of each measured sensor response
`and the sensor distance SD from the datum line 44, summing
`the products, and dividing the sum by the total of all the
`measured weights. In practice, it is found that the center of
`weight varies greatly depending on the type of occupant and
`whether an infant seat faces forward or rearward.
`
`In FIG. 3, a vehicle seat 46 having a bottom cushion 36
`instrumented according to the arrangement of FIG. 2, sup-
`ports an infant seat 48 facing to the rear, which is the
`preferred position for small babies. Seat belts for securing
`the infant seat are not shown. The top or head portion 50 of
`the infant seat 48 extends toward the front of the passenger
`compartment and is spaced from the vehicle instrument
`panel 52. FIG. 4 shows the same infant seat 48 facing
`forward and the head portion leans against the seat back. It
`is apparent by comparison of the FIGS. 3 and 4 that the
`center of gravity of the rear facing infant seat is much further
`forward than the forward facing seat, and experimental data
`supports that conclusion. Adult occupants, when seated
`normally, have a center of gravity near the rear of the seat.
`The seat pressure sensor locations are selected to detect
`the difference of center of gravity of the rear and forward
`facing infant seats. In FIG. 2 the positions A and B mainly
`reflect the adult occupant presence and the positions C and
`D mainly reflect the infant seat presence. While the sensors
`are localized and do not actually weigh the whole person or
`infant seat,
`they can measure weight parameters which
`together represent the total weight and can be empirically
`related to the total weight, and in the same way the center of
`weight distribution calculations can approximate the real
`center of gravity positions well enough to clearly distinguish
`between forward and rear facing infant seats.
`The sensors are preferably located just beneath the seat
`cover and some pressure is exerted on the sensors by the seat
`cover. At the time of vehicle manufacture, the sensors are
`calibrated by measuring each sensor voltage for an empty
`seat condition and those calibration voltages are stored.
`When weight measurements are made by a particular sensor,
`the current voltage is read and subtracted from the calibra-
`tion voltage. The difference voltage then is a function of the
`pressure exerted on the sensor and is empirically related to
`actual occupant weight. That is, the sum of measured voltage
`difierences is a weight parameter which represents occupant
`weight and the value of that sum is empirically determined
`for critical threshold values which are used in determining
`the occupant type. These values are, for example, 50 pounds
`for the maximum weight of an occupied infant seat, and 10
`pounds for the minimum weight of an occupied infant seat,
`allowing a range of 5 to 10 pounds for seat weight and a
`range of 5 to 40 pounds for baby weight. Thus by selecting
`voltage values for these two thresholds a distinction can be
`
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`made among empty seat, occupied infant seat and a larger
`seated occupant. The maximum and minimum threshold
`values are stored in the microprocessor 22.
`The calculated weight center or weight distribution
`parameter made by summing the products of the sensor
`outputs and their distance from a datum line, and dividing
`the sum by the total weight parameter yields a first set of
`results for a rear facing infant seat and a second set for a
`front facing infant seat. These two sets are on opposite sides
`of an imaginary transverse reference line; the results for rear
`facing seats are in front of the line and the results for forward
`facing seats are behind the reference line. The distance data
`for each sensor is stored in the microprocessor 22 which
`makes the calculation, and the position of the imaginary
`reference line is also stored there for comparison with the
`calculated weight distribution parameter.
`The microprocessor 22 is programmed to issue enabling
`pulses on line 24, read each sensor during each pulse, make *
`a decision whether to allow deployment, monitor the deci-
`sions for a fault, and output the decision and fault__results to
`the SIR microprocessor 16. The flow chart of FIGS. 5a, 5b
`and represents the program. Reference numerals shown
`herein in angle brackets <nn> refer to functions described in
`flow chart boxes bearing those numerals. At the beginning of
`the program a timer is initialized <60> and the program is
`delayed <62> until one second has elapsed in order to limit
`the program execution to once per second. Then the sensors
`are enabled and each sensor sampled <64>. The sampled
`voltage is subtracted from the sensor calibration voltage to
`determine a force for each sensor <66> and they are summed
`to obtain a total force or weight parameter <68>. Then a
`center of force or weight "distribution is made <70>. If the
`total weight parameter is greater than the maximum infant
`seat weight <72> this indicates that a larger occupant is
`present and a decision is made to allow deployment <74>.
`Otherwise, if the total weight parameter is less than the
`minimum weight threshold for an occupied infant seat <'76>
`it is determined that the seat is empty and a decision is made
`to inhibit deployment <18>. The same result could be
`obtained if a child or larger occupant in the seat is out of
`position, i.e., leaning forward; then it still is desirable to
`inhibit deployment. If the total weight parameter is between
`the threshold the occupant is identified as an occupied infant
`seat or a small child <80>. If the center of weight distribu-
`tion is forward of the reference line <82> a rear facing infant
`seat is detected and a decision to inhibit deployment is made
`<84>. If the center of weight distribution is not forward of
`the reference line, a forward facing infant seat is detected
`and a decision is made to allow deployment of the air bag
`<86>.
`
`40
`
`45
`
`50
`
`The portion of the how chart shown in FIG. 5b is directed
`to detecting a fault by monitoring the consistency of the
`decisions. The decision made in each loop execution is
`stored in an array <90> and if less than five decisions have
`been stored <92> a decision counter is incremented <94>. If
`the counter reaches a count of five, the counter is cleared
`<96>- and the decisions are compared to determine if they are
`all the same <98>. If they are the same, the current decision
`is transmitted to the SIR module 10 <lO0>, the current
`decision is labelled as the previous decision <l02>, and a
`faulty decision counter is cleared <lO4>. If all five decisions
`are not the same, the previous decision is retransmitted to the
`module 10 <l06> and the faulty decision counter is incre-
`mented <l08>. If a large number of consecutive faulty
`decisions occur <1 10> a fault signal is transmitted to the SIR
`module 10 <ll2> and the faulty decision counter is cleared
`<ll4>. The maximum allowed number of unstable readings
`
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`6
`may, for example, amount to one half hour of operation.
`With this program the decision to allow deployment is
`updated every five seconds, and an occasional spurious
`decision, which may be due to occupant movement or other
`instability, is filtered out. Extended instability triggers the
`fault signal which results in energizing the fault indicator 20.
`It is thus seen that a relatively simple seat pressure sensor
`along with a logical decision program can provide a sub-
`stantial amount of information about the nature of a pas-
`senger seat occupant, if any, and a reliable decision whether ‘
`to inhibit air bag deployment. It is expected that this system
`be limited to a passenger seat subject to SIR protection.
`Referring to FIG. 6, a seat belt monitoring system pro-
`vides belt usage information to the driver for each passenger
`seat so that the driver can enforce a requirement that each
`passenger’s seat belt be fastened. Thus it is desirable to
`determine whether a seat is occupied and to generate a
`warning signal only if an occupied seat has an unfastened
`belt. Each passenger seat position for front and rear seats
`120 is equipped with a seat sensor 122 of the type shown in
`FIG. 2. Seat belts 124 for each position each have a seat belt
`detector 126 which signals that a belt is not fastened. Signal
`lines 128 from the sensors 122 and detectors 126 connect
`with a control circuit 130 which can determine whether a
`seat is occupied and the corresponding belt is unfastened,
`and if so to activate an indicator 132 which informs the
`driver of non-compliance. In the case of infant seats only the
`weight measurement is needed to determine whether a seat
`is occupied, the position of the infant seat being irrelevant.
`The control circuit 130 then should contain a microprocessor
`programmed with steps 60 through 80 of FIG. 5a to deter-
`mine if a seat is empty or -occupied, the program being
`separately executed for each seat sensor 122, and additional
`logic to determined whether an occupied seat correlates with
`an unfastened belt.
`The embodiments of the invention in which an exclusive
`property or privilege is claimed are defined as follows:
`1. In a vehicle occupant restraint system sensitive to the
`occupancy of a vehicle seat by an adult and an occupied
`infant seat and to the position of an infant seat including
`pressure sensors strategically located in the vehicle seat for
`response to the adult occupants and of infant seats, the
`method of controlling air bag deployment comprising the
`steps of:
`measuring a pressure response of each sensor;
`calculating a total occupant weight;
`calculating a weight distribution parameter;
`distinguishing between adult and occupied infant seat
`presence on the basis of total occupant weight;
`distinguishing between forward facing and rear facing
`infant seats on the basis of the weight distribution
`parameter; and
`determining whether to inhibit deployment on the basis of
`adult presence, and on presence and position of an
`infant seat.
`2. The invention as defined in claim 1, wherein the weight
`distribution parameter represents a fore and aft position on
`the vehicle seat, and wherein the step of distinguishing
`between forward facing and rear facing infant seats on the
`basis of the weight distribution parameter includes:
`establishing a reference line relative to the sensors which
`divides a forward weight distribution indicative of a
`rear facing infant seat from a rear weight distribution
`indicative of a front facing infant seat; and
`determining the infant seat position from the weight
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`distribution parameter and the reference line.
`3. The invention as defined in claim 1 wherein the step of
`calculating a weight distribution parameter comprises:
`establishing a datum line extending transverse of the seat;
`multiplying the pressure response of each sensor by the
`distance of the sensor from the datum line to obtain a
`product; and
`dividing the sum of the products by the total weight.
`4. The invention as defined in claim 1 wherein the step of
`determining whether to inhibit deployment includes a deci-
`sion to allow deployment in the case of adult presence or a
`forward facing infant seat, and to inhibit deployment in the
`case of a rear facing infant seat.
`5. In a vehicle occupant restraint system sensitive to the
`occupancy of a vehicle seat by an adult and an occupied
`infant seat including pressure sensors strategically located in
`the vehicle seat for response to adult occupants and to infant
`seats, the method of detecting infant and adult presence
`comprising the steps of:
`establishing a maximum response threshold and a mini-
`mum response threshold for occupied infant seats;
`measuring a pressure response of each sensor;
`calculating an occupant weight parameter from measured
`pressure responses;
`distingiishing between adult presence and an occupied
`infant seat on the basis of the occupant weight pararn-
`eter and the maximum response threshold; and
`distinguishing between an occupied infant seat and no
`occupant on the basis of the occupant weight parameter
`and the minimum response threshold.
`6. The invention as defined in claim 5 wherein the
`occupant restraint system is an SIR system and the method
`includes inhibiting air bag deployment including the steps
`of:
`
`determining from the pressure responses of the sensors
`whether an infant seat is rear facing or forward facing;
`and
`
`inhibiting deployment when an occupied rear facing
`infant seat is detected.
`7. The invention as defined in claim 6 wherein the step of
`determining from the pressure responses of the sensors
`whether an infant seat is rear facing or forward facing
`comprises the steps of:
`calculating a weight distribution parameter from the pres-
`sure response of each sensor and the position of each
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`sensor; and
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`discriminating between front and rear facing infant seats
`on the basis of the weight distribution parameter.
`8. The invention as defined in claim 5 wherein the
`
`occupant restraint system is a seat belt system having
`detectors for seat belt engagement, and the method includes
`indication of seat belt usage comprising the steps of:
`determining whether a seat is occupied;
`detecting that a seat belt is not fastened; and
`indicating when a seat is determined to be occupied and
`its corresponding seat belt is not fastened.
`9. A vehicle occupant restraint system sensitive to the
`occupancy of a vehicle seat by an adult and an occupied
`infant seat including:
`an array of pressure sensors located on a vehicle seat to
`respond to the weight of an adult occupant and of an
`occupied infant seat;
`means for sampling each sensor to determine a plurality
`of weight parameters; and
`means for comparing aggregate weight parameters to first
`and second thresholds to detemiine adult presence,
`occupied infant seat presence, and no occupant.
`10. The invention as defined in claim 9 further including:
`control means for deploying an air bag;
`means for detennining weight distribution from the
`weight parameters; and
`means for withholding air bag deployment when the
`weight distribution is centered toward the front of the
`sensor array and for allowing air bag deployment when
`the weight distribution is toward the rear of the sensor
`array.
`11. The invention as defined in claim 9 wherein the weight
`distribution of a rear facing infant seat is forward of the
`weight distribution of a front facing infant seat, the system
`including:
`control means for deploying an air bag;
`means for detennining weight distribution from the
`weight parameters;
`means for detemiining from the weight distribution
`whether an rear facing infant seat is present; and
`means for withholding air bag deployment when a rear
`facing infant seat is present.
`*
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