‘
`
`.
`
`USOOS732375A
`
`Umted States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,732,375
`
`
`Cashler
`[45] Date of Patent:
`Mar. 24, 1998
`
`[54] METHOD OF INHIBITING OR ALLOWING
`AIRBAG DEPLOYMENT
`
`[75]
`
`Inventor: Robert John Cashler, Kokomo, Ind.
`
`[73] ASSlgl‘lCE! D8100 Electronics Corp, KOkOIDO. Ind.
`
`[21] App1' N0”: 566’029
`
`[22] Filed:
`
`Dec. 1, 1995
`
`Int. CI.6 ............................. B60R 21/32; GOGF 17/40
`[51]
`[52] us. C1.
`.............................. 701/45; 701/46; 130/273;
`280/735
`[53] Field of Search ..................... 364/424.055. 424.056.
`
`364/424.05 ~ 5
`. 568: 130/271, 232. 268,
`273. 307/151“; 340/436, 433; 280/735.
`’
`73001. 730.02
`'
`
`[55]
`
`RefeIeHCes Cited
`
`U-S' PATENT DOCUMENTS
`
`4,1991 Kiko et a]. "
`73/862042
`
`. 230/730,]
`11/1991 VoIlmer
`
`3/1993 Blackburn et
`230/732
`
`.........
`1/1995 Arakiet a1.
`364/557
`10/1995 Mazur et a1.
`........................... 230/735
`
`5,010 774
`5461:1320
`5,232,243
`5,384,716
`5,454,591
`
`5,474,327
`5,494,311
`5,570,301
`5,570,903
`5,605,348
`5,612,376
`
`12/1995 Schousek ................................ 180/268
`2/1996 Blackburn et a1.
`. 280/735
`
`. 364/559
`10/1996 Barrus ............
`
`.. 280/735
`11/1996 Master at a].
`2/1997 Blackburn et a1.
`280/735
`3/1997 Zeidler et a1.
`................... 364/424.055
`OTHER PUBLICATIONS
`
`Research Disclosure—Jan. 1994 #357—“Method for Sens-
`
`ing Occupant Mass and Position." Disclosed Anonymously.
`
`Primary Emminer—Tan Q- Nguyen
`Am’my' 1433"" 0’ an—Mark A- Navarre
`[57]
`ABSTRACT
`
`.
`An array of pressure sensors on a vehicle passenger seat
`senses the presence of an occupant including an infant seat
`and determines whether the infant seat faces forward or
`rearward. A microprocessor coupled to the sensors deter-
`mines whether to allow or inhibit deployment based on the
`sensor load forces and the pattern of loading. The pattern can
`identify an infant seat and pattern and loading determine its
`orientation. Local areas are checked to detect child occu-
`pants. Fuzzy logic is used to determine loading and to
`recognize patterns.
`
`19 Claims, 4 Drawing Sheets
`
`42
`
`so
`
`53
`
`RAILS DETECTED
`
`YES
`
`No
`
`LO
`
`HI
`
`TOTAL FORCE
`
`LOCALIZED FORCE
`AND FLAG
`
`H'
`
`HI
`
`
`
`FRONT FORCE & ALL FRONT FLAG
`
`LEFT FORCE & ALL LEFT FLAG
`
`RIGHT FORCE 5. ALL RIGHT FLAG
`
`HI
`
`HI
`
`HI
`
`“W."
`62
`
`INFANT SEAT TYPE
`
`REAR
`
`74
`
`75
`
`78
`
`
`
`I HEARFORCE&ALLREARFLAG
`
`CENTER GROUP FORCE
`
`HI
`
`TOTAL FUZZY VALUE
`
`84
`
`_\
`
`HN-1001
`
`1
`
`HN-1001
`
`

`

`US. Patent
`
`Mar. 24, 1998
`
`Sheet 1 of 4
`
`5,732,375
`
`FIG - 1
`
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`
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`
`16
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`”J
`
`FIG - 2
`
`51015 20 25 30 3540 45
`
`
`
`2
`
`

`

`US. Patent
`
`Mar. 24, 1998
`
`Sheet 2 of 4
`
`5,732,375
`
`ow
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`

`

`US. Patent
`
`Mar. 24, 1998
`
`Sheet 3 of 4
`
`5,732,375
`
`FORCEOHLOAD
`FUZZY
`CONTWBUUON
`
`
`
`-
`FIG 5
`
`b‘
`
`0
`
`5:55.50
`
`LOADFUUWNG
`
`FIG - 6
`
`d
`
`LOAD
`
`1O 15 20 25 30 35 40 45
`5
`/—-—-___.____._-——__.——_~.—-——
`
`FIG-7
`
`FIG-9
`
`62
`
`
`
`TOTAL
`
`66
`
`
`
`
`YES
`was“
`
`
`
`INHIBIT
`
`FRONT PAIR LOADED
`AND TOTAL FORCE > Y
`
`
`
`
`
`
`4
`
`

`

`US. Patent
`
`Mar. 24, 1993
`
`Sheet 4 0f 4
`
`5,732,375
`
`60
`
`68
`
`RAILS DETECTED
`
`NO
`
`HI
`
`TOTAL FORCE
`
`42
`
`YES
`
`L0
`
`FORWARD
`w
`
`INFANT SEAT TYPE
`
`:
`
`62
`
`REAR
`
`ALLOW
`
`
`.-
`
`
`
`
`h_
`
`
`
`
`
`
`
`
`e
`
`TOTAL FUZZY VALUE
`
`INHIBIT
`
`FIG - 3
`
`5
`
`

`

`1
`METHOD OF INHIBITING 0R ALLOWING
`AIRBAG DEPLOYMENT
`
`5 ,732,375
`
`2
`
`FIELD OF THE INVENTION
`
`This invention relates to occupant restraints for vehicles
`and particularly to a method using seat sensors to determine
`seat occupancy for control of airbag deployment.
`
`BACKGROUND OF THE INVENTION
`
`The expanding use of supplemental inflatable restraints
`(SIRS) or airbags for occupant protection in vehicles increas-
`ingly involves equipment for the front outboard passenger
`seat. The driver side airbag has been deployed whenever an
`imminent crash is sensed The position and size of the driver
`is fairly predictable so that such deployment can advanta-
`geously 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 airbag interaction, the rear
`facing position places the top portion of the infant seat close
`to the vehicle dash which houses the airbag. In the latter
`event. it is desirable to prevent deployment of the airbag.
`It has been proposed in US. Pat. No. 5,474,327 which
`will issue Dec. 12, 1995, entitled VEHICLE OCCUPANI‘
`RESTRAINT WITH SEAT PRESSURE SENSOR and
`assigned to the assignee of this invention, to incorporate
`pressure sensors in the passenger seat and monitor the
`response of the sensors by a microprocessor to evaluate the
`weight distribution and determine the type of occupant and
`the facing direction of an infant seat. The sensor arrange—
`ment and the algorithm successfully cover most cases of seat
`occupancy. It is desirable, however, to encompass every case
`of seat occupancy.
`
`SUMMARY OF THE INVENTION
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`It is therefore an object of the invention to detect a
`comprehensive range of vehicle seat occupants including
`infant seats for a determination of whether an airbag deploy-
`ment should be permitted. Another object in such a system
`is to determine whether an infant seat is facing the front or
`the rear. Another object is to include sensitivity to the
`possible seating positions of small children.
`A SIR system, as is well known, has an acceleration
`sensor to detect an impending crash, a microprocessor to
`process the sensor signal and to decide whether to deploy an
`airbag, and a deployment unit fired by the microprocessor.
`An occupant detection system can determine if an occupant
`or infant seat is positioned in a way to not benefit from
`deployment. and then signaling the microprocessor whether
`to allow or inhibit deploying the airbag.
`A dozen sensors, judicially located in the seat, can garner
`sufficient pressure and distribution information to allow
`determination of the occupant type and infant seat position.
`This information, in turn, can be used as desired to inhibit
`SIR deployment. The sensors are arranged symmetrically
`about the seat centerline and includes a front pair, a right
`pair, a rear pair, a left pair and four in the center. Each sensor
`is a very thin resistive device, having lower resistance as
`pressure increases. A microprocessor is programmed to
`
`45
`
`50
`
`55
`
`65
`
`sample each sensor, determine a total weight parameter by
`summing the pressures, and determine the pattern of pres-
`sure distribution by evaluating local groups of sensors.
`Total force is sufficient for proper detection of adults in
`the seat, but
`the pattern recognition provides improved
`detection of small children and infant seats. To detect infant
`
`seats, all patterns of sensor loading which correspond to the
`imprints of various seats are stored in a table and the
`detected sensor pattern is compared to the table entries.
`Front and rear facing seats are discriminated on the basis of
`total force and the loading of sensors in the front of the seat.
`The pattern recognition for detecting children is made
`possible by applying fuzzy logic concepts to the pressure
`readings for each sensor in the array and assigning a load
`rating to each sensor. Pattern recognitionis also enhanced by
`sampling several pairs of sensors, applying leveling tech—
`nique to them, and computing a measure for the area of the
`seat covered by each pair. For all measures calculated within
`the algorithm. a contribution is made to an overall fuzzy
`rating which is used to handle marginal cases.
`
`BRIEF DESCRlPTION OF THE DRAWINGS
`
`The above and other advantages of the invention will
`become more apparent from the following description taken
`in conjunction with the accompanying drawings wherein
`like references refer to like parts and wherein:
`FIG. 1 is a schematic diagram of an SIR system incor-
`porating a seat occupant detector;
`FIG. 2 is a position diagram of seat sensors for the system
`of FIG. 1. according to the invention;
`FIG. 3 is a flow chart representing an overview of an
`algorithm for determining deployment permission according
`to the invention;
`FIG. 4 is a flow chart representing a method of computing
`decision measures used in the algorithm of FIG. 3;
`FIG. 5 is a graphical representation of a function used in
`fuzzy logic for total force and load ratings;
`FIG. 6 is a graphical representation of a function used in
`fuzzy logic for determining load rating;
`FIG. 7 is a position diagram of seat sensors illustrating
`sensor grouping;
`FIG. 8 is a flow chart for deployment decision, according
`to the invention; and
`FIG. 9 is a flow chart representing the logic for deter-
`mining the facing direction of an infant seat as required by
`the algorithm of FIG. 8.
`
`DESCRIPTION OF THE INVENTION
`
`Referring to FIG. 1, a SIR system includes a SIR module
`13 coupled to a seat occupant sensing system 14. The SIR
`module 13 includes an accelerometer 15 mounted on the
`vehicle body for sensing an impending crash, a micropro-
`cessor 16 for receiving a signal fiom the accelerometer and
`for deciding whether to deploy an airbag. An airbag deploy-
`mentunit 18 is controlled by the microprocessor 16 and fires
`a pyrotechnic or compressed gas device to inflate an airbag
`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 14.
`The seat occupant sensing system 14 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
`
`6
`
`

`

`5,732,375
`
`4
`The next step in FIG. 4 is to determine the load rating of
`each sensor <52>. The load rating is a measure of whether
`the sensor is detecting some load and is used for pattern
`recognition purposes. Low loads present a borderline case
`which is rated by fuzzy logic according to a function similar
`to that of FIG. 5. As shown in FIG. 6, if a load is below a
`base value d. which may be four. the rating is zero and if it
`is above the base value it is the difference between the base
`and the measured load up to a limit value of. say, four. The
`total load rating is calculated <54> by summing the indi—
`vidual sensor ratings and the fuzzy contribution of the total
`load rating is again determined as in FIG. 5 where a total
`load below a minimum threshold b is zero. a total load above
`the minimum is the total load minus the minimum threshold
`up to a limit at maximum threshold c. The minimum
`threshold may be four, for example, and the maximum
`threshold may be 24.
`Next a check is made for force concentration in a local-
`ized area (56>. Four overlapping localized areas are defined
`as shown in FIG. 7. The front four sensors 1, 6, 7 and 12 are
`in the front group, the rear eight sensors 2, 3, 4, 5, 8. 9. 10
`and 11 are in the rear group. the left eight sensors 1. 2, 3. 4,
`S. 6, 8, and 9 are in the left group. and the eight sensors 4.
`5, '7, 8, 9. 10. 11, and 12 are in the right group. The algorithm
`determines if the pressure is all concentrated in one group by
`summing the load ratings of the sensors in each group and
`comparing to the total load rating. If the rating sum of any
`group is equal to the total rating, a flag is set for that group
`(all right. all front etc.).
`Finally the force and fuzzy contribution is computed for
`each pair of sensors and for the center group <58>. The force
`on each pair is used to detect occupants such as small
`children which can easily sit in one small area of the seat.
`These measures are looking for the pressure to be evenly
`distributed over the two sensors of the pair To accomplish
`this the algorithm looks at each pair, determines the mini—
`mum value of the two sensors. and clip the higher one to a
`calibrated “delta” from the lower. If the force is evenly
`distributed over the two sensors the values will be about
`equal and the sum will be unalfected by clipping. The sum
`of the two sensor forces, as adjusted, comprise the force
`measure of the pair. The fuzzy contribution of each pair is
`equal to the force measure of the pair but limited to a
`maximum value such as 20 which is calibrated separately for
`each pair. The center group measure is the sum of the sensor
`forces and the fuzzy contribution is equal to the sum of the
`four sensors but limited to a calibrated maximum value.
`
`SENSOR
`
`3
`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 MD 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 airbag 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, 10 kohms and the
`variable resistors vary between 10 kohms at high pressure
`and 100 kohrns at low pressure. Then the voltage applied to
`the ports 30 will vary with pressure. Each sensor comprises
`two polyester sheets each having a film of resistive ink
`connected to a conductive electrode. the two resistive films
`contacting one another such that
`the resistance between
`electrodes decreases as pressure increases. Such pressure
`sensors are available as ALPS pressure sensors from Alps
`Electric Co. Ltd. Tokyo. Japan.
`The mounting arrangement of sensors 28 on a bottom
`bucket seat cushion is shown in FIG. 2. The sensors are
`numbered 1—12 according to seat location. A left pair of
`sensors 1 and 2 are on the left side of the seat with sensor
`2 to the rear and slightly inboard of sensor 1. Sensors 11 and
`12 are the corresponding right pair of sensors. A front pair
`of sensors 6 and 7 are at the front of the seat and a rear pair
`of sensors 3 and 10 are at the rear. The four remaining
`sensors 4.5.8 and 9 are the center group of sensors. Sensors
`5 and 8 are astride the seat centerline and are just in front of
`sensors 4 and 9. The center group is positioned just to the
`rear of the seat middle.
`
`The method of operation is illustrated by a series of
`flowcharts wherein the functional description of each block
`in the chart is accompanied by a number in angle brackets
`<nn> which corresponds to the reference number of the
`block. The overall operation is shown in FIG. 3 wherein the
`sensor values are read by the microprocessor 22 <36> and
`the data is adjusted by bias correction and low pass filtering
`68>. One sensor at a time is turned on. sampled four times
`and averaged. Then a bias calibrated for each sensor is
`subtracted from each sensor reading, and the data is filtered
`with a time constant on the order of 1 second. Then all
`decision measures are computed <40> and decision algo-
`rithms are run <42>. Ultimately a decision is made to allow
`or inhibit airbag deployment <44>. Then either an inhibit
`light is turned on <46> or an allow light is turned on <48>.
`FIG. 4 shows the algorithm for computing decision mea-
`sures 40. Total force is calculated by summing the sensor
`values and a fuzzy contribution is calculated for the total
`force <50>. Each sensor produces a voltage which is
`expressed as a digital value in the range of 0—255. The
`typical range is on the order of 0—50. however. An empty
`seat will have a total force near 0 after the bias adjustments.
`A fully loaded seat could go up to about 3000 but 2000 is
`more likely. For discrimination purposes, the inhibit/allow
`threshold is less then 255 and for reporting to the display
`software,
`the value is clipped to 255. The total fuzzy
`contribution is determined according to the function shown
`in FIG. 5. If the total force is below a minimum or inhibit
`threshold b. the fuzzy value is zero; if it is above a maximum
`or allow threshold, the fuzzy value is the difference between
`the inhibit and allow thresholds; and if it is between the
`thresholds the fuzzy value is equal to the force value minus
`the inhibit threshold. The thresholds are calibrated for each
`application; they may be for example, an inhibit threshold of
`32 and an allow threshold of 128.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
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`
`50
`
`55
`
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`L
`
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`7
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`
`The measured values, ratings, patterns and flags are used
`in deciding whether to allow or inhibit deployment. As
`shown in FIG. 8, the decision algorithm 42 first: decides if
`rails of an infant seat are detected <60> and if so whether the
`
`7
`
`

`

`5 ,732,375
`
`5
`
`seat is facing forwardly or rearwardly <62.>. Deployment is
`allowed for a forward facing seat and inhibited for a rear
`facing seat. This is determined as shown in FIG. 9 wherein
`if the total force is greater than a certain value <64> the seat
`is forward facing and deployment is allowed. If not, and the
`front pair of sensors is loaded and the total force is greater
`than another set value <66>. the seat is forward facing and
`deployment is allowed. Otherwise the seat is rear facing and
`deployment is inhibited. It should be noted that whenever an
`inhibit or allow decision is made, that decision is controlling
`and all other conditions lower on the chart are bypassed.
`If rails are not detected <60>, the total force is compared
`to high and low thresholds <68>. If it is above the high
`threshold deployment is allowed and if below the low
`threshold the deployment is inhibited. Otherwise, if the
`localized force for a sensor group is above a threshold and
`the flag corresponding to that group is set <70>, deployment
`is allowed. If not, the next step is to compare the total load
`rating to high and low thresholds <72>. Deployment is
`allowed if the rating is above the high threshold and inhib-
`ited if below the low threshold. Each of the sensor pairs for
`front, left, right, and rear are compared to threshold values
`<74—80>. If any of them are above its allowed. If not, the
`center group force is compared to a threshold <82> to decide
`upon allowance. Finally, the total fuzzy value is compared to
`a threshold <84> to allow deployment if it is sufficiently
`high, and if not the deployment is inhibited. The fuzzy value
`decision manages a marginal case where several of the
`previous measures came close to exceeding their thresholds
`but didn’t, the fuzzy measure can still allow deployment.
`It will thus be seen that airbag deployment can be allowed
`or inhibited by a pattern of resistive sensors embedded in a
`seat cushion and coupled to a microprocessor to detect the
`force on each sensor to determine the loading pattern as well
`as the force values from which infant seat presence and
`orientation are determined as well as the presence of other
`occupants.
`The embodiments of the invention in which an exclusive
`property or privilege is claimed are defined as follows:
`1. A method of airbag control in a vehicle having an array
`of force sensors on the passenger seat coupled to a controller
`for determining whether to allow airbag deployment based
`on sensed force and force distribution comprising the steps
`of:
`
`measuring the force detected by each sensor;
`calculating the total force of the sensor array;
`allowing deployment if the total force is above a total
`threshold force;
`defining a plurality of seat areas, at least one sensor
`located in each seat area;
`determining the existence of a local pressure area when
`the calculated total force is concentrated in one of said
`seat areas;
`calculating a local force as the sum of forces sensed by
`each sensor located in the seat area in which the total
`force is concentrated; and
`allowing deployment if the local force is greater than a
`predefined seat area threshold force.
`2.. The method of airbag control as defined in claim 1
`including:
`determining a pattern of sensor loading;
`determining from the pattern of sensor loading whether an
`infant seat is on the passenger seat;
`then determining from the total force and force distribu-
`tion whether the infant seat is facing forward or rear-
`ward;
`
`6
`allowing deployment for a forward facing seat; and
`inhibiting deployment for a rearward facing seat.
`3. The method of airbag control as defined in claim 2
`wherein the step of determining a pattern of sensor loading
`comprises detecting which sensors are below a first load
`threshold and which sensors are above a second load thresh-
`old.
`
`4. The method of airbag control as defined in claim 2
`wherein the step of determining from the pattern of loaded
`sensors whether an infant seat is present comprises:
`establishing a table of loaded and unloaded sensor pat-
`terns which result from the configuration of the bottom
`of an infant seat; and
`deciding that an infant seat is present when the pattern of
`sensor loading matches one of the table patterns.
`5. The method of airbag control as defined in Claim 2
`wherein the step of determining whether the infant seat is
`facing forward or rearward comprises:
`deciding that the seat is facing forward when
`1) the total force is greater than a first value. or
`2) sensors in the flour of the seat are loaded and the
`total force is greater than a second value; and
`deciding that the seat is facing rearward when both the
`conditions 1) and 2) are not true.
`6. The method of airbag control as defined in claim 1
`including:
`determining a pattern of sensor loading;
`prior to the step of allowing deployment if the total force
`is above a total threshold force, determining from the
`pattern of sensor loading whether an infant seat is on
`the seat;
`
`then determining from the total force and force distribu-
`tion whether the infant seat is facing forward or rear-
`ward;
`allowing deployment for a forward facing seat; and
`inhibiting deployment for a rearward facing seat.
`7. The method of airbag control as defined in claim 1
`wherein the defined seat areas overlap so that some sensors
`are included in more than one seat area, the seat areas
`including a front area, a rear area, a right area and a left area.
`8. The method of airbag control as defined in claim 1
`wherein each of said seat areas includes a secondary group
`of sensors peculiar to that seat area and the method includes:
`calculating a modified local force for each secondary
`group located in a seat area in which the total force is
`concentrated; and
`
`allowing deployment if the modified local force for
`exceeds a threshold for that secondary goup.
`9. The method of airbag control as defined in claim 8
`wherein each secondary group of sensors comprises a pair
`and the step of calculating a modified local force comprises
`limiting the higher sensor force to a maximum delta above
`the lower sensor force and adding the higher sensor force, as
`limited, to the lower sensor force.
`10. The method of airbag control as defined in claim 1
`including the steps of:
`defining a center seat area ineluding a group of sensors
`located in the center of the passenger seat,
`calculating a local force for the center seat area as the sum
`of the forces sensed by the sensors in the center seat
`area; and
`.
`allowing deployment if the local force for the center seat
`area is greater than a predefined center seat area thresh-
`old force.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`8
`
`

`

`5,732,375
`
`7
`
`11. Amethod of airbag control in a vehicle having an array
`of force sensors on the passenger seat coupled to a controller
`for determining whether to allow airbag deployment based
`on sensed force and force distribution comprising the steps
`of:
`
`measuring the force sensed by each sensor;
`calculating the total force of the sensor array;
`allowing deployment if the total force is above a total
`threshold force;
`
`assigning a load rating to each sensor based on its
`measured force. said load ratings being limited to
`maximum value;
`
`summing the assigned load ratings for all the sensors to
`derive a total load rating; and
`allowing deployment if the total load rating is above a
`predefined total load threshold, whereby deployment is
`allowed if the sensed forces are distributed over the
`passenger seat. even if the total force is less than the
`total threshold force.
`
`12. The method of airbag control as defined in claim 11
`wherein the step of assigning a load rating to each sensor
`comprises:
`establishing a base force; and
`assigning a load rating according to- the measured force
`minus the base force.
`13. The method of airbag control as defined in claim 11
`further including the steps of:
`defining a plurality of seat areas, at least one sensor
`located in each seat area;
`
`determining the existence of a local pressure area when
`the calculated total force is concentrated in one of said
`seat areas;
`
`calculating a local force as the sum of forces sensed by
`each sensor located in the seat area in which the total
`force is concentrated; and
`
`allowing deployment if the local force is greater than a
`predefined seat area threshold force.
`14. The method of airbag control as defined in claim 13
`further including the steps of:
`determining individual fuzzy values based on the total
`force. the local forces for each seat area. and total load
`rating;
`summing said fuzzy values; and
`allowing deployment if the summed fuzzy values exceed
`a threshold.
`
`15. A method of airbag control as set forth in claim 11,
`including the steps of:
`determining a fuzzy total force contribution value based
`on the calculated total force;
`
`determining a fuzzy total loading contribution value based
`on the total load rating; and
`summing the fuzzy total force and fuzzy total loading
`contribution values. and allowing deployment if the
`summed contribution values exceed a predefined fuzzy
`threshold.
`16. The method of airbag control as defined in claim 15
`wherein the steps of determining the fuzzy total force and
`total loading contribution values comprises:
`
`10
`
`15
`
`20
`
`30
`
`35
`
`4D
`
`45
`
`50
`
`55
`
`60
`
`8
`setting minimum and maximum thresholds for the total
`force and total load rating; and
`subtracting the minimum thresholds from the respective
`total force and total load rating, and limiting each
`difference to the respective maximum threshold; and
`determining the fuzzy total and total loading contribution
`values based on the respective limited dilferences.
`17. A method of airbag control in a vehicle having an
`array of force sensors on the passenger seat coupled to a
`controller for determining whether to allow airbag deploy-
`ment based on sensed force and force distribution compris-
`ing the steps of:
`measuring the force sensed by each sensor;
`calculating the total force of the sensor array;
`allowing deployment if the total force is above a total
`threshold force; and
`if the total force is not above the total threshold force.
`determining a fuzzy total force contribution value
`based on the calculated total force;
`
`defining a plurality of seat areas, at least one sensor
`located in each seat area, calculating a local force for
`each seat area as the sum of forces sensed by each
`sensor located in that seat area. and determining a fuzzy
`local force contribution value based on each of the
`calculated local forces; and
`summing the fuzzy total force and fuzzy local force
`contribution values, and allowing deployment if the
`summed contribution values exceed a predefined fuzzy
`threshold.
`‘
`18. The method of airbag control as defined in claim 17
`wherein the steps of determining the fuzzy total and local
`force contribution values comprises:
`setting a minimum and maximum force threshold for each
`total and local force; and
`subtracting the minimum force thresholds from the
`respective total and local forces and limiting each
`ditference to the respective maximum force threshold;
`and
`
`determining the fuzzy total and local force contribution
`values based on the respective limited differences.
`19. The method of airbag control as defined in claim 17
`wherein
`
`a pair of sensors are located
`in each seat area, and wherein:
`the step of calculating the local force for each seat area
`comprises the steps of:
`limiting the higher force of the respective pair of
`sensors to a set amount greater than the lower force
`of the respective pair of sensors, and
`summing the lower force and the higher force, as
`limited, to derive the local force;
`and the step of determining a fuzzy local force contribu—
`tion amount comprises the steps of:
`setting a maximum pair force threshold, and
`setting the fuzzy local force contribution amount equal
`to the local force limited to the maximum pair force
`threshold.
`
`9
`
`