FILE HISTORY
`
`US 6,012,007
`
`PATENT:
`
`6,012,007
`
`INVENTORS: Fortune. Duane Donald
`
`Cashler, Robert John
`
`TITLE:
`
`Occupant detection method and
`apparatus for air bag system
`
`APPLICATION
`NO:
`
`US1 997868338}-\
`
`FILED:
`
`03 JUN 1997
`
`ISSUED:
`
`04 JAN 2000
`
`COMPILED:
`
`06 MAY 2014
`
`1
`
`KMA-1 002
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`

`
`OCCUPANT DETECTION METHOD AND APPARATUS FOR AIR BAG
`
`6,012,007
`
`SYSTEM
`
`Transaction History
`
`Transaction Descri tion
`Date
`nformation Disclosure Statement
`06-03-199?
`nforrnation Disclosure Statement
`06-03-1997
`nitial Exam Team nn
`07-12-1997
`FW Scan & PACR Auto Securit Review
`09-08-199?
`10-23-1997 A lication Dis atched from OIPE
`12-18-1997
`Case Docketed to Examiner in GAU
`12-19-1997 Chane in Power ofAtiorne (Ma Include Associate POA
`01-20-1999
`Case Docketed to Examiner in GAU
`
`IDS Filed
`[DS Filed
`
`04-0?-1999 Non-Final Rejection
`04-09-1999 Mail Non-Final Re’ecti0n
`07-09-1999
`Res ortse after Non-Final Action
`0?-21-1999
`Date Forwarded to Examiner
`08-18-1999 Mail Notice ofAl1owance
`
`08-18-1999 Notice ofAl1owance Data Verification Completed
`09-0?-1999 Workflow - Drawings Finished
`09-07-1999 Workflow — Drawings Matched with File at Contractor
`09-011 999 Workflow - Drawins Received at Contractor
`09-17-1999 Workflow - Drawins Sent to Contractor
`09-21-1999 Workflow - File Sent to Contractor
`10-15-1999
`Issue Fee Pa ment Verified
`
`12-15-1999 Workflow - Complete WF Records for Drawings
`12-19-1999 Agplieation Is Considered Ready for Issue
`12-23-1999
`Issue Notification Mailed
`01-04-2000
`Recordation of Patent Grant Mailed
`
`3
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`

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`POSITION
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`INDEX OF CLAIMS
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`US006l'}'l20U':'A
`
`United States Patent
`Fortune ct al.
`
`[19]
`
`[m Patent Number:
`[45] Date of Patent:
`
`6,012,007
`Jan. 4, 2000
`
`|S-4] UC(.‘Ul'AN'l' l)E'l'EC'l‘lDN METHUIJ AND
`APPARJXTUS FOR AIR BAG SYSTEM
`
`[5t':|
`
`References Cited
`U_S_ l’A'l‘LN‘['
`|JE)(.‘UMEN‘l'5
`
`|75[
`
`lnvunlursz
`
`lluane Donald Fortune, l_uhanon;
`Robert John Cashlcr, Kukumo, bath
`of 1nd.
`
`73
`
`.
`.
`.
`.
`.
`.
`.'
`.
`'
`.
`. I
`5
`- -
`I Abmym Delphi luhnolnhleb’ [m ’ lmy’ MM:
`I
`[21] Appl. No; EI3f868,333
`I2...
`Filed:
`Jun. 3. 199’?
`
`_
`
`“claim U-55 —“PP"¢‘3‘5'1“ nil“!
`_
`‘
`_
`_
`_
`_
`(inngllaualmn-1n:p.1rI 0{_app|u:ul|or| N0. l‘|8.’::b6.lJ2‘), Dec. 1.
`IP93. Pal. N0. 3.732-3'3
`Int. CL?
`B601? 2l.I'l2; Bbilll 21932
`U_§_ CL _
`I 70]/.35; 7(][_;4(,; 34()_,43(,-‘
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`Field of Search
`3405436. 18 ...'i'], 273'. ?.3W73U.l—'?35;
`307r"‘}.|
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`13(}___;r];
`
`5.-|13ll.()4li
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`
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`JI5d_a‘d-24.05
`'.I'lI|.‘4-S
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`!'r:'m::rr !;'xrmr1'm:r—WilIia|n A. tfuchlinski Jr.
`A
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`.
`‘
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`Aswsrarrf £;.rrJmmc' —Yonc1 Beaulleu
`.-*1.'mrm’_r, Agclnf. or Fr'rm—Jimrny [.. Funkc
`[57|
`ABS'l‘RAC'l‘
`Prcasurc sensors on lh: hollom surface of a seat cushion
`rcspund lo occupant weight. A mic.‘tnpr<msmr evalualcs the
`sensor uutpuls according lu luta] 1'-Jrce,
`load rating.
`lung
`term avwagc. Sensor groups and a fuzzy nwasflre [0 dis_
`criminalu hclwcun large and small uccupanls and allow air
`hag dcpluymcnl lhrlargc hut nm small m:cup:1nts.Allnw and
`inhibit decisions are filtered avoid sudden response to Iran-
`5LL'.I'Il prusafiuru changes on lhu seal. When a large nccupanl is
`pusilivuly tlulcclcd. an alluw dascisiun is locked in placv: as
`1093‘. 35 101-'11 tom“ ‘5x‘3'3'5d5 3 ”JW5h01d-
`
`27 Claims, 5 Drawing Sheflls
`
`AD ULT LOCK
`
`DECISION FILTEH = MAX.
`TOTAL FORCE 2- LOCK THRESHOLD
`LOCK TIMER > LOCK DELAY
`
`TOTAL FORCE >
`UNLOCK THHESHOLD
`
`INCREMENT FLAG VALUE
`TOWARD MAX.
`
`TOTAL FORCE <
`UNLOCK THRESHOLD
`FLAG VALUE > O '?
`
`DECFIEMENT FLAG
`VALUE TOWARD ZERO
`
`FLAG VALUE >0 ’?
`
`N0
`
`FLAG = CLEARED
`
`FLAG = SET
`
`12
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 1 ofS
`
`6,012,007
`
`DECISION
`
`MICHOPROCESSOR
`
`
`
`MICHOPFIOCESSOH
`
`.
`
`SIR MODULE i SEAT OCCUPANT
`DETECTOR
`
`13 ._,/I
`
`- 1
`PRIOR ART
`
`13
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 2 of 5
`
`6,012,007
`
`HG - 4
`
`INPUT ‘I2
`sensor:
`VALU ES
`
`ADJUST DATA WITH BIAS
`AND LOWPASS FILTER
`THE DATA
`
`FROM FILTERED DATA
`COMPUTE ALL DECISION
`MEASURES
`
`RUN DECISION
`ALGORITHMS
`
`DECISION
`FILTER
`
`INHIBIT
`DECISION
`
`FINAL
`CONSENT
`
`COMPUTE DECISION MEASURES
`
`CALC ULATE
`
`' TOTAL FORCE & THRESHOLD
`* LOAD RATINGS 8: MEASURE
`' LONG TERM AVERAGE 8: THRESHOLD
`' EACH GROUP MEASURE 8: THRESHOLD
`* FUZZY MEASURE
`
`14
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 3 of 5
`
`6,012,007
`
`FIG-6
`
`VARIABLE THRESHOLD
`
`GET INHIBIT TIMES
`T1 +T2
`
`MEASURE :-
`MIN. ACTIVITY
`VALUE
`
`MEASURE <
`
`THFIE§HOLD
`
`I NCFIEMENT
`TH FIESHOLD
`TOWARD MAX.
`
`DEOFIEM ENT
`THRESHOLD
`TOWARD MIN.
`
`RESET TIMEFI
`
`FI ETU FIN
`
`b
`MEASURE
`
`15
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 4 of 5
`
`6,012,007
`
`ADULT LOCK
`
`HG . 8
`
`DECISION FILTER .2 MAX.
`TOTAL FORCE > LOCK THRESHOLD
`LOCKTIMER > LOCK DELAY
`
`TOTAL FORCE >
`UNLOCK TH RES HOLD
`
`INCREMENT FLAG VALUE
`TOWARD MAX.
`
`TOTAL FORCE <
`UNLOCK THRESHOLD
`FLAG VALUE > 0 '?
`
`DECREMENT FLAG
`VALU E TOWARD ZERO
`
`FLAG VALUE >0 ?
`
`NO
`
`FLAG - CLEARED
`
`RETURN
`
`INCREMENT
`coumen
`
`FILTER
`
`DECFIEM ENT
`COUNTER
`
`- courgR>13a
`=- COUNT >123
`AND
`cowcem
`
`c§,',,'§‘°,‘5';4T
`
`RETURN
`
`16
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 5 of 5
`
`6,012,007
`
`F'G'9
`
`PROCESS ADULT LOCK FLAG
`
`ADULT LOCK FLAG SET ?
`
`YES
`
`98
`
`LOAD RATING LOW ?
`
`NO
`
`NO
`
`YES
`
`QQ
`
`INHIBIT DECISION
`TO FILTER
`
`ALLOW DECISION
`TO FILTER
`
`17
`
`

`
`6,012,007
`
`1
`OCCUPANT DETECTION METHOD AND
`APPARATUS FOR AIR BAG SYSTEM
`
`This is a continuation-in-part of US. patent application
`Ser. No. 08,566,029, tiled Dec. 1, 1995, now US. Pat. No.
`5,732,375, issued Mar. 24, 1993, which is also assigned to
`the aaiignee of the present invention.
`FIELD OF THE INVENTION
`
`.
`
`1‘his invention relates to an occupant restraint system
`using an occupant detection device and particularly to an
`airbag system having seat pressure detectors in the scat.
`BACKGROUND OF THE INVENTION
`
`The expanding use of supplemental inflatable restraints
`(S1115) 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 a 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 includinga 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). In a system
`designed for effective interaction with a full sized adult, an
`advantageous interaction with a small person may not be
`attained. In such cases it is preferred to disable the passenger
`side airbag when a small person occupies the seat or when
`the seat is empty.
`It has been proposed in U.S. Pat. No. 5,474,327 to
`Schousek, entitled “VEI-IlCl..E OCCUPANT RESTRAINT
`WITH SEAT PRESSURE SENSOR", and in US. Pat. No.
`5,‘l'32,375, issued Mar. 24, 1998 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 and weight
`distdbution, and for inhibiting deployment in certain cases.
`These disclosures teach the use olsensors on the top surface
`of the seat, just under the sat cover, and algorithms espe-
`cially for detecting the presence and orientation of infant
`seats. Both of these disclosures form a foundation for the
`premnt invention and are incorporated herein by reference.
`It
`is desirable, however to provide a system which is
`particularly suited for disrximinating between heavy and
`light occupants and for robust operation under dynamic
`conditions such as occupant shifting or bouncing due to
`rough roads.
`SUMMARY OF THE INVENTION
`
`It is therefore an object of the invention to discriminate in
`a SIR system between large and small seat occupants for a
`detcrrnination of whether an airbag deployment sltoulrl be
`permitted. Another object in meh a system is to maintain
`reliable operation in spite of dynamic variations in sensed
`pressures.
`A SIR system, as is well known, has an acceleration
`sensor to detect an impending crash, a microprocessor to
`process the setsor signal and to decide whether to deploy an
`air bag, and a deployment unit lined 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 microproccsor whether
`to allow or inhibit deploying the air bag.
`A number of sensors, judicially located in the seat, can
`garner sufficienl load and distribution information to allow
`
`2
`determination of the occupant size. Each sensor is a very
`thin resistive device, having lower resistance as pressure
`increases. This information is then used to determine
`whether to inhibit airbag deployment. The sensors are
`arranged in groups in the seat. A microprocessor is pro-
`grammed to sample each sertsor, determine a total weight
`parameter by summing the forces, determine the forces on
`local groups of sensors, and averaging or filtering to provide
`several different measures ot seat occupancy, each of which
`can be used determine whether to allow deployment.
`BRIEF DESCRIPTION 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 Ehematic diagram of a prior art SIR system
`incorporating a seat occupant detector;
`FIG. 2 is a cross section of a seat equipped with pressure
`sensors, according to the invention:
`FIG. 3 is a view of a seat support of FIG. 2 equipped with
`pressure sensors;
`FIG. 4 is flow chart representing an overview of an
`algorithm for detennining deployment consent according to
`the invention;
`FIG. 5 is a how chart representing a method of computing
`decision measures used in the algorithm of FIG. 4;
`FIG. 6 is a flow chart representing a method of computing
`variable thresholds according to the invention;
`FIG. 7 is a graphical representation of a function used in
`fuzzy logic for determining toad ratings and a fuzzy mea-
`sure;
`FIG. 8 is a Bow chart representing a method of computing
`an adult lock flag according to the invention;
`FIG. 9 is a flow chart for deployment decision according
`to the invention; and
`FIG. 10 is a flow chart representing a method of filtering
`allow and inhibit decisions according to the invention.
`DESCRIPTION OF THE lN\"EN'l‘l0N
`
`Referring to FIG. 1, a SIR system includes a SIR module
`13 uaupled to a seat occupant sensing system I4. 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 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 lines 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 lti will
`show a failure of the seat occupant sensing system 14.
`It is the aim of the seat sensing system 14 to inhibit air bag
`deployment when a seat is empty or occupied by a small
`child, while allowing deployment when the occupant
`is
`large. For example, the system may be tuned to always
`inhibit deployment for occupants weighing less than 66
`pounds, and always allow deployment for occupants exceed-
`ing 105 pounds. The seat occupant sensing system 14
`comprises a microprocessorilz having a 5 volt supply and an
`enabling line 2-‘lperiodically 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 premtre sensor or variable
`resistor 28. and the junction point of each resistor 26 and
`
`18
`
`

`
`6,012,007
`
`3
`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 air bag .
`deployment and the decision is coupled to the microproces-
`sor 16 by a line 32. The microprocessor 22 also monitors its
`decisions for consistency and i§t.tes a fault signal on line 34
`to the microprocessor 16 if faults continue to occur over a
`long period.
`Each fixed resistor 26 is, for example, 10 kohms and the
`variable resmors vary between 10 kohms at high pressure
`and lfltl kohms at low premtre. 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 [tom Alps
`Electric Co., Ltd.. Tbkyo. Japan.
`FIG. 2 shows a seat cushion 36 having an upper surface
`38 for holding an occupant, and a lower surface 40 seated on
`a rigid sheet or plastic form 42 which in turn is supported by
`a seat subassembly 44. The form 42, also shown in FIG. 3,
`holds a dozen premure sensorszs on its upper surface so that
`the sensors are premed against the bottom surface 40 of the
`seat cushion 36..A.utomotive seat cushions assetnbliesdo not
`normally have the form 42 but here it serves to hold the
`sensors 28 and to provide a reaction surface for the sensors.
`allowing each semtorto detect a force imposed by the weight
`of a seat occupant.
`The method of operation is illustrated by a series of
`fiowcharts 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. 4 wherein the
`sensor values are read by the microprocessor 22 «:46: and
`the data '5 adjusted by bias correction and low pass filtering
`<48). Once every 100 ms one sensor at a time is turned on
`and sampled. Then a bias calibrated for each sensor is
`subtracted from each sensor reading. Then all decision
`measures are computed -:5D> and decision algorithms are
`run <52>. The algorithm output is filtered to avoid the effects
`oftransient events and ultimately adecision is made to allow
`or inhibit air bag deployment <54>. Then either an inhibit
`signal is imued <56) or an allow signal is issued -c58>. The
`microprocessor executes the algorithm every 100 ms.
`The computation of decision measures, as shown in FIG.
`5, involves calculating total force and its threshold, sensor
`load ratings and measure.
`long tenn average of sensor
`readings and its threshold. the measure of each sensor group
`(right, left, etc.) and corresponding threshold, and a fuzzy
`measure of sensor readings. A fixed threshold is provided for
`the fuzzy measure and the load rating measure. The other
`thresholds are variable.
`The variable threshold for a measure will slowly increase
`if the measure is above a selected minimum activity level
`(chosen for each measure) and will quickly decrease if the
`measure is below the level. Inhibit times are chosen for each
`measure to control the rate of increase or decrease; for
`increase the time T1 is preferably in the range of 30 to 300
`seconds, and for decrease the time 12 is preferably less than
`1 second. The threshold is allowed to vary between a
`minimum value and a maximum value. The variable thresh-
`old is calculated as shown in FIG. 6. For this and subsequent
`flowcltarts the functional description of each block in the
`
`4
`chart is accompanied by a number in angle brackets 4-'.'nt1>
`which corresponds to the reference number of the block.
`Inhibit times are selected for each measure. The inhibit times
`T1 and T2 for the particular measure is retrieved from
`memory <60». If the measure is above the minimum activity
`level <62> and below the variable threwold <6-I>, and a
`timer is greater than T2 <66:-, the threshold is incremented
`<6Be- and the timer is reset <70:-. When the measure is less
`than the minimum activity level <62> and the timer exceeds
`T1 -<'i'2>, the threshold is decremenled -<7-t»> and the timer
`reset -c70>.
`Referring again to FIG. 5, the total force is simply the sum
`of the sensor outputs. The load ratings are determined in the
`same way as in the above mentioned application Ser. No.
`D8J'566.029 and asrellected in FIG. 7. There if a measure has
`a value lower than a it has a zero rating and if it has a value
`greater than b has a maximum rating, while intermediate
`values are linearly dependent on the measure. Thus each
`sensor is given a rating (fuzzy term) depending on its output
`and reflects the certainty that a load is present. The sum of
`the ratings gives the load rating measure. The long term
`average is calculated by 1) averaging all the sensor outputs
`in each sample period. 2) averaging all of the averages over,
`say, 16 sample period; and then 3) long term filtering the
`result by passing the result through a low pass software filter
`with a 10 to 20 second time constant. The filter output is the
`long term average measure. Each group measure is the sum
`of sensor outputs for various groups of sensors such as a
`right group. left group, from group, rear group and central
`group.
`The fuzzy measure is calculated by 1) applying the FIG.
`7 function to the long term average measure to obtain a long
`term fuzzy value. 2) applying the FIG. 7 function to the load
`rating measure to obtain a load rating fuzzy value. and 3)
`calculating the product of the two fuzzy values.
`FIG. 8 is a flowchart for processing an Adult Lock Flag
`which will be used is the main decision algorithm. The term
`“A.t.lult" refers not. to the age or maturity of an occupant but
`rather to a weight which is chosen to distinguish from a
`small child. When the Adult Luck Flag is set, the output
`decision will always be to allow deployment. The algorithm
`LL‘?-Bsa lock threshold which is above the total fat-on threshold
`range and an unlock threshold which represents an empty
`seat. It also uses a lock delay on the order of one to five
`minutes, and a lock timer which measures the time since
`vehicle ignition is turned on. If the decision filler 54 is at its
`maximum value, the total force is greater than the lock
`threshold. and the lock timer is larger than the loci: delay
`#76:», a flag value is increased toward a maximum value
`<‘}'B> and tI1eAdt.tll Lock Flag is set <80». If the decision at
`block '76 is No, it is determined whether the total force is
`above the unlock threshold <;B2> and if not, whether the total
`force is below the unlock threshold and the llag value is
`greater than zero <84). If so, the flag value is dccremented
`toward zero <36>, and in either case the flag, value is tested
`<88:-; ifthe value is above zero the Flag is set -elllb and if
`the value is zero the Flag is cleared <90:-.
`The main decision algorithm 42 is shown in FIG. 9. Note
`that this algorithm will result
`in an allow or an inhibit
`decision. but this decision is preliminary. subject to subse-
`quent filtering to obtain a final consent to deployment. Each
`measure '5 determined to be high or low by comparison with
`its variable threshold if one has been computed. or against
`a fixed threshold. The Adult Luck Flag is processed «:92:
`according to P16. 8 and if the Flag is set <94: an allow
`decision is made. If not, and the load rating is low <96> an
`inhibit decision is made. If the rating is not low the total
`
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`
`5
`force is tested <98, 100:-. If high, an allow decision is issued
`and if low an inhibit decision is issued. If neither,
`it
`is
`determined whether the long term average measure -:lIl2:-
`the load rating <104>, ora group measure <lll§> is high.and
`to issue an allow decision Finally, if no decision has yet
`been made, an allow or inhibit decision is made on the basis
`of the fuzzy measure 4108:.
`"the final judgment of whether to consent to deployment
`is made in the decision filter asshnwn in FIG. 10. An up and
`down counter starting at zero and having a maximum count
`of 255 is used. Ifan allow decision is made e42> the counter
`is incremented <l10> and if an inhibit decision is made the
`counter is decremented <l12>. When the count exceeds 133
`«I14: final consent to deployment
`is granted «I16»; if
`consent is already present, a count over [23 is needed to
`maintain that state to afford hysteresis. When the count falls
`below 125 the comenl is revoked and deployment will be
`inhibited. Assttming that the increment size is one count. at
`the I00 ms loop execution late a minimum of 13.3 seconds
`will be required to issue the consent, and at least 25.5
`seconds are needed to reach the maximum count needed to
`set the Adult Lock I-‘lag, Similarly, once the rnarcimum count
`is attained, at least 13.2 seconds are needed to revoke the
`consent.
`It will thus be seen that pr ncess of determining whether an
`adult siate person is occupying the seat is carried out by
`analyzing sensor output with several measures to insure both
`that deployment will be allowed with at large occupant and
`will not occur with a small occupant. Rapid detection of
`large adults is enabled by the total [ores and load rating
`measures, while dynamic sensor outputs caused by frequent
`occupant movement are managed by the long term average
`measure. The fuuy measure helps discriminate between
`large and small occupants in borderline cases. The seat
`stnrcture with sensors placed on the bottom surface of the
`seat cushion permits sensing of occupant weight without
`great sensitivity to localized forces on the top surface of the
`seat. 011’ center weight distributions caused by sitting on a
`seat edge or leaning in one direction are still detectable.
`The embodiments of the invention in which an exclusive
`property or privilege is claimed are defined as follows:
`1. In a vehicle restraint system having a controller for
`deploying air bags and means lior selectively allowing
`deployment according to the outputs of seat sensors
`rmponding to the weight of an occupant, a method of
`allowing deployment accordingto sensor response including
`the steps of:
`determining measures represented by individual sensor
`outputs and calculating from the sensor outputs a
`relative weight parameter;
`establishing a ll.t'$l threshold of the relative weight param-
`eter;
`allowing deployment when the relative weight parameter
`is above the first threshold;
`establishing a lock threshold above the that threshold;
`setting a lock flag when the relative weight parameter is
`above the lock threshold and deployment has been
`allowed for a given time;
`establishing an unloclt threshold at a level indicative ol an
`empty seat;
`clearing the flag when the relative weight parameter is
`below the unlock threshold for a time; and
`allowing deployment while the lock flag is set.
`2. The method defined in claim 1, including:
`establishing at. second threshold of the relative weight
`parameter; and
`
`IS
`inhibiting deployment when the relative weight parameter
`is below the second threshold.
`3. The method defined in claim 1 wherein the relative
`weight parameter In the total force detected by all
`the
`sensors.
`4. The method defined in claim 1 wherein the relative
`weight parameter is a long term average obtained by the
`following steps:
`averaging all sensor outputs over a plurality of sample
`events to obtain a cumulative average; and
`long temt filtering the cumulative avenge to obtain the
`long term average.
`5. The method defined in claim 1 wherein the relative
`weight parameter is a load rating obtained by:
`calculating a load rating for each sensor as a function of
`the difference between the sensor output and a base
`value; and
`summing the load rating for all the sort; to derive a
`total load ratirtg.
`ll. The method defined in claim 1 wherein the relative
`weight parameter is a fuzzy value obtained by:
`calculating a total load rating for all the sensors;
`determining a fuzzy load value from the total load rating;
`calculating a long term average for all the sensors;
`determining a fuzzy average value from the long term
`average; and
`combining the l"uzzy average and the fuzzy load value to
`obtain the Enzzy value.
`7. The method defined in claim 1 wherein the step of
`setting the lock flag is executed in repetitive loops and
`cnmprism:
`incrementing a flag value toward a maximum value in
`each loop when the relative weight parameter is above
`the lock threshold;
`decrementlng the flag value toward zero in each loop
`when the relative weight parameter is less than the
`unlock threshold; and
`setting the lock flag when the flag value is greater than
`stern and clearing the llag when the bag value is earn.
`an that
`the flag value at any time determines the
`minimum time for clearing the flag.
`3. The method defined in claim 7 including;
`enabling the incrementing step only when adecision filter
`reaches a maximum count; and
`the decision filter includes
`incrementing a counter toward a maximum count in
`each loop when an allow decision is present, and
`decremeutiug the counter when an allow decision is
`absent.
`9. The method defined in claim 1 wherein a step of
`allowing deployment is a preliminary allow decision and
`final deployment cornrent is attained by long term filtering of
`the allow decision.
`Ill. The method defined in claim I wherein a step of
`allowing deployment is a preliminary allow decision and
`final deployment consent is attained by the steps of:
`beginning at a zero count, periodically incrementing a
`counter toward a maximum count when an allow
`decision is present;
`periodically de-crententing the counter when an allow
`decision is absent;
`establishing an allow threshold; and
`issuing deployment consent when the counter count
`exceeds the threshold.
`
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`
`.
`
`7
`11. The method defined in claim lll wherein the allow
`threshold has a first value when deployment consent
`is
`absent and a lower value when deployment oomrent
`is
`present to alford hysteresis.
`12. The method defined in claim 1 wherein the step of
`establishing a first
`threshold includes varying the first
`threshold over time as a luncljon of the relative weight
`parameter when the relative weight parameter is below the
`first threshold.
`13. The method defined in claim 1 wherein the step of
`establishing a titst
`threshold includes varying the Era!
`threshold over time within a defined range by the steps of:
`setting a minimum activity level of the relative weight
`parameter below the defined range;
`increasing the first
`threshold when the relative weight
`parameter is above the minimum activity level and
`below the first threshold;
`decreasing the first threshold when the relative weight
`parameter is below the minimum activity level.
`14. The method defined in claim 13 wherein increasing
`the first threshold is permitted only after set adjustment
`times have elapsed since a previous variation.
`15. The method defined in claim 13 wherein increasing or
`decreasing the first
`threshold is permitted only after set
`adjustment times have elapsed since the previous adjust-
`ment.
`16. In a vehicle restraint system having a controller for
`deploying air bags and meam for inhibiting deployment
`when a seat
`is not octarpied by an adult
`including seat
`sensors responding to the weight of an occupant, a method
`of inhibiting and allowing deployment according to sensor
`response including the steps of:
`determining forces represented by individual sensor out-
`puts and total force represented by all sensor outputs;
`establishing a first threshold of total force and a second
`threshold below the fist threshold;
`inhibiting deployment when the total force is below a
`second threshold, and allowing deployment when the
`total force is above the first threshold;
`establishing a lock tltreshotd above the first threshold;
`setting a lock flag when the total force is above the lock
`threshold and deployment has been allowed for a given
`time;
`establishing an unlock threshold at a level indicative of an
`empty seat;
`clearing the flag when the total force is below the unlock
`threshold for a time; and
`allowing deployment while the lock flag is set,
`1?. In a vehicle restraint system having a controller for
`deploying air bags, means for inhibiting and allowing
`deployment according to whether a seat is occupied by a
`person of at least a minimum weight comprising:
`seat sensors responding to the weight of an occupant to
`produce sensor outputs;
`a microprocessor coupled to the sensor outputs and pro-
`grammed to inhibit and allow deployment according to
`sensor response and particularly pmgrarrtrned to
`determine measures represented by individual senmr
`outputs and calculate from the sensor outputs a
`relative weight parameter,
`establish a first
`threshold of the relative weight
`parameter,
`allow deployment when the relative weight parameter
`is above the first threshold,
`establish a lock threshold above the first threshold,
`
`8
`set a lock flag when the relative weight parameter is
`above the lock threshold and deployment has been
`allowed for a given time,
`establish an unlock threshold at a level indicative of an
`empty seat.
`clear the flag when the relative weight parameter is
`below the unlock threshold for a time, and
`allow deployment while the lock [lag is set.
`18. Means for inhibiting and allowing deployment as
`defined in claim 17 wherein:
`the seat comprises a resilient pad having a top surface for
`hearing an occupant and a bottom surface;
`a support mounting the bottom strrfaoe; and
`the seat sensors are arrayed on the bottom surface for
`sensing forces imposed by the weight of the occupant.
`19. Means for inhibiting and allowing deployment as
`defined in claim 17 whereim
`the seat comprises a resilient pad having atop surface for
`bcaring an occupant and a bottom surface;
`a support irtcludingapancl supporting the bottom surface;
`and
`the seat sensors are arrayed in an interface defined by the
`bottom surface and the panel
`for sensing forces
`imposed by the weight of the occupant.
`20. Means for inhibiting and allowing rleployrnent as
`defined in claim 17 wherein the micruproom is further
`programmed to inhibit deployment when the relative weight
`parameter is below a second threshold.
`21. Means for inhibiting and allowing deployrrtent as
`defined in claim I‘! wherein the relative weight parameter is
`the total force-detected by all the sensors.
`22. Means for inhibiting and allowing deployment as
`defined in claim 17 wherein relative weight parameter is a
`long term average of semtor outputs and the microprocessor
`is further pr