United States Patent
`
`[19]
`
`[11] Patent Number:
`
`6,012,007
`
`Fortune et al.
`
`[45] Date of Patent:
`
`Jan. 4, 2000
`
`US006012007A
`
`[54] OCCUPANT DETECTION METHOD AND
`APPARATUS FOR AIR BAG SYSTEM
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventors: Duane Dunald F°m'"e’ Lebanon;
`Robert John Cashler, Kokomo, both
`of Ind.
`
`5,430,649
`5 732 375
`,
`,
`
`7/1995 Cashleretal. ..................... 364/424.05
`3,1998 Cashier
`701/45
`,
`
`[73] Assignee: Delphi Technologies, Inc., Troy, Mich.
`
`[21] Appl. No.: 08/868,338
`
`[22]
`
`Filed:
`
`Jun. 3, 1997
`
`[63]
`
`Related U-S- APPliC3ti011 Data
`p
`_
`‘
`_
`_
`(,oritmuat1on—1ri—part of application No. (J8,'566,029,Dec. 1,
`1995’ Pat‘ NO‘ 5’732’375'
`Int. Cl.7 .......................... .. B60R 21/12; B60R 21/32
`[51]
`[52] U_s_ C]_ ,,,,,,,,,,,,,,,,,,,,,,,, " 701/45; 701/45; 340/436;
`130/271; 180/273; 230/730,]; 230/735;
`307/9_1
`[58] Field of Search ........................ 701/45, 46; 340/438,
`340/436; 180/271, 273; 280/730.l—735;
`307/91
`
`Primary Examiner—William A. Cuchlinski, Jr.
`Assistant Examiner—Yor1el Beaulieu
`
`Attorney, Agent, or Firm—Jimmy L. Funke
`
`ABSTRACT
`[57]
`Pressure sensors on the bottom surface of a seat cushion
`
`respond to occupant weight. A microprocessor evaluates the
`sensor outputs according to total force, load rating, long
`term average’ Sensor groups and a fuzzy measure to diS_
`crirninatc between large and small occupants and allow air
`bag deployment for large but not small occupants. Allow and
`inhibit decisions are filtered avoid sudden response to tran-
`sierit pressure changes on the seat. When a large occupant is
`positively detected, an allow decision is locked in place as
`1011a as total feree exeeede a threshold-
`
`27 Claims, 5 Drawing Sheets
`
`76
`
`ADULT LOCK
`
`
`
`
`N0
`DECISION FILTER = MAX.
`YES
`TOTAL FORCE > LOCK THRESHOLD
`
`LOCK TIMER > LOCK DELAY
`
`78
`
`
`
`TOTAL FORCE >
`
`INCREMENT FLAG VALUE
`
`UNLOCK THRESHOLD
`TOWARD MAX. YES
`
`TOTAL FORCE <
`UNLOCK THRESHOLD
`FLAG VALUE > 0 ?
`
`
` 1
`
`DECREM ENT FLAG
`VALUE TOWARD ZERO
`
`FLAG VALUE >0 '?
`
`NO
`
`
`
`RETURN
`
`FLAG = SET
`
`80
`
`
`
`KMA-1001
`
`1
`
`KMA-1001
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 1 of 5
`
`6,012,007
`
`I
`I
`
`15
`
`28
`
`24
`
`25
`
`-
`
`26-
`_
`-
`
`28
`
`30
`26
`30
`Imnn
`
`
`
`5
`8
`E
`O
`S
`E
`
`15
`
`ACCELEROMETER
`
`FAULTINDICATOR
`18
`
`AIR BAG
`DEPLOYMENT
`
`12.../I
`- 1
`
`PRIOR ART
`
`*5‘’ 30
`
`i |
`5 M
`DECISION!
`5
`“
`O
`E
`O
`E
`_
`E
`
`
`
`
`34
`
`I
`1
`ii
`
`1
`
`22
`
`"W
`26
`23
`SEAT OCCUPANT \
`DETECTOR
`
`—_—
`
`14
`
`SIR MODULE
`
`2
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 2 of 5
`
`6,012,007
`
`FIG-4
`
`
`INPUT 12
`SENSOR
`VALUES
`
`
`
`ADJUST DATA WITH BIAS
`AND LOWPASS FILTER
`THE DATA
`
`FROM FILTERED DATA
`COMPUTE ALL DECISION
`MEASURES
`
`50
`
`
`
`
`52
`
`
`
`RUN DECISION
`ALGORITHMS
`
`54
`
`56
`
`DECISION
`FILTER
`
`58
`
`INHIBIT
`DECISION
`
`
`
`FINAL
`CONSENT
`
`
`
`FIG-5
`
`
`
`COMPUTE DECISION MEASURES
`
`
`
`50
`
`CALC ULATE
`
`” FUZZY MEASURE
`
`* TOTAL FORCE & THRESHOLD
`
`* LOAD RATINGS & MEASURE
`
`* LONG TERM AVERAGE & THRESHOLD
`
`"' EACH GROUP MEASURE & THRESHOLD
`
`3
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 3 of 5
`
`6,012,007
`
` VARIABLE THRESHOLD
`
`
`GET INHIBIT TIMES
`T1 +T2
`
`60
`
`62
`
`NO
`
`
`
`MEASURE <
`THRESHOLD
`
`?
`TOWARD MIN.
` RESET TIMER
`
`DECREM ENT
`THRESHOLD
`
`
`
`INC REMENT
`THRESHOLD
`TOWARD MAX.
`
`FIG - 7
`
`FUZZY
`TERM
`
`a
`
`b
`
`MEASURE
`
`
`
`YES
`
`64
`
`MEASURE>
`MIN. ACTIVITY
`VALUE
`
`
`
`4
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 4 of 5
`
`6,012,007
`
`FIG-8
`
`DECISION FILTER = MAX.
`YES
`NO
`
`
`TOTAL FORCE > LOCK THRESHOLD
`LOCK TIMER > LOCK DELAY
`
`
`78
`
`
`
`TOTAL FORCE >
`
`TOWARD MAX. YES
`
`INCREMENT FLAG VALUE
`
`76
`UNLOCK THRESHOLD
`
`TOTAL FORCE <
`UNLOCK THRESHOLD
`FLAG VALUE > 0 ?
`
`DECREMENT FLAG
`VALUE TOWARD ZERO
`
`
`
`FLAG VALUE >0 ?
`
`NO
`
`FLAG = CLEARED
`
`FLAG = SET
`
`80
`
`
`
`
`
`RETURN
`
`
`
`110
`
`
`
`INCREMENT
`COUNTER
`
`FIG-10
`
`116
`
`
`
`
`
`
`FILTER
`
`* COUNT > 133
`
`_OR-
`* COUNT >123
`AND
`
`
`CONCENT
`INHIBIT
`
`FINAL
`CONSENT
`
`
`
`RETURN
`
`
`
`112
`
`
`
`DECREMENT
`COUNTER
`
`5
`
`

`
`U.S. Patent
`
`Jan. 4, 2000
`
`Sheet 5 of 5
`
`6,012,007
`
`42
`
`FIG-9
`
`92
`
`94
`
`96
`
`YES
`
`PROCESS ADULT LOCK FLAG
`
`ADULT LOCK FLAG SET ?
`
`YES
`
`LOAD RATING LOW ?
`
`NO
`
`NO
`
`
` YES
`
`LONG TERM AVERAGE HIGH ?
`
`
`
`ANY GROUP MEASURE HIGH ?
`
`LOADRATINGHIGH?
`FUZZYMEASUREHIGH?
`I
`
`INHIBIT DECISION
`-
`TO FILTER
`
`ALLOW DECISION
`TO FILTER
`
`6
`
`

`
`6,012,007
`
`1
`OCCUPANT DETECTION METHOD AND
`APPARATUS FOR AIR BAG SYSTEM
`
`This is a continuation-in-part of U.S. patent application
`Ser. No. 08/566,029, filed Dec. 1, 1995, now U.S. Pat. No.
`5,732,375, issued Mar. 24, 1998, which is also assigned to
`the assignee of the present invention.
`FIELD OF THE INVENTION
`
`This invention relates to an occupant restraint system
`using an occupant detection device and particularly to an
`airbag system having seat pressure detectors in the seat.
`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). In a system
`designed for eifective 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 “VEHICLE OCCUPANT RESTRAINT
`WITH SEAT PRESSURE SENSOR”, and in U.S. Pat. No.
`5,732,375, 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
`distribution, and for inhibiting deployment in certain cases.
`These disclosures teach the use of sensors on the top surface
`of the seat, just under the seat cover, and algorithms espe-
`cially for detecting the presence and orientation of infant
`seats. Both of these disclosures fomi a foundation for the
`present invention and are incorporated herein by reference.
`It
`is desirable, however to provide a system which is
`particularly suited for discriminating 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
`determination of whether an airbag deployment should be
`permitted. Another object in such 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 sensor signal and to decide whether to deploy an
`air bag, 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 air bag.
`A number of sensors, judicially located in the seat, can
`garner sullicient load and distribution information to allow
`
`60
`
`65
`
`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 sensor, 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 of 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 schematic 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 determining 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 load ratings and a fuzzy mea-
`sure;
`
`FIG. 8 is a How 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 INVENTION
`
`10
`
`15
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`25
`
`30
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`35
`
`40
`
`45
`
`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 from the accelerometer and
`for deciding whether to deploy an air bag. An air bag
`deployment unit 18 is controlled by the microprocessor I6
`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 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 microprocessor 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
`
`7
`
`

`
`6,012,007
`
`3
`variable resistor 28 is connected to an A/D 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 issues 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 resistors vary between 10 kohms at high pressure
`and 100 kohms 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.
`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 pressure sensors 28 on its upper surface so that
`the sensors are pressed against the bott.om surface 40 of the
`seat cushion 36. Automotive scat cushions assemblies do 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 sensor to detect a force imposed by the weight
`of a seat occupant.
`The method of operation is illustrated by a series of
`ftowcharts 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 is 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 <50> and decision algorithms are
`run <52>. The algorithm output is filtered to avoid the effects
`of transient events and ultimately a decision is made to allow
`or inhibit air bag deployment <54>. Then either an inhibit
`signal is issued <56> or an allow signal is issued <58>. 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 term 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. Afixed 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 T2 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
`Ilowcharts the functional description of each block in the
`
`10
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`30
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`35
`
`40
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`
`60
`
`65
`
`4
`chart is accompanied by a number in angle brackets <nn>
`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 threshold <64>, and a
`timer is greater than T2 <66>, the threshold is incremented
`<68> and the timer is reset <70>. When the measure is less
`than the minimum activity level <62> and the timer exceeds
`T1 <72>, the threshold is decremented <74> and the timer
`reset <70>.
`
`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.
`08/566,029 and as reflected 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 ever,
`say, 16 sample periods, 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, front group, rear goup 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
`“Adult” 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 Lock Flag is set, the output
`decision will always be to allow deployment. The algorithm
`uses a lock threshold which is above the total force 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 filter 54 is at its
`maximum value, the total force is greater than the lock
`threshold, and the lock timer is larger than the lock delay
`<76>, a flag value is increased toward a maximum value
`<78> and the Adult 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 <82> and if not, whether the total
`force is below the unlock threshold and the flag value is
`greater than zero <84>. If so, the flag value is decremented
`toward zero <86>, and in either case the flag value is tested
`<88>; if the value is above zero the Flag is set <8l)> 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 is determined to be high or low by comparison with
`its variable threshold if one has been computed, or against
`a fixed threshold. The Adult Lock Flag is processed <92>
`according to FIG. 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
`
`8
`
`

`
`6,012,007
`
`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 <102>
`the load rating <104>, or a group measure <1l]6> 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 <108>.
`The final judgment of whether to consent to deployment
`is made in the decision filter as shown in FIG. 10. An up and
`down counter starting at zero and having a maximum count
`of 255 is used. If an allow decision is made <42> the counter
`is incremented <ll0> and if an inhibit decision is made the
`counter is decremented <112>. When the count exceeds 133
`<l14> final consent to deployment
`is granted <1l6>;
`if
`consent is already present, a count over 123 is needed to
`maintain that state to afford hysteresis. When the count falls
`below 123 the consent is revoked and deployment will be
`inhibited. Assuming that the increment size is one count, at
`the 100 ms loop execution rate 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 Flag. Similarly, once the maximum count
`is attained, at least 13.2 seconds are needed to revoke the
`consent.
`
`It will thus be seen that process of determining whether an
`adult size person is occupying the seat is carried out by
`analyzing sensor output with several measures to insure both
`that deployment will be allowed with a large occupant and
`will not occur with a small occupant. Rapid detection of
`large adults is enabled by the total force and load rating
`measures, while dynamic sensor outputs caused by frequent
`occupant movement are managed by the long term average
`measure. The fuzzy measure helps discriminate between
`large and small occupants in borderline cases. The seat
`structure 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. Off 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 for selectively allowing
`deployment according to the outputs of seat sensors
`responding to the weight of an occupant, a method of
`allowing deployment according to 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 first 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 first 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 unlock threshold at a level indicative of 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 a second threshold of the relative weight
`parameter; and
`
`10
`
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`
`40
`
`45
`
`60
`
`65
`
`6
`inhibiting deployment when the relative weight parameter
`is below the second threshold.
`3. The method defined in claim 1 wherein the relative
`
`the
`
`weight parameter is the total force detected by all
`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 term filtering the cumulative average 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 sensors to derive a
`total load rating.
`6. The method defined in claim 1 wherein the relative
`
`weight parameter is a fuzzy val11e 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 fuzzy average and the fuzzy load value to
`obtain the fuzzy value.
`7. The method defined in claim 1 wherein the step of
`setting the lock flag is executed in repetitive loops and
`comprises:
`incrementing a flag value toward a maximum Value in
`each loop when the relative weight parameter is above
`the lock threshold;
`decrementing 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
`zero and clearing the flag when the flag value is zero,
`so that
`the flag value at any time determines the
`minimum time for clearing the flag.
`8. The method defined in claim 7 including:
`enabling the incrementing step only when a decision 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
`decrementing 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 consent is attained by long term filtering of
`the allow decision.
`
`10. The method defined in claim 1 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 decrementing the counter when an allow
`decision is absent;
`establishing an allow threshold; and
`issuing deployment consent when the counter count
`exceeds the threshold.
`
`9
`
`

`
`6,012,007
`
`7
`11. The method defined in claim 10 wherein the allow
`threshold has a first value when deployment consent
`is
`absent and a lower value when deployment consent
`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 function 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 first
`threshold includes varying the first
`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 means for inhibiting deployment
`when a seat is not occupied 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 first 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 threshold 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 11 nlock 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.
`17. 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 programmed to
`determine measures represented by individual sensor
`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,
`
`5
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
`
`60
`
`65
`
`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 flag 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
`bearing an occupant and a bottom surface;
`a support mounting the bottom surface; 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 wherein:
`
`the seat comprises a resilient pad having a top surface for
`bearing an occupant and a bottom surface;
`a support including a panel 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 deployment as
`defined in claim 17 wherein the microprocessor is further
`programmed to inhibit deployment when the relative weight
`parameter is below a second threshold.
`21. Means for inhibiting and allowing deployment as
`defined in claim 17 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 sensor outputs and the microprocessor
`is further programmed to
`average all sensor outputs over a plurality of sample
`events to obtain a cumulative average, and
`long term filter the cumulative average to obtain the long
`term average.
`23. Means for inhibiting and allowing deployment as
`defined in claim 17 wherein the relative weight parameter is
`a total load rating of the sensors and the microprocessor is
`further programmed to
`calculate a load rating for each sensor as a function of the
`dilferc-11cc between the sensor output and a base value;
`and
`
`sum the load rating for all the sensors to derive a total load
`rating.
`24. Means for inhibiting and allowing deployment as
`defined in claim 17 wherein to set the lock flag the micro-
`processor is further programmed to
`periodically increment a flag value toward a maximum
`value when the relative weight parameter is above the
`lock threshold,
`periodically decrement the flag value toward zero when
`the relative weight parameter is less than the unlock
`threshold, and
`set the lock flag when the flag value is greater than zero
`and clear the flag when the flag value is zero, so that the
`flag value at any time determines the minimum time for
`clearing the flag.
`25. Means for inhibiting and allowing deployment as
`defined in claim 17 wherein a decision to allow deployment
`is a preliminary decision, and to make a final consent
`decision the microprocessor is programmed to
`
`10
`
`10
`
`

`
`6,012,007
`
`9
`periodically increment a counter toward a maximum
`count when an allow decision is present,
`netindieaily deet-etnent the ennntet when an allow tleei_
`sion is absent,
`establish an allow threshold, and
`issue final consent when the counter count exceeds the
`tl-n-esliOld_
`25_ Means fnt inhibiting and allowing deployment as
`defined in claim 17 wherein to establish a threshold the 10
`microprocessor is programmed to vary the first threshold
`over time as a function of the relative weight parameter
`when the relative weight parameter is below the first thresh-
`old,
`
`5
`
`10
`27. Means for inhibiting and allowing deployment as
`defined in claim 17 wherein to establish a first threshold
`which is Variable within a defined range the microprocessor
`15 Pfogfamfllcd t0
`set a minimum activity level of the relative weight param-
`star bfllow the dcfincd range’
`increase the first
`threshold when the relative weight
`parameter is above the minimum activity level and
`be10W the first threshold: and
`decrease the first
`threshold when the relative weight
`parameter is below the minimum activity level.
`
`*
`
`*
`
`*
`
`as
`
`az<
`
`11
`
`11