`
`ENGINECONTROL
`
`12.33
`
`| Advance Angle
`
`
`
`Se
`
`a oe
`
`
`
`ama Ae Ny cnt
`‘A
`ee
`uN
`asSeou
`
`ee
`pany)
`
`i
`
`
`
`
`
`istengine
`
`speed;accelerator position:engine“coolant,fuel, and.inlet air"temperatures;=,epochenser
`boost:Bressure,vehiclespeed,controlrack,orcontrolcollarposition{eratcontroloffuelquan-:
` tem onan in-line dieselfuel injectionpump application,
`_ Fuel Quantity and Timing. The: fuel. quantity alonecontrols a compression ignition.
`éngine’s speedandload. The intakeairis notthrottled as inasparkignitionengine.Thequan-
`. tityof fuel'to be deliveredischangedby increasingor decreasing thelength:of fuel delivery:
`timeper injection..Ontheinjection pump,the deliverytiméis controlledbythepositionofthe
`controlrackon in-line pumps andthepositionof thecontrolcollarondistributor-~typepumps.
`An ECU-controlled actiiator is used to move’thecontrol rackorthecollar to increaseor
`dectease thefuel delivery-time. The ECU determinesthe. correct.length of délivery time:
`
`(expressedas a functionofcontreltackorcollar position) using performance niaps‘basedon
`
`engine speedand calculated‘fuelquantity. Corrections and/orlimitationsas functions of
`
`
`1701
`
`1701
`
`

`

`12.34
`
`CONTROL SYSTEMS
`
`
`
`enginespeed, teiperatute,andturbochargerboost pressureareused to modify the delivery
`‘time, In addition,the control rackor collar actuator contains.a position sensorthat provides
`feedback to the ECU on controller position. Ifthe requested position differs from the com-
`manded position,the: ECU continues fo: move thecontroller-yid'the actuatoruntil the com-
`manded andactual position arethesame.
`The start of injection-tinte ofthe fuelat the cylinderis:a functionofthe.wave propagation
`speed. (ie., the speed of sound)of the fuel fromthe fuel injection pumpto. theinjector.
`Because ‘this timerémains a constant, at increasing engine speedthe delivery of fuel atthe’
`cylinder would be delayed with reference to:crankshaft angle. Therefore, the timing at the
`injection pump.must be advancedwith4increasing engineSpee80.that the.start ofinjection
` alage:impactonexaui
`
`NO, emissions, but-éx
`Therefore,precisecontr‘ol ofthestartofir
`
`
`Althoughmanyyeeuse:ihechanical
`
`
`
`spring-loadedtiming,device plunger.Theplungerrotatesthepump’Scollarring“(for distribu-
`tortype:pumps) iintheoppestte:directionof:thepump’s rotation which advances the timing.
`
`1702
`
`1702
`
`

`

`ENGINECONTROL=12.35
`SpeedControl. As was mentionedpreviously,foraCI engine,fuel quantity alone controls
`the engine’s speed andload. Therefore, presuming adequate ‘injected fuel quantity, an
`unloadedClengine can speed upout of control and destroyitself,Becauseofthis, a governor:
`is requiredto. limitthe engine’smaximumspeed,Inaddition, governorsarealso used for low
`idle-and cruise control'to maintain aconstant engine oryehicle speed and meter thecorrect
`fuelfor cold-starting. Fuelis also:controlledas.a functionof speedandboost préssure'to limit
`- smokeleyels, enginetorque,and exhaustgas temperatures.On an-electronicallycontrolledCI
`“engine, the governor's functions are controlled by thefuel delivery systemdescribed prévi-
`
`-ously, Engine spéed is provided byan RPMsensor that:monitorstheperiodsofangular seg-
`mentsbetweenthe reference markson theengine’s flywheelor in thein-lineinjection pump.
`
`-EGR Control. Rerouting ofexhaustgasesinto-the intakeair stteamis knownasexhaust gas.
`-reerrculation (EGR). EGRreducesthe amount of oxygen inthefreshintakecharge while
`
`increasing.its specificheat.Thislowers combustion temperatures andresults m- lower NO,
`_ emissions. However,excessive amounts ofEGR resultin higher emissionsof soot (particu-
`-Jates), CO,and HCsall dueto insufficient: air, Also, the introduction of EGR can have an
`adverseaffecton driveability duringcold-engine operation,full-load operation,atidatidle.It
`‘is best,therefore,to.controltheEGRvalvewith the ECU.Bothpneumatically controlled and
`: solenoid-controlled EGR valvesaréin-lise. The ECU determinies.when and how. much.EGR.
`will occurbasedon enginetemperatureand accelerator position.
`Turbocharger BoostPressure Control. Enginesthat have’turbochargers benelit seals :
`~eantlyfrom‘electronic:boost |‘pressure ‘control. If only-a pheumatic-mechanical ‘wastegate is,
`: used.sonyone boost pressure,pointforthe.entire operatingrange:Isusedto.divert the exhaust
`: conditions because all the exhaustgases must.pass fhe turbine.Theresul EAS
`trnereasedexhaust
`
`: backpressure, more turbocharger work,moreresidualexhaustgas inthecylinders,andhigher
`chatge.air temperatures.
`Bycontrollingthewastegatewith apulse-width-modulatedsolenoidvalve,the wastegate
`eanbeopened at different pressures dependingonthe engine operatingconditions, Theré-.
`fore; onlythelevel of air charge: pressure réquiredis:developed. The electronic control uni.
`usesinformation onengine speed. and accelerator position to reference adatatable andthe
`_ proper ‘boostpressure. (actually, dutycycle. ofthe-control valve) is determined, On systems
`
`
`usingintake manifold: pressure sensors, a closed-loop control,system. can: be:developed. to
`“comparethespecified valuewith the measured value.
`
`.
`
`GlowPlugConirol. Biectroniccontrol ofthe glowplug:duration.can be:hatidledbytheECU
`ora-separate controlunit.Inputfor determiningglow timeis:from an engine coulant temper-
`ature sensor.Atthe end of thespecified glow period;thecontroller turns out the start indica-
`torlightte signalthe driver-thatthe engine can bestarted, Theglowplugs remainenergized
`
`while the starter isengaged,An engineload monitor is usé to‘switchoff the glowprocessafter
`start.To limit theloadsonthebatteryandthe glow plugs, a safety overrideis also used,
`
`12.3.2 Fuel Delivery Systems
`
`~The diesel fuel deliverysystemcomiprises.alow- andhigh-pressureside. On the low-pressure
`sideis thefueltank,fuelfilter, fuel supply pump, overflowvalve, and fuelsupplylines; The
`_high-pressuré sideis initiatediii the plunger and barrelassemblyandcontinues through the
`deliveryvalve, high-pressure injectionlines, andinjectionnozzle.
`Thefuel injectionpump mustdeliverfuel at a pressure between350 and 1200 bar,depend-
`ing on the enginé’s combustionconfiguration. The quantity and. timing of injection must be
`: preciselycontrolled ie-achieve good mixture quality and t6 minimizeexhaust emissions.
`
`1703
`
`1703
`
`

`

`12.36
`
`FuelInjectionProcess. An engine-drivencamshaft (in-line pump)orcamplate(distributor
`_pump)drivestheinjection pump’s plungerin the supplydirection,creating presstre in the
`high-pressure gallery. Thedeliveryvalve.resporidsto theincrease inpressure by ¢opening. This
`‘sends a pressurewayeto the injectionnozzleat the speedof sound, The needlevalve in the
`nozzle-overcomes the spring forceofthe injectionnozzle spring and lifts from its:seat when
`theopening pressure is réacheéd. Fuelis then injected fromthe spray ¢orifices into the:engine’S
`combustion. chamber, The injection process ‘énds with’ the openingofthespill port in the.
`plungerand barrel-assembly.This causesthepressurein thepump chamberto collapse,which
`then.causes the delivery valveto close. Dueto theaction ofthedeliveryvalvereliefcollar, the
`pressure.in the injectionline isreducedto the “stand-by pressure.” The stand-by pressure is
`determinedto ensure thattheinjectornozzle closesquickly to eliminatefuel dribble,andthe
`residual pressure wavesinthe lines preventthe nozzles from reopening.
`
`ABOUTTHE AUTHORS
`GARY C. Hirschijesis chiefengineér, etiginemanagement systems; for the Robert Bosch
`Corp. He:previously held various‘engineering andsales'responsibilitieswithBosch.In his ear-
`lier career, he worked-as-a senior ‘engineer in powertrain developmentforFord tractor-opera>
`tions,andasa'salescnginéer withGTE, and ag:at,engines: in plant:engineering.for GMTruck
`andCoach.
`:
`
`hyRobertBoscitJomPrior to thatshehadbeen an engineeringProject
`
`awaself-tapioyedtechnicalwtiter,butuntit1993,shewasaseniorappli-
`
`1704
`
`1704
`
`

`

`
`
`CHAPTER 13
`TRANSMISSION CONTROL
`
`Kurt Neuffer, Wolfgang Bullmer, and Werner Brehm
`
`RobertBosch GmbH.
`
`
`13.1 INTRODUCTION
`
`InNorth Américaand Japan, 80 to 90percentofallpassenger carssoldhaveautomatic trans-
`missions: (ATs),but inEuropeonly10to 15 petcent ofpassengercarssold have ATs, There
`arétwo main reasonsfor the difference, In Europe,drivers tend to view ATs, comparedto
`manualtransmissions, as detrimentaltodriveability and sesponsible|for @somewhathigher
`fuelconsumption, But implementation ofelectronic¢:controlconceptshas invalidated bothof
`those-argunichts.
`Sincetheintroduction ofelectronictratisthission conttolsunits (TCUs)in the early 1980s
`by Renault and BMW(together with a four-speed transmission: frot. Zahir dfa
`Tee
`Friedrichshafen,or. ZE), the acceptance: ofthe AT rose steeply; even inEurope.
`son, all new ATsaredesigned. with.electronic control. ThemarketforATS is.dividedinto
`stepped:and continuously variabletratisinissions (CVTs).For bothtypes thedrivergetsmiaiiy.
`advantages.In:steppedtratismissions, thesmoothshifts can be optiniized bythereductionof:
`engine torqueduring gearshift,combinedwiththecorrectly matchedoil pressureforthefric.
`tionelements (clutches, brakebands). Thereduction, ofshift shocks,toa,very lowor even ta
`an unnoticeablelevelhasallowedthedesign offive--speedATs wherea'slighilyhigher num-
`berof.gearshifts occur, Intoday’sstandardsystems, the driver‘can choose between:sportand
`economicdriveprogramsby operaling a selector switch;Inhighly sophisticated newer sys:
`“tems, the’selectioncan. bereplaced by. theself-adaptation ofshift strategies.This leads not
`-only tobetter driveability butvalso to asignificant reduction. in fael consumption. Addition-
`ally, 4-wellanatched electronic contre! of the torque converterlockuphelps. to-improve: the
`yield ofthe overall‘system.Bothautomotive,andtyansmission manufacturers benefit:from the
`ent shift‘pharasteristits are:easy‘to. implement in‘software,and rmich adaptation can be
`
`
`data:change, leaving:thetransmissionhardwareandTCU unchanged.The reduc-.
`achievedbr
`
`+ lossesin friction elementsincreases the life expectancy andenablesthe optt
`tion of poy
`“mizationoftransmission hardwaredesign.
`With the-CVT, oneof the biggest obstaclestothe potential reductionin fuel consumption
`byoperatingtheengineat its optimal workingpoint.is the powerlossfrom.the transmission’s-
`éd yieldby. matching
`oil pump. Only with electronic control is it possible to-achievethe requir
`
`theoil mass-stream and. oil pressurefor the pulleysto'the-actual workingconditions.
`‘To guarantee theoverall economic solution.for an electronically controlledtransmission,,
`either:steppedor CVT, theavailabilityofprecision electrohydraulicactuators is imperative,
`
`1705
`
`1705
`
`

`

`13.2
`
`CONTROL-SYSTEMS
`
`.
`
`“
`
`13.2_SYSTEMCOMPONENTS
`
`The componentsofan electronic transmissioncontrol system are a transmission whichis.
`adapted tothe electronic. control requirements andan electronic control unit with corre-
`sponditiy-inputsand:‘sutputs and-attachedsensor elements.
`
`13.2.1 Transmission
`
`The greatest share of electronically controlled transmissions-currently on the market:consists
`offour- orfive-speed units with a torque converter lockup.clutch, commanded by the control
`unit, Marketshare forfive-speedtransmissionsis. continuously 1increasing.With electronically
`controlled transmissions there ate numerous possibilities to substitute: mechanical and
`hydraulic components with. electromechanical or electrohydraulic components. One basic
`methodistosubstitute onlythe shiftpoint control. In aconventional purehydraulic AT,the
`gear shifts are-carried outby mechanical and hydraulic:components,Theseare controlled by”
`a centrifugal governorthat detects the vehicle speed, anda wire cable connected to'the throt-
`fle plate lever,With anelectronic shift point control, on the other hand, an.clectronic.control
`unit detects andcontrols therelevantcomponents. Inthetransmission’s hydraulic control
`unit, mechanical and hydratilic components arereplacedby:electrohydraulic controllingele-
`‘ments, usuallyin the formof electrohydraulicon/off solenoids, This waythe number of
`solenoids,as wellasthecontrollogic; can bevariedover a widerange, Forexample, foreach
`gear, onespecific solenoid can operate the relevantclutch for this gear shift. Alternatively,
`there canbe onesolenoidforeachpear change, whichis switched corresponding.to theshift
`“command.In'this 4way, only. three.solenoidsare reqitiredin a four-speedtransmission: In some
`current. designs, the pears are controlled by a logical combination of solenoid.states. This.
`designneeds onlytwogear-controllingsolenoidsfora four-speedtransmission. For five-speed
`applications,accordingly, threesolenoidsarerequired.(Table 1313)
`
`TABLE 13:1. Example ofa. Geat-Soletioid: Combination for.a Five-Speed.
`‘TransmissionApplication
`
`=
`Slenoid22
`Solenoid'3
`Om on
`Istpear
`.
`~
`Qnd-ceatr
`on:
`off
`Std pear:
`off
`off
`‘Ath gear
`off
`otf
`
`Sthipear off off on
`
`
` _Solenoidd 5
`
`
`
`“The hydraulic présstire is controlledin this basicapplication by ahydraulic proportional
`
`valvewhichis, in turn;
`controlled bya wirecableconnectedto thethrottle platelever. With
`this design, theshiftpoints can be determinedby the electronicTCU,resulting in a wide range
`of freelyselectable driving behaviors regarding the shiff points. It is also possible to-use dif:
`ferentshift maps.accordingto switchorsensorsignals: The influence on driving comfort dur-
`ing gear shifting in thiselectronic transmission control applicationhas importantrestrictions.
`‘The only-possible wayto controlshift smoothnessis with aninterface to the electronic‘engine
`‘management.This:way, the engine output torque is influencedduring gearshifting. Asystem-
`atic wide-rangecontrol of the hydraulicpressure duringand after the gearshift necessitates
`the replacement of the: hydraulic pressure: governor with an electronically’ controlled
`hydraulic. solenoid. This designallows theuseof either a pulsé-width-modulated (PWM)
`solenoidor apressure: regulator, The-choice of which type of pressure. control solenoid to
`useresulisfromthe. requirements. concerning,shitt comfort under all driving conditions, For:
`
`1706
`
`1706
`
`

`

`TRANSMISSION CONTROL
`13.3
`present-daydesigns with high requirementsfor shift comfort during the: entirelife:of the
`transmission,atall temperatures, andwith varying oi]quality, the analog, pressure control
`
`
`solenoidis superiorto the usual PWMsolenoid, providing there is no pressure sensort
`
`
`ation as aguidelinefor pressure regulation,Thisapplicationusuallyuses: one central control-
`
`lingelementinthe transmission forthepressure regulation to control the:shiftquality.
`In other transmission developments, theshift quality is further increasédusing électroni-
`
`
`callycontrollablebrake elements(brake bands) for somespecific
`gearchanges. In thiscase,
`the flywheeleffect of therevolving elementsis limited byanelectroniccontrol ofa brake.
`. bandaccordingtoan algorithmor special timing conditions,
`The mostsophisticated transmissionapplication todateisso designed that overrunning
`
`
`clutchesare eliminated andgearchangesare exclusivelycontrolled bytheelectronic control
`iit with pressureregulator solenoids.’ This application is characterized by extremely high
`
`
`
`demandsontheelectronieTCU concerningreal-time. behavior anddata handling. Therela-
`tionship: between. weight, transmission outline; and transferrable torque has reached.a high
`level. Compared‘to transmissions with overrun cluiches, the necessaryfitting dimensions are
`reduced,
`r
`sclronically controlled ATsusuallyhave an electronically commanded torque
`
`eonverterclutch, whichcan lock up the-torqueconverterbetweenthe:engine output andthe
`transinission,input.‘The tongue Gonvetler.clutehissolivated under certain* driving.conditions
`
`noid,orapressure voulgton‘Lockingupthetorque converter:eliminatesinesofae
`
`
`converter, and the:efficiency of thetransmissionsystemisincreased. This resultsin an even.
`lower fuelFeonsurmption forcars:equipped.with AT.
`
`.
`
`13.2.2 Electronic Control Unit
`Another important componentinelectronic transmissioncontrol-isthe electronte control
`unit,whichis designedaccordingto the requirements of the transmission. andthe‘car cnvi-
`ronments: The electronic’controlunit can’ be divided inte:two main parts: the hardware and
`the:corresponding software.
`Hardware. “The hardware ofthe electronic controlWHiEConsistS.ofthe housing,the phig, the
`carrier for the electronic devices, and the devices themselves.Thehousing, according to.the
`requirements, is available as an unsealeddesignfor ‘applications msidethe passenger com-
`partmentor within the luggage compartment. ‘It isalso possibleto havesealed‘variantsfor
`mounting conditionsinside the engine compartmentor atthe bulkhead.Thematerials for the.
`housingcan beceither various plastics: or:metals: There-are-manydifferent nonstandardized
`housingson themarket.The various outlinesand plug configurations differ, depending upon
`the manufacturer:obthe electronic.unit. Thephig configuration,\.e., the number ofpins and
`‘therequirementsof the automotive inanufacturer,
`
`‘Thenumberot}pinsis‘usually.less than100.Some.control unitmanufacturerstry tostandard-
`ize:theirplugs andhousings throughoutalltheir electronic controlunits, such asengine:man-
`This is importantto simplify andto standatdize.
`agemient, ABS,tractioncontrol, and-oth
`
`the unit productionandthetests during manufacturing,
`Thecarrierfortheelectronic devices isusually.aconventional printed circuit board(PCB).
`
`Thenumberoflayers on the PCB dependsontheapplication. Forunits witha complex device
`structure andhigh demands ‘forelea ‘Omapnetic compatibility,multilaycr applications are in
`usé. Inspecial cases,iis possible1iduseCéfamicsas a carrier. [hereare usually some parts of
`theelectroniccircuit,resistors for example, designed ‘as-a thick-film circuit on the hybrid: In
`this case the electronic unitismanufacturedas a solder hybrid orasabondhybrid with direct-
`bonded integrated circuitdevices. Some single applications existwith-aflex-foil'as a carrier
`for the electronic devices; These:‘applicationsare limitedto veryspecialrequirements.
`
`1707
`
`1707
`
`

`

`13:4
`
`CONTROL SYSTEMS
`
`Thetransmission control. area.requires some specially designedelectronicdevices, in par-
`ticular, the outputstages forthe actuatorsof pressureregulationandtorque:converter’clutch
`control. These actuators’ for pressure control have exiremely- high demands regarding accu-
`racy ofthe actuator current overthe whole temperature range-andunder all conditions inde-
`pendentofbattery voltage and overtheentirelifetime.There aresomeknown applicationsof
`customer-specific integrated circuits or devices, Here, special attention paid to, quality and
`reliability over the entire lifetime ts necessary to meetthe continuously increasing quality
`requiréments ofthe automotivemarket. Currently, there is an increasing:Spread ofsurfacé-
`mourited devicesin transmission control applications. Thisis whytheunitsizeis:continuously
`decreasingdespite an increasing numberoffunctions. .
`Onthefunctional side, the hardware configurationcanbedivided into’power supply,input
`signaltransfercircuits, output stages, and microcontroller, including peripheral components
`and monitoringandsafety circuits (Fig. 13.1).‘Thepower supply:conyertstheveliicle battery
`voltage into a constant ‘voltage required: bythe electronic’ devices. inside ‘the: control unit:
`Accordingly; specialattention must. bepaidto the protection of theinternal devices against.
`destruction by transients from the vehicleelectrical system such as load dump, reverse battery
`polarity,and voltage. peaks. Particular attention is also necessary in the design oftheelec-
`
`oe
`actuator =|.
`output, >actuators
`stages
`m
`
`
`-
` omicra-
`“| ‘controller:
`ae
`
`ignition
`Visatt
`
`
`
`
`
`digital a | “lditalsignals
`inputs "|
`
`‘Interfaces
`,
`
`
`.
`EMS aux |
`‘interface:=="
`
`“| pulse signal
`ees
`|. interfaces:
`speed
`
`
`signals
`2")
`
`T
`“ATE
`
`
`:
`
`.| analog signals
`Se
`PL
`
`
`~
`|.
`interfaces
`‘extemal
`|
`— watchdog |.
`
`
`
`
`
`diagnostics
`| “seta. ~ 7
`| interface tor
`
`
`diagnostics. “|
`
`
`FIGURE13.1 ‘Overview of hardware parts:
`
`1708
`
`
`
`
`
`
`
`
`low.
`signals
`output
`ages
`
`a
`“ECU:
`_
`Bese
`
`1708
`
`

`

` E
`iE}i
`
`be
`
`
`
`
`
`|
`
`|
`
`|
`
`i
`LS
`
`“TRANSMISSION-CONTROL
`
`13.5
`
`tronicground conceptfor the control unit,especially where the electromagnetic compatibil-..
`iheand.REinterferenceAs.concerned,Thisis veryeetopreventundesired‘gearshift-
`: ransfer‘oftheaansignalsike ATF temperature andvoltages according topoten-
`
`
`tiometer statés.The thirdpartis theinterface to otherelectroniccontrol. units, especially: foo
`theengine managementsystem.Herethesinglesignal lines between. the control units will be
`‘increasingly substituted by bussystems like CAN.Thefourthpartis the preparation ofthe:
`transmission-specificsignalsfromthe‘speedsensors.insidéthe tratismission,
`The calculators inside the:control units are usuallymicrocontrollers.The:real-time require-
`mentsand the directly addressableprogram storage siz ofthe selected mictdécontrollers are
`
`determined by thefunctions ofthetransmissi
`and the car environment, In present
`
`applications, either.8-bit or 16-bit microcontrollers are in use. There are systems
`with
`3
`mictocontrollersindevelopmentfor pew,highly sophisticated control systems:withincreasing
`functional andextremereal-timerequirementsoriginatingfrom the transmission concept.
`Thememory devicesfor program and dataare usuallyEPROMS,Theirstoragetaj acity1s, In.
`present applications, upto.64 Kbytes. Future applications will necessitate storage §i7es upto
`
`128Kbytes,The failurestoragesfor diagnostics,and thestorage:for adaptive dataare mcon-
`
`ventionalapplications,battery voltagé-suppliedRAMs,Theseareincreasingly beingreplaced
`
`by.EEPROMSs.
`
`-Theré:are usually watchdog.circuitsin various: configiirationsiin usetégarding safety and
`monitoring. These:can be either-a, second; Jow-petformatice: mie ocontroller, a customer
`“specific circuit,or a cireuitwithcommon availabledevices. Theoutputstapes can be divided
`inte high*power stages forthe transmission-actuator control andlow-powerStages like lamp
`drivers orinterfaces to otherelectrénic controltinits.The low-~-power output stages aremostly
`conventionaloutputdrivers eitherisingleorin:‘multiple applications,whicharemainlypro-
`tected:against shortcircuits:and voltage overloads,
`For thetransmission. solenoid control, special-output stages are’ necessary, and they are
`“specializedfor.operation with induetivéactuators,The pressure regulation:during shifting in
`-some applications. réquires |hi htaccuracy and. cutrent-regulated output stapes are needed.
`
`"Thesearemainlydesigned as:customer-specificdevices,The typeandnumber:ofsolenoid out-
`‘put stages dependonthecontrolphilosophyofthetransmission: they3atégenerally of a spe-
`cial design forspecific transmissionapplications, Duringthep eparationofthéspeedsensor
`
`signals,attentionmust be:paid tothe electromagnetic compati ility and tadiofrequencyintér-
`
`_ ference conditions.
`-Software.. Thesoftware within theeléctronic transmissioncontrol system is gainingineteas-
`_iilg importance due to thejincreasing‘numberoffunctionswhich, in turn, requires increasing
`
`software-volume,Thesoftwarefor the controlunitean.be dividedintotwoparts: the program
`and. the data. Theprogramstructure is defined by thefunctions, The dataarespecific for the:
`
`relevant prograin.parts andhavetobe fixed duringthecalibration stage. The most difficult
`software: t quirements|result fromthereal-Uime: conditions comingfrom,the. transmission,
`
`design. Thisis also the maincriterion for.thé seléctionofthemi rocontroller (Fig.13.2).
`
`Theprogramis generally made upin several parts;
`‘Softwareaieto the specialmicrocontrollerhardware;&g. TiO preparation.and filter,ms
` -forthecontrollerperipheraldevices,and.internal softwaresenviceslikeoperatingsystems,
`« Softwarecomingfromthe defined.functions, originating:from specific'transmissionandcar
`functions,
`i
`-«Parts concerningsafetyfunctionslike outputswitch-off, substitutevaluesfor'theinput sig-
`nals, andsafety-statesofthemicrocontroller environmentinvaseoffailures,Depending on
`the: requirements,there can be-a software watchdogora hardware-configured watchdog
`‘cireuitimuse,The watohdoginstructionis also part of thé securitysoftware.
`
`
`
`1709
`
`1709
`
`

`

`13.6
`
`CONTROESYSTEMS
`
`initialization:
`ofmicrocontroller.
`
` _
`
`inputsignals
`
`“|
`
`and controlunit
`
`
`‘preparation [7
`
`
`
`calculation =|
`
` | output:
`
`signal,
`|translation...
`
`functions:
`
`“FIGURE:13.2:.Software structureaverview.
`
`» Diagnostic and communication software.for theself-test ofthe:contrel unit'and alsothetest
`of the control unit environment.
`These.functions:are:related to:the defiried functionsoftheelectroniccontrolot aystemParts
`
`
`numberof# powerful,cost-effectivemicrocontrollers
`
`ity of memorycomponents with largerstor
`makingitpossible.touse a higher progra
`an ingeniousstructureof software mode
`ide gear shifting with
`be followed by an effective distribution offu
`
`related time requirementsand event manager
`istructure improves
`
`thefunctionoftheelectronicTCU because of th dlingoftime-criticalfne=
`
`
`tions during gearshifting.
`Hi
`.
`——
`i
`
`1710
`
`1710
`
`

`

`TRANSMISSIGN'CONTROL
`13.7
`The second. soitware ‘part, data,.can be dividedinto fixed data, whichis related to fixed’
`attributes: ofthe system; é.8,, thenumberof actuators,and calibration datafor system tuning.
`
`‘The calibrationdatacanbe adapted tochangingparametersof the systemsuchas'the engine,
`vehicle;andtransmission characteristics. The: fixing ofcalibration data takesplace during the
`tuningstageofthe vehicle and has to be redeterminedforeach: typeofvehicle andtransmission.
`With some applications, the calibrationdata’ ate addedto.a basic: program. duringthe vehicle
`productionaccordingtodifferenttypes of cars bytheso-calledend-of-lin programming.This
`‘meansthattheunitscanbe programmedwiththe calibration data with closed housingsbya spe-
`cial interlace.Theshare of
`software developmentiin relation to thetotal.development|titeis
`increasing continuously.Therequirementsforreal-time behaviorandtmemorysizearerisingin.
`
`accordancewiththe considerablly inereasing demandsfor shiftcomfort.andself-“learning func-
`tions. This requiresan ingenious.structure of the:softwareand an event-related distributionof
`softwaremodels, especiallyduringgear:shifting.‘The tisingsoftware complexitywith-simultane-
`ouslyincreasing qualityrequirementscauseshigher demandsfor softwarequalitycontrol.
`
`13:2.3.. Actuators
`Electrohydraulic actuators are importantcomponents:of:the electronictransmissioncontrol
`systems.” Continuously:operatingactuators areusedto: modulate:pressute, while: switching
`actuators functionas supply anddischargevalves for shittpointcontrol.‘Figure 13,3: provides
`-abasicoverview ofthese:types:ofsolenoids;
`Important qualities for the tiseof actuators in ATs are low hydraulicresistanceto achieve
`highflowrates, operation’ lemperature range from —40to +150 °C,smallpowerloss, mini-
`nized heat dissipation
`intheECU's.outputstages, small size and low weight, highest reliabil-
`ity’ in heavily contaminated. oils,maximum: accuracy and repeatability overlifetime, short:
`
`reactiontimes, pressure rangeup to:2000 kPa, maximum:vibration acceleration of300 m/s’,
`andhigh numberof switch operations.
`
`_ Averyimportantaspectisthat the:hardware and-softwaré: of.the ECUbe developed, tak:
`ing into accounttheelectrical specifica ionsof thesolenoid to obtainan: optimized complete:
`systemconcerning performanceand. cost.”62Bor furtherdetailsin design andapplication,refer.
`to. Sec..10.3;5.
`
`It shouldbe notédthatthese characteristics canbe'variedoverawider.angeandthatmanyother
`typesofsolenoidsexistorateindevelopment
`forthespecialRequirementsofnew applications.
`
`'
`
` 13.3 SYSTEMFUNCTIONS
`Furictions‘caibe designated at systemsfunetionsif the:individualcomponents. of the total:
`‘electronictransmissioncontrolsystem cooperate efficiently toprovidea désired béhavior of
`‘the transniissionarid thevehicle, Thérearédifferentstapesof functionality which havediffer¥
`
`ent effects on drivingbehaviorand shift characteristics (Fig. 13:4)..In, general, there is an
`increasing complexityofthe system relatingto-all components to improve:thetranslationof
`driverbehaviorinto. transmissionaction. That méansthatthe expense o actuators, sensors,
`‘atidlinks:to otherControlwitsis increasing, as is the expense oftheTCUsoftwareand hard-
`warein the-case of high-level requirementsregarding driveability andshift comfort. Figure:
`13,4 shows threemainaréas. These:will bediscussed:in detail in the followingg material.
`
`13.3.1 Basic Functions
`‘The basic:functions-ofthe.transmission controlatethe shift pointcontrol, the lockup control,
`enging torque:controlduring:shifting, related safety.functions,and diagnostic functions for.
`
`1711
`
`1711
`
`

`

`Switching actuators
`
`Continuous operationactuators
`
`|Variabte Pressure :
`‘Solenoid
`
`L
` [ndrmal
`
`
`
`
`
`
`
`
`
`high.
`
`
`High Flow(7000cm3/min, 400KPa) |
`LowFlow (1300cm3/min, 400KPa)
`
`
`
`FIGURE 13.3 'Blectrohydrauliciactuatorsfor automatic-transmissions:
`
`
`
`
`
`
`
`
`| Settleaming adaptation
`
`
`{of shift strategy to driving:
`
`
`
`- |behaviorand
`driving situation
`
`[Seltleamingadaptationof |
`
`
`
`
`[shift characteristic according
`
`
`{to variableJoadconditions_
`
`
`
`
`
`‘|Basicfunctions
`
`
`‘|| for-excellentgear change
`
`
` lopment progress
`FIGURE13.4 Relationshipbetweendrivingcharactetistic and function complexity,
`
`
`
`_, Funetional contents
`
`
`
`
`
`
`
`"Acceptanceey
`
`
`
`
`13:8.
`
`1712
`
`1712
`
`

`

`‘ignition. =
`
`Veit
`
`
`
`positionsy
`
`
`
`.
`
`Intarfades’
`,
`
`TRANSMISSION CONTROL
`
`13.9:
`
`
`
`
`
`
`
`ee a
`|
`‘solenoid f=
`Shitting:
`diver
`poe
`stages; =.”~ solenoids
`
`micro- |
`“controller |
`
`
`
`KD
`
`
`
`
`EMS. >.
`interface:
`.
`
`_|speedsignals: Interfaces
`
`
`wing=——# digital:|limphome:
`
`
`cons
`‘signals
`
`
`
`output
`engine
`
`
`es
`torque
`analog sigrials
`anes
`:
`reduction
`
`
`
`ree
`Tay.
`|
`
`
`
`external:
`interfaces |
`
`ent | watehdag
`
`_Sétial: fo
`
`
`
`|. interface-for= |)
`
`diagnostics
`
`“ATE
`
`:
`
`Kline
`Leline
`
`“FIGURE 13.5‘Structure‘of'a basictransmission electronic canttdl unit.
`
`vehicle service, The pressurecontrolintransmissionsystems with:electricaloperating possi-
`I
`during
`andoutsideshiftingcan also beconsideredasabasicfunction.
`
`é
`'yinputs. andoutputs-as wellas the block diagramofanelec-
`=
`
`tronicTCU suitable for thebasic functions.
`ShiftPointControl. Thebasic:shift point control uses shift maps,which:aredefinedin data
`intheunit memory.Theseshiftmapsare:selectable ver aWide3Tange.Theshift.‘point.imita-
`
`
` ‘noiseemission,n Theinputsoftheshiftpoint:determination ;
`eratorpedalposition,and thevehicle:speed (determined bytthetranstissionoutputseen),yi
`
`Figure 13.6 shows-4 typical‘shift:map.application ofa four-speed transmission.
`,
`‘To8 PreventaedfrequentsShitting‘betweentwo gears,a.hysteresisbetweenthe.upshift
`
`Dusieress18 determine by
`the:desired
` ECUreleasesthe shiftbyactivatingtherelatedactuators,This: can’putvadirectshiftinto the
`
`1713
`
`1713
`
`

`

`13.10
`
`CONTROLSYSTEMS
`
`E-Progratn (Economy)
`
`
`
`load
`
` Engine
`
`Outputspeed ng,x 1000
`FIGURE 13.6. Shift characteristics ofa four-speedapplication.
`
`target gear or by a-serial activation of specific actuatorsin a fixed sequencetothe target'sgear,
`depending onthetransmission hardware:design.
`
`Lockup: Control/Torque Converter Clutch.® “The torque converter dutch connects both
`functional componentsofthe hydraulic converter,thepump. andtheturbine:The lockup of
`the clutch reduces the power. losses.comingfromthe torque.converter: slip.Thisisa perma-
`nentslipbecauseitis necessary in principle to-have-a-slip. betweenthe pumpwheel arid the
`turbineto translate torquefrom theengine outputto thetransmission input; To increase the.
`efficiencyof the lockup,it is necessary to closethe clutchasoften as possible. On theother
`hand, the torqueconverteris an important component to prevent vibrations ofthe power-
`train.The activation ofthelockupis, therefore, a.compromise betweenlowfuel consumption
`and high driving comfort.The‘shiftpoints ofthelockuparedeterminedin thesamewayas the
`determinationof theshift pointin the gearshift point control. Usuallythere is one separate
`characteristic curve forthe lockupfor each gear.'To prevent.powertrainvibrations,it is advis-
`able to.openthe lockup-during coastingto use the dampingeffect ofthe torque converter. In
`the caseofa highpositive gradientof the accelerator pedal with low engine speed, the con-
`verter-‘clutch:hasto open to use'the:torque gain oftheconverterfor better'acceleration.of the
`car. In some applications, the lockupis opened during’shifting forimproved shiftcomfort.
`After shifting, the lockup ean beclosedagain, Whendrivingin first gear, the lockupisusually
`open, because the time:spentin.first gearisusually very low and,there