820920 Transmission Controls ApplicationsElectronic forOff-Highway A.S.Farber JohnDeereProductEngineering Center Waterloo, IA ABSTRACT Thereasons fortheverywideinterest inelectronic can· trolofvehicletransmissions arepr13sented andthemIcro­ computer controlofJohnDeerescraper transmissions is described. Transmissions byothermanufacturers arelisted anddiscussed.Themicrocomputer-controlled transmission onthe Deere762Aand862Scrapers (Figure1)isanexampleofthe stateoftheart.Theelectronics wasdesigned byDean HeinooftheJohnDeereProductEngineering Center.These self·loading scrapers haveaslx·speed, powershifttrans· missionwithalockable torqueconverter. Manyvehicle parameters areusedindetermining thetransmission state ateachpointinthevehicleoperating cycle. Fig.1-JD862Scraper THEREHAVEBEENMANYINVESTIGATIONS oftheuseof elecfronlcs tocontrolthetransmissions ofbothon·andoff· roadvehicles. Thosemostrecentlyreportedusemicrocom· puterstoreplacethehydraulic andmechanical logicofthe olderautomatic transmissions. ItIslikelythatallofthemao jarvehicleandtransmission manufacturers haveatleasta prototype systemundertest. Thiswidespread Interestinelectronics Isduetothe following reasons: •Inordertoimprovevehiclefueleconomy andproductivity, transmissions havebecomequitecomplex. Manygear ratiosandalockingtorqueconverter givetheoperatora complex choiceoftransmission states. ..Thevehicleoperator maybeskilledorinexperienced, freshortired,withmanyconflicting reqUirements forhis attention. HeIsnotlikelytobeabletochoosetheop· tlmumtransmission stateinallsituations. toTheoptimum shiftingofatransmission Isafunctionof manyoperating characteristics ofthepowertrainand thevehiclemission. Thesignalswhichrepresent these characteristics aredifficulttoacquire,communicate, process andcombine Inanybuttheelectronic domain.Duetotheroughterraininwhichthesevehiciesare utilized,theoperator's seatissuspended andmanyofthe frequently usedcontrolsaremounted Inthearmrest,which moveswiththeseat (Figure 2).Havingthearmrest-mounted controls movewiththeseatisveryconvenient forthe operator butwouldmakemechanical controloverthe transmission quitecomplex. Fig.2 -Armrestcontrols 235Downloaded from SAE International by Purdue University, Tuesday, August 21, 2018Fig.6-EMCtestinginmineToidentifyandeliminate weakcomponents, anexten­ sivereliability growthstagewaspartofourdevelopment ef· fort.Astandard testIncluded cyclicvariation of temperature, humidity, voltageandappliedsignalsfor100 days.EMItestingwasperformed atboththecomponent and complete vehiclelevel.Sincethescraperistoolargefor mostanechoic chambers, alargeunderground minewas utilizedforthevehicletests.Figure6showsatestofthe sensitivity oftheentirescraper systemtohighfields generated inthemine.appliedforashorttime.Thisassurespromptpull-in.Thedu­ tycycleisthenreducedtotheminimum neededtoholdthe armatures inplacewiththethenoccurring vehiclevoltage. BythismethodweavoidhavingtoregUlatetheonetofive amperes ofcurrenttothesolenoids andmaintain low dissipation Inallcomponents. Fig.5 -Insideofcontroller Gu, S~I.CllanCShHl ~t.... Salenald.a Can.c,le, Hold1lI1ilenNtec~up AulalManualTSwilchRtac~upa lndlca'af Foal L I»th'elll.L ESIOll., OulpulSpe.d Inl.,lack0 RFig.3.Shiftpattern TheblockdiagraminFigure4showsontheleftthein· putstotheprocessor fromtheauto·manual modeswitch, gearselector, fuelpedalswitch,elevator controlswitch, groundspeedsensorandshiftinhibitpedal.Ontherightare theoutputs tothesixtransmission controlsolenoids, the reversewarninghorn,thestarterrelayandthedigitalgear display.The2Kbyte memory externaltothe8035processor storesalloftheinstructions, including different shiftpoints foreachupshiftanddownshift, depending onwhetherthe vehicleisintheloadortransport mode.Acomplete descrip· tionofthecontrollogicismuchtoolengthytoIncludehere.Duringusetheoperator caninstructthecomputer to shifttothegearhedesiresundermanualcontrol.Orinthe automatic mode(Figure3),theprocessor selectstheop· timumgearandtorqueconverter clutchcondition, usingthe operat