885122 NewGeneration OfElectronic ControlUnits ForCommercial VehicleAutomatic Transmission Systems ManfredSchwab,KurtVenger ABSTRACT Intheautomatic transmissions sector, theuseofmicrocomputer control units hasmadeitpossible tointroduce sys­ temswithpreviously unattainable per­ formance characteristics intermsof economy andeaseofoperation. With thenewgeneration ofelectronic con­ trolunitsfortheZFEcomattrans­ mission system further improvements by meansofnewfunctions suchasclosed loopshiftcontrol anddiagnostic ca­ pability areintroduced. Theincreas­ ingcomplexity willplacegreater em­ phasis onsupport duringthecommis­ sioning phase andtheservice ofthese systems. Thenewgeneration ofelect­ roniccontrol unitstherefore com­ prises arangeofdevices suchas portable diagnosis terminals and laptop-PC foracomputer-based ap­ plication ofthesystem. 1INTRODUCTION Inthelasttenyears enormous pro~ gresshasbeenmadeinimproving the drivelinetoenhance fueleconomy and driving comfort, especially inbuses. Improved trartsmission.systems, espe­ cially improved control systems have played anessential roleinthispro­ cess.Without theuseofelectronicsthiswouldnothavebeenpossible. A thirdgeneration ofelectronic control unitsisabouttobeintroduced into theZFtransmission Ecomat-. range, and thiswillmeanafurther improvement totheoverall system. Thefollowing paperpresents theoverall concept of thisautomatic transmission system, withspecial emphasis ontheelect­ roniccontrol system.2TRANSMISSION SYSTEM TheECOMAT system (Fig.1)comprises a rangeofpowershift transmissions with thefollowing special features: -4,5,6and7speedversions -inputtorque upto1,600Nm, 1,200ft-lbs -compact, lightweight design -numerous options available (PTOs, transfer cases, angledrives) -integrated hydrodynamic primary retarder -amicroprocessor control system whichpermits flexible adaptation to arangeofservice conditions Development workontheEcomat range beganinthemidSeventies, afterin­ tensive market research anddiscus­ sionswithvehicle manufacturers and endcustomers. Twodecisions were takenatthattimewhichhavesub­ sequently proved tobecorrect, and whichhaveledtoanewtransmission system whichmakesuseofallthe latesttechnology: Fig.1:ZFAutomatic Transmission HP500Range 2.239Downloaded from SAE International by Columbia Univ, Monday, August 20, 2018-flexible transmission design with variable number ofspeeds andratios -theuseofanelectronic-hydraulic control system Aswellasthefunctional advantages, anelectronic-hydraulic systemalso simplifies therangeandnumberof mechanical andhydraulic transmission parts. Thisisamajoradvantage for boththecustomer andthemanufac­ turer. 3THEELECTRONIC CONTROL SYSTEM Theprincipal functions oftheelect­ roniccontrol system are: -shiftpointcontrol -lock-up clutchcontrol -gearchange sequence control -pressure modulation control -protection against malfunctions and operator error.selects thevalues tobesenttothe transmission. Thesevalues arepassed ontothetransmissions hydraulic sys­ temviaelectro-hydraulic converters suchassolenoid valves andpressure regulators. Fig.2showsanoverall viewofthesystem anditsconstituent parts. Withtheexception ofpressure modul­ ationcontrol, theprincipal functions mentioned abovewereallincluded in thefirstgeneration ofelectronic control unitswhenproduction started in1978.Whenmicrocomputer controls wereintroduced in1982apressure modulation valvewasaddedtocontrol thepressure, andthisallowed afar higherlevelofshiftcomfort tobe achieved. Thethirdgeneration now permits further significant functional improvements, themostimportant of whichare: -Adaptive gearchange characteristics Inordertoperform thesetasks,all relevant operating parameters suchas shiftleverposition, engine load, speedetcarepicked upbysensors and transmitted totheelectronic control unitintheformofelectrical sig­ nals.Themicrocomputer inthecontrol unitprocesses thisinformation ac­ cording toapreset program andthenFormerly, gearchange points were onlyrelated tothesetting ofthe accelerator p