technicaltraining. productinformation. g12chassisand
TRANSCRIPT
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Technicaltraining.Productinformation.
BMWService
G12ChassisandSuspension
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Generalinformation
Symbolsused
Thefollowingsymbolisusedinthisdocumenttofacilitatebettercomprehensionortodrawattentiontoveryimportantinformation:
Containsimportantsafetyinformationandinformationthatneedstobeobservedstrictlyinordertoguaranteethesmoothoperationofthesystem.
Informationstatusandnational-marketversions
BMWGroupvehiclesmeettherequirementsofthehighestsafetyandqualitystandards.Changesinrequirementsforenvironmentalprotection,customerbenefitsanddesignrendernecessarycontinuousdevelopmentofsystemsandcomponents.Consequently,theremaybediscrepanciesbetweenthecontentsofthisdocumentandthevehiclesavailableinthetrainingcourse.
Thisdocumentbasicallyrelatestolefthanddrivevehicles.Furtherdifferencesmayariseastheresultoftheequipmentspecificationinspecificmarketsorcountries.
Additionalsourcesofinformation
Furtherinformationontheindividualtopicscanbefoundinthefollowing:
• Owner'sHandbook• IntegratedServiceTechnicalApplication.
Contact:[email protected]
©2015BMWAG,Munich
ReprintsofthispublicationoritspartsrequirethewrittenapprovalofBMWAG,Munich
TheinformationcontainedinthisdocumentformsanintegralpartofthetechnicaltrainingoftheBMWGroupandisintendedforthetrainerandparticipantsintheseminar.RefertothelatestrelevantinformationsystemsoftheBMWGroupforanychanges/additionstothetechnicaldata.
Contact:SebastianRiedelTel.:+49(0)8938265044E-mail:[email protected]
Informationstatus:June2015BV-72/TechnicalTraining
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G12ChassisandSuspensionContents1. Introduction.............................................................................................................................................................................................................................................1
1.1. Developmentcode...............................................................................................................................................................................................11.2. Chassisandsuspensioncomparison....................................................................................................................................11.3. Overviewofchassisandsuspension.....................................................................................................................................2
1.3.1. Highlights..........................................................................................................................................................................................3
2. Axles.....................................................................................................................................................................................................................................................................52.1. Frontaxle............................................................................................................................................................................................................................5
2.1.1. Versionsofthefrontaxlesupport..............................................................................................................82.1.2. NotesforService..................................................................................................................................................................8
2.2. Rearaxle...........................................................................................................................................................................................................................112.2.1. NotesforService.............................................................................................................................................................12
3. AirSuspension.............................................................................................................................................................................................................................163.1. Airsupplysystem.............................................................................................................................................................................................19
3.1.1. Technicaldata........................................................................................................................................................................233.1.2. Solenoidvalveblock...................................................................................................................................................24
3.2. Airsuspensionstrut......................................................................................................................................................................................253.3. Rideheightsensor..........................................................................................................................................................................................273.4. Operatingstrategy...........................................................................................................................................................................................29
3.4.1. High level.......................................................................................................................................................................................333.4.2. Normal level..............................................................................................................................................................................343.4.3. Sport level....................................................................................................................................................................................35
3.5. NotesforService...............................................................................................................................................................................................363.5.1. Liftingthevehicle............................................................................................................................................................363.5.2. Transportmode...................................................................................................................................................................373.5.3. Bleedingtheairsuspension...........................................................................................................................373.5.4. Fillingtheairsuspension....................................................................................................................................37
3.6. Systemwiringdiagram.............................................................................................................................................................................38
4. Brakes............................................................................................................................................................................................................................................................404.1. Servicebrakes........................................................................................................................................................................................................42
4.1.1. Brakedesign............................................................................................................................................................................424.1.2. Pedalmechanismmounting...........................................................................................................................43
4.2. Parkingbrake............................................................................................................................................................................................................444.2.1. Functions.......................................................................................................................................................................................474.2.2. Braketeststand.................................................................................................................................................................48
4.3. Serviceinformation.........................................................................................................................................................................................494.3.1. Servicebrakes.......................................................................................................................................................................494.3.2. Parkingbrake..........................................................................................................................................................................50
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G12ChassisandSuspensionContents5. Wheels/Tires.................................................................................................................................................................................................................................51
5.1. Puncturedetectionsystems............................................................................................................................................................525.2. TirePressureMonitorRDCi.............................................................................................................................................................52
5.2.1. Wheelelectronics............................................................................................................................................................54
6. DrivingStabilityControl.............................................................................................................................................................................................566.1. DynamicStabilityControl(DSC)...............................................................................................................................................59
6.1.1. Hydrauliccircuitdiagram.....................................................................................................................................616.1.2. Functions.......................................................................................................................................................................................626.1.3. Systemwiringdiagram............................................................................................................................................64
6.2. Steering.............................................................................................................................................................................................................................666.2.1. Steeringwheel.....................................................................................................................................................................676.2.2. Steeringcolumnadjustment.........................................................................................................................686.2.3. Versionoverview................................................................................................................................................................696.2.4. IntegralActiveSteering..........................................................................................................................................716.2.5. Serviceinformation.......................................................................................................................................................786.2.6. Systemwiringdiagram............................................................................................................................................80
6.3. ElectronicDamperControl(EDC)...........................................................................................................................................856.3.1. Shockabsorberdesign..........................................................................................................................................856.3.2. Systemoverview...............................................................................................................................................................876.3.3. Electricalshockabsorbercontrol...........................................................................................................89
6.4. Anti-rollbar..................................................................................................................................................................................................................926.5. Standardsuspension...................................................................................................................................................................................94
6.5.1. Chassisandsuspensionsetup..................................................................................................................946.6. ActiveComfortDrive....................................................................................................................................................................................95
6.6.1. Predictivecontrol.............................................................................................................................................................986.6.2. Electricactiverollstabilization(EARSV).................................................................................1026.6.3. Controlstrategy..............................................................................................................................................................1096.6.4. Systemwiringdiagramofelectricactiverollstabilization
EARSV...........................................................................................................................................................................................112
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G12ChassisandSuspension1.Introduction
1
1.1.DevelopmentcodeThenewBMW7SeriesG12willbelaunchedonthemarketfromOctober2015.
Intermsofthechassisandsuspension,thenewBMW7Seriesoffersincreasedcomfortwithoutanycompromisesindrivingdynamics.
1.2.ChassisandsuspensioncomparisonComponent F01/F02 G12Frontaxle Double-wishbonefrontaxle Double-wishbonefrontaxleFrontsuspension Steelsprings AirsuspensionFrontdamping ElectronicDamperControl
(EDC)ElectronicDamperControl(EDC)
Anti-rollbar,front Conventionalorhydraulicactivestabilizer(ARS)
Conventionalorelectricalactivestabilizer(EARSV)
Rearaxle Five-linkrearsuspension Five-linkrearsuspensionRearsuspension Steelspringsorrearair
suspension(optionalequipmentintheF01)
Airsuspension2axle
Reardamping ElectronicDamperControl(EDC)
ElectronicDamperControl(EDC)
Rearanti-rollbar ConventionalorhydraulicactivestabilizerARS
ConventionalorelectricalactivestabilizerEARSV
Frontbrake Brakediscsuptodia.348mm Brakediscsuptodia.395mmRearbrakes Brakediscsuptodia.345mm Brakediscsuptodia.370mmParkingbrake Drumbrakeswith
electromechanicalparkingbrakeEMF
Discbrakeswithcombinedbrakecaliperfortheelectricparkingbrake
Wheels/tires Run-flattires(RSC) NormaltiresTirePressureMonitor(RDC) RDC RDCiSteering ElectronicPowerSteeringor
IntegralActiveSteeringElectronicPowerSteeringorIntegralActiveSteering
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G12ChassisandSuspension1.Introduction
2
1.3.Overviewofchassisandsuspension
OverviewofchassisandsuspensionintheG12
Index Explanation1 Airsuspensionstrut,frontaxle2 12Vbattery(forEARSV)3 Brakeservo4 Steeringcolumnadjustment5 Steeringwheel6 Airsuspensionstrut,rearaxle7 Five-linkrearaxle(HA5)8 Rearaxleslipanglecontrol(HSR)(optionalequipment)9 ElectricactiverollstabilizationrearEARSV(optionalequipment)10 Pressureaccumulator2liters11 Airsupplysystemoftwo-axleridelevelcontrol12 Pressureaccumulator4liters13 Discbrakewithintegratedparkingbrakefortherearaxle
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G12ChassisandSuspension1.Introduction
3
Index Explanation14 DynamicStabilityControl(DSC)15 Discbrakeforfrontaxle16 Double-wishbonefrontaxle17 ElectricactiverollstabilizationfrontEARSV(optionalequipment)18 ElectronicPowerSteering(electromechanicalpowersteering)(EPS)
ThefollowingtableshowsacomparisonofthechassisandsuspensionontheG12.
G12Rear-wheeldrive Four-wheeldrive
Wheelbase 3210mm 3210mm
Turningcircle* 12.8m 12,9m
Groundclearance 135mm 135mmMaximumvehicleheight 1505mm 1505mmMinimumvehicleheight 1475mm 1475mmVehicleheightatnormallevel 1485mm 1485mmVehicleheightathighlevel 1505mm 1505mmVehicleheightatsportlevel 1475mm 1475mm
*Theturningcirclevaluesrefertovehicleswithbasicsteering.
1.3.1.HighlightsThefollowingtableshowsthedifferentequipmentspecificationsintheareaofthechassisandsuspensionfortheG12.
Systems Basicchassisandsuspension
IntegralActiveSteering
ActiveComfortDrive
ElectronicPowerSteering(EPS) XEPSwithvariablerackgeometry XRearaxleslipanglecontrol(HSR) XTwo-axleridelevelcontrol XElectronicDamperControl(EDC) XFrontaxleanti-rollbar XRearaxleanti-rollbar XElectricactiverollstabilizationfront(EARSV)
X
Electricactiverollstabilizationrear(EARSV)
X
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G12ChassisandSuspension1.Introduction
4
Systems Basicchassisandsuspension
IntegralActiveSteering
ActiveComfortDrive
Wheelaccelerationsensors
X
StereoKAFAScamera XAuxiliarybattery(12 V) X
Thefollowingoptionalequipmentisavailableinadditiontothebasicchassisandsuspension:
• IntegralActiveSteering• ActiveComfortDrive
Bothequipmentoptionscanbecombinedwitheachotherandareavailableforalldrivevariants(alsoxDrive).Itwaspossibletoreducethecarbondioxideemissionsandincreasethecontroldynamicsthroughcompleteelectrificationofthetwooptionalequipmentsystems.Inthecustomer'sperception,thisisexpressedinalowerfuelconsumptionwithincreasedcomfortaswellasasportierdrivingfeeling.
Thedrivercaninfluencethecontrolcharacteristicsofthedifferentsuspensioncontrolsystemsbymeansofthedrivingexperienceswitch.FurtherinformationonthisisprovidedintheTechnicalTrainingManual“G12DriverAssistanceSystems”.
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G12ChassisandSuspension2.Axles
5
2.1.FrontaxleThedouble-wishbonefrontaxleoffersoptimumalignmentofthecamberofthefrontwheelsinrelationtotheroadwayineverydrivingsituation.Duringthecompressionandreboundmovements,awheelthereforealwayshasexactlythecambervaluethatguaranteesoptimumtransferofcorneringforcesinrelationtotheroadway.Thisensuresexcellenttirecontactwiththeroadandthetireisabletotransferhighlateralforces.Theattainablehighlateralaccelerationforcesarethuspossiblewithouttheotherwisenecessaryfirmchassisandsuspensionsetup.
Withthedouble-wishbonefrontaxle,theshockabsorberdoesnotperformanywheelcontroltasks.Thismeansthattheshockabsorberarepracticallyfreeoflateralforcesandcanreactsensitivelytoroadbumps.
Sincethedouble-wishbonefrontaxlehasasmallkinematicleverarm,disturbancevariablessuchasroadjointsorpotholesgenerateonlyasmalltorqueaboutthesteeringaxis.
Thesumofalladvantagesmeansthatthedouble-wishbonefrontaxlemakesitpossibletoresolvetheconflictofgoalsbetweencomfortandsportiness.
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G12ChassisandSuspension2.Axles
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OverviewoffrontaxleonG12withxDrive
Index Explanation1 Supportbearingonairsuspensionstrut2 ActuatorforElectronicDamperControl(EDC)3 Wishbone,bottom4 Steeringbox5 Crossmember6 Universaljointofsteeringshafttosteeringgear7 Castsidesection8 Strut
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G12ChassisandSuspension2.Axles
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Index Explanation9 Serviceopening10 Rearstiffeningplate11 Steeringshaft12 Universaljointofsteeringshafttosteeringcolumn13 Trianglewishbone,top14 Sidemember15 Swivelbearing16 Wheelbearingunit17 Trackrodhead18 Trailinglink19 Transversetube20 Frontserviceflap21 Lever22 Castcorner23 Castcornerconnection24 Springstrutholder
Inordertoachievethelowestpossiblevehicleweight,thefrontaxlecomponentsaremadealmostcompletelyfromaluminium.
Thedesignofthedouble-wishbonefrontaxleoffersthefollowingadvantages:
• Highagilityduetoabsorptionofhighlateralaccelerationforces.• Outstandingrollstabilizationwhencorneringwithoutanyreductioninridecomfort.• Comfortable,goodspringresponseoftheaxleandgooddirectionalstability.• Highcomfortduetominimuminfluenceofdisturbancevariables.
Inadditiontoensuringdrivingdynamicsandridecomfort,thedouble-wishbonefrontaxlealsoperformsvariouscrashfunctions.Thefrontaxlesupportispartofthecrashstructureofthebodyandformsanadditionalloadpath.Thisensuresthattheincreasedrequirementsrelatingtopedestrianprotectionaremet.
Drivingwithoutastiffeningplateisnotpermittedduetotheresultantlackofvehiclestability.
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G12ChassisandSuspension2.Axles
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2.1.1.VersionsofthefrontaxlesupportTwodifferentfrontaxlesupportsareuseddependingonthevehicleequipment.
VersionsofthefrontaxlesupportintheG12
Index ExplanationA Rear-wheeldrivesDriveB All-wheeldrivexDrive
2.1.2.NotesforServiceTwodifferentwishbonesareavailabletoServiceforcambercorrection.
CambercorrectionbyupperwishboneintheG12
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G12ChassisandSuspension2.Axles
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Index ExplanationA Cambercorrectionbyupperwishbone+30minB Cambercorrectionbyupperwishbone-30min
Inordertoavoiddamagetotheballbearingontheupperwishbone,itmustbeensuredwhenperformingdisassemblyorassemblyworkthatthedeflectionangleoftheballjointdoesnotexceedavalueof55°.
Thefollowingtableshowswhenwheelalignmentisnecessaryonthefrontaxlewhenacomponentisreplaced.
Replacementofacomponentonthefrontaxle
Wheelalignmentrequired
Frontaxlesupport YESSteeringbox YESWishbone,bottom YESRubbermountforwishbone,bottom YESTrailinglink NORubbermountfortrailinglink NOTrianglewishbone,top NORubbermountforupperwishbone NOTrackrod YESSwivelbearing YESWheelbearing NOAirsuspensionstrut NOSupportbearing NO
Thefollowingtableshowswhenwheelalignmentisnecessaryonthefrontaxlewhenacomponentisundone.
Undoingthescrewconnectionatthefrontaxle
Wheelalignmentrequired
Frontaxlesupporttobody NOSteeringboxtofrontaxlesupport YESBottomwishbonetofrontaxlesupport YESBottomwishbonetoswivelbearing NOTrailinglinktofrontaxlesupport NOTrailinglinktoswivelbearing NOUpperwishbonetobody NO
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G12ChassisandSuspension2.Axles
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Undoingthescrewconnectionatthefrontaxle
Wheelalignmentrequired
Upperwishbonetoswivelbearing NOTrackrodtosteeringbox NOTrackrodendtotrackrod YESTrackrodendtoswivelbearing NOSpringstruttobottomwishbone NOSupportbearingtobody NOBottomsteeringshafttosteeringbox NOUppersteeringshafttosteeringcolumn NO
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G12ChassisandSuspension2.Axles
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2.2.Rearaxle
OverviewofrearaxleintheG12
Index Explanation1 Supportbearing2 Airsuspensionstrut3 Frontrubbermount4 Rearrubbermount5 Airdeflector
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G12ChassisandSuspension2.Axles
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Index Explanation6 Cambercontrolarm7 Wishbone8 Camberlink9 Wheelbearingunit10 Wheelcarrier11 Trailingarm12 Controlarm13 Compressionstrut14 Axlesupport
Thefive-linkrearaxleoftheG12ischaracterizedbyprecisewheelguidance,whichcomesintoitsowninvariousdrivingsituations,suchasduringloadreversalsorthetransitionfromcorneringtostraight-aheaddriving.Inaddition,thefive-linkrearaxleoffersveryhighcomfortincombinationwithsportydrivingdynamics.
Itwaspossibletoresolvethisconflictofgoalsbymeansofthefollowingmeasures:
• Doubleflexiblerear-axlerubbermounts• Highstructuralrigidityoftherearaxlesupport• Largesupportareaoftherearaxlesupport
Itwaspossibletokeeptheunsprungmassesofthefive-linkrearaxlelowthroughtheuseofanaluminiumwheelcarrieraswellasvariousforgedaluminiumandsheetsteelcontrolarms.
Cleverdefinitionofthekinematicpointsaswellasprecisedesignoftheballjointsandrubbermountsresultinalargespringtravelrangeincombinationwithoptimumwheelguidance.Thesmallactingleverarmsensureparticularlygoodinsensitivitytobumpsintheroad.Theextremelyrigidcontrolarmsaswellasthetorsion-freerearaxlesupportandbodyconnectionsrealizedbymeansofcompressionstrutsresultinextremelyprecisewheelguidance.
Theairdeflectorsunderthecontrolarmsminimiseswirlandthusincreasetheefficiencyofthevehicle.
2.2.1.NotesforServiceThefollowingtableshowswhenwheelalignmentisnecessaryontherearaxlewhenacomponentisreplaced.
Replacementofacomponentontherearaxle
Wheelalignmentrequired
Rearaxlesupport YESRubbermountforrearaxlesupport YESCambercontrolarm YESCamberlink YESTrailingarm YES
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G12ChassisandSuspension2.Axles
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Replacementofacomponentontherearaxle
Wheelalignmentrequired
Wishbone YESBalljointinthewheelcarrier YESControlarm YESWheelcarrier YESWheelbearing NOAirsuspensionstrut NOSupportbearing NO
Thefollowingtableshowswhenwheelalignmentisnecessaryontherearaxlewhenacomponentisundone.
Undoingacomponentontherearaxle WheelalignmentrequiredRearaxlesupporttobody YESFrontcompressionstruttobody NOCamberlinktorearaxlesupport YESCambercontrolarmtowheelcarrier YESCamberlinktorearaxlesupport YESCamberlinktowheelcarrier NOTrailingarmtorearaxlesupport YESTrailingarmtowheelcarrier YESControlarmtorearsuspensionsubframe YESControlarmtohubcarrier NOWishbonetorearaxlesupport NOWishbonetowheelcarrier NOAirsuspensionstruttowheelcarrier NOSupportbearingtobody NO
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G12ChassisandSuspension2.Axles
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Rearaxlepositioning
ComparisonofrearaxleontheF01/F02withtheG12
Index ExplanationA RearaxleoftheF01/F02B RearaxleoftheG121 Body2 Centeringmountingforrearaxlesupport3 Mountingforrearaxlesupport4 Rearaxlesupport5 Rubbermountoftherearaxlesupport
OntheG12,nocenteringmountingsareusedonthebodyforalignmentoftherearaxle.Thismakesitpossibletoensureduringassemblythattherubbermountsoftherearaxlearescrewedtothebodycompletelywithoutanytension.Bumpsintheroadareisolatedandarenottransmittedtothebodyduetodirectcontactoftherubbermounts.
Newspecialtoolsareusedforremovalandassemblyoftherearaxlesupport.Therearaxlesupportisheldinthecorrectpositionforinstallationbymeansof2guidepins.Forthedetailedprocedure,refertothecurrentrepairinstructions.
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G12ChassisandSuspension2.Axles
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CenteringtoolforremovingandinstallingtherearaxleintheG12
Index Explanation1 Centeringpinforlongitudinalandtransversedirections(x-andyaxes)2 Centeringpinforlongitudinaldirection(y-axis)
Basicalignmentoftherearaxlesupportisensuringbythecentringpinforlongitudinalandtransversedirections.Duetothepermittedproductiontolerancesoftherearaxlesupport,thesupportispositionedonlyinlongitudinaldirectionbythesecondcentringpin.
Anincorrectprocedureforpositioningtherearaxlesupportcanleadtoproblemsduringwheelalignment.
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G12ChassisandSuspension3.AirSuspension
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Inordertoguaranteeuniformridecomfortindependentlyoftheloadstatus,theG12isequippedasstandardwithairsuspensiononthefrontandrearaxles.Thetwo-axleridelevelcontroloftheG12isofferedonlyincombinationwithelectricallycontrolledshockabsorbers.
Theairsuspensionincreasestheridecomfort.Thesystemperformsadjustmentmainlyatstandstill,e.g.inordertocompensateforachangeinheightduetothevehicleload.Theinertiaofthesystemmeansthatitcannotreacttodrivingdynamicsdisturbancevariables,whichmayoccurwhenthevehicleisdrivenquicklyontwistingroads.Dynamiccontrolwhendrivingservesonlytocompensateforchangesinheightduetoafallingfueltankvolumeaswellastemperaturechangesoftheairintheairsuspensionstruts.
Theairsuspensionoffersthefollowingadvantages:
• Increaseindrivingsafety,sincetheself-levellingsuspensionautomaticallykeepstheheightofthevehiclebodyatapredefinednominalride-levelinallloadstates.
• Highridecomfortduetoautomaticadaptationoftheoscillationbehaviortothevehicleweight.• Increasedcustomerbenefitthroughmanualleveladjustmentbymeansoftherideheight
selectionswitch.
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G12ChassisandSuspension3.AirSuspension
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Systemoverviewoftwo-axleridelevelcontrolintheG12
Index ExplanationA Compressedairline,frontright(colorcodeblack)B Compressedairline,rearright(colorcodeblue)C Compressedairline,rearleft(colorcodered)D Compressedairline,frontleft(colorcodegreen)E Compressedairlineforpressureaccumulator(colorcodeyellow)1 Airsuspensionstrut,frontright2 EDCvalve,frontright(ElectronicDamperControl)3 Rideheightsensor,frontright4 Rearrightpowerdistributionbox5 Relayforairsupplysystem
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G12ChassisandSuspension3.AirSuspension
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Index Explanation6 VerticalDynamicsPlatform(VDP)(centralcontrolunit)7 Airsuspensionstrut,rearright8 Positivebatteryterminaldistributor9 Airsuspensionstrut,rearleft10 Pressureaccumulator2liter11 Pressureaccumulator4liter12 Airsupplysystem13 Rideheightselectionswitch14 Airsuspensionstrut,frontleft
ThecentralcontrolunitforcontrollingtheairsuspensionistheVerticalDynamicsPlatform(VDP).TheVerticalDynamicsPlatform(VDP)controlunitreadsinthecurrentrideheightvaluesbymeansofthe4rideheightsensors.TheVerticalDynamicsPlatform(VDP)activatesthesolenoidvalvesofthesolenoidvalveblockinordertoperformcontrolactions.
Controlactionsatstandstillandatlowvehiclespeeds(0–20km/h/0–12mph)areachievedbyusingthestoragevolumeofthetwopressureaccumulators.Forcontrolactionswhendriving(>20km/h/>12mph),therequiredcompressedairisnottakenfromthepressureaccumulator,butisgeneratedbythecompressorandforwardeddirectlytothecorrespondingairsuspensionstruts.Inexceptionalsituations,thecompressorcanalsobeswitchedonwhenthevehicleisatstandstill.
Theincreaseinvolumeintheairsuspensionstrutliftsthevehiclebody.Achievementofthenominalride-levelheightisdetectedbythe4rideheightsensorsandactivationofthecorrespondingsolenoidvalvesisinterrupted.Three-pointcontrolisusedforprocessinginordertoavoidfrequentre-adjustment.Therearaxleiscontrolledindividuallybymeansofbothrideheightsensors.Inthecaseofthefrontaxle,thecorrespondingrideheightisadjustedonthebasisofameanvalue.
Thecompressedairlineshavedifferentcolorsinordertoavoidconfusionduringservicingworkonthesolenoidvalveblock.Thefollowingtablecontainsanoverviewofthecolorcodes.
Colorcode ComponentYellow PressureaccumulatorBlack Airsuspensionstrut,frontrightGreen Airsuspensionstrut,frontleftBlue Airsuspensionstrut,rearrightRed Airsuspensionstrut,rearleft
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G12ChassisandSuspension3.AirSuspension
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3.1.AirsupplysystemTheairsupplysystemismadeupofthefollowingcomponents:
• Electricalcompressor• Solenoidvalveblock• Holderwithvibrationdamper
Theairsupplysystemhasthetaskofgeneratingtherequiredcompressedairandcoordinatingtheairflowsbetweentheelectricalcompressor,pressureaccumulatorsandthe4airsuspensionstrutscorrespondingtotherequirements.ThecalculationsrequiredforthisareperformedbytheVerticalDynamicsPlatform(VDP).
Forpackagereasons,thesystemcomprisestwoseparatepressureaccumulatorswithatotalvolumeof6litersandamaximumstoragepressureof17.5bar.Atotalvolumeof105litersisavailabletothesystematmaximumpressure.
AirsupplysystemoftheG12
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Index Explanation1 Pressureaccumulator2liters2 Airintakehose3 Electricalcompressor4 Holderwithvibrationdamper5 Solenoidvalveblock6 Pressureaccumulator4liters7 Compressedairlineforpressureaccumulator2liters8 Compressedairlineforpressureaccumulator4liters9 Compressedairlineforairsupplytosolenoidvalveblock10 Ventilationtoatmosphere11 Connectionforairintakehose12 Housingcoverforaircleaner61 Plug-incontactforelectricalaircompressor62 Plug-incontactforelectricaldrainsolenoidvalve63 Plug-incontactforsolenoidvalveblock64 Plug-incontactoftemperaturesensor
Theelectricalcompressorisswitchedviaarelay.TherelayisactivatedbytheVerticalDynamicsPlatform(VDP).Inordertopreventvibrationsfrombeingtransmittedintothevehicleinteriorwhenthecompressorisrunning,theairsupplysystemissecuredtothevehiclebodybymeansofaholderwithvibrationdampers.
Topreventthedriverfrombeingirritatedbythestart-upnoisesofthecompressor,thisisswitchedonalmostexclusivelywhiledriving.Thecompressorcanalsobeswitchedonatvehiclestandstillifthefollowingpreconditionsareallmet:
• VehicleconditionResiding/Awake• Sufficientvehiclevoltage• Rideheight–40mmoftheinitializesvalue• Insufficientpressureinthepressureaccumulatorforcontrol
Theintakeairiscleanedbytheaircleanerupstreamofthecompressoranddriedbytheairdrierdownstreamofthecompressor.Cleaningisnecessarysothatthevalvesareprotectedagainstsoiling.Thewaterisextractedfromtheairinordertoprotectthevalvesagainsticingatlowambienttemperatures.Ifthevalvesweretofreezeduetoexcessivelyhighairhumidityintheairsupplysystem,thiswouldmeanthatlevelcontrolbytheairsuspensionwouldnolongerbepossible.Toavoidthis,theairdrierispermanentlycleanedordried.
Thegranulateintheairdrierabsorbsmoistureathighpressureandgivesthisoffagainatlowpressure.Themoistureisextractedfromtheairwhenairflowsthroughthegranulatewhenfillingthesystem.Whenthevehicleheightislowered,theexcessairwithlowpressureisroutedthroughtheairdrier.Thestoredmoistureisthengiveofftotheairagainasitflowspast.Thispermanentregenerationoftheairdrierensuresfault-freeoperationofthesystemwithouttheneedformaintenancework.
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Pneumaticconnectionsincompressedairsystemsareusuallyprovidedwithstandardisednumbers.Thisservesthepurposeofdifferentiationandisintendedtoexcludethepossibilityoftheconnectionsbeingmixedup.Thefollowingtableprovidesanoverviewofthestandardizednumbercodes.
Numbercode Meaning0 Intakeairconnection1 Energysupply2 Energyoutlet3 Atmosphere
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Thefollowinggraphicshowsaschematicillustrationoftheairsupplysystem.
SchematicillustrationoftheairsupplysystemintheG12
Index ExplanationA AircompressorB SolenoidvalveblockC FillingD Draining
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Index Explanation1 Airfilter2 Electricmotor2.1 Energyoutlet,output1(airsuspensionstrut,frontleft)2.2 Energyoutlet,output2(airsuspensionstrut,frontright)2.3 Energyoutlet,output3(airsuspensionstrut,rearleft)2.4 Energyoutlet,output4(airsuspensionstrut,rearright)2.5.1 Energyoutlet,pressureaccumulator12.5.2 Energyoutlet,pressureaccumulator23 Pneumaticdischargevalvewithpressurerelieffunction4 Airdrier5 Non-returnvalve6 Electricaldrainsolenoidvalve7 Temperaturesensor8 Electricalsolenoidvalveofpressureaccumulators9 Electricalsolenoidvalveforrearleftairsuspensionstrut10 Electricalsolenoidvalveforrearrightairsuspensionstrut11 Electricalsolenoidvalveforfrontrightairsuspensionstrut12 Electricalsolenoidvalveforfrontleftairsuspensionstrut13 Pressuresensor
3.1.1.Technicaldata
Compressor Drainsolenoidvalve
Temperaturesensor
Solenoidvalveblock
Supplyvoltage
12V 12V 5 V 12V
Pickupcurrentpervalve
— 0.82A6 — 0.8-1.0A
Holdingcurrentpervalve
— 0.55A6 — 0.55A6
Maximumstartingcurrent
110A6 — — —
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Compressor Drainsolenoidvalve
Temperaturesensor
Solenoidvalveblock
Maximumcontinuouscurrent
35A6 2.5A6 — 3.1A6
Dynamicpressurecontrol
22.5 bar — — —
Resistance — 9Ω 5kΩat25°C/77°F
6.8kΩ
3.1.2.Solenoidvalveblock
SolenoidvalveblockoftheairsupplyintheG12
Index Explanation2.1 Energyoutlet,output1(airsuspensionstrut,frontleft)2.2 Energyoutlet,output2(airsuspensionstrut,frontright)2.3 Energyoutlet,output3(airsuspensionstrut,rearleft)2.4 Energyoutlet,output4(airsuspensionstrut,rearright)2.5.1 Energyoutlet,pressureaccumulator2l2.5.2 Energyoutlet,pressureaccumulator4l63.1 Activationofsolenoidvalveforfrontleftairsuspensionstrut63.2 Activationofsolenoidvalveofpressureaccumulators63.3 Activationofsolenoidvalveforrearleftairsuspensionstrut63.4 Activationofsolenoidvalveforfrontrightairsuspensionstrut63.5 Ground
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Index Explanation63.6 Ground63.7 Sensorground(pressuresensor)63.8 Activationofsolenoidvalveforrearrightairsuspensionstrut63.9 Sensorvoltagesupply(pressuresensor)63.10 Sensorsignaloutput(pressuresensor)
Thedifferentelectricalsolenoidvalvesarelocatedinthesolenoidvalveblock.Theseareusedtoforwardthecompressedairtothedifferentcomponentsoftheairsuspension.TherequiredcalculationsforcontroloftheelectricalsolenoidvalvestakeplaceintheVerticalDynamicsPlatform(VDP)controlunit.
Thefollowingcontrolspeedscanbeachievedforaxle-basedchangesintherideheightbythesystem:
• Controlviathepressureaccumulators~10mm/s• Controlviatheelectricalcompressor~2mm/s
Anadvantageoftheinstallationpositionofthepressuresensoristhatthefillingpressuresofthepressureaccumulatorsandairsuspensionstrutscanbereadinwithonlyonesensordependingonactivation.
Whentheelectricalsolenoidvalveofthepressureaccumulatorsisactivated,apressuresensorsuppliesinformationaboutthecurrentfillingpressureofthesystemtotheVerticalDynamicsPlatform(VDP)controlunit.Ifthestoredpressureisnotsufficientforapendingchangeinrideheight,theVerticalDynamicsPlatform(VDP)controlunitswitchesonthecompressorforpressurebuild-up.However,thecompressorisswitchedononlysubjecttocertainpreconditionswhenthevehicleisatstandstillsothatcomfortisnotimpaired(seeAirsupplysystem).
Intheeventofactivationofthesolenoidvalvesforoperationoftheairsuspensionstruts,thepressuresensorsuppliesthefillingpressuresofthecorrespondingairsuspensionstruts.
3.2.AirsuspensionstrutTheheightofthevehiclebodyisautomaticallycontrolledviathepressureintheairsuspensionstrutinallloadstates.Thispreventsthevehiclebodyfromsinkingwhenthevehicleisloaded.Theairsupplyfortheairsuspensionstrutsisprovidedbyanelectricallydrivencompressorand2airaccumulators.Theairsuspensionthusfunctionsindependentlyoftheoperatingconditionofthecombustionengineandcanalsocompensateunevenloading(e.g.slopingload)byindividualwheelcontrolontherearaxle.
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AirsuspensionstrutsonfrontandrearaxlesintheG12
Index ExplanationA Airsuspensionstrutonthefrontaxle(illustrationfromall-wheeldrive)B Airsuspensionstrutonrearaxle1 Pot,upperpart2 Pot,lowerpart3 Gaiter4 Dustboot5 ControlvalveoftheElectronicDamperControl(EDC)6 Dampertube7 Electricalconnectionfordamperadjustment8 Pneumaticconnectionwithintegratedresidualpressureholdingvalve
Ontheairsuspensionstrut,thecoilspringisreplacedbyaU-typebellows.Theairispressedintotheairsuspensionstrutviaacompressedairconnection.TheU-typebellowsoftheairsuspensionstrutunrollsasaresultofthepressureincreaseandraisesthevehiclebody.Whentheairsuspensionstrutisvented,thepressurefallsandtheU-typebellowsrollsupagainsothatthevehiclebodyislowered.
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Thereisaresidualpressureholdingvalveinsidethepneumaticconnectionstopreventcompletepressurereductionintheairsuspensionstrut.Aresidualpressureof1.8–2.7barisheldwhenthecompressedairlinesareremoved.
Thepneumaticconnectionswithintegratedresidualholdingvalveontheairsuspensionstrutcannotbereplacedseparately.Theairsuspensionstrutwillbedamagedifitisattemptedtoremovedthepneumaticconnectionswithintegratedresidualpressureholdingvalve.
Airsuspensionstrut,frontaxle
Airsuspensionstrut,rearaxle
Airvolumeinnormalposition 2.87L 2.85LCompressiontravel 65mm 86mmReboundtravel 76mm 106.4mmFillingpressureondelivery 1.8-2.7bar 1.8-2.7bar
3.3.Rideheightsensor
RideheightsensorintheG12
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Index Explanation1 Holder2 Articulatedrodwithballsocket3 Deflectionlever4 Rideheightsensor
TheVerticalDynamicsPlatform(VDP)controlunitreadsinthecurrentrideheightvaluesofthevehiclebodybymeansofthe4rideheightsensors.Themaximummeasuringrangeoftherideheightsensoris70°.Theoutputisananaloguevoltagesignalbetween0.5Vand4.5V.
Therideheightsensorhasthefollowingelectricalconnections:
• Voltagesupply(5V)• Groundconnection• Signaloutput(0.5–4.5V)
RideheightsignaloftherideheightsensorsintheG12
Index ExplanationV VoltageinVW Angle
Afterrenewalofoneormorerideheightsensors,theservicefunctionforrideheightadjustmentmustbeperformedusingtheBMWdiagnosissystemISTA.
TherideheightvaluesarestoredintheBodyDomainController.Theyarealsousedforleveladjustmentoftheheadlights.
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3.4.Operatingstrategy
InputandoutputdiagramoftheairsuspensionintheG12
Index Explanation1 VerticalDynamicsPlatform(VDP)2 Compressor3 Solenoidvalveblock4 Drivingexperienceswitch5 Doorcontactswitch6 Rideheightselectionswitch7 Temperaturesensor(insidethecompressor)
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Index Explanation8 Pressuresensor(insidethesolenoidvalveblock)9 Rideheightsensor10 Vehicleelectricalsystemvoltage11 Vehiclespeed
ConfigurationoptionsoftheairsuspensionintheG12
Index ExplanationA NormallevelorSportlevelactivatedB Highlevelactivated1 SPORTbuttononthedrivingexperienceswitch2 Rideheightselectionswitch
Therideheightcanbeadjustedmanuallybymeansoftherideheightselectionswitchandthedrivingexperienceswitch.Threedifferentrideheightsareavailable.
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RideheightsoftheG12
Index ExplanationA Sportlevel(-10mm)B Normallevel(+/-0mm)C Highlevel(+20mm)
Situation Highlevel Normallevel SportlevelRideheight +20mm +/–0mm -10mmRideheightactivation
Rideheightselectionswitch
— 1)Drivingexperienceswitch2)Drivingspeed> ~ 140km/h/> ~ 87mph
Speed 0–40km/h/0–25mph
0~140km/h/0~87mph
1)0km/h–finalspeed2)~140km/h/~ 87mph–finalspeed
Thefollowingprerequisitesmustbemetinordertoperformmanualadjustmentintherideheightbymeansoftherideheightselectionswitch:
• DrivingreadinessResiding/Awakeordrivingbetween0–40km/h/0–25mph• Sufficientvehiclevoltage• Doorsclosed• Pressureaccumulatorwithsufficientfillingpressure
(onlyrelevantfordrivingreadinessResiding/Awake)
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ThefollowinggraphicshowstheoperatingstrategyoftheairsuspensionintheG12.
OperatingstrategyoftheairsuspensionintheG12
Index ExplanationA Highlevel(+20mm)B Normallevel(+/-0mm)C Sportlevel(-10mm)H Rideheightofthevehiclebodyv Vehiclespeed1 RideheightselectionswitchsettoHighlevel2 DrivingexperienceswitchinComfortposition3 DrivingexperienceswitchinSportposition
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3.4.1.Highlevel
OperatingstrategyoftheairsuspensionintheG12atHighlevel
Index ExplanationA Highlevel(+20mm)B Normallevel(+/-0mm)C Sportlevel(-10mm)H Rideheightofthevehiclebodyv Vehiclespeed1 RideheightselectionswitchsettoHighlevel2 DrivingexperienceswitchinComfortposition3 DrivingexperienceswitchinSportposition
Inthespeedrangebetween0–40km/h/0–25mph,theHighlevel(+20mm)canbeactivatedmanuallyviatherideheightselectionswitch.Thisrideheightsettingisintendedtoallowthedrivertodriveovershouldersorrampswithalargegradientanglewithoutdamagingthevehicleduetotheincreasedgroundclearance.Thefollowingrideheightsaresetautomaticallyifthisspeedrangeisexceeded.
1 IfthedrivingexperienceswitchisinComfortposition,therideheightisloweredtoNormallevel(+/-0mm).
2 IfthedrivingexperienceswitchisinSportposition,therideheightisloweredtoSportlevel(-10mm).
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Whenadrivingspeedof~140km/h/~87mphisexceeded,thevehiclebodyisautomaticallyloweredfromNormalleveltoSportlevel(-10mm)independentlyoftherespectiveswitchsettings.LoweringtoSportleveloffersthefollowingadvantages:
• Lowvehiclecenterofgravityandthusincreaseddrivingdynamics.• Improvedaerodynamicsandthuslowerfuelconsumption.
3.4.2.Normallevel
OperatingstrategyoftheairsuspensionintheG12atNormallevel
Index ExplanationA Highlevel(+20mm)B Normallevel(+/-0mm)C Sportlevel(-10mm)H Rideheightofthevehiclebodyv Vehiclespeed1 RideheightselectionswitchatNormallevel2 DrivingexperienceswitchinComfortsetting
Normallevel(+/-0mm)canbesetbymeansofthefollowingswitchpositions.
• RideheightselectionswitchinNormalposition.• DrivingexperienceswitchnotinSportposition.
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Whenadrivingspeedof~140km/h/~87mphisexceeded,thevehiclebodyisautomaticallyloweredfromNormalleveltoSportlevel(-10mm)independentlyoftherespectiveswitchsettings.LoweringtoSportleveloffersthefollowingadvantages:
• Lowvehiclecenterofgravityandthusincreaseddrivingdynamics.• Improvedaerodynamicsandthuslowerfuelconsumption.
3.4.3.Sportlevel
OperatingstrategyoftheairsuspensionintheG12atSportlevel
Index ExplanationA Highlevel(+20mm)B Normallevel(+/-0mm)C Sportlevel(-10mm)H Rideheightofthevehiclebodyv Vehiclespeed1 RideheightselectionswitchatNormallevel2 DrivingexperienceswitchinSportsetting
Sportlevel(-10mm)canbesetbymeansofthefollowingswitchpositions.
• RideheightselectionswitchinNormalposition.• DrivingexperienceswitchinSportposition.
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Sportlevel(-10mm)offersthehighestdrivingdynamicsofallrideheightsduetothelowvehiclecenterofgravity.Thefuelconsumptionalsofallsduetotheimprovedaerodynamics.
3.5.NotesforServiceComplete(100%)tightnessoftheairsuspensioncannotbeguaranteedduetothenumerousflexiblecompressedairlineswiththecorrespondingcompressedairconnections.Adefinedlowlossofcompressedairisthereforepermissible.IfthevehicleisparkedatNormallevel,therideheightmaybeloweredbyuptoamaximumof–2mmafter24hours.Thismeansthattherideheightmaybeloweredbyupto-60mmforavehiclethathasbeenparkedfor30dayswithouttherebeingafaultcausedbyaleak.
SideviewoftheG12withairsuspensionloweredtomaximumextent
Sincecomponentsdonotallleaktothesameextentfortolerancereasons,itisalsopossiblethatthevehiclewillbeslopingatanangleafteraprolongedstandstilltime.
LowandslopingvehiclepositionsareautomaticallycompensatedbytheairsuspensionafterdetectionofthevehicleconditionResiding/Awake.Forthispurpose,themissingcompressedairisforwardedtothecorrespondingspringstrutsbythepressureaccumulator.Ifthefillingpressureofthepressureaccumulatorsistoolow,thelackofairiscompensatedbyswitchingontheelectricalcompressor.
Thefollowingscenariosforactivationoftheelectricalcompressorarepossible:
1 Iftherideheightislessthan–40mm,thecompressorwillbeswitchedononlywhentheengineisrunning.
2 Iftherideheightismorethan–40mmandthevehicleelectricalsystemhassufficientvoltage,thecompressorwillalreadybeswitchedonwhenthevehicleconditionResiding/Awakeisdetected.
3.5.1.LiftingthevehicleTheairsuspensionhasajackdetectionfunction.Thispreventscontrolactionoftheairsuspensionwhenthevehicleislifted.
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3.5.2.TransportmodeTheairsuspensionisintransportmodewhennewvehiclesaredelivered.Achangeintherideheightisnotpossible.TransportmodemustbedeletedusingtheBMWdiagnosissystemISTAduringthepre-deliverycheck.Thedifferentrideheightsoftheairsuspensioncanbeselectedonlyaftersuccessfulstart-upoftheairsuspension(transportmodedeleted).
3.5.3.BleedingtheairsuspensionWhenworkingoncomponentsoftheairsuspensionsystem,itisnecessarytodepressurizethesystembeforeundoingthevariouscompressedairlines.ThiscanbedoneusingtheBMWdiagnosissystemISTAbymeansofableedingroutine.Here,thevarioussolenoidvalvesoftheairsuspensionstrutsandtheelectricaldrainsolenoidvalveareactivatedsimultaneously.Inordertoprotectthevalvesagainstoverheating,thebleedingroutinecannotbeperformedanarbitrarynumberoftimesinsuccession.However,thefunctionisavailableagainafteradefinedwaitingperiod.
Inordertoavoiddamagetotheairsuspensionstruts,thevehicleshouldberaisedslightlyusingavehiclehoistduringthebleedingroutine.
However,itisnotrecommendedtocompletelyliftthevehicleduringthebleedingroutineasthishamperscompleteemptyingofthecompressedairfromtheairsuspensionstruts.
3.5.4.FillingtheairsuspensionThesystemisfilledautomaticallyviathevehicle'selectricalcompressorassoonasthemarginalconditionsforthisaremet.InordertoperformaleakagetestoftheairsuspensioninService,theelectricalcompressorcanbeswitchedonmanuallytofillthesystemusingtheBMWdiagnosissystemISTA.Iftheairsuspensionisfilledseveraltimes,theelectricalcompressormaybeswitchedofftopreventthecompressorfrombeingdamaged.
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3.6.Systemwiringdiagram
Systemwiringdiagramofthetwo-axleridelevelcontrolintheG12
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Index Explanation1 Rideheightsensor,frontleft2 EDCvalve,frontleft(ElectronicDamperControl)3 EDCvalve,frontright(ElectronicDamperControl)4 DSCrideheightsensor,frontright5 Powerdistributionbox,frontright6 BodyDomainController(BDC)7 Rearrightpowerdistributionbox8 VerticalDynamicsPlatform(VDP)9 Rideheightsensor,rearright10 EDCvalve,rearright(ElectronicDamperControl)11 Relayforairsupplysystem12 Positivebatteryterminaldistributor13 Compressor14 Solenoidvalveblock15 Airsupplysystem16 EDCvalve,rearleft(ElectronicDamperControl)17 Ride-heightsensor,rearleft18 CrashSafetyModule(ACSM)19 Rideheightselectionswitch20 DynamicStabilityControl(DSC)
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ThefollowinggraphicprovidesanoverviewofthebrakesystemoftheG12.
OverviewofbrakesystemintheG12
Index Explanation1 Plug-incontact,wheel-speedsensor,frontright2 EMFactuator(electromechanicalparkingbrake)3 Plug-incontact,wheelspeedsensor,rearright4 Plug-incontact,brakepadwearsensor,rearright5 Plug-incontact,wheelspeedsensor,rearleft6 Brakedisc,rearaxle7 Brakecaliper,rearaxle8 Auto-Holdbutton9 Parkingbrakebutton10 DSCbutton11 Bearingsupport,pedalmechanism12 Brakeservo13 Brakefluidexpansiontank14 DynamicStabilityControl(DSC)
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Index Explanation15 Brakecaliper,frontaxle16 Brakedisc,frontaxle17 Plug-incontact,wheel-speedsensor,frontleft18 Plug-incontact,brakepadwearsensor,frontleft
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4.1.Servicebrakes
4.1.1.BrakedesignInordertoenhancethevisualappearanceofthebrakes,Blackpaintedcalipersareoptionalinthe“AutobahanPackage”(ZAN).
Versions Frontaxle RearaxleStandardcaliper
AutobahnPackagewithBMWlogoprint
MSport
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4.1.2.Pedalmechanismmounting
MountingofthepedalmechanismonthebrakeservolinkageintheG12
Index ExplanationA BrakeservolinkageB Pedalmechanism1 Ballhead2 Plasticclip
AmodifiedmountingisusedintheG12betweenthepedalmechanismandthebrakeservolinkage.Here,theballheadofthebrakeservolinkageisengagedinaplasticcliponthepedalmechanism.
Anewspecialtoolisneededtoreleasethisconnection.
Partnumber83302409646
Specialtoolforremovingthepedalmechanism
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Whenremovingthepedalmechanism,alwaysobservetheinstructionsinthecurrentrepairinstructions.
4.2.ParkingbrakeTheBMWE65/E66(BMW7Seriesfrom2001–2008)wasthefirstproductionvehicleintheworldwithanelectromechanicalparkingbrakeEMF.ThiswasfollowedbymanyotherBMWmodelswithdifferentelectricalparkingbrakesystems.
Thefollowingadvantagesresultfromtheuseofsuchasystem:
• MorestoragespaceduetoomissionofaparkingbrakeleverandparkingbrakeBowdencable.• Contactpressureofbrakepadscorrectlyadjustedatalltimes.• Variousadditionalfunctionstoassistthedriver(e.g.automaticreleasewhendrivingoff).• Higherbrakingpowerofauxiliarybrakesystem.
Thefollowing2differentelectricalsystemsarecurrentlyusedatBMW:
• Electromechanicalparkingbrake=Cablepullsystemviaduo-servoparkingbrake(Küstersystem).
• Electricparkingbrake=Combinedbrakecaliper(TRW/Continentalsystem).
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Thefollowinggraphicshowsacomparisonofthetwosystems.
SystemcomparisonoftheelectromechanicalparkingbrakeintheF01/F02withtheelectricparkingbrakeoftheG12
Index ExplanationA F01/F02(BMW7Seriesfrom2008–2015)B G12(BMW7Seriesfrom2015)1a DSCcontrolunit(DynamicStabilityControl)1b DSCcontrolunitwithintegratedparkingbrakefunction
(DynamicStabilityControl)2 Instrumentpanel(KOMBI)3 Parkingbrakebutton4 Electricparkingbrakeviaactuatoratcombinedbrakecaliper
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Index Explanation5 Electromechanicalparkingbrakeviaduo-servoparkingbrake6 Electromechanicalparkingbrakeactuatorunitwithintegrated
controlunit(electromechanicalparkingbrake)BDC BodyDomainControllerZGM Centralgatewaymodule
IncontrasttothecablepullsystemintheF01/F02,theelectricparkingbrakesystemwithacombinedbrakecaliperfamiliarfromthesmallerseriesisusedintheG12.
Previously,theparkingbrakewasrealizedbymeansofaduo-servoparkingbrakeintheheavyupperclassvehicles.Theadvantageofthissystemisthehighself-lockingforceofthebrakepadswhentheparkingbrakeisapplied.
Duetotheincreaseinthepreloadforcesofthecombinedbrakecaliperwithelectricparkingbrake,itwaspossibletodispensewiththepreviouslyusedcablepullsystemintheG12.OmissionoftheassociatedcomponentsisbeneficialforweightreductionandalsofortherepairfriendlinessoftheG12.
TheelectricparkingbrakeoftheG12isdifferentiatedaboveallbythefactthatthereisnoseparatecontrolunit.TheelectricparkingbrakeisactivatedviathecontrolunitoftheDynamicStabilityControl(DSC).Thereisaparkingbrakebuttononthecenterconsoleforactivatingordeactivatingtheelectricparkingbrake.ThedriverisinformedaboutthecurrentsystemstatusviatheinstrumentclusterKOMBI.
Thebrakepadisappliedwithapreciselycalculatedpreloadforceviatwoactuatorsscrewedontothebrakecalipers.AtemperaturemodelisstoredintheDSCcontrolunitwhichmakesitpossibletodrawconclusionsaboutthebrakedisctemperatures.Asthecontactpressuredecreaseswhenthebrakediscscooldown,thesystemmustadjustthebrakepadsasappropriate,particularlyifthebrakediscsarehot.Thetimeandfrequencyoftheadjustmentvariesdependingontheinitialtemperaturecalculated.
Whentheelectricparkingbrakeisopened,theactuatorsaremovedbackonlyuntilthebrakepadshavereachedtheircorrectlysetclearance.Duetothisreadjustmentfunction,theactuatorsmustbemovedbackbeforeexchangingthebrakepadsinService.Forthedetailedprocedure,refertothecurrentrepairinstructions.
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ActuatorforelectricparkingbrakeintheG12
Index Explanation1 Beltdrive2 Planetarygears3 Spindlenut4 Brakecaliper5 Electricmotor(DC)
Thereisanelectricmotorwithbeltdriveandplanetarygearonthehousingofthecombinedbrakecaliperwithelectricparkingbrake.Whentheelectricmotorisactivated,theforceistransmittedviathebeltdriveandplanetarygeartothespindlenut.Thespindlenutgeneratestherequiredstroketoapplythebrakepad.ThecontrolunitoftheDynamicStabilityControlcandeterminethepreloadforceonthebasisoftheriseincurrentoftheelectricmotor.
Whencarryingoutservicingwork,anextendedspindlenutcanbetravelledbacktoitsinitialpositionasfollows:
• Specialtoolformechanicallyturningback• Servicefunction“Workshopmode”intheBMWdiagnosissystemISTA
4.2.1.Functions
Dynamicemergencybraking
Iftheparkingbrakebuttonisoperatedduringthejourneyaboveadefineddrivingspeed,theDSCunitinitiatesadynamicemergencybrakingoperation.Apressurebuild-upoccursinall4wheelbrakesduetoactivationofthe6-pistonpumpandthechangeovervalvesintheDSCunit.Thesliplimitsofallwheelsaremonitoredwiththeassistanceofthefourwheelspeedsensorstoensureastablebraking
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operationuntilthevehiclecomestoastandstill.Thetwoactuatorsoftheelectricparkingbrakeareactivatedassoonasthevehiclecomestoastandstill.Thevehicleisthensecuredtopreventitfromrollingawayonlybymeansoftheparkingbrake.
Automaticreleaseoftheparkingbrake
Thisfunctionallowsthedrivertodriveoffwhentheparkingbrakeisactivatedwithoutoperatingtheparkingbrakebuttontoreleasethebrake.
Prerequisitesforreleasingtheelectricparkingbrake:
• Driver'sdoorisclosed• VehicleconditionDRIVING• Electricparkingbrakeactuated• Drivepositionengaged• Acceleratorpedaloperated
4.2.2.BraketeststandTheDynamicStabilityControl(DSC)hasarollermodesothatthebrakingpoweroftheelectricparkingbrakecanbecheckedonabraketeststand.Whenrollermodeisactivated,thevehicleisbrakedviatheactuatorsoftheelectricparkingbrakewhentheparkingbrakebuttonispressed.ADSCpressurebuild-upinthe4wheelbrakesdoesnottakeplace.Thismakesitpossibletodeterminethebrakeforcesoftheelectricparkingbrake.
IntheG12,rollermodeisautomaticallydetectedonthebasisofaplausibilitycheck(wheelspeedcomparison).Thedetectiontakesamaximumof5seconds(canberecognizedbyslowflashingoftheredparkingbrakeindicatorlight).
Afteractivationofteststandmodethesystemisinteststandmode.Thisconditionisacknowledgedbytheindicatorlightoftheparkingbrakestartingtoflashatafrequencyof1Hz.Theparkingbrakecanbeappliedin5stagesusingtheparkingbrakebutton.Inthiscase,thebrakingvariesbetweentheminimumbrakingpowerinthefirststageandthemaximumbrakingpoweroncetheparkingbrakebuttonhasbeenpressedfivetimes.Ifthebuttonisoperatedcontinuously,thesystemincreasesthebrakingpowerautomaticallyincrementallyuptothemaximumbrakingpower.Theflashingfrequencyoftheparkingbrakeindicatorlightchangesfrom1Hzto3Hzwhentheparkingbrakebuttonispressedinteststandmode.
Thefollowingpointsmustbeobservedduringthetest:
• Donotpresstheaccelerator• DrivepositionN(neutral)• Donotpressthefootbrake
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4.3.Serviceinformation
4.3.1.ServicebrakesThestatusofthebrakepadscannotbereadoutpermanentlyviatheCentralInformationDisplay(CID).
ThefollowinggraphicshowsthevehiclestatuswithoutandwithinformationaboutthestatusofthebrakepadsontheCentralInformationDisplay(CID).
CIDmessageonvehiclestatusintheG12
Index ExplanationA BrakepadwearsensorwithinlimitsB Brakepadwearsensoroutsidelimits1 Vehiclestatus2 OKEngineoil3 OKBrakefluid4 OK§vehicleinspection5 OKVehiclecheck6 Brakepadsrear(padwearshortlybeforethewearlimit)
TheG12isequippedwithaone-stagebrakepadwearsensor.Novehiclestatusaboutthecurrentstatusofthebrakepadsisoutputaslongasthissensorhasnotbeengroundbythebrakedisc.
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Beforethewearlimitofthebrakepadisreached,thesensorwireoftheone-stagebrakepadwearsensoriscutthroughbytherotatingbrakediscwhiledriving.Asfromthispoint,thevehiclestatusofthebrakepadscanbecheckedontheCentralInformationDisplay(CID).Theremainingdistanceuntilthewearlimitofthebrakepadisreachedis4000-5000km/2500-3100miles,dependingondrivingstyle.
Inaddition,thedriverisinformedabouttheconditionofthebrakepadsbymeansofthefollowingwarnings.
Remainingdistance YellowCheckControlmessage
RedCheckControlmessage
<2000km/<1200miles X0km/0miles X
Thecurrentrepairinstructionsmustalwaysbeobservedinordertoavoidinterferencenoisesafterbrakepadreplacement.
4.3.2.Parkingbrake
Replacingbrakepads
Inordertoreplacethebrakepadsoftherearparkingbrakecalipers,itisfirstnecessarytoturnbackthedrivespindleinthebrakecaliper.ThiscanbedoneeithermanuallyusingaspecialtoolorusingtheBMWdiagnosissystemISTA.TheparkingbrakebuttonisblockedtopreventuseafteractivationofworkshopmodeviatheBMWdiagnosissystemISTA.Thispreventsinjuryduringthebrakeservice.Theparkingbrakebuttonisenabledagainatthestartofdrivingorafterexitingworkshopmode.
Afterenablingviathespeedthresholdof3km/h/1.8mph,theparkingbrakemustbere-initializedbybuttonoperation(apply/releasebrake).
Emergencyrelease
Itispossibletomechanicallyturnbackthedrivespindletoreleasetheparkingbrakeafterremovingtheactuatorhousingfromthebrakecaliper.Topreventaccidents,thevehiclemustfirstbesecuredtopreventitfromrollingaway.
Emergencyreleaseoftheelectricparkingbrakeispermittedonlybycorrespondinglytrainedpersonnel.
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TheG12willbeequippedinthestandardequipmentconfigurationwithrun-flattires.Asparewheelisavailableasoptionalequipment.
Components Standardequipment OptionalequipmentRun-flattires XSparewheel(OE300) X
TiresoftheG12
Index ExplanationA Tireswithoutemergencyrunningproperties(NotforUS)B Run-flattires
Intheeventoftirepressurelossinarun-flattire,thecustomercanstilldriveatarestrictedspeed(max.80km/h/50mph)foraremainingdistancethatisdependentonthevehicleload.Onvehicleswiththeoptionalchassisandsuspensionpackage“ActiveComfortDrive”,thevehicleweightisautomaticallydistributedviatheactiveelectricstabilizerswhendrivingwithanunpressurisedrun-flattiresothattheunpressurisedwheel(<0.5bar)isrelievedtothemaximumpossibleextentandtheintactwheelsloadedcorrespondingly.Thisensuresthatthemaximumpossibleremainingdistancecanbedriven.Themaximumpermittedremainingdistancewithmediumloadis80kilometres/50miles.
Furtherinformationonthefunctionoftheactiveelectricstabilizerisprovidedinthesection“AutobahanPackage”.
Adamagedrun-flattirecanalsobereplacedbyatirewithoutemergencyrunningpropertiesintheeventoftirefailure.However,thetirewithoutemergencyrunningpropertiesmustbereplacedattheearliestopportunitybyarun-flattire.
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5.1.PuncturedetectionsystemsDependingoncountry,theG12isequippedwiththefollowingsystemsforpuncturedetection:
• Tirepressurecontrol(RDC)
5.2.TirePressureMonitorRDCi
SystemoverviewoftirepressurecontrolRDCiintheG12
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Index Explanation1 Wheelelectronics,frontright2 CentralInformationDisplay(CID)(displayoftirepressurespossible)3 Wheelelectronics,rearright4 Remotecontrolreceiver(FBD)5 Wheelelectronics,rearleft6 Instrumentpanel(KOMBI)7 DynamicStabilityControl(DSC)8 Wheelelectronics,frontleft
TheG12isequippedwiththeRDCialreadyfamiliarfromtheF15.TheRDCiisasystemwhichperformsdirectmeasurementandwhichdeterminestherealtirepressuresbymeansofwheelelectronicsineachwheel.UnlikewiththeRDClow,aseparateRDCcontrolunitisnotrequiredfortheRDCi.ThefunctionsoftheRDCiareintegratedintotheDynamicStabilityControl(DSC)controlunit.Theremotecontrolreceiver(FBD)actsasareceiverforthesentreportsofallwheelelectronics.ItthenforwardsthisinformationviabustotheDSCcontrolunit.
ThepreviousRDCisystemsweresuppliedbyContinental.ThesystemsupplieroftheRDCiintheG12isthecompanySchrader.Inordertoensurefault-freeoperationofthesystem,itisessentialthatonlySchraderwheelelectronicsareused.Itisnotpossibletoassumeanyliabilityformalfunctionswiththird-partywheelelectronics.
OntheG12,theresttimesrequiredbythesystembeforethenewwheelelectronicscanbetaught,havechanged.Previously,avehiclewithRDCihadtobestationaryforanuninterruptedperiodofatleast8minutesindependentlyoftheterminalstatusbeforetheDSCcontrolunitacceptedtheIDsofthenewwheelelectronics.
OntheG12,thevehicleconditionisdecisiveforthetimesrequiredbythesystembeforetheIDsofnewwheelelectronicsareacceptedandtaught.Thefollowingtableprovidesanoverviewofthedifferentconditions.
Vehiclecondition 5minutes 17minutesResiding/Awake XDriving X
SothatnewwheelelectronicscanbetaughtbytheDynamicStabilityControl(DSC),astandingtimeofatleast5minutes(Residing/Awake)or17minutes(driving)mustbeobservedafterawheelexchange.
Ifthestandingtimeofatleast5minutes(Residing/Awake)or17minutes(driving)wasnotreachedbeforestartingajourneywithnewwheelelectronics,aCheckControlmessagewillbedisplayedtothedriverafteracertaintime.Inthiscase,thevehiclemustonlyremainstationaryforanuninterruptedperiodoflongerthan5minutesinResiding/Awakemodeor17minutesinDrivingmode.ThenewwheelelectronicswillthenbeautomaticallytaughtbythecontrolunitoftheDynamicStabilityControl(DSC).
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ThevehiclecanalsobeinthevehicleconditionDrivingwhentheenginehasbeenswitchedoffbytheautomaticenginestart-stopfunctionMSA.
Thesystemmustbere-initializedintheeventofchangesinthetirepressuresaswellasafterwheelexchange.InitializationofthenewtirepressurescanbeperformedusingthecontrollerontheCentralInformationDisplay(CID).
5.2.1.Wheelelectronics
WheelelectronicsfromSchraderintheG12
Thewheelelectronicsareinthefollowingmodes,dependingonthesystemstatus:
• Sleepmode• Teach-inmode• Readinessmode
TherearealsochangesinthetransmissionmodesoftheSchraderwheelelectronicsincomparisonwiththetransmissionmodesofthewheelelectronicsfromContinental.Inordertoguaranteethelongestpossiblebatterycapacity,thewheelelectronicsrequirelongerstandingtimesbeforetheyswitchtoteach-inmode.
After15minutesinrestmode(wheelstandstill),thewheelelectronicsstarttotransmitinteach-inmodeassoonastheyareacceleratedtoaspeedfasterthanaround20km/h.Inteach-inmode,thereportsaresenttotheDSCcontrolunitevery15secondsforapproximately9minutes(40reports).Transmissioninteach-inmodeallowstheDSCcontrolunittocalculatetheinstallationpositionoftherespectivewheelelectronics.Thewheelelectronicswillstarttotransmitinreadinessmodeifawheel
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setwaschangedfromonevehicletoanotherwithoutthewheelsethavingbeeninrestmode(wheelstandstill)foranuninterruptedperiodofmorethan15minutes.Teachingofthewheelelectronicsisnotpossibleinreadinessmode.
Balancingofthewheelsetshortlybeforefittingonthevehicleisnotaproblem.Sinceonlyasmallnumberofreportsaretransmittedinteach-inmodeduringbalancing,theremainingreportsaresufficienttoreliablyteachthewheelelectronics.
ThebatterystatusofthewheelelectronicscanbereadoutviatheBMWdiagnosissystemISTA.Theremainingbatterylifeisspecifiedinpercent.
DetailedinformationontheoperatingprincipleoftheRDCiisprovidedintheTrainingReferenceManual“I01CompleteVehicle”.
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BusoverviewG12
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Index ExplanationACC ActivecruisecontrolACSM CrashSafetyModuleAHM Trailermodule(NotforUS)AMPT AmplifierTop(tophighfidelityamplifier)ASD ActiveSoundDesignBDC BodyDomainControllerCON ControllerDDE DigitalDieselElectronics(NotforUS)DME DigitalMotorElectronicsDME2 DigitalEngineElectronics2DSC DynamicStabilityControlEARSVH ElectricactiverollstabilizationrearEARSVV ElectricactiverollstabilizationfrontEGS ElectronictransmissioncontrolEPS ElectromechanicalPowerSteeringFLA High-beamassistantFLER FrontalLightElectronicsRightFLEL FrontalLightElectronicsLeftFZD RooffunctioncenterGWS GearselectorHEADUNIT HeadunitHKARearclimatecontrol
Automaticrearair-conditioningandheating
HKFM TailgatefunctionmoduleHSR RearaxleslipanglecontrolIHKA Integratedautomaticheating/airconditioningKAFAS Camera-baseddriversupportsystemsKOMBI InstrumentpanelLEM LightEffectManagerNFC NearFieldCommunicationNVE NightVisionElectronicsPCU PowerControlUnitPMA ParkingmanoeuvringassistantRFK ReversingcameraRSE RearSeatEntertainment
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Index ExplanationRSL RadarSensorLeft(avoidanceassistant)RSR RadarSensorRight(avoidanceassistant)SAS OptionalequipmentsystemSCR SelectiveCatalyticReductioncontrolunit(NotforUS)SMBF Seatmodule,passengerSMBFH Seatmodule,passenger,rearSMFA Seatmodule,driverSMFAH Seatmodule,driver,rearSPNMHL SeatpneumaticsmodulebackleftSPNMHR SeatpneumaticsmodulebackrightSWW Lanechangewarning(main)SWW2 Lanechangewarning(secondary)TCB TelematicCommunicationBoxTRSVC ControlunitforrearviewcameraandSideViewVDP VerticalDynamicPlatformVM VideoModule(NotforUS)VTG VTGcontrolunitWCA WirelesschargingtrayZGM Centralgatewaymodule
ThecontrolunitsthatarerelevanttodrivingdynamicsareinterconnectedviatheFlexRaybus.Thisbusischaracterizedaboveallbyitshighdatatransferrateof10MBit/s.
Themostimportantsystemsandtheirfunctionsaredescribedinmoredetailbelow.
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6.1.DynamicStabilityControl(DSC)AlongsidetheVerticalDynamicsPlatform(VDP)controlunit,theDynamicStabilityControl(DSC)representsthecoreelementofthedrivingdynamicscontrolsystemsusedtoincreaseactivesafety.Itoptimizesdrivingstabilityinalldrivingconditionsandalsotractionwhendrivingoffandaccelerating.Italsoidentifiesunstabledrivingconditionssuchasundersteeringoroversteeringandhelpsmaintainthevehicleonasteadycourse.
InstallationpositionofDynamicStabilityControl(DSC)intheG12
Index ExplanationA DSCunit1 DSCcontrolunit2 BrakelineconnectionsattheDSChydrauliccontrolunit3 Returnpump4 Bracket
TheDynamicStabilityControl(DSC)islocatedinthefrontlowerareaofthevehicle.ThemanufacturerdesignationisTRWDSC-EBC460.Duetothedifferentconnectiondiametersofthebrakelines,channelconfusionofthevarioushydrauliclinesisnotpossible.
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DSCunitintheG12
Index ExplanationA DSChydraulicunitB DSCcontrolunit1 Pressuresensors2 Hydraulicdampingelements3 Returnpumpactivation4 Solenoidvalves(12x)5 Controlunitconnector6 Solenoidvalvecoils(12x)
TheDSCcontrolunitandtheDSChydrauliccontrolunitarescrewedtogether.TheDSCcontrolunitcanbereplacedindividuallytoreduceservicingcosts.
Inolderseries,thedifferentdrivingdynamicssystemsareconnectedviatheIntegratedChassisManagement(ICM)controlunit.ThecontrolunitoftheDynamicStabilityControl(DSC)intheG12hasanadditionalstorageelement(blackbox)inwhichsomeofthefunctionsoftheIntegratedChassisManagement(ICM)arestored.Thedifferentdrivingdynamicscontrolsystemsarecoordinatedperfectlybymeansofthealgorithmsstoredintheblackbox.
Thefunctionsofthetirepressurecontrol(RDC)andelectricparkingbrake(EPB)wereintegratedintheDSCcontrolunit.
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6.1.1.Hydrauliccircuitdiagram
HydrauliccircuitdiagramofTRWDSC-EBC460
Index ExplanationA InstalledonlyonhybridversionB OnlyforoptionalequipmentactivecruisecontrolwithStop&Gofunction1 Hydraulicdampingelements2 6-pistonpump3 DSCpressuresensor4 Brakemastercylinder5 Brakefluidexpansiontank6 Brakeservo7 BrakepedaltravelsensorAV Exhaustvalves
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Index ExplanationEV IntakevalvesHL RearaxleonleftHR RearaxleonrightTV SeparatorvalvesUPS ChangeovervalvesVL FrontaxleonleftVR Frontaxleonright
DifferentDSCversionsareuseddependingonthedrivetypeandequipmentrange.Inthehybridversion,thereisanadditionalbrakepedaltravelsensoronthefootbrakelever.
Ifthevehicleisequippedwiththeoptionalequipment“ActivecruisecontrolwithStop&Gofunction”,thereare2additionalpressuresensorsinthehydraulicunit.
6.1.2.FunctionsThefollowingtableprovidesanoverviewofthedifferentfunctionsoftheDSCunit.
Function ExplanationAntilockBrakeSystem(ABS)
Preventsblockingofindividualwheelswhenbrakingthroughtargetedmodulationofthebrakepressures.Vehiclesteerabilityismaintained.
DynamicStabilityControl(DSC)
Ifthevehiclestartstoundersteeroroversteer,itisstabilizedbytargetedbrakeinterventionsatindividualwheels.
DynamicTractionControl(DTC)
ThisisaspecialmodeoftheDynamicStabilityControl(DSC).IninteractionwithASCandDSC,thismodefeaturesextendedinterventionthresholdsandpermitsanevensportierdrivingstylewithoutinterventionsonnormalsurfacesaswellasmaximumpropulsiononloosegroundsuchassnow,sandorcoarsegravel.
CorneringBrakeControl(CBC)
Preventsthevehiclefromturninginwhenitisbrakedlightlyunderhighlateralaccelerationforcesbymeansofasymmetricalcontrolofthebrakepressure.Thecorneringstabilityisimproved.
AutomaticStabilityControl(ASC)
Preventsthedrivewheelsfromspinningbytargetedbrakingofthesewheelsandadaptationofthedrivetorquedeliveredbytheengine.Vehiclepropulsionisoptimizedasaresultanddrivingstabilityismaintained.
DynamicBrakeControl(DBC)
Intheeventofpanicbrakinginitiatedbythedriver,thesystemsupportsthedriverbyautomaticallyimmediatelyapplyingthemaximumbrakepressuretoensurethebestpossibledeceleration.
AutomaticDifferentialBrake(ADB-X)
Replicatesthefunctionofadifferentiallock.Ifawheeldisplaysatendencytospin,thiswheelisautomaticallybrakedsothatpropulsioncanstillbeachievedviatheotherwheelofthedrivenaxle.
Trailerstabilizationcontrol
Automaticallydetectswhenavehiclewithtrailerisstartingtosnake,stabilizestheoutfitbytargetedbrakeinterventionsandsimultaneouslydeceleratesittoanuncriticalspeedforsnaking.
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Function ExplanationBrakestandby Buildsupamoderatebrakepressureinthesystemwhenthedrivertakes
hisfootofftheacceleratorpedalveryquickly.Thebrakepadsareappliedslightlyasaresult.Thebrakingeffectthenactsmorequicklyifthedriverthenperformspanicbraking.
Drybyapplyingbrake Dependingonoperationofthewiper,appliesthebrakepadsgentlyatintervalsinordertodrythebrakediscs.Thebrakingeffectissignificantlyimprovedbythiswhenthevehicleisbraked.
Fadingsupport Supportsthedriverwhenbrakingifthebraketemperaturehasbecomeveryhighduetoanextremedrivingstyleandthedesireddecelerationcanbeachievedonlybyapplyingahigherbrakeforce.
Drive-offassistant Holdsthevehicleforapproximately1.5sonuphillgradientswhenthedriverreleasesthebraketodriveoff.Thisallowsthedrivertodriveoffcomfortablywithoutthevehiclerollingawayonitsown.
AutomaticHold Automaticallyholdsthevehicleafterithascometoastandstillwithoutitbeingnecessarytostillpressthebrakewhenthedrivepositionisselected.Thebrakeisautomaticallyreleasedwhentheacceleratorpedalispressedandthevehicledrivesawaynormally.Thefunctioncanbeswitchedonandoffbymeansofabutton.
Ifatrailertowhitchisretrofitted,thefunction“trailerstabilizationlogic”mustbeencodedintheDSCcontrolunit.
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6.1.3.Systemwiringdiagram
SystemwiringdiagramfortheDynamicStabilityControl(DSC)intheG12
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Index Explanation1 Brakepadwearsensor,frontleft2 Wheel-speedsensor,frontleft3 Powerdistributionbox,enginecompartment4 Wheel-speedsensor,frontright5 Powerdistributionbox,frontright6 BodyDomainController(BDC)7 Rearrightpowerdistributionbox8 Wheelspeedsensor,rearright9 Brakepadwearsensor,rearright10 Actuator,electricparkingbrakerearright11 Actuator,electricparkingbrakerearleft12 Wheelspeedsensor,rearleft13 CrashSafetyModule(ACSM)14 ButtonforelectricparkingbrakeandforAutomaticHoldfunction15 DSCbutton16 Brakelightswitch17 Steeringcolumnswitchcluster18 Instrumentpanel(KOMBI)19 Brakefluidlevelswitch20 DynamicStabilityControl(DSC)
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6.2.Steering
OverviewofsteeringintheG12
Index Explanation1 Steeringwheel2 Uppersteeringcolumnwithsteeringcolumnadjustment3 Controlunitforsteeringcolumnadjustment4 Lowersteeringcolumnwithslidingpiece5 Trackrodend6 Trackrod7 Steering-torquesensor8 EPScontrolunit(ElectronicPowerSteering)9 ElectricmotorforEPS(ElectronicPowerSteering)
Inelectricsteeringsystems,thesupporttorqueisgeneratedbymeansofanelectricmotor.
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Inadditiontothepuresupportfunction,thefrontwheelscaninprinciplebemadetoperformanysteeringmovementindependentlyofthemanualtorqueappliedatthesteeringwheel.ThissystemisthereforeaprerequisiteforrealizationofalargenumberofassistancefunctionssuchastheParkingManoeuvringAssistant(PMA).
TheElectronicPowerSteering(EPS)permitsareductionintheaveragefuelconsumptionofapproximately0.3lper100km/62miles.Afurtheradvantageisthatnooilisneededforsteeringassistance.
6.2.1.SteeringwheelItispossibletochoosebetween3differentsteeringwheeldesigns.
SteeringwheelversionsintheG12
Index ExplanationA SportssteeringwheelwithshiftpaddlesB LuxurysteeringwheelC Standardsteeringwheel(NotforUS)
Intheluxuryversion,theleatherrimfeaturesawoodinlayleathersteeringwheel.Thedrivercanoperatethevariousassistanceanddriverinformationsystemsbymeansofthemultifunctionswitches.
Steeringwheeldiameterofthedifferentversions:
• Sportssteeringwheel=382mm• Luxurysteeringwheel=384mm(NotforUS)• Standardsteeringwheel=385mm(NotforUS)
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Additionalfunctionsareoptionallypossible:
• Heatedleatherrim.• Transmissionofhapticvibrations(steeringwheelvibration)
Forassistancesystemssuchaslanedepartureorlanechangewarning.• Hands-Offdetection
Forthetrafficjamassistantfunction.• Shiftpaddles
ForthemanualshiftfunctionwiththeautomaticSporttransmission(SA2TB).
6.2.2.Steeringcolumnadjustment
SteeringcolumnadjustmentintheG12
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Index Explanation1 Electricmotor2 Spindle3 Controlunitforsteeringcolumnadjustment4 Steeringshaft
Thesteeringcolumnwithelectricallongitudinalandheightadjustmentallowsthedrivertoassumeanoptimumsittinganddrivingpositionthroughseamlessadjustmentofthesteeringwheelposition.
Adjustmentrange:
• Heightadjustment=+/-20mm• Forward/backadjustment=-20mm/+40mm
6.2.3.VersionoverviewTheG12isequippedwiththefollowingdifferentsteeringsystems:
• Standardsteering12V• IntegralActiveSteering12V• IntegralActiveSteering24V
Components Standardsteering12V
IntegralActiveSteering12V
IntegralActiveSteering24V
ElectronicPowerSteeringwithnormalrackgeometry
X
ElectronicPowerSteeringwithvariablerackgeometry
X X
12 Vbattery X X X12Vauxiliarybattery XPowerControlUnit(PCU)(DC/DCconverter150W)
X
Rearaxleslipanglecontrol(HSR)
X X
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Thefollowinggraphicshowstheinstallationpositionsofthedifferentsystemcomponents.
OverviewofthesteeringsystemsoftheG12
Index Explanation1 ElectromechanicalPowerSteering1a Conventionalrackgeometry(standardsteering)1b Variablerackgeometry(IntegralActiveSteering)2 PowerControlUnit(PCU)(onlyfor24Vsteering)3 Rearaxleslipanglecontrol(HSR)(IntegralActiveSteering)4 12Vauxiliarybattery(onlyfor24Vsteering)5 Separatingelement(onlyfor24Vsteering)6 12 Vbattery7 DynamicStabilityControl(DSC)
Withthestandardsteering,theG12isequippedwithconventionalelectromechanicalpowersteering(12V)withnormalrackgeometry.
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TheoptionalequipmentIntegralActiveSteeringnownolongerconsistsofanactivesteeringsystemwithvariableratiotransmission,buthasbeenreplacedbyanelectromechanicalpowersteeringsystemwithvariablerack(sportsteering)aswellasrearaxleslipanglecontrol(HSR).Dependingontheaxleloadsofthefrontvehicleend,a12Vor24Vsteeringsystemisused.Therearaxleslipanglecontrol(HSR)alwaysoperateswitha12Vvoltage.
ThefollowingtableprovidesanoverviewofthedifferentvoltagelevelsoftheelectricsteeringintheoptionalequipmentIntegralActiveSteering.
Model Engine Rear-wheeldrivewithIntegralActiveSteering
All-wheeldrivewithIntegralActiveSteering
740i B58 12V —750(x)I N63 24 V 24 V
6.2.4.IntegralActiveSteering
Frontaxle
Ratioofthevariablerackgeometry(OEIntegralActiveSteering)intheG12
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Index ExplanationA Moreindirectsteeringgearratiointhecenterpositionof
thevariablerack(0°-45°)B Transitionalrange(45°-130°)C Directsteeringgearratiooutsidethecenterpositionof
thevariablerack(>130°)X Steeringanglein°y Steeringgearratioinmm/steeringwheelturn1 Variablerackgeometry(IntegralActiveSteering)
ThevariablesteeringgearratiointheoptionalequipmentIntegralActiveSteeringisaccomplishedbythegeometry/pitchofthetoothedgearoftherack.Aroundthecenterpositionofthesteeringgear,thesteeringsystembehavesaccuratelywithsteadydirectionalstability.Asthesteeringanglemovesawayfromthecenterposition,theratiobecomesincreasinglymoredirect.
SteeringangleoftheIntegralActiveSteeringonthefrontaxleoftheG12
Index ExplanationA Moreindirectsteeringgearratio(variablerackgeometry)B Directsteeringgearratio(variablerackgeometry)
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Rearaxle
Rearaxleslipanglecontrol(HSR)intheG12
Index Explanation1 Trackcontrolarmmounts2 Electricmotor3 HSRcontrolunit(rearaxleslipanglecontrol)4 Spindlepositionsensor(PLCDsensor)5 Permanentmagnet6 Carrierplate
Therearaxleslipanglecontrol(HSR)mountedontherearanglepermitsamaximumsteeringangleoftherearwheelsof+/-3°.Asaresult,itwaspossibletoreducetheturningcirclebyapproximately1mincomparisonwithvehicleswithoutrearaxleslipanglecontrol(HSR).Therearaxleslipanglecontrolisavailablefromaspeedofapproximately5km/h/3mphuptothemaximumspeed.
TherequesttoadjustthesteeringangleattherearaxleisissuedbytheDynamicStabilityControl(DSC).Aspindledriveinsidethecomponentisrotatedviatheelectricmotor.Thisproducesalinearmovementatthetwotrackcontrolarms.Usingthepositionsensor,thecontrolunitoftherearaxleslipanglecontrol(HSR)candeterminethelineardisplacementandthuscalculatethesteeringangleofthetworearaxlewheels.
Thespindledriveoftherearaxleslipanglecontrol(HSR)isself-inhibiting.Thismeansthatthevehiclehastheidenticaldrivabilitytoavehiclewithoutrearaxleslipanglecontrol(HSR)intheeventofsystemfailure.
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Aspecialfixtureisrequiredforalignmentinordertoassemblethecarrierplates.ThisisnotavailableinService.Forthisreason,thecarrierplatesontherearaxleslipanglecontrol(HSR)mustnotbeundone.Ifthisisnotobserved,thewheelalignmentontherearaxlewillbecomeincorrectlyadjusted.
Thecarrierplatesoftherearaxleslipanglecontrol(HSR)mustnotbeundoneinService
Operatingstrategy
InputandoutputdiagramoftheIntegralActiveSteeringintheG12
Index Explanation1 DynamicStabilityControl(DSC)2 Rearaxleslipanglecontrol(HSR)3 Yawrateandlateralacceleration(ACSM)4 Wheelspeeds5 Steeringangle(EPS)
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OperatingstrategyoftheIntegralActiveSteeringintheG12
Index ExplanationA OppositesteeringB Parallelsteering
Inthespeedrangeuptoapproximately60km/h/37mph,therearaxleslipanglecontrol(HSR)steersintheoppositedirectiontothesteeringanglesofthefrontaxlesteering.Thispermitsincreasedvehiclemanoeuvrability.
Asfromthespeedrangeofapproximately60km/h/37mph,therearaxleslipanglecontrol(HSR)steersinthesamedirection.Thisimprovesthedirectionalstabilityofthevehicle.
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Drivingdynamicscontrolinterventionswhencornering
Whenchanginglanesquickly,allvehicleshaveatendencytoproduceasignificantyawresponseandcansometimesstarttooversteer.IftheDynamicStabilityControl(DSC)detectsadeviationbetweenthedriverwishandvehicleresponse,thevehicleisstabilizedbymeansofasteeringinterventionattherearaxle.Thespeedofthestabilizinginterventionissuchthatitishardlydiscerniblebythedriver.ItispossibletolargelydowithoutdeceleratingDSCbrakeinterventions.Asaresult,thevehicleismorestableandthedrivingdynamicsarepreserved.
PossibledrivingdynamicsinterventionsoftheDSCandIntegralActiveSteeringwhencornering
Index ExplanationA Preventionofundersteerbybrakeinterventionsatindividualwheels(DSC)B Preventionofundersteerbysteeringinterventionsattherearaxle(HSR)M Yawmomentactingonthevehicleduetoaninterventionbythedriving
dynamicscontrol1 Courseofanundersteeringvehicle2 Courseofavehiclewithneutraldrivability3 Individualbrakemodulation(DSC)4 Steeringinterventionattherearaxle(HSR)
Ifthedriverunderestimatesabendwhendrivingrapidly,hemaybesurprisedbysuddenundersteer.Therearaxleslipanglecontrol(HSR)canalsoperformacorrectiveinterventioninundersteersituationsandthusadditionalincreasesactivesafety.
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Drivingdynamicscontrolondifferentsurfaces
Hardbrakingmanoeuvresonroadwaysthatareslipperyononesidemakethevehicleyawtothevehiclesidewithmoregrip.Intheeventofemergencybraking,thedriverofaconventionalvehiclemusttakecorrectiveaction.Withthisso-calledµ-splitbraking,theDynamicStabilityControl(DSC)providesastabilizingyawmomentviaasteeringinterventionattherearaxle.
µ-splitbrakingmanoeuvreswithdifferentdrivingdynamicssystems
Index ExplanationA VehiclewithoutDSCB VehiclewithDSCC VehiclewithDSCandrearaxleslipanglecontrol(HSR)
(optionalequipmentIntegralActiveSteeringSA2VH)
FurthertoA)WithoutDSC
WhenbrakingwithavehiclewithoutDSC,maximumbrakeforceissupportedonthedrysideoftheroadandonlylowbrakeforceonthewetoricyside.Ananti-clockwiseyawmomentisproducedwhichcanleadtothevehicleskiddingtotheright.
FurthertoB)WithDSC
WhenbrakingwithavehicleequippedwithDSC,thebrakeforcesatthewheelsaremeteredsothattheyawmomentactingonthevehicleisreduced.Thevehiclethereforeremainscontrollable.Thestoppingdistancemaybeincreasedslightly.
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FurthertoC)WithDSCandrearaxleslipanglecontrol(HSR)
WhenbrakingwithavehicleequippedwithDSCandrearaxleslipanglecontrol(HSR)(optionalequipmentIntegralActiveSteeringSA2VH),theDSCcontrolunitcalculatesthesteeringanglefortherearwheels.Theactuatorsoftherearaxleslipanglecontrol(HSR)convertthecalculatedsteeringangleintoanactivesteeringangleatbothrearwheels.Theresultantstabilizingyawmomentallowsthemaximumbrakeforcestobeappliedinordertoachievetheshortestpossiblestoppingdistance.Theperfectinteractionofsteeringandbrakeinterventionthereforeincreasesactivesafetyandenhancesthedrivingdynamicsofthevehicle.
6.2.5.ServiceinformationIntheeventofarepair,thesteeringgearcanbefullylowered.Thiseliminatestheneedforcomplexaxledisassemblyandrepaircostsarereducedsignificantly.
Steeringangle
Thesteeringangleiscalculatedbythecontrolunitoftheelectromechanicalpowersteeringusingtherotoranglesensor.Intheeventofalossofthevoltagesupply,thisstoredvalueislostandmustbetaughtagain.Thiscanbedonestaticallybyturningthewheelstotherightandleftwiththeenginerunningordynamicallywhendrivingslowly.
Drivingwithsnowchains
SettingmenufordrivingwithsnowchainsintheG12
Index ExplanationA SnowchainmodedeactivatedB Snowchainmodeactivated
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Inordertoavoiddamagetothewheelarcheswhendrivingwithsnowchains,therearaxleslipanglecontrol(HSR)mustbefixedinstraight-aheadposition.ThedrivercandothismanuallyusingthecontrollerontheCentralInformationDisplay(CID).Themaximumpermittedspeedis50km/h(31mph)hisspeedisexceeded,therearaxleslipanglecontrol(HSR)switchesonagainautomatically.
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6.2.6.Systemwiringdiagram
24Vsteering
Systemwiringdiagramfor24VsteeringintheG12
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Index Explanation1 DynamicStabilityControl(DSC)2 Wheel-speedsensor,frontleft3 Enginecontrolunit(DME)4 ElectronicPowerSteering(electromechanicalpowersteering)(EPS)5 Steering-torquesensor16 Steering-torquesensor27 Wheel-speedsensor,frontright8 Powerdistributionbox,frontright9 BodyDomainController10 Wheelspeedsensor,rearright11 Rearrightpowerdistributionbox12 PowerControlUnitPCU(DC/DC150W)13 Separator14 12Vauxiliarybatteryfor24Vsteering15 Positivebatteryterminaldistributor16 Wheelspeedsensor,rearleft17 CrashSafetyModule(ACSM)18 Brakelightswitch19 Steeringcolumnswitchcluster(SZL)20 Instrumentpanel(KOMBI)
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Rearaxleslipanglecontrol(HSR)
Systemwiringdiagramforrearaxleslipanglecontrol(HSR)intheG12
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Index Explanation1 DynamicStabilityControl(DSC)2 CrashSafetyModule(ACSM)3 BodyDomainController(BDC)4 Rearrightpowerdistributionbox5 Positivebatteryterminaldistributor6 Rearaxleslipanglecontrol(HSR)
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Electricallyadjustablesteeringcolumn
SystemwiringdiagramforelectricallyadjustablesteeringcolumnintheG12
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Index Explanation1 Powerdistributionbox,frontright2 BodyDomainController(BDC)3 Steeringcolumnswitchcluster(SZL)4 Buttonforsteeringcolumnadjustment5 Memoryswitch6 Controlunitforsteeringcolumnadjustment7 Electricmotor(DC)8 Electricmotor(DC)
6.3.ElectronicDamperControl(EDC)Inordertomeetthehighcustomerdemandswithrespecttocomfortanddrivingdynamics,theG12isequippedasstandardwithElectronicDamperControl(EDC).Theelectronicallycontrolledshockabsorbersformaunitwiththerespectiveairsuspensionstrutandcannotbereplacedseparately.Thereare2electriccontrolvalvesoneachshockabsorberwhichallowthecompressionandreboundstagesoftheregulatedshockabsorberstobeadjustedseparatelyfromeachother.Thismakesitpossibletoperfectlycounteractthevibrationsofthebodyandwheels.Thisincreasessafety,comfortanddrivingdynamics.
6.3.1.ShockabsorberdesignTheshockabsorbersaresingle-tubegas-filledshockabsorbers.Thegascushionconsistsofnitrogenatapressureof16.5bar.Thisispressedtogetherandthuscompressedfurtherbytheoildisplacedwhenthepistonrodisretracted.Thehighgaspressurepreventsfoamingoftheoilunderalloperatingconditionsandthusguaranteesoptimumshockabsorberoperation.Inaddition,thehighgaspressureensuresthatthepistonrodispressedoutwithaforceofapproximately400N(~40kg).Compressionoftheshockabsorberbyhandisthereforehardlypossible.
Thefollowinggraphicshowstheinternaldesignofanelectricallyregulatedshockabsorber.
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DesignofEDCshockabsorberintheG12
Index Explanation1 Pistonrod2 Workingchamber3 Overflowduct4 Controlvalve,compressionstage5 Comfortvalve,compressionstage6 Comfortvalve,reboundstage7 Controlvalve,reboundstage8 Gaspressurechamber
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Index Explanation9 Dividingpiston10 Balancingchamber11 Bottomvalve12 Workingchamber13 Workingpiston
Inordertopermitasportydrivingstyleongoodroadswhilestillabsorbingbumpsonroughroadsurfacesascomfortablyaspossible,theoilflowinsidetheshockabsorbercanbevariablyadjusted.Thechangesintheoilflowchangetheforcesactingontheshockabsorber.
Theshockabsorberhas2controlvalves,whichallowseparateadjustmentofthedampingforceforrebound(reboundstage)andcompression(compressionstage).
Thecontrolvalvesadjustthedampingforcebychangingarestrictorcross-sectionthroughwhichanoilflowispressed.Thefollowingrelationshipexistsbetweentherestrictorcross-sectionanddampingforce:
• Largerestrictorcross-section=lowdampingforce.• Smallrestrictorcross-section=highdampingforce.
Therestrictorcross-sectionandthusthedampingforcecanbeadjustedseamlessfewmilliseconds.
Compressionstage
Duringcompression,theshockabsorberispushedtogethertelescopicallyandoperatedintheso-calledcompressionstage.
Rebound
Duringrebound,theshockabsorberisextendedtelescopicallyandoperatedintheso-calledreboundstage.
6.3.2.SystemoverviewThedrivingexperienceswitchisusedtoconfiguretheshockabsorberadjustmentsetting.Itispossibletochoosebetweenasportilyfirmorcomfortablysoftchassisandsuspensionsetup.Thefollowingtableprovidesanoverviewofthesettingoptions.
Drivingmode CharacteristicsCOMFORTPLUS ComfortableComfort/ECOPRO BalancedSport Sports
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SystemoverviewoftheElectronicDamperControl(EDC)
Index Explanation1 ElectronicPowerSteering(electromechanicalpowersteering)(EPS)2 Controlvalvesforshockabsorberadjustment,frontright3 Rideheightsensor,frontright4 Controlvalvesforshockabsorberadjustment,frontleft5 Rideheightsensor,frontleft6 DynamicStabilityControl(DSC)7 BodyDomainController(BDC)8 AdvancedCrashSafetyModule(ACSM-High)9 Drivingexperienceswitch10 VerticalDynamicsPlatform(VDP)11 Rideheightsensor,rearright12 Controlvalvesforshockabsorberadjustment,rearright13 Ride-heightsensor,rearleft14 Controlvalvesforshockabsorberadjustment,rearleft
TheElectronicDamperControl(EDC)comprisesthefollowingcomponents:
• 4electricallycontrolledshockabsorberswith2controlvalveseach• VerticalDynamicsPlatform(VDP)controlunit• 4rideheightsensorsfordeterminationofwheelmovement• Sensorclusterfordeterminationofbodymovement(lift,pitchandroll)
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TheVerticalDynamicsPlatform(VDP)controlunitusesvariousdatasuchasbodymovement,transverseandlongitudinalacceleration,steeringangleandtheroadconditiontocalculatewheel-individualcontrolcommandsfortheelectricalcontrolvalvesintheshockabsorbers.Inthisway,thedampingforceoftheindividualshockabsorbersiscontinuouslychangedapproximately100timespersecond.Thismeansthatdemand-basedadjustmentofthedampingforceisalwayspossiblecorrespondingtothedrivingsituation.
Fewervehiclebodymovementsarepermittedifasportierdrivingmodeisselected.Theshockabsorbersareadjustedtoahardsettingmorequicklyandmoreoften.Thisautomaticallyresultsinalossofcomfort.
Inthestandardequipmentconfiguration,informationabouttheverticalbodymovements(pitch,rollandlift)ismadeavailablebytheCrashSafetyModuleACSM-High.Theretractionandextensionspeedsoftheshockabsorbersaredeterminedbymeansoftherideheightsensors.
Ifthevehicleisequippedwiththeoptionalequipment“ActiveComfortDrive”(SA2VS),thereareadditionalwheelaccelerationsensors.TheseareusedamongotherthingsformorepreciseregulationoftheElectronicDamperControl(EDC).
Thefollowingtableshowsthedifferentcomponentsuseddependingonthechassisandsuspensionpackage.
Component Basicchassisandsuspension
ActiveComfortDrive
Wheelaccelerationsensors — XACSM-High X —ACSM-Low — X
Amoredetaileddescriptionoftheoptionalequipment“ActiveComfortDrive”(SA2VS)isprovidedinalaterchapter.
6.3.3.ElectricalshockabsorbercontrolThecontrolvalvesofthereboundandcompressionstagesareactivatedviapulse-widthmodulatedsignalsfromtheVerticalDynamicsPlatform(VDP)controlunit.Thecontrolvalvesareopeninde-energizedcondition.Theshockabsorberisinthemaximumsoftsettinginthiscondition.
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Controlofthecompressionstage
ControlofcompressionstageontheshockabsorberoftheG12
Index ExplanationA ShockabsorbermovementB Oilflow1 Mainvalve,compressionstage2 Workingpiston3 Mainvalve,reboundstage4 Bottomvalve5 Gaspressurechamber6 Controlvalve,reboundstage7 Comfortvalve,reboundstage8 Comfortvalve,compressionstage9 Controlvalve,compressionstage
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Whenthepistonrodisretracted,theoilvolumedisplacedbytheretractingpistonispressedthroughthebottomvalveintothecompensatingreservoirandgeneratesadampingforceatthebottomvalveintheprocess.Theoilvolumedisplacedbytheworkingpistonispressedthroughthecomfortandcontrolvalveofthecompressionstageandthuspassesfromtheworkingchamberbelowtheworkingpistonintotheworkingchamberabovethepiston.Therestrictorcross-sectioninthecontrolvalveadjuststhedampingforce.Theoilflowisforcedthroughthemainvalvewhenthecontrolvalveisclosed.Themaximumpossibledampingforceisthenset.
Controlofthereboundstage
ControlofreboundstageontheshockabsorberoftheG12
Index ExplanationA ShockabsorbermovementB Oilflow1 Mainvalve,compressionstage2 Workingpiston3 Mainvalve,reboundstage
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Index Explanation4 Bottomvalve5 Gaspressurechamber6 Controlvalve,reboundstage7 Comfortvalve,reboundstage8 Comfortvalve,compressionstage9 Controlvalve,compressionstage
Whenthepistonrodisextended,thegaspressureforcesthenecessarycompensationvolumeoutofthecompensatingchamberthroughthebottomvalveintotheworkingchamberbelowtheworkingpiston.Theoilvolumedisplacedbytheworkingpistonispressedthroughthecomfortandcontrolvalveofthereboundstageandthuspassesfromtheworkingchamberabovetheworkingpistonintotheworkingchamberbelowthepiston.Therestrictorcross-sectioninthecontrolvalveadjuststhedampingforce.Theoilisforcedthroughthemainvalveofthereboundstagewhenthecontrolvalveisclosed.Themaximumpossibledampingforceisthenset.
6.4.Anti-rollbarThefollowinganti-rollbarsareusedontheG12dependingonthevehicleequipment:
• StandardequipmentConventionalanti-rollbaronfrontandrearaxles.
• Optionalequipment(“ActiveComfortDrive”SA2VS)ElectricactiverollstabilizationonfrontandrearaxleEARSVV/EARSVH.
ComparisonofconventionalandactiverollstabilizationinstationaryconditionoftheG12
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Index ExplanationA ConventionalpassiverollstabilizationB Activerollstabilizationaq LateralaccelerationFq Transverseforceh Distancebetweenrollaxisandcenterofgravity(leverarm)Ma MomentofactivestabilizerMw RollmomentRA RollaxisSP centerofgravityφ Rollangle
Whencornering,thelateralacceleration(aq)actsatthevehiclecenterofgravity(SP).Thebodyrollsabouttherollaxis(RA),whichisdefinedbythekinematicsofthefrontandrearaxles.Thisresultsintherollangle(φ).
Onvehicleswiththeoptionalequipment“ActiveComfortDrive”(SA2VS),therollmoment(Mw)canbecompensatedsolelybytheactivestabilizersuptoacertainlateralacceleration.Arollangle(φ)buildsuponlywhentherollmoment(Mw)exceedsthecounter-torque(Ma)setbytheactivestabilizer.
Thefollowingdiagramshowsacomparisonofthedifferentrollanglesofbothanti-rollbarsasafunctionofthelateralacceleration.
Rollanglediagramoftheconventionalanti-rollbarandactivestabilizer
Index ExplanationA ConventionalrollstabilizationB Activerollstabilizationaqin[m/s²] Lateralaccelerationinmetrespersecondsquaredφin[°] Rollangleinangulardegrees
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6.5.Standardsuspension
Conventionalanti-rollbarintheG12
Index Explanation1 Rearaxleanti-rollbar2 Frontaxleanti-rollbar
Asstandard,conventionalanti-rollbarsonthefrontandrearaxlesreducetherolltendencyofthebodyduringfastcorneringorfastavoidancemanoeuvres.However,therearealsocomfortlossesinthecaseofone-sidedroadbumpsduetothetorsionspringcharacteristicsofaconventionalanti-rollbar.Ifaconventionalanti-rollbarisexcitedbyapulseatawheelononeside,thisleadstospringoscillationsoftheanti-rollbarsothatthewheelattheotherendoftheanti-rollbaralsoperformsor"copies"theseoscillations.Sincetheanti-rollbarispivot-mountedonthebody,thedriveralsofeelstherolloscillationscausedbythisso-called"copying".
6.5.1.ChassisandsuspensionsetupVehicledrivabilitywhencorneringcanbegreatlyinfluencedbyanti-rollbarsonthefrontandrearaxles.Adecisivefactorhereistherollmomentratiobetweenthefrontandrearvehicleaxles.Thisratiodependsontherespectiveanti-rollbarmomentsofthetwoaxles.
Thefollowingtableprovidesanoverviewofthepossiblerollmomentratiosandtheresultanthandlingofthevehicle.
Anti-rollbar Rollmomentratio Understeer OversteerFrontaxlesoft/rearaxlehard
<50% X
Frontaxlehard/rearaxlesoft
>50% X
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Thefollowinggraphicshowsthepercentagedistributionoftheanti-rollbarmoments(rollmomentratio)ofthefrontandrearaxleswhenconventionalanti-rollbarsareused.
Percentagedistributionoftheanti-rollbarmomentsonavehiclewithconventionalanti-rollbars
Index ExplanationA UndersteeringrollmomentratioMkin[%] Momentdistributionofconventionalanti-rollbarsinpercentvin[km/h] Drivingspeedinkilometersperhour1 Conventionalanti-rollbaronthefrontaxle2 Conventionalanti-rollbarontherearaxle
Withaconventionalanti-rollbar,therollmomentratioisoptimallyadaptedtotherespectivevehicle.Itisaimedtoachievehandlingwithslightundersteer.Fornormaldrivers,anoversteeringvehicleismoredifficulttocontrolthananundersteeringvehicle.
6.6.ActiveComfortDriveThepreviouslyknownoptionalequipmentAdaptiveDriveisreplacedintheG12bytheenhancedsuspensioncontrolsystem“ActiveComfortDrive”.
Thevariousdrivingdynamicscontrolsystemsarenetworkedtogetherintheoptionalchassisandsuspensionpackage“ActiveComfortDrive”inordertoachieveperfectdrivingdynamicscombinedwithhighridecomfort.InformationisreadinfromalargenumberofsensorsbytheVerticalDynamicsPlatform(VDP)controlunitandthecorrespondingcontrolcommandsareoutputtothedifferentactuators.Theaimistoabovealldetectroadbumpsandobstaclesaheadasearlyaspossibleandtoderiveappropriatecounter-measures.
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Thefollowinggraphicprovidesanoverviewoftheoverallsystem.
Systemoverviewoftheoptionalchassisandsuspensionpackage“ActiveComfortDrive”intheG12
Index Explanation1 ElectricactiverollstabilizationfrontEARSVV(optionalequipment
“ActiveComfortDrive”SA2VS)2 ElectronicPowerSteering(electromechanicalpowersteering)(EPS)3 Wheelaccelerationsensor,frontright(optionalequipment
“ActiveComfortDrive”SA2VS)4 Controlvalvesforshockabsorberadjustment,frontright5 Rideheightsensor,frontright6 Wheelaccelerationsensor,frontleft(optionalequipment
“ActiveComfortDrive”SA2VS)7 Controlvalvesforshockabsorberadjustment,frontleft8 Rideheightsensor,frontleft9 12Vbattery(optionalequipment“ActiveComfortDrive”SA2VS)10 DynamicStabilityControl(DSC)11 BodyDomainController(BDC)12 Stereocamera(optionalequipment“ActiveComfortDrive”SA2VS)13 AdvancedCrashSafetyModule(ACSM-Low)14 Drivingexperienceswitch15 VerticalDynamicsPlatform(VDP)16 Rideheightsensor,rearright17 Controlvalvesforshockabsorberadjustment,rearright
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Index Explanation18 Wheelaccelerationsensor,rearright(optionalequipment
“ActiveComfortDrive”SA2VS)19 Ride-heightsensor,rearleft20 Controlvalvesforshockabsorberadjustment,rearleft21 Wheelaccelerationsensor,rearleft(optionalequipment
“ActiveComfortDrive”SA2VS)22 Electricactiverollstabilizationrear(EARSVH)(optionalequipment
“ActiveComfortDrive”SA2VS)23 PowerControlUnit(PCU)(optionalequipment
“ActiveComfortDrive”SA2VS)
Theoptionalchassisandsuspensionpackage“ActiveComfortDrive”hasthefollowingadditionalcomponents:
• Wheelaccelerationsensorsonall4wheelcarriers• Electricactivestabilizersonthefrontandrearaxles• Anadditional12VbatteryaswellasaDC/DCconverter• Astereocamerainthewindscreen
Wheelaccelerationsensorsareusedintheoptionalchassisandsuspensionpackage“ActiveComfortDrive”forthefollowingreasons:
• Moreprecisedisturbancevariablecontroloftheelectricactivestabilizers(EARSV)possible.Avoidanceofso-calledcopyingfromonewheeltotheotherintheeventofroadbumps.
• PreciseregulationoftheElectronicDamperControl(EDC)ispossiblethroughdetectionofthewheelmovementviathewheelaccelerationsensorsandthebodymovementviatherideheightsensors.ProcessingofthetwoinformationsourcesallowsuseofasimplifiedcontrolunitversionoftheCrashSafetyModule(ACSM-Low).
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6.6.1.Predictivecontrol
Predictivecontroloftheoptionalchassisandsuspensionpackage“ActiveComfortDrive”intheG12
Index Explanation1 Satellite2 Navigationdata3 Stereocamera(KAFAScamera3)4 Controllableshockabsorber,frontleft5 Electricactiverollstabilizationfront(EARSVV)6 Controllableshockabsorber,frontright7 DynamicStabilityControl(DSC)
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Index Explanation8 Controllableshockabsorber,rearright9 VerticalDynamicsPlatform(VDP)controlunit10 Electricactiverollstabilizationrear(EARSVH)11 Controllableshockabsorber,rearleft
Inordertopreparethechassisandsuspensionforthedifferentroadconditionsasearlyaspossible,thefollowingdataisreadinfromvariouscontrolunitsandprocessedtoallowpredictivecontrol:
• IfADAPTIVEdrivingmodehasbeenactivatedviathedrivingexperienceswitch,theDynamicStabilityControlcontrolunitprocessesthenavigationdatatoanalysestherouteandinfluencesthedrivingprogramtobeactivatedifnecessary.Ifthevehicleisapproachingasharpbendathighspeed,forexample,theDynamicStabilityControl(DSC)activatesSportmodewithoutanyactiononthepartofthedriver.TheVerticalDynamicsPlatform(VDP)readsinthisinformationandactivatesthecorrespondingchassiscomponentsforSportmode.Conversely,anautomaticchangeindrivingprogramfromSporttoComfortisalsopossible.Ifthevehicleexitsatwistingsectionofroadthroughwhichithasbeendrivenatspeedandthendrivesatconstantspeedonastraightsection,thisresultsinautomaticchangeovertotheComfortdrivingprogram.Thismeansthattheoptimumdrivingmodewithrespecttocomfort(Comfort)anddrivingdynamics(Sport)isautomaticallysetwithoutmanualoperationofthedrivingexperienceswitchdependingonthedrivingstyleandprobableroute.Routeguidanceneednotbeactivatedforthis.
• TheVerticalDynamicsPlatform(VDP)readsintheinformationofthestereocamerainthewindscreenindependentlyoftheselecteddrivingmodeandprocessesthis.
Inaddition,alargequantityofadditionalinformationsuchasthedrivingstyleanalysisisreadinbytheVerticalDynamicPlatform(VDP)controlunitandusedforpredictivecontrolofthestandardElectronicDamperControl(EDC)aswellastheelectricactivestabilizers(EARSV).
Obstaclescanthereforebeovercomepredictivelyandwithevenmorecomfort.Thedriverisevenlessawareofbumps.Thebodyofthevehicledoesnothavetomoveverticallytothesameextentsincethechassisandsuspensionreactintelligentlyandpredictivelytoroadbumps.
Theoptionalchassisandsuspensionpackage“ActiveComfortDrive”thereforeoffersthefollowingadvantages:
• Reducedcompressionandrebound(EDC).• Reducedpitchmovement(EDC).• Fasterdecayofvehiclebodyreverberations(EDC).• Highdrivingdynamicswhencorneringthankstoactiverollstabilization(EARSV).• Highcomfortforstraight-aheaddrivingduetodecouplingofanti-rollbarhalves
andthusavoidanceofroadbump"copying"(EARSV).
Thefunctionsofthechassisandsuspensionpackage"ActiveComfortDrive”areavailableindifferentformsinthefollowingpositionsofthedrivingexperienceswitch.
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Drivingexperienceswitchposition
ElectricactiverollstabilizationEARSV
ElectronicDamperControl(EDC)
COMFORTPLUS Balanced ComfortableComfort/ECOPRO Balanced BalancedSport Sporty Sporty
Asaresultofintelligentnetworkingofthesystems,failureofonesensorsystem,e.g.thestereocameraduetopoorvisibility,canbesufficientlycompensatedbytheotheravailablesensors.Theridecomfortanddrivingdynamicsthusremainataveryhighlevelunderallconditions.
Thefollowinggraphicshowsaninputandoutputdiagramofthevariouscomponentsforcontroloftheoptionalchassisandsuspensionpackage“ActiveComfortDrive”intheG12.
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Inputandoutputdiagramoftheoptionalchassisandsuspensionpackage“ActiveComfortDrive”intheG12
Index Explanation1 VerticalDynamicsPlatform(VDP)2 Electricactiverollstabilizationfront(EARSVV)3 Electricactiverollstabilizationrear(EARSVH)4 ElectronicDamperControl(EDC)(4x)5 Steeringangle(EPS)6 Navigationdata7 Wheelspeeds(DSC)
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Index Explanation8 Wheelaccelerations9 Rideheights10 Drivingmode11 Roadprofile(stereocamera)12 Lateralandlongitudinalaccelerationandyawrate(ACSM-Low)13 Vehiclespeed
6.6.2.Electricactiverollstabilization(EARSV)Asthefirstvehiclemanufacturerworldwide,BMWuseselectricactivestabilizersinsteadofthepreviouslyusedhydraulicactivestabilizers.Theelectricactivestabilizersintheoptionalequipment“ActiveComfortDrive”(SA2VS)reducetherolltendencyofthebodyinbendsbytargetedapplicationofmechanicalmomentsonthestabilizerhalvesbymeansofanelectricmotor.
Thefollowinggraphicshowsaschematicsystemcomparisonbetweentheactivehydraulicstabilizerandtheactiveelectricstabilizer.
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Schematiccomparisonofhydraulicactivestabilizerandelectricactivestabilizer
Index ExplanationA HydraulicactivestabilizerARS(F01/F02)B ElectricactivestabilizerEARSV(G12)1 Engineoilcooler2 Hydraulicactivestabilizerfront(ARS)3 Expansiontank4 Hydraulicpump5 Valveblock6 VerticalDynamicsManagementcontrolunit(VDM)7 Hydraulicactivestabilizerrear(ARS)8 Electricactiverollstabilizationfront(EARSVV)9 12Vbattery(vehicleelectricalsystemsupport)
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Index Explanation10 Vehicleelectricalsystem11 PowerControlUnitPCU(DC/DCconverter500W)12 VerticalDynamicsPlatform(VDP)controlunit13 Electricactiverollstabilizationrear(EARSVH)
Electrificationoftheactivestabilizeroffersthefollowingadvantages:
• Simpleintegrationin“fullhybrid”drivesystemsActiverollstabilizationispossibleduringpurelyelectricdriving.
• Simpledecouplingofthestabilizerhalvesduringstraight-aheaddrivingImprovedridecomfortduetopreventionofroadbump"copying"
• IncreasedefficiencyEnergyisrequiredexclusivelyduringthecontrolactionsanddoesnotneedtobekeptpermanentlyavailablelikeinahydraulicsystem.Self-aligningforceswhichactontheelectricmotorinthestabilizercanbepartiallyconvertedintoelectriccurrentandfedbackintothevehicleelectricalsystem.
SystemoverviewofelectricactiverollstabilizationEARSV
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Index Explanation1 Electricactiverollstabilizationfront(EARSVV)2 Wheelaccelerationsensor,frontright3 12Vbatteryinenginecompartment(vehicleelectricalsystemsupport)4 Wheelaccelerationsensor,rearright5 VerticalDynamicsPlatform(VDP)6 Rearrightpowerdistributionbox7 PowerControlUnit(PCU)(DC/DCconverter500W)8 Electricactiverollstabilizationrear(EARSVH)9 Wheelaccelerationsensor,rearleft10 Wheelaccelerationsensor,frontleft
Aparticularadvantagewhichcontributesabovealltoincreasingridecomfortisthepreventionofso-called"copying".Whenthevehicleisdrivingstraight-aheadanddrivesoverroadbumps,electricactiverollstabilizationEARSVpermitspracticallyfulldecouplingoftheleftandrightsidestothatcopyvibrationsarealmostexcluded.Theelectricactivestabilizersthereforecompensateforthedisadvantagesofconventionalanti-rollbars.
Thefollowingvariablesaremainlyusedforcalculationoftherequiredactivationoftheelectricactivestabilizers.
• Currentlateralandlongitudinalacceleration• Vehiclespeed• Steeringangle• Wheelacceleration• Rideheights
Theincipientrollmoment(Mw)israpidlycounteractedbyfastprocessingofthedataandactivationofelectricactiverollstabilization(EARSV).
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SectionalviewofanelectricactivestabilizerintheG12
Index Explanation1 Groundconnection2 Electricalconnection3 Controlunit(EARSVV/EARSVH)4 Electricmotor5 Planetarygear(three-stage)6 Decouplingelement7 Anti-rollbarlink8 Torquesensor
TheactivestabilizersreceivethecontrolrequestfromtheVerticalDynamicsPlatform(VDP)controlunit.Thebustelegramsarereadinandprocessedbythecontrolunitsofthetwoactivestabilizers(EARSVV/EARSVH).Thetwostabilizerhalvesaretwistedwithrespecttoeachotherbyactivationoftheelectricmotor.Centralenergyconversiontakesplaceinthepermanentlyexcitedsynchronousmotor,whosedirectionofrotation,torqueandspeedarecontrolledviathesetrotatingfield.
Powertransmissiontakesplaceviathethree-stageplanetarygear,whichconvertsthetorqueoftheelectricmotortotherequiredstabilizeroutputtorsiontorquewitharatioof1:158.Amaximumstabilizertorsiontorqueof750NmiscurrentlyimplementedintheG12.Thesystemisdesignedforsignificantlyhighertorsiontorquesinordertoalsopermitcompensationofsuperpositioneffectsduetoroadbumps.
Theelastomerdecouplingelementbetweentheplanetarygearandstabilizertorsionspringhasthetaskofdecouplinghighlydynamic,low-amplitudeexcitationsfromtheroad.Thisthusmakesafurthercontributiontomeetingthehighcomfortgoals.
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Atorquesensorinsidethecomponentprovidesfeedbackonthecurrentcontroltorquestothecontrolunit.Aplausibilitycheckofthedataallowsvariousfaultstobedetectedandthenstoredintheformofafaultcodeentry.However,repairofthecomponentisnotpossible.Theactiveelectricstabilizermustbereplacedasacompleteunitintheeventofamechanicalcomponentdefect.
Sincetheelectricactivestabilizerwillbeavailableinothervehiclemodelsinfuture,thecontrolunitmustbetaughtfortherespectivevehiclebymeansofversionencodingafterinstallation.Thisensuresthattheelectricactivestabilizerprovidesthecorrectcontroltorquesforthevehicleinquestion.
Technicaldata
Thefollowingtableprovidesanoverviewofthetechnicaldataoftheelectricactivestabilizer.
ElectricactiverollstabilizationEARSV TechnicaldataWeight 14 kg/30lbsMaximumcontrolunittemperature 120 °C/248°FMaximumelectricmotortemperature 160 °C/320°FMaximumelectricmotortorque 7.5Nm/5.5ft-lbsMaximumstabilizertorque 750Nm/553ft-lbsMaximumcurrentconsumption 120AMaximumcurrentoutput -100A
Thevaluesformaximumcurrentconsumptionandmaximumcurrentoutputarethevaluesthatarepossibleforshort-timeoperation.
CurrentconsumptionandcurrentoutputoftheelectricactivestabilizerintheG12
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Theabovegraphicshowsthecurrentconsumptionandoutputoftheelectricactivestabilizerforadrivingmanoeuvrewithapproximately30 %energyrecovery.Itmustbenotedthatthisdiagramisjustasnapshotrepresentation.Dependingonthedrivingmanoeuvre,theactivationpowerandenergyrecoveryoftheelectricactivestabilizermaydifferconsiderably.
FunctiondiagramoftheDC/DCconverterintheG12
Index ExplanationA 12VvehicleelectricalsystemB Consumesofelectricactivestabilizers1 Startermotor2 Alternator3 12 Vbattery4 Consumersofthe12Vvehicleelectricalsystem5 PowerControlUnit(PCU)(DC/DCconverter500W)6 12Vbatteryinenginecompartment(vehicleelectricalsystemsupport)7 Electricactiverollstabilizationfront(EARSVV)8 Electricactiverollstabilizationrear(EARSVH)
Inordertoensurethattheconsumersofthe12VvehicleelectricalsystemintheG12arenotinfluencedbythehighloadcurrentsofthetwoelectricactivestabilizers,thestabilizershavebeenisolatedfromthebasisvehicleelectricalsystembymeansofaDC/DCconverter(500W).
Therequireenergyforactivationisprovidedbyanadditional12Vbatterylocatedintheenginecompartment.Thismeansthatotherconsumersarenotaffectedbythehighenergyconsumption.
Thebatteryisanauxiliarybatterwhichsuppliesthevehicleelectricalsystemwithpowerdependingonthevehicleequipment.Forthisreason,thebatterymayalsobepresentevenifthevehicleisnotequippedwithelectricactivestabilizers.
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6.6.3.ControlstrategyVehicledrivabilitywhencorneringcanbegreatlyinfluencedbyanti-rollbarsonthefrontandrearaxles.Adecisivefactorhereistherollmomentratiobetweenthefrontandrearvehicleaxles.Thisratiodependsontherespectiveanti-rollbarmomentsofthetwoaxles.
Thefollowingtableprovidesanoverviewofthepossiblerollmomentratiosandtheresultanthandlingofthevehicle.
Anti-rollbar Rollmomentratio Understeer OversteerFrontaxlesoft/rearaxlehard
<50% X
Frontaxlehard/rearaxlesoft
>50% X
Thefollowinggraphicshowsthepercentagedistributionofthestabilizermoments(rollmomentratio)oftheactivestabilizersonthetwovehicleaxles.
Characteristiccurveofactivestabilizeronfrontandrearaxles
Index ExplanationA UndersteeringrollmomentratioB NeutralrollmomentratioMain[%] Momentdistributionofactivestabilizersinpercentvin[km/h] Drivingspeedinkilometersperhour1 Activestabilizeronthefrontaxle2 Activestabilizerontherearaxle
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Theactivestabilizerallowstherollmomentratiotobeadaptedtotherespectivedrivingsituationinordertoincreasethedrivingdynamics.Therollmomentratiois50 : 50(neutral)inthelowerspeedrange(0 ~ 50km/h).Therollmomentratioisadjustedtowardsundersteerwithincreasingspeed.
Applicationofrollmomentsviatheactivestabilizerinfluencesthecorneringforcesthatcanbetransferredbythetires.
Thefollowinggraphicshowsthemaximumcorneringforcesthatcanbetransferredwhencorneringasafunctionoftheappliedstabilizermoments.
Diagramofapositiverollmomentratiothroughcontrolvia2activestabilizers
Index ExplanationA LargemomentoftheactivestabilizeronthefrontaxleB LowmomentoftheactivestabilizerontherearaxleC IncreaseintransferablecorneringforceatthewheelD ReductionintransferablecorneringforceatthewheelE ResultanttransferablecorneringforceatthewheelsofanaxleFS TransferablecorneringforceatthewheelFN VerticalwheelforceHL Forceofactivestabilizeratrearleftwheel
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Index ExplanationHR ForceofactivestabilizeratrearrightwheelMa ActivestabilizermomentVL ForceofactivestabilizeratfrontleftwheelVR Forceofactivestabilizeratfrontrightwheel
Whencornering,acounter-torque(Ma)isappliedbytheactivestabilizerstocounteracttheactingrollmoment(Mw).Themoments(Ma)applieddependingontheactionoftheactivestabilizerseitherincreaseorreducethetirecontactforcesofthedifferentwheels.
Ifawheelisloadedwithaparticularlyhighforcebytheactivestabilizer,itstransferablecorneringforceincreasesduetothehighertirecontactforce.Incontrast,theloadontheoppositewheelisrelieved,anditscorneringforceisthusreducedduetothelowertirecontactforce.Theresultanttirecontactforcescharacterisethetransferablecorneringforcesofthewheelsonanaxle.
Sincethereductioninthetransferablecorneringforcesoftherelievedwheelisproportionatelyhigherthantheincreaseinthetransferablecorneringforcesoftheloadedwheelasaresultofincreasingactivestabilizerforce,thismeansthatthereisareductionintheresultantcorneringforceofthewheelsonthisaxle.
Inthedirectcomparisonofthetwoaxlesintheabovediagram,itcanbeseenthattherearaxlecantransferahigherresultanttransferablecorneringforcethanthefrontaxle.Inthelimitrange,thevehiclewouldthereforepushoverthefrontwheels,i.e.understeer.
Itiseasierforaninexperienceddrivertoregaincontroloverthevehicleagaininthissituationthanifthevehicleweretooversteer(vehicleskidsattherearaxle).
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6.6.4.SystemwiringdiagramofelectricactiverollstabilizationEARSV
SystemwiringdiagramofelectricactiverollstabilizationEARSVintheG12
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Index Explanation1 Wheelaccelerationsensor,frontleft2 Electricactiverollstabilizationfront(EARSVV)3 Powerdistributionbox,enginecompartment4 Wheelaccelerationsensor,frontright5 12Vbatteryinenginecompartment(vehicleelectricalsystemsupport)6 BodyDomainController(BDC)7 Powerdistributionbox,frontright8 VerticalDynamicsPlatform(VDP)9 Wheelaccelerationsensor,rearright10 Rearrightpowerdistributionbox11 Electricactiverollstabilizationrear(EARSVH)12 Wheelaccelerationsensor,rearleft13 KAFAScameracontrolunit14 Stereocamera
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