8.2.1
Overview
This section describes the available powertrain modules provided with the ‘Generic’ library. The models of this library are highly configurable and should meet the needs of the most common configurations.
Supported configurations
Basically powertrain configurations are distinguished by the number of driven wheels and in addition to this by the number of differential gears used.Figure 8.5gives an overview of the available configurations:
The standard front and rear drive configurations use one differential gear to distribute the torque from the drive shaft to the wheels (either at the front or at the rear axle). The 4WD configuration uses one differential gear for every axle and a center differential gear for dis- tributing torque to the front and rear axle. The hanged on configurations also have differen- tial gears for front and rear axle but use a coupling for transferring torque to the hanged on axle. This means that with opened center coupling this configuration acts like a standard front or rear drive.
PowerTrain.Kind Description
GenFront standard front drive vehicle GenRear standard rear drive vehicle
Gen2p2Front front driven vehicle with rear axle hanged on Gen2p2Rear rear driven vehicle with front axle hanged on Gen4WD four wheel drive vehicle
Figure 8.5: Configurations overview
Front Drive: Rear Drive: GenFront Gen2p2Front Gen4WD Gen2p2Rear GenRear
Powertrain ’Generic’
Supported coupling configurations
In addition to this there are several possibilities to add different types of couplings between different shafts of the differential gears in the drive line:
Figure 8.6: Configuration possibilities for powertrain couplings
left2right in2left in2right
left2right in2left in2right
front2rear in2front in2rear
Front: Center: Rear: hangon i i
Powertrain ’Generic’
There are several types of couplings for different purposes available. They can be config- ured for each individual coupling shown inFigure 8.6:
Visco Coupling As a matter of principle a visco coupling is only able to transfer torque if there is a rotation speed difference between both sides of the coupling. This is because a fluid is used for torque transmission like in a hydrodynamic torque converter (Föttinger-Coupling). This means there is no state where a visco coupling is sticking, there has to be slip for torque transmission.
For simulation purposes a torque characteristic as a function of rotating speed difference is used. The coupling torque is calculated by:
(EQ 31)
A typical characteristic may look like inFigure 8.7
Torque Sensing Coupling
The coupling torque (locking torque) depends on the torque difference between the two coupled shafts.
The torque sensing coupling is only useful for the mount positions left2right and front2rear. Figure 8.8 displays the mount position left2right.
T = f(∆ω˙)
Figure 8.7: Typical characteristic for a visco coupling rotation speed difference
tr
ansf
erred torque
0 ∆ω˙
T
Figure 8.8: Principal torque sensing coupling TCage
TLock
THigh TLow
Powertrain ’Generic’
With torque sensing couplings there are two common characteristic values. The torque bias and locking ratio are defined as:
(EQ 32)
(EQ 33)
If then applies for a standard differential gear. If exists the torques calculate to:
(EQ 34)
With(EQ 32),(EQ 33)and(EQ 34)a relationship between torque bias and locking ratio can be determined:
(EQ 35)
The CarMaker implementation of a torque sensing coupling uses a torque bias value as input for each the driven ( ) and undriven ( ) case.
Locked Coupling This is not a real coupling. It acts like a rigid connection between input and output shaft. It is useful for simulating a locked differential or testing purposes. No matter which mount position is chosen the differential is lock in either case. There are no parameters needed for this coupling.
DVA Locked With this coupling the locking torque for the configured couplings can be given via modifi- cation of DVA quantities.
TB THigh TLow --- = LR TLock TCage --- =
TLock = 0 THigh TLow 1
2 ---TCage = = TLock TLow 1 2 --- T( Cage–TLock) = THigh 1 2 --- T( Cage+TLock) = LR TB 1– TB+1 --- = TCage≥0 TCage<0
Powertrain ’Generic’
8.2.2
General Parameters
PowerTrain.Kind = KindStr
With this parameter a powertrain model is selected. The powertrain ‘Generic’ library pro- vides the following models:
Example PowerTrain.Kind = GenRear
PowerTrain.ET.Kind = ETKindStr
PowerTrain.Clutch.Kind = ClutchKindStr
PowerTrain.GearBox.Kind = GearBoxKindStr Selecting powertrain ’Generic’ sub models, seesection 8.3 ’Engine Torque’ on page 110, seesection 8.4 ’Clutch’ on page 120 and seesection 8.5 ’Gear Box’ on page 128.
Inertias
PowerTrain.Engine.I = value
PowerTrain.Clutch.I_in = value
All parts of the clutch which should be added up to the engine mass substitute.
PowerTrain.Clutch.I_out = value
All parts of the clutch which should be added up to the wheel mass substitute if the trans- mission is in gear.
PowerTrain.Kind Description
GenFront standard front drive vehicle GenRear standard rear drive vehicle
Gen2p2Front front driven vehicle with rear axle hanged on Gen2p2Rear rear driven vehicle with front axle hanged on Gen4WD four wheel drive vehicle
Powertrain ’Generic’
PowerTrain.GearBox.I_in = value
All parts of the gearbox which are not added up to the wheel mass substitute. Measured when transmission is in neutral.
PowerTrain.GearBox.I_out = value
All parts of the gearbox which are added up to the wheel mass substitute. Measured when transmission is in neutral.
PowerTrain.DriveLine.I_in = value
Powertrain ’Generic’
8.2.3
Model ‘Generic’ Differential Parameters
Differential Models ‘Front’ or ‘Rear’
Depending on the powertrain configuration a differential gear is used either for front or rear or both axles.
‘F’ means front, ‘R’ means rear.
PowerTrain.DL.FDiff.I_in = value
PowerTrain.DL.RDiff.I_in = value Inertia of the input shaft
PowerTrain.DL.FDiff.I_out = value
PowerTrain.DL.RDiff.I_out = value Inertia of the output shaft
PowerTrain.DL.FDiff.I_Cage = value PowerTrain.DL.RDiff.I_Cage = value
Optional. Inertia of the differential cage. Default: 0
PowerTrain.DL.FDiff.i = value
PowerTrain.DL.RDiff.i = value Transmission ratio from input shaft to cage.
Example PowerTrain.DL.FDiff.i = 3.5
PowerTrain.DL.FDiff.Cpl.Kind = KindStr
PowerTrain.DL.RDiff.Cpl.Kind= KindStr
Optional. Select a coupling model. Default: no coupling is used. Possible values are:Visco, TrqSensing, Locked, DVA_Locked
PowerTrain.DL.FDiff.Cpl.Mounting = MountPos
PowerTrain.DL.RDiff.Cpl.Mounting= MountPos Optional. Select mounting position.
Possible values are:left2right,in2left,in2right Default:left2right.
Powertrain ’Generic’
PowerTrain.DL.FDiff.Cpl.k PowerTrain.DL.RDiff.Cpl.k
Optional. Stiffness used for numerical stability when switching from stick to slip. Default: 10
Differential Model ‘Central’
A center differential is only available for Model ‘Gen4WD’.
PowerTrain.DL.CDiff.I_in = value Inertia of the input shaft
PowerTrain.DL.CDiff.I_out_front = value Inertia of the front output shaft
PowerTrain.DL.CDiff.I_out_rear = value Inertia of the rear output shaft
PowerTrain.DL.CFDiff.I_Cage = value Optional. Inertia of the differential cage. Default: 0
PowerTrain.DL.CDiff.i_in2cent = value
Transmission ratio from input shaft to cage of the center differential.
Example PowerTrain.DL.CDiff.i_in2cent = 1.0
PowerTrain.DL.CDiff.TrqRatio_front = value
Powertrain ’Generic’
PowerTrain.DL.CDiff.Cpl.Kind = KindStr Select a coupling model.
Possible values are:Visco, TrqSensing, Locked, DVA_Locked
PowerTrain.DL.CDiff.Cpl.Mounting = MountPos Optional. Select mounting position.
Possible values are:front2rear, in2rear, in2front Default:front2rear.
PowerTrain.DL.CDiff.Cpl.k = value
Powertrain ’Generic’
8.2.4
Model ‘Generic’ Coupling Parameters
Coupling Model ‘Visco’
‘F’ means front, ‘R’ means rear, ‘C’ means center.
PowerTrain.DL.FDiff.Cpl.Trq_Amplify = value
PowerTrain.DL.RDiff.Cpl.Trq_Amplify = value
PowerTrain.DL.CDiff.Cpl.Trq_Amplify = value
PowerTrain.DL.HangOn.Cpl.Trq_Amplify =value
Amplifies the determined value by a given factor
PowerTrain.DL.FDiff.Cpl.Trq_drotv = value
PowerTrain.DL.RDiff.Cpl.Trq_drotv = value
PowerTrain.DL.CDiff.Cpl.Trq_drotv = value
PowerTrain.DL.HangOn.Cpl.Trq_drotv = value
Characteristic for coupling torque as a function of the rotation speed difference:
.!
Coupling Model ‘Locked’
No parameters are necessary!Coupling Model ‘TrqSensing’
PowerTrain.DL.FDiff.Cpl.TrqBias_Driven = value
PowerTrain.DL.RDiff.Cpl.TrqBias_Driven = value
PowerTrain.DL.CDiff.Cpl.TrqBias_Driven = value
Specify torque bias value for drive case driven. Value has to be >= 1.
Example PowerTrain.DL.FDiff.Cpl.TrqSensing.TrqBias_Driven = 1.3
PowerTrain.DL.FDiff.Cpl.TrqBias_Dragged = value
PowerTrain.DL.RDiff.Cpl.TrqBias_Dragged = value
Syntax Infofile table mapping with 2 columns <rotation velocity difference> <torque>
Powertrain ’Generic’
Coupling Model ‘DVA_Locked’
No extra parameters needed for coupling model ‘DVA_Locked’! The coupling torque can be set by accessing DVA variables (Seesection 12.3.2 on page 268).
Coupling Model for Configurations ’Gen2p2Front’ and ’Gen2p2Rear’
One axle is driven, the other one is hanged on. It is parametrized with basic parameters, extended by a hang on coupling.PowerTrain.DL.HangOn.I_in = value Inertia of the input shaft
PowerTrain.DL.HangOn.I_out = value Inertia of the output shaft
PowerTrain.DL.HangOn.i = value
Transmission ratio between gearbox and hangon coupling
Example PowerTrain.DL.Hangon.i = 1.0
PowerTrain.DL.HangOn.Cpl.Kind = KindStr
Select a coupling model.
Possible values are:Visco, Locked, DVA_Locked
PowerTrain.DL.HangOn.rotv_open = value
Only for configuration Gen2p2Front! Optional. With this parameter it is possible to imple-
ment a disconnect unit for the rear axle. When the vehicle is dragged and the rotation speed is above the specified value the disconnect unit applies. Default: 1e38 (this means no dis- connect unit is installed)
Example PowerTrain.DL.HangOn.rotv_open = 100
PowerTrain.DL.HangOn.Cpl.k = value
Engine Torque