Overview
The clutch calculates the torque transfer from the engine to the gearbox input shaft consid- ering the clutch pedal or ECU signals.
PowerTrain.Clutch.Kind = KindStr
Selection of the clutch subsystem to use. The powertrain components library provides the following submodels:
Example PowerTrain.Clutch.Kind = Manual Figure 8.13: Clutch Model
Engine Clutch Gearbox
Clutch Pedal ECU Signals TEngine TClutch2GearBox q q˙, Gearbox q q˙, Engine Powertrain.Clutch.Kind Description
Converter torque converter model usually used in combination with automatic transmissions
Manual manual clutch model usually hand-operated by the driver DVA Clutch torque is modified via DVA access
Clutch
8.4.1
Clutch Model ‘Manual’
A manual clutch in reality consists of two plates a friction plate and a contact pressure plate. The transmissible torque depends of the contact pressure and the speed difference between the two plates. In a real time environment with fixed step integrators modeling a technical system like a clutch is a challenging task. With conventional methods usually problems occur when transiting from slip to the singularity stick and vice versa. For a better computation stability the modeling approach of the clutch in this powertrain is sightly more complex.
Figure 8.14shows the non physical approach of this model which uses three plates for transmitting the torque from the engine to the gearbox. The plates form engine side to gear- box side are called “input-”, “friction-” and “output-plate”. The “input-” and the “friction-plate” form a system with pure friction which is used to cover the case clutch is opened respec- tively is slipping. The remaining two plates form the counterpart for the closed clutch where a spring loaded force element is added to the friction part.
Both parts of this clutch system contribute their moment to the resulting clutch moment which is transmitted through the clutch:
(EQ 37)
To determine how much every system is contributing (or which case applies the most at one stage) a weighting function is used.
Internally a normalized pedal position withinConnectPosandDisconnectPosis used. BelowConnectPosno torque is transmitted and aboveDisconnectPosthe clutch is fully closed.
(EQ 38)
The factor x in(EQ 38)is estimated so that the range [0 .. 1] is adhered. A simple weighting function is derived from the normalized pedal position:
(EQ 39)
Figure 8.14: Structure of Clutch Model Manual
ω ω,
˙
ωIn,ω˙In ωOut,ω˙OutT
ωFp,ω˙Fp⇒
Engine
⇒
Gearbox
TIn2Fp TFp2In friction plateinput plate output plate
{ {
Case: open Case: closedTIn2Out = TfIn2Fp+TkdFp2Out
PedalPosNorm = x PedalPos ConnectPos( – )
Clutch
• Calculation of the case “clutch open”:
(EQ 40) (EQ 41)
is the maximum transmittable torque for the case clutch open. The real transmit- ted torque calculates to:
(EQ 42)
• Calculation of the case “clutch closed”:
This case makes the assumption that the speed of the “input-” and the “friction plate” are equal . This also means that following(EQ 40)and(EQ 42) calcu- lates to zero and only this part is contributing the torque transmission.
(EQ 43) (EQ 44)
With
(EQ 45)
the transmitted torque calculates to:
(EQ 46)
Parameters
PowerTrain.Clutch.ConnectPos = value
Optional. At this clutch pedal position the clutch starts transferring torque. Default: 0.3 [0 .. 1].
Example PowerTrain.Clutch.ConnectPos = 0.3
PowerTrain.Clutch.DisconnectPos = value
Optional. At this clutch pedal position the clutch starts slipping when opening. Default: 0.7 [0 .. 1]
Example PowerTrain.Clutch.DisconnectPos = 0.7
∆ω˙In2Fp = ω˙Fp–ω˙In Tfmax = (1.0–λ)⋅Trq_max_fric
Tfmax
TfIn2FP = min T( fmax ,d_fric⋅–ω˙In2Fp)
ω˙Fp≡ω˙In TfIn2Fp
∆ω˙Fp2Out = ω˙Out–ω˙In
∆ωFp2Out = ωOut–ωFp
Tkdmax = (1.0–λ)⋅Trq_max
Clutch
Alternatively the maximum transmissible torque can be set independently with the following two parameters.
PowerTrain.Clutch.Trq_max_fric = value
Optional. Maximum transmissible torque when clutch is slipping.Default: 300.
Example PowerTrain.Clutch.Trq_max_fric = 300
PowerTrain.Clutch.Trq_max_kd = value
Maximum transmissible torque when clutch is closed.
Example PowerTrain.Clutch.Trq_max_kd = 300
PowerTrain.Clutch.d_fric = value
Optional, unit: Nm/deg. Friction coefficient for the case clutch is slipping.
Example PowerTrain.Clutch.d_fric = 0.0175
PowerTrain.Clutch.k_FP = value Optional, unit: Nm/deg; default: 1.6667 Nm/deg. Spring constant for the case clutch is closed.
Example PowerTrain.Clutch.k_FP = 1.6667
PowerTrain.Clutch.d_FP = value
Optional, unit: Nm s/deg. Friction coefficient for the case clutch is closed. Default: 0.1167
Example PowerTrain.Clutch.d_FP = 0.1167
Syntax PowerTrain.Clutch.Trq_max_kd = val [Nm] optional, default 300 Nm
Syntax PowerTrain.Clutch.d_fric =val [–]
Clutch
8.4.2
Clutch Model ‘Converter’
A hydrodynamic torque converter or Föttinger-Converter is able to reduce rotation speed and translate torque.
The input and output torque TIn,Outof the converter is calculated with the speed ratio depen- dent converter factors kIn, kOut and the input speedωIn.
(EQ 47)
The relation between the converter output- and the input-torque is often described with the torque ratioµ.
(EQ 48)
So, two characteristics kIn(s) andµ(s) respectively kOut(s) are used to represent the trans- mission behavior of the converter.
Those characteristics use the following parameter names in CarMaker input files:
Figure 8.15shows a typical gradient of the converter factor kInover the speed ratio nOut/nIn: kIn PowerTrain.Clutch.k_E
µ PowerTrain.Clutch.mue
TIn = kInωIn2 TOut = kOutωOut2
kIn,kOut= f s( ) mit s ωOut
ωIn --- = µ TOut TIn --- kOut kIn --- = =
Figure 8.15: converter factor kIn as a function of the rotation speed ratio rotation speed ratio nOut/nIn
con v er ter f actor k In (Nms 2 ) 0 1 0.98 1 e-4 1.7 e-3
Clutch
As depicted inFigure 8.16the maximum torque ratio (usually 1.9 to 2.5) for the driveway reduces with increasing rotation speed ratios. Above a certain speed ratio the torque ratio remains constantly shortly below 1 (because of losses). This case is called clutch mode.
Parameters
PowerTrain.Clutch.Adjust = value
For principal adaption of converter characteristics. This factor is multiplied with PowerTrain.Clutch.k_E.
This parameter needs to be 1 to obtain the given characteristic! Otherwise the characteristic for PowerTrain.Clutch.k_E is altered by this factor
Example PowerTrain.Clutch.Adjust = 1.0
PowerTrain.Clutch.k_E = Table
Characteristic for the input torque conversion factor.!
Figure 8.16: torque ratio as a function of the rotation speed ratio
torque r atio m = T out /T in 0 0.88 1 0.98 2.3
rotation speed ratio nout/nin
Syntax Infofile table mapping with 2 columns <nout/nin> <k_E>
Example PowerTrain.Clutch.k_E:
0.0 3.3e-4 0.3 3.2e-4 0.6 3.0e-4 0.9 2.2e-4 0.95 1.8e-4 0.975 1.2e-4 0.995 1.7e-5 1.0 0
Clutch
PowerTrain.Clutch.mue : = Table Torque ratio characteristic.
Syntax Infofile table mapping with 2 columns <nout/nin> <mue>
Example PowerTrain.Clutch.mue:
0.0 2.1
0.8 0.98
0.9 0.98
Clutch
8.4.3
Clutch Model ‘DVA’
This model is not a conventional clutch model. The transmissible torque is not determined by the rotations speed difference of the clutches input and output shaft and the pedal actu- ation.
The user can specify a torque by modifying a DVA variable.
(EQ 49)
This model decouples the engine model since only the user specified torque is transferred to the gearbox input shaft.
Parameters
This model has no parameters.
Figure 8.17: Clutch Model DVA
Clutch Gearbox
TClutch2Gearbox
q q˙, Gerarbox DVA PT.Clutch.DVA.Trq_A2B
Gear Box