schnellster and twinster®+

© GETRAG Driveline Systems GmbH, 16. – 18. June 2009, All rights reserved1

Active Yaw Systems: Re-experience Front Wheel Drive with SCHNELLSTER and TWINSTER®+

Peter Obergünner

2© GETRAG Driveline Systems GmbH, 16. – 18. June 2009, All rights reserved

Content

Introduction

Investigation of different driveline configurations

Functional Description- Speed lead SCHNELLSTER- Torque lead TWINSTER®+

Vehicle Performance Results - Low-µ- High-µ

Road Load Data Acquisition

Summary


Investigation of Different Driveline Configurations on a R53 MINI Cooper S


GETRAG MINI AWD Investigated Driveline Configurations

RWD RWD + Hang-On front

BOOSTER

FWD + Hang-On rear

BOOSTER

FWD + Hang-On + e-LSD

BOOSTER & TRACKSTER

RWD + Active Yaw front

TWINSTER®


GETRAG MINI FWD Investigated Driveline Configurations

FWDProduction

FWD +Passive LSD

FWD +e- LSD frontTRACKSTER

FWD +Active Yaw

TWINSTER®+

FWD +Active Yaw

SCHNELLSTER


Motivation for Development of FWD Active Yaw Systems


Motivation for Development of FWD Active Yaw Systems

Today's trend is to equip high performance AWD with AYC systems on rear axle to:- avoid AWD understeering- increase agility

Basically Active Yaw Function is independent from Front- or Rear Axle installation!FWD vehicles with open differentialAdvantage: high stability easy controllableDisadvantage: strong understeering when:

- high engine power installed or power independent- driving on µ-low (wet, snow, ice)

On FWD AYC cannot generate uncontrollable oversteering in power on - Light understeering at the limit is still there

- predictable, safe and easy controllableThe average driver can feel the performance improvement easily because AYC is not dependent on lateral acceleration or corner speed


Effects by Active Yaw System


„Kammscher“ CircleDuring Cornering with Constant Load: open Differential


„Kammscher“ CircleDuring Cornering with Constant Load: AYC System


Options to Generate a Yaw Moment on Vehicle's Cog


Options to Generate a Yaw Moment on Vehicle´s Cog

Superimposed planetary gear system (speed lead)- SCHNELLSTER

Coupling system (Torque lead)- TWINSTER®+

Single wheel brake interventionNot taken into account because of high energy losses

Clutch and gear systems can be introduced on- Front axle- Rear axle- Transfer case (AWD)

Not taken into account because of low efficiency


SCHNELLSTER and TWINSTER®+Influence on Yaw Behavior by Different Solutions

Yaw Moment by AYC

Rotational speed Wheel Force

Yaw Moment by AYC

SCHNELLSTER TWINSTER® +


SCHNELLSTERSuperimposed Planetary Gear SystemSpeed Lead


SCHNELLSTERSystem description Mechanical Part / Torque Flow

C1 C2

Input from diff. Carrier

3 Step Planetary Gear

Planetary Carrierwith integratedCoupling Function


SCHNELLSTERSystem description Hydraulic Part

HCA

X

X X

P UP U

)( )()( )(

One ActuatorPressure Controlled4-port/2-way valveNo AccumulatorNo Pressure limitation valveHigh DynamicHigh efficiency


SCHNELLSTERCurrent Lay Out for MINI R53

Planetary gear offset: 10%Max. delta Torque: 1400 NmWeight: 15 kgDrag Torque: < 2NmHydraulic Pressure Range: 0 – 45 barResponse times: < 100 ms


GETRAG TWINSTER® +TWIN Clutch SystemTorque lead


TWINSTER®+Approach

Approach- „Kammscher“ Circle

- Frontaxle transmits tractive forces (longitudinal) and steering forces (lateral)

- Assumption: during cornering without longitudinal wheel force vehicle drives on the “ideal” path

- Target: to compensate occurring understeering, through increasing longitudinal wheel force, by delta torque between inner and outer front wheel


TWINSTER®+Specific Previous Considerations about Torque Lead Systems

Feasibility Study- Thermal capacity of coupling

- delta speed during tight cornering- permanent slip during normal driving

- Coupling capacity- wheel slip torque needs to be achieved

- Torque steering effects- wheel delta torque can generate torque steering

- Efficiency- losses on coupling- HCA current consumption


TWINSTER®+System description Mechanic Part / Torque Flow

No Differential

Sideshaft left Sideshaft right

Coupling leftCoupling right


TWINSTER®+System description Hydraulic Part

Twin Coupling SystemValve controlledPressure demand dependent controlOne actuatorNo accumulatorNo pressure limitation valveHigh dynamicHigh efficiency

HCA

X X


TWINSTER®+Pressure Demand versus Vehicle Speed Current Lay Out for MINI

Vehicle Speed km/h

Engi

neTo

rque

Nm

Pre

ssur

eba

r

Engine TorquePressure Gear box clutchPressure TWINSTER® +

EfficientLess Efficient33% of RLD 66% of RLD


TWINSTER®+Current Lay Out for MINI R53

Skid Torque for each Coupling: 1800 NmWeight incl. HCA: 18 kgDrag Torque: < 2 NmHydraulic Pressure Range: 0 – 45 barResponse time: < 100 ms


TWINSTER®+Overview of System Potentials

Differential Function- eliminate differential (cost / weight compensation)

Gearbox Main Clutch Function - eliminate main clutch including actuation (cost / weight compensation)- different clutch characteristic possible (normal- sport or snow mode)

Torque Limiter Function- Protect drivline for overload- Eliminate stamping front axle (e.g. acceleration on wet asphalt)- Prevent for spinning front wheels - Provide best acceleration performance independent from friction coefficient

Limited Slip Differential (eLSD) FunctionActive Yaw Control

- Yaw support- Yaw damping

Friction Coefficient Detector Function- pressure mirrors transmittable wheel torque

Freewheel Function (sailing)- switch engine in coast off (fuel saving)- decouple while Braking or during ABS/ESP intervention

Hybrid- instead of eliminated coupling this area can be used for a hybrid disc

Cost reduction by Integration into DCT - one ECU - one hydraulic system- same pressure control valves


TWINSTER®+Weight compensation potential by integration into man. transmission

Weight reduction:• Differential • Clutch• Actuation

-9.0 kg

External solution:• HCA: 2 kg• TWINSTER®+: 16 kg• :overall 18 kg

Add 9.0 kg


With integration:• HCA: 2 kg• TWINSTER®+: 8 kg• overall: 10 kg

+ 1.0 kg

Weihgt reduction:• Differential • Transm. Clutch• Actuation

-9.0 kg

TWINSTER®+Weight compensation potential by integration into man. transmission


Vehicle Test Resultsµ-low


Self-steering behavior, packed Snow, Circle dia= 230mOpen, SCHNELLSTER, TWINSTER®+

05

101520253035404550556065707580859095

100105110

°

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5m/s2Lateral Acceleration

Stee

ring

Angl

e

TWINSTER®+OPEN SCHNELLSTER


WOT from Steady State Cornering, packed Snow, Circle dia= 230mOpen, SCHNELLSTER, TWINSTER®+

10

20

30

40

50

60

70

80

90

100

110

120

130

14010^-3 rad/s

0.5 1.0 1.5 2.0 2.5

s

OPEN

TWINSTER®+

SCHNELLSTER

Understeering

Neutral

Self-steering behaviorYa

wsp

eed


0

50

100

150km/h

0

5

10bar

0

5

10

15°

0

50

100 %

1 0kN

WOT Acceleration on split-µTWINSTER®+ Steering angle demand for yaw compensation

max. steering angle 8°

„select low pressure“

wheelspeed

coupling pressure

24 26 28 30 32

s

throttlepossteering angle Throttle pos


Vehicle Test Resultsµ-high


Self-steering behavior µ-high, dry asphalt, circle r=80 mOpen, SCHNELLSTER, TWINSTER®+

05

101520253035404550556065707580859095

100105110115120125

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.510.0

Lateral Acceleration m/s²

Stee

ring

Angl

e °

OPEN

TWINSTER®+

SCHNELLSTER


Position Plot, Steer Step Input in WOT, 50 km/h, dry Asphalt, 2. Gear, Open, SCHNELLSTER, TWINSTER®+

-75

-70

-65

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0sm

-70 -60 -50 -40 -30 -20 -10 0

sm

OPEN

TWINSTER®+

SCHNELLSTER


Vehicle Test ResultsRoad Load Data Acquisition TWINSTER® +Thermal Capacity


-15

-5

5

15m/s2

0

500°

0

100

200

300kmh

0.0

62.5

125.0°C

3.8 3.9 4.0 4.1 4.2 4.3

10^3 s

TWINSTER®+ Road Load Data Acquisition: Nürburgring North loop (Race style)

Average Pressure: 10.3 barAverage Delte Speed: 5.5 1/minAverage Coupling Torque: 420 NmAverage Vehicle Speed: 126 km/h

Average Power Losses: 241 WMax. Oilsumptemperature: 109 °CEnergy per km: 4.9 kJ/km


TWINSTER®+ Public Roads Country (normal style) 120 km Distance

-20

0

20m/s2

0

500°

0

100

200kmh

60

70

80

90°C

0 1 2 3 4 5 6 7

10^3 s

Average Pressure: 6.7 barAverage Delta Speed: 2.1 1/minAverage Coupling Torque: 130 NmAverage Vehicle Speed: 57 km/h

Average Power Losses: 35 WMax. Oilsumptemperature: 73°CEnergy per km: 2.2 kJ/km


TWINSTER®+ Nürburgring North loop (race style)Pressure Distribution left Coupling versus Vehicle Speed

Freq

uenc

y%

Pressure bar


TWINSTER®+ Public Roads Country (normal style)Pressure Distribution left Coupling versus Vehicle Speed

Freq

uenc

y%

Pressure bar


Summary


12

52

40

16

43

0

10

20

30

40

50

60

Impr

ovem

ent %

eLSD TWINSTER + SCHNELLSTER AWD Hang on AWD TWINSTER

TWINSTER®+ improvement with Utilization of PotentialsComparison to FWD “open Differential” and other Driveline Systems

Improvement by utilizationof additional potentials

TWINSTER®++ AWDTWINSTER®SCHNELLSTER


Summary

On FWD Active Yaw Systems are feasible and provide an outstanding new handling behavior Active Yaw Control improves traction and handling independent from lateral acceleration or corner speed- Typical FWD understeering behavior can be impressively reduced

- behavior is transparent, predictable and easily controllable- Every driver can experience the benefits without being an

experienced sport driverUnique selling point for the OEM to differentiate from other competitorsBy utilization of all potentials of the TWINSTER®+ the system can become the future “differential” in FWD

schnellster and twinster®+

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