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

Active Yaw Systems: Re-experience Front Wheel Drive with SCHNELLSTER and TWINSTER + Peter Obergünner 1

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 2

Investigation of Different Driveline Configurations on a R53 MINI Cooper S 3

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 4

GETRAG MINI FWD Investigated Driveline Configurations FWD FWD + FWD + FWD + FWD + Production Passive LSD e- LSD front Active Yaw Active Yaw TRACKSTER TWINSTER + SCHNELLSTER 5

Motivation for Development of FWD Active Yaw Systems 6

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 differential Advantage: high stability easy controllable Disadvantage: 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 controllable The average driver can feel the performance improvement easily because AYC is not dependent on lateral acceleration or corner speed 7

Effects by Active Yaw System 8

Kammscher Circle During Cornering with Constant Load: open Differential 9

Kammscher Circle During Cornering with Constant Load: AYC System 10

Options to Generate a Yaw Moment on Vehicle's Cog 11

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 intervention Not 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 12

SCHNELLSTER and TWINSTER + Influence on Yaw Behavior by Different Solutions SCHNELLSTER TWINSTER + Yaw Moment by AYC Yaw Moment by AYC Rotational speed Wheel Force 13

SCHNELLSTER Superimposed Planetary Gear System Speed Lead 14

SCHNELLSTER System description Mechanical Part / Torque Flow C1 C2 3 Step Planetary Gear Planetary Carrier with integrated Coupling Function Input from diff. Carrier 15

SCHNELLSTER System description Hydraulic Part X X One Actuator Pressure Controlled 4-port/2-way valve No Accumulator No Pressure limitation valve High Dynamic High efficiency P U )( )( )( )( P U X HCA 16

SCHNELLSTER Current Lay Out for MINI R53 Planetary gear offset: 10% Max. delta Torque: 1400 Nm Weight: 15 kg Drag Torque: < 2Nm Hydraulic Pressure Range: 0 45 bar Response times: < 100 ms 17

GETRAG TWINSTER + TWIN Clutch System Torque lead 18

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 19

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 20

TWINSTER + System description Mechanic Part / Torque Flow Coupling left Coupling right Sideshaft left Sideshaft right No Differential 21

TWINSTER + System description Hydraulic Part X X Twin Coupling System Valve controlled Pressure demand dependent control One actuator No accumulator No pressure limitation valve High dynamic High efficiency HCA 22

TWINSTER + Pressure Demand versus Vehicle Speed Current Lay Out for MINI Vehicle Speed km/h Engine Torque Pressure Gear box clutch Pressure TWINSTER + Engine Torque Nm Pressure bar Less Efficient Efficient 33% of RLD 66% of RLD 23

TWINSTER + Current Lay Out for MINI R53 Skid Torque for each Coupling: Weight incl. HCA: Drag Torque: Hydraulic Pressure Range: Response time: 1800 Nm 18 kg < 2 Nm 0 45 bar < 100 ms 24

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) Function Active 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 25

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 26

TWINSTER + Weight compensation potential by integration into man. transmission Weihgt reduction: Differential Transm. Clutch Actuation -9.0 kg With integration: HCA: 2 kg TWINSTER +: 8 kg overall: 10 kg + 1.0 kg 27

Vehicle Test Results µ-low 28

Self-steering behavior, packed Snow, Circle dia= 230m Open, SCHNELLSTER, TWINSTER + Steering Angle 110 105 100 95 90 85 80 75 OPEN SCHNELLSTER 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Lateral Acceleration m/s 2 TWINSTER + 29

WOT from Steady State Cornering, packed Snow, Circle dia= 230m Open, SCHNELLSTER, TWINSTER + 10^-3 rad/s 140 130 Self-steering behavior Neutral 120 110 Yawspeed 100 90 80 70 60 50 TWINSTER + SCHNELLSTER 40 30 20 OPEN 10 0.5 1.0 1.5 2.0 2.5 s Understeering 30

WOT Acceleration on split-µ TWINSTER + Steering angle demand for yaw compensation km/h wheelspeed 150 100 bar coupling pressure 50 0 10 5 select low pressure steering angle 0 15 10 5 throttlepos max. steering angle 8 100 % Throttle pos 50 kn 0 10 24 26 28 30 32 0 s 31

Vehicle Test Results µ-high 32

Self-steering behavior µ-high, dry asphalt, circle r=80 m Open, SCHNELLSTER, TWINSTER + Steering Angle 125 120 115 110 105 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 OPEN SCHNELLSTER TWINSTER + 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 33

Position Plot, Steer Step Input in WOT, 50 km/h, dry Asphalt, 2. Gear, Open, SCHNELLSTER, TWINSTER + sm 0-5 -10-15 -20-25 -30-35 -40 TWINSTER + -45-50 -55 SCHNELLSTER -60-65 -70-75 OPEN -70-60 -50-40 -30-20 -10 0 sm 34

Vehicle Test Results Road Load Data Acquisition TWINSTER + Thermal Capacity 35

TWINSTER + Road Load Data Acquisition: Nürburgring North loop (Race style) m/s2 15 5-5 -15 500 Average Pressure: Average Delte Speed: Average Coupling Torque: Average Vehicle Speed: 10.3 bar 5.5 1/min 420 Nm 126 km/h kmh C 0 300 200 100 0 125.0 Average Power Losses: 241 W Max. Oilsumptemperature: 109 C Energy per km: 4.9 kj/km 62.5 0.0 3.8 3.9 4.0 4.1 4.2 4.3 10^3 s 36

TWINSTER + Public Roads Country (normal style) 120 km Distance m/s2 20 0 kmh C -20 500 0 200 100 0 90 80 Average Pressure: Average Delta Speed: Average Coupling Torque: Average Vehicle Speed: 6.7 bar 2.1 1/min 130 Nm 57 km/h Average Power Losses: 35 W Max. Oilsumptemperature: 73 C Energy per km: 2.2 kj/km 70 60 0 1 2 3 4 5 6 7 10^3 s 37

TWINSTER + Nürburgring North loop (race style) Pressure Distribution left Coupling versus Vehicle Speed Frequency % Pressure bar 38

TWINSTER + Public Roads Country (normal style) Pressure Distribution left Coupling versus Vehicle Speed Frequency % Pressure bar 39

Summary 40

TWINSTER + improvement with Utilization of Potentials Comparison to FWD open Differential and other Driveline Systems 60 52 Improvement by utilization of additional potentials Improvement % 50 40 30 20 10 12 40 16 43 0 elsd TWINSTER ++ + SCHNELLSTER AWD Hang on AWDTWINSTER 41

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 driver Unique selling point for the OEM to differentiate from other competitors By utilization of all potentials of the TWINSTER + the system can become the future differential in FWD 42

Thank you for your attention! 43