tradeoff between powertrain complexity and fuel efficiency - presentations/hevs and...

Namdoo Kim, Jason C. Kwon, and Aymeric RousseauArgonne National Laboratory, USA

Nov, 2010

Tradeoff Between Powertrain Complexity and Fuel Efficiency

Introduction

2

Argonne National Laboratory - Tradeoff Between Power-train Complexity and Fuel Efficiency

Toyota Prius, and some other hybrids, use a “Power Split” system:

- Engine speed can be controlled independently from the vehicle speed

- Relatively low efficiency in the high-speed region

Combining several EVT modes in to one “Multi-mode” hybrid system, thereby increasing the number of MPs and allowing greater operation flexibility

Dozen of patents on multi-mode EVT design configuration

EVT efficiency of electro-mechanical power path increases with powertrain(PT) configuration complexity

EVT mechanical losses also increase with PT complexity

The objective is to evaluate the benefits of several multi-mode powertrain configurations from a fuel consumption and cost point of view.

MP = Mechanical point

What is an EVT ?

3


Electrically Variable Transmission

Continuously variable, using gearing and electric motors

Used with a battery pack in hybrid electric vehicles.

Examples:

– Single mode w/o FG : Toyota Prius04

– Single mode w/ FG : Prius10, LS600, HS 250h, Ford Escape,…

– Two mode w/o FG : Allison EP40 and EP50 bus hybrid

– Two mode w/ FGs : Saturn Vue HEV, GM Tahoe HEV

– Three&Four mode w/ FGs : Being developed by OEM

Gear Gear

BatteryEngine Wheel

Electro-Mechanical

MC2 MC1

All-Mechanical

FG = Fixed Gear

0 0.5 1 1.5 2 2.5 3-1.5

-1

-0.5

0

0.5

1

Pow

er R

atio

The ratio P-elect to P-eng (@ W-eng=1500rpm, T-eng=100Nm)

EVT1

“All-Mechanical” Power

“All-Input” Power

“Electro-Mechanical” Power“Mechanicla Point”

Ratio : 0.7054

0 1 2 3 4-1.5

-1

-0.5

0

0.5

1

1.5

Pow

er R

atio


EVT1EVT2

MP1MP2

0 1 2 3 4-1.5

-1

-0.5

0

0.5

1

1.5

Pow

er R

atio


EVT1EVT2

MP1MP2 FG1FG2

FG3

FG4

0 1 2 3 4-1.5

-1

-0.5

0

0.5

1

1.5

Pow

er R

atio


EVT1EVT2EVT3

MP2MP3FG2FG3

MP1FG1

Technical AccomplishmentsUnderstand Efficiency Potential of Each Multi-Mode

4

Note : Power ratio = electro-mechanical power / all-input power Minimize the power ratio, which is more efficient and transmit more power mechanically

Single Mode Two Mode(1)

AHS2 FWD

Three Mode

small values mean little recirculation, higher efficiencies

Technical AccomplishmentsUnderstand Efficiency Potential of Each Multi-Mode

5


AHS2 FWD Three Mode

Note : The efficiency of the multi-mode system has relatively high value Additional mode can allow to maintain high efficiency over a wider range

0 0.5 1 1.5 2 2.5 30.5

0.6

0.7

0.8

0.9

1

Eff.

Efficiency (@ W-eng=1500rpm, T-eng=100Nm)

EVT1MP

0 1 2 3 40.4

0.5

0.6

0.7

0.8

0.9

1

Eff.


EVT1EVT2

0 1 2 3 40.4

0.5

0.6

0.7

0.8

0.9

1

SR, the ratio of W-eng to W-out

Eff.


EVT1EVT2

0 1 2 3 40.4

0.6

0.8

1


Eff.


EVT1EVT2EVT3


AHS2 FWD Three Mode

EGMC2

MC OUT

S1 C1 R1

R2 C2 R2

EGMC2

MC

OUT

CL2

CL1S1

CL4

CL3

C1 R1

R2 C2S2

S3

R3C3

Seven Configurations are Considered

6

AHS2 FWD (Two mode w/ FGs)

EGMC2

MCOUTCL1

CL2

CL3EGMC2

MCOUTCB12R

C234

CB4

C13

Two Mode w/o FGSingle Mode

P7,220,203 : 2 Electric Motors 2 Planetary Gear Sets (SPPG, DPPG) 4 Wet-Plate Clutches

P6,478,705 : 2 Electric Motors 2 Planetary Gear Sets (only SPPG) 2 Wet-Plate Clutches

AHS2 RWD (Two mode w/ FGs) Three & Four Mode w/ FGs

P6,953,409 : 2 Electric Motors 3 Planetary Gear Sets (only SPPG) 4 Wet-Plate Clutches

P7,645,206 : 2 Electric Motors 3 Planetary Gear Sets (SPPG, DPPG) 5 Wet-Plate Clutches

PRIUS : 2 Electric Motors 1 Planetary Gear Set (SPPG) no Wet-Plate Clutches

EGMC2 MC

OUT

78 30

S C R

EGMC2

MCOUTCL2

CL1S1 C1 R1

R2 C2 S2

AHS = Advanced Hybrid System (GM 2 Mode)

Single Mode w/ RG

ESCAPE : 2 Electric Motors 2 Planetary Gear Set (SPPG) no Wet-Plate Clutches


Modeled Different Transmissions

7

Gear System

::

Note : Transmission models developed in SimDriveline to allow for modeling of detailed losses (Transmission spin loss, Hydraulic oil loss). Low level control developed for each transmission

Local control

Plant


Using Argonne Powertrain System Analysis Toolkit : - forward-looking powertrain simulation environment- dynamic plant models- Matlab/Simulink/Stateflow Based

Multi Mode Leads to Smaller Component Sizes

8

Single Mode

Single Mode w/ RD

Two Modew/o FGs AHS FWD AHS RWD Three Mode Four Mode

Engine 131.5 kW 131.1 kW 125.3 kW 124.8 kW 125.3 kW 123.3 kW 123.3 kW

Motor 2 (F) 91.7 kW 80.9 kW 62.6 kW 58.1 kW 62.6 kW 61.6 kW 61.6 kW

Motor 1 (R) 91.2 kW 88.2 kW 52.4 kW 47.2 kW 52.2 kW 32.6 kW 32.6 kW

Battery NIMH, 173 cells, 1.2 volt/cell, 6

Ah

NIMH, 180 cells, 1.2 volt/cell, 6

Ah


Ah


Ah


Ah


Ah


Ah

PC Converter Efficiency 95 % 95 % 95 % 95 % 95 % 95 % 95 %

Electrical Accessory 200 W 200 W 200 W 200 W 200 W 200 W 200 W

PGs Ratio (Zr/Zs) 2.6 2.4, 2.0 1.5, 1.5 2.36, 2.24 1.93, 1.97, 2.69

2.0, 2.0, 2.3 -

Final Drive 4.11 4.11 3.02 3.02 3.02 3.02 3.02

Wheel Radius 0.3423 m 0.3423 m 0.3423 m 0.3423 m 0.3423 m 0.3423 m 0.3423 m

Drag Coefficient 0.37 0.37 0.37 0.37 0.37 0.37 0.37

Vehicle Mass 1953 kg 1940 kg 1883 kg 1875 kg 1883 kg 1857 kg 1857 kg

Note : Baseline Vehicle Specifications : Small-size 2WD SUV Sizing results from grade(13% @ 65mph) and acceleration constraint (7.8 sec) Multi-Mode mode allows smaller electric machines

'Single' 'Single w/ RG''Two w/o FG' 'AHS2 FWD' 'AHS2 RWD' 'Three' 'Four'0

20

40

60

80

100

120

140Component Sizing

Pow

er, k

W

Mode

EngineMotor(2)Motor(1)

88.2%96.7%

95.3%100%

100%

100%

94.9% 95.3% 93.8% 93.8%99.7%

68.3%

57.5%63.4%

51.8%

68.3%

57.2%

67.2%

35.7%

67.2%

35.7%

Vehicle Level Controls All Developed Using the Same Control Philosophy

9

Controller objective: Find the power split between mechanical components (ICE, MC2, MC1) that meets the driver request for the current speed of the vehicle, while maintaining acceptable battery SOC and minimal fuel consumption

Controller has to decide on engine ON/OFF, mode and 2 other degrees of freedom

The SOC correction and engine ON/OFF conditions are properly defined.

Mode selection rule is defined by maps which are computed in an offline optimization code to find the optimal engine speed and torque.

Note: Basic control concepts/constraints provided by the validation works

0 20 40 60 80 100 120 140 1600

200

400

600

800

1000

1200

1400Mode Shift Map

Vehicle Speed, mph

GB

Tor

que

Out

, Nm

EVT1EVT2EVT3FG1FG2FG3

(a)

0 20 40 60 80 100 120 140 1600

100

200

300

400

500Mode Shift Map

Vehicle Speed, mph

Eng

Spee

d O

ut, r

ad/s

ec

EVT1EVT2EVT3FG1FG2FG3

FG3

FG2FG1

(b)

Convert into the map using vehicle and engine speeds indexes

Fuel Economy Summary

10

AHS2 FWD system provides the highest fuel economy for the vehicle application considered on the small-size SUV specification.

UDDS HWFET NEDC LA92 US0620

25

30

35

40

45

50Fuel Economy Summary

Fuel

Eco

nom

y, m

pg

Single ModeSingle Mode w/ RGTwo Mode(1) w/o FGAHS2 FWDAHS2 RWDThree ModeFour Mode

15 20 25 30 35 40 45 5032

34

36

38

40

42

44

46

48

50

Average Speed, mile/h

Fuel

Eco

nom

y, m

pg

Cycle Statistics vs. FE


0.2 0.3 0.4 0.5 0.6 0.725

30

35

40

45

50

Average Acceleration, m/s2

Fuel

Eco

nom

y, m

pg

Cycle Statistics vs. FE


Component Average Efficiency (%) Single mode has the highest transmission efficiency

11

HWFET Single Mode

SM w/ RG

Two Mode (1)

AHS 2FWD

AHS2 RWD

Three Mode

Four Mode

Engine average Bidirectional efficiency 33.77 33.71 33.53 31.61 30.55 30.70 30.60

Motor #1 average Bidirectional efficiency 91.40 89.94 86.09 86.58 87.15 87.01 87.03


Transmission average Bidirectional efficiency 93.84 93.42 88.85 89.04 88.89 90.21 90.25

Powertrain Efficiency - Bidirectional 25.94 26.00 26.94 26.73 25.83 26.51 26.47

UDDS Single Mode

SM w/ RG

Two Mode (1)

AHS2 FWD

AHS2 RWD

Three Mode

Four Mode

Engine average Bidirectional efficiency, 33.32 33.37 33.05 30.89 31.09 31.94 32.02



Transmission average Bidirectional efficiency 96.12 96.39 92.85 90.48 89.54 89.11 88.70

Powertrain Efficiency - Bidirectional 33.46 33.61 33..20 31.62 30.89 30.61 30.09

Note : Transmission eff. refers only to mechanicals including final reduction gearset eff.

Single Mode

Single Mode w/ RG

Two Mode (1)

AHS2 FWD

AHS2 RWD

Three Mode

Four Mode

Single Mode

Single Mode w/ RG

Two Mode (1)

AHS2 FWD

AHS2 RWD

Three Mode

Four Mode

The energy loss results of the transmission under UDDS and HWFET


Impact of Powertrain on Operation

12

0 10 20 30 40 50 600

50

100

150

200

Vehicle Speed, mph

Engi

ne S

peed

, rad

/s

UDDS - Operating points (HEV and propelling)

M.P.

0 10 20 30 40 50 600

50

100

150

200

250

Vehicle Speed, mph

Engi

ne S

peed

, rad

/s


M.P.1M.P.2FG1FG2FG3FG4EVT1EVT2FG2FG3FG4

0 10 20 30 40 50 600

50

100

150

200

250

Vehicle Speed, mph

Engi

ne S

peed

, rad

/s


M.P.1M.P.2M.P.3FG1FG2FG3EVT1EVT2EVT3FG2FG3Mechanical Points Line

(SR=0.7222)

FG2 (MP1)

FG3

FG4(MP2)

FG1 FG1(MP1)

FG3(MP3)

FG2(MP2)

AHS2 FWD

Single-mode

Three-mode

0 10 20 30 40 50 600

50

100

150

Vehicle Speed, mph

Engi

ne S

peed

, rad

/s

HWFET - Operating points (HEV and propelling)

M.P.

0 10 20 30 40 50 600

50

100

150

200

Vehicle Speed, mph

Engi

ne S

peed

, rad

/s


M.P.1M.P.2FG1FG2FG3FG4EVT1EVT2FG3FG4

0 10 20 30 40 50 600

50

100

150

200

Vehicle Speed, mphEn

gine

Spe

ed, r

ad/s


M.P.1M.P.2M.P.3FG1FG2FG3EVT1EVT2EVT3FG2FG3

FG2 (MP1)

FG3

FG4(MP2)

MPFG3

(MP3)

FG2(MP2)

AHS2 FWDSingle-mode Three-mode

UDDS :

HWFET :

0 0.5 1 1.5 2 2.5-2

-1.5

-1

-0.5

0

0.5

1

1.5


Pw

r R

atio

The ratio P-elect to P-eng, Single Mode EVTConstant Engine Torque and Engine Speed (@ W-eng=1500rpm, T-eng=120Nm)

EVT1

0 0.5 1 1.5 2 2.5

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1


Eff

.

Efficiency

EVT1

“Electro-Mechanical” Power

“All-Mechanical” Power

“Mechanical Point”ratio :0.72

“All-Input” Power

Single Mode Single Mode

Single mode system has relatively lower system efficiency in primary operating region As transmission reaches higher overdrive, electro-mechanical power increases sharply.

Conclusion

13


The fuel efficiency potential of several multimode systems (1 to 4 modes) has been defined.

Detailed transmission models, including spin losses and hydraulic oil losses have been developed along with their low level controllers.

Vehicle level control strategies have been defined for several multi-mode systems.

For the small SUV application considered, the results show impact on component sizing and component operating conditions.

Multi-mode system has more fuel economy advantage during high speed cycle. When the cycle is more aggressive, multi-mode with FG has advantage.

Future work will focus on:

- Additional vehicle classes (e.g., compact, midsize car, midsize SUV…)

- Take into account additional Vehicle Technical Specifications (i.e., towing, passing…)

- Other configurations options (e.g., for series, compare series vs. GM Volt…)

Tradeoff Between Powertrain Complexity and Fuel Efficiency

Contact / Website

Namdoo Kim, [email protected]

Aymeric Rousseau, [email protected]

http://www.autonomie.net/

Argonne National Laboratory, 9700 South Cass, Argonne IL 60439, USA

Acknowledgements

Activity sponsored by Lee Slezak from the U.S. Department of Energy

mailto:[email protected]�

http://www.autonomie.net/�

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