Comparison of VECTO and GEM - theicct.org · Comparison of VECTO and GEM Dr. Felipe Rodríguez 22ndJanuary 2018 G20 Transport Task Group: Deep Dive to Support Heavy-Duty Vehicle Efficiency

Comparison of VECTO and GEM

Dr. Felipe Rodríguez22nd January 2018

G20 Transport Task Group:Deep Dive to Support Heavy-Duty Vehicle Efficiency Labeling and Standards Meeting #2

2

”Heavy-duty vehicle fuel-efficiency simulation: A comparison of US and EU tools” (2015)

Franco, V., Delgado, O., & Muncrief, R. (2015). Heavy-duty vehicle fuel-efficiency simulation: A comparison of US and EU tools. ICCT. http://www.theicct.org/heavy-duty-vehicle-fuel-efficiency-simulation-comparison-us-and-eu-tools

§ ICCT conducted a comparison of GEM 2.0 (Phase 1) and VECTO (2.0.3) in 2015

§ Since then both tools have been updated to GEM 3.0 (Phase 2) and VECTO (3.2.1), resulting in changes to the required model inputs and the resulting fuel consumption simulation.

§ Nevertheless, ICCT’s 2015 report is a good reference document for understanding:§ Forward vs. backward models§ VECTO’s shifting strategy§ VECTO’s look ahead coasting§ VECTO’s file structure

www.theicct.org

APRIL 2015WHITE PAPER

[email protected]

B E R L I N | B R U SS E L S | SA N F R A N C I S CO | WAS H I N GTO N

HEAVY-DUTY VEHICLE FUEL-EFFICIENCY SIMULATION: A COMPARISON OF US AND EU TOOLS

Vicente Franco, Oscar Delgado and Rachel Muncrief

3

”The Present of EU’s Vehicle Energy Consumption Calculation Tool (VECTO), and Recommendations for the Future” (2018)

Rodríguez, F. (2018). The Present of EU’s Vehicle Energy Consumption Calculation Tool (VECTO), and Recommendations for the Future (Publication pending). International Council on Clean Transportation.

§ A new comparison study of the latest releases of GEM and VECTO

§ Although focused on VECTO, it describes the model architectures of both GEM and VECTO

§ The results of this new study are the focus of this presentation

§ Publication expected in February 2018

4

Input comparison between GEM and VECTO

Component VECTO input GEM input

Engine

Displacement, idle speed, fuel consumption map, full load torque curve, motoring friction curve, brake-specific fuel consumption over the Worldwide Harmonized Transient Cycle (WHTC)

Displacement, idle speed, fuel consumption map, full load torque curve, motoring friction curve, fuel consumption over the ARB Transient Drive Cycle for 9 different vehicle configurations

TransmissionTransmission type, gear ratios, torque loss map as a function of torque and speed for each gear, maximum torque and speed per gear

Transmission type, gear ratios, and maximum torque per gear. Optional: Power loss map as a function of torque and speed for each gear

Axle Axle ratio and torque loss map as a function of torque and speed

Axle ratioOptional: Power loss map as a function of torque and speed

Aerodynamic drag

Air drag area as determined during the constant speed procedure. For rigid trucks, a standard box is used. For tractors, a standard trailer is used.

Air drag area as determined by the coastdown methodology. Standard trailers are used for tractor modeling.

Tires Tire dimensions, rolling resistance coefficient (Crr), and load applied during the rolling resistance test for each axle

Rolling resistance coefficient (Crr) for each axle, and drive tire revolutions per mile

Vehicle Curb vehicle weight, gross vehicle weight rating, and axle configuration

Vehicle weight reduction (sum of standardized weight reductions per component), vehicle regulatory subcategory (e.g., Class 8, sleeper cabin, high roof), and axle configuration

Other

Auxiliaries: Technology used for the following auxiliaries: cooling fan, steering system, electric system, pneumatic system, A/C system (whether it is present or not), and power take-off

Off-cycle technologies: Improvements through the application of the following technologies: Speed-limiter, neutral-idle, intelligent controls, accessory load reduction, extended idle reduction, tire pressure system, and other technologies.

5

GEM’s model architecture

Vehiclespeed

Target speed

100

200

300

400500

600700800

9001000

11001200

1300

1400

1500

Input

torq

ue/Nm

0

1x104

2X104

3X104

4x104

5x104

Input speed / 1/min0 500 1000 1500 2000

Torque loss / Nm

Powertrain

Trans.

Driveline

Vehicle

Driver

Drivingcycle

Accelerator pedal position andfeedback from the powertrain

Torqueloss maps

Fuel consumptionmap

Vehicle weightAir drag area

Rolling resistancecoefficients

Road grade andambient temperature

Force atthe wheel

Vehiclespeed

Advance indistance and time

New vehicle positionand speed

30.032.0

38.0

40.0

41.0

44.0

44.044.5

44.8

Torq

ue/Nm

0

500

1000

1500

2000

2500

Engine speed / rpm600 1000 1400 1800 2200

Brake thermal efficiency / %

FRR

Ambient

Engine

§ GEM does not feature a graphical user interface.

§ GEM was developed in Matlab Simulink as a forward-looking model: The simulation runs from the accelerator pedal to the wheels.

§ The GEM architecture is comprised of four main modules: Powertrain, Vehicle, Driver, and Ambient.

§ The Driver module is a closed-loop controller

US and Canada HDV fuel consumption certification

6

Engine dyno mapping

Coastdown test

GEM - Engine cycle generation

GEM

Engine testing:Cycle averaged map

Declared CO2 and FC value

Standard vehicle specifications

Powertrain testing option

Tires test

Transmission and axle test

Wind average correction

Off cycle technologies

Transient correction

Powertrain correction

Input data Dyno testing Correction SimulationOutput data

7

VECTO’s model architecture

30.032.0

38.0

40.0

41.0

44.0

44.044.5

44.8

Torq

ue/Nm

0

500

1000

1500

2000

2500

Engine speed / rpm600 1000 1400 1800 2200

Brake thermal efficiency / %

7700

70

8800

80

9900

90

6600

60

5500

50

4400

30

Inputto

rque/Nm

-6000

-4000

-2000

0

2000

4000

6000

Input speed / 1/min0

i=n Torque loss / Nm

7700

70

8800

80

9900

90

6600

60

5500

50

4400

30

Inputto

rque/Nm

-6000

-4000

-2000

0

2000

4000

6000


i=10 Torque loss / Nm

7700

70

8800

80

9900

90

6600

60

5500

50

4400

30

Inputto

rque/Nm

-6000

-4000

-2000

0

2000

4000

6000



7700

70

8800

80

9900

90

6600

60

5500

50

4400

30

Inputto

rque/Nm

-6000

-4000

-2000

0

2000

4000

6000



100

200

300

400500

600700800

9001000

11001200

1300

1400

1500

Inputto

rque/Nm

0

1x104

2X104

3X104

4x104

5x104

Input speed / 1/min0 500 1000 1500 2000

Torque loss / Nm

Driver

Vehicle

Wheels

Axle

Transmission

EngineAuxiliaries Success?

Shiftingstrategy

Forcerequest

Accelerationrequest

Torquerequest

Torquerequest

Torquerequest

Fuelconsumption

Torque

request

Torque

loss

Torque

loss

Rolling

resistancecoeffi

cients

Vehicle

weig

htAirdrag

area

Driving

cycle

Write simulationresults and advance

to next point

Yes

No

Reduce acceleration requestor operate the brakes

FRR

§ VECTO was developed in C# as a backward-looking model: the simulation flow occurs in the opposite direction to the way it takes place in the actual vehicle.

§ The Driver Model converts the drive cycle information into an acceleration request, to ultimately locate an appropriate operating point in the engine fuel map

§ Once a valid engine operating point is found, the simulation moves to the next point in the driving cycle.

8

Europe HDV fuel consumption certification

Engine dyno mapping

Constant speed air drag test

WHTC test

VECTO

Transient correction

Declared CO2 and FC value

Tires test

Transmission and axle test

Auxiliaries

Cross wind and speed profile

correction

Vertical load correction

Input data Dyno testing Correction SimulationOutput data

9

GEM-VECTO comparison: Definition of base vehicle

Component Parameter 4x2 tractor-trailer 6x2 tractor-trailer

Engine

Displacement 11.0 liters 15.0 liters

Idle speed 650 rpm 600 rpm

Power 262 kW @ 1715 rpm 340 kW @ 1726 rpm

Transient correction None None

Transmission and axleTransmission type 10 speed, AMT 10 speed, AMT

Axle ratio Between 3:1 and 4:1 Between 3:1 and 4:1

Aerodynamic dragCdA Between 4 and 6 m2 Between 4 and 6 m2

Cross-wind correction None None

Tires

Crr steering axle Between 4 and 7 N/kN Between 4 and 7 N/kN

Crr drive/tandem axles Between 4 and 7 N/kN Between 4 and 7 N/kN

Crr trailer axles 6 N/kN 6 N/kN

Tire dynamic radius 512 mm 512 mm

AccessoriesAccessory power 3500 W (constant) 3500 W (constant)

Acc. load reduction None None

Vehicle

Base vehicle mass 9570 kg 14741 kgBase payload 11340 kg 17237 kgVehicle weight reduction Up to 2000 kg Up to 3000 kgTotal number of axles 4 5

10

GEM-VECTO comparison: Powertrains

600

900

1200

1500

1800 210

0240060

0900

1200

1500

1800 210

02400

5 10

1520

25

30

35

40

4550

Torq

ue/Nm

-300

0

300

600

900

1200

1500

1800

Engine speed / rpm

11 L, 262 kW engine.Fuel consumption in kg/h

10

20

30

35

40

45

5060

55

55

5

15

1525

25

Torq

ue/Nm

-500

0

500

1000

1500

2000

2500

Engine speed / rpm

15 L, 340 kW engine.Fuel consumption in kg/h

50

5500

100

110000

150

115500

200

220000Inpu

tto

rque

/10

00

Nm

-6

-4

-2

0

2

4

6

Input speed / rpm

0500

1000 150

02000

2500

3000

Gears 1, 2, 3, 4, and 5Torque loss / Nm

2200

40

4400

60

6600

80

8800

100

110000

120

112200

Inpu

tto

rque

/10

00

Nm

-6

-4

-2

0

2

4

6

Input speed / rpm

0500

1000 150

02000

2500

3000

Gears 6, 7, 8, and 10Torque loss / Nm

2244

21

1188

15

1122

9

Inpu

tto

rque

/10

00

Nm

-6

-4

-2

0

2

4

6

Input speed / rpm

0500

1000 150

02000

2500

3000

Gear 9 (direct drive)Torque loss / Nm

1000

900

800

700

600

500

400

300

100

200Inpu

tto

rque

/10

00

Nm

0

10

20

30

40

50

Input speed / rpm

0500

1000 15

002000

2500

Axle ratio = 4Torque loss / Nm

700

600

500

400

300

100

200

Inpu

tto

rque

/10

00

Nm

0

10

20

30

40

50

Input speed / rpm

0500

1000 15

002000

Axle ratio = 3Torque loss / Nm

Engine: ~ 46% peak efficiency

Axle: ~ 98% mechanical efficiency

Transmission: ~95-99% mech. efficiency

11

GEM-VECTO comparison: Randomized vehicle generation

4.0 4.5 5.0 5.5 6.0

Freq

uenc

y/%

0

5

10

15

20

Axle ratio / -3.0

03.253.503.7

54.0

0

CdA / m2 Crr / N/kN4.0

04.7

55.5

06.2

57.0

0

SteerDrive/Tandem

Weight reduction / kg

0750150

022503000

A total of 500 unique vehicle configurations were randomly generated for each one of the two vehicle types. As an example, the distribution of the values for the 500 different 6x2 tractor-trailers simulated are below

12

The US GHG Phase 2 cycles were used for the comparison

55 mph and 65 mph cycles

Time / s

0100

200

300

400

500

600

700

ARB Transient cycle

Spee

d/km

/h

0

30

60

90

Grade

/%

-7-5-3-11357

Distance / km

0 5 10 15 20

Spee

d/km

/h60

90

120

§ The regulatory cycles for the US GHG Phase 2 standard were used, since they cannot be changed in GEM.

§ The 55 mph and 65 mph cycles are distance-based cycles with grade.

§ The ARB Transient cycle is a time-based cycle without grade

13

Comparison results: Constant speed cycles with grade

22 24 26 28 30 32 34VECTO fuel consumption / gfuel / tonne-km

22

24

26

28

30

32

34

GEM

fuel

cons

umption

/g

fuel/to

nne-

km

6x2, sleeper cab, tractor-trailerGEM = 1.009 * VECTO, R2=0.920

4x2, day cab, tractor-trailerGEM = 1.030 * VECTO, R2=0.964

6 7 8 9 10 11VECTO engine work / kWh

6

7

8

9

10

11

GEM

enginewor

k/kW

h



ARB Transient cycle

55mph and 65 mph cycles with grade

10 12 14 16 18 20 22 24VECTO fuel consumption / gfuel / tonne-km

10

12

14

16

18

20

22

24

GEM

fuel

cons

umption

/g

fuel/to

nne-

km



17 19 21 23 25 27 29 31 33 35VECTO engine work / kWh

17

19

21

23

25

27

29

31

33

35

GEM

enginewor

k/kW

h



§ The engine work is useful to gauge the agreement in energy flows observed by the engine.

§ The fuel consumption is useful to assess the impact of the shifting strategies. For a given engine work, the shifting strategy determines the regions of the engine map.

Absolute error: 0.64%

14

Comparison results: Transient cycle

22 24 26 28 30 32 34VECTO fuel consumption / gfuel / tonne-km

22

24

26

28

30

32

34

GEM

fuel

cons

umption

/g

fuel/to

nne-

km



6 7 8 9 10 11VECTO engine work / kWh

6

7

8

9

10

11

GEM

enginewor

k/kW

h



ARB Transient cycle

55mph and 65 mph cycles with grade

10 12 14 16 18 20 22 24VECTO fuel consumption / gfuel / tonne-km

10

12

14

16

18

20

22

24

GEM

fuel

cons

umption

/g

fuel/to

nne-

km



17 19 21 23 25 27 29 31 33 35VECTO engine work / kWh

17

19

21

23

25

27

29

31

33

35

GEM

enginewor

k/kW

h



§ Despite the differences in model architecture (forward vs backward-looking), driver model, and shifting strategy; both VECTO and GEM produce similar results in terms of engine work and fuel consumption.

Absolute error: 2.03%

15

§ VECTO and GEM show very good agreement when simulated over a large set of identical vehicles

§ The accurate simulation of CO2 emissions of HDVs is more dependent on the component input data than on the selected model (VECTO vs GEM). Harmonization of component certification benefits the implementation of future regulatory measures.

§ Both GEM and VECTO can be adapted to account for the differences across regions. VECTO’s engineering mode provides a user friendly interface to modify drive cycles, payloads, and vehicle details. GEM can also be modified accessing the source code, however, this implies more effort.

Takeaway messages

Documents

Comparison of VECTO and GEM - theicct.org · Comparison of VECTO and GEM Dr. Felipe Rodríguez 22ndJanuary 2018 G20 Transport Task Group: Deep Dive to Support Heavy-Duty Vehicle Efficiency