November 16, 2015 EVE 5110

Plug-In Hybrid Electric Vehicle

Siddhesh OzarkarMS Mechanical Engineering

Wayne State University, Detroit

Abstract

Energy requirement of a vehicle is a crucial step prior to design of the powertrain. An estimate of the required power is done by simulating the performance of the glider vehicle to complete specific drive cycles. These are also referred as the various energy requirements at the wheels.

During new powertrain designing process commercially available computer programs can be utilized for the simulation of the drive cycles.

This report focuses on the energy requirement of the glider vehicle subjected to the following mentioned drive cycles, UDDS, HwFET & US06.

Introduction

Powertrain design is an important step in overall vehicle development process. This report discusses important vehicle parameters derived for a glider vehicle. These parameters then can be used for benchmarking during the powertrain design process.

The parameters are required to perform the sizing and selection of energy source (Internal Combustion Engine, Electric Drive, and Hybrid Power Vehicle).

Powertrain the parameters are required to perform the sizing and selection of energy source (Internal Combustion Engine, Electric Drive, and Hybrid Power Vehicle).

In this report basic vehicle dynamics and physics is considered to calculate energy requirements of a glider vehicle. Cases of constant linear accelerations & constant velocities are considered to calculate average power required at the wheels on a level surface and on graded slopes.

Definitions

The energy requirements of the vehicle are strongly dependent on the drive cycles for which it is being tested for. The Drive cycles used in the simulations are as follows;

1. Urban Dynamometer Driving Schedule (UDDS)2. Highway Fuel Economy Driving Schedule

(HwFET)3. Supplemental FTP Driving Schedule (US06)

These driving schedules are graphically establishes in upcoming figures.

The UDDS is given in figure 1

It shows how velocity changes with a time step of 1 second.

Figure1

UDDS

The HwFET schedule is given in figure 2

The variation of velocity is plotted against time.

HwFET

The US06 schedule is given in figure 3

Variation of velocity is plotted with respect to time.

Figure3

US06

Glider Vehicle Parameters

GVWR 2000kgCoefficient of Rolling

Resistance (fr)0.009

Drag* Area 0.75m2

ρ 1.2kg/m3

The following parameters for the glider vehicle have been provided. Table1.

These parameters are further used to formulate the vehicle dynamics equation.

Table1

Forming of Vehicle dynamics Equation

The energy requirement of the vehicle depends on the road load.

The road load equation is given

Ftr=(m*g*fr)+(1/2*ρ *Cd*Af*v2)+Finertia

--------- Equation 1

Where,

Ftr = Tractive Effort (N)

m = GVWR (kg)

ρ = Air Density (kg/m3)

Af = Frontal Area of Vehicle (m2)

Finertia = Inertia force (N) = m dv /dt (N)

V = Velocity (m/s)

Grade = 0%.

Equation 1 has been established from simple laws of physics. The various load forces acting on the vehicle are illustrated in figure 4.

A similar Engine of given characteristics can be found in the 2010 Toyota Prius.

A 2010 model of Prius has the same engine configuration and has been considered for this report.

The Transmission configuration has been formulated by using the tire radius, accessories load etc. from the vehicle technical data provided for Prius.

A generic 100 kW (~1.8 L) gasoline engine ‐ ‐has the power and efficiency characteristics shown & create an ICE powertrain MATLAB ‐mode

N=6000 rpm

T= 160Nm

P= 100kW

η =35%

Toyota Prius Technical Specifications:

1,798 cc 1.8 liters

In-line 4 front engine

B*S 80.5 mm * 88.4 mm

Power: 100 kW

Tire Diameter = 0.2159m

.

Toyota Prius Technical Specifications:

1,798 cc 1.8 liters

In-line 4 front engine

B*S = 80.5 mm * 88.4 mm

Power: 100 kW

Tire Diameter = 0.2159m

The following graph shows the normalized values of Torque and Engine Speed.

To determine Peak torque we can assume the rough ratio between peak torque and Torque@ maximum power as 0.85.

( 160Tpeak )=0.85

Tpeak = 190 Nm.

Maximum Speed:

Pmax=( 12 )∗ρ∗ACd .vmax3+m∗g∗Fr . vma x2

Therefore the Maximum velocity that can be achieved using this Engine @ 100 Kw Power is 61.21m/s = 219 Kmph.

Acceleration:

To travel 0 to 60mph the vehicle with test mas s of 1500 kg.

Using the Basic Vehicle dynamics Equation and integrating for t.

ηmax∗(Gr )∗Tmax=Fr∗m∗g+(1

2 )∗ρCd . A .V 2+m( dVdT

)

T=12.7 seconds

Gear Ratio Calculation:

Gear Ratio γ4

γ 4= r∗cm∗π(vmax∗S )

Cm = Mean engine Speed

S = Stroke = 88mm

R= radius of tire =0.2159m

γ 4 = 2.17

Test Mass(kg) 1500Max. Speed(kmph) 220

Acceleration 0 to 60 mph (s) 12.7Powertrain configuration Series HybridEngine peak power, kW 100kW @6000rpmEngine peak torque, Nm 190Nm (Graph)

Transmission, gearing Single speed gearboxMotor Peak Power kW 51.8

Battery energy Capacity kWh 3Battery peak power, kW 50

Battery mass, kgBattery Energy Capacity (code) 2.5 kWh

Motor Mass kg 91

Maximum Speed:

Pmax=( 12 )∗ρ∗ACd .vmax3+m∗g∗Fr . vma x2

Therefore the Maximum velocity that can be achieved using this Engine @ 100 Kw Power is 61.21m/s = 219 Kmph.

Acceleration:

To travel 0 to 60mph the vehicle with test mas s of 1500 kg.

Using the Basic Vehicle dynamics Equation and integrating for t.

ηmax∗(Gr )∗Tmax=Fr∗m∗g+(1

2 )∗ρCd . A .V 2+m( dVdT

)

T=12.7 seconds

Gear Ratio Calculation:

Gear Ratio γ4

γ 4= r∗cm∗π(vmax∗S )

Cm = Mean engine Speed

S = Stroke = 88mm

R= radius of tire =0.2159m

γ 4 = 2.17

For other Gear Ratios using the relation:

γ 4=( 23 )γ 3

γ 3= 3.26

Similarly

γ 2= .4.9

γ 1 =7.3

From the Vehicle Technical data the engine operates at maximum power of 100kW.

The codes can be validated by using a simple relation and comparing the two values:

Pe=z∗( π16 )∗B2∗pme . cm

Z= number of cylinders =4 given from specification

B = Bore (mm) = 80mm

Pme = Piston Mean effective pressure

Cm = Piston mean speed

Pe = 100.35 kW

Thus the relations used in coding are close enough to the realistic values.

Calculation of Energy Consumption:

For the given Cycle (eg UDDS)

Avg. Ftrac= 230N

Avg. velocity for this cycle = 8.87m/s

Avg Tractive Power:

Ptrac= Ptrac∗vavgtrac

Trac = Avg. traction fraction from the entire cycle=0.8 for udds.

Efficiency of engine given is 35%

Calculate Efficiency ηe = 0.409 =40%

Power in Fuel Required

Pf =( trac )∗( Pe (avg )ηe )

For UDDS Pf = 11.14kW

Fuel required Vf:

Vf = PfHl∗ρ

Hl = Lower heating value of fuel

Hl = 43.5J\kg ……. For gasoline

Hl = 30.9 kJ\kg …..For E85

Therefore Range for UDDS

Range = 56.95mpg.

To find CO2 Emissions:

Range in l/100km 2392g/l/100km

For UDDS 3.77l/100km

The corresponding values for the emissions for only 100kW IC engine System.

UDDS HwFET Combined US06

Distance Travelled(km) 11.9902 16.5050 15.20 12.8876

Time(hr.) 0.38 0.212 0.30 0.1667

Net tractive energy (Wh/km)

63.9 102.9 88.6 726

Fuel energy (Wh/km) 352.76(11.14kW) 95.46(7.4326kW) 204.47(10.36kW) 157.31( 12.32kW)

Battery energy (DC Wh/km)

NA NA NA NA

GHG WTW (g CO2 eq/mile)

81.74(131.54 g/mi) 54.49(87.693g/mi) 76.00(122.31 g/mi) 90.34(145.38 g/mi)

Range (mpg) 56.9548 36.9698 52.9579 62.95

Validation of Results

Calculation of Energy Consumption:

For the given Cycle (eg UDDS)

Avg. Ftrac= 230N

Avg. velocity for this cycle = 8.87m/s

Avg Tractive Power:

Ptrac= Ptrac∗vavgtrac

Trac = Avg. traction fraction from the entire cycle=0.8 for udds.

Efficiency of engine given is 35%

Calculate Efficiency ηe = 0.409 =40%

Power in Fuel Required

Pf =( trac )∗( Pe (avg )ηe )

For UDDS Pf = 11.14kW

Fuel required Vf:

Vf = PfHl∗ρ

Hl = Lower heating value of fuel

Hl = 43.5J\kg ……. For gasoline

Hl = 30.9 kJ\kg …..For E85

Therefore Range for UDDS

Range = 56.95mpg.

To find CO2 Emissions:

Range in l/100km 2392g/l/100km

For UDDS 3.77l/100km

The emission values obtained from the coding and calculations are compared with the ones given by EPA Test Car List data

Toyota Prius Emission Values

For given IC engine Powertrain

Criteria Satisfaction & Performance Targets. For 100KW IC Engine Vehicle

Performance/Utility Category Vehicle Modeling Design Targets*

Achieved Targets

Energy consumption (unadjusted energy use on

combined Federal Test Procedure [FTP] city and

highway cycles)

Better than 370 Wh/km (600 Wh/mi) combined city and

highway (55%/45%, respectively)

Energy Consumption Better than 370Wh/km

GHG emissions (WTW combined city and highway

cycles)

Less than 120 g of carbon dioxide equivalent (CO2

eq)/km (200 g CO2 eq/mi)

Yes, all emissions well below the limit ( refer above figure for comparison with values

calculated)Range Greater than 320 km (200 mi)

combined city and highwayYes Range achieved in all

cases is greater than 320 km.Maximum speed Greater than 135 kph (85

mph)Yes maximum Speed is greater than 135 km/h

Acceleration time of 0 to 97 kph (0 to 60 mph)

Less than 11 seconds 12.7

Highway grade ability (at gross vehicle weight rating

[GVWR])

Greater than 3.5% grade at a constant 97 kph (60 mph) for

20 minutes

Yes Grad ability greater than 3.5%

Part B: Downsizing of Engine:

Engine Downsizing is the way to make small engines perform high.

Plug In Series Hybrid Mode of Operation:

SOC balanced fuel consumption‐

The Series Hybrid is designed with energy management strategy to keep the battery state of charge (SOC) within reasonable bounds.

Power Demand

Motor Power

Test Mass =2000 kgEngine Power 150kW

UDDS

Distance Travelled(km) 11.9902

Time(hr.) 0.38

Net tractive energy (Wh/km) 66.4

Fuel energy (Wh/km) NA

Battery energy (DC Wh/km) 3

GHG WTW (g CO2 eq/mile) 83.1(131.54 g/mi)

Instantaneous Power & Avg. Power with Full & zero Regenerative Braking

References

SOC balanced fuel consumption‐

The Series Hybrid is designed with energy management strategy to keep the battery state of charge (SOC) within reasonable bounds.

Traction Required

?

Engine Power

Y

N

PT<PE

SOC<SOCT

YSOC of

PPS

N

N

Pbrk>Pm?

Y

Hybrid Braking

Hybrid Traction

Engine+PPS

PPS Charging

Y

Engine Traction only

SOC Control logic Flow Chart

The power rating of the engine/generator is designed to be capable of supporting the vehicle at a regular highway speed (100 km/h or 60 mph) on a flat road is 43 kW, in which energy losses in transmission (90% of efficiency), motor drive (85% of efficiency) are involved.

Avg. Power in UDDS =Pavg. =6.95 kW (calculation showed only for UDDS)Compared with the power needed in Figure 7, the average power in these drive cycles is smaller. Hence, 43 kW of engine power can meet the power requirement in these drive cycles.

Average Power with Zero Regenerative Braking.

The power rating of the engine/generator is designed to be capable of supporting the vehicle at a regular highway speed (100 km/h or 60 mph) on a flat road is 43 kW, in which energy losses in transmission (90% of efficiency), motor drive (85% of efficiency) are involved.

Avg. Power in UDDS =Pavg. =6.95 kW (calculation showed only for UDDS)Compared with the power needed in Figure 7, the average power in these drive cycles is smaller. Hence, 43 kW of engine power can meet the power requirement in these drive cycles.

Figure 6

Figure 7

Design of Power capacity of PPS

Ppps=( Pmotorηm )−Pengine

Pengine =43.5kWPmotor= 51.8 kW

Required Power capacity of PPS Ppps= 47.2941kW

Given Peak Power of Ppps = 50kW

Total Energy Capacity of Battery 2.5kWh

SOC limits

SOC top limit =0.6SOC bottom Limit = 0.4

Gear Ratio design based on Motor speed

ig= π .Nm. r(30. Vmax )

ig=2.17 Series PHEV by sizing the battery and engine using ADVISOR Component Sizing and Mass for above cycles

With Toyota Prius Values as Reference

Total Mass of Vehicle = 1471 kg

Test Conditions for UDDS ValuesInitial SOC 0.6Vehicle mass kg 1368Grade % 6Minimum SOC 0.4

Test Results ValuesGradability @ 90kmph 0.8%Vehicle mass kg 16170-90 kmph 29s

SOC Variation Graph from Advisor* UDDS Cycle

Component Power kW Mass (kg)

Engine 43kW @ peak η =0.39

137

Motor 31 kW & η=0.91 57

Generator 15 kW 34

Transmission NA 50

Energy StorageRint Model

ESS PB25 275

Vehicle Mass NA 918

HwFET Cycle

USo6 Cycle

In USO6 cycle it can be seen that using PPS is not favorable as SOC drops to 0 during operation at long distances.

At this time The Engine is required to bring back the SOC within the reasonable bounds. Series Combination Seems to be underperforming for cycle requirement.

Final values of Emissions and Vehicle performance during various cycles

Torque Speed Variation using Advisor

Down Sized Engine & Other Components used for Simulation:

Component Production Model Mass (kg)Engine Toyota Prius 43kW 137Motor MC AC 75 91

PPs NImh40Module with V_nominal

308

40

Total Vehicle Mass = 1471kg

Battery Modelling:

Modelling of a battery using PNGV Model

Test Mass= 1500+117 kgEngine 43 kW +Motor

31kW

UDDS HwFET US06

Distance Travelled(km) 11.9902 16.5050 12.8876

Time(hr.) 0.38 0.212 0.1667

Max Speed km/h 91.25 96.4 129.23

Max Acc’n m/s 1.48 1.43 3.76

Net tractive energy (Wh/km)

63.9 102.9 726

Fuel Consumption (l/100km)

4.9 3.6 6.91

GHG WTW (g CO2 eq/mile)

139.54 g/mi 117.693g/mi 198.3 g/mi

Range (mpg) 46.9 58.7 33.60

OCV Open Circuit VoltageRo Battery Internal ResistanceRp Polarization ResistanceC Shunt CapacitanceT Polarization time Constant T=RpCV1 Battery Terminal voltage

Battery Paramenter

Simulation of Batteries using Given Program & ADVISOR Results for Battery Simulation:

Parameter A123` ESS NiMH6Module 7 1

Nom. Voltage 3.3V 8V

ResultsMinimum Voltage 262.5V 255VMaximum Voltage 378V 361V

Mass 212kg 30.2

References:

Modern Electric, Hybrid Electric, and Fuel Cell Vehicles. Mehrdad Ehsani, Texas A&M University, Yimin Gao, Texas A&M University, Sebastien E. Gay, Texas A&M University, Ali Emadi, Illinois Institute of Technology

Modeling and Simulation of Electric and Hybrid Vehicles By David Wenzhong Gao, Senior Member IEEE, Chris Mi, Senior Member IEEE and Ali Emadi, Senior Member IEEE

Energy Management Power Converters in Hybrid Electric and Fuel Cell Vehicles By Jih-Sheng (Jason) Lai, Fellow IEEE, and Douglas J. Nelson.