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January 12, 2005 4’th VI Winter Workshop Series Slide 1
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
John M. Miller, P.E., PhDJ-N-J Miller, P.L.C.
Design Services
January 12, 2005 4’th VI Winter Workshop Series Slide 2
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Outline of TopicsSlide #
3 21 64 75 8593
• Session 1: Historical developments…….• Session 2: Toyota, THS-I and THS-II…..• Session 3: Ford-Volvo-Aisin, FHS………• Session 4: GM-Allison, AHS-2………….• Session 5 Renault, IVT………………….• Conclusion and wrap up………………….
• Presentation time: ½ day
January 12, 2005 4’th VI Winter Workshop Series Slide 3
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: Hydrostatic
• Hydrostatic power split– Maintains direct mechanical power path– Input power splits (k/(k+1)) mechanical + (1/(k+1)) hydraulic– Controllable speed summer (differential) maintains desired
output
ICE Gearbox
VarDispPump
Fixed DispMotor
Hydraulic lines
Geardiff.
Output
Mechanical Power Path
Hydrastatic Power SplitTransmission
January 12, 2005 4’th VI Winter Workshop Series Slide 4
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• The classic electro-mechanical power split transmission developed by TRW and published in a 1971 SAE paper is the basis of today’s electric power split systems. G.H. Gelb, N. A. Richardson, T.C. Wang, B. Berman, “An Electromechanical Transmission for Hybrid Vehicle Powertrains,” SAE paper no. 710235, Jan. 1971
• One electric machine provided the function of “speeder” • A second electric machine provided the function of a
“torquer”• In the original TRW system there are no clutches and no
step ratio gear shifts – the essentials of power split.
January 12, 2005 4’th VI Winter Workshop Series Slide 5
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• TRW Electromechanical Transmission – EMT– ICE drives the planetary SUN gear– The “speeder” (generator) M/G connects to the carrier– The “torquer” (motor) M/G is connected to the ring gear via an
additional gear ratio.– Ring gear output shaft transmits summation power to the vehicle
driveline.
January 12, 2005 4’th VI Winter Workshop Series Slide 6
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• Electromechanical Transmission– Has 5 operating modes– Relies on single planetary gear– Requires 2 electric M/G’s
R
C
SICE
Speeder M/G
FD
TorquerM/G
ωe
ωs
ωΤ
BatteryPack
3φ
3φ
January 12, 2005 4’th VI Winter Workshop Series Slide 7
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• EMT Operating Modes• Mode 1: low acceleration events when ICE power
exceeds the road load– Excess engine power is used to charge the battery by using
M/G1 and M/G2 in their generating mode– When engine power matches road load but has insufficient
torque, the “torquer” M/G acts as a motor to deliver additional power to the wheels by discharging the battery.
• Mode 2: low speed, launch and light cruise– The “speeder” M/G remains in generator mode and delivers
engine power to the “torquer” via the electric path.– Excess electric power may be delivered to the battery
January 12, 2005 4’th VI Winter Workshop Series Slide 8
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• EMT – operating regimesR
C
SICE
Speeder M/G
FD
TorquerM/G
ωe
ωs
ωΤ
BatteryPack
3φ
3φ
Veh
icle
Acc
el (m
/s2)
Vehicle Speed (mph)
Mode 1
Mode 2
Mode 3
Mode 4
Mode 5
January 12, 2005 4’th VI Winter Workshop Series Slide 9
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• Mode 3: High load condition– Road load torque and power exceed the available engine torque
and power.– The battery (ESS) contributes additional boost power to both the
motor “torquer” and generator “speeder”.
• Mode 4: High cruising speeds– “Speeder” is locked up and the engine is throttled up– “Torquer” is operated in motoring or generating mode as needed
• Mode 5: Deceleration– Both M/G’s operate in generating mode to recuperate vehicle
kinetic energy to battery (ESS).
January 12, 2005 4’th VI Winter Workshop Series Slide 10
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: ElectroMechanical
• EMT operating regimes
Veh
icle
Acc
el (m
/s2)
Vehicle Speed (mph)
Mode 1
Mode 2
Mode 3
Mode 4
Mode 5
R
C
SICE
Speeder M/G
FD
TorquerM/G
ωe
ωs
ωΤ
BatteryPack
3φ
3φ
January 12, 2005 4’th VI Winter Workshop Series Slide 11
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: Flywheel Hybrids
• During 1970’s to early 1980’s U.S. DOE sponsored programs investigated ICE-Flywheel hybrid concepts– FES is the primary energy storage system– Some used mechanical CVT’s as matching elements
FD
ICE CVT
C1 C2
C3
ChainDriveAssembly
Flywheel
HypoidGear
January 12, 2005 4’th VI Winter Workshop Series Slide 12
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: Flywheel Hybrids
• Some systems used a planetary gear matching element between the driveline and the flywheel, FES– City bus applications were common development platforms
CIDI
MTFW + GearReduction
SpeedSummer
FD
FW
4:1Epicyclic
Clutch
Input
DOE ProgramFW Brake EnergyRecovery16 T City Bus100 kW CIDI750 Wh FW
January 12, 2005 4’th VI Winter Workshop Series Slide 13
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments:Battery + Flywheel
• A novel combination relied on Lead-acid battery energy storage and a flywheel for dynamic storage– Battery for continuous and low dynamic events– FES for high dynamic events and for power boosting
FWBattFDXMM/G
90 Wh18 kWh
Battery -FW combination EV
mv = 910 kg
mbatt = 500 kg
mpass = 273 kg
mGVW = 1683 kg
ηFW = 52%
Battery only EV range ~ 57 mi
Battery + FW EV range = 80 mi
January 12, 2005 4’th VI Winter Workshop Series Slide 14
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments:Battery + Flywheel
• Battery + FES system was an early attempt at combination energy storage systems for continuous and dynamic loading events– FES recharges during deceleration events AND– FES can be recharged from the battery – at slow and efficient rates
Battery PowerFWPower
FW PowerBatterychargesFW
Accel Cruise Coast Brake IdleP
t
January 12, 2005 4’th VI Winter Workshop Series Slide 15
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Historical Developments: Early Hybrids• 1905 H. Piper files U.S. patent for a petrol-electric hybrid vehicle.
Goal was to use the electric motor to assist the ICE so that higher speeds (25 mph) could be achieved.– Unfortunately, within a couple years the ICE was improved to the
point that such speeds became commonplace.• 1921 Owen Magnetic Model 60 Touring vehicle
– Uses gasoline engine to run a generatorThat supplies electric power to motorsMounted in each of the rear wheels.
• 2004 Ford Hybrid Escape– Launches in electric mode 0 25 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 16
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Hybrid Functions
• Hybrid functionality improves dramatically as M/G power increases to 50% of targeted peak power – synergy with ICE
<4035301073%FE Benefit
ZEV
Launch assist
Energy Mg’mt
Regen
Idle Stop
Functions:
NiMH, 60kgNiMH, 40kgNiMH, 20 kgVRLA, 30kgVRLA, 30kgFlooded Pb-Acid, 25 kg
Battery
ElectricElectricElectric ElectricConventionalConventionalAncillaries
Offset ISG >300V
Crank-ISG 150V
Crank-ISG 42V
Belt ISG 42V
Belt ISG 42V
Belt ISG 14V
Elect. M/G
DownsizedDownsizedDownsizedConventionalConventionalConventionalPowerTrain
<4035301073%FE Benefit
ZEV
Launch assist
Energy Mg’mt
Regen
Idle Stop
Functions:
NiMH, 60kgNiMH, 40kgNiMH, 20 kgVRLA, 30kgVRLA, 30kgFlooded Pb-Acid, 25 kg
Battery
ElectricElectricElectric ElectricConventionalConventionalAncillaries
Offset ISG >300V
Crank-ISG 150V
Crank-ISG 42V
Belt ISG 42V
Belt ISG 42V
Belt ISG 14V
Elect. M/G
DownsizedDownsizedDownsizedConventionalConventionalConventionalPowerTrain
January 12, 2005 4’th VI Winter Workshop Series Slide 17
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
ICE versus Electric: Achieving a balance
• What do we mean by synergy with ICE?• Toyota: Hybrid Passenger Vehicle Industry leader
– Prius hybrid: THS-I generation of hybrid functionality– New Prius hybrid: THS-II generation based on hybrid synergy drive– Toyota Prius-II has electric power steering, electronic controlled brakes
and electric drive air conditioning.
PICE PM/G
100 kW
0 50 100 Electric Fraction, Ef
CV
THS-IIHSD Batt
EV
THS-I
Toyota Motor Co has managed toRaise the battery warranty from 8 yearsOn PRIUS-I to 150,000 miles (10 yr)On PRIUS-II
How?By more intelligent operation and byImproving the battery terminations forLower ESR (higher efficiency)
January 12, 2005 4’th VI Winter Workshop Series Slide 18
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Vehicle Performance Targets
• Hybrid vehicles today must deliver the performance customers expect. The new HSD Prius-II was released for sale October 2003 in North America. Prius-I sales for 2003 were some 38,000 in NA and customers are now lining up to purchase the new Prius-II. CY2004 sales target in N.A. is 70,000
Launch Accel0.45g
tz6011s
tz8521s
MaximumGrade 30%
Gradeability 90 kphfor 20 min. 6%
WOT speed0% grade180 kph
ZEV Range:
Towing Capacity
Hybrids typically do not have towing capability– until the new Ford hybrid Escape
introduced Oct. 2004 that has a tow capability of 1500# (non-hybrid Escape is rated 3500# towing). Full size pickups are rated 6500# towing.
Acceleration benchmarks:Prius I, 0 60 mph time = 12.5sPrius II, 0 60 mph time = 10.5sHybrid Escape, 0 60 mph time = 11.2s
January 12, 2005 4’th VI Winter Workshop Series Slide 19
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Vehicle Performance Targets
• Applying the vehicle performance targets
Vehicle Speed, V
Axl
e To
rque
Total Power
Road Load at 0-grade
Vmax atWOT & 0-grade
mmax, tire adhesionlimited
P max, T
ransm
ission rolling, aero, grade
limited speed
Road load at 6% grade
sustain 90 kph, 20 min
V6%
Torque for 30% grade
January 12, 2005 4’th VI Winter Workshop Series Slide 20
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Vehicle Performance Targets
• So how do recent hybrid vehicle products now offered “stack-up” in terms of performance?– Historically, performance targets have dictated a peak specific power
(combined in case of a hybrid) of 10 kW/125 kg power plant
10.34750/10571295HSD8.84565/28802053Escape8.63833/10531254Prius7.351410631242Civic
(kW/125 kg)(%)(kW)(kW)(kg)
Peak specific power
Electric Fraction
M/G Power
Engine Power
Curb massVehicle
Hybrid Synergy Drive, HSD, goal is to match V6 performance with anI4 through “electric supercharging”
January 12, 2005 4’th VI Winter Workshop Series Slide 21
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Session 2
• Toyota Hybrid System: – THS-I and THS-II– Tire dynamics– Hybrid modes– Power Split operation during cruise
January 12, 2005 4’th VI Winter Workshop Series Slide 22
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Comparison of Toyota Hybrid Technology: THS-I & THS-II Power Train & Vehicle
• Example to illustrate Prius-II vehicle specifications in comparison to Prius-I
P185/65R15P175/65R14Tires
2.29 m22.23 m2Frontal area *
0.260.29Drag coefficient, Cd
1313 kg1257 kgVehicle curb weight
Electronic CVTElectronic CVTTransmission
60/51/55 mpg city/hwy/combined52/45/48 mpg city/hwy/combinedFuel Economy
Advanced Tech. PZEVSULEVEmissions
111 Nm at 4,200 rpm111 Nm at 4,200 rpmEngine Torque
57 kW at 5,000 rpm52 kW at 4,500 rpmEngine Power
4V/cylinder, VVT-i4V/cylinder, VVT-iValve system
13:1 Atkinson Cycle13:1 Atkinson CycleCompression ratio
1.5 liter, DOHC, I41.5 liter, DOHC, I4Engine displacement
Prius IIPrius I
January 12, 2005 4’th VI Winter Workshop Series Slide 23
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Comparison of Toyota Hybrid Technology: THS-I & THS-II Power Train & Vehicle
• To understand vehicle propulsion we start at the wheels– Code: P175/65R14 = <veh type> <W, tread width> <H in %W> <Drim>
Tire code: P=passenger, 123mm tread width/sidewall height as xx% Wtread, R, rim diameter (inch)
V (mph)
WH
Drimrw
2)%(298.0 treadrim
wxWHDr +
= = 0.292m Prius-I and 0.3045m Prius-II from which the final drive ratio comes out to Gr=3.95:1 in Prius-I and 4.0:1 in Prius-II
January 12, 2005 4’th VI Winter Workshop Series Slide 24
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Comparison of Toyota Hybrid Technology: THS-I & THS-II Power Train & Vehicle
• Finding the driveline final drive ratio, gfd– Must know Vmax and Nm-max
– Need tire dynamic rolling radius, rw
V (mph)
rw
Motor, Ωmax
axleωa, ma
gfd
drivelineωdl, mdl
Vmax
mphvVgVg
rVg
fd
fd
wfd
97|95.3/383)447.0/()292.0(3.586
)/(
maxmax
max
maxmax
====
Ω=
January 12, 2005 4’th VI Winter Workshop Series Slide 25
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Comparison of Toyota Hybrid Technology: THS-I & THS-II Power Train & Vehicle
• Comparison of Prius-I and Prius-II continued
201.6 V, 168 cells273.6V, 228 cellsBattery voltage
21 kW improved internal resistance
21 kW (25 kW max)Battery PowerSealed NiMHSealed NiMHBattery type
500V max274VSystem Voltage400 Nm, 0 to 1,200 rpm350 Nm 0 to 400 rpmM/G Torque
50 kW, 1,200 to 1,540 rpm33 kW 1,040 to 5,600 rpmM/G Power
Permanent Reluctance Machine, PRM
Interior Permanent Magnet, IPM
Motor/GeneratorPrius-IIPrius-I
January 12, 2005 4’th VI Winter Workshop Series Slide 26
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS-II System
• THS-II achieves higher voltage local dc bus using a conventional half bridge converter (i.e., one additional phase leg of power electronics).
• Present cost of hybridization for THS-I and THS-II systems are $66/kW to $93/kW while cost of an SI powertrain is ~$30/kW
S/A M/GNiMH6 Ah201.7 V233 Apk1400 W/kg
Half-bridgeboostconverter
Boost Ind250A, 10 kHz
1500 uF600V
10 kW 50 kW
500V (2.5x boost)
30 kW, 8-pole IPM50 kW, 8-pole IPM
500V Power Elect.
1500 uF, 600V, PPS-polyphenylene sulfide dc link bus capacitor
S/A M/GNiMH6 Ah201.7 V233 Apk1400 W/kg
Half-bridgeboostconverter
Boost Ind250A, 10 kHz
1500 uF600V
10 kW 50 kW
500V (2.5x boost)
30 kW, 8-pole IPM50 kW, 8-pole IPM
500V Power Elect.
1500 uF, 600V, PPS-polyphenylene sulfide dc link bus capacitor
January 12, 2005 4’th VI Winter Workshop Series Slide 27
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS-II System• NiMH battery with double welded terminations for 30% reduced ESR &
more compact package.
S/A M/GNiMH6 Ah201.7 V233 Apk1400 W/kg
Half-bridgeboostconverter
Boost Ind250A, 10 kHz
1500 uF600V
10 kW 50 kW
500V (2.5x boost)
Expanded view of power electronics package. NiMH battery cable connector:
Link Ind~100mmcube
January 12, 2005 4’th VI Winter Workshop Series Slide 28
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS-II System• Mechanical & Electrical Architecture• Motor/Generators are under full electronic control
R
C
S
M/G2
ICE FD
wheels
Power Split, E-CVT
M/G1
Battery
Integrated Power& Control Electronics
January 12, 2005 4’th VI Winter Workshop Series Slide 29
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Power Split Device
• Mechanical and Electrical Architecture– Depend fundamentally on the dynamics of a planetary gear set– Epicyclic gears provide speed summation– Torque splits according to port loading (power balance)
Uc
ωr
ωc
ωprp
vsωs
rs
rr
rc
SunPlanet
Ring (inside and/or outside gear)
Fundamental equation of the planetaryGear set: ratio of the difference inAngular speeds between an inner epicyclicGear and a common gear and a secondInner gear and the common gear equalsA constant – the basic ratio.
0)1()()(
=+−+−−=−
−=−=−−
crs
crcs
s
r
cr
cs
kkk
kNN
ωωωωωωω
ωωωω
January 12, 2005 4’th VI Winter Workshop Series Slide 30
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Power Split Device• Planetery gear set
– The basic ratio is negative for inside gears and positive for an outside epicyclic gear.
• Dynamics of the planetary gear set (ω is angular speed and m is torque, MKS units)
R
S
C
ωs ωrωc
011
0110)1(
_
=+
−−+
+
=+−−
=+−+
==
rrccrrcc
rrssrrss
crs
s
r
JkkJM
kkM
Jk
JMk
M
kk
ratiobasicRRk
ωωηη
ωωηη
ωωω
&&
&&
Prius I & II: Nr = 78, Np=24, Ns=30 from which k=78/30 = 2.6
January 12, 2005 4’th VI Winter Workshop Series Slide 31
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Power Split Dynamics
• THS power split dynamics
R
C
S
M/G2
ICE FD
wheels
M/G1
Batteryrw
V
Ga2r
Gr2s
Ge2s
ωama,Ja
ωfd,mfd,Jfd
ωr,mr,Jr
ωg,mg,Jg
ωe,me,Je
ωm,mm,Jm
Pe
Pb
SOCCbUoc
January 12, 2005 4’th VI Winter Workshop Series Slide 32
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Power Split Dynamics
• Expressions for M/G2 (motor) and M/G1 (gen) torque can be derived by inspection of the THS architecture– System inertias are lumped parameter– Generator effects (couple) are reflected to engine and motor ports
( )
emdlss
mgceeese
g
mmqgcse
sregceq
se
sre
se
srmdl
mkkmm
JJmg
m
JJggJJ
ggm
ggmm
1
1
2
2
2
2
2
2
2
++=
−−=
−+
−+−=
ωω
ωω
&&
&&
Steady state driveline torque expression showingTorque contribution of motor and engine mechanicalPath split
January 12, 2005 4’th VI Winter Workshop Series Slide 33
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy
• Engine and electric system matching are essential to realize geographical preferences in the market– The power split device & the electric machine CPSR – constant
power speed ratio are key elements in this strategy
R
C
S
M/G
ICE
S/A
Gearbox FD
wheelsFE(mpg)
Gsrc
4 4.5 5 5.5 6 6.5 7
ATGear shift ratio coverage = 5 5.5 6.5
Japan 10-151900 kg sedan
Europe EC1900 kg sedan
US combined2900 kg SUV
Note: most input coupled transmissions have the ICE at the planet carrier port
January 12, 2005 4’th VI Winter Workshop Series Slide 34
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy
• To further develop the propulsion system strategy we first define the power split operating modes
• Then, an efficiency optimizing strategy is defined for highway cruise that aims to hold the ICE in or near the high plateau’s of BSFC – brake specific fuel consumption (g/kWh)
Batt
R
C
S
M/G2
ICE FD
wheels
Power Split, e-CVTUn-Buffered ESS
M/G1
Epicyclic274 V Inverter
Ultra-cap
January 12, 2005 4’th VI Winter Workshop Series Slide 35
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy
• Operating modes – In this study five modes will be
defined• Batt-EV & Regen mode• Normal driving mode• Battery charge mode• Power boost mode• Negative split mode
• Some power split systems enter negative split as a means to further lug the engine (lower its speed at given torque)
January 12, 2005 4’th VI Winter Workshop Series Slide 36
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy
• Positive split is primarily used (which is most of the time) when ESS state of charge, SOC, is low, vehicle speed is relatively low and the engine delivers power to the ESS –battery.
• Negative split is used when the ESS, SOC is high, vehicle is under cruise condition with engine ON.– ESS discharges into generator (runs in motoring quadrant(s))– Generator in motoring mode drives engine speed lower to further
optimize fuel efficiency
• Series mode is used when parked, during idle and for reverse (Batt-EV mode).
January 12, 2005 4’th VI Winter Workshop Series Slide 37
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Modes• Batt-EV (electric drive and regeneration mode)
– Engine OFF and generator not used.– Also called series mode
Batt-EV and Regeneration Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
Note: series modeFor reverse – speedConstrained in S/WBy rev limiter.
January 12, 2005 4’th VI Winter Workshop Series Slide 38
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Modes• Normal driving, cruise mode
– Engine ON, power splits from engine to wheels mechanically and via generator electrically.
– ESS has nominal SOC, electrical power circulates from engine viagenerator to the motor where it sums mechanically with engine mechanical path power Normal Driving Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
January 12, 2005 4’th VI Winter Workshop Series Slide 39
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Modes
• Battery charge mode – Vehicle parked or during idle
Battery Charging Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
January 12, 2005 4’th VI Winter Workshop Series Slide 40
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Modes
• Power boost mode– Engine torque augmentation– Similar to EMT mode 3, engine has insufficient torque/power to meet
road load demandPower Boost Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
January 12, 2005 4’th VI Winter Workshop Series Slide 41
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Modes• Negative split mode
– Forced engine lugging to optimize fuel economy– Engine control strategies also come into play in the form of advanced or
retarded VVT when SOC is low• Advanced VVT lowers speed, but higher torque op point• Retarded VVT increases speed, lowers torque op point
Negative Split Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
January 12, 2005 4’th VI Winter Workshop Series Slide 42
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy
• Overall strategy is to operate the engine at high torque, low speed, most efficient operating points– Atkinson cycle provides inherent ~10% higher thermodynamic
combustion efficiency– Improves highway FE
ICE
GEN
ESSBattery
MOT
FD
Inverter
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
1000 1500 2000 2500 3000 3500 4000 4500 5000Engine speed (rpm)
210215
220230
250
270
300
400
700BSFC
Bra
ke m
ean
effe
ctiv
e pr
essu
re x
100
(kN
/m2 ) Te
Peng
70
60
50
40
30
20
10
Engi
ne p
ower
(kW
)200
150
100
50
0
Torq
ue (N
m)
(me-ωe) constrainedmapping points
Torque reservefor driveability
January 12, 2005 4’th VI Winter Workshop Series Slide 43
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy• Efficiency optimizing strategy for cruise mode
– Define using N/V plot– Piecewise linear approximation of the engine control strategy– Generator speed responds to these discontinuties – artifact of the method
0 20 40 60 80 1005000
0
5000
1 .104
Speed, mph
Ang
ular
spee
d, ra
d/s
5.544 103×
3.712− 103×
N m i( )
N e i( )
N g i( )
0
1000 V i( )
Note that the generator speed is restricted to 3rd quadrant operation. LoweringGenerator speed increases engine speed and vice versa regardless of Motor speed (i.e., vehicle speed)
January 12, 2005 4’th VI Winter Workshop Series Slide 44
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
THS: Propulsion System Strategy• Lever “stick” diagrams are
sometimes used to illustrate the interplay of engine and electric M/G’s in the power split system.
RCS
Vehicle launch
Cruise
Engine Cranking
AccelerationVehSpeed
EngineSpeed
S/ASpeed
292.004136
167.170167
10 V i( ).
ω r i( )
ω c i( )
ω s i( )
100 t i( )0 2 4 6 8 10
200
0
200
400
Time (s)
Com
pone
nt S
peed
s (m
/s, r
ad/s
)
R
C
S
M/G2
ICE FD
wheels
Power Split, E-CVT
M/G1
BatteryVehicle Speed
M/G2 rpm
Engine rpm
M/G1 rpm
January 12, 2005 4’th VI Winter Workshop Series Slide 45
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Power Split Propulsion System Strategy
• The strategy to be employed can be described in look up table format (and applied to the THS-I system)
+430-19374620280080
-1110-26044043220070
-860-28883465170060
+430-10272890180050
+670-6082310150040
-3,290-45041733OFF30
000OFF0
Battery PowerPb (W)
Generator SpeedNg (rpm)
Motor SpeedNm (rpm)
Engine SpeedNe (rpm)
Vehicle SpeedV (mph)
January 12, 2005 4’th VI Winter Workshop Series Slide 46
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Observations on the selected Power Split strategy– Batt-EV mode 0 30mph then– Batt-charge mode at 40 and 50 mph– Power boost mode at 60 and 70 mph– ICE to near WOT torque at 80 mph
• At max vehicle speed the PS motor will be at max speed – As will the planetary gear set
• Engine operation at WOT torque (Ne~ 4000 rpm) will occur during high load conditions, grade, etc.
January 12, 2005 4’th VI Winter Workshop Series Slide 47
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• The maximum Batt-EV mode speed is limited by the generator max speed– Ne = 0 engine is OFF– Ng = 6500 rpm maximum
mphV
smV
kgr
V
ci
ci
fd
wgmci
3.43447.035.19
/35.19)95.3(6.2
)292.0(6.680
==
==
Ω=
ICE
GEN
ESSBattery
MOT
FD
Inverter
Max engine cut-in speed can be approachedBy very gradual acceleration in Batt-EV mode
January 12, 2005 4’th VI Winter Workshop Series Slide 48
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• First step is to calculate the road load during cruise
• Froll = 98.33N and Faero = 0.4103V2
2
3
3
0
20
31.29.0
)(Pr29.0@/225.1
0/902.9
1254008.0
sin5.0cos
mWHA
iusCSTPmkg
gradesmg
kgmR
gmVACgmRF
f
d
air
v
vfdairvt
==
==
−==
==
++=
ρ
α
αρα
January 12, 2005 4’th VI Winter Workshop Series Slide 49
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Steps used in the evaluation of power split operation• 1st: Calculate the road load for the stated condition• 2nd: Reflect the road load to the driveline – speed and
torque• 3rd: Assign the engine speed per the strategy• 4th: Use the planetary gear speed equation to determine
the generator speed,• 5th: Calculate the engine mechanical path torque per the
planetary gear torque expression (see power split device slides)
• 6th: Calculate all power flows and insure balance to match the stated battery loading condition.
January 12, 2005 4’th VI Winter Workshop Series Slide 50
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
VehicleV = 30 mphFt = 172 NPt = 2.31 kW
DrivelinePdl = 2.81 kWωdl =181.4 r/smdl=15.5 Nm
Motor/Ring GearPm = 2.81 kWωm = 181.4 r/smm = 15.5 Nm
EnginePem = 0ωe = 0mem = 0me = 0Pe = 0
GeneratorPg = 0ωg = -471.6 r/smg = 0
Pb =-3.9 kW PM/G = 0
gfd = 3.95ηfd = 0.82
Electric power path:ηmi = ηm*ηi = 0.91*0.94 = 0.855• V=30 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 51
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Engine and M/G maps for 30 mph
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
January 12, 2005 4’th VI Winter Workshop Series Slide 52
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
VehicleV =40 mphFt = 229.5 NPt = 4.1 kW
DrivelinePdl =5 kWPdlm = 4.5 kWPdle = 0.5 kWωdl =241.9 r/smdl=20.67 Nm
Motor/Ring GearPm =0.5 kWωm = 241.9 r/smm = 2.07 Nm
EnginePem = 4.5 kWωe = 157 r/smem = 28.62me = 41.2Pe = 6.47 kW
GeneratorPg =1.47 kW ωg = -63.74 r/smg = 6.74 Nm
Pb = +670WPM/G = 585W
Electric power path:ηmi = ηm*ηi = 0.91*0.94 = 0.855
gfd = 3.95ηfd = 0.82
• V=40 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 53
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Engine and M/G maps for 40 mph
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
January 12, 2005 4’th VI Winter Workshop Series Slide 54
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
VehicleV =50 mphFt = 303 NPt = 6.78 kW
Motor/Ring GearPm =1.12 kWωm = 302mm = 3.71 Nm
EnginePem = 7.14 kWωe = 188.5 r/smem = 37.9 Nmme = 48.7 NmPe = 9.175 kW
GeneratorPg = 2.035 kWωg = -107.5 r/smg = 18.93 Nm
Pb = +430 WPM/G =1.31 kW
Electric power path:ηmi = ηm*ηi = 0.91*0.94 = 0.855
gfd = 3.95ηfd = 0.82
DrivelinePdl =8.27 kWPdlm = 7.14 kWPdle = 1.12 kWωdl =302.3 r/smdl= 27.35
• V=50 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 55
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Engine and M/G maps for 50 mph
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
January 12, 2005 4’th VI Winter Workshop Series Slide 56
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
VehicleV =60 mphFt = 393.5 NPt = 10.6 kW
Motor/Ring GearPm =4.125 kWωm = 362.8 r./smm = 11.4 Nm
EnginePem = 8.745 kWωe = 178 r/smem = 49.1 Nmme = 75.2 NmPe = 13.385 kW
GeneratorPg =4.64 kW ωg = -302.5r/smg = 15.33 Nm
Pb = -860 WPM/G = 4.824 kW
Electric power path:ηmi = ηm*ηi = 0.91*0.94 = 0.855
gfd = 3.95ηfd = 0.82
DrivelinePdl =12.87 kWPdlm = 8.745 kWPdle = 4.125 kWωdl =362.8 r/smdl=35.47 Nm
• V=60 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 57
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Engine and M/G maps for 60 mph
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
January 12, 2005 4’th VI Winter Workshop Series Slide 58
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
VehicleV =70 mphFt = 500 NPt = 15.65 kW
Motor/Ring GearPm =4.73 kWωm = 423.3 r/smm = 11.17 Nm
EnginePem = 14.37 kWωe = 230 r/smem = 62.5 Nmme = 85 NmPe = 19.55 kW
GeneratorPg = 5.18 kWωg = -272.6 r/smg = 19 Nm
Pb = -1.1 kWPM/G = 5.532 kW
Electric power path:ηmi = ηm*ηi = 0.91*0.94 = 0.855
gfd = 3.95ηfd = 0.82
DrivelinePdl =19.1 kWPdlm = 14.37 kWPdle = 4.73 kWωdl =423.3 r/smdl=45.12 Nm
• V= 70 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 59
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Engine and M/G maps for 70 mph
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
January 12, 2005 4’th VI Winter Workshop Series Slide 60
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
ICE
GEN
ESSBattery
MOT
FD
Inverter
VehicleV =80 mphFt = 623 NPt = 22.3 kW
Motor/Ring GearPm =4.374 kWωm = 483.7 r/smm = 9.04 Nm
EnginePem = 22.786 kWωe = 293 r/smem = 77.8 Nmme = 100 NmPe = 29.27kW
GeneratorPg = 6.486 kWωg = -202.8mg = 21.6 Nm
Pb = +430WPM/G =5.116 kW
Electric power path:ηmi = ηm*ηi = 0.91*0.94 = 0.855
gfd = 3.95ηfd = 0.82
DrivelinePdl =27.16 kWPdlm = 22.786 kWPdle = 4.374 kWωdl =483.7 r/smdl=56.15 Nm
• V=80 mph
January 12, 2005 4’th VI Winter Workshop Series Slide 61
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Engine and M/G maps for 80 mph
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
January 12, 2005 4’th VI Winter Workshop Series Slide 62
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS Propulsion System in Cruise Mode
• Composite engine and M/G maps
115
90
65
35
0
Torq
ue (N
m)
0 1000 2000 3000 4000 5000Engine Speed (rpm)
200
210
220
230
240
250
270
290
Consumptiong/kWh
20 kW
15 kW10 kW 8 kW
35 kW
55 kW
T(Nm)
80
60
40
20
0
Speed (krpm)0 1 2 3 4 5 6
Generator map
93
88
82
73
Atkinson Engine Map
T(Nm)
300
240
200
120
80
0
Speed (krpm)0 1 2 3 4 5 6
93
88
82
73
Motor map
(me-ωe) constrainedmapping points
Torque reservefor driveability
Electric subsystemtorque reserve forpower boosting
January 12, 2005 4’th VI Winter Workshop Series Slide 63
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
PS System Summary
• Conclusions– Cruise mode control strategy must optimize both engine and
generator efficiency– Hybrid strategy pushes engine operation high on T-N map
resulting in reduced engine torque for transients– Motor operates at relatively low power levels during cruise– But, the motor maintains sufficient reserve to augment the
engine torque during transient maneuvers, passing, negotiating grades, braking, etc
– Battery SOC is maintained via the generator by additional loading on the engine
– During boosting the battery augments generator power
January 12, 2005 4’th VI Winter Workshop Series Slide 64
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Session 3
• Ford-Volvo-Aisin, FHS System– Very similar to the THS system, with the addition of output
gearing– Still an input coupled power split– Motor is now offset geared from planetary ring gear– Power and control electronics are now integral to the e-CVT
transmission.
• Hybrid Escape introduced in Oct. 2004 as MY2005 hybSUV
January 12, 2005 4’th VI Winter Workshop Series Slide 65
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Hybrid Escape e-CVT
• Ford Hybrid System
2.3L ICE
e-CVT
HV Battery
2.3L Atkinson
Cycle Engine
Planetary
GearOutputGear
To Wheels
TractionGenerato
r
TractionMotor
AC-DCInverters
TractionHV Battery
Mechanical PathElectrical Path
January 12, 2005 4’th VI Winter Workshop Series Slide 66
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Hybrid Escape e-CVT
• Model development
R1
C1
S1 M/G1
ICEFD
wheels
M/G2
EpicyclicInput
300 V
BattUltra-cap Inverter
OWCB1
N1
N2
N2
OutputGears
Fixed link, PowerSplit with Gear
An ultracapacitor and battery combination isShown to illustrate that ESS system upgrades are possible and also recommended for increased ESS longevity
January 12, 2005 4’th VI Winter Workshop Series Slide 67
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Hybrid e-CVT: Sidebar on ESS
• It is small wonder then, with this discussion of hybrid vehicles and energy storage systems that energy storage may indeed represent a >$10B market by 2010.
Potential: 1000 Wh/kg
Nissan AltraEVSONY, SAFTlaboratory400 to 1200300100 to 150Lithium-Ion
Potential: 2200 cycle
life
WWU Viking 23SAFT110300 to 600mature10 to 20-60 to +60-40 to +601000 to
200050 to 20035 to 57Nickel-Cadmium
Potential: 120 Wh/kg, and 2200 cycle life
Toyota RAV4-EV,
Toyota Prius,
Chrysler Epic
minivan, Honda EV, Chevy S-10
Panasonic, Ovonic, SAFT
115 to 300525 to 540prototype600 to 1500150 to 25050 to 80Nickel-Metal
Hydride
Potential: 55 Wh/kg, 450 W/kg, and 2000 cycle
life
Audi Duo, GM EV1 (VLRA), Solectria
Force
Delphi, Horizon,
Electrosourceproduction500 to 800240 to 41235 to 42Advanced
Lead Acid
CARTA bus,
SolectriaE10
(sealed)
Trojan, Hawker, Exide,
Interstate
75100 to 125production2 to 3ambient-18 to +70200 to 40075 to 13025 to 35Lead-Acid
Other Notes
Vehicles Used_In
Principal Manuf.
Future Cost
$/kWh]
Current Cost
[$/kWh]Maturity
Self Discharge Rate[% per month]
Storage Temp.
[C]
Operating Temp.
[C]
Cycle Life
Power Density [W/kg]
Energy Density [Wh/kg]
Battery Type
January 12, 2005 4’th VI Winter Workshop Series Slide 68
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Hybrid e-CVT: Sidebar on ESS
• Ultracapacitors are becoming a viable ESS technology
Above, 2700F BoostCAP & New D-Cell BoostCAP.Below, D-Cell 15V 58 F module
January 12, 2005 4’th VI Winter Workshop Series Slide 69
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Power Split: Electrical System Modeling
• Motor-generator and power electronics are modeled conventionally: – M/G as torque source or sink dependent on angular speed with
load dependent loss– Inverter as switching elements with load dependent losses
• Control strategy is modeled as state transition map based on hybrid dynamical systems theory – Each operating mode must be modeled:– (1) standstill, (2) Creep, (3) Power split, (4) Parallel, (5) Regen
brake• Electrical Energy Storage System model for state-of-
charge variation with load demand
January 12, 2005 4’th VI Winter Workshop Series Slide 70
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Power Split: Electrical System Modeling
• State transition map
q1
q2
q3
q4
q5
Standstill
Creep
PowerSplit
Parallel
regeneration
Enter
State Transition Map, ex
e1
e2
e3
e4
e5
e6 e7 e8
e9
e10e11In state q4 we have that (ρ=1/k):
fme
ee
r
g
re
mmmJ
J −++
=+
+
=+
=
ρω
ρ
ω
ωρ
ω
1)1(
01
1
2&
Brake B1=ON
January 12, 2005 4’th VI Winter Workshop Series Slide 71
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Power Split: Electrical System Modeling
• Model must account for ESS SOC variation
dtCSdCI
IVPdtSOCdCV
dtdW
PRIVIIVP
brb
bocstoredbrocc
availibocbbdbat
)0(
)()(
=∴
===
=−==
VocVd
Battery Ri
Pbat
Ib
Substitute for Ib in equation for PbatThen solve the resulting quadratic to obtain:
( )bri
ocibatoc
briocbrbat
CRVRPV
dtSOCd
thatFinddtSOCdCRV
dtSOCdCP
24)(
:_
)()(
2 −−+
−=
−=
Define Cbr = battery rated capacity, AhNoting that: RiCbr = τbat
January 12, 2005 4’th VI Winter Workshop Series Slide 72
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Power Split: Electrical System Modeling
• Mechanical System Modeling
++++=
=Ω=
dttdUMgMUtUACgMR
Gr
tm
rtUG
Gt
vvofdvofd
wf
w
fdafdf
)()sin())((21)(
)()(
2 αρ
ω
ωe, me
ωr, mr
ωg, mg
ωf, mfR1
C1
S1 M/G1
ICEFD
wheels
M/G2
EpicyclicInput
300 V
BattUltra-cap Inverter
OWCB1
N1
N2
N2
OutputGears
Fixed link, PowerSplit with Gear
Countershaft
ωm, mm
fmr
reeregr
rgergrg
mmmthatnoting
mkkmJ
kkJJ
kk
mk
mJkJk
J
kDefine
==
++=
+
−++
−=+−
+
=
:_
111
1)1(1
1:
2
2
2
ωω
ωω
ρ
&&
&&
For each operating state reflectRoad load conditions to power splitM/G’s and engine
January 12, 2005 4’th VI Winter Workshop Series Slide 73
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Power Split: e-CVT Dynamics
• FHS system dynamics
R
C
S
M/G2
ICEFD
wheels
M/G1
Battery
rw
V
ga2f
gr2s
ge2s
ωamaJa
ωr,mr,Jr
ωg,mg,Jg
ωe,me,Je
ωm,mm,Jm
PePb
SOCCbUoc
N1
N2
N3
Pe
ωfd,mfd,Jfd
gm2r
gm2f
gf2r
Input split with fixed output gearing
Counter shaft
January 12, 2005 4’th VI Winter Workshop Series Slide 74
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
FHS: e-CVT Power Split Dynamics
• Expressions for M/G2 (motor) and M/G1 (gen) torque can be derived by inspection of the THS architecture– System inertias are lumped parameter– Generator effects (couple) are reflected to engine and motor ports
( )
emfdss
sefm
srrmcs
mgceeqese
g
mmqfa
gccsegcfa
eqcsecsmfm
fd
mNN
kkm
NNm
ggggg
JJmg
m
Jg
JgJg
Jgmgmg
m
++
=
=
−−=
−+
−+−=
3
2
1
2
22
22
2
222
1
1
111
ωω
ωω
&&
&&
Steady state driveline torque expression showingTorque contribution of motor and engine mechanicalPath split
January 12, 2005 4’th VI Winter Workshop Series Slide 75
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Session 4
• GM-Allision Advanced Hybrid System, 2-mode– Introduces clutches into basic power split– Dual planetary e-CVT with both input and output coupling– Input split and compound split performance– Synchronous shift from low range to high range
• Compound split promotes induction machine use
January 12, 2005 4’th VI Winter Workshop Series Slide 76
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
GM-Allision Advanced Hybrid System, 2-mode
• AHS-2 system– Mechanical and electrical architecture
R
C
S
M/G
ICE FD
wheelsBattery
R
C
S
M/G
Compound Split, e-CVT
The AHS-2 system appears suited to heavyVehicles such as city buses, trucks and fullSize SUV’s.
January 12, 2005 4’th VI Winter Workshop Series Slide 77
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
GM-Allison, AHS-2• Compound split E-VT exhibits 2-modes: high and low range without need
for gear shifts.– Two “mechanical” points of power split at input plus two “mechanical” points of output split.– M/G electrical power versus vehicle speed exhibits the mechanical points:
M/G1M/G2
Pe
mechanical points
Pe
Uv, veh spd
Mode switching requires clutch activations synchronously withM/G speed = zero points
January 12, 2005 4’th VI Winter Workshop Series Slide 78
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System
• AHS-2 model development• Mode 1 = Input Split
– Low range & reverse– E1 = differential– E2 = torque mult– C1=1, C2=0, C3=1– M/G1=gen, M/G2=mtr
• Mode 2 = Compound Split– High range, highway– Towing, grades– E1=E2=differential– C1=1, C2=1, C3=0
• Neutral mode: C2=C3=0
R1
C1
S1 M/G1
ICE
FD
wheels
R2
C2
S2M/G2
Compound Split, EVTUn-Buffered ESS
CL1
CL2
CL3EpicyclicInput
EpicyclicOutput
300 V
BattUltra-cap Inverter
January 12, 2005 4’th VI Winter Workshop Series Slide 79
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System
• AH2 model development– Compound split mode: input power splits into 2 paths which
recombine at the output differential, E2– Benefit of compound split is reduced M/G speed range made
possible by introduction of clutches and synch shift– M/G1 and M/G2 can be induction machines
• M/G operating modes versus vehicle speed– V<0 reverse, engine at idle, M/G2 = motoring in (-) dir and M/G1
spins faster in (-) direction– V>0 forward, engine speed ramps up, M/G2=motoring in (+) dir
and M/G1 spins in (-) direction but slowing down.– At a particular vehicle speed, Vshift, M/G1 speed =0
January 12, 2005 4’th VI Winter Workshop Series Slide 80
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System Modes & Dynamics
• Input split (mode 1)
R1
C1
S1 M/G1
ICE
FD
wheels
R2
C2
S2M/G2
EVT in Mode 1CL1=1, CL2=0, CL3=1
CL1
CL2
CL3
BatterySOCCbUoc
Pb
Pe
ωe,me,Je
ωg,mg,Jg
rw
V
ωa
ma,Ja
ga2f
ωfd,mfd,Jfd
ωr2,mr2,Jr2
ωg,mg,Jg
Counter shaft
gi2g
ge2g
Intermediate shaft
gm2i
gf2m
gr2m
ωi,mi,Ji
ωr1,mr1,Jr1
E1-Differential E2- TorqueMultiplier
January 12, 2005 4’th VI Winter Workshop Series Slide 81
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System Modes & Dynamics
• Compound split (mode 2)
R1
C1
S1 M/G1
ICE
FD
wheels
R2
C2
S2M/G2
EVT in Mode 2CL1=1, CL2=1, CL3=0
CL1
CL2
CL3
BatterySOCCbUoc
Pb
Pe
ωe,me,Je
ωg,mg,Jg
rw
V
ωama,Ja
ga2f
ωfd,mfd,Jfd
ωr2,mr2,Jr2
ωg,mg,Jg
Counter shaft
gi2g
ge2g
Intermediate shaft
gm2i
gf2m
gr2m
ωi,mi,Ji
ωr1,mr1,Jr1
January 12, 2005 4’th VI Winter Workshop Series Slide 82
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System
0 20 40 60 80 1001000
0
1000
2000Input split mode below sync shift
Vehicle Speed, mph
Ang
ular
spee
ds, r
pm
1.8 103×
392.197−
n 0 i( )
n e i( )
0
10015− V i( )
0.447
Engine ramps to steady state, Nss, at V=30 mph
• M/G operating modes versus vehicle speed– Synchronous shift when
V=Vshift, M/G1 speed = 0 (1st
mech pt)– Vshift<V< Vs3, both M/G1 and
M/G2 motoring in (+) dir– At Vs3, M/G2 speed =0 (2nd
mechanical point)– Vs3<V<Vs4 have M/G2
motoring in (-) dir to add torque to M/G1 and to the engine
– V>Vs4 have M/G1 = gen.
0 20 40 60 80 1005000
0
5000
1 .104 Input split mode, below sync shift
Vehicle speed, mph
Ang
ular
spee
d, rp
m
5.648 103×
4.012− 103×
n m1 i( )
n m2 i( )
0
10010− V i( )
0.447
At synchronous shift point, Vshift = 33 mph, the Output shaft speed, No=1294 rpm and Nm1=4659 rpm
January 12, 2005 4’th VI Winter Workshop Series Slide 83
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System
0 20 40 60 80 1001000
2000
3000
4000Compound split mode above sync shift
Vehicle speed, mph
Ang
ular
spee
d, rp
m
3.804 103×
1.294 103×
n 0 i( )
n e i( )
10015− V i( )
0.447
0 20 40 60 80 1001 .104
0
1 .104 Compound split mode above sync shift
Vehicle speed, mph
Ang
ular
spee
d, rp
m
9.016 103×
9.745− 103×
n m1 i( )
n m2 i( )
0
10010− V i( )
0.447
Engine remains at Nss, No continues to climb inDirect relation to vehicle speed, V
At 1st mech point, Vs1 Nm2=0 while V=53.3 mphNm1=2940 rpm. At 97 mph, Nm1=9 krpm, Nm2=-9750
• M/G operating points versus vehicle speed
• Input split mode:
• Compound split mode02
01
0
)1()1(
1047.0
nknknnkn
rVg
n
m
em
w
fd
+=−+=
=
kkk
nkknkn
knnknNn
EEem
em
sse
==
+−−=
−+===
210
22
01
)1)(1(
)1(1800
January 12, 2005 4’th VI Winter Workshop Series Slide 84
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
AHS-2 System• AHS-2 summary
– For modest values of the epicyclic basic ratio the M/G speed regimes are indeed reasonable.
– For k>3 the speeds tend to become excessive– K=2.6 was assumed here
• Composite M/G, Vehicle and Engine speeds
-10 0 10 20 30 40 50 60 70 80 90 100V, mph
N(krpm) 10
8
6
4
2
0
-2
-4
-6
-8
-10
Vs1 Vshift Vs2 Vs3 Vs4Rev Forward
Nm2
Ne
Nout
Nm1AHS-2 EVT
January 12, 2005 4’th VI Winter Workshop Series Slide 85
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Session 5
• Renault Infinitely Variable Transmission, IVT– Appears derived from GM-Allision AHS-2 concept– Emphasis on bulk of power transmission via mechanical path– Variator path is electrical– Variator controls the overall transmission ratio
• Compound split (electric variator) promotes induction machine use
January 12, 2005 4’th VI Winter Workshop Series Slide 86
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System• Compound split without synchronous shift
– Renault sought out the most flexible and most efficient variator topology– An electric variator was selected
• The IVT transmission concept
M/G2 M/G1
R1
R1
C1
C1
S1S2
C2
C2
R2
R2
ICE
FD
gf2d
gfd
PM/G
ωvoωvi ωi
ωo
January 12, 2005 4’th VI Winter Workshop Series Slide 87
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System
• IVT model development
E1
E2
S1
C1
R1
M/G1
M/G2S2
C2
R2
ICE
ωvi
ωvo
ωiωi
ωo
ωo
PM/G
M/G2 M/G1
R1
R1
C1
C1
S1S2
C2
C2
R2
R2
ICE
FD
gf2d
gfd
PM/G
ωvoωvi ωi
ωo
January 12, 2005 4’th VI Winter Workshop Series Slide 88
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System
• IVT model development
E1
E2
S1
C1
R1
M/G1
M/G2S2
C2
R2
ICE
ωvi
ωvo
ωiωi
ωo
ωo
PM/G
M/G2 M/G1
R1
R1
C1
C1
S1S2
C2
C2
R2
R2
ICE
FD
gf2d
gfd
PM/G
ωvoωvi ωi
ωo
E1
E2
S1
C1
R1
M/G1
M/G2 S2
C2
R2
ICEPM/G
Vb
Pb
ωvi
ωvo
ωo ωo
ωiωi
Compound Splitmechanical path
Electric Variator
January 12, 2005 4’th VI Winter Workshop Series Slide 89
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System• IVT model development
– Planetary gear sets E1 & E2 may have different basic ratios– Define the planetary gear element speeds at each carrier – This will result in expressions for ωi and ωo.
E1
E2
S1
C1
R1
M/G1
M/G2 S2
C2
R2
ICEPM/G
Vb
Pb
ωvi
ωvo
ωo ωo
ωiωi
Compound Splitmechanical path
Electric Variator
22
2
222
11
1
111
111
111
rE
E
sEc
rE
E
sEc
kk
k
kk
k
ωωω
ωωω
+
+
+=
+
+
+=
January 12, 2005 4’th VI Winter Workshop Series Slide 90
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System
• IVT model development
22
2
222
11
1
111
111
111
rE
E
sEc
rE
E
sEc
kk
k
kk
k
ωωω
ωωω
+
+
+=
+
+
+=
E1
E2
S1
C1
R1
M/G1
M/G2 S2
C2
R2
ICEPM/G
Vb
Pb
ωvi
ωvo
ωo ωo
ωiωi
Compound Splitmechanical path
Electric Variator
oE
E
voEi
iE
E
viEo
kk
k
kk
k
ωωω
ωωω
+
+
+=
+
+
+=
2
2
2
1
1
1
111
111
January 12, 2005 4’th VI Winter Workshop Series Slide 91
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System
• IVT model development– Some definitions, then solve the preceding sets of equations for
E1 and E2 speeds as:
2
2
2
22
1
1
1
11
1
11
1
11
E
E
E
E
E
E
kkk
kkk
+=
+=
+=
+=
β
α
β
α
−−
−−=
vo
vi
o
i
ωω
ββαβ
ββα
ββα
βββα
ωω
21
21
21
1
21
2
21
21
11
11
January 12, 2005 4’th VI Winter Workshop Series Slide 92
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Renault IVT System
• IVT model development– Electric variator system– ESS capacity = 0 system is “AT-like”– ESS capacity = low, system is “mild” hybrid w/ stop/start, regen, boost– ESS capacity = high, system is “full” hybrid w/ “mild” + ZEV range
S1
C1R1
S2
C2 R2
E1
E2
ωvi
ωvo
ωi ωo
mi
mvo
mvi
mo
IVT - quadripole elementE1
E2
S1
C1
R1
M/G1
M/G2 S2
C2
R2
ICEPM/G
Vb
Pb
ωvi
ωvo
ωo ωo
ωiωi
Compound Splitmechanical path
Electric Variator
January 12, 2005 4’th VI Winter Workshop Series Slide 93
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Conclusions and Wrap-up
• Historical developments during the early 20th century explored combining ICE’s with electric machines – hybrid
• Globally, automotive OEM’s have converged to the power split hybrid transmission– Decouples engine from wheels so long as output power is met– Provides all hybrid transmission features plus emissions
reduction– Transmits bulk of engine power mechanically to wheels whereas
variator – electric path, determines its overall ratio
• Power split transmissions rely on 2 electric machines
January 12, 2005 4’th VI Winter Workshop Series Slide 94
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Conclusions and Wrap-up
• Power split transmissions, or, electronic CVT’s, have emerged along two distinct development paths– Single planetary gear, input coupled, power split preferred by
Toyota and Ford– Dual planetary gear, input/compound split, preferred by GM and
Renault (and others)
• Efficiency of the variator, as in mechanical CVT’s, remains the main development area:– Need for high power density & efficient electric machines– Need for compact and highly efficient power electronics– Need for high energy throughput electric energy storage system
January 12, 2005 4’th VI Winter Workshop Series Slide 95
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Conclusions and Wrap-up• Economics of hybrids:• CO2 reduction = Fuel consumption reduction = Fuel economy benefit
0 50 100 150 200 250 300 350 400 450
$1400 +$1400 +$2800 +$3200 +$5600Base cost ------> technology increment
CO2Reduction (%) 70
60
50
40
30
20
10
0
$18/%FE
$125/%FE
SI-Base
GDI
DownsizedLean BurnGDI
4V HSDIDiesel
Lean BoostedDownsized GDIMild Hybrid
Honda CivicIMA
Ricardo IMOGENMild Hybrid Diesel$900 in 2006
Prius THS-I$3500 in 2006
Prius THS-I$5300 in 2003
50% FC Reduction= 100% FE Improvement
Source: Ricardo & UC Davis ITS
benefit
lincrementametric FE
Value%$
=
−=
benefit
benefitbenefit FC
FCFE
%100%
100%
January 12, 2005 4’th VI Winter Workshop Series Slide 96
Comparative Assessment of Hybrid Vehicle Power Split Transmissions
Conclusions and Wrap-up
• Current market prices for hybrid electric cars– Hybrid vehicle market expected to reach 4.5 M units/yr (6%) in 2013– Drivers: higher energy costs and more stringent emissions regulations
Ford Escape Hybrid MSRP Range: $26,780- $28,405 »Buy Now »More Info
Honda Insight
MSRP Range: $19,180- $21,380 »Buy Now »More Info
Honda Civic
MSRP Range: $19,650- $20,950 »Buy Now »More Info
Toyota Prius
MSRP: $20,295 »Buy Now »More Info