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Evaluation of 2-Motor
Hybrid Architectures
James PotterZF Special Driveline Technology
Hybrid Systems Contents
� Single Planetary Gear Set Systems
� Input Summing Hybrid
� Output Split Hybrid
�Dual Planetary Gear Set Systems
� Compound Split Hybrid
� Triple Planetary Gear Set Systems
� Compound Split Hybrid
� Two-Mode Hybrid
MG1MG2
Input Summing Hybrid System
� Hybrid Vehicle Applications� Ford Escape
� Toyota Prius Synergy Drive
� Features� Electric CVT – Single planetary transmission
� Generator can directly power the traction motor
� No torque converter → E-CVT launch
� PowerSplit Myth
� The PowerSplit system is advertized by both Toyota and Ford as a combination of both the parallel and series hybrid. However, even though there are operational points where the generator can absorb 100% of the engine power transferred into the system, the engine remains mechanically coupled to the drive axle. This pseudo-series hybrid operational point is unsustainable due to the variance in efficiency between the mechanical and electrical paths, therefore, the system would vary between charge depleting, charge neutral and charge increasing states.
� The PowerSplit argument can be applied to any two or more motor system, as long as one of the motors (generators) is attached to a different system node, relative to the traction motor, allowing one motor to act as a generator while the other motor provides motoring/tractive torque.
Input Summing Hybrid SystemMotor Power Ratio
PowerSplit Hybrid System
-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.02.53.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Transmission Torque Ratio
Po
wer
Ra
tio
, P M
oto
r/P
En
gin
e
PM1/Peng
PM2/Peng
Cross-Over Point
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90
Ratio: Sun/Ring Gear Teeth
Co
up
lin
g P
oin
t
Prius & Escape
Coupling Point
Expected overall ratio spread ≈0.7:1 15:1
( )1
11 1RingSun
Ring
Engine
MG
NNRatio
N
P
P
+−=
Input Summing Hybrid SystemMotor Speed Gains
-25
-20
-15
-10
-5
0
5
10
15
0246810121416
Transmission Torque Ratio
Moto
r Speed G
ain
MG1
MG2
MG1 limits speed when;
Ratio < 0.4 and
Ratio > 4.0
Note: Assumes a maximum motor speed of 15,000 rpm
Prius & Escape
Output Split Hybrid System
MG1 MG2
� Hybrid Vehicle Applications
� Chevrolet Volt
� Features
� Motor integration ease
� Poor launch drivability
� Not practical at high torque ratios
The Volt avoids the launch issues by using a
brake to lock the ring gear during low speed
operation.
Output Split Hybrid SystemMotor Power Ratio
Output Split Hybrid System
-5
-3
-1
1
3
5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Ratio
Po
wer
Rati
o, P M
oto
r/P
En
gin
e
PM1/Peng
PM2/Peng
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Planetary Ratio, NSun/NRing
Co
up
lin
g P
oin
t
Coupling Point
Expected overall ratio spread ≈0.7:1 15:1
+
⋅−=
)(12
RingSun
Ring
Engine
M
NN
RatioN
Power
Power
Output Split Hybrid SystemMotor Speed Gains
-5
0
5
10
15
20
25
30
35
0246810121416
Transmission Torque Ratio
Moto
r Speed G
ain
MG1
MG2
MG2 limits speed when the torque ratio is less than 0.6
Compound Split Hybrid System
� Hybrid Vehicle Applications
� Lexus HS250h & RX400h
� Toyota Camry & Highlander
� Features
� Similar to the Prius Input
Summing system. The
traction motor operates
through a planetary rather
than a fixed gear set.
� Increased torque range of low
motor power requirements
� No Torque Converter → E-
CVT launch
� Efficient power ratios
� Minimal speed limitations
MG1MG2
MG1MG2
RX400h & Highlander
HS250h & Camry
Compound Split Hybrid SystemMotor Power Ratio
Compound Split Hybrid Systems
-8
-6
-4
-2
0
2
4
6
8
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Po
wer R
ati
o,
P M
oto
r/P
En
gin
e
PM1/Peng
PM2/Peng
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Planetary Ratio, NSun/NRing
Coupling P
oin
t
Expected overall ratio spread ≈0.7:1 15:1
Coupling Point
( )
+⋅−=
1
11 1RingSun
Ring
Engine
MG
NNRatio
N
P
P
Compound Split Hybrid SystemMotor Speed Gains
HS250h & Camry
-25
-20
-15
-10
-5
0
5
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Mo
tor S
peed
Ga
in
MG1
MG2
MG2 limits speed when the torque ratio is less than 0.6:1
Compound Split Hybrid SystemMotor Speed Gains
-30
-20
-10
0
10
20
30
40
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Moto
r S
peed G
ain
MG1
MG2
MG2 limits speed when the torque ratio is less than 1:1
RX400h & Highlander
Compound Split Hybrid System
MG1 MG2
CBLowCBHigh
To engage the low gear range, Toyota opens the conventional
planetary gearset’s brake 1 and locks brake 2, resulting in a
reduction gear ratio of 3.900. For high gear, brake 1 is locked
and brake two is open, with a reduction gear ratio of 1.900.
(The Rx 400h uses a fixed reduction ratio of 2.478.) The
result is that the motor in the 450h acts as a single high-
torque and high-speed motor. Motor size can then be reduced
enough to fit the transmission in the GS450h floor pan tunnel
� Hybrid Vehicle Applications
� Lexus GS450h, LS600h
� Features
� Low range is similar to the
RX400h system
� No Torque Converter → E-
CVT launch
� Increased complexity, with
added efficiency over Input
and other compound split
systems
� Efficient power ratios
� Reduction Ratios
• Low Gear 3.9:1
• High Gear 1.9:1
Compound Split Hybrid SystemMotor Power Ratio – Low Range
GS450h & LS600h in Low Range
-8
-6
-4
-2
0
2
4
6
8
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Pow
er R
atio, P
Moto
r/P
Engin
e
PM1/Peng
PM2/Peng
( )1
11 1RingSun
Ring
Engine
MG
NNRatio
N
P
P
+−=
Coupling Point
Expected overall ratio spread ≈
0.7:1
15:1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Planetary Ratio: NSun/NRing
Coupling P
oin
t
1.9:1 3.9:1Low Range
Compound Split Hybrid SystemMotor Power Ratio – High Range
GS450h & LS600h in High Range
-6
-4
-2
0
2
4
6
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Po
wer
Ra
tio
, P
Mo
tor/P
En
gin
e
PM1/Peng
PM2/Peng
−=
2
32 11
Ring
Ring
Engine
MG
N
N
RatioP
P
1.9:10.7:1
High Range
Compound Split Hybrid SystemClutch Slip Speed Gain
0
1
10
100
03691215
Transmission Torque Ratio
Clu
tch
Sli
p S
pee
d G
ain
CBLow
CBHigh
0.7
GS450h & LS600h
Engineω⋅142.2
Compound Split Hybrid SystemMotor Speed Gains
-20
-15
-10
-5
0
5
10
15
20
25
30
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Mo
tor
Sp
eed
Gain
MG1
MG2-Low
MG2-High
MG2 limits speed in;
- low range when the torque ratio is less than 1.0
- high range when the torque ratio is less than 0.5
GS450h & LS600h
xx4th Gear
xx3rd Gear
xEVT2
xx2nd Gear
xx1st Gear
xEVT1
CB4
C234, EVT2
C13
CB12R,
EVT1
Note: Gear-to-gear shifts are possible, however, the typical
shift sequence is to go from gear-to-EVT, then to the next gear.
Second gear is the hand-off from EVT1 to EVT2.
C234, EVT2
MG2MG1
CB4
C13
CB12R, EVT1
Two-Mode Hybrid System� Hybrid Vehicle Applications
� Allison EV Drive
� BMW X6
� Chrysler Aspen, Durango
� GM Tahoe, Yukon
� Mercedes ML450
� Features
� Electric & Mechanical Oil Pump
� Damper (GM only)
� No Torque Converter → E-CVT1 launch
� Synchronized Shifting
� Clutch-to-Clutch Powershift (BMW only)
� Race Start (BMW & Mercedes)
� Significant motor power requirements at high torque ratios
� High parasitic losses in all ratios, except at or near 3rd gear (Direct ratio)
Two-Mode Hybrid SystemE-CVT Low Range Motor Power Ratio
E-CVT Low Range (Mode 1)
-150
-100
-50
0
50
100
150
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Pow
er R
ati
o, P
Mo
tor/P
En
gin
e
MG1
MG2
Mode 1 Coupling Point Sensitivity
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Planetary Sun-to-Ring Gear Ratio
Coupling P
oin
t
NSun1/NRing1
NSun2/NRing2
NSun3/NRing3
Coupling Point
Expected overall ratio spread ≈
1.8:1
15:1
( )
( )
( )
++
−
−⋅=
K
NN
NN
Ratio
N
NNN
CCRatio
Power
Power RS
SRS
SRSOut
MG 33
321
121
211
EVT1
Two-Mode Hybrid SystemE-CVT High Range Motor Power Ratio
E-CVT High Range (Mode 2)
-6
-4
-2
0
2
4
6
0 2 4 6 8 10 12 14 16
Transmission Torque Ratio
Po
wer
Rati
o, P
Mo
tor/P
En
gin
e
MG1
MG2
Mode 2 Coupling Sensitivity
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Planetary Ratio, Sun-to-Ring Gear
Coupling P
oin
t NSun1/NRing1
NSun2/NRing2
NSun3/NRing3
NSun1/NRing1
NSun2/NRing2
NSun3/NRing3
Coupling Points
0.7:1
( ) ( )
( )
+
+−⋅⋅
−−=
KN
KNRatioK
Ratio
NN
N
N
P
P
Ring
SunSunRing
Sun
Ring
In
MG
2
112
1
22
Node 1
Node 2
1.8:1
Released Clutch Slip Speeds
0
1
2
3
4
5
6
7
8
EVT-1 EVT-1 1st Gear EVT-1 2nd Gear EVT-1 3rd Gear EVT-2 EVT-2 EVT-2 4th Gear EVT-2
Transmission Mode & Gear
Clu
tch S
lip
Sp
eed
Gain
0
2
4
6
8
10
12
14
16
Tra
nsm
issi
on T
orq
ue
Rati
o
CB12R
C13
CB234
CB4
Ratio
Engine Speed
Two-Mode Hybrid SystemClutch Slip Speed Gains
Torque Ratio
Two-Mode Hybrid SystemMotor Speed Gains
Motor Speeds Across Torque Range
-10
-5
0
5
10
15
20
EVT-1 1st Gear 2nd Gear EVT-2 EVT-1 3rd Gear EVT-2 4th Gear EVT-2
E-CVT Mode & Gear Ratio
Tra
nsm
issi
on
Torq
ue
Rati
o
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Moto
r S
pee
d G
ain
Ratio
MG1
MG2
Engine Speed
~ Motor Speed Limit
The EVT1 to EVT2 hand-off occurs at 2nd
gear, therefore, this EVT1 ratio will not
occur.