Evaluation Of 2 Motor Hybrid Architectures

Evaluation of 2-Motor
Hybrid Architectures

James Potter
ZF 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

Input Summing Hybrid System
MG2 MG1

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 System Cross-Over Point

Motor Power Ratio 1.00

0.90

0.80

0.70

Coupling Point
0.60

0.50

0.40

0.30

Prius & Escape
PowerSplit Hybrid System
0.20

0.10

0.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

Coupling Point Ratio: Sun/Ring Gear Teeth

3.0
Motor/PEngine

2.5
2.0
1.5
1.0
0.5 PM1/Peng
Power Ratio, P

0.0
-0.5 PM2/Peng
-1.0
-1.5
-2.0
-2.5
-3.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 P
4.0MG 1 = 1 −
4.5 5.0 N Ring 1

P Engine Ratio (N Sun + N Ring )
1
Transmission Torque Ratio

Expected overall ratio spread

≈
0.7:1 15:1

Input Summing Hybrid System
Motor Speed Gains

Prius & Escape 15

10

5

Motor Speed Gain
0
MG1
-5
MG2
-10

-15

-20

-25
16 14 12 10 8 6 4 2 0

MG1 limits speed when; Note: Assumes a maximum motor speed of 15,000 rpm
Ratio < 0.4 and
Ratio > 4.0

Output Split Hybrid System
MG1 MG2

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 System 2.0

1.8

Motor Power Ratio 1.6

1.4

Coupling Point
1.2

1.0

0.8

0.6

0.4

Output Split Hybrid System 0.2

0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Planetary Ratio, N Sun/N Ring

Coupling Point
5
Motor/PEngine

3

1
PM1/Peng
Power Ratio, P

PM2/Peng
-1

-3

-5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Power M 2 = 5.0− N Ring ⋅ Ratio 
4.5 
1 
Power Engine 
 ( N Sun + N Ring ) 

Ratio

0.7:1
≈ 15:1

Output Split Hybrid System
Motor Speed Gains

35

30

25

Motor Speed Gain
20

MG1
15
MG2

10

5

0

-5
16 14 12 10 8 6 4 2 0

MG2 limits speed when the torque ratio is less than 0.6

Compound Split Hybrid System
MG2 MG1

Lexus HS250h & RX400h
Toyota Camry & Highlander
Features
Similar to the Prius Input HS250h & Camry
Summing system. The
traction motor operates
through a planetary rather
than a fixed gear set. MG2 MG1
Increased torque range of low
motor power requirements
No Torque Converter → E-
CVT launch
Efficient power ratios
RX400h & Highlander
Minimal speed limitations

Motor Power Ratio
Compound Split Hybrid Systems
Coupling Point 1.0

8 0.9

0.8

0.7

Coupling Point
6 0.6

0.5

0.4
Power Ratio, P Motor/P Engine

0.3
4 0.2

0.1

0.0

2 0.0 0.1 0.2 0.3 0.4 0.5
Plane tary Ratio, NSun/NRing
0.6 0.7 0.8 0.9

PM1/Peng
0
PM2/Peng
-2

-4

-6

-8  
PMG 1 N Ring 1
= 1 −
0 2 4 6 8 10 12 PEngine 14


16N + N
Ratio ⋅ ( Sun Ring )1 



≈
0.7:1 15:1

Motor Speed Gains
5

0

-5
Motor Speed Gain

MG1
-10
MG2

-15

-20

-25
0 2 4 6 8 10 12 14 16

HS250h & Camry MG2 limits speed when the torque ratio is less than 0.6:1

Motor Speed Gains

40

30

20
otor Speed Gain

10
MG1
MG2
0
M

0 2 4 6 8 10 12 14 16
-10

-20

-30

MG2 limits speed when the torque ratio is less than 1:1
RX400h & Highlander


Hybrid Vehicle Applications MG1 MG2

Lexus GS450h, LS600h
Features
Low range is similar to the
CBLow
RX400h system CBHigh
No Torque Converter → E-
CVT launch
Increased complexity, with
added efficiency over Input To engage the low gear range, Toyota opens the conventional
and other compound split planetary gearset’s brake 1 and locks brake 2, resulting in a
systems reduction gear ratio of 3.900. For high gear, brake 1 is locked
Efficient power ratios 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
Reduction Ratios result is that the motor in the 450h acts as a single high-
• Low Gear 3.9:1 torque and high-speed motor. Motor size can then be reduced
• High Gear 1.9:1
enough to fit the transmission in the GS450h floor pan tunnel

Motor Power Ratio – Low Range
Coupling Point

1.0

GS450h & LS600h in Low Range 0.9

0.8

0.7

Coupling Point
8 0.6

0.5

0.4

6 0.3

0.2
Power Ratio, PMotor/P Engine

0.1
4 0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Plane tary Ratio: NSun /NRing

2
PM1/Peng
0
PM2/Peng
0 2 4 6 8 10 12 14 16
-2

-4

-6

-8
P MG 1 N Ring 1
Transmission Torque Ratio = 1−
P Engine Ratio (N Sun + N Ring )1

Low Range
1.9:1 3.9:1
≈
15:1
0.7:1

Motor Power Ratio – High Range
GS450h & LS600h in High Range

6

4

2

PM1/Peng
0
PM2/Peng
0 2 4 6 8 10 12 14 16

-2

-4

-6
PMG 2 1  N Ring 3 
= 1 − 
PEngine Ratio 
 N Ring 2 


High Range
0.7:1 1.9:1

Clutch Slip Speed Gain
100

10

CBLow
CBHigh
2 . 142 ⋅ ω Engine
1

0
15 12 9 6 3 0.7 0

GS450h & LS600h

Motor Speed Gains
30

25

20

15
Motor Speed Gain

10
MG1
5 MG2-Low
MG2-High
0
0 2 4 6 8 10 12 14 16
-5

-10
MG2 limits speed in;
-15 - low range when the torque ratio is less than 1.0
- high range when the torque ratio is less than 0.5
-20

GS450h & LS600h

Two-Mode Hybrid System
MG1 MG2
CB12R, EVT1
Allison EV Drive CB4

C13
BMW X6
Chrysler Aspen, Durango C234, EVT2
GM Tahoe, Yukon
Mercedes ML450
Features
Electric & Mechanical Oil Pump
CB12R, C13 C234, EVT2 CB4
Damper (GM only) EVT1
No Torque Converter → E-CVT1 EVT1 x
launch
1st Gear x x
Synchronized Shifting
2nd Gear x x
Clutch-to-Clutch Powershift (BMW
only) EVT2 x

Race Start (BMW & Mercedes) 3rd Gear x x
Significant motor power requirements 4th Gear x x
at high torque ratios
Note: Gear-to-gear shifts are possible, however, the typical
High parasitic losses in all ratios, shift sequence is to go from gear-to-EVT, then to the next gear.
except at or near 3rd gear (Direct ratio) Second gear is the hand-off from EVT1 to EVT2.

E-CVT Low Range Motor Power Ratio
E-CVT Low Range (Mode 1)
Coupling Point
150 Mode 1 Coupling Point Sensitivity

4.00

3.50

3.00
100

Coupling Point
2.50
NSun1/NRing1

2.00 NSun2/NRing2
NSun3/NRing3
1.50

50 1.00

0.50

0.00
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Plane tary Sun-to-Ring Ge ar Ratio
0

-50 MG1
  N S1 N R2 N S3   MG2
 + 
PowerMG1
=
(Ratio ⋅ C1 − C 2 )   Ratio (N S 3 + N R 3 ) 
-100
PowerOut N S1 (N R 2 − N S1 )  K 
 

 

-150
0 2 4 6 8 10 12 14 16

EVT1 Expected overall ratio spread
≈
15:1
1.8:1

E-CVT High Range Motor Power Ratio
E-CVT High Range (Mode 2)
Mode 2 Coupling Sensitivity
Coupling Points
4.50

6 4.00
Node 2
3.50

3.00 NSun1/NRing1

Coupling Point
NSun2/NRing2
2.50 NSun3/NRing3

4 2.00
NSun1/NRing1
NSun2/NRing2
Power Ratio, P Motor /P Engine

1.50 NSun3/NRing3

1.00

0.50 Node 1
2 0.00
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

0

MG1
-2
MG2

-4
PMG 2  N Ring 2 (N Ring 2 − N Sun1 )  K ⋅ Ratio − ( N Sun1 + K ) 
⋅
PIn
=
 N Sun1
−
Ratio  
 (N Ring 2 + K )  

-6
0 2 4 6 8 10 12 14 16

0.7:1 1.8:1

Clutch Slip Speed Gains

Released Clutch Slip Speeds
Torque Ratio
8 16

7 14

6 12

5 10 CB12R
C13
4 8 CB234
CB4
3 6 Ratio

2 4

1
Engine Speed 2

0 0
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

Motor Speed Gains

Motor Speeds Across Torque Range

20 4.5

4.0
15

~ Motor Speed Limit 3.5

Motor Speed Gain
10 3.0
Ratio
2.5 MG1
5
2.0 MG2

0 1.5

Engine Speed 1.0
-5
0.5

-10 0.0
EVT-1 1st Gear 2nd Gear EVT-2 EVT-1 3rd Gear EVT-2 4th Gear EVT-2
E-CVT Mode & Gear Ratio

The EVT1 to EVT2 hand-off occurs at 2nd
gear, therefore, this EVT1 ratio will not
occur.

Evaluation Of 2 Motor Hybrid Architectures

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