Authors: - Sebastian Hämmerle, Vorarlberg Univ. of Appl. Sc. Austria - Marco Kessler, Modelon GmbH Germany - Markus Andres, Modelon GmbH Germany The work introduces a new concept of modeling the overall control unit of hybrid electric vehicles in Modelica. The study focuses on a structure which can simulate substantially different vehicle concepts without changing the structure of the control unit. Based on this universal implementation different scenarios can be simulated rapidly and consequently cheaply, including fundamentally different drive trains ranging from conventional to purely electrical including hybrid versions. Full text at: http://www.ep.liu.se/ecp/096/008/ecp14096008.pdf

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Utilizing Object-Oriented Modeling Techniques
for Composition of Operational Strategies for
Electrified Vehicles
Sebastian Hämmerle1 Markus Andres2 Marco Keßler2
1Vorarlberg Univ. of Appl. Sc.
Austria
2Modelon GmbH
Germany
10th International Modelica Conference
Hämmerle, Andres, Keßler Modelica 2014 1 / 26

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Electrified Powertrain Concepts (EPoC)
The results shown in this presentation were developed within
the EPoC project which is funded by the Eurostars Programme.
The outcome of the project is a commercially distributed
Modelica library: The Electrified Powertrains Library (EPTL)
Hämmerle, Andres, Keßler Modelica 2014 2 / 26

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High variety of HEVs
• Various kinds of topologies
Optional
G
+-
12V
AB
CD
-
-+
+
Optional
AC-DCDC-DC
AC-DC
DC
AC
Ω
Ω
Ω
+-
HV
Series Hybrid
Optional
+-
HV
AB
CD
-
-+
+
Optional
AC-DC
DC
AC
Ω
Ω
Ω
DC-DC
+-
12V
Parallel Hybrid
Optional
AB
CD
-
-+
+
G
+-
HV
Optional
DC-DC
AC-DC
DC
AC
AC-DC
Ω
Ω
Ω
+-
12V
Power-split Hybrid
Hämmerle, Andres, Keßler Modelica 2014 3 / 26

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High variety of HEVs
• Different hybridization levels and corresponding drive
modes
Hämmerle, Andres, Keßler Modelica 2014 4 / 26

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Common implementation for Control Units
In most cases a specific control unit for one configuration is
implemented, which:
+ is relatively quick achieved,
+ is well suited for one specific case,
- BUT requires an adoption of the control unit or even a new
control unit if the topology changes.
Hämmerle, Andres, Keßler Modelica 2014 5 / 26

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Goal: General control unit implementation
The aim was to:
• model a control unit covering all topologies,
• provide a frame work with fully working templates,
• allow easy customization and extendibility.
Hämmerle, Andres, Keßler Modelica 2014 6 / 26

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Dependencies of the control unit
The control unit gets signals from the driver via the brake and
acceleration pedals and it interacts directly with the vehicle.
Driving Cycle Driver
Drive
Environment
Control
Unit
Vehicle Auxiliary Unit Vehicle
Environment Environment
Control Unit
Hämmerle, Andres, Keßler Modelica 2014 7 / 26

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Model of the entire system
To test the control unit the vehicle consisting of drive line and
auxiliary units, a driver and the environment were modelled.
Control Blocks Drive Environment
Vehicle Environment
1 3 5
2 4
Driver
v
t
Cycle
EnvironmentD-Line
data
RR
A-Unit
0 1 0 1
1 0 1 0
0 1 0 1
Control-Unit
Hämmerle, Andres, Keßler Modelica 2014 8 / 26

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Structure of the universal control unit
Two level structure:
L1 driving mode
determination
L2 component
controllers which
act depending on
the current drive
mode
Primary Control Level
Secondary Control Level
0 1 0 1
1 0 1 0
0 1 0 1
ECU
0 1 0 1
1 0 1 0
0 1 0 1
GBCU
0 1 0 1
1 0 1 0
0 1 0 1
CCU
0 1 0 1
1 0 1 0
0 1 0 1
BCU
Signals
0 1 0 1
1 0 1 0
0 1 0 1
HCU
0 1 0 1
1 0 1 0
0 1 0 1
EDCU
data
Results
Hämmerle, Andres, Keßler Modelica 2014 9 / 26

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Primary layer of the hybrid control unit (HCU)
• control strategy
block determines
drive mode
depending on
vehicle states and
driver inputs
• state graph
ensures that only
one mode is
active
Control Strategy
0 1 0 1
1 0 1 0
0 1 0 1
Controller
rising
driveModi
OR
standStill
from BUS
standStillEngine
from BUS
electricDriving
from BUS
braking
from BUS
regenerativeBraking
from BUS
boosting
from BUS
shiftingOperationPoint
from BUS
conventionalDriving
from BUS
DriveModi
to BUS
data
rising
rising
rising
rising
rising
rising
rising
Hämmerle, Andres, Keßler Modelica 2014 10 / 26

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Considered Drive Modes
In the current implementation the following drive modes are
included:
1 Standstill engine off
2 Standstill engine on
3 Electric driving
4 Friction braking
5 Regenerative braking
6 Boosting
7 Shifting of the Operation Point
8 Conventional Driving
Hämmerle, Andres, Keßler Modelica 2014 11 / 26

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Framework for the control strategies
• one drive mode
controller for
each drive mode
• modes can be
deactivated with
boolean
parameters
• adaptable control
strategy
templates for
activation of the
drive modes
Control Strategy
0 1 0 1
1 0 1 0
0 1 0 1
Controller
Hämmerle, Andres, Keßler Modelica 2014 12 / 26

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Framework for the control strategies
• one drive mode
controller for
each drive mode
• modes can be
deactivated with
boolean
parameters
• adaptable control
strategy
templates for
activation of the
drive modes
Control Strategy
0 1 0 1
1 0 1 0
0 1 0 1
Controller
Hämmerle, Andres, Keßler Modelica 2014 13 / 26

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Exemplary control strategy
The drive mode stand still gets active when it is enabled, the
vehicle speed is zero and the SOC of the battery allows it.
StandStill =
if StartStop == true and
bus.brakePedal > 0.95 and
bus.VehicleSpeed <= vmin and
bus.SOC >= SOCmin
then true
else false;
StandStillEngine =
if bus.VehicleSpeed <= vmin and
bus.brakePedal > 0.95 and
(bus.SOC < SOCmin or StartStop ==
false)
then true
else false;
Hämmerle, Andres, Keßler Modelica 2014 14 / 26

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Implementation of the Control Strategy within the HCU
• own control strategies are
easy to implemented by
changing the template code
• new driving modes are
added by including new
drive mode controllers
Hämmerle, Andres, Keßler Modelica 2014 15 / 26

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Driving mode selection via state graphs
• parallel loop
for each
driving mode
• an activated
driving mode
deactivates all
others
entry
RegenerativeBrakingON
StandStillON
StandStillEngineON
ElectricDrivingON
BrakingON
BoostingON
ShiftingOperationPointON
DrivingMode
ConventionelDrivingON
RegenerativeBrakingOFF
StandStillOFF
StandStillEngineOFF
ElectricDrivingOFF
BrakingOFF
BoostingOFF
ShiftingOperationPointOFF
ConventionelDrivingOFF
1 = StandStill
2 = StandStillEngine
3 = ElectricDriving
4 = Braking
5 = RegenerativeBraking
6 = Boosting
7 = ShiftingOperationPoint
8 = ConventionalDriving
multiSwitch
{1234
5678}
driveModi
Hämmerle, Andres, Keßler Modelica 2014 16 / 26

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Secondary layer of the hybrid control unit (HCU)
Primary Control Level
Secondary Control Level
0 1 0 1
1 0 1 0
0 1 0 1
ECU
0 1 0 1
1 0 1 0
0 1 0 1
GBCU
0 1 0 1
1 0 1 0
0 1 0 1
CCU
0 1 0 1
1 0 1 0
0 1 0 1
BCU
Signals
0 1 0 1
1 0 1 0
0 1 0 1
HCU
0 1 0 1
1 0 1 0
0 1 0 1
EDCU
data
Results
Hämmerle, Andres, Keßler Modelica 2014 17 / 26

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Secondary layer of the hybrid control unit (HCU)
Primary Control Level
Secondary Control Level
0 1 0 1
1 0 1 0
0 1 0 1
ECU
0 1 0 1
1 0 1 0
0 1 0 1
GBCU
0 1 0 1
1 0 1 0
0 1 0 1
CCU
0 1 0 1
1 0 1 0
0 1 0 1
BCU
Signals
0 1 0 1
1 0 1 0
0 1 0 1
HCU
0 1 0 1
1 0 1 0
0 1 0 1
EDCU
data
Results
Hämmerle, Andres, Keßler Modelica 2014 18 / 26

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ECU - Controller for the combustion engine
• parallel branches are
activated drive mode
depended
• adoptable template
strategies for
shifting the
operation point
(SOP), boosting (BST)
etc. are provided
Shifting the Operation Point
Boosting
Conventional Driving
During Shift
Start/Stop/Idle
CE
modifiedAcceleratorPedalCE
from BUS
accelearationCE
to BUS
=
6
driveModi
from BUS
B
R
=
7
B
R
SOP
=
8
B
R
BST
DST
k
limiter
uMax=1
limiter
data
1 = StandStill
2 = StandStillEngine
3 = ElectricDriving
4 = Braking
5 = RegenerativeBraking
6 = Boosting
7 = ShiftingOperationPoint
8 = ConventionalDriving
Hämmerle, Andres, Keßler Modelica 2014 19 / 26

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Simulations with BMW i8
To test a parallel hybrid structure the setup of the BMW i8 is
used. Simulations as a hybrid electric and a conventional vehicle
can be performed by enabling the specific drive modes in the
parameter set.
A B
CD
-
- +
+
Hämmerle, Andres, Keßler Modelica 2014 20 / 26

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BMW i8 simulated as a hybrid electric vehicle
0
0
10
20
30
Vehiclespeed[m/s]
0 200 400 600 800 1000 1200
2
4
6
8
Drivemodes
Time [s]
1 Standstill engine off
2 Standstill engine on
3 Electric driving
4 Friction braking
5 Regenerative braking
6 Boosting
7 Shifting of the Operation Point
8 Conventional Driving
Hämmerle, Andres, Keßler Modelica 2014 21 / 26

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BMW i8 simulated as a conventional vehicle
0
10
20
30
Vehiclespeed[m/s]
0 200 400 600 800 1000 1200
2
4
6
8
Drivemodes
Time [s]
1 Standstill engine off
2 Standstill engine on
3 Electric driving
4 Friction braking
5 Regenerative braking
6 Boosting
7 Shifting of the Operation Point
8 Conventional Driving
Hämmerle, Andres, Keßler Modelica 2014 22 / 26

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Simulations with BMW i3
To test a fully electrical vehicle the setup of the BMW i3 is used
with the same control unit as for the BMW i8 - only the drive
modes are changed by setting boolean variables.
A B
CD
-
- +
+
Optional
Hämmerle, Andres, Keßler Modelica 2014 23 / 26

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BMW i3 simulation results
0
10
20
30
0 250 500 750 1000 1250 1500 1750
0
1
3
5
Time [s]
Vehiclespeed[m/s]Drivingmodes
1 Standstill engine off
2 Standstill engine on
3 Electric driving
4 Friction braking
5 Regenerative braking
6 Boosting
7 Shifting of the Operation Point
8 Conventional Driving
Hämmerle, Andres, Keßler Modelica 2014 24 / 26

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Conclusion
With the presented control unit:
+ simulations of conventional, electric, series hybrid and
parallel hybrid vehicles are possible
+ a fully working template is provided
+ existing driving modes can be altered or deactivated
+ new driving modes can be added
- support for power split hybrids is missing
- new driving modes require a new loop in the state graph
model
Hämmerle, Andres, Keßler Modelica 2014 25 / 26

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Thanks!
Hämmerle, Andres, Keßler Modelica 2014 26 / 26