By the strict discussions regarding energy saving and the goal to reduce CO2, there is a keen demand for light designed automotive structures and the development of electric vehicles. To achieve these goals, a comprehensive method for urban vehicle concepts with electric powertrain and their necessary vehicle structures is presented. The dimensions and packaging of the presented vehicle is based on demands of a future urban vehicle with space for four occupants including baggage, steerable front system wheels and a rear axle including an electric powertrain. In the geometric design phase of the method the vehicle design space is analyzed for global load path with the help of topology optimization (OptiStruct). The load paths are then clustered into different shapes. Concepts for new body in white structures are derived from the results. Speakers Marco Münster, Research Assistant, DLR Institute of Vehicle Concepts

1. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 1
Development of body structure concepts for electric vehicles
using the topology optimization for global load pathfinding
2015 European Altair Technology Conference
September 29 – October 1 Paris France
Dipl.-Ing. Marco Münster
Dipl.-Ing. Michael Schäffer
Prof. Dr.-Ing. Horst E. Friedrich
DLR Institute of Vehicle Concepts

2. • DLR Institut of Vehicle Concepts and Project Next Generation Car (NGC)
• Challenges and motivation for new vehicle concepts
• Holistic development Methodology for vehicle concepts and body structures
• Topology optimization for global loadpath finding
• Example of body structure development with the method of global loadpath
finding
• Summary and Outlook
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 2
Agenda

3. DLR.de • Chart 3
DLR – German Aerospace Center
DLR's mission:
• Exploration of the Earth and the solar system
• Research aimed at protecting the environment
• dDevelopment of environmentally-friendly technologies
to promote mobility, communication and security.
7.700 employees are working at 32 research institutes and
facilities in n 9 locations and  7 branch offices.
SPACE AERONAUTICS TRANSPORT ENERGY
SECURITY
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015

4. DLR.de • Chart 4
DLR – German Aerospace Center
Institute of Vehicle Concepts:
SPACE AERONAUTICS TRANSPORT ENERGY
SECURITY
Vehicle systems and
technology assessment
Vehicle energy
concepts
Alternative energy
conversion
Lightweight and hybrid
construction
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015

5. • Technologies, methods and tools for integrated
development of road vehicles of tomorrow
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 5
DLR Next Generation Car (NGC)
Source: DLR
Source: DLR
Source: DLR
Source: DLR
Source: DLR
Source: DLR
Source: DLR
Source: DLR
Source: Stuttgarter Symposium 2015 Documentation Volume 2; Dipl.-Ing. Gundolf Kopp, Dipl.-Ing. Simon Brückmann, Dipl.-Ing. Michael Kriescher, Dr. Martin Ruff, Prof. Dr.-Ing. Horst E. Friedrich; DLR-FK
Source: DLR

6. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 6
Source: Auto Motor Sport
Challenge and motivation
Packaging conventional- and electric vehicle

7. • remove: combustion engine, exhaust system, transmission …
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 7
Source: Auto Motor Sport
Challenge and motivation
Packaging conventional- and electric vehicle

8. • remove: combustion engine, exhaust system, transmission …
• add: battery, electric motor, power electronics …
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 8
Source: Mahle
Source: Getrag Source: Brusa
Source: Febasto
Conclusion  Development of new vehicle concepts and components
Source: Nissan
Source: Auto Motor Sport
Challenge and motivation
Packaging conventional- and electric vehicle

9. Holistic development Methodology for vehicle concepts and body structures
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 9
Phase 2: Body structure development phase
Phase 1: Concept phase
Mobility requirements/
Market/Customer
Vehicle conception
geometrically/simulative
Vehicle dimension/
Package
Source: DLR (Münster; Gaydon 2013)
Source: DLR (Münster; Gaydon 2013)
Design/Parametric CAD-
vehicle space model
Package study
Source: DLR (Münster; Gaydon 2013)
State of the art comparison
Topology optimization for
global load pathfinding
Lastpfadanalyse
Material selection, MDO
optimization with concept
body structure
Prototypical
validation
Overall Rating
Vehicle concept parameters
(Number of seats, range,
Application area …)
Vehicle conception
(geometrically and simulative)
Parametric CAD-vehicle space model
(tunnel, double bottom, B-pillar …)
Load path analysisEngineering designOptimizationComponent validationConcept review
+
Selection of Basic
form variant and
package
+
V1
V2
Concept body structure
V1 tunnel + profile + shell

10. Holistic development Methodology for vehicle concepts and body structures
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 10
Phase 2: Body structure development phase
Phase 1: Concept phase
Mobility requirements/
Market/Customer
Vehicle conception
geometrically/simulative
Vehicle dimension/
Package
Source: DLR (Münster; Gaydon 2013)
Source: DLR (Münster; Gaydon 2013)
Design/Parametric CAD-
vehicle space model
Package study
Source: DLR (Münster; Gaydon 2013)
State of the art comparison
Topology optimization for
global load pathfinding
Lastpfadanalyse
Material selection, MDO
optimization with concept
body structure
Prototypical
validation
Overall Rating
Vehicle concept parameters
(Number of seats, range,
Application area …)
Vehicle conception
(geometrically and simulative)
Parametric CAD-vehicle space model
(tunnel, double bottom, B-pillar …)
Load path analysisEngineering designOptimizationComponent validationConcept review
+
Selection of Basic
form variant and
package
+
V1
V2
Concept body structure
V1 tunnel + profile + shell

11. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 11
Parametric space model for topology optimization
x
y
z
Variable parameters:
• dimension of the tunnel
• double floor
• seat crossmember
• …
3 doors hatch
with tunnel,
double bottom,
seat crossmembers
5 doors hatch
with tunnel,
double bottom,
seat crossmembers
5 doors hatch
double bottom

12. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 12
Topology optimization on space model
Boundary conditions and load cases
1. Tool: Topology optimization on space model
Defining boundary conditions and load cases
Boundary conditions9 crash load cases 3 static load cases
xy
z
x
y
z
McPherson Strut
Twist-beam Rear Axle

13. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 13
Topology optimization on space model
Boundary conditions and load cases
1. Tool: Topology optimization on space model
x
y
z
Defining boundary conditions and load cases
Masses of body structure and
components
+
x
y
z
Force introduction surfaces as rigid elements
100%, 40%, 25%
Front Crash
100% Rear
Crash
Pole Crash IIHS Side Crash
Roof Crush
Mass Points

14. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 14
Topology optimization on space model
Boundary conditions and load cases
1. Tool: Topology optimization on space model
Topology optimization boundary conditions
Equivalent Static Inertia Relief
Loads for Crash:
Static Load Cases: Single-Point Constraint
at chassis points
Elements: 1.2 Mio C-TETRA
Elements Objective: Weighted Compliance
Constrains: Massfraction
x
y
z
x
y
z
100%, 40%, 25%
Front Crash
100% Rear
Crash
Pole Crash IIHS Side Crash
Roof Crush

15. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 15
Topology optimization on space model
Weighted compliance
1. Tool: Topology optimization on space model
Weighted compliance
loadcase 1: weighted with 1
loadcase 2: weighted with 1
loadcase 1: weighted compl. =1
loadcase 2: weighted compl. =1

16. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 16
Topology optimization in different space model variants
V1
V2
1. Tool: Topology optimization on space model
Topology optimization in different space model variants
xy
z
xy
z

17. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 17
Topology optimization levels
1. Tool: Topology optimization on space model
unlimited space model
(without components)
limited space model
(space for major package components)
limited space model
(space for major package components)
Partially erased space model of
dynamic loaded body areas
Space model Package
I)
II)
III)
Topology optimization levels

18. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 18
Load path derivation rules
- unbranched structures  profile
- flat area with medium-sized  shell/sandwich
element densities
- branched structures  node element
1. Tool: Topology optimization on space model
Load path derivation rules

19. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 19
Analysis of state of the art body in white, requirements
and boundary conditions, body designs
2. Tool: Analysis of state of the art body in white, requirements
and boundary conditions, body designs
Source: Audi
Source:: Audi
Source: BMW
Source: Tesla
Source: Honda
Source: Renault
1. Tool: Topology optimization on space model

20. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 20
Load path interpretation to body structures
Space model V1 Package Topology optimization
Source: DLR (Münster; Gaydon 2013) Source: DLR (Münster) Source: DLR (Münster)
1
2
3
x
y
z
x
y
State of the art BIW
Source: Audi
V1 Tunnel
• Topology optimization (green) in the vehicle floor with the load path floor cross
(1), two cross-members (2) and longitudinal beams in the center tunnel (3)
Load path derivation rules

21. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 21
Final body in white structure
Space model V1 Package Topology optimization
Source: DLR (Münster; Gaydon 2013) Source: DLR (Münster) Source: DLR (Münster)
State of the art BIW
Source: Audi
x
y
z
V1 Tunnel
Load path derivation rules
x
y
z

22. > Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 22
Simulation of final body in white structure
• 1st Eigenfrequency trimmed
body 34,4 Hz
Space model V1 Package Topology optimization
Source: DLR (Münster; Gaydon 2013) Source: DLR (Münster) Source: DLR (Münster)
State of the art BIW
Source: Audi
1st Eigenfrequency trimmed body [Hz]
StateoftheartBIW[-]
Body in white DLR
V1 Tunnel

23. Summary:
• Holistic development Methodology for vehicle concepts and body structures
• Topology optimization for global loadpath finding
• Topology optimization levels
• Topology optimization in different space model variants
• Example of global loadpath finding and a body structure with Variant 1
Outlook:
• Development of a second body structure
• Numerical multidisciplinary design optimization of the concepts
• Building a component of the body and test on the in-house component crash
test facility
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding > Marco Münster • 2015DLR.de • Chart 23
Summary and Outlook
Space model V1 Package Topology optimization
Source: DLR (Münster; Gaydon 2013) Source: DLR (Münster)
Body in white

24. Thank you for your attention
Marco Münster
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
German Aerospace Center
Institute of Vehicle Concepts | Lightweight and Hybrid Design Methods | Pfaffenwaldring 38-40 | 70569 Stuttgart | Germany
Dipl.-Ing. Marco Münster
Phone +49 711 6862-707 | Fax +49 711 6862-258 | marco.muenster@dlr.de
www.DLR.de/fk/en
> Development of body structure concepts for electric vehicles using the topology optimization for global load pathfinding> Marco Münster • 2015DLR.de • Chart 24
Source: DLR (Münster; Gaydon 2013)
Source: DLR (Münster; Gaydon 2013) Source: DLR (Münster; Gaydon 2013)
+
+
V1
V2