Tech Briefs Magazine - October 2023 - 24

Generative Engineering
Vehicle
requirements
Vehicle
(xEV)
Objectives:
* Energy consumption
[l/km]
* CO2
emission
[kg/km]
* Costs [€]
PWT
requirements
PWT
system
* PWT architecture
* PWT component sizing &
control
cooling subsystem (Figure 1). The design
process commences with the definition
of the vehicle's requirements, encompassing
performance and profile
specifications,
straints like packaging limitations. These
requirements are then applied to the
powertrain system level, where design
engineers
face decisions
Cooling
requirements
Cooling
subsystem
* Cooling architecture
* Cooling component
sizing & control
Figure 1: xEV design process based on an engineering system approach. (Image: Dessia)
exploring
architectures and concepts
that fulfill requirements, avoiding fixation
on a single design and performing
parameter sensitivity analysis. Such approach
reduces the number of iterations
by utilizing computer tools to automate
tasks and conduct detailed design phases
for promising candidates.
A New Approach to System
Modeling
Generative engineering is a new approach
to system modeling using object-oriented
modeling coupled with artificial
intelligence and 3D generative
algorithms; it allows to exhaustively explore
all possible combinations, to manage
uncertainty and variability and to
explore quickly all the functional architectural
and 3D integration solutions
meeting the requirements.
With this object-oriented system modeling
based on the Python programming
language, knowledge about a system is
encapsulated in objects which are defined
by a set of attributes and methods.
The application of algorithms to these
objects allows the execution of automated
tasks in the system design process,
such as architecture research.
The system modeling integrates the
product requirements, the objectives to
be minimized, the technical knowledge
(e.g., design rules) and the functional
(or physical) description and/or the 3D
description of the system.
The advantages of generative engineering
approach are:
* explore all possible configurations to
avoid late questions
* identify the optimal global solution
with respect to the system requirements
to be met
* make informed decisions upstream on
structuring choices
* achieve rapid design iteration loops.
Application to xEV Systems
Architectures
The vehicle system is broken down
into various systems and subsystems,
such as the powertrain system and the
PWT system
Torque wheel [T.m]
Speed wheel
[RPM]
alongside design conconcerning
powertrain
architecture, component
technology, and sizing to fulfill the powertrain
requirements.
These choices made at the powertrain
level subsequently establish the prerequisites
for the cooling subsystem. At the
cooling subsystem level, decisions regarding
architecture and components
must be taken. The choices made at different
system levels, both for architecture
and components, significantly influence
overall system objectives, such as
energy consumption and costs.
Notably, the impact of the system architecture
on system performance may
outweigh that of component sizing and
control. The methodology facilitates architects
and engineers in making optimal
choices for architecture and components
at distinct system levels: powertrain
system and cooling subsystem.
Design exploration at powertrain system
level (HEV)
The powertrain system is modeled using
the approach presented in the previous
section. It is decomposed into the following
components, as shown in Figure 2:
internal combustion engine (ICE), battery,
electrical machine(s), and gearbox(s).
At this stage, designers consider the
powertrain components at a high level of
abstraction.
For instance, the ICE is modeled by an
object that provides a torque and rotational
speed with a single output mechanical
connection. A gearbox is modeled by an
object with two mechanical connections
(input and output) capable of providing a
torque and speed ratio.
ICE
Torque [N.m]
Speed [RPM]
Battery
U [V]
I [A]
Electrical Machine
Torque [N.m]
Speed [RPM]
Figure 2: HEV powertrain system modeling. (Image: Dessia)
24
Gear Box
Ratio
The proposed powertrain system model,
coupled with a decision-tree generative
algorithm, allows for the generation
of all possible solutions for connecting
the components of the powertrain system.
Figure 3 presents some examples of
powertrain architecture generated, with
each architecture represented by a graph.
To meet the powertrain requirements,
each architecture requires specific component
specifications. For example, to
fulfill the same powertrain requirements
(for wheel torque and speed), a series
and parallel HEV powertrain architecture
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Tech Briefs Magazine - October 2023

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