Korea-Japan Joint Workshop on Rotorcraft 2023

KARI MDAO System Development Plan and Status for
the Hybrid eVTOL Aircraft DesignFebruary 10, 2023
Seung-Kil Paek
Korea Aerospace Research Institute⚫

Interests in UAM(Urban Air Mobility) or AAM(Advanced Air Mobility) is in fullswing.
▪ The Vertical Flight Society (US) counts almost 700 entrants in the AAM industry with newones added on a weekly basis⚫

KARI(Korea Aerospace Research Institute) should provide the Korean
industry with the core technology for those types of aircrafts as a Korean
government funded research institute since 1989.
▪ Developing also an eVTOL aircraft a.k.a. OPPAV1▪ Developing MDAO2 technology on eVTOL aircraft
through an internal project since 2019.
•Started a new five-year-long internal project to develop
a MDAO system.

1OPPAV : Optionally Piloted Personal Air Vehicle, 2019 ~ 2023
2MDAO : Multi-disciplinary analyses and optimization

KARI MDAO System Development Plan and Status1

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There have been various MDAO Frameworks, related software and digitalcontents:▪ CEASIOM(CEASIOMpy), pyMDO, OpenMDAO, 3DOPT, MDOPT, CPACS, RCE, and etc.

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DLR (Germany) started the development of the aircraft design environment
from 2005.
DLR created the open-sourced CPACS as a common namespace.
▪ a standard for exchanging aircraft design information among aviation-related institutions ofDLR.

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DLR developed the open-sourced RCE as a process integration framework▪ It supports collaborative and distributed work.

KARI MDAO System Development Plan and Status2⚫

A collaborative MDAO system▪ the design tools implemented by each discipline specialist are operated in independent
software environments▪ their outputs are shared by design tools in other fields

DLR has been conducting collaborative optimization design research ina distributed environment early on.

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In the AGILE project,▪ AGILE : Aircraft 3rd Generation MDO for Innovative Collaboration of Heterogeneous Teamsof Experts•

from 2015 to 2018, part of the Horizon 2020 program.

▪ DLR has reached the level of designing an aircraft by implementing interworking between
processes distributed across three continents, 19 institutions, and heterogeneous platforms

KARI MDAO System Development Plan and Status3⚫

Software structure▪ Collaborative software structure will be used:▪ The independent analysis method established by using the most familiar software tools
such as Excel, script, commercial S/W, and in-house software, in the most appropriate
operating environment by each discipline expert will be combined as a process.
▪ The concept of establishing a process is not to create a new tool, but to transform an
existing tool into a form that can be shared as much as possible on the network▪ In Korea, optimal design researches under such a collaborative system have hardly
been conducted.
•Hence this research will be a big challenge.

KARI MDAO System Development Plan and Status4⚫

Central Data Model▪ Central data model will be used to minimize the interfaces.
▪ Communication between different disciplines is achieved throughdesign parameters.
▪ In KARI, these design variables were independently defined andthere was no common parameter pool until now.
▪ In this project, CPACS1 is used to control design variables in all
disciplines as much as possible▪ Using CPACS, is like forcing people with different mother tongues
to use only one foreign language!
•Big challenge

Courtesy of https://github.com/DLR-SL/CPACS▪ CPACS is mainly used for conventional fixed wing aircrafts with jet
fan engines until now.
•It needs much enhancements so that it can be used for UAM aircraft design

1CPACS : Common Parametric Aircraft Configuration Schema. A data definition for the airtransportation system. Opensource digital content hosted in github.

KARI MDAO System Development Plan and Status5⚫

Process Integration▪ KARI had used ModelCenter® for the process integration•Kang, H.-J. “Design optimization of QTP-UAV prop-rotor blade using ModelCenterⓇ”. Journal ofAerospace System Engineering, Vol. 11, No. 4,
pp. 36—43, 2017.

▪ Recently, RCE, an open-source replacement
have been tested instead.
▪ The user experience with RCE was satisfactory.
▪ RCE will be used for this project.

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Three engineering tools was integrated:• an aircraft geometry creating tool using OpenVSP and Rhino®
• a commercial mesh generation tool CENTAUR®
• an inhouse CFD solver to make geometry design study
KARI MDAO System Development Plan and Status6⚫

2022 : MDO System Requirements & System Architecture Design
▪
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Define the requirements for the MDAO system
Define the tool list to be integrated in the MDAO system
Define the interface using the central data model.
Define the workflow of the MDAO system as XDSM1 format

2023 :1XDSM : Extended Design Structure Matrix

Verification&Validation
Flow▪ Verification of System Architecture▪ Development of tools and discipline workflows

2024 : Verification of each discipline workflow⚫ 2025 : Verification of the integrated workflow⚫ 2026 : Verification of the optimal design capability⚫

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Based on system engineering methodology
for software development.
▪ Project management with Redmine software▪ Configuration control with Git software

KARI MDAO System Development Plan and Status

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KARI is making a concept design of a 6 seated UAM aircraft:▪ Define the top-level requirement and analysis standard•

the follow-up study of the OPPAV aircraft▪ Decide the design variables, analysis cases, and major performance objectives▪ Establish an optimal design problem▪ Create a concept design.

KARI MDAO System Development Plan and Status8⚫

2024 :▪
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▪
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Build a surrogate model for each discipline workflow
The collected surrogate models are integrated into the total workflow.
The work will be used for optimal design study
The optimal design will be reviewed.

2025 :▪ The discipline workflows will be integrated altogether.
▪ DOE using the integrated workflow will be made.
▪ Optimal solution using DOE results⚫

2026▪ Direct optimization with the integrated workflow

KARI MDAO System Development Plan and Status

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For the design of the MDAO system, such as the input/output definition ofeach component and the workflow design combining each component, tools
are needed:▪ KADMOS••

An open source python package based on the data schema called CMDOWS
Little documentation and not easy to start▪ MDAx : MDO Workflow Design Accelerator•••

A web-based GUI application by DLR
An easy-to-use substitute of KADMOS
more promising than KADMOS.

KARI MDAO System Development Plan and Status

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KARI have been studying the usability of various DLR software tools:▪ RCE, TiGL, TiXI, VAMPzero, CPACS and MDAx⚫

KARI-DLR cooperation was proposed by KARI in 2020 and welcomed by DLR.
▪ Enhancement of DLR tools through the test and evaluation▪ Discussions were made to materialize the cooperation through2021.
▪ An online meeting was made between the aeronautics research
directorate of KARI and the institute of system architecture inaeronautics of DLR in March 2022 to discuss the practicalcooperation.

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Online workshops have been held four times through the video conferencing▪
▪
▪
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from May 2022 to Aug 2022
CPACS and TiGL Tutorial and Q&AHands-on exercises using MDAx via the web “as-a-service”
KARI work procedures for flight control, mission analysis, andgeometry generation▪ Totally 43 people from KARI side attended the workshops.
KARI MDAO System Development Plan and Status11

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MDO System Requirement Documentation

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MDO System design needs the cooperation between the experts on physicalmodels constituting the system.
⚫ Intensive discussions and brain storming were needed in a short time.
⚫ Six internal workshops were made in 2022.
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February : eVTOL concept design seminar
March : 1st optimal design problem definition
May : CPACS-RCE basics and 1st N2 chart build
July : 2nd N2 chart build
August : 2nd optimal design problem definition
September : MDO system design

KARI MDAO System Development Plan and Status13⚫

MDO System Requirement – Top Level Requirements▪ Six top level requirements
••
•
•••

Preliminary design for 5 seated hybrid eVTOL aircrafts
CPACS as central data model
RCE as the process integrator
Each Component to be able to separate execution
Interoperable components
System engineering to be followed

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MDO System Requirement – High Level Requirement▪ Five functional requirements▪ Six environment requirements▪ One Performance requirement

KARI MDAO System Development Plan and Status15

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MDO System Requirement – Use Cases and Test Cases▪ Five use cases•••••

One execution of a specific component
Design of Experiment (Multiple executions) using a specific component
Design of Experiment (Multiple executions) using plural components
Optimization using plural components
Optimization using all components

KARI MDAO System Development Plan and Status16⚫

Major tools to be integrated into the MDAO system:••

Geometry : inhouse software using CPACS, TiXI, TiGL, Python
Aerodynamics* :
◆◆◆•
•
•
•
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Athena Vortex Lattice (AVL) code
Inhouse source doublet panel method + actuator disk theory
OpenFOAM + actuator disk model

Flight control : inhouse flight model, MATLAB, CONDUITMission performance and Prop* : inhouse software, CAMRAD II
Noise* : inhouse software
Structure* : inhouse FE modeler, MSC/NASTRAN, Hypersizer
Hybrid electric propulsion* : inhouse software in MATLAB andSIMULINK*Need to be developed or upgraded

KARI MDAO System Development Plan and Status

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TLAR
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Payload : more than 550 kg (1 pilot and 5 passengers)
Cruise speed : more than 250 km/h
Maximum speed : more than 300 km/h
Maximum range : more than 200 km
Maximum endurance : more than 60 minutes
Maximum altitude : 2 km
Noise : less than 65dBA at T/O and Landing (100 m distant and at 100 m altitude)

Assumption▪ Battery Pack Energy Density : more than 250 Wh/kg

KARI MDAO System Development Plan and Status18

⑤ Descent 227 km/h

④ Cruise 250 km/h

⑥ Reserve 15min⑦ Tran. 227 → 0 km/h
⑧ Vertical Landing
Altitude 500 m (AGL)

Batt. SOC 20%③ Climb 227 km/h
Mission Range 180 km② Tran. 0 → 227 km/h
① Vertical Take-off

Batt. SOC 100%

✓ Max Range 230 km✓ Max Endurance 60 min

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Design Parameters▪ 𝑘, 𝑏 : the kink position and span of the main wing
▪ 𝐶𝑟𝑜𝑜𝑡 , 𝐶𝑘𝑖𝑛𝑘 , 𝐶𝑡𝑖𝑝 : the chord lengths of the root, kink, and tip
sections of the main wing▪ Λ1 , Λ 2 : the sweep angles of the root and kink sections of the mainwing▪ 𝜃1 , 𝜃2 : the twist angles of the kink and tip sections of the mainwing▪ Γ1 , Γ2 : the dihedral angles of the root and kink sections of themain wing
▪ Hybridization factor⚫

Objective▪ Minimize the maximum take-off weight

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Draft XDSM chartcpacsUtil : from CPACS to higher level parameter
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Enhancement being devised▪ Elements for UAM specific systems▪ Performance Map for Propellers and Motors

KARI MDAO System Development Plan and Status24

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User manual is being madeKARI MDAO System Development Plan and Status25

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Concept Design Tool
▪ Based on SUAVE(an open source concept design tool by Stanford Univ)▪ Devised a component for the Lift-Tilt configuration

KARI MDAO System Development Plan and Status26

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The first sizing▪ Based on OPPAV, one-seated vehicle, the sizing was made with the six-seater
requirement.

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The KARI plan, from 2022 to 2026, on the overall MDAO system development
was explained⚫

KARI-DLR cooperations until now were explained.

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MDAO system design and concept design in 2022 were explained▪
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Requirements
System design
Interfaces
Component workflows

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