What is MDO? Some popular definitions for
Download
Report
Transcript What is MDO? Some popular definitions for
MULTIDISCIPLINARY DESIGN OPTIMIZATION
-A Paradigm Shift in Design Methodology
for Complex Engineering Systems
K Sudhakar, PM Mujumdar, Amitay Isaacs
Centre for Aerospace Systems Design & Engineering
Dept. of Aerospace Engineering, IIT Bombay
Dec. 6, 2002
MDO - 0
ENGINEERING DESIGN OPTIMIZATION
Decision is objective and not subjective
Forces a mathematical statement of the problem
Dec. 6, 2002
Forces modeling system performance & ‘goodness
criteria’
Captures knowledge - What was the problem
solved, how was it analyzed, how were the
decisions taken, . . .
MDO - 1
ISSUES IN POSING THE PROBLEM
•
Of all variables that influence the design
which to pick as design variables? x X
•
How to confirm that all constraints are g
specified (g, h)?
•
Which one(s) f F to choose as objectives?
•
How to evaluate f, g, h ?
•
How to handle coupled multi-disciplinary (iterative)
analysis
Dec. 6, 2002
MDO - 2
HIERARCHICAL STEPS
IN TRADITIONAL DESIGN
Mission
Requirements
Conceptual
Design
•Optimization
•Parametric
•1st level analysis
•General arrangement and performance
•Representative Configurations
•General internal layout
Conceptual
Baselines
Preliminary
Design
•Sophisticated analysis
•Problem Decomposition
•Disciplinary Optimization
Selected
Baseline
Detailed
Design
May lead to Sub-optimal designs
Source: AIAA MDO White Paper, 1991
Dec. 6, 2002
•Systems Specifications
•Detailed Subsystems
•Internal Arrangements
•Process Design
Production
Baseline
Production
and Support
MDO - 3
TRADITIONAL APPROACH
TO PRODUCT DEVELOPMENT
100%
CONCEPTUAL
100%
PRELIMINARY
100%
DETAILED
100%
KNOWLEDGE ABOUT DESIGN
• AERODYNAMICS
• PROPULSION
• STRUCTURES
• CONTROLS
• MANUFACTURING
• SUPPORTABILITY
• COST
DESIGN FREEDOM
TIME INTO DESIGN PROCESS
Short Conception phase + unequal distribution of disciplines
limited scope for optimization & assessing impact of inter-disciplinary
couplings.
Correction of later problems
Costly/ Lost Time/ Futile
Solutions limited to specific discipline
Source: AIAA MDO White Paper, 1991
Dec. 6, 2002
MDO - 4
LEVERAGE IN THE DEVELOPMENT PROCESS
Ballistic Missile System
C
u
m
u
l
a
t
i
v
e
%
L
C
C
LC
Phase
100
95%
Committed Cost
85%
75
70%
Life cycle cost
effectively rendered
unchangeable for a
given design
50
25
Actual Cost
18%
1%
Concept
7%
Advanced Full-scale
Time
Production
Source: AIAA MDO White Paper, 1991
Dec. 6, 2002
50%
Operations/
Support
MDO - 5
THE DESIGN PROCESS PARADIGM SHIFT
100%
CONCEPTUAL
100%
PRELIMINARY
GOAL
100%
DETAILED
100%
KNOWLEDGE ABOUT DESIGN
• AERODYNAMICS
• PROPULSION
• STRUCTURES
• CONTROLS
• MANUFACTURING
• SUPPORTABILITY
GOAL
• COST
DESIGN FREEDOM
TIME INTO DESIGN PROCESS
Design process reorganized to gain information earlier and to retain design freedom longer
More up-front design
More evenly distributed efforts of disciplines in early design
Alleviate paradox
Design decisions/trade-off reordered
Source: AIAA MDO White Paper, 1991
Dec. 6, 2002
MDO - 6
CONCURRENT ENGINEERING Vs MDO
Life Cycle Emphasis
C
E
M
D
O
Design
Manufacturing
Supportability
Aerospace systems design emphasis
Aerodynamics
Propulsion
Structures
Controls
Time into the process
Ultimate objective - Balanced design by full and formal multi-disciplinary
integration and optimization concurrently in all disciplines
Source: AIAA MDO White Paper, 1991
Dec. 6, 2002
MDO - 7
MDO ?
Multi-disciplinary : More than one discipline
Design – Process of translating requirements into
plays a role. Eg. In aerospace -aerodynamics,
structures, controls, mission, . . .
detailed product specifications.
Optimization – Formal mathematical process of
locating the ‘best’ under ‘constraints’
Dec. 6, 2002
MDO - 8
What is MDO?
Some popular definitions of Multidisciplinary Design Optimisation
• A methodology for the optimal design of complex
engineering systems and subsystems that coherently
exploits the synergism of mutually interacting phenomena
using high fidelity analysis with formal optimization
• MDO is a methodology that combines analysis and in
individual disciplines into that for the entire system for
optimization.
• "How to decide what to change, and to what extent to
change it, when everything influences everything else."
Dec. 6, 2002
MDO - 9
Dec. 6, 2002
MDO - 10
HAS MDO BEEN AROUND?
M (L/D)
Progress in aerodynamic design ?
• B-707
• DC-8
• B-747
• L-1011
• B-767
• A-300
20
15
10
5
0
1960
1970
1980
1990
Year
AIAA-97-1408
Series1
Improvement in Aerodynamics siphoned off for
other system level benefits – MDO in action
Dec. 6, 2002
MDO - 11
CONVENTIONAL DESIGN V/S MDO
Conventional Aerospace Design Practice
Dec. 6, 2002
Heirarchichal
Dependence on Parameter trends and trade-off
studies
Independent disciplinary design + System level
reviews
Optimization limited to disciplines
Resolution of interdisciplinary conflicts nonautomated
Relying heavily on previous experience
Overall – more heuristic, than formal
mathematical optimization
MDO - 12
CONVENTIONAL DESIGN V/S MDO
Multi-disciplinary Design Optimization
Low fidelity models => Conceptual design
Tightly coupled inter-disciplinary codes. (Close knit group) ??
All or most of the following,
Largely automated within a formal framework
Formal mathematical methods and high fidelity
computations indispensable
Interdisciplinary couplings formally modeled/retained
Design freedom to significantly affect system
performance in multiple disciplines simultaneously
Disciplinary authority. Parallel execution.
Dec. 6, 2002
MDO - 13
CONVENTIONAL DESIGN V/S MDO
Multi-disciplinary Design Optimization (contd.)
Dec. 6, 2002
Special architectures for problem formulation/
decomposition
•
System level objectives, constraints, variables
•
Disciplinary (local) constraints, variables
•
Coupling variables and constraints
•
System level and discipline level optimizations
Human expertise & judgement given due weightage
MDO - 14
MDO CONCEPTUAL ELEMENTS
Information Science
& Technology
Design-Oriented
MD Analysis
MD Optimization
Software
Integration
Mathematical
Modeling
Optimization
Problem
Formulation
S/W Engineering
Practices
Cost v/s Accuracy
Trade-off
Decomposition
Data Management,
Storage & Visualization
Smart
Reanalysis
Interdisciplinary
Feasibility
Data & S/W
Standards
Approximations
Design Space
Search
Human
Interface
Sensitivity
Analysis
Source: AIAA MDO White Paper, 1991
Dec. 6, 2002
MDO - 15
CHALLENGES IN MDO
IMPLEMENTATION
Information Science & Technology
• Computational resources (CPU, memory, disk space)
Distributed parallel processing
• Common parametric geometric model
• Software support
s/w integration of proprietary, legacy, commercial, . .
configuration control and data management
collaborative work environment, person-person/machine
• Human expertise/experience capture
Dec. 6, 2002
MDO - 16
CHALLENGES IN MDO
IMPLEMENTATION
Multidisciplinary Analysis
• Well posed interfaces for disciplines
• Discipline and MD sensitivities
• Mathematical modeling of LC disciplines
• Automated grid generation for CFD, FEM
• Cost & run-time of high fidelity analysis
MD Optimization
• Problem definition
• MDO architectures
Dec. 6, 2002
• Design Space Search
MDO - 17
OPTIMIZATION ISSUES IN MDO
Dec. 6, 2002
Single level monolithic optimization (conventional)
Decomposition
• Decomposed Analysis
- System level optimization
- Parallel disciplinary analysis
• Decomposed optimization
- Multi-level (system and subspace) optimization
- Parallel disciplinary analysis
System sensitivity analysis
Design oriented analysis, Surrogates
Improved optimization algorithms
• Large number of design variables & constraints
• Gradient free
MDO - 18
OPTIMISATION ISSUES IN MDO
• Which optimisation algorithm to use?
– Gradient based? How to generate gradients?
– Evolutionary? How many function evaluations?
• Evaluation of gradients?
Requirements on convergence more severe
than that required for engineering analysis.
• Noisy functions?
f
X
Dec. 6, 2002
MDO - 19
MDO GROWTH OVER THE YEARS
1982 : Holt Ashley AIAA lecture "Making things Best ..."
"There are over 8073 papers in Optimal Control,
Aerodynamic
Optimisation
& Structural Optimisation.
Not one paper on Optimization in Aircraft Design”
1991 : AIAA White Paper on MDO; &
Special issue of Journal of Aircraft
1996 : Over 200 papers on MDO application to
A/C Design, including from Industry
1998 : AIAA White Paper on MDO.
“Summary of Industry MDO Applications & Needs”,
Geising & Barthelemy
1999 : Second Special Issue of Journal of Aircraft
Dec. 6, 2002
MDO - 20
MDO STATUS AT A GLANCE
Generalized MDO environment – far from reach
Most common applications
• One discipline (structures) with other discipline as constraints
• Simultaneous aerodynamic and structural optimization
Wings
Aircraft configurations (HSCT, BWB)
Rotor blades
• Coupling of preliminary design with mission and performance
optimization catching up
• Trajectory optimization in Space vehicles
Disciplines - propulsion, trajectory analysis, weights, sizing
• Simultaneous structures, aerodynamics and control optimization
Dec. 6, 2002
MDO - 21
SUMMARY OF INDUSTRY MDO APPLICATIONS
Source: AIAA MDO White Paper, 1998
Dec. 6, 2002
MDO - 22
An Example – HSCT (1991-’99)!
HSCT-2
HSCT-3
5 design variables, 6 constraints
WINGDES, ELAPS, Range equation, engine deck
Time for one cycle = 10 minutes
7 design variables, 6 constraints
ISAAC, COMET, Range equation. Engine deck
Time for one cycle = 3 hours
HSCT-4
271 design variables, 31,868 constraints
CFL3D, USSAERO, GENESIS, FLOPS, ENG10
Time for one cycle = 3 days (Analysis, sensitivity, optimizer step)
32 P Origin 2000, n x {Sun Ultra-2, SGI R10000}
CFL3D - CFD in Euler mode;
Dec. 6, 2002
USSAERO – Panel code,
GENESIS - FEM
MDO - 23
HSCT - 4
Dec. 6, 2002
Detailed problem definition took more than 1 year
to extract from people
Requirements document touched 100 pages merely
to define analysis process, tools used and data
flow
90% of work went into preparing analysis codes
for MDA and integrating them in a proper
sequence. (Such experiences have prompted
development of MDO Frameworks)
MDO - 24
MDO@CASDE OVER THE YEARS
Aug 1999
Aug 2000 - First meeting of SIG-MDO
Jan 2001 - Professional Development Course on MDO
Jun 2002 - Second meeting of SIG-MDO
Mar 2003 - Third Meeting of SIG-MDO
Sep 2003 - International Conference on MDO
Feb 2004 - Fourth Meeting SIG-MDO
Jan 2005 - Fifth Meeting of SIG-MDO
Dec. 6, 2002
- CASDE asked to spur initiatives in MDO
MDO - 25
End of MDO Introduction
Dec. 6, 2002
MDO - 26
MDO STATUS AT A GLANCE
MDO Elements
• Decomposition, Approximations, Sensitivity Analysis well
researched but not matured to industry requirements
• Other issues ??
Recent Trends - Generic MDO Technologies (NASA, EC )
• Distributed heterogeneous environment
• Problem specification and setup, decision support
systems
• Generic software framework for MDO
• Multi-objective design optimization
MADIC,
FRONTIER, FIDO, iSIGHT, USMADE
IPPD system for aircraft design (ASDL, GIT Atlanta)
Knowledge Based Engineering (Boeing)
• MDO in preliminary design focused on aero-elasticity
with FEM, CFD
Dec. 6, 2002
MDO - 27