1. Dec. 6, 2002 MDO - 0 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

2. Dec. 6, 2002 MDO - 1 ENGINEERING DESIGN OPTIMIZATION Decision is objective and not subjective Forces a mathematical statement of the problem Forces modeling system performance & ‘goodness criteria’ Captures knowledge - What was the problem solved, how was it analyzed, how were the decisions taken,...

3. Dec. 6, 2002 MDO - 2 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

4. Dec. 6, 2002 MDO - 3  May lead to Sub-optimal designs Mission Requirements Conceptual Design Conceptual Baselines Preliminary Design Selected Baseline Detailed Design Production Baseline Production and Support General arrangement and performance Representative Configurations General internal layout Optimization Parametric 1st level analysis Sophisticated analysis Problem Decomposition Disciplinary Optimization Systems Specifications Detailed Subsystems Internal Arrangements Process Design HIERARCHICAL STEPS IN TRADITIONAL DESIGN Source: AIAA MDO White Paper, 1991

5. Dec. 6, 2002 MDO - 4 TRADITIONAL APPROACH TO PRODUCT DEVELOPMENT  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 CONCEPTUAL 100%PRELIMINARY 100%DETAILED 100% DESIGN FREEDOM KNOWLEDGE ABOUT DESIGN TIME INTO DESIGN PROCESS 100% AERODYNAMICS PROPULSION STRUCTURES CONTROLS MANUFACTURING SUPPORTABILITY COST

6. Dec. 6, 2002 MDO - 5 Ballistic Missile System LEVERAGE IN THE DEVELOPMENT PROCESS 25 50 75 100 Concept AdvancedFull-scale Production Operations/ Support 70% 7% 1% 85% 95% 18% 50% Time Committed Cost Cumulative%LCCCumulative%LCC LC Phase Actual Cost Source: AIAA MDO White Paper, 1991 Life cycle cost effectively rendered unchangeable for a given design

7. Dec. 6, 2002 MDO - 6 THE DESIGN PROCESS PARADIGM SHIFT  More up-front design  More evenly distributed efforts of disciplines in early design  Alleviate paradox  Design decisions/trade-off reordered Design process reorganized to gain information earlier and to retain design freedom longer Source: AIAA MDO White Paper, 1991 CONCEPTUAL 100%PRELIMINARY 100%DETAILED 100% GOAL DESIGN FREEDOM AERODYNAMICS PROPULSION STRUCTURES CONTROLS MANUFACTURING SUPPORTABILITY COST KNOWLEDGE ABOUT DESIGN TIME INTO DESIGN PROCESS 100%

8. Dec. 6, 2002 MDO - 7 Ultimate objective - Balanced design by full and formal multi-disciplinary integration and optimization concurrently in all disciplines CONCURRENT ENGINEERING Vs MDO MDO MDO Aerospace systems design emphasis Aerodynamics Propulsion Structures Controls Time into the process Source: AIAA MDO White Paper, 1991 Life Cycle Emphasis Design Manufacturing Supportability CE CE

9. Dec. 6, 2002 MDO - 8 MDO ? Multi-disciplinary : More than one discipline plays a role. Eg. In aerospace -aerodynamics, structures, controls, mission,... Design – Process of translating requirements into detailed product specifications. Optimization – Formal mathematical process of locating the ‘best’ under ‘constraints’

10. Dec. 6, 2002 MDO - 9 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."

11. Dec. 6, 2002 MDO - 10

12. Dec. 6, 2002 MDO - 11 HAS MDO BEEN AROUND? B-707 DC-8 B-747 L-1011 B-767 A-300 AIAA-97-1408 Improvement in Aerodynamics siphoned off for other system level benefits – MDO in action

13. Dec. 6, 2002 MDO - 12 CONVENTIONAL DESIGN V/S MDO  Conventional Aerospace Design Practice  Heirarchichal  Dependence on Parameter trends and trade-off studies  Independent disciplinary design + System level reviews  Optimization limited to disciplines  Resolution of interdisciplinary conflicts non- automated  Relying heavily on previous experience  Overall – more heuristic, than formal mathematical optimization

14. Dec. 6, 2002 MDO - 13 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.

15. Dec. 6, 2002 MDO - 14 CONVENTIONAL DESIGN V/S MDO Multi-disciplinary Design Optimization (contd.)  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

16. Dec. 6, 2002 MDO - 15 MDO CONCEPTUAL ELEMENTS MD Optimization Design-Oriented MD Analysis Interdisciplinary Feasibility Decomposition Design Space Search Optimization Problem Formulation Mathematical Modeling Cost v/s Accuracy Trade-off Smart Reanalysis Approximations Sensitivity Analysis Software Integration Data & S/W Standards Data Management, Storage & Visualization S/W Engineering Practices Human Interface Information Science & Technology Source: AIAA MDO White Paper, 1991

17. Dec. 6, 2002 MDO - 16 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

18. Dec. 6, 2002 MDO - 17 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 Design Space Search

19. Dec. 6, 2002 MDO - 18 OPTIMIZATION ISSUES IN MDO  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

20. Dec. 6, 2002 MDO - 19 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? X f

21. Dec. 6, 2002 MDO - 20 MDO GROWTH OVER THE YEARS & Structural Optimisation. 1982 : Holt Ashley AIAA lecture "Making things Best..." "There are over 8073 papers in Optimal Control, AerodynamicOptimisation 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

22. Dec. 6, 2002 MDO - 21 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

23. Dec. 6, 2002 MDO - 22 SUMMARY OF INDUSTRY MDO APPLICATIONS Source: AIAA MDO White Paper, 1998

24. Dec. 6, 2002 MDO - 23 An Example – HSCT (1991-’99)! HSCT-2 5 design variables, 6 constraints WINGDES, ELAPS, Range equation, engine deck Time for one cycle = 10 minutes HSCT-3 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; USSAERO – Panel code, GENESIS - FEM

25. Dec. 6, 2002 MDO - 24 HSCT - 4 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)

26. Dec. 6, 2002 MDO - 25 Aug 1999 - CASDE asked to spur initiatives in MDO 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 MDO@CASDE OVER THE YEARS

27. Dec. 6, 2002 MDO - 26 End of MDO Introduction

28. Dec. 6, 2002 MDO - 27 MDO STATUS AT A GLANCE  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  MDO Elements Decomposition, Approximations, Sensitivity Analysis well researched but not matured to industry requirements Other issues ??