dr. achille messac multidisciplinary design and optimization laboratory

04/22/23 1Engineering & Technology Management Group

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Dr. Achille MessacMultidisciplinary Design and Optimization LaboratoryMechanical, and Aeronautical Engineering Department

Rensselaer Polytechnic Institute

Multidisciplinary Design Optimization as a Powerful Risk Mitigation Tool


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Presentation Outline

1- Multidisciplinary Design Optimization

What is it?

A bit of history…

2- Aerospace and other MDO Applications

3- Multiobjective reality -- Physical Programming

4- Venturing into the nondeterministic environment of RISK

– The role of MDO

5- Optimization in Conceptual Design

6- Concluding Remark


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ProductDevelopmentFrom Early Timid Optimization Applications

to MDO

From 50’s to 70’s, engineering optimization is

- Primarily Uni-disciplinary Aerospace >> Structure – min. mass

- Computationally Challenged

- Of Timid Problem Scope

- Heavily reliant on the defective MO method -- weighted sum


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ProductDevelopmentFrom Early Timid Optimization Applications

to MDO -- Cont.

In early to mid eighties

- Computers become faster, and start decreasing in cost

- Optimal Control grows in popularity

- Large Space Structures research grows

- Concurrent Engineering becomes a cherished word

- Bi-disciplinary optimization: Control-Structure (Messac, Hale)

- NASA, Air Force, and JPL initiate MDO, CSI programs

- Government financial resources relatively abundant (human, computer – however slow)

- First Pre-MDO conference is held at Langley (Sobieski – 1984)


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From Early Timid Optimization Applications to MDO -- Cont.

Mid 80’s to Mid 90’s

- Computers are much faster and cheaper

- AIAA MDO TC is born (Transition from Bi- to Multi-disciplinary)

- MDO is still largely Deterministic

- MDO is still implemented in later stages of designNot at Conceptual Design Stage

- MDO is still largely addressing traditional disciplinesAero, Structure, Control – Neglecting Cost, Management, etc.

While…

- MDO’s popularity and use grows many-fold (e.g. GE heating element)

- MDO research enjoys strong international growth

- MA&O Conference grows more and more successful


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From Early Timid Optimization Applications to MDO -- Cont.

Mid 90’s to Present

-MDO is still implemented in later stages of designNot at Conceptual Design Stage-- New Conceptual Design optimization method emerged

(s-Pareto based Conceptual Design – Mattson-Messac)

-Optimization is still often used using the defective weighted sum paradigm

- Computer cost and speed are dramatically reduced

- MDO grows within government AND industry

-MDO begins to address non-traditional disciplinesCost, Management, Manufacturability, Profit, Safety, Risk, etc.

- MDO becomes more appropriately treated as Multiobjective

- MA&O Conference continues to prosper: 2002 Atlanta; Sept. 2004 Near Saratoga Springs NY


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Multidisciplinary Design Optimization (MDO)

CFD Structures

Performance

Aero Loads

Deformations

Mach Number

Str. WeightAero LoadsTOGW Design space discipline 1

Design space discipline 2Design Variables

Performance

MultidisciplinaryOptimal Design

Discipline 1 Optimum

Feasible Design Space

SuboptimalDesign

Conventional Trades

MDO Search

Discipline 2 Optimum

• Effective Integration of Individual Disciplines/Subsystems to Capture the Interactions• Novel Solution Procedures to Enable Improved System Solutions:

- Account for Interdisciplinary Couplings & Integrated Product Team (IPT) settings.

• MDO = { Design Optimization, Design Exploration, Cross-Attribute Optimization, InterDisciplinary Optimization, System Synthesis }


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NVH

FrontalCrash

Offset Crash

Roof Crush

Minimize: Vehicle Weight

Subject to: NVH design targetsFrequencyBending DisplacementTorsion DisplacementFrontal crash design targetsDummy HICDummy Chest GProbability of severe injury

Roof crush design targetsMaximum resistant force

50% Frontal Offset crash design targetsIntrusion

Side Impact design targets

Displacements

Viscous Criterion

Safety

Ford-SGI - Vehicle System MDO Project

HPC/MDO for NVH & Safety on the Origin 3800

Side Impact

Everything influenceseverything else!


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Aerodynamics

Propulsion

Controls

Hydraulics

Avionics

ElectricalsystemFuel

system

Landing gear

• Structural optimizationis at MDO roots

AIRFRAMESTRUCTURE

In Vehicle Everything Couples to Structure


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Car Body Optimization for Noise, Vibration, Harshness, and Crash

• Vehicle Roof Crush is a federally mandated requirement to enhance passenger safety during a rollover event.

• NVH must be constrained for passengers comfort

•Modified NVH Model with a Square Ram to Perform Roof Crush as specified by regulations

• Finite Element Model of 390,000+ dof, 6000+ boundary conditions;

• 20 design variables

• Optimization executed using Response Surface approximations to crash analysis and sensitivity-based approximations to NVH

• Implemented on a computer with 256 processors

• Single processor computer would need 257 days to do this optimization• It was condensed to 1 day on the multiprocessor machine.

Courtesy:Ford Motor Co./R-J. Yang


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Air Borne Laser System Design

BMCBMC44I I • Boeing

•8-10 March

Beam Control SystemBeam Control System• Turret Assembly

•Large Optics•Four Axis gimbals•Transfer optics

• Beam Transfer Assembly•Sensor Suite•Active Mirrors•Illuminators•Electronics•Software/Processors

747F Aircraft - 747F Aircraft - • BoeingBoeing • CDR 29 Feb - 3 Mar

Chemical Oxygen IodineChemical Oxygen IodineLaser (COIL) Laser (COIL) • TRW• 21-23 March

System Level DesignSystem Level Design• Boeing• CDR 25-27 April

12


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ProductDevelopmentSupersonic Business Jet Test Case


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• MDO necessary to protect very small payload margin• Massively computational problem• Candidate MDO method : design data bases for subsystems and disciplines precomputed off-line using multiprocessor computing

Examples of applications that will need all that

Configuration “A” Configuration “B”

Courtesy: NASA LRC/Troutman


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Obtaining an effective objective function is difficult in practice.

Weighted-Sum (WS) method for optimization has its inherent significant drawbacks. It is incapable of capturing a large class of potentially desirable Pareto solutions. It is also the most popular!

Compromise Programming (CP) method can be used to generate a complete set of efficient solutions, but its reliance on meaningless weights is a serious problem. Pareto ...

Etc.

Prevailing Practice


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Obj. Fun. Line

1 1 2 2J w f w f Optimal Solution UsingWeighted-Sum


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1 1 2 2J w f w f Pareto Solutions Using Weighted-Sum


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1 1 2 2J w f w f

Obj. Fun. Line

Weighted-Sum in Non-Convex Pareto Frontiers


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Obj. Fun. Line

1 1 2 2n nJ w f w f

Weighted Compromise Programming for Non-Convex Pareto Frontiers


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Quantify Preference for Each Design Metric

Ex: Mass of Beam

Highly Desirable < 250 (kg)

Desirable 250 - 275

Tolerable 275 - 300

Undesirable 300 - 325

Highly Undesirable 325 - 350

Unacceptable > 350

Physical Programming (cont.)


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Expressing Designer Preference During the Optimization Process

Expressing Designer Preference During the Optimization Process


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Behavior of the PP Class Functionfor Change in Preferences

Behavior of the PP Class Functionfor Change in Preferences


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Numerical Example 1 (of 2)Numerical Example 1 (of 2)

Minimize 25

24

23

22

211 xxxxxf

354

3212 )(01.0

323 xx

xxxf

25.02 54321 xxxxxSubject to

05.06.08.024 254321 xxxxx

1025

24

23

22

21 xxxxx

WS CP PPResults

Behaviors of different objective functions for a convex frontier


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Example 2Example 2

1 1min { ( ), ( )}J f f

sin1 f

72 sin1f

2532.15326.0

WS CP PPResults

Behaviors of different objective functions for a concave frontier


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The Reality of Uncertainty and Risk

1- Non-Deterministic Forum -- SDM

2- Traditional Factor-of-Safety approach is rapidly becoming an anachronistic relic of the past

3- Development of probabilistic design optimization methods

4- New MDO methods emerge to model risk and uncertainty

5- Profit as a design metric gains acceptance

6- Growing recognition that optimization in Conceptual Design is a necessity

7- TC has moves to Engineering & Technology Management Group to explore expanded collaboration


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• Not Primarily a Technical Problem• Critical Issues are: EDUCATION, MANAGEMENT, AND ORGANIZATION “CULTURE”

A Challenge?

INJECTING MDO INTO INDUSTRIAL PRACTICE:


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ProductDevelopmentConcluding RemarksConcluding Remarks

• The picture is somewhat muddied!Much of good news; yet much to be desired.

• MDO’s power is evident.

•Yet its strongest influence can be felt in this decade if -- its application in a holistic setting comes to pass, and-- key methodological developments take place in collaboration with non-traditional participants

• MDO is a unifying indispensable glue, if we are to effectively design the ultra-safe, profitable, and effective design of the future

• For more information: www.rpi.edu/~messac

dr. achille messac multidisciplinary design and optimization laboratory

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