Multi-Objective Design Exploration (MODE) Applied to a Regional Jet Design. Shigeru Obayashi Institute of Fluid Science Tohoku University

Transcription

1 Multi-Objective Design Exploration (MODE) Applied to a Regional Jet Design Shigeru Obayashi Institute of Fluid Science Tohoku University

2 n Introduction Outline n Multi-Objective Design Exploration (MODE) n MRJ structure modeling n Objectives n Structure design of MRJ Horizontal Tail n Visualization of design space n Conclusion MRJ: Mitsubishi Regional Jet

3 MODE Applications to MRJ MODE as aircraft MDO has been proposed and applied to MRJ wing design (MHI-Tohoku-university collaboration) Previous Applications Wing-body configuration MDO Wing-nacelle-pylon-body configuration MDO Winglet design MDO

4 MODE to Solve Multi-objective Optimization Multi-Objective Design Exploration (MODE) Multi-objective Genetic Algorithm Computational Fluid Dynamics Step 1 Multi-objective Shape Optimization Design Database Visualization and Data Mining Step 2 Knowledge Mining Design Knowledge Data mining: maps, patterns, models, rules

5 Self-Organizing Map (SOM) " Visualization of design space " Neural network model proposed by Kohonen n Unsupervised, competitive learning " High-dimensional data 2D map " Qualitative description of data Data vector Reference vector for k-th unit SOM provides design visualization: Seeing is understanding (Essential design tool) High-dimensional Vector space k-th unit Map space

6 MRJ Structural Features ü Application of composite materials is about 12% ü Need to reduce structural weight of main components Aluminum wing box Composite horizontal tail box (present application) Composite vertical tail box etc Titanium 3% Steel 2% CFRP 9% GFRP 3% Aluminum 83%

7 Previous MDO modeling for MRJ Previous MODE applications - Aerodynamics : based on high-fidelity CFD model - Strength : based on low-fidelity structure model Need to introduce high-fidelity structure model into MODE skin skin-stringer equivalent plate Low-Fidelity Structure model Strength Criteria stringer Various buckling modes for skin, stringer and spar etc. Actual aircraft design Fidelity Gap Plate compressive and tensile stress (rough evaluation) Aircraft model for MRJ MDO High-Fidelity CFD model

8 Structure of Horizontal Tail Wing Key Points for H-Tail Structural Design ü Various interactive criteria for buckling Euler buckling, Stringer crippling Skin bucking, Stiffened panel buckling Spar web shear buckling Spar à Hard to determine optimum combination between rib pitch (A) & stringer pitch (B) Skin Stringer A B Rib Conventional Approach for Rib-Str. Pitch Optimization ü Parameter study Weight Global Optimum? à Limited search of design space with interactive buckling criteria à Global optimum? Local optimum? Rib P1 Str. P1 Rib P1 Str. P2 Rib P2 Str. P1 Rib P2 Str. P2

9 Objectives Introduce a high-fidelity structure model into MODE based on detailed buckling modes using realistic aircraft structure model Apply the new MODE to MRJ Horizontal Tail

10 Definition of Optimization Problem 1. Assumptions H-Tail OML (fixed) Fixed H-Tail OML & box config. Fixed design loads Fixed stacking sequence T-type stringer Str. Pitch H-tail box (fixed) H t W T-type Stringer t à Fixed W & H à t = sizing parameter Sizing criteria Rib Pitch à Euler & Skin buckling à Stringer crippling à Stiffened panel buckling à Spar web shear buckling 2. Objective Minimize structural weight Minimize number of main structure parts (rib & stringer) 3. Design variables Rib pitch (at regular intervals) Str. pitch (at regular intervals) 4. Criteria Str. thickness t > tmin (specified) Strain margin > Specified margin

11 Flowchart of Present Approach Define design space Choose sample points Strength evaluation Design of experiment: Latin hypercube NASTRAN-based structural sizing Construct surrogate model Response surface model: Kriging model Find non-dominated front of EIs Optimization: ARMOGA Check the model and front Extract design space Data mining: SOM

12 NASTRAN-based Structural Sizing Design parameters Rib & Str. Pitch, Initial thicknesses Automated FEM generation OML (fixed) Design Loads (fixed) OML: Outer Mold line FEM: Finite Element Model Static analysis by NASTRAN Internal stress, strain FEM update Structural sizing New thicknesses, Weight Horizontal Tail FEM No Converged? Yes Converged thicknesses & weight Number of stringers and ribs NASTRAN Static Analysis

13 Results - Optimum Solution Kriging model was constructed based on 36 sample points à Tradeoffs between two objective functions à Improvements over the baseline design Constructed Weight RSM Number of StructuralComponents 10 OptimumDirection Weight Initial poin ts 1st update 2nd update Baseline 20kg Comparison of objective functions among the baseline and sample points

14 Results - Design Knowledge SOMs were generated to extract design knowledge à Optimum str. pitch can contribute to reduce both of the inboard & the outboard weights à Smaller rib pitch is effective to reduce the inboard weight à Larger rib pitch is effective to reduce the outboard weight Optimum pitch Larger pitch Smaller pitch Additional weight reduction by using larger outboard rib pitch than inboard (new design concept) Regular interval rib pitch (previous design concept)

15 Conclusion MODE has been applied to the multi-objective structural design optimization for MRJ H-Tail n Including detailed buckling evaluation n Improved both of weight and number of main structure parts compared with the baseline design n Provided a better design concept utilized for MRJ H- Tail structural design

16 Stay tuned for the first flight in 2013!