multi-objective optimization coupling modefrontier and · pdf filea. clarich, z. wen* esteco,...
TRANSCRIPT
A. Clarich, Z. Wen* ESTECO, Trieste, (Italy)
Multi-objective optimization coupling modeFRONTIER and CST MICROWAVE STUDIO
Summary
• Introduction to modeFRONTIER
• CST direct interface in modeFRONTIER
• Application case: optimization of wideband antenna
• Application case: optimization of Power Data Handling and Transmission (PDHT) antenna
Introducing modeFRONTIER
is an integration platform for multi-objective optimization, automation of design processes
and analytic decision making providing seamless coupling with engineering tools
within various disciplines
User’s Community and short company history ESTECO started in 1999 as a University spin-off.
modeFRONTIER was the first commercial tool that allowed a MULTI-OBJECTIVE
optimization applied to ANY engineering design area
Now modeFRONTIER is used worldwide
1999 2001 2003 2004 2008 2010 2013
modeFRONTIER v. 1
Esteco establishment
in Europe
modeFRONTIER v. 2
Expansion to Asian markets
modeFRONTIER v. 3
Opening of ESTECO
North America
modeFRONTIER v. 4
modeFRONTIER v. 5
Automotive
Research Inst. and Uni
Electronics
Aerospace
Energy
Materials
Appliances
Defence and Space
No
Yes
OK?
Initial Configuration
Simulate
Evaluate Results
Accept
Modify Configuration
Traditional Design Optimization Approach
Parametric models
Design Objectives and Constraints
Optimal trade-off Solution
The Concept behind modeFRONTIER
The Concept behind modeFRONTIER
The Black Box: (ADAMS, ANSYS, CST, GT-Suite, etc.)
Scheduler: (DOE, optimization algorithms,..)
Input Variables: Entities defining the design space.
Output Variables: Measures from the
system
modeFRONTIER can be coupled with most software (CAD, CAE or general application tools) and it enables the simultaneous use of a number of such software packages even
on different machines
Modules of modeFRONTIER
Process Integration
Statistical Analysis Multivariate Analysis Decision Making Response Surface Tool
Design of Experiments Optimization Algorithms Robust Design
CST interface in modeFRONTIER
• Existing I/O parameters are automatically introspected and listed after clicking apposite space
• Assign each one of them to mF workspace parameters
CST interface in modeFRONTIER
CST direct interface Preferences
• CST application can be selected
• CST solver can be specified
Application Examples:
1) Maximizing bandwidth for a wideband antenna with modeFRONTIER
2) Multi-objective optimization of an isoflux Antenna
from: F.Franchini, Multi-objectives optimization coupling modeFRONTIER and CST MICROWAVE STUDIO®, CST Workshop Series 2013 - 14 March 2013, Ankara, Turkey
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• Wideband antenna for mobile communications, e.g. in base stations
• Antenna performance is measured by return loss (low return loss desirable)
• Aim: design antenna with low return loss over the largest frequency range possible
– S11 - parameter used, equivalent to return loss
• Bandwidth for nominal design is 2.1 GHz
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Application example: Maximizing bandwidth for a wideband antenna
Results 1/2
• Bandwidth increased by 15% compared to original model
– Nominal design violated design constraint of S11 < -4.5 dB in range
– Automated process for antenna design created – Two-step optimization approach
Original design Final design
Bandwidth = 2.13 GHz Bandwidth = 2.43 GHz
S11 peak to -4.3 dB (above limit!) S11 peak below limit
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Engineering design process captured:
Easy adaptation for future projects (more parameters, different antenna model, additional result quantities …)
Relationship between input parameters and results clarified
Engineering time
CPU time
Defining modeFRONTIER workflow 1h
First optimization step (finding a starting point, 30 simulations, 20 minutes each): 10 h
Evaluation first step 30 min Second optimization step (20 simulations, 45 minutes each): 15 h
Evaluation of results 1 h
Total 2.5 h 25 h
Total time for project 1,5 days
Results 2/2
Estimated time to carry out a similar project
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PDHT Antenna Description • The Power Data Handling and Transmission (PDHT) antennas
are basic payloads on Low Earth Orbit (LEO) satellites. • These antennas play an important role in many mission of
earth Observation from Space, where high transmission rate is required to acquire Earth images in various spectral bands for several civilian and military applications.
• The basic PDHT Antenna architecture was developed more than ten years ago and It consists of a corrugated planar surfaces with cylindrical symmetry excited by quartz loaded launcher, so that the analysis is based on 2D Method of Moment Modeling, while the optimization is performed by a quasi-Newton technique.
F. Franchini, N.Baldecchi Enginsoft SpA, Firenze, Italy C. Iannicelli, Software System Engineering SpA, Roma, Italy
R. Ravanelli, Thales Alenia Italia SpA, Roma, Italy
Application example: Multi-objective optimization of an isoflux Antenna
PDHT Antenna Description
The new PDHT Antenna Structure conceived to meet new and more stringent requirements especially on cross-polarization discrimination XPD and operative frequency bandwidth has sets of slots in radial direction: 3D modeling is necessary with much more computation resources to perform electromagnetic analysis The slots are variables in number and geometry. New multi-objective evolutionary algorithms are required because of the new multi-variable and multi-objective nature of optimization problem
Electromagnetic Problem Formulation
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90Theta (degs)
Am
plitu
de (
dBi)
MinimumGainMask
MaximumGainMask
R1
DR1 R2
DR2
DR….
DRn
R…
Rn
A2
A… An
D2
D…
Dn
A1
• Radio Frequency requirements are fixed on: • Gain achievement on desired mask defined on elevation angular range • Cross Polar Discrimination (XPD) on required angular and frequency • Amplitude and Phase Ripple with respect of required frequency • Return Loss requirement
• The Antenna Structure is described by a set of geometrical parameters
• The Antenna Performances Optimization consists in defining the best combination of geometrical variables
Minimum Gain Mask Maximum Gain Mask
Optimization Methodology
• First step: Design of Experiments (DOE) in modeFRONTIER and sensitivity analysis to reduce the variables from 100 to 25 variables
• Second step: Optimization phase performed by Genetic Algorithm and Game Theory on the reduced variables space
DOE – Sensitivity Analysis
• Uniform Latin Hypercube DOE approach allow to generate a set of uncorrelated designs in input such to avoid linear correlation between them.
• Sensitivity Analysis has been performed in order to better understand I/O correlations, and to reduce the optimization problem dimension
Optimization strategy
• A first screening of design space has been implemented combining the current DOE with MOGT (Game Theory algorithm)
• Starting from the Pareto Frontier of MOGT step, MOGAII (Multi –objective Genetic Algorithm) has been applied to extend the set of optimum solutions
• A good compromise of the most important requirements (Gain and XPD) has been found
Discussion of results 1/2
• Comparing the results between optimized design and original design the following improvements have been achieved: • Improvement of the gain at ±62°
(6.6 dB vs. 6 dB);
• The pattern widening on the enlarged coverage has been achieved so that the antenna can be used for the lower satellite position with 70 degs field of view;
• The XPD improve of 7 dB passing from 5 dB to 12 dB;
BASELINE
OPTIMIZED
Discussion of results 2/2
• The amplitude ripple in band of interest has been satisfied with 1 dB (peak to peak) variation. The new solution presents a equalized copular pattern over a large frequency bandwidth;
• The phase ripple in band of interest is satisfied with 3 deg (peak to peak) variation;
Conclusion
• The presentation highlights the powerful capabilities of modeFRONTIER couple with CST MICROWAVE STUDIO in the antenna development process (Optimization)
• In modeFRONTIER any numerical model can be integrated in the process, and a large variety of multi-objective optimization algorithms and pre/post-processing tools are available
Thank you!
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