Gradient-based shape optimisation of conformal array antennas

2010 ◽  
Vol 4 (2) ◽  
pp. 200 ◽  
Author(s):  
P. Jacobsson ◽  
T. Rylander
Keyword(s):  
Shape Optimisation ◽  
Conformal Array ◽  
Array Antennas ◽  
Gradient Based

scholarly journals Shape and excitation optimization for conformal array antennas

Radio Science ◽  
2008 ◽  
Vol 43 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
T. Halleröd ◽  
T. Rylander
Keyword(s):  
Conformal Array ◽  
Array Antennas

Adjoint-based aerodynamic drag minimisation with trim penalty

2021 ◽  
pp. 1-25
Author(s):  
S. Shitrit
Keyword(s):  
Drag Reduction ◽  
Aerodynamic Drag ◽  
Lift Coefficient ◽  
Free Form ◽  
Shape Optimisation ◽  
Control Points ◽  
Aerodynamic Shape ◽  
Design Variables ◽  
Gradient Based ◽  
Mesh Warping

Abstract The aerodynamic performance of conventional aircraft configurations are mainly affected by the wing and horizontal tail. Drag reduction by shape optimisation of the wing, while taking into account the aircraft trimmed constraint, has more benefit than focusing solely on the wing. So in order to evaluate this approach, the following study presents results of a single and multipoint aerodynamic shape optimisation of the wing-body-tail configuration, defined by the Aerodynamic Design Discussion Group (ADODG). Most of the aerodynamic shape optimisation problems published in the last years are focused mainly on the wing as the main driver for performance improvement, with no trim constraint and/or excess drag obtained from the fuselage, fins or other parts. This work partially fills this gap by an investigation of RANS-based aerodynamic optimisation for transonic trimmed flight. Mesh warping and geometry parametrisation is accomplished by fitting the multi-block structured grid to a B-spline volumes and performing the mesh movement by using surface control points embedded within the free-form deformation (FFD) volumes. A gradient-based optimisation algorithm is used with an adjoint method in order to compute the derivatives of the objective and constraint functions with respect to the design variables. In this work the aerodynamic shape optimisation of the CRM wing-body-tail configuration is investigated, including a trim constraint that is satisfied by rotating the horizontal tail. The shape optimisation is driven by 432 design variables that envelope the wing surface, and 120 shape variables for the tail, as well as the angle of attack and tail rotation angles. The constraints are the lift coefficient, wing’s thickness controlled by 1,000 control points, and the wing’s volume. For the untrimmed configuration the drag coefficient is reduced by 5.76%. Optimising the wing with a trim condition by tail rotation results in shock-free design with a considerably improved drag, even better than the untrimmed-optimised case. The second optimisation problem studied is a single and multi-point lift constraint drag minimisation of a gliding configuration wing in transonic viscous flow. The shock is eliminated, reducing the drag of the untrimmed configuration by more than 60%, using 192 design variables. Further robustness is achieved through a multi-point optimisation with more than 45% drag reduction.

scholarly journals Single and multi–objective UAV aerofoil optimisation via hierarchical asynchronous parallel evolutionary algorithm

2006 ◽  
Vol 110 (1112) ◽  
pp. 659-672 ◽  
Author(s):  
L. F. Gonzalez ◽  
D. S. Lee ◽  
K. Srinivas ◽  
K. C. Wong
Keyword(s):  
Traditional Approach ◽  
Global Solutions ◽  
Shape Optimisation ◽  
Test Cases ◽  
Navigation Systems ◽  
Local Optima ◽  
Multi Objective ◽  
Gradient Based ◽  
Parallel Evolutionary Algorithm ◽  
Operational Envelope

Abstract Unmanned aerial vehicle (UAV) design tends to focus on sensors, payload and navigation systems, as these are the most expensive components. One area that is often overlooked in UAV design is airframe and aerodynamic shape optimisation. As for manned aircraft, optimisation is important in order to extend the operational envelope and efficiency of these vehicles. A traditional approach to optimisation is to use gradient-based techniques. These techniques are effective when applied to specific problems and within a specified range. These methods are efficient for finding optimal global solutions if the objective functions and constraints are differentiable. If a broader application of the optimiser is desired, or when the complexity of the problem arises because it is multi-modal, involves approximation, is non-differentiable, or involves multiple objectives and physics, as it is often the case in aerodynamic optimisation, more robust and alternative numerical tools are required. Emerging techniques such as evolutionary algorithms (EAs) have been shown to be robust as they require no derivatives or gradients of the objective function, have the capability of finding globally optimum solutions among many local optima, are easily executed in parallel, and can be adapted to arbitrary solver codes without major modifications. In this paper, the formulation and application of a evolutionary technique for aerofoil shape optimisation is described. Initially, the paper presents an introduction to the features of the method and a short discussion on multi-objective optimisation. The method is first illustrated on its application to mathematical test cases. Then it is applied to representative test cases related to aerofoil design. Results indicate the ability of the method for finding optimal solutions and capturing Pareto optimal fronts.

The Research of DOA Estimation Algorithms in the Conformal Array Antenna

2015 ◽  
Vol 743 ◽  
pp. 471-473
Author(s):  
C.Z. Sun
Keyword(s):  
Doa Estimation ◽  
Array Antenna ◽  
Signal Subspace ◽  
Music Algorithm ◽  
Estimation Algorithms ◽  
Conformal Array ◽  
Array Antennas ◽  
Peak Search ◽  
Simulation Results ◽  
Rayleigh Limit

To the conformal array antennas, the conventional DOA estimation algorithms will be affected by the Rayleigh limit. While, the MUSIC algorithm can solve this problem, it fully utilizes the orthogonality of noise subspace and signal subspace. It can achieve the DOA estimation through the spectrum peak search. The MUSIC algorithm is analyzed. Based on the cylindrical and conical array antenna, the algorithms are simulated. The simulation results show that the array arrangement mode can exert an important influence on the DOA estimation.

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