Analysis of some global optimization algorithms for space trajectory design

In this paper, we analyze the performance of some global search algorithms on a number of space trajectory design problems. A rigorous testing procedure is introduced to measure the ability of an algorithm to identify the set of ²-optimal solutions. From the analysis of the test results, a novel algorithm is derived. The development of the novel algorithm starts from the redefinition of some evolutionary heuristics in the form of a discrete dynamical system. The convergence properties of this discrete dynamical system are used to derive a hybrid evolutionary algorithm that displays very good performance on the particular class of problems presented in this paper

An inflationary differential evolution algorithm for space trajectory optimization

In this paper we define a discrete dynamical system that governs the evolution of a population of agents. From the dynamical system, a variant of Differential Evolution is derived. It is then demonstrated that, under some assumptions on the differential mutation strategy and on the local structure of the objective function, the proposed dynamical system has fixed points towards which it converges with probability one for an infinite number of generations. This property is used to derive an algorithm that performs better than standard Differential Evolution on some space trajectory optimization problems. The novel algorithm is then extended with a guided restart procedure that further increases the performance, reducing the probability of stagnation in deceptive local minima.Comment: IEEE Transactions on Evolutionary Computation 2011. ISSN 1089-778

Aerodynamic optimization of a large PrandtlPlane configuration

The purpose of this paper is to present design procedures and tools for the aerodynamic optimization of a large freighter aircraft with a PrandtlPlane configuration. Suitable optimization tools have been developed and are shortly described in the paper; sensitivity analyses for high speed flight conditions have been performed, and, also, low speed performances are evaluated to provide a complete preliminary design of the PrandtlPlane freighter

On testing global optimization algorithms for space trajectory design

In this paper we discuss the procedures to test a global search algorithm applied to a space trajectory design problem. Then, we present some performance indexes that can be used to evaluate the effectiveness of global optimization algorithms. The performance indexes are then compared highlighting the actual significance of each one of them. A number of global optimization algorithms are tested on four typical space trajectory design problems. From the results of the proposed testing procedure we infer for each pair algorithm-problem the relation between the heuristics implemented in the solution algorithm and the main characteristics of the problem under investigation. From this analysis we derive a novel interpretation of some evolutionary heuristics, based on dynamical system theory and we significantly improve the performance of one of the tested algorithms

Deterministic chaos produced by local optimisation algorithms

Deterministic chaos situations produced by local optimisation algorithms are considered. A family of test multi‐extremal functions is proposed that allows getting the collections of functions with an arbitrary pre‐defined number of the local optima. Special software is developed for generating test functions from the family, performing multiple local optimisations of different initial points, visualising the chaotic attraction regions. Properties of the regions of attraction are presented. Regularity of the attraction regions is required to be a special characteristic of the local optimisation algorithms. Apibrėžto chaoso suformavimas lokaliaisiais optimizavimo algoritmais Santrauka Straipsnyje nagrinėjamos lokaliųjų optimizavimo algoritmų suformuotos apibrėžto chaoso situacijos. Pasiūlyta daugiaekstreminių funkcijų šeima, kuri leidžia nustatyti iš anksto pasirinktų lokaliųjų opmimumų reikšmes. Sukurta speciali programinė įranga, kuri iš funkcijų šeimos kuria testavimo funkcijas, atlieka kartotinį lokalinį optimizavimą pagal įvairius pradinius taškus ir vaizduoja chaoso zonas. Pateikos tų zonų savybės. Zonų taisyklingumas lemia lokaliojo optimizavimo algoritmų ypatybes. First Published Online: 21 Oct 2010 Reikšminiai žoidžiai: globalusis ir lokalusis optimizavimas, chaoso zona, apibrėžtas chaosas

Modeling supersonic heated jet noise at fixed jet Mach number using an asymptotic approach for the acoustic analogy Green’s function and an optimized turbulence model

In this study we show how accurate jet noise predictions can be achieved within Goldstein’s generalized acoustic analogy formulation for heated and un-heated supersonic jets using a previously developed asymptotic theory for the adjoint vector Green’s function and a turbulence model whose independent parameters are determined using an optimization algorithm . In this approach, mean flow non-parallelism enters the lowest order dominant balance producing enhanced amplification at low frequencies, which we believe corresponds to the peak sound at small polar observation angles. The novel aspect of this paper is that we exploit both mean flow and turbulence structure from existent Large Eddy Simulations database of two axi-symmetric round jets at fixed jet Mach number and different nozzle temperature ratios to show (broadly speaking) the efficacy of the asymptotic approach. The empirical parameters that enter via local turbulence length scales within the algebraic-exponential turbulence model are determined by optimizing against near field turbulence data post-processed from the LES calculation. Our results indicate that accurate jet noise predictions are obtained with this approach up to a Strouhal number of 0.5 for both jets without introducing significant empiricism