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AIAA Aviation Forum

作者： Djeddi, Reza Ekicit, Kivanc Univ Tennessee Dept Mech Aerosp & Biomed Engn Knoxville TN 37996 USA

ISBN: (数字)9781624105982

ISBN: (纸本)9781624105982

A computationally efficient "one-shot" approach with a low memory footprint is presented for unsteady design optimization. The proposed technique is based on a novel and unique approach that combines "local-in-time" and fixed-point iteration methods to advance the unconverged primal and adjoint solutions forward and backward in time to evaluate the sensitivity of the globally time-integrated objective function. This is in some ways similar to the "piggyback" iterations where primal and adjoint solutions are evaluated at a frozen design. During each cycle, the primal, adjoint, and design update problems are solved to advance the optimization problem. This new coupled approach is shown to provide significant savings in the memory footprint while reducing the computational cost of primal and adjoint evaluations per design cycle. The method is first applied to an inverse design problem for the unsteady lid-driven cavity. Following this, vortex suppression and mean drag reduction for a circular cylinder in cross-flow is considered. Both of these objectives are achieved by optimizing the rotational speeds for steady or periodically oscillating excitations. For all cases presented in this work, the proposed technique is shown to provide significant reductions in memory as well as computational time. It is also shown that the unsteady design optimization problem converges to the same optimal solution obtained using a conventional approach.

关键词： Karman Vortex Street Aerodynamic Shape Optimization Magnus Effect Computational Fluid Dynamics sequential quadratic programming Navier Stokes Equations Optimal Control Incompressible Flow Lagrange Multipliers High Performance Computing

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GRADIENT-BASED SOLUTION FOR HYBRID PRECODING IN MIMO SYSTEMS

GRADIENT-BASED SOLUTION FOR HYBRID PRECODING IN MIMO SYSTEMS

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IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Zanjani, Negin Bakhshi Khademi, Seyran Leus, Geert Delft Univ Technol Fac EIect Engn Math & Comp Sci Delft Netherlands

ISBN: (纸本)9781509041176

The combination of base band and analog precoding for multiple-input multiple-output (MIMO) systems is considered in this paper which is referred to as hybrid precoding. The system capacity, as a design criterion, is maximized subject to unit modulus constraints on the elements of the analog precoder (phase shifters), and a total power constraint. This is a non-convex problem due to the product of the analog and baseband precoder variables. The proposed technique suggests computing non-trivial complex derivatives of the objective and constraints, analytically, in order to develop an iterative gradient-based sequential optimization algorithm to solve the non-convex problem. Promising simulation results show that the solution of the proposed algorithm is sufficiently close to the optimal (full-baseband) precoder solution, regardless of the channel characteristics.

关键词： multiple-input multiple-output (MIMO) hybrid precoding non linear optimization sequential quadratic programming

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Autonomous Reference Orbit Refinement for Optimal Swarm Reconfiguration

Autonomous Reference Orbit Refinement for Optimal Swarm Reco...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Lippe, Corinne D'Amico, Simone Stanford Univ Aeronaut & Astronaut Durand Bldg 496 Lomita Mall Stanford CA 94305 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

This work presents a novel approach to minimizing delta-v consumption for spacecraft swarm reconfiguration through reference orbit refinement in near-circular orbits. Given a desired relative motion configuration, the optimal real or virtual chief spacecraft's orbit refinement is solved for to provide minimum delta-v expenditure. Relative orbital elements (ROE) are leveraged to produce two quadratically constrained linear programs (QCLPs). One program minimizes the sum of delta-v usage across the swarm, and the second minimizes the maximum delta-v usage among the swarming spacecraft. These two programs are designed to reduce swarm delta-v usage to extend mission lifetime. Furthermore, both optimization programs can be solved efficiently with interior point methods. While the two minimizations apply to any ROE set, the quasi-nonsingular ROE are exploited in this work to produce analytical solutions for arbitrary relative motion reconfigurations in non-equatorial orbits. If analytical solutions are not available, guidance is provided to reduce the effort required by convex optimization solvers in finding solutions. Delta-v savings enabled by the virtual or real chief spacecraft's orbit refinement on the order of cm/s to m/s are demonstrated using a state-of-the-art solver that produces the minimum reachable delta-v for a given reconfiguration. Therefore, leveraging a small refinement in the reference orbit for swarm reconfiguration through a QCLP can provide significant delta-v savings, extending mission lifetime.

关键词： Equatorial Orbit Spacecraft Orbits Convex Optimization Orbital Elements sequential quadratic programming National Science Foundation Six Degree of Freedom State Dependent Riccati Equation Argument of Latitude Fuel Consumption

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Design of airfoils in unsteady viscous flows using Hierarchical Kriging model 55

Design of airfoils in unsteady viscous flows using Hierarchi...

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55th AIAA Aerospace Sciences Meeting

作者： Song, Chao Yang, Xudong Song, Wenping National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University Xi’anShaan Xi710072 China School of Aeronautics China

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

In this paper, optimizations are carried out to determine an airfoil shape with the best aerodynamic performance in the unsteady low Reynolds flow. To capture the unsteady physics driving the design process, the time-accurate Navier-Stokes equations are solved for aerodynamic performance. The Hierarchical Kriging (HK) model is used due to its high efficiency in the process of building a model and ability in searching global optimal. The influence of different low-fidelity (L-F) models and infilling strategies on the optimization efficiency is investigated. It is found that an extremely coarse mesh would be an excellent L-F model, which is a suitable balance between accuracy and computational cost. By taking the advantage of the hybrid infilling strategy, the optimization converges rapidly without initial design of experiment for the high-fidelity (H-F) model. The design approach proposed in this paper allows highly efficient aerodynamic optimizations in unsteady low Reynolds number flow, at the same time global optimum can be surely guaranteed. © 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Kriging Model Separated Flows Lift to Drag Ratio Aerodynamic Shape Optimization Design of Experiments Unmanned Aerial Vehicle Vortex Shedding sequential quadratic programming Aerodynamic Performance Surrogate Model

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Three-dimensional subdivision parameterisation for aerodynamic shape optimisation 55

Three-dimensional subdivision parameterisation for aerodynam...

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55th AIAA Aerospace Sciences Meeting

作者： Masters, D.A. Taylor, N.J. Rendall, T.C.S. Allen, C.B. Department of Aerospace Engineering University of Bristol BristolBS8 1TR United Kingdom MBDA UK Ltd WG3 PO Box 5 Filton BristolBS34 7QW United Kingdom

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

A novel hierarchical wing parameterisation method based on subdivision surfaces is presented and its performance tested on a range of geometric and aerodynamic optimisation test cases. Subdivision surfaces form a limit surface based on the recursive refinement of an initial network of points. This intrinsically creates a hierarchy of control points that can be used to deform the surface at varying degrees of fidelity. This principle is used to create a multi-resolutional surface parameterisation that can make fine and gross surface changes without losing underlying surface detail. This is then extended to allow multi-resolutional control of arbitrary meshes such as computational surface grids. This parameterisation method is then applied to a range of optimisation problems in a ‘multi-level’ procedure that starts with a low fidelity parametrisation and which is then increased sequentially. These cases are compared against a range of ‘single-level’ schemes that use each level in isolation. It was found that by using the multi-level method significant improvements to both convergence rates and robustness were achieved. In some cases this increased robustness lead to improved final results by successfully exploiting high dimensional design spaces that could not be explored using a fixed number of design variables. © 2017 by Dominic Masters, Nigel Taylor, Thomas Rendall, Christian Allen.

关键词： Aerodynamic Shape Optimization Lift Coefficient B Splines Aspect Ratio sequential quadratic programming Computer Aided Design Computer Animation Surface Roughness Flow Conditions Wing Geometry

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Motion Planning for Vibration Reducing of Free-floating Redundant Manipulators Based on Hybrid Optimization Approach

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Chinese Journal of Aeronautics 2011年第4期24卷 533-540页

作者： LIAO Yihuan LI Daokui TANG Guojin College of Aerospace and Materials Engineering National University of Defense Technology Changsha 410073 China

This paper is concerned with optimal motion planning for vibration reducing of free-floating flexible redundant manipulators. Firstly, dynamic model of the system is established based on Lagrange method, and the motion planning model for vibration reducing is proposed. Secondly, a hybrid optimization approach employing Gauss pseudospectral method （GPM） and direct shooting method （DSM）, is proposed to solve the motion planning problem. In this approach, the motion planning problem is transformed into a non-linear parameter optimization problem using GPM, and genetic algorithm （GA） is employed to locate the approximate solution. Subsequently, an optimization model is formulated based on DSM, and sequential quadratic programming （SQP） algorithm is used to obtain the accurate solution, with the approximate solution as an initial reference solution. Finally, several numerical simulations are investigated, and the global vibration or residual vibration of flexible link is obviously reduced by the joint trajectory which is obtained by the hybrid optimization approach. The numerical simulation results indicate that the approach is effective and stable to the motion planning problem of vibration reducing.

关键词： flexible manipulator dynamic modeling motion planning Gauss pseudospectral method direct shooting method genetic algorithm sequential quadratic programming

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Restricted snakes: A flexible topology parameterisation method for aerodynamic optimisation 55

Restricted snakes: A flexible topology parameterisation meth...

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55th AIAA Aerospace Sciences Meeting

作者： Payot, A.D.J. Rendall, T.C.S. Allen, C.B. Department of Aerospace Engineering University of Bristol BristolBS8 1TR United Kingdom

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

This paper presents the development of a novel parameterisation method for aerodynamics which allows topological flexibility. This new parameterisation method builds geometries using restricted snakes to recover Volume Of Solid (VOS) data under a minimum length constraint. Geometric inverse design results are presented showing the ability of the parameterisation to recover a range of aerodynamic shapes to a set tolerance. The Aerodynamic Design Optimization Discussion Group (ADODG) Eulerian drag minimisation of the NACA 0012 (case 1) was attempted using a conjugate gradient optimiser leading to a drag coefficient of 66 counts. Results of supersonic drag minimizations under an area constraint were compared against known linear optima, showing equivalent or better aerodynamic performance in all cases. The topological flexibility of the parametrisation allowed reductions in drag of 80% compared to the Busemann biplane, a multiplane profile predicted to have no wave drag at supersonic speed by linear theory. © 2017 by A. D. J. Payot;T. C. S. Rendall;C. B. Allen.

关键词： Aerodynamic Shape Optimization NACA 0012 Aerodynamic Performance Geometric Tolerances Supersonic Speed sequential quadratic programming Computational Fluid Dynamics Supersonic Flow Commercial Aircraft Computational Structural Dynamics

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A standard platform for testing and comparison of MDAO architectures 53

A standard platform for testing and comparison of MDAO archi...

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53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 2012

作者： Gray, Justin Moore, Kenneth T. Hearn, Tristan A. Naylor, Bret A. NASA Glenn Research Center Cleveland OH United States

ISBN: (数字)9781600869372

ISBN: (纸本)9781600869372

The Multidisciplinary Design Analysis and Optimization (MDAO) community has developed a multitude of algorithms and techniques, called architectures, for performing optimizations on complex engineering systems which involve coupling between multiple discipline analyses. These architectures seek to effciently handle optimizations with computationally expensive analyses including multiple disciplines. We propose a new testing procedure that can provide a quantitative and qualitative means of comparison among architectures. The proposed test procedure is implemented within the open source framework, OpenMDAO, and comparative results are presented for five well-known architectures: MDF, IDF, CO, BLISS, and BLISS-2000. We also demonstrate how using open source soft- ware development methods can allow the MDAO community to submit new problems and architectures to keep the test suite relevant.

关键词： Open Source Software Application programming Interface sequential quadratic programming Computational Fluid Dynamics Finite Element Analysis Design of Experiments Black Box Conjugate Gradient Algorithm Piston Engine Aeronautics

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Timetable Generator for Educational Institute Using Genetic Algorithm 3

Timetable Generator for Educational Institute Using Genetic ...

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3rd International Conference on Technological Advancements in Computational Sciences, ICTACS 2023

作者： Bhatt, Chandradeep Chaurasiya, Divyanshu Chauhan, Rahul Singh, Teekam Sharma, Sanjay Baloni, Dev Graphic Era Hill University Cse Department Dehradun India Graphic Era Hill University Computer Science and Engineering Dehradun India Graphic Era Deemed to Be University Computer Science and Engineering Dehradun India Sgrr Univeristy Computer Application Department Dehradun India Quantum University Computer Science and Engineering Dehradun India

ISBN: (纸本)9798350342338

Genetic algorithms are effectively capable to find out solution of a variety of challenging actual situations. They are heuristic search and optimization methods influenced by natural evolution. The process of making a schedule has been quite time- and labor-intensive. To create a schedule, a lot of time and effort must be invested. Timetables are produced for a wide range of reasons, including class scheduling at educational institutions, developing timing charts for buses and trains, and many more. A schedule requires a lot of effort and time to create. In our research, we tried to reduce the difficulties of generating a schedule using a genetic approach. We may create timetables that are quicker to create while still being more precise, exact, and error-free by using genetic algorithms. © 2023 IEEE.

关键词： Artificial Neural Network Genetic Algorithms Heuristic Search Recurrent Neural Network sequential quadratic programming

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Optimal multi-target Lambert rendezvous

Optimal multi-target Lambert rendezvous

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AIAA/AAS Astrodynamics Specialist Conference, 2016

作者： Bang, Jun Ahn, Jaemyung Korea Advanced Institute of Science and Technology Department of Aerospace Engineering Daejeon305-701 Korea Republic of

ISBN: (数字)9781624104459

ISBN: (纸本)9781624104459

The solution methodology for solving a general multi-target Lambert rendezvous optimization problem is proposed in this paper. The purpose of optimization is to find the optimal visiting sequence and trajectory that minimize the velocity increment to complete all rendezvous maneuvers. The problem is mathematically formalized by applying a hybrid optimal control framework. A novel approach using a gradient-based algorithm to find a set of local minima for single-target Lambert rendezvous is developed. Then, a scheme that sequentially combines the sets of local minima to obtain the global solution of multi-target Lambert rendezvous for a given sequence is introduced. Experimental studies are conducted to demonstrate the validity of the proposed methods. The results show that the proposed scheme is successfully worked as an inner-loop solver and ensures the consistent optimal solution. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Optimal Control Theory Asteroids Particle Swarm Optimization Nonlinear programming Interplanetary Mission Orbital Elements sequential quadratic programming Aerospace Engineering Genetic Algorithm Lambert's Problem

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