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Optimal Control of a Librating Electrodynamic Tether Performing a Multirevolution Orbit Change

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2009年第5期32卷 1497-1507页

作者： Stevens, Robert E. Baker, William P. USN Acad Dept Aeronaut & Astronaut Annapolis MD 21402 USA USAF Inst Technol Dept Math & Stat Wright Patterson AFB OH 45433 USA

Satellites that use low-thrust propulsion systems for maneuvering, although efficient, can take a long time to complete significant orbit changes. Determining the nonlinear optimal controls for such multirevolution maneuvers using the instantaneous orbital state dynamics can he riddled with numerical errors and are often subject to long computation times, due to the large number of discretization nodes required by thea* optimization algorithm. An approach to optimal control of an electrodynamic tether is examined using averaged orbital state dynamics as constraints instead of instantaneous dynamic constraints. A mean-square libration state is introduced in the dynamic model that captures the average of the out-of-plane libration of the tether. A sample long-term optimal orbit change maneuver of a librating electrodynamic tether subject to atmospheric drag is investigated. The method of averaging is employed to transform the optimal control problem from the time domain into Fourier space, in which the complex problem is significantly reduced to a Zermelo-type problem that is solved using a pseudospectral method. To validate the dynamic model of averaged states, the instantaneous states are propagated from the initial conditions using the resulting optimal controls.

关键词： Covector Mapping Principle Electrodynamic Tether Satellites Atmospheric Drag Pseudospectral Methods optimization algorithm Low Thrust Propulsion Earth Low Thrust Maneuvers Aerodynamic Torque

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Path Planning algorithms for Skid-to-Turn Unmanned Aerial Vehicles

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2009年第5期32卷 1531-1543页

作者： Yokoyama, Nobuhiro Ochi, Yoshimasa Natl Def Acad Dept Aerosp Engn Yokosuka Kanagawa 2398686 Japan

. This study describes two types of algorithms for skid-to-turn unmanned aerial vehicles to plan paths between two waypoints under constant wind conditions. The first type of algorithm is a rigorousa* optimization algorithm based on the Euler-Lagrange formulation with analytical integration of the path. The second type of algorithm is a fast algorithm describing the path by two circular arcs connected by a line segment or another circular are in the air mass frame, which is similar to the Dubins path. The latter algorithm is developed for actual airborne application, whereas the former algorithm is developed to check the quasi-optimality of the path calculated by the latter algorithm. We present a convergence proof of the latter algorithm under certain assumptions and its quasi-optimality in comparison with the former algorithm. Furthermore, the computational efficiency and the convergence reliability of the latter algorithm are demonstrated through numerical examples.

关键词： Bank to Turn Path Planning UAV optimization algorithm Airspeed Bang Bang Control Angle of Attack Sideslip Angle Control Surfaces Global Positioning System

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A Semi-Automated Dynamic Approach to Threat Evaluation and Optimal Defensive Resource Allocation

A Semi-Automated Dynamic Approach to Threat Evaluation and O...

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5th International Conference on Intelligent Computing

作者： Naeem, Huma Masood, Asif Hussain, Mukhtar Khan, Shoab A. Natl Univ Sci & Tehcnol Dept Comp Sci Mil Coll Signals Rawalpindi Punjab Pakistan Natl Univ Sci & Technol Coll Elect & Mech Engn Dept Comp Sci Islamabad Pakistan

ISBN: (纸本)9783642040696

This paper presents a decision support based, dynamic approach to optimal threat evaluation and defensive resource scheduling. The algorithm provides flexibility and optimality by swapping between two objective functions, based on preferential and subtractive defense strategies, as and when required. Analysis part of this paper presents the strengths and weaknesses of the proposed algorithm over an alternative greedy algorithm as applied to different offline scenarios.

关键词： Automated Threat Evaluation (TE) and Weapon Assignment (WA) - (TEWA) optimization algorithm Decision Support System Artificial intelligence - Cybernetics application preferential/subtractive defense strategies DA based weapon allocation

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An entropy-based model to support QoS multicast routinga* optimization algorithm for mobile ad hoc networks

An entropy-based model to support QoS multicast routing opti...

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International Conference on Wireless Communications, Networking and Mobile Computing

作者： Sun, BL Li, LY Chen, H Wuhan Univ Technol Sch Comp Sci & Technol Wuhan 430063 Peoples R China

ISBN: (纸本)078039335X

A Mobile Ad hoc NETwork (MANET) is an autonomous system of mobile nodes connected by wireless links. There is no static infrastructure such as base station as that was in cell mobile communication. Due to the dynamic nature of the network topology and restricted resources, quality of service (QoS) and multicast routing in MANET is a challenging task. In this paper, we present an entropy-based model to support QoS multicast routinga* optimization algorithm in mobile ad hoc networks (EQMOA). The basic motivations of the proposed modeling approach stem from the commonality observed in the location uncertainty in mobile ad hoc wireless networks and the concept of entropy. The simulation results demonstrate that the proposed approach and parameters provide an accurate and efficient method of estimating and evaluating the route stability in dynamic mobile networks.

关键词： ad hoc network entropy multicast routing optimization algorithm

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A distributed entropy-based QoS multicast routinga* optimization algorithm for MANET

A distributed entropy-based QoS multicast routing optimizati...

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6th International Conference on Parallel and Distributed Computing, Applications and Technologies (PDCAT 2005)

作者： Gui, C Sun, BL Hubei Univ Econ Dept Comp & Elect Sci Wuhan 430205 Peoples R China

ISBN: (纸本)0769524052

A Mobile Ad hoc NETwork (MANET) is an autonomous system of mobile nodes connected by wireless links There is no static infrastructure such as base station as that was in cell mobile communication. Due to the dynamic nature of the network topology and restricted resources, quality of service (QoS) and multicast routing in MANET is a challenging task In this paper, we present an entropy-based model to support QoS multicast routinga* optimization algorithm in mobile ad hoc networks (EQMOA). The basic motivations or the proposed modeling approach stem from the commonality observed in the location uncertainty in mobile ad hoc wireless networks and the concept of entropy. The simulation results demonstrate that the proposed approach and parameters provide an accurate and efficient method of estimating and evaluating the route stability in dynamic mobile networks.

关键词： Ad Hoc network QoS multicast routing entropy optimization algorithm

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Aerodynamic optimization of essentially three-dimensional shapes for wing-body fairing

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AIAA JOURNAL 2008年第7期46卷 1814-1825页

作者： Peigin, Sergey Epstein, Boris Israel Aerosp Ind Ltd IL-70100 Ben Gurion Israel Acad Coll Tel Aviv Yaffo IL-64044 Tel Aviv Israel

A new approach for the optimization of essentially three-dimensional aerodynamic shapes for minimum drag is proposed. The method allows the handling of the nonlinear surfaces that are typical of complex aircraft junctions such as a wing-body fairing. The optimization framework OPTIMAS, previously proposed and developed by the authors for the solution of the drag-minimization problem for two-dimensional airfoils, three-dimensional isolated wings, and three-dimensional wings in the presence of a body in succession, is extended in this paper to a significantly higher level of geometrical complexity of optimized aerodynamic configurations. The method is driven by accurate full Navier-Stokes evaluations of the objective function, and the optimization engine is based on genetic algorithms. The important features of the method are the ability to accurately handle multiple geometrical/aerodynamic constraints and a high level of computational efficiency, achieved through massive multilevel parallelization and a reduced-order-model approach. The method was applied to the optimization of a wing-body fairing for a generic business jet configuration at realistic transonic cruise flight conditions. The results demonstrate that the proposed approach achieves significant drag reduction in on- and offdesign conditions and can be used in an engineering environment.

关键词： Aerodynamic Shape optimization Generic Business Jet Configuration Genetic algorithm Two Dimensional Airfoil Numerical Simulation Aircraft Configurations Aerodynamic Performance Navier Stokes Equations Euler Equations optimization algorithm

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Resulted word counts optimization - A new approach for better automatic image annotation

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PATTERN RECOGNITION 2008年第12期41卷 3562-3571页

作者： Kwasnicka, Halina Paradowski, Mariusz Wroclaw Univ Technol Inst Appl Informat PL-50370 Wroclaw Poland

One of major problems in image auto-annotation is the difference between the expected word counts vector and the resulted word counts vector. This paper presents a new approach to automatic image annotation-an algorithm called resulted word counts optimizer which is an extension to existing methods. An ideal annotator is defined in terms of recall quality measure. On the basis of the ideal annotator an optimization criterion is defined. it allows to reduce the difference between resulted and expected word counts vectors. The proposed algorithm can be used with various image auto-annotation algorithms because its generic nature. Additionally, it does not increase the computational complexity of the original annotation method processing phase. It changes output word probabilities according to a pre-calculated vector of correction coefficients. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： automatic image annotation ideal image annotator recall quality measure optimization algorithm

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Amplitude-only Shaping optimization Method for Circular Planar Slot Array Antennas

Amplitude-only Shaping Optimization Method for Circular Plan...

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11th IEEE Singapore International Conference on Communication Systems

作者： Zha, Xiaochen Wang, Jian Ren, Lixia Univ Elect Sci & Technol China Sch Elect Engn Chengdu 610054 Peoples R China

ISBN: (纸本)9781424424238

A new method for amplitude -only optimization of circular planar slot array antennas is presented. In order to form a given three-dimensional antenna pattern for array antennas, variable metric algorithms, Davidon- Fletcher- Powell(DFP) and Broyden- Fletcher- Goldfarb-Shanno (BFGS) were jointly used to optimize the amplitude distribution of the current excitations. Thus, the optimized main lobe of the antenna pattern is fitted for the given and the side lobe level is efficiently controlled. This method solves N-dimensional unrestricted function;it shows fast convergence and small amount of computing. It is a valuable beam shaping method for array antennas.

关键词： shaped three-dimensional pattern circular slot array antennas amplitude-only method optimization algorithm

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Unsteady discrete adjoint formulation for two-dimensional flow problems with deforming meshes

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AIAA JOURNAL 2008年第6期46卷 1351-1364页

作者： Mani, Karthik Mavriplis, Dimitri J. Univ Wyoming Dept Mech Engn Laramie WY 82071 USA

A method to apply the discrete adjoint for computing sensitivity derivatives in two-dimensional unsteady flow problems is presented. The approach is to first develop a forward or tangent linearization of the nonlinear flow problem in which each individual component building up the complete flow solution is differentiated against the design variables using the chain rule. The reverse or adjoint linearization is then constructed by transposing and reversing the order of multiplication of the forward problem. The developed algorithm is very general in that it applies directly to the arbitrary Lagrangian-Eulerian form of the governing equations and includes the effect of deforming meshes in unsteady flows. It is shown that an unsteady adjoint formulation is essentially a single backward integration in time and that the cost of constructing the final sensitivity vector is close to that of solving the unsteady flow problem integrated forward in time. It is also shown that the unsteady adjoint formulation can be applied to time-integration schemes of different orders of accuracy with minimal changes to the base formulation. The developed technique is then applied to three optimization examples, the first in which the shape of a pitching airfoil is morphed to match a target time-dependent load profile, the second in which the shape is optimized to match a target time-dependent pressure profile, and the last in which the time-dependent drag profile is minimized without any loss in lift.

关键词： Two Dimensional Flow Arbitrary Lagrangian Eulerian Symmetric Airfoil Edge Computing Freestream Mach Number Angle of Attack Euler Equations Roe Approximate Riemann Solver optimization algorithm Computational Fluid Dynamics

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Coordinated standoff tracking of moving targets using Lyapunov guidance vector fields

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2008年第2期31卷 290-306页

作者： Frew, Eric W. Lawrence, Dale A. Morris, Steve Univ Colorado Boulder CO 80302 USA MLB Co Mountain View CA 94043 USA

This paper presents a control structure for cooperative stand-off line-of-sight tracking of a moving target by a team of unmanned aircraft based on a Lyapunov guidance vector field that produces stable convergence to a circling limit cycle behavior. A guidance vector field is designed for a stationary target and then modified with a correction term that accounts for a moving target and constant background wind. Cooperative tracking by multiple unmanned aircraft is achieved through additional phasing, also with a Lyapunov stability analysis. Convoy protection, in which the unmanned aircraft must scout an area ahead of the moving target, is performed by extending the cooperative stand-off line-of-sight limit cycle attractor along the direction of travel. Simulation results demonstrate the behavior of the algorithms as well as the improvement that results from cooperation. Finally, simulations of a larger cooperative search, acquisition, and tracking scenario are described that illustrate the use of the cooperative standoff line-of-sight and convoy protection controllers in a realistic application.

关键词： Lyapunov Stability Theory Standoff Tracking Flight Control System Aircraft Speed Track algorithm optimization algorithm Heading Angle Guidance Laws GPS Control algorithm

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