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Unified Method for Field-of-View-Limited Homing Guidance

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2022年第8期45卷 1415-1434页

作者： Dong, Wei Wang, Chunyan Wang, Jianan Son, Hungsun Xin, Ming Beijing Inst Technol Sch Aerosp Engn Beijing 100081 Peoples R China Ulsan Natl Inst Sci & Technol Dept Mech Engn Ulsan 44919 South Korea Univ Missouri Dept Mech & Aerosp Engn Columbia MO 65211 USA

Homing guidance requires maintaining the target lock-on condition within the seeker's field of view (FOV). This paper aims at developing a unified FOV-limited guidance framework from which a variety of two-dimensional (2D) and three-dimensional (3D) guidance laws can be derived. First, the unified method for 2D homing guidance is established by augmenting an arbitrary baseline guidance law with a biased command. To mitigate the effect on the baseline guidance law, this biased command is designed in the admissible range that respects the FOV limit and only takes effect when the lead angle approaches the FOV bound. For more practical relevance, the autopilot dynamic of any order is further considered explicitly in the design with a recursive approach. Then, the unified method for 3D homing guidance with coupling nonlinearity is developed by exploiting the geometric relation among space angles. Unlike existing similar results, the proposed design requires neither switch logic nor numerical algorithms, which allows for continuous guidance command and convenient implementation. With the proposed method, various illustrative guidance laws are derived to demonstrate the significance of the unified framework. Finally, numerical simulations with comparative study are conducted to support the analytical findings and show the superiority of the proposed method.

关键词： Homing Guidance Control Guidance Autopilot numerical Simulation numerical algorithms Rudder Flight Path Angle Optimal Control State Dependent Riccati Equation Terminal Sliding Mode

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Convex Approach to Covariance Control with Application to Stochastic Low-Thrust Trajectory Optimization

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2022年第11期45卷 2061-2075页

作者： Benedikter, Boris Zavoli, Alessandro Wang, Zhenbo Pizzurro, Simone Cavallini, Enrico Sapienza Univ Rome Dept Mech & Aerosp Engn Via Eudossiana 18 I-00184 Rome Italy Univ Tennessee Dept Mech Aerosp & Biomed Engn Knoxville TN 37996 USA Italian Space Agcy Space Transportat Space Infrastruct & Inorbit Serv Via Politecn snc I-00133 Rome Italy Italian Space Agcy Space Transportat Space Infrastruct & Inorbit Serv Space Transportat Programs Off Via Politecn snc I-00133 Rome Italy

This paper outlines a novel approach to the design of optimal space trajectories under significant uncertainty. Finite-horizon covariance control, i.e., the steering of a system from an initial probability distribution to a desired one at a prescribed time, is employed to plan an optimal nominal path along with a robust feedback controller that compensates for exogenous in-flight disturbances. A mindful convexification strategy is devised to recast the nonlinear covariance control problem as a deterministic convex optimization problem. The convexification is based on a convenient change of variables that allows for relaxing the covariance matrix discrete-time propagation into a set of semidefinite cone constraints. While featuring a larger feasible space, the relaxed problem shares the same optimal solution as the original one. The lossless property of the relaxation is analytically proven by leveraging optimal control theory and discussed on the basis of numerical experiments. Monte Carlo campaigns are carried out to validate the in-flight performance of the attained control policies.

关键词： Trajectory Optimization Thrust Probability Distribution numerical Optimization Flight Performance Linear Quadratic Regulator numerical algorithms Rockets Stochastic Optimization Powered Descent Guidance

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The time-freezing reformulation for numerical optimal control of complementarity Lagrangian systems with state jumps

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AUTOMATICA 2023年 158卷

作者： Nurkanovic, Armin Albrecht, Sebastian Brogliato, Bernard Diehl, Moritz Univ Freiburg Dept Microsyst Engn IMTEK Freiburg Germany Univ Freiburg Dept Math Freiburg Germany Siemens Technol Munich Germany Univ Grenoble Alpes INRIA CNRS Grenoble INPLJK Grenoble France

This paper introduces a novel time-freezing reformulation and numerical methods for optimal control of complementarity Lagrangian systems (CLS) with state jumps. We cover the difficult case when the system evolves on the boundary of the dynamic's feasible set after the state jump. In nonsmooth mechanics, this corresponds to inelastic impacts. The main idea of the time-freezing reformulation is to introduce a clock state and an auxiliary dynamical system whose trajectory endpoints satisfy the state jump law. When the auxiliary system is active, the clock state is not evolving, hence by taking only the parts of the trajectory when the clock state was active, we can recover the original solution. The resulting time-freezing system is a Filippov system that has jump discontinuities only in the first time derivative instead of the trajectory itself. This enables one to use the recently proposed Finite Elements with Switch Detection (Nurkanovic et al., 2022), which makes high accuracy numerical optimal control of CLS with impacts and friction possible. We detail how to recover the solution of the original system and show how to select appropriate auxiliary dynamics. The theoretical findings are illustrated on a nontrivial numerical optimal control example of a hopping one-legged robot. (c) 2023 Elsevier Ltd. All rights reserved.

关键词： Nonsmooth and discontinuous problems Modeling for control optimization numerical algorithms algorithms and software

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Enhanced High-Order Scheme for High-Resolution Rotorcraft Flowfield Analysis

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AIAA JOURNAL 2022年第1期60卷 144-159页

作者： Hong, Yoonpyo Lee, Dawoon Yee, Kwanjung Park, Soo Hyung Seoul Natl Univ Dept Aerosp Engn Seoul 08826 South Korea Seoul Natl Univ Inst Adv Aerosp Technol Seoul 08826 South Korea Konkuk Univ Dept Mech & Aerosp Engn Seoul 05029 South Korea

The recent growing interest in urban air mobility (UAM) worldwide has led to the demand for physical analyses of the aerodynamic performance and aeroacoustic characteristics of electric vertical takeoff and landing (eVTOL) rotorcraft. In a UAM eVTOL rotorcraft, the smaller vortices generated from multiple propulsors interact with lifting surfaces such as wings, fuselage, and propellers in a complex manner. Therefore, to accurately predict the performance and noise of UAM eVTOL rotorcraft, vortices should be preserved with little dissipation;and their interactions must be modeled precisely. These requirements need a numerical algorithm with a refined resolution than that allowed by conventional schemes. This paper proposes a newly modified enhanced multidimensional limiting process (eMLP) for vorticity conservation (eMLP-VC), which improves the original eMLP by accounting for the fact that most rotorcraft flowfields are vortex dominated and subsonic. For advanced capability in preserving vortices, the distinguishing criterion was modified through vortex profile analysis, and low-Mach-number adjustment was performed by reconstructing the interpolated primitive variables. The proposed scheme was applied to wave propagation, shock discontinuity, double Mach reflection, propeller-wing interaction, and Second Higher-Harmonic Control Aeroacoustic Rotor Test problems. The computed results confirmed that eMLP-VC exhibits superior resolution, numerical stability, and computational time efficiency as compared to the multidimensional limiting process, eMLP, and weighted essentially nonoscillatory methods.

关键词： Multirotor Wingtip Vortices Reynolds Averaged Navier Stokes Freestream Mach Number Propeller Blades Urban Air Mobility Primitive Variable Aircraft Configurations Vertical Takeoff and Landing numerical algorithms

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Modeling of Pulsed - Electrochemical Machining Using CFD Under Large Grid Deformations

Modeling of Pulsed - Electrochemical Machining Using CFD Und...

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AIAA Aviation Forum

作者： Mendez, Julio C. Palani, Siva Rose, Alan Corrdesa LLC Tyrone GA 30290 USA

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

Computational Fluid Dynamics (CFD) has been widely applied in multiple applications, from combustion to biofluid applications. An area that has made substantial progress is the applications of moving reference frames, where overset and morphing techniques are the two most prominent alternatives. The former allows multiple overlapping regions to move relative to each other, while the latter, morphing techniques, apply displacement to the boundaries. Due to intrinsic differences in their numerical applications, overset is more commonly applied to applications where large motions are involved. On the other hand, morphing is largely applied in studies where changes in the shape of the boundaries are expected. Because of this, Morphing is the most suitable option to model Pulsed - Electrochemical Machining (PECM). This technique uses electrochemical processes to machine hard, tough, and even ductile metals, which are difficult to machine using conventional techniques. However, designing PECM tools is an iterative process due to the complex flow field found in the electrolyte flow region. Flow phenomena such as turbulence, hydrogen evolution, and large gradients in the temperature field make the flow highly inhomogeneous. As a result, PECM tools (cathode) go through several design stages to lead to the desired shape on the workpiece (anode). With the advent of High-Performance Computing (HPC), efficient numerical algorithms, and Multiphysics CFD packages, PECM simulations have gained popularity in the CFD community. Nevertheless, one of the main challenges remains unresolved "the large grid deformation required to represent the tool motion." This work presents a novel technique where the PECM is modeled using an efficient re-meshing workflow that allows large deformation without incurring low-quality mesh metrics and/or numerical instabilities. In this work, we use Simcenter STAR-CCM+ CFD solver connected to Fidelity Pointwise, where the entire process has been scripted.

关键词： Electrochemical Machining High Performance Computing Fluid Dynamics numerical algorithms Temperature Fields High Aspect Ratio Computational Simulation Electrical Conductivity Distributions Comsol Multiphysics Conservation Equations

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Approximate Formulations in Mean Models of Dielectric Barrier Discharge Plasma Flow Actuator

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AIAA JOURNAL 2022年第7期60卷 4215-4226页

作者： Adamiak, Kazimierz Western Univ Dept Elect & Comp Engn London ON N6A 3K7 Canada

A new simplified algorithm is proposed for numerical simulation of dielectric barrier discharge actuators. It is based on a three-species fluid model and includes five ionic reactions. The reaction rate coefficients are calculated from the Boltzmann equation, and the local field approximation is used. To drastically reduce the computing time, the discharge pulses are artificially damped. Two approximate models for photoionization are implemented and compared. This numerical algorithm is an attempt to compromise two approaches previously proposed: full plasma models, requiring prohibitively long computing time, and phenomenological models, which were based on inadequate physics. The electrical and mechanical characteristics of the electrohydrodynamics flow generated by the discharge are presented and validated by comparing with the experimental data, proving satisfactory accuracy of the model.

关键词： Plasma Actuator Dielectric Barrier Discharge EHD numerical Simulation Reduced Computing Time Boltzmann Constant numerical algorithms numerical Modeling Electric Field Intensity Electric Power

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A STOCHASTIC FRAMEWORK FOR ATOMISTIC FRACTURE\ast

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SIAM JOURNAL ON APPLIED MATHEMATICS 2022年第2期82卷 526-548页

作者： Buze, Maciej Woolley, Thoms E. Mihai, Angela Cardiff Univ Sch Math Cardiff CF24 4AG Wales

We present a stochastic modeling framework for atomistic propagation of a Mode I surface crack, with atoms interacting according to the Lennard--Jones interatomic potential at zero temperature. Specifically, we invoke the Cauchy--Born rule and the maximum entropy principle to infer probability distributions for the parameters of the interatomic potential. We then study how uncertainties in the parameters propagate to the quantities of interest relevant to crack propagation, namely, the critical stress intensity factor and the lattice trapping range. For our numerical investigation, we rely on an automated version of the so-called numerical-continuation enhanced flexible boundary NCFlex algorithm.

关键词： Key words elasticity interatomic potential stress fracture stochastic modelling numerical algorithms

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Continuous Optimization for Control of Hybrid Systems With Hysteresis via Time-Freezing

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IEEE CONTROL SYSTEMS LETTERS 2022年 6卷 3182-3187页

作者： Nurkanovie, Armin Diehl, Moritz Univ Freiburg Dept Microsyst Engn D-79110 Freiburg Germany Univ Freiburg Dept Math D-79110 Freiburg Germany

This letter regards numerical optimal control of a class of hybrid systems with hysteresis using solely techniques from nonlinear optimization, without any integer variables. Hysteresis is a rate independent memory effect which often results in severe nonsmoothness in the dynamics. These systems are not simply Piecewise Smooth Systems (PSS);they are a more complicated form of hybrid systems. We introduce a time-freezing reformulation which transforms these systems into a PSS. From the theoretical side, this reformulation opens the door to study systems with hysteresis via the rich tools developed for Filippov systems. From the practical side, it enables the use of the recently developed Finite Elements with Switch Detection (Nurkanovic et al., 2022), which makes high accuracy numerical optimal control of hybrid systems with hysteresis possible. We provide a time optimal control problem example and compare our approach to mixed-integer formulations from the literature.

关键词： Hysteresis Optimal control Transforms Switches Clocks Automata Optimization Hybrid systems optimal control numerical algorithms software

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Short-Term Collision Probability Algorithm for Parallelepiped-Shaped Satellites

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2022年第6期45卷 1093-1107页

作者： Enriquez, Cesar Daniel Garcia-Pelayo, Ricardo Tech Univ Madrid Madrid 28040 Spain Ronda Poniente 19 Tres Cantos 28760 Spain Tech Univ Madrid Escuela Tecn Super Ingn Aeronaut & Espacio Dept Appl Phys Plaza Cardenal Cisneros 3 Madrid 28040 Spain

The probability of collision of two solid satellites, one of which is a parallelepiped and the other is a parallelepiped or a small sphere, is computed under the assumptions of short-term encounter. The probability is given by the integral of the relative position probability density over a region of the collision plane. This region is the Minkowski sum of the projections of the objects' shapes onto the collision plane. The integration is the only step that cannot be done analytically. When the position probability densities are Gaussians, a very fast and accurate algorithm found in the literature can be applied after several transformations have been performed to the integration region. A comparison against several current methods has been included. When a parallelepiped is involved, the presented method is advantageous with respect to the existing ones.

关键词： Satellites Computing Probability Density Functions Space Situational Awareness numerical Integration numerical algorithms Monte Carlo Simulation High Aspect Ratio Radar Imaging Space Agencies

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Stochastic Optimal Control of a Sailboat

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IEEE CONTROL SYSTEMS LETTERS 2022年 6卷 2048-2053页

作者： Miles, Cole Vladimirsky, Alexander Cornell Univ Phys Dept Ithaca NY 14850 USA Cornell Univ Math Dept Ithaca NY 14850 USA

In match race sailing, competitors must steer their boats upwind in the presence of unpredictably evolving weather. Combined with the tacking motion necessary to make upwind progress, this makes it natural to model their path-planning as hybrid stochastic optimal control problems. Dynamic programming provides the tools for solving these, but the computational cost can be significant. We greatly accelerate a semi-Lagrangian iterative approach of Ferretti and Festa by reducing the state space dimension and designing an adaptive timestep discretization that is very nearly causal. We also provide a more accurate tack-switching operator by integrating over potential wind states after the switch. The method is illustrated through a series of simulations with varying stochastic wind conditions.

关键词： Switches Mathematical models Boats Wind Optimal control numerical models Interpolation Stochastic optimal control switched systems numerical algorithms

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