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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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Anisotropic and asymmetrical yielding and its distorted evolution: Modeling and applications

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INTERNATIONAL JOURNAL OF PLASTICITY 2016年 82卷 127-158页

作者： Li, H. Hu, X. Yang, H. Li, L. Northwestern Polytech Univ State Key Lab Solidificat Proc Sch Mat Sci & Engn Xian 710072 Peoples R China Res Inst Baosteel Automobile Steel Res Inst Shanghai 201900 Peoples R China

Characterizing the anisotropy/asymmetry-induced distortional yielding and subsequent evolution is still a challenge for potential usages of hard-to-deform materials. From perspective of multiple mechanisms, two types of yield functions are classified, viz., the principal shear stress-based models (SSM) and the stress invariants-based models (SIM);then a unified continuum-based discontinuous (CBD) framework is constructed, in which SSM and SIM are introduced to capture the distorted shape of the yielding, and an interpolation approach is adopted to smoothly present the nonlinear evolution of the distorted plasticity in the full stress space. Taking the CPB06 (Cazacu et al., 2006) and Yoon's criteria (Yoon et al., 2014) as typical SSM and SIM, the CBD framework is implemented in the explicit 3D-FE platform for practical usages by combining implicit algorithm and interpolation approach, and the Nelder-Mead (N-M) method and the genetic algorithm (GA) approach are evaluated for calibrating of CBD related to convergence, overlapping and accuracy. The evaluation proves that the GA-based method is suitable for CBD, and the SIM seems to be feasible for embedding into the CBD framework because of its solid physical basis and numerical robustness. Taking high strength titanium alloy tube (HSTC) as a case, the distorted plasticity evolution of the HSTT with six typical initial textures are characterized, then the correlations among initial textures, distorted behaviors and inhomogeneous deformation are quantitatively established to improve the multi-defect constrained formability in uniaxial tension/compression and mandrel bending. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Yield condition Anisotropic material Constitutive behaviour Finite elements numerical algorithms

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Ontology-Enabled Generation of Simulation Software for a Complex Dynamic System

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2018年第7期15卷 462-470页

作者： Sankari, S. S. Uma Kumar, P. Sreenivasa Geethaikrishnan, C. Indian Inst Technol Madras Dept Comp Sci & Engn Artificial Intelligence & Database Res Lab Chennai 600036 Tamil Nadu India Indian Space Res Org Vikram Sarabhai Space Ctr Qual Assurance Mission Div Thiruvananthapuram 695022 Kerala India

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Experimental and Visco-Plastic Self-Consistent evaluation of forming limit diagrams for anisotropic sheet metals: An efficient and robust implementation of the M-K model

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INTERNATIONAL JOURNAL OF PLASTICITY 2015年 73卷 62-99页

作者： Schwindt, C. Schlosser, F. Bertinetti, M. A. Stout, M. Signorelli, J. W. UNS CONICET Dept Engn Buenos Aires DF Argentina IFIR UNR CONICET Rosario Santa Fe Argentina

In the present work, an efficient formulation for the prediction of forming-limit diagrams (FLDs) based on the well-known Marciniak and Kuczynski (M-K) theory using a Visco-Plastic Self-Consistent (VPSC) crystal-plasticity model has been detailed. The present model extends the previous MK-VPSC implementation (Signorelli et al., Predictions of forming limit diagrams using a rate-dependent polycrystal self-consistent plasticity model, International Journal of Plasticity 25 (2009) 1-25) based on the Newton Raphson (N-R) method, which gives no guarantee of a robust iterative procedure. In order to avoid convergence problems and to reduce the computational cost of the coupled MK-VPSC scheme, a direct approach (DA) is proposed. The DA eliminates the need of the Jacobian evaluation associated with the N-R method as well as the iterative procedure tied to other possible minimization techniques. Moreover, the mechanical states outside and inside the groove are solved in the sample reference frame, avoiding the need to rotate the crystallographic orientations and the internal variables to the current band reference frame at each increment. In this way, only two calls to the material law are required per M-K increment, obtaining a more robust numerical procedure with a significant computational cost reduction. Interestingly, the requirement of more complex boundary conditions does not substantially increase the number of internal VPSC iterations to achieve a given tolerance. Simulation results show that the direct MK-VPSC approach is consistent with that based on the N-R method. The generalized boundary conditions in the polycrystal model allowed us to calculate either strain-rate ratio or stress ratio based FLDs. The effect of using either strain-rate ratio or stress ratio paths on the FLDs has been investigated by imposing three types of pre-straining on the sheet metals. Formability predictions for a randomly-textured FCC material and for textured FCC, BCC and HCP polycryst

关键词： Ductility Polycrystalline material Viscoplastic material numerical algorithms Forming limit

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Vibration mode localization in two-dimensional systems

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AIAA JOURNAL 1997年第10期35卷 1653-1659页

作者： Xie, WC Wang, X University of Waterloo Waterloo Ontario N2L 3G1 Canada

The method of regular perturbation is applied to study vibration mode localization in randomly disordered weakly coupled two-dimensional cantilever-spring arrays. Localization factors, which characterize the average exponential rates of decay or growth of the amplitudes of vibration, are defined in terms of the angles of orientation. First-order approximate results of the localization factor are obtained using a combined analytical-numerical approach. The localization factors are symmetric about the cantilever and the horizontal and vertical axes passing through the cantilever at which vibration is originated. For the systems under consideration, the direction in which vibration is originated corresponds to the smallest localization factor;whereas the diagonal directions correspond to the largest rate of decay or growth of the amplitudes of vibration. When plotted in the logarithmic scale, the vibration modes are of a hill shape with the amplitudes of vibration decaying linearly away from the cantilever at which vibration is originated.

关键词： Cantilever Bending Stiffness Structural Dynamics Linear Vibrations Green's Function numerical algorithms Computer Memory Kinetic Energy

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DESIGNING REDUCED-ORDER LINEAR-MULTIVARIABLE CONTROLLERS USING EXPERIMENTALLY DERIVED PLANT-DATA

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1993年第1期16卷 53-58页

作者： FRAZIER, WG IRWIN, RD Ohio University Athens Ohio 45701

An iterative numerical algorithm for simultaneously improving multiple performance and stability robustness criteria for multivariable feedback systems is developed. The unsatisfied design criteria are improved by updating the free parameters of an initial, stabilizing controller's state-space matrices. Analytical expressions for the gradients of the design criteria are employed to determine a parameter correction that improves all of the feasible, unsatisfied design criteria al each iteration. A controller design is performed using the algorithm with experimentally derived data from a large space structure test facility. Experimental results of the controller's performance at the facility are presented.

关键词： Large Space Structures numerical algorithms Open Loop Controller Linear Quadratic Gaussian Mathematical Models Control System Design Algorithm Performance Frequency Domain NASA Marshall Space Flight Center Search Algorithm

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OPTIMAL REENTRY MANEUVERS WITH BOUNDED LIFT CONTROL

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1987年第4期10卷 321-329页

作者： BEINER, L Tel Aviv University Ramat Aviv Israel

Green’s theorem is employed to find the optimal lift control that transfers a hypervelocity vehicle between prescribed initial and final values of the altitude and flight-path angle when maximum lift coefficient is bounded. Payoffs to be extremized are either final velocity, range, time, or heat input. Problem formulation leads to linear control, and the optimal maneuvers consist of either max-lift/min-lift or itnin-lift/max-lift nonsingular paths. Conditions for the final state to be reachable by such sequences are derived. Only descending or ascending trajectories are considered. Analytical solutions are derived, and order of subarcs and locations of switching points are determined. Results of parametric studies in nondimensional form are presented graphically. © 1987 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Flight Path Angle Lift Coefficient Zero Lift Drag Coefficient Lift to Drag Ratio Optimal Control numerical algorithms Heat Transfer Earth

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A quasistatic implementation of the concurrent atomistic-continuum method for FCC crystals

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INTERNATIONAL JOURNAL OF PLASTICITY 2015年 72卷 91-126页

作者： Xu, Shuozhi Che, Rui Xiong, Liming Chen, Youping McDowell, David L. Georgia Inst Technol GWW Sch Mech Engn Atlanta GA 30332 USA Univ Florida Dept Mech & Aerosp Engn Gainesville FL 32611 USA Iowa State Univ Dept Aerosp Engn Ames IA 50011 USA Georgia Inst Technol Sch Mat Sci & Engn Atlanta GA 30332 USA

In recent years, numerous partitioned-domain methods have been developed to describe dislocation behavior at length scales that are usually inaccessible to most classical atomistic methods. These methods retain full atomistic detail in regions of interest while using a continuum description to reduce the computational burden elsewhere. In most of these methods, however, lattice defects in the continuum are either implemented via constitutive relations, lattice elasticity with dislocation field interactions, or are not permitted at all. In such approaches, the transit of dislocations across the atomistic/continuum interface appeals to approximate heuristics intended to minimize the effects of the interface due to the change from atomistic to continuum degrees of freedom. The concurrent atomistic-continuum (CAC) method, originally developed for addressing dynamic dislocation behavior by Xiong et al. (2011), permits dislocations to propagate in a continuum domain that employs a piecewise continuous finite element description with interelement displacement discontinuities. The method avoids ghost forces at interfate between atomistically resolved and coarse-grained domains. CAC has subsequently been used to investigate complex dislocation behavior in face-centered cubic (FCC) metals (Xiong et al., 2012b,a,c, 2015). In this paper, we propose a quasistatic 3-D method to carry out sequential energy-minimized simulations at 0 K. This facilitates study of structure evolution along minimum energy pathways, avoiding over-driven conditions of high rate molecular dynamics. Parallelization steps in code implementation are described. Applications are presented for the quasistatic CAC method in FCC metal plasticity. Comparisons are made with a fully-resolved atomistic method for generalized stacking fault energy, core structure and stress field of a single 60 mixed type dislocation, surface indentation, and 60 mixed type dislocation migration through the interface between atomistic

关键词： Concurrent atomistic-continuum method Dislocations Metallic material Finite elements numerical algorithms

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On the algorithmic implementation of a material model accounting for the effects of martensitic transformation

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STEEL RESEARCH INTERNATIONAL 2006年第9-10期77卷 733-740页

作者： Antretter, Thomas Fischer, Franz Dieter Cailletaud, Georges Ortner, Balder Univ Leoben Inst Mech A-8700 Leoben Austria Ecole Mines Ctr Mat Evry France Univ Leoben Inst Met Phys A-8700 Leoben Austria

The formulation and numerical implementation of a material model with as little phenomenological input as possible requires a thorough investigation of the physical relationships relevant for the material under consideration. In the present case the focus is on the correct description of the TRIP (Transformation Induced Plasticity) effect and its interpretation in terms of a transformation surface concept similar to the well-known yield surface approach used in classical plasticity. Some general aspects of the thermodynamics of martensitic transformation along with a general idea of the topology of a transformation surface in stress space are presented and cast into equations suitable for the implementation into a finite element program. A normality rule for the transformation strain rate can be derived in analogy to the well established procedures of flow plasticity. The notion of a transformation hardening is introduced, collectively characterizing the mechanisms inhibiting transformation. They can be quantified based on the data from dilatometer tests. In contrast to earlier models of this group of authors [1], the algorithm at hand allows to keep track of the evolution of each single variant thus providing detailed insights into the variant selection mechanisms for various load levels and loading directions.

关键词： martensitic transformation transformation induced plasticity numerical algorithms orientation effect

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Arnold tongue predictions of secondary buckling in thin elastic plates

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 1999年第10期47卷 2187-2206页

作者： Everall, PR Hunt, GW Univ Bath Dept Mech Engn Bath BA2 7AY Avon England

The stability of post-buckled states for simply-supported flat elastic plates under compression is investigated for a range of in-plane boundary conditions. The von Karman plate equations are reduced to a series of ODEs which are solved numerically under parametric variation of both load and length. Results are checked against full numerical solutions of the PDEs, and comparison with a modal analysis highlights the dominant passive contaminations. The nondimensional amplitude at secondary bifurcation, for any combination of modes and all plate lengths, is presented in a concise form using the parameter space of Arnold tongues. This demonstrates that compound bifurcation represents a worst case for post-buckling reserve, and that long plates have inherently more such reserve than short plates. It is also shown that stiffening the boundaries against inplane movement is destabilizing, in that it induces mode jumping at secondary bifurcation to occur at an earlier stage in the post-buckling regime. (C) 1999 Elsevier Science Ltd. All rights reserved.

关键词： structures energy methods numerical algorithms mode jumping

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