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Optimal packing in additive manufacturing

IFAC-PapersOnLine 2019年第13期52卷 2758-2763页

作者： Romanova, T. Stoyan, Y. Pankratov, A. Litvinchev, I. Yanchevsky, I. Mozgova, I. Institute for Mechanical Engineering Problems of the National Academy of Sciences of Ukraine Department of Mathematical Modelling and Optimal Design Kharkiv Ukraine Faculty of Mechanical and Electrical Engineering San Nicolas de los Garza Mexico National Technical University of Ukraine ''Igor Sikorsky Kyiv Polytechnic Institute Department of Dynamics and Strength of Machines and Strength of Materials Kyiv Ukraine Institute of Product Development Leibniz University of Hannover Hannover Germany

The paper studies a packing problem for ellipses placed into an arbitrary disconnected polygonal domain. Neither a number of ellipses nor their sizes are fixed. The objective is maximizing packing factor. The ellipses can be continuously translated and rotated. Restrictions on the dimensions of the ellipses are taken into account. Placement constraints (distance constraints between ellipses and containment of ellipses into a polygonal domain) are formulated using the phi-function technique. Resulting packing problem is stated in the form of MIP model that is equivalent to a sequence of NLP subproblems. A new solution approach is proposed combining a feasible starting point algorithm and an optimization procedure to search for efficient locally optimal solutions. The approach as an addition to existing topology optimization algorithms, can be used to automate design of parts for «support-free» additive manufacturing taking into account requirements of static and/or fatigue strength. © 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

关键词： Geometry 3D printers Additives Functions Mathematical models nonlinear programming Packing Distance constraints Ellipses Non linear optimization Optimal solutions Optimization algorithms Optimization procedures Phi function technique Solution approach

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Accelerated Model Predictive Control Using Restricted Quadratic programming ⁎

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IFAC-PapersOnLine 2020年第2期53卷 7001-7006页

作者： Anson Maitland John McPhee Department of Systems Design Engineering University of WaterlooWaterloo Canada

We present a method to reduce the computational burden of solving a sequence of convex quadratic programs (QPs). By determining offline what search space is most important, we can restrict our online problem to that subspace, reducing the dimension and computational cost of the QP solver. The process we present is very simple requiring surprisingly little data. Further, we present a modified sequential QP algorithm that leverages the restricted QP approach to solve nonlinear programming problems found in model predictive control. Lastly, we apply these to a benchmark MPC problem and demonstrate their effectiveness using a variety of established QP solvers. We demonstrate that QP problems can be solved faster with minimal MPC performance degradation and highlight future directions for this work.

关键词： Model-based control Predictive control Quadratic programming nonlinear programming

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RGB-D Indoor Simultaneous Location and Mapping Based on Inliers Tracking Statistics

RGB-D Indoor Simultaneous Location and Mapping Based on Inli...

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International Seminar on Computer Science and Engineering Technology (SCSET)

作者： Niu, Xiaoning Liu, Hongzhe Yuan, Jiazheng Beijing Union Univ Beijing Key Lab Informat Serv Engn Beijing 100101 Peoples R China Beijing Open Univ Beijing 100081 Peoples R China

In this paper, an algorithm based on Inliers tracking statistics is proposed to solve the problem of motion-blur interference of RGB-D SLAM front-end pose estimation and back-end optimization. Firstly, the feature extraction and matching of the RGB image are carried out and the inliers is obtained by the RANSAC algorithm. Then, the blur image affected by the camera motion is removed by the tracking and statistics of the inliers quantity, and the camera position is solved by the nonlinear optimization method. Finally, the motion trajectory and the three-dimensional dense point cloud are plotted by and optimized global pose. Experimental results based on standard test set show that the algorithm based on Inliers tracking can improve the robustness and precision of SLAM system.

关键词： nonlinear programming

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Research on tension optimization of under-constrained collaborative towing system with multi-helicopters in inverse dynamics

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UPB Scientific Bulletin, Series D: Mechanical Engineering 2020年第1期82卷 79-92页

作者： Su, Cheng Zhang, Shaohui Li, Wei Ding, Wangcai Zhao, Zhigang School of Mechatronic Engineering Lanzhou Jiaotong University Lanzhou China

In the under-constrained system that multiple unmanned helicopters cooperatively tow a load by cables, the tension of the cables cannot be obtained directly since the number of the equations is always smaller than the number of unknown quantities in inverse dynamics problem. In this paper, on the basis of established dynamic equation of the system, the problem of calculating the tension of cables in real time is converted into a nonlinear programming problem. Therefore, minimum solution and maximum solution of cable tensions that meet the requirements can be obtained. The optimal solution is between minimum solution and maximum solution, which can be expressed by linear interpolation. In the process of optimization, the optimal objective function is expressed by the p-norm approximately considering that the optimal solution may not be continuous in some cases. Finally, the feasibility of cable tension optimization method is illustrated simulatively by three unmanned helicopters cooperatively tow a load by cables. © 2020, Politechnica University of Bucharest. All rights reserved.

关键词： nonlinear programming

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Introducing a Linear Gamma Variate Fit to Measure Pulmonary Perfusion with Electrical Impedance Tomography

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Current Directions in Biomedical Engineering 2020年第3期6卷

作者： Schuderer, Felix Kircher, Michael Dössel, Olaf Stender, Birgit Bluth, Thomas Gama De Abreu, Marcelo Institute of Biomedical Engineering Kit Fritz-Haber-Weg 1 Karlsruhe Germany Institute of Biomedical Engineering Kit Karlsruhe Germany Drägerwerk Ag and Co. KGaA Lübeck Germany Pulmonary Engineering Group Department of Anesthesiology and Intensive Care Medicine University Hospital and Tu Dresden Dresden Germany

The indicator dilution method (IDM) is one approach to measure pulmonary perfusion using Electrical Impedance Tomography (EIT). To be able to calculate perfusion parameters and to increase robustnes, it is necessary to approximate and then to separate the components of the measured signals. The component referring to the passage of the injected bolus through the pixels can be modeled as a gamma variate function, its parameters are often determined using nonlinear optimization algorithms. In this paper, we introduce a linear approach that enables higher robustnes and faster computation, and compare the linear and nonlinear fitting approach on data of an animal study. © 2020 by Walter de Gruyter Berlin/Boston 2020.

关键词： nonlinear programming

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Cost minimization in placing service chains for virtualized network functions

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INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS 2020年第4期33卷

作者： Wang, Chien Ting Lin, Ying-Dar Wang, Chih-Chiang Lai, Yuan-Cheng Natl Chiao Tung Univ Grad Degree Program Network & Informat Syst Hsinchu Taiwan Acad Sinica Hsinchu Taiwan Natl Chiao Tung Univ Dept Comp Sci Hsinchu Taiwan Natl Kaohsiung Univ Appl Sci Dept Comp Sci & Informat Engn Kaohsiung Taiwan Natl Taiwan Univ Sci & Technol Dept Informat Management Taipei Taiwan

Network function virtualization (NFV) places network functions onto the virtual machines (VMs) of physical machines (PMs) located in data centers. In practice, a data flow may pass through multiple network functions, which collectively form a service chain across multiple VMs residing on the same or different PMs. Given a set of service chains, network operators have two options for placing them: (a) minimizing the number of VMs and PMs so as to reduce the server rental cost or (b) placing VMs running network functions belonging to the same service chain on the same or nearby PMs so as to reduce the network delay. In determining the optimal service chain placement, operators face the problem of minimizing the server cost while still satisfying the end-to-end delay constraint. The present study proposes an optimization model to solve this problem using a nonlinear programming (NLP) approach. The proposed model is used to explore various operational problems in the service chain placement field. The results suggest that the optimal cost ratio for PMs with high, hybrid, and low capacity, respectively, is equal to 4:2:1. Meanwhile, the maximum operating utilization rate should be limited to 55% in order to minimize the rental cost. Regarding quality of service (QoS) relaxation, the server cost reduces by 20%, 30%, and 32% as the end-to-end delay constraint is relaxed from 40 to 60, 80, and 100 ms, respectively. For the server location, the cost decreases by 25% when the high-capacity PMs are decentralized rather than centralized. Finally, the cost reduces by 40% as the repetition rate in the service chain increases from 0 to 2. A heuristic algorithm, designated as common sub chain placement first (CPF), is proposed to solve the service chain placement problem for large-scale problems (eg, 256 PMs). It is shown that the proposed algorithm reduces the solution time by up to 86% compared with the NLP optimization model, with an accuracy reduction of just 8%.

关键词： network function placement network function virtualization nonlinear programming service chains

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Optimal Coordination of Automated Vehicles at Intersections with Turns 18

Optimal Coordination of Automated Vehicles at Intersections ...

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18th European Control Conference (ECC)

作者： Hult, Robert Zanon, Mario Gros, Ebastien Falcone, Paolo Chalmers Univ Technol Dept Elect Engn Gothenburg Sweden IMT Sch Adv Studies Lucca Italy

ISBN: (纸本)9783907144008

In this paper we address the problem of coordinating automated vehicles at intersections, with a special focus on turning maneuvers. The inclusion of rear-end collision avoidance constraints into the problem is decided during turning maneuvers by a smooth function of the vehicle state, rather than integer variables. Moreover, curvature-based acceleration constraints are introduced, which limit the velocity of the vehicle during the turn, and a term in the objective function accounts for passenger comfort. We discuss how the coordination problem is formulated as a nonlinear program and show though simulations that for practical problem instances the proposed approximation is either exact or introduces very little conservativeness.

关键词： nonlinear programming

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Optimization studies of low-density polyethylene process: effect of different interval numbers

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CHEMICAL PRODUCT AND PROCESS MODELING 2020年第4期15卷

作者： Azmi, Ashraf Sata, Suhairi Abdul Rohman, Fakhrony Sholahudin Aziz, Norashid Univ Sains Malaysia Sch Chem Engn Engn Campus Perai 14300 Pulau Pinang Malaysia

The highly exothermic nature of the low-density polyethylene (LDPE) polymerization process and the heating-cooling prerequisite in tubular reactor can lead to various problems particularly safety and economic. These issues complicate the monomer conversion maximization approaches. Consequently, the dynamic optimization study to obtain maximum conversion of the LDPE is carried out. A mathematical model has been developed and validated using industrial data. In the dynamic optimization study, maximum monomer conversion (X-M) is considered as the objective function, whereas the constraint and bound consists of maximum reaction temperature and product melt flow index (MFI). The orthogonal collocation (OC) on finite elements is used to convert the original optimization problems into nonlinear programming (NLP) problems, which are then solved using sequential quadratic program (SQP) methods. The result shows that five interval numbers produce better optimization result compared to one and two intervals.

关键词： dynamic optimization low-density polyethylene nonlinear programming tubular reactor

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Improved gradient projection method for parametric optimisation of bar structures

MAGAZINE OF CIVIL ENGINEERING

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MAGAZINE OF CIVIL ENGINEERING 2020年第6期98卷

作者： Yurchenko, V. V. Peleshko, I. D. Kyiv Natl Univ Construct & Architecture Kiev Ukraine Lviv Polytech Natl Univ Lvov Ukraine

Numerical optimization and the finite element method have been developed together to make possible the emergence of structural optimization as a potential design tool. The main research goal of this paper is the development of mathematical support and a numerical algorithm to solve parametric optimization problems of structures with orientation on software implementation in a computer-aided design system. The paper considers parametric optimization problems for bar structures formulated as nonlinear programming ones. The method of the objective function gradient projection onto the active constraints surface with simultaneous correction of the constraints violations has been used to solve the parametric optimization problem. Equivalent Householder transformations of the resolving equations of the method have been proposed. They increase numerical efficiency of the algorithm developed based on the considered method. Additionally, proposed improvement for the gradient projection method also consists of equivalent Givens transformations of the resolving equations. They ensure acceleration of the iterative searching process in the specified cases described by the paper due to decreasing the amount of calculations. The comparison of the optimization results of truss structures presented by the paper confirms the validity of the optimum solutions obtained using proposed improvement of the gradient projection method. The efficiency of the proposed improvement of the gradient projection method has been also confirmed taking into account the number of iterations and absolute value of the maximum violation in the constraints.

关键词： parametric optimization bar structures nonlinear programming gradient projection method finite element analysis

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A Four-component Polarimetric Decomposition Method Based on Generalized Scattering Models

A Four-component Polarimetric Decomposition Method Based on ...

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Photonics and Electromagnetics Research Symposium - Fall (PIERS - Fall)

作者： Wu, G. Q. Chen, S. W. Wang, X. S. Natl Univ Def Technol State Key Lab Complex Electromagnet Environm Effe Changsha 410073 Peoples R China

ISBN: (纸本)9781728153049

Polarimetric target decomposition is a powerful tool for polarimetric synthetic aperture radar (PolSAR) data interpretation and utilization. Although many advances have been reported, scattering mechanism ambiguity still occurs for manmade targets with large orientations. Recently, a general model-based decomposition has been established to mitigate this ambiguity by modeling the orientations of manmade structures. However, the optimal solutions are obtained with nonlinear optimization which usually costs a large computation time. This work aims at maintaining the generalized scattering models while significantly reducing the computation burden. The main contributions are two-fold. Firstly, the generalized scattering models are adapted to fit the actual observed situation. The second contribution is the parameter inversion. In proposed decomposition procedure, the volume scattering power is derived through an eigen decomposition problem. Then, the helix scattering power is obtained through the imaginary part of a coherency matrix element. The next two scattering components of odd-bounce and double-bounce are calculated through a set of linear equations. As a result of extra freedoms, the roll-invariant feature, Alpha angle from H/alpha/A decomposition is selected as a branch condition to discriminate between dominant odd-bounce and double bounce scattering mechanisms. The comparison experiments are carried out on airborne PolSAR data sets. The experiment results demonstrate that the proposed method achieved improved decomposition performance and greatly reduced computation time.

关键词： nonlinear programming

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