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A two-step approach to damage localization at supporting structures of offshore wind turbines

STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL 2018年第5期17卷 1313-1330页

作者： Schroeder, Karsten Gebhardt, Cristian Guillermo Rolfes, Raimund Leibniz Univ Hannover Inst Struct Anal Appelstr 9A D-30167 Hannover Germany

This article introduces a new adaptive two-step optimization algorithm for finite element model updating with special emphasis on damage localization at supporting structures of offshore wind turbines. The algorithm comprises an enhanced version of the global optimization algorithm simulated annealing, the simulated quenching method that approximates an initial guess of damage localization. Subsequently, sequential quadratic programming is used to compute the final solution adaptively. For the correlation of numerical model and measurement data, both a measure based on eigenfrequencies and mode shapes and a measure employing time series are implemented and compared with respect to their performance for damage localization. Phase balance of the time signals is achieved using cross-correlation. The localization problem is stated as a minimization problem in which the measures are used in time and modal domain as the objective function subject to constraints. Furthermore, the objective function value of the adjusted model is used to distinguish correct from wrong solutions. The functionality is proven using a numerical model of a monopile structure with simulated damage and a lab-scaled model of a tripile structure with real damage.

关键词： Model updating damage localization simulated quenching sequential quadratic programming

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Gradient-Free Trust-Region-Based Adaptive Response Surface Method for Expensive Aircraft Optimization

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AIAA JOURNAL 2018年第2期56卷 862-873页

作者： Long, Teng Li, Xin Shi, Renhe Liu, Jian Guo, Xiaosong Liu, Li Key Lab Dynam & Control Flight Vehicle Beijing 100081 Peoples R China Beijing Inst Technol Sch Aerosp Engn Beijing 100081 Peoples R China Minist Educ Sch Aerosp Engn Singapore Singapore

This paper presents a novel gradient-free trust region assisted adaptive response surface method for aircraft optimization problems with expensive functions. A gradient-free trust region sampling space approach is developed for design space reduction and sequential sampling, and response surface metamodel refitting enables the trust region assisted adaptive response surface method to possess higher optimization efficiency and better global convergence capability. Besides, an election sequential Latin hypercube sampling method is developed to improve the space-filling property and feasibility of the sequential samples. Moreover, the augmented Lagrangian method is employed to handle expensive constraints. The trust region assisted adaptive response surface method outperforms several adaptive response surface metamodel variants in the comparative study on a number of benchmark problems. Additionally, compared with several other well-known metamodel-based global optimization algorithms, the proposed algorithm also shows favorable performance in global convergence, efficiency, and robustness. Next, the trust region assisted adaptive response surface method is successfully applied to solve an airfoil aerodynamic optimization problem based on computational fluid dynamics simulation to demonstrate its effectiveness for real-world engineering problems. Finally, limitations of the proposed method and future work are discussed.

关键词： Aircrafts Augmented Lagrangian Method NACA 0012 Computational Fluid Dynamics Simulation sequential quadratic programming ICE Lift Coefficient Aircraft Design Process MATLAB Aerodynamic Characteristics

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Simulation and optimization of a continuous biodiesel plant using nonlinear programming

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ENERGY 2019年 189卷

作者： Alvardes, Adan de Oliveira Prata, Diego Martinez Santos, Lizandro de Sousa Univ Fed Fluminense Dept Engn Quim & Petr Rua Passo da Patria 156 BR-24210240 Niteroi RJ Brazil

The continuous production of biodiesel is achieved through a sequence of stages such as reaction, absorption, decantation, and product distillation. These steps require certain performance criteria that must be optimized. Several works have addressed the optimization of the design of biodiesel plants, and these have usually examined modifications to the dimensions and types of equipment or energy integration. However, there is only limited literature available on determining optimal operating conditions for existing processes. In this paper, the steady-state optimization of a soybean continuous biodiesel plant is proposed. To this end, a mathematical model to describe the chemical kinetics of soybean oil trans-esterification was developed and incorporated into a chemical process simulator. The optimization procedure is based on multidimensional sequential quadratic programming (SQP), in which the primary objectives were to minimize the plant's energy consumption subject to a minimum of 99 wt% biodiesel purity. The results reveal that the optimization of the current process allows a 4.45% reduction in energy consumption compared to the base case. Besides, the study also evidenced that the optimization approach can be applied to recalculate the optimal point when possible disturbances can deviate the system from a steady state. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： sequential quadratic programming Nonlinear programming Transesterification

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Local optimum in multi-material topology optimization and solution by reciprocal variables

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STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION 2018年第3期57卷 1283-1295页

作者： Long, Kai Wang, Xuan Gu, Xianguang North China Elect Power Univ Beijing Key Lab Energy Safety & Clean Utilizat Beijing 102206 Peoples R China North China Elect Power Univ State Key Lab Alternate Elect Power Syst Renewabl Beijing 102206 Peoples R China Dalian Univ Technol Dept Engn Mech State Key Lab Struct Anal Ind Equipment Dalian 116024 Peoples R China Hefei Univ Technol Sch Automobile & Traff Engn Hefei 230009 Anhui Peoples R China

It is revealed that the local optimum is particularly prone to occur in multi-material topology optimization using the conventional SIMP method. To overcome these undesirable phenomena, reciprocal variables are introduced into the formulation of topology optimization for minimization of total weight with the prescribed constraint of various structural responses. The SIMP scheme of multi-phase materials is adopted as the interpolation of the elemental stiffness matrix, mass matrix and weight. The sensitivities of eigenvalue and weight with respect to design variables are derived. Explicit approximations of natural eigenvalue and weight are given with the help of the first and second order Taylor series expansion. Thus, the optimization problem is solved using a sequential quadratic programming approach, by setting up a sub-problem in the form of a quadratic program. The filtering technique by solving the Helmholtz-type partial differential equation is performed to eliminate the checkerboard patterns and mesh dependence. Numerical analysis indicates that it is beneficial to avoid the local optimum by using the reciprocal SIMP formulation. Besides, the structure composed of multi-materials can achieve a lighter design than that made from the exclusive base material. The effectiveness and capability of the proposed method are also verified by nodal displacement constraint and multiple constraints.

关键词： Topology optimization Local optimum Multi-phase materials Natural frequency sequential quadratic programming

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Development of an optimum mix design method for self-compacting concrete based on experimental results

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CONSTRUCTION AND BUILDING MATERIALS 2018年 168卷 113-123页

作者： Habibi, Alireza Ghomashi, Jian Shahed Univ Civil Engn Dept Tehran Iran Univ Kurdistan Civil Engn Dept Sanandaj Iran

The main objective of this study is to develop an optimum mix design method for self-compacting concrete (SCC) based on experimental results. For this purpose, mix design of self-compacting concrete is formulated as an optimization problem. Given the importance of manufacturing costs of concrete, the total cost of one cubic meter of self-compacting concrete is considered as the objective function in the optimization problem, which must be minimized. Limitation of the 28-day compressive strength and slump flow of self-compacting concrete are considered as the main inequality constraints. To ensure that sum of concrete components makes unit volume, an equality constraint is considered. To formulate the self-compacting concrete mix design optimization problem based on experimental data, forty-two different mix designs of self-compacting concrete are presented and three cylinder specimens are made and tested for each of them. Two mathematical models are developed to estimate the strength and the slump of the concrete and used to define the main constraints in the mix design optimization model. The concrete specimens are prepared in a construction site in Sanandaj in Iran. Considering importance of sand grading on the compressive strength of self-compacting concrete, stone powder is used to improve sand fineness modulus. The sequential quadratic programming is employed to solve the optimal mix design problem of self-compacting concrete based on proposed model. In order to verify the proposed method, the mix design problem is solved for several case studies and then the final optimal mix designs are made in laboratory and mechanical properties of specimens are evaluated. The results show that the proposed method satisfies the mechanical characteristics of the self-compacting concrete, besides minimizing the cost of the concrete and automating the mix design process. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Self-compacting concrete Optimum mix design Compressive strength Slump flow sequential quadratic programming

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Low-Energy Near-Earth Asteroid Capture Using Momentum Exchange Strategies

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2018年第3期41卷 632-643页

作者： Tan, Minghu McInnes, Colin R. Ceriotti, Matteo Univ Glasgow Sch Engn James Watt South Bldg Glasgow G12 8QQ Lanark Scotland

This paper investigates the concept of capturing small near-Earth asteroids into bound periodic orbits at the Sun-Earth L1 and L2 points using momentum exchange. A small asteroid is first maneuvered to engineer a fly-by with a larger asteroid. Two strategies are then considered: when the small asteroid approaches the vicinity of the large asteroid, it will either impact the large asteroid or connect to it with a tether. In both strategies, momentum exchange can be used to effect the capture of one of the asteroids. Then, a two-impulse Lambert arc is used to design a postencounter transfer trajectory to the stable manifolds of the Sun-Earth L1 or L2 points. A selection strategy for candidate asteroids is proposed by considering both the deflection windows for capturing asteroids and the size of the asteroids. By investigating the outcome of the impact on the small asteroid, or the tension of the tether, the maximum velocity increment available using these momentum exchange strategies is investigated. Finally, a detailed design procedure is presented, which is then optimized using a global optimization strategy. The results show that, in principle, capture strategies using momentum exchange have the potential to deliver low-energy capture of asteroids although significant practical challenges remain.

关键词： Asteroid Collisions Earth CNT Characteristic Velocity Orbital Elements Astronomical Unit Material Properties Minimum Orbit Intersection Distance Albedo sequential quadratic programming

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Decoupling the constraints for process simulation in large-scale flowsheet optimization

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COMPUTERS & CHEMICAL ENGINEERING 2018年 113卷 240-252页

作者： Ishii, Yoshikazu Otto, Fred D. Fraxon Technol Ltd 2-18-6 Tanaka Yokohama Kanagawa Japan Univ Alberta Dept Chem & Mat Engn Edmonton AB T6G 2G6 Canada

A distinct advantage of sequential quadratic programming (SQP) is global convergence that ensures convergence from a remote starting point. When the constraints are highly nonlinear such as in flowsheet optimization, however, locally convergent Newton's method used in SQP as the equation-solving tool may deteriorate the behavior of convergence. Our recognition that this issue remains to be resolved motivated us to study a two-tier SQP approach where the constraints for process simulation consisting of nonlinear equations are decoupled from the KKT system in order to block the adverse influence of nonlinearity on global convergence. Our equation oriented (EO) process simulator (Ishii and Otto, 2011) is employed to decouple the constraints and for maintaining feasibility of the decoupled constraints. The effectiveness and potential of the two-tier SQP approach for reliably and efficiently solving large-scale flowsheet optimization problems are numerically illustrated with fully thermally coupled distillation problems. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： sequential quadratic programming Highly nonlinear constraints Reduced KKT system Flowsheet optimization Equation oriented process simulation Distillation

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Combined lock-in thermography and SQP algorithm for non-intrusive reconstruction of optical and thermal properties in semitransparent medium

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2018年 132卷 446-456页

作者： Sun, Shuangcheng Qi, Hong Zhang, Wenwen Ren, Yatao Ruan, Liming Harbin Inst Technol Sch Energy Sci & Engn 92 West Dazhi St Harbin 150001 Heilongjiang Peoples R China

A combined lock-in thermography (LIT) technique with sequential quadratic programming (SQP) algorithm is proposed for simultaneous reconstruction of the optical and thermal property distributions in a 2D semi-transparent medium. The LIT technique is applied to identify the positions of inclusions in media, in which the discrete correlation method is employed to extract the amplitude and phase angle of thermal wave signals. The SQP algorithm is employed as the main optimization method to simultaneously reconstruct the absorption coefficient, scattering coefficient, and thermal conductivity distributions in the medium. The LIT-SQP technique combines the advantages of rapid identification of inclusion position of the LIT technique and accurate reconstruction of inclusion properties of the SQP algorithm. The inclusions of various positions, shapes, numbers, and sizes are investigated. All the inclusions can be accurately reconstructed by the proposed LIT-SQP technique, which is proved to be more efficient and accurate than the LIT technique and the SQP algorithm alone.

关键词： Optical parameter Thermal conductivity Simultaneous reconstruction Lock-in thermography sequential quadratic programming Absorption coefficient Scattering coefficient

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Reconstruction of Radiative Properties Fields in Participating Media by Using the sequential quadratic Programing Combined With Regularization Technique

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JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME 2019年第2期141卷 022702-022702页

作者： Wei, Lin-Yang Qi, Hong Zhang, Xiao-Luo Wen, Shuang Islam, Md Arafat Ruan, Li-Ming Harbin Inst Technol Sch Energy Sci & Engn Harbin 150001 Heilongjiang Peoples R China Minist Ind & Informat Technol Key Lab Aerosp Thermophys Harbin 150001 Heilongjiang Peoples R China

The refractive index and absorption coefficient fields in participating media are reconstructed simultaneously in this work. In the direct model, the coupled radiation-conduction heat transfer in participating media exposed to a pulse laser irradiation is solved by finite volume method (FVM). In the inverse model, the sequential quadratic programming (SQP) algorithm combined with the generalized Gaussian Markov random field (GGMRF) model is employed to solve the reconstruction problem. It is found that the refractive index and absorption coefficient fields cannot be reconstructed simultaneously. A secondary reconstruction technique based on different regularization parameters is proposed to reconstruct the refractive index and absorption coefficient fields simultaneously. All the retrieval results indicate that the proposed secondary reconstruction technique performs accurately and effectively.

关键词： inverse radiative problem refractive index field absorption coefficient field sequential quadratic programming regularization technique

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Minimization of Cable-Net Reflector Shape Error by Machine Learning

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JOURNAL OF SPACECRAFT AND ROCKETS 2019年第6期56卷 1757-1764页

作者： Tang, Yaqiong Li, Tuanjie Liu, Yang Wang, Zuowei Xidian Univ Sch Mechano Elect Engn POB 188 Xian 710071 Shaanxi Peoples R China

During assembly of a cable-net reflector, surface adjustments must be made to meet the stick accuracy requirement of a space mission by changing the lengths of adjustable cables. It is desirable to find the optimum adjustment amount based on the current state of the cable-net reflector. However, all data needed to establish an accurate simulation model for the cable-net reflector cannot be measured. Therefore, the cable-net reflector is treated as a black box, and a machine learning algorithm (support vector machine) is used to develop a prediction model to establish the relationship between cable length adjustments and surface accuracy. The k-fold cross-validation method is used to estimate the generalization error. The simulated annealing and grid search are combined to get the optimum hyperparameters for the prediction model. Next, a surface adjustment method is developed to calculate the optimal cable lengths. A tension truss reflector example is used to demonstrate the support vector machine prediction model and the adjustment method. The machine learning algorithm identified the relationships between cable lengths and surface accuracy. Both surface accuracy and tension uniformity can be improved by adjusting the boundary cables and tension ties with this method using only information from the front-side nodes.

关键词： Empirical Risk Minimization Trusses Black Box Annealing Space Missions Finite Element Modeling Virtual Prototyping Lagrange Multipliers sequential quadratic programming Neural Networks

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