An interactive fuzzy multi-objective optimization method for engineering design

The coupling of performance functions due to common design variables and uncertainties in an engineering design process will result in difficulties in optimization design problems, such as poor collaboration among design objectives and poor resolution of design conflicts. To handle these problems, a fuzzy interactive multi-objective optimization model is developed based on Pareto solutions, where the metric function and some additional constraints are added to ensure the collaboration among design objectives. The trade-off matrix at the Pareto solutions was developed, and the method for selecting weighting coefficients of optimization objectives is also provided. The proposed method can generate a Pareto optimal set with the maximum satisfaction degree and the minimum distance from ideal solution. The favorable optimal solution can be then selected from the Pareto optimal set by analyzing the trade-off matrix and collaborative sensitivity. Two examples are presented to illustrate the proposed method.     

An intelligent moving object optimization algorithm for design problems with mixed variables, mixed constraints and multiple objectives

This paper presents an optimization algorithm for engineering design problems having a mix of continuous, discrete and integer variables; a mix of linear, non-linear, differentiable, non-differential, equality, inequality and even discontinuous design constraints; and conflicting multiple design objectives. The intelligent movement of objects (vertices and compounds) is simulated in the algorithm based on a Nelder–Mead simplex with added features to handle variable types, bound and design constraints, local optima, search initiation from an infeasible region and numerical instability, which are the common requirements for large-scale, complex optimization problems in various engineering and business disciplines. The algorithm is called an INTElligent Moving Object algorithm and tested for a wide range of benchmark problems. Validation results for several examples, which are manageable within the scope of this paper, are presented herein. Satisfactory results have been obtained for all the test problems, hence, highlighting the benefits of the proposed method.     

一种新的模糊约束满意优化控制算法

将模糊满意度概念与以无穷范数为优化指标的鲁棒预测控制相结合，给出了模糊满意度意义下满意控制的一般算法及适用于一般计算机在线优化的实用算法，解决了优化过程中各种要求(目标、约束)的协调、权衡和折衷问题．仿真结果说明了该算法的有效性．     

Algorithms of discrete optimization and their application to problems with fuzzy coefficients

An approach to solving optimization problems with fuzzy coefficients in objective functions and constraints is described. It consists in formulating and solving one and the same problem within the framework of mutually related models with constructing equivalent analogs with fuzzy coefficients in objective functions alone. It enables one to maximally cut off dominated alternatives “from below” as well as “from above”. Since the approach is applied within the context of fuzzy discrete optimization problems, several modified algorithms of discrete optimization are discussed. These algorithms are associated with the method of normalized functions, are based on a combination of formal and heuristic procedures, and allow one to obtain quasi-optimal solutions after a small number of steps, thus overcoming the computational complexity posed the NP-completeness of discrete optimization problems. The subsequent contraction of the decision uncertainty regions is associated with reduction of the problem to multiobjective decision making in a fuzzy environment with using techniques based on fuzzy preference relations. The techniques are also directly applicable to situations in which the decision maker is required to choose alternatives from a set of explicitly available alternatives. The results of the paper are of a universal character and can be applied to the design and control of systems and processes of different purposes as well as the enhancement of corresponding CAD/CAM systems and intelligent decision making systems. The results of the paper are already being used to solve problems of power engineering.     

The order structure of fuzzy numbers based on the level characteristics and its application to optimization problems

Ranking and comparing fuzzy numbers is an important part in many fuzzy optimization problems such as intelligent control and manufacturing system production line scheduling with uncertainty environments. In this paper, based on the level characteristic function and α-average of level cut sets of fuzzy number, we establish the IMα-metric method for measuring fuzzy number as a whole, and introduce the concept of IDα-difFerence that describes the reliability of IMα-metric value. Further, the basic properties and the separability of IMα-metric and IDα-difference are discussed. Finally, we give a mathematical model to solve fuzzy optimization problems by means of IMα-metric.     

A negotiation methodology for multidisciplinary collaborative product design

The collaborative design of a complicated mechanical product often involves conflicting multidisciplinary objectives, thus one key problem is conflict resolution and coordination among the different disciplines. Since the characteristics such as cooperative competition, professional dependence, compromise, overall utility and so on exist in multidisciplinary collaborative design (MCD), an effective way to gradually eliminate the conflicts among the multiple disciplines and reach an agreement is the negotiation by which a compromise solution that satisfies all parties is got. By comprehensively analyzing the characteristics in MCD and considering the benefit equilibrium among discipline individuals and team, a negotiation strategy is presented, which maximize the union satisfaction degree of system overall objective under the premise of ensuring the higher satisfaction degree level of each discipline’s local objective. A design action of a discipline is abstractly expressed as a concession in the negotiation strategy, and a negotiation model used for MCD is generated by establishing the relation between concession and satisfaction degree. By the relation between satisfaction degree and objective function, the mapping relationship between satisfaction degree domain and physical domain is built to get the design solution. A negotiation process is planned, and a negotiation system framework is designed to support the negotiation among multiple disciplines and assist the different disciplines rapidly reach a consistent compromise solution. A design example of automotive friction clutch is given to illustrate the proposed method.     

模糊多属性决策的相似接近度解法

首先对模糊集合的3种接近度测度,即海明距离、模糊贴近度和灰色关联度进行讨论,在此基础上提出了相似接近度的概念,运用模糊满意度的概念建立了模糊多属性决策的数学模型,其次将相似接近度的概念应用于该模型,提出了该模型的一个新的解法;最后通过数值算例表明,该方法不但十分有效,而且物理意义和数学意义明确,模糊贴近度、灰色关联度和相对接近度解法都是该方法的特例．     

基于模糊决策与进化算法的生产设备布局优化

为解决复杂情况下制造系统的生产设备布局优化问题,提出了一种将模糊决策与进化算法相结合的设备布局优化方法。进一步完善了优化模型,优化目标包括总成本最小、设备相邻要求最大化和面积利用率最大化等优化目标;其中总成本最小目标考虑了物料搬运成本,设备重置导致的设备拆装、移动成本,生产停工造成的产能损失成本。该方法考虑了用户对于成本、利用率及相邻性要求等存在的满意度、优先度等模糊情况,基于模糊决策理论,对多目标优化模型进行了模糊化处理,设计了模糊适应度函数,用以根据用户的优先关系评价pareto解集。基于求解模型的特点,对多目标进化算法的染色体编码方式与交叉、变异等遗传操作方式进行改进,以提高求解该模型的实用性与效率。最后以实际案例的优化结果证明了该方法的有效性。     

Fuzzy two-stage quadratic programming for planning solid waste management under uncertainty

In this study, a fuzzy two-stage quadratic programming (FTSQP) method is developed for planning waste-management systems under uncertainty. It incorporates approaches of fuzzy quadratic programming and two-stage stochastic programming within a general optimization framework, to better reflect uncertainties expressed as probability-density and fuzzy-membership functions. The FTSQP can be used for analyzing various policy scenarios that are associated with different levels of economic penalties when the promised policy targets are violated. Moreover, using fuzzy quadratic terms rather than linear ones, the proposed method can improve upon the existing fuzzy linear programs through (a) more effectively optimizing the general satisfaction of the objective and constraints, (b) minimizing the variation of satisfaction degrees among the constraints and leading to more robust solutions, and (c) reflecting the trade-off between the system cost and the constraint-violation risk. The developed method is applied to a case study of municipal solid waste management. The results indicate that reasonable solutions have been generated. They will allow in-depth analyses of trade-offs between environmental and economic objectives as well as those between system cost and decision-maker's satisfaction degree.     

Integrating linear physical programming within collaborative optimization for multiobjective multidisciplinary design optimization

Multidisciplinary design optimization (MDO) is a concurrent engineering design tool for large-scale, complex systems design that can be affected through the optimal design of several smaller functional units or subsystems. Due to the multiobjective nature of most MDO problems, recent work has focused on formulating the MDO problem to resolve tradeoffs between multiple, conflicting objectives. In this paper, we describe the novel integration of linear physical programming within the collaborative optimization framework, which enables designers to formulate multiple system-level objectives in terms of physically meaningful parameters. The proposed formulation extends our previous multiobjective formulation of collaborative optimization, which uses goal programming at the system and subsystem levels to enable multiple objectives to be considered at both levels during optimization. The proposed framework is demonstrated using a racecar design example that consists of two subsystem level analyses — force and aerodynamics — and incorporates two system-level objectives: (1) minimize lap time and (2) maximize normalized weight distribution. The aerodynamics subsystem also seeks to minimize rearwheel downforce as a secondary objective. The racecar design example is presented in detail to provide a benchmark problem for other researchers. It is solved using the proposed formulation and compared against a traditional formulation without collaborative optimization or linear physical programming. The proposed framework capitalizes on the disciplinary organization encountered during large-scale systems design.     

基于模糊多目标的高超声速飞行器再入轨迹设计

针对多约束条件下的高超声速飞行器再入轨迹的优化问题,考虑多个具有不同重要性等级的优化指标,提出基于模糊多目标的轨迹设计方法.首先,利用直接配点法,将最优控制问题转化为带优先级的非线性多目标规划问题;然后,基于模糊满意优化的思想,根据更重要目标具有更高满意度的原则,将优先级表示为满意度序,并设计两步式优化模型.通过调节参数,能获得同时满足优化和重要性等级要求的最优轨迹.仿真结果表明了所提出方法的有效性.     

Reverse triple Ⅰ method of fuzzy reasoning

A theory of reverse triple I method with sustention degree is presented by using the implication operator R0 in every step of the fuzzy reasoning. Its computation formulas of supremum for fuzzy modus ponens and infimum for fuzzy modus tollens are given respectively. Moreover, through the generalization of this problem, the corresponding formulas of α-reverse triple I method with sustention degree are also obtained. In addition, the theory of reverse triple I method with restriction degree is proposed as well by using the operator R0, and the computation formulas of infimum for fuzzy modus ponens and supremum for fuzzy modus tollens are shown.     

基于熵和改进的协相关度的直觉模糊决策方法

针对决策信息为直觉模糊集且属性权重未知的多属性决策问题,以及关于协相关度的决策方法研究中存在的问题,提出了一种基于直觉模糊熵和改进的协相关度的决策方法。为准确度量直觉模糊集的直觉性和模糊性,给出了一种改进的直觉模糊熵的公式,概括并推广了原有的一类直觉模糊熵的公式,并讨论了其相关性质。然后由概率统计中相关系数的构造思想,改进了直觉模糊集协相关度的定义,构造了直觉模糊集与理想对象之间的相关系数以及得分函数,由此给出了一种改进的基于直觉模糊信息的多属性决策方法,最后通过实例计算验证了该方法的有效性和可行性。     

Intelligent multi-criteria fuzzy group decision-making for situation assessments

Organizational decisions and situation assessment are often made in groups, and decision and assessment processes involve various uncertain factors. To increase efficiently group decision-making, this study presents a new rational–political model as a systematic means of supporting group decision-making in an uncertain environment. The model takes advantage of both rational and political models and can handle inconsistent assessment, incomplete information and inaccurate opinions in deriving the best solution for the group decision under a sequential framework. The model particularly identifies three uncertain factors involved in a group decision-making process: decision makers’ roles, preferences for alternatives, and judgments for assessment-criteria. Based on this model, an intelligent multi-criteria fuzzy group decision-making method is proposed to deal with the three uncertain factors described by linguistic terms. The proposed method uses general fuzzy numbers and aggregates these factors into a group satisfactory decision that is in a most acceptable degree of the group. Inference rules are particularly introduced into the method for checking the consistence of individual preferences. Finally, a real case-study on a business situation assessment is illustrated by the proposed method.     

三角模糊数型不确定多指标决策的可能度关系法

针对指标权重未知的三角模糊数型不确定多指标决策问题, 提出4 种新的三角模糊数比较可能度的等价定义, 并得到一些优良性质关系. 借鉴合作博弈中极大极小算法, 提出一种基于三角模糊数比较可能度关系的指标权重确定方法; 集结所有决策方案比较的可能度, 并对决策方案集进行最优判定和排序, 即可得到三角模糊数型不确定多指标决策的比较可能度关系法. 最后通过算例表明所提出算法的可行性和有效性.

     

General solution to kiln support reactions and multi-objective fuzzy optimization of kiln axis alignment

Based on the analyses of the mechanical features of rotary kiln with multi-supports, a general mechanical model for indeterminate kiln with variable bending rigidities, arbitrary supports and complex loads is established. From this model, the equations of the rotational angle and the deformation are deduced, the general matrix and procedure are developed. The correlation between the roller forces and axis deflections of no. 2 rotary kiln is derived. To improve kiln performance by kiln axis alignment, taking roller forces equilibrium and relative axis deflection minimum as the optimization goal, considering the fuzzy constraints of axis alignment, the fuzzy optimization model of kiln axis alignment is set up. The optimization model is solved with the max–min approach. The results show that fuzzy optimization alignment of rotary kiln can make kiln axis as straight as possible and can distribute kiln loads equally.     

An α-Fuzzy Goal Approximate Algorithm for Solving Fuzzy Multiple Objective Linear Programming Problems

Multiple conflicting objectives in many decision making problems can be well described by multiple objective linear programming (MOLP) models. This paper deals with the vague and imprecise information in a multiple objective problem by fuzzy numbers to represent parameters of an MOLP model. This so-called fuzzy MOLP (or FMOLP) model will reflect some uncertainty in the problem solution process since most decision makers often have imprecise goals for their decision objectives. This study proposes an approximate algorithm based on a fuzzy goal optimization under the satisfactory degree α to handle both fuzzy and imprecise issues. The concept of a general fuzzy number is used in the proposed algorithm for an FMOLP problem with fuzzy parameters. As a result, this algorithm will allow decision makers to provide fuzzy goals in any form of membership functions.     

基于模糊性能指标的广义预测控制器参数调整

针对广义预测控制算法在控制时域中求得的M个控制量，利用模糊模拟技术对系统的约束进行检验，不断修正目标函数中控制量的加权系数，充分利用系统预测控制量的信息，增强系统的鲁棒性，并满足系统的约束。     

A fuzzy particle swarm optimization algorithm for computer communication network topology design

Particle swarm optimization (PSO) is a powerful optimization technique that has been applied to solve a number of complex optimization problems. One such optimization problem is topology design of distributed local area networks (DLANs). The problem is defined as a multi-objective optimization problem requiring simultaneous optimization of monetary cost, average network delay, hop count between communicating nodes, and reliability under a set of constraints. This paper presents a multi-objective particle swarm optimization algorithm to efficiently solve the DLAN topology design problem. Fuzzy logic is incorporated in the PSO algorithm to handle the multi-objective nature of the problem. Specifically, a recently proposed fuzzy aggregation operator, namely the unified And-Or operator (Khan and Engelbrecht in Inf. Sci. 177: 2692–2711, 2007), is used to aggregate the objectives. The proposed fuzzy PSO (FPSO) algorithm is empirically evaluated through a preliminary sensitivity analysis of the PSO parameters. FPSO is also compared with fuzzy simulated annealing and fuzzy ant colony optimization algorithms. Results suggest that the fuzzy PSO is a suitable algorithm for solving the DLAN topology design problem.     

On solutions of fuzzy random multiobjective quadratic programming with applications in portfolio problem

In this paper, a multiobjective quadratic programming problem fuzzy random coefficients matrix in the objectives and constraints and the decision vector are fuzzy variables is considered. First, we show that the efficient solutions fuzzy quadratic multiobjective programming problems series-optimal-solutions of relative scalar fuzzy quadratic programming. Some theorems are to find an optimal solution of the relative scalar quadratic multiobjective programming with fuzzy coefficients, having decision vectors as fuzzy variables. An application fuzzy portfolio optimization problem as a convex quadratic programming approach is discussed and an acceptable solution to such problem is given. At the end, numerical examples are illustrated in the support of the obtained results.