基于数据解析的连退生产过程多因子操作优化

针对连退生产过程中带钢质量波动大和生产能耗过大的问题,基于数据解析方法构建带钢质量的预测模型,进而建立连退生产过程多因子操作优化模型.该模型的任务是求得一个最优工艺参数设定方案,使得模型中所包含的两个相互影响但并不冲突的目标能够实现同时最优化.针对该问题,提出一种改进的自适应多因子进化算法(AdaMFEA),将不同优化目标作为不同类别因子,通过父代解在不同因子上的性能评价指标决定子代解的搜索方向.为了改进算法的鲁棒性和搜索效率,算法使用多种交叉算子,并基于各算子的搜索性能分析提出多种交叉算子的自适应选择机制;同时提出基于回溯直线搜索和拟牛顿法的个体学习策略,对个体进行局部搜索.基于Benchmark问题的实验结果表明,AdaMFEA能够有效提升传统多因子进化算法(MFEA)的求解效率;基于实际工业问题的实验结果表明,AdaMFEA可有效求解连退生产过程多因子操作优化问题,实现多个非冲突目标在一个种群的进化过程中同时达到最优.     

动态分级中心引力约束优化算法及工程应用

结合非固定多段罚函数处理约束条件,提出一种动态分级中心引力优化算法用于求解约束优化问题。该算法利用佳点集初始化个体以保证种群的多样性。在每次迭代过程中将种群分为两个子种群,分别用于全局搜索和局部搜索,根据搜索阶段动态调整子种群个体数目。对几个标准的测试问题和工程优化问题进行数值实验,结果表明该算法能处理不同的约束优化问题。     

Evolutionary Optimization of Machining Processes

Optimization of machining processes plays a key role in meeting the demands for high precision and productivity. The primary challenge for machining process optimization often stems from the fact that the procedure is typically highly constrained and highly non-linear, involving mixed-integer-discrete-continuous design variables. Additionally, machining process models are likely discontinuous, non-explicit, or not analytically differentiable with the design variables. Traditional non-linear optimization techniques are mostly gradient-based, posing many limitations upon application to today’s complex machining models. Genetic Algorithms (GAs) has distinguished itself as a method with the potential for solving highly non-linear, ill-behaved complex machining optimization problems. Unlike traditional optimization techniques, GAs start with a population of different designs and use direct search methods stochastically and deterministically toward optimal and feasible direction. However, GAs still has its own drawbacks when it is applied to machining process optimization, including the lack of efficiency due to its binary representation scheme for continuous design variables, a lack of local fine-tuning capabilities, a lack of a self-adaptation mechanism, and a lack of an effective constraint handling method. A novel and systematic evolutionary algorithm based on GAs is presented in this paper in the areas of problem representation; selection scheme; genetic operators for integer, discrete, and continuous variables; constraint handling method; and population initialization to overcome the underlying drawbacks. The proposed scheme has been applied to two machining problems to demonstrate its superior performance.     

遗传算法优化框架中使用嵌入的混合可视化和数据分析的过程设计优化

非线性、非凸、不连续的数学模型的使用,使得过程优化问题难以求解。虽然确定性方法已经取得了重大的进步,但随机方法,特别是遗传算法提供了一种更有优势的方法。然而,遗传算法的性质决定了其不适合求解带有高约束的问题。本文提出了一个适用于高度约束问题的目标遗传算法,算法中的算子：交叉和变异,是在数据分析步骤得到的关于可行区域和目标函数行为信息的基础上定义。数据分析是以平行坐标系中的可视化描述为基础,一种模式匹配算法,扫描园算法,通过学习向量量化的使用被扩展来自动地确定目标函数和搜索空间的关键特征,这些特征被用于确定遗传算子。对石油稳定问题应用新的目标遗传算法,其结果证明了方法的有用、高效和健壮性。作为数据分析的核心,可视化技术的使用也可以用于解释优化过程得到的结果。     

结合增广Lagrange罚函数的约束优化差分进化算法

利用增广Lagrange罚函数处理问题的约束条件,提出了一种新的约束优化差分进化算法。基于增广Lagrange惩罚函数,将原约束优化问题转换为界约束优化问题。在进化过程中,根据个体的适应度值将种群分为精英种群和普通种群,分别采用不同的变异策略,以平衡算法的全局和局部搜索能力。用10个经典Benchmark问题进行了测试,实验结果表明,该算法能有效地处理不同的约束优化问题。     

组织进化数值优化算法

基于经济学中“组织”的概念 ,该文提出一种新的进化算法———组织进化算法 ,来解决无约束和有约束的数值优化问题 .该算法与传统遗传算法、进化规划、进化策略的运行机制完全不同 ,其进化操作不直接作用于个体上 ,而作用在组织上 ,为此 ,该文定义了三种组织进化算子———分裂算子、吞并算子和合作算子来引导种群进化 .理论分析证明组织进化算法具有全局收敛性 .实验中 ,用 4个无约束和 6个有约束标准函数对算法进行了测试 ,与 3个新算法作了比较 ,并对组织进化算法的性能作了深入分析 .结果表明 ,该文算法无论在解的质量上还是在计算复杂度上都优于其它算法 .对于有约束问题 ,只用了简单的静态罚函数就得到了良好的效果 ,这表明该文算法的搜索机制非常有效 ,不易陷入局部最优 .最后 ,参数分析的结果表明该文算法具有性能稳定、成功率高、对参数不敏感等优越的性能     

Global laminate optimization on geometrically partitioned shell structures

A method aimed at the optimization of locally varying laminates is investigated. The structure is partitioned into geometrical sections. These sections are covered by global plies. A variable-length representation scheme for an evolutionary algorithm is developed. This scheme encodes the number of global plies, their thickness, material, and orientation. A set of genetic variation operators tailored to this particular representation is introduced. Sensitivity information assists the genetic search in the placement of reinforcements and optimization of ply angles. The method is investigated on two benchmark applications. There it is able to find significant improvements. A case study of an airplane’s side rudder illustrates the applicability of the method to typical engineering problems.     

Multi-operator based evolutionary algorithms for solving constrained optimization problems

Over the last two decades, many sophisticated evolutionary algorithms have been introduced for solving constrained optimization problems. Due to the variability of characteristics in different COPs, no single algorithm performs consistently over a range of problems. In this paper, for a better coverage of the problem characteristics, we introduce an algorithm framework that uses multiple search operators in each generation. The appropriate mix of the search operators, for any given problem, is determined adaptively. The framework is tested by implementing two different algorithms. The performance of the algorithms is judged by solving 60 test instances taken from two constrained optimization benchmark sets from specialized literature. The first algorithm, which is a multi-operator based genetic algorithm (GA), shows a significant improvement over different versions of GA (each with a single one of these operators). The second algorithm, using differential evolution (DE), also confirms the benefit of the multi-operator algorithm by providing better and consistent solutions. The overall results demonstrated that both GA and DE based algorithms show competitive, if not better, performance as compared to the state of the art algorithms.     

结合非固定多段罚函数的约束优化进化算法

利用非固定多段映射罚函数的约束条件,提出一种结合非固定多段罚函数的约束优化进化算法。该算法利用佳点集方法初始化种群,以保证其均匀分布在搜索空间中。在进化过程中,对种群进行单形交叉和多样性变异操作产生新的个体,增加种群的多样性。对6个经典Benchmark问题进行测试,实验结果表明,该算法能有效地处理不同的约束优化问题。     

A hybrid evolutionary approach for solving constrained optimization problems over finite domains

A novel approach for the integration of evolution programs and constraint-solving techniques over finite domains is presented. This integration provides a problem-independent optimization strategy for large-scale constrained optimization problems over finite domains. In this approach, genetic operators are based on an arc-consistency algorithm, and chromosomes are arc-consistent portions of the search space of the problem. The paper describes the main issues arising in this integration: chromosome representation and evaluation, selection and replacement strategies, and the design of genetic operators. We also present a parallel execution model for a distributed memory architecture of the previous integration. We have adopted a global parallelization approach that preserves the properties, behavior, and fundamentals of the sequential algorithm. Linear speedup is achieved since genetic operators are coarse grained as they perform a search in a discrete space carrying out arc consistency. The implementation has been tested on a GRAY T3E multiprocessor using a complex constrained optimization problem.     

A hybrid multi-swarm particle swarm optimization to solve constrained optimization problems

In the real-world applications, most optimization problems are subject to different types of constraints. These problems are known as constrained optimization problems (COPs). Solving COPs is a very important area in the optimization field. In this paper, a hybrid multi-swarm particle swarm optimization (HMPSO) is proposed to deal with COPs. This method adopts a parallel search operator in which the current swarm is partitioned into several subswarms and particle swarm optimization (PSO) is severed as the search engine for each sub-swarm. Moreover, in order to explore more promising regions of the search space, differential evolution (DE) is incorporated to improve the personal best of each particle. First, the method is tested on 13 benchmark test functions and compared with three stateof-the-art approaches. The simulation results indicate that the proposed HMPSO is highly competitive in solving the 13 benchmark test functions. Afterward, the effectiveness of some mechanisms proposed in this paper and the effect of the parameter setting were validated by various experiments. Finally, HMPSO is further applied to solve 24 benchmark test functions collected in the 2006 IEEE Congress on Evolutionary Computation (CEC2006) and the experimental results indicate that HMPSO is able to deal with 22 test functions.     

A graph-based framework for model-driven optimization facilitating impact analysis of mutation operator properties

Optimization problems in software engineering typically deal with structures as they occur in the design and maintenance of software systems. In model-driven optimization (MDO), domain-specific models are used to represent these structures while evolutionary algorithms are often used to solve optimization problems. However, designing appropriate models and evolutionary algorithms to represent and evolve structures is not always straightforward. Domain experts often need deep knowledge of how to configure an evolutionary algorithm. This makes the use of model-driven meta-heuristic search difficult and expensive. We present a graph-based framework for MDO that identifies and clarifies core concepts and relies on mutation operators to specify evolutionary change. This framework is intended to help domain experts develop and study evolutionary algorithms based on domain-specific models and operators. In addition, it can help in clarifying the critical factors for conducting reproducible experiments in MDO. Based on the framework, we are able to take a first step toward identifying and studying important properties of evolutionary operators in the context of MDO. As a showcase, we investigate the impact of soundness and completeness at the level of mutation operator sets on the effectiveness and efficiency of evolutionary algorithms.

     

An effective hybrid optimization strategy for job-shop scheduling problems

Simulated annealing is a naturally serial algorithm, but its behavior can be controlled by the cooling schedule. Genetic algorithm exhibits implicit parallelism and can retain useful redundant information about what is learned from previous searches by its representation in individuals in the population, but GA may lose solutions and substructures due to the disruptive effects of genetic operators and is not easy to regulate GA's convergence. By reasonably combining these two global probabilistic search algorithms, we develop a general, parallel and easily implemented hybrid optimization framework, and apply it to job-shop scheduling problems. Based on effective encoding scheme and some specific optimization operators, some benchmark job-shop scheduling problems are well solved by the hybrid optimization strategy, and the results are competitive with the best literature results. Besides the effectiveness and robustness of the hybrid strategy, the combination of different search mechanisms and structures can relax the parameter-dependence of GA and SA.Scope and purposeJob-shop scheduling problem (JSP) is one of the most well-known machine scheduling problems and one of the strongly NP-hard combinatorial optimization problems. Developing effective search methods is always an important and valuable work. The scope and purpose of this paper is to present a parallel and easily implemented hybrid optimization framework, which reasonably combines genetic algorithm with simulated annealing. Based on effective encoding scheme and some specific optimization operators, the job-shop scheduling problems are well solved by the hybrid optimization strategy.     

求解多车型校车路径问题的混合集合划分的GRASP算法

针对不同规划场景下具有不同优化目标的多车型校车路径问题(HSBRP),提出一种混合集合划分(SP)的贪婪随机自适应(Greedy Randomized Adaptive Search Procedure,GRASP)算法。根据GRASP算法寻优过程中产生的路径信息构建SP模型,然后使用CPLEX精确优化器对SP模型进行求解。为了适应不同类型的HSBRP问题,改进GRASP的初始解构造函数得到一个可行解,并将其对应的路径放入路径池;在局部搜索过程中应用多种邻域结构和可变邻域下降(VND)来提升解的质量,同时在路径池中记录在搜索过程中得到提升的路径和在每次迭代中得到局部最好解的路径信息。使用基准测试案例进行测试,实验结果表明在GRASP算法中,混合SP能够有效地提高算法的求解性能和稳定性,并且该算法能适应不同优化目标下车型混合和车辆数限制两类HSBRP的求解;与现有算法的比较结果再次验证了所提算法的有效性。     

A hybrid cooperative search algorithm for constrained optimization

Many engineering design problems can be formulated as constrained optimization problems which often consist of many mixed equality and inequality constraints. In this article, a hybrid coevolutionary method is developed to solve constrained optimization problems formulated as min–max problems. The new method is fast and capable of global search because of combining particle swarm optimization and gradient search to balance exploration and exploitation. It starts by transforming the problem into unconstrained one using an augmented Lagrangian function, then using two groups to optimize different components of the solution vector in a cooperative procedure. In each group, the final stage of the search procedure is accelerated by via a simple local search method on the best point reached by the preceding exploration based search. We validated the effectiveness and robustness of the proposed algorithm using several engineering problems taken from the specialised literature.     

Simulating non-stationary operators in search algorithms

In this paper, we propose new scenarios for simulating search operators whose behaviors often change continuously during the search. In these scenarios, the performance of such operators decreases while they are applied. This is motivated by the fact that operators for optimization problems are often roughly classified into exploitation and exploration operators. Our simulation model is used to compare the performances of operator selection policies and to identify their ability to handle specific non-stationary operators. An experimental study highlights respective behaviors of operator selection policies when faced to such non-stationary search scenarios.     

Parallel decomposition of combinatorial optimization problems using electro-optical vector by matrix multiplication architecture

A new state space representation for a class of combinatorial optimization problems, related to minimal Hamiltonian cycles, enables efficient implementation of exhaustive search for the minimal cycle in optimization problems with a relatively small number of vertices and heuristic search for problems with large number of vertices. This paper surveys structures for representing Hamiltonian cycles, the use of these structures in heuristic optimization techniques, and efficient mapping of these structures along with respective operators to a newly proposed electrooptical vector by matrix multiplication (VMM) architecture. Record keeping mechanisms are used to improve solution quality and execution time of these heuristics using the VMM. Finally, the utility of a low-power VMM based implementation is evaluated.     

AORCEA – An adaptive operator rate controlled evolutionary algorithm

When applying evolutionary algorithms to optimization problems many different strategy parameters have to be set to define the behavior of the evolutionary algorithm itself. To a certain extent these strategy parameter values determine whether the algorithm is capable of finding a near-optimum solution or not. In particular the choice of the different genetic operators and their relative rates is most often based on experience. Furthermore, the operator rates are defined before starting the optimization runs and remain unchanged until the stopping criterion is reached. Controlling the parameter values during the run has the potential of adjusting the algorithm to the problem while solving the problem. This paper investigates an adaptive strategy controlling the rates of arbitrary chosen genetic operators. The control mechanism is based on the state of the optimization by evaluating a success and a diversity measure for each operator. More efficient operators are favored in order to find better solutions with less evaluations. The algorithm is tested with constrained and unconstrained numerical examples and a concrete structural optimization problem is treated.     

A parallel boundary search particle swarm optimization algorithm for constrained optimization problems

During the past decade, considerable research has been conducted on constrained optimization problems (COPs) which are frequently encountered in practical engineering applications. By introducing resource limitations as constraints, the optimal solutions in COPs are generally located on boundaries of feasible design space, which leads to search difficulties when applying conventional optimization algorithms, especially for complex constraint problems. Even though penalty function method has been frequently used for handling the constraints, the adjustment of control parameters is often complicated and involves a trial-and-error approach. To overcome these difficulties, a modified particle swarm optimization (PSO) algorithm named parallel boundary search particle swarm optimization (PBSPSO) algorithm is proposed in this paper. Modified constrained PSO algorithm is adopted to conduct global search in one branch while Subset Constrained Boundary Narrower (SCBN) function and sequential quadratic programming (SQP) are applied to perform local boundary search in another branch. A cooperative mechanism of the two branches has been built in which locations of the particles near boundaries of constraints are selected as initial positions of local boundary search and the solutions of local boundary search will lead the global search direction to boundaries of active constraints. The cooperation behavior of the two branches effectively reinforces the optimization capability of the PSO algorithm. The optimization performance of PBSPSO algorithm is illustrated through 13 CEC06 test functions and 5 common engineering problems. The results are compared with other state-of-the-art algorithms and it is shown that the proposed algorithm possesses a competitive global search capability and is effective for constrained optimization problems in engineering applications.     

Design of graph-based evolutionary algorithms: a case study for chemical process networks

This paper describes the adaptation of evolutionary algorithms (EAs) to the structural optimization of chemical engineering plants, using rigorous process simulation combined with realistic costing procedures to calculate target function values. To represent chemical engineering plants, a network representation with typed vertices and variable structure will be introduced. For this representation, we introduce a technique on how to create problem specific search operators and apply them in stochastic optimization procedures. The applicability of the approach is demonstrated by a reference example. The design of the algorithms will be oriented at the systematic framework of metric-based evolutionary algorithms (MBEAs). MBEAs are a special class of evolutionary algorithms, fulfilling certain guidelines for the design of search operators, whose benefits have been proven in theory and practice. MBEAs rely upon a suitable definition of a metric on the search space. The definition of a metric for the graph representation will be one of the main issues discussed in this paper. Although this article deals with the problem domain of chemical plant optimization, the algorithmic design can be easily transferred to similar network optimization problems. A useful distance measure for variable dimensionality search spaces is suggested.