An asymmetric multileveled symbiotic evolutionary algorithm for integrated FMS scheduling

This paper considers the integrated FMS (flexible manufacturing system) scheduling problem (IFSP) consisting of loading, routing, and sequencing subproblems that are interrelated to each other. In scheduling FMS, the decisions for the subproblems should be appropriately made to improve resource utilization. It is also important to fully exploit the potential of the inherent flexibility of FMS. In this paper, a symbiotic evolutionary algorithm, named asymmetric multileveled symbiotic evolutionary algorithm (AMSEA), is proposed to solve the IFSP. AMSEA imitates the natural process of symbiotic evolution and endosymbiotic evolution. Genetic representations and operators suitable for the subproblems are proposed. A neighborhood-based coevolutionary strategy is employed to maintain the population diversity. AMSEA has the strength to simultaneously solve subproblems for loading, routing, and sequencing and to easily handle a variety of FMS flexibilities. The extensive experiments are carried out to verify the performance of AMSEA, and the results are reported.     

A hybrid genetic algorithm for the single machine scheduling problem with sequence-dependent setup times

This paper presents a hybrid approach based on the integration between a genetic algorithm (GA) and concepts from constraint programming, multi-objective evolutionary algorithms and ant colony optimization for solving a scheduling problem. The main contributions are the integration of these concepts in a GA crossover operator. The proposed methodology is applied to a single machine scheduling problem with sequence-dependent setup times for the objective of minimizing the total tardiness. A sensitivity analysis of the hybrid approach is carried out to compare the performance of the GA and the hybrid genetic algorithm (HGA) approaches on different benchmarks from the literature. The numerical experiments demonstrate the HGA efficiency and effectiveness which generates solutions that approach those of the known reference sets and improves several lower bounds.     

基于正态云模型的状态转移算法求解多目标柔性作业车间调度问题

为了求解具有多目标多约束的柔性作业车间调度问题,提出一种基于正态云模型的状态转移算法.构建以最小化最大完工时间、机器总负荷及瓶颈机器负荷为目标的多目标柔性作业车间调度问题的数学模型;针对灰熵关联度适应度分配策略在Pareto解比较序列与参考序列之间的差值相等时不能引导算法进化的情况,提出一种改进灰熵关联度的适应度值分配策略;同时引入兼具模糊性和随机性的云模型进化策略以改进状态转移算法,可有效避免算法早熟并增加候选解的多样性.仿真结果表明:基于正态云模型的状态转移算法能够有效解决多目标柔性作业车间调度问题;与其他算法相比,所提出算法求解问题的收敛精度更高、收敛速度更快.     

利用优势元素改进进化算法求解柔性作业调度

进化算法进化过程中种群多样性的降低导致的收敛极大限制了进化算法的求解质量与搜索效率,通过扩大搜索规模并不能有效提高算法求解质量。在共生进化算法求解柔性作业调度的基础上,研究进化算法在较大搜索规模下的种群状态进化过程,并在进化过程向种群内批量加入优势元素,调整种群模式构成。仿真实验表明：与传统进化算法相比,进化过程中加入优势元素能有效提高算法的求解质量与搜索效率,在较短的时间内能得到较好的解,并且在较大搜索规模时表现了更好的搜索性能。     

Hybridizing a multi-objective simulated annealing algorithm with a multi-objective evolutionary algorithm to solve a multi-objective project scheduling problem

In this paper, a multi-objective project scheduling problem is addressed. This problem considers two conflicting, priority optimization objectives for project managers. One of these objectives is to minimize the project makespan. The other objective is to assign the most effective set of human resources to each project activity. To solve the problem, a multi-objective hybrid search and optimization algorithm is proposed. This algorithm is composed by a multi-objective simulated annealing algorithm and a multi-objective evolutionary algorithm. The multi-objective simulated annealing algorithm is integrated into the multi-objective evolutionary algorithm to improve the performance of the evolutionary-based search. To achieve this, the behavior of the multi-objective simulated annealing algorithm is self-adaptive to either an exploitation process or an exploration process depending on the state of the evolutionary-based search. The multi-objective hybrid algorithm generates a number of near non-dominated solutions so as to provide solutions with different trade-offs between the optimization objectives to project managers. The performance of the multi-objective hybrid algorithm is evaluated on nine different instance sets, and is compared with that of the only multi-objective algorithm previously proposed in the literature for solving the addressed problem. The performance comparison shows that the multi-objective hybrid algorithm significantly outperforms the previous multi-objective algorithm.     

Multileveled Symbiotic Evolutionary Algorithm: Application to FMS Loading Problems

Recently, there has been an increasing effort to address integrated problems that are composed of multiple interrelated sub-problems. Many integrated problems in the real world have a multileveled structure. This paper proposes a new method of solving integrated and multileveled problems. The proposed method is named Multileveled Symbiotic Evolutionary Algorithm (MSEA). MSEA is an evolutionary algorithm that imitates the process of symbiotic evolution, including endosymbiotic evolution. It is designed to promote the balance of population diversity and population convergence. To verify its applicability, MSEA is applied to loading problems of flexible manufacturing systems with various flexibilities. Through computer experiments, the features of MSEA are shown and their effects on search capability are discussed. The proposed algorithm is also compared with existing ones in terms of solution quality. The experimental results confirm the effectiveness of our approach.     

Multi-objective mobile robot path planning problem through learnable evolution model

A new multi-objective non-Darwinian-type evolutionary computation approach based on learnable evolution model (LEM) is proposed for solving the robot path planning problem. The multi-objective property of this approach is governed by a robust strength Pareto evolutionary algorithm (SPEA) incorporated in the LEM algorithm presented here. Learnable evolution model includes a machine learning method, like the decision trees, that can detect the right directions of the evolution and leads to large improvements in the fitness of the individuals. Several new refiner operators are proposed to improve the objectives of the individuals in the evolutionary process. These objectives are: the path length, the path safety and the path smoothness. A modified integer coding path representation scheme is proposed where the edge-fixing and top-row fixing procedures are performed implicitly. This proposed robot path planning problem solving approach is assessed on eight realistic scenarios in order to verify the performance thereof. Computer simulations reveal that this proposed approach exhibits much higher hypervolume and set coverage in comparison with other similar approaches. The experimental results confirm that the proposed approach performs in the workspaces with a dense set of obstacles in a significant manner.     

基于模糊物元模型的高维多目标FJSP研究*

为解决高维多目标柔性作业车间调度问题,提出了一种基于模糊物元模型与粒子群算法的模糊粒子群算法（Fuzzy Particle Swarm Optimization,FPSO）。该算法以模糊物元分析理论为依据,采用复合模糊物元与基准模糊物元之间的欧式贴近度作为适应度值引导粒子群算法的进化,并引入具有容量限制的外部存储器保留较优的Pareto非支配解以供决策者选择。此外,构建了优化目标为最大完工时间、设备总负荷、加工成本、最大设备负荷与加工质量的高维多目标优化模型,并以Kacem基准问题与实际生产数据为例进行仿真模拟与对比分析。结果表明,该算法具有良好的收敛性且搜索到的非支配解分布性较好,能够有效地应用于求解高维多目标柔性作业车间调度问题。     

改进混沌烟花算法的多目标调度优化研究

为满足生产中的不同需求,以最小化完成时间、最小化工件总延期时间、最小化机器总空闲时间为目标函数,建立多目标优化模型。提出一种改进混沌烟花算法,通过逻辑自映射产生混沌序列避免算法陷入局部最优,并设计了一种双元锦标赛与动态淘汰制相结合的帕累托非劣解集的构造方法。通过对六个不同规模标准问题的仿真测试,验证了该算法在求解多目标作业车间问题时具有较高求解精度和稳定性。     

Multi-objective evolutionary algorithms based on the summation of normalized objectives and diversified selection

Most multi-objective evolutionary algorithms (MOEAs) use the concept of dominance in the search process to select the top solutions as parents in an elitist manner. However, as MOEAs are probabilistic search methods, some useful information may be wasted, if the dominated solutions are completely disregarded. In addition, the diversity may be lost during the early stages of the search process leading to a locally optimal or partial Pareto-front. Beside this, the non-domination sorting process is complex and time consuming. To overcome these problems, this paper proposes multi-objective evolutionary algorithms based on Summation of normalized objective values and diversified selection (SNOV-DS). The performance of this algorithm is tested on a set of benchmark problems using both multi-objective evolutionary programming (MOEP) and multi-objective differential evolution (MODE). With the proposed method, the performance metric has improved significantly and the speed of the parent selection process has also increased when compared with the non-domination sorting. In addition, the proposed algorithm also outperforms ten other algorithms.     

Scheduling of short-term hydrothermal energy system by parallel multi-objective differential evolution

With the growing concerns on energy and environment, the short-term hydrothermal scheduling (SHTS) which minimizes the fuel cost and pollutant emission simultaneously is playing an increasing important role in the modern electric power system. Due to the complicated operation constraints and objectives, SHTS is classified as a multi-objective optimization problem. Thus, to efficiently resolve this problem, this paper develops a novel parallel multi-objective differential evolution (PMODE) combining the merits of parallel technology and multi-objective differential evolution. In PMODE, the population with larger size is first divided into several smaller subtasks to be concurrently executed in different computing units, and then the main thread collects the results of each subpopulation to form the final Pareto solutions set for the SHTS problem. During the evolutionary process of each subpopulation, the mutation crossover and selection operators are modified to enhance the performance of population. Besides, an external archive set is used to conserve the Pareto solutions and provide multiple evolutionary directions for individuals, while the constraint handling method is introduced to address the complicated operational constraints. The results from a mature hydrothermal system indicate that when compared with several existing methods, PMODE can obtain satisfactory solutions in both fuel cost and environmental pollutant, which is an effective tool to generate trade-off schemes for the hydrothermal scheduling problem.     

基于改进的遗传算法的多目标优化问题研究

研究多目标优化算法问题,针对传统的多目标优化算法由于计算复杂度非常高,难以获得令人满意的解等问题,在图论和遗传算法基础上,提出了一种改进的遗传算法求解多目标优化方法。首先采用二进制编码表示最小树问题,然后采用深度优先搜索算法进行图的连通性判断,给出了一种新的适应度函数,以提高算法执行速度和进化效率。最后仿真结果表明,与经典的Prim算法和Kruskal算法相比,新算法复杂度较低,并能在第一次遗传进化过程中获得一批最小生成树,适合于解决不同类型的多目标最小树问题。     

基于权重学习的高维多目标进化算法

在多目标进化算法解决多目标优化问题的过程中,随着目标个数的增加,种群个体进化方向的盲目性逐渐显露出来,同时还存在着收敛性和多样性难以平衡的问题。针对以上两个问题,以基于参考点策略的快速非支配排序遗传算法NSGA-Ⅲ为框架,分别从产生候选解和选择候选解两个角度进行算法改进,从而得到一个新的进化算法WL-NSGAⅢ。在新算法的匹配选择阶段,设计了一种基于权重的个体学习策略,即利用种群信息构建代内关系为种群个体提供进化方向并增加候选解集的收敛性。同时,在新算法的环境选择阶段,利用权重信息对小生境选择策略进行改进。为了验证新算法的有效性,通过模拟实验将新算法与现有算法在DTLZ问题测试集中进行比较。仿真结果表明,新算法在大多数基准问题上具有良好的效果。     

基于项集归减的高维频繁高效用项集挖掘多目标优化方法

频繁高效用项集挖掘是数据挖掘的一项重要任务,挖掘到的项集由支持度和效用这2个指标衡量.在一系列用于解决这类问题的方法中,进化多目标方法能够提供1组高质量解以满足不同用户的需求,避免传统算法中支持度和效用的阈值难以确定的问题.但是已有多目标算法多采用0-1编码,使得决策空间的维度与数据集中项数成正比,因此,面对高维数据集会出现维度灾难问题.鉴于此,设计一种项集归减策略,通过在进化过程中不断对不重要项进行归减以减小搜索空间.基于此策略,进而提出一种基于项集归减的高维频繁高效用项集挖掘多目标优化算法(IR-MOEA),并针对可能存在的归减过度或未归减到位的个体提出基于学习的种群修复策略用以调整进化方向.此外还提出一种基于项集适应度的初始化策略,使得算法在进化初期生成利于后期进化的稀疏解.多个数据集上的实验结果表明,所提出算法优于现有的多目标优化算法,特别是在高维数据集上.     

基于参数动态调整的多目标差分进化算法

针对多目标差分进化算法最优解难以获取的问题,提出一种基于参数动态调整的多目标差分进化(AMODE)算法.AMODE算法通过设计变异率和交叉率的自适应调整策略,实现进化过程中变异率和交叉率的动态调整,均衡多目标差分进化算法的局部搜索能力和全局探索能力,获得收敛性、多样性和均匀性较好的最优解.实验结果表明,基于参数动态调整的AMODE算法能够有效改善多目标差分进化算法的逼近能力(IGD)和均匀性(SP),具有较好的优化效果.     

Multi-objective optimisation and decision-making of space station logistics strategies

Space station logistics strategy optimisation is a complex engineering problem with multiple objectives. Finding a decision-maker-preferred compromise solution becomes more significant when solving such a problem. However, the designer-preferred solution is not easy to determine using the traditional method. Thus, a hybrid approach that combines the multi-objective evolutionary algorithm, physical programming, and differential evolution (DE) algorithm is proposed to deal with the optimisation and decision-making of space station logistics strategies. A multi-objective evolutionary algorithm is used to acquire a Pareto frontier and help determine the range parameters of the physical programming. Physical programming is employed to convert the four-objective problem into a single-objective problem, and a DE algorithm is applied to solve the resulting physical programming-based optimisation problem. Five kinds of objective preference are simulated and compared. The simulation results indicate that the proposed approach can produce good compromise solutions corresponding to different decision-makers’ preferences.     

一种多目标人工蜂群算法

为将标准人工蜂群算法有效应用到多目标优化问题中,设计了一种多目标人工蜂群算法。其进化策略在利用精英解引导搜索的同时结合正弦函数搜索操作来平衡算法对解空间的开发与开采行为。另外,算法借助了外部集合来记录与维护种群进化过程中产生的Pareto最优解。理论分析表明:针对多目标优化问题,本算法能收敛到理论最优解集合。对典型多目标测试问题的仿真实验结果表明:本算法能有效逼近理论最优,具有较好的收敛性和均匀性,并且与同类型算法相比,本算法具有良好的求解性能。     

一种改进的多目标约束优化差分进化算法

提出一种新的多目标优化差分进化算法用于求解约束优化问题.该算法利用佳点集方法初始化个体以维持种群的多样性.将约束优化问题转化为两个目标的多目标优化问题.基于Pareto支配关系,将种群分为Pareto子集和Non-Pareto子集,结合差分进化算法两种不同变异策略的特点,对Non-Pareto子集和Pareto子集分别采用DE/best/1变异策略和DE/rand/1变异策略.数值实验结果表明该算法具有较好的寻优效果.     

复杂并行机调度问题基于分解的优化算法

针对纺织生产过程中广泛存在的带特殊工艺约束的大规模并行机调度问题，提出了一种基于分解的优化算法。首先将原调度问题分解为机台选择和工件排序两个子问题，然后针对机台选择子问题提出一种进化规划算法，并采用一种具有多项式时间复杂度的最优算法求解工件排序子问题，以得到问题特征信息（即每台机器对应拖期工件数的最小值），该问题特征信息用以指导进化规划算法的迭代过程。不同规模并行机调度问题的数值计算结果及实际制造企业应用效果表明，本文提出的算法是有效的。     

Multi-objective self-adaptive differential evolution with elitist archive and crowding entropy-based diversity measure

A self-adaptive differential evolution algorithm incorporate Pareto dominance to solve multi-objective optimization problems is presented. The proposed approach adopts an external elitist archive to retain non-dominated solutions found during the evolutionary process. In order to preserve the diversity of Pareto optimality, a crowding entropy diversity measure tactic is proposed. The crowding entropy strategy is able to measure the crowding degree of the solutions more accurately. The experiments were performed using eighteen benchmark test functions. The experiment results show that, compared with three other multi-objective optimization evolutionary algorithms, the proposed MOSADE is able to find better spread of solutions with better convergence to the Pareto front and preserve the diversity of Pareto optimal solutions more efficiently.