可重入混合流水车间调度的拉格朗日松弛算法

为了有效提升多重入车间的生产效率,考虑了实际生产中检查和修复过程对于逐层制造的可重入生产系统的重要性,提出了基于拉格朗日松弛算法的可重入混合流水车间的调度方法.首先进行了问题域的描述,并在此基础上以最小化加权完成时间为调度目标,建立数学规划模型.针对该调度问题提出了基于松弛机器能力约束的拉格朗日松弛算法,使松弛问题分解成工件级子问题,并使用动态规划方法建立递归公式,求解工件级子问题.随后,使用次梯度算法求解拉格朗日对偶问题.最后,对各种不同问题规模进行了仿真实验,结果表明,所提出的调度算法能够在合理的时间内获得满意的近优解.     

带运输考虑的多阶段动态可重入混合流水车间调度

可重入混合流水车间调度允许一个工件多次进入某些加工阶段,它广泛出现在许多工业制造过程中,如半导体制造、印刷电路板制造等.本文研究了带运输时间的多阶段动态可重入混合流水车间问题,目标是最小化总加权完成时间.针对该问题,建立了整数规划模型,进而基于工件解耦方式提出了两种改进的拉格朗日松弛(LR)算法.在这些算法中,设计了动态规划的改进策略以加速工件级子问题的求解,提出了异步次梯度法以得到有效的乘子更新方向.测试结果说明了所提出的两种改进算法在解的质量和运行时间方面均优于常规LR算法,两种算法都能在可接受的计算时间内得到较好的近优解.     

区间数可重入混合流水车间调度与预维护协同优化

针对加工时间不确定的可重入混合流水车间调度与预维护协同优化问题,构建以区间最大完工时间、区间总碳排放和区间总预维护费用为优化目标的集成调度模型.针对问题特性,通过设计改进的可能度计算方法,定义区间意义下解的Pareto占优关系.提出一种改进的离散鲸鱼群算法,通过同步调度与维护策略,实现制造与维护的联合优化;设计个体间距...     

带线性恶化工件的零等待流水车间调度

研究了以最小化总加权完成时间为目标的带线性恶化工件的零等待流水车间调度,其中工件的加工时间表示为开始时间的线性恶化函数,每个工件在不同机器有各自的恶化率.为了对该问题进行求解,提出了一种融合CDS启发式算法、局部搜索和自适应遗传算法的混合启发式算法.引入CDS启发式算法改善初始工件加工序列群,设计遗传参数自适应更新策略...     

混合流水车间调度的遗传下降算法

针对混合流水车间调度问题(Hybrid Flow Shop Scheduling,HFSS)建立了混合整数规划模型,提出了遗传下降算法(Genetic Descent Algorithm,GDA).GDA与HFSS工件在机器上最优分配规则相结合,不但能够产生初始可行解,而且保证交叉和变异后解仍然可行;同时在遗传算法中嵌入邻域下降策略.为了验证GDA算法的有效性,随机产生了230组数据进行实验.实验结果表明:对于HFSS问题,在小规模情况下,GDA算法与最优解之间的平均偏差为0.1%;对于较大规模的情况,GDA比NEH算法平均改进10.45%.     

求解混合流水车间调度问题的一种遗传算法

由于高度的计算复杂性(NP-hard问题),混合流水车间调度问题很难求得最优解,启发式算法和智能优化算法(如遗传算法)求解此类问题的近优解的有效性和实用性已被证实。该文提出了一种基于遗传算法的求解方法,在由染色体转换成可行调度的过程中引入工件插入方法,同时设计了一种新的交叉算子。通过大量的数值计算表明,该算法的优化质量大大优于传统的遗传算法和NEH启发式算法。     

改进果蝇算法求解混合流水车间调度问题

针对混合流水车间调度问题(HFSP),本文提出了一种新的基于果蝇算法和变邻域搜索的混合优化方法.首先,将关键块内的工序与同阶段其他机器上的工序进行交换,提出了一种基于关键路径的HFSP新邻域结构.其次,针对HFSP的阶段式解码特性,提出了一种邻域解的快速评估方法,并验证了快速评估方法的高效性.然后,基于提出的新邻域结构,并将N7和K-insertion邻域结构引入HFSP,设计了基于上述3种邻域结构的变邻域搜索方法,以此为基础提出了一种针对HFSP的混合优化方法.最后,通过对Carlier和Liao等经典测试集进行测试,验证了所提新邻域结构的可行性和有效性,并将该方法与其他文献的方法进行了对比,验证了所提方法的优越性.     

求解混合流水车间调度问题的离散布谷鸟算法

为求解混合流水车间调度问题,提出一种离散布谷鸟算法。针对常规解码方法难以获得最优解的缺点,提出一种改进的解码方法,基于工件数与并行机数,按概率随机分配机器;根据标准布谷鸟算法中莱维飞行和巢寄生行为两种位置更新策略的核心思想,提出基于位置交叉和个体距离的离散莱维飞行,设计基于最优插入和最优交换的巢寄生策略。最后算例对比实验结果显示,采用基于改进解码方法的离散布谷鸟算法求解所得结果的平均值最小,验证了改进解码方法能提高解的质量;实例测试所得结果均获得了当前最优解,验证了离散布谷鸟算法求解该类问题的优越性。     

时间约束混合流水车间调度问题综述

车间调度是智能制造领域中的核心问题之一,在经典流水车间调度中,所有工件按照相同的加工顺序在指定机床上加工.混合流水车间调度(HFS)作为流水车间调度的特例,相比前者增加了机床选择的灵活性,可以显著优化系统目标,但同时也增加了问题求解的难度.由于时间约束HFS相比基本HFS问题更贴近实际生产过程,近年来,综合考虑各类时间相关约束的HFS问题得到了深入研究.因此,本文围绕基本HFS、有限等待时间HFS、带准备时间HFS、模糊/随机加工时间HFS、多时间约束HFS、时间约束相关多目标HFS等问题开展研究.针对每一类时间约束HFS问题,按照问题规模对当前研究成果进行分类描述,按照确定性算法、启发式方法、元启发式方法、算法混合对相关成果进行算法分类,按照实际工业应用对文献进行归类分析.另一方面,围绕交货期、能耗、成本等3类性能指标,分析了在各类时间约束HFS问题中的多目标优化相关成果.最后详细分析了带时间约束HFS问题在问题层面、算法层面和应用层面存在的挑战性问题和未来研究的方向.     

求解总拖期时间最小化流水车间调度问题的多智能体进化算法

针对总拖期时间最小化的置换流水车间调度问题（Total tardiness permutation flow-shop scheduling problem） 提出了一种基于多智能体的进化搜索算法. 在该算法中,采用基于延迟时间排序的学习搜索策略（Tardiness rank based learning）,快速产生高质量的新个体,并根据概率更新模型进行智能体网格的更新进化. 同时通过实验设计的方法探讨了算法参数设置对算法性能的影响. 为了验证算法的性能,求解了Vallada标准测试集中540个测试问题,并将测试结果与一些代表算法进行比较,验证了该算法的有效性.     

A new Lagrangian relaxation algorithm for hybrid flowshop scheduling to minimize total weighted completion time

We investigate the problem of scheduling n jobs in s-stage hybrid flowshops with parallel identical machines at each stage. The objective is to find a schedule that minimizes the sum of weighted completion times of the jobs. This problem has been proven to be NP-hard. In this paper, an integer programming formulation is constructed for the problem. A new Lagrangian relaxation algorithm is presented in which precedence constraints are relaxed to the objective function by introducing Lagrangian multipliers, unlike the commonly used method of relaxing capacity constraints. In this way the relaxed problem can be decomposed into machine type subproblems, each of which corresponds to a specific stage. A dynamic programming algorithm is designed for solving parallel identical machine subproblems where jobs may have negative weights. The multipliers are then iteratively updated along a subgradient direction. The new algorithm is computationally compared with the commonly used Lagrangian relaxation algorithms which, after capacity constraints are relaxed, decompose the relaxed problem into job level subproblems and solve the subproblems by using the regular and speed-up dynamic programming algorithms, respectively. Numerical results show that the new Lagrangian relaxation method produces better schedules in much shorter computation time, especially for large-scale problems.     

Two-machine flowshop scheduling problem with bounded processing times to minimize total completion time

We consider the two-machine flowshop scheduling problem where jobs have random processing times which are bounded within certain intervals. The objective is to minimize total completion time of all jobs. The decision of finding a solution for the problem has to be made based on the lower and upper bounds on job processing times since this is the only information available. The problem is NP-hard since the special case when the lower and upper bounds are equal, i.e., the deterministic case, is known to be NP-hard. Therefore, a reasonable approach is to come up with well performing heuristics. We propose eleven heuristics which utilize the lower and upper bounds on job processing times based on the Shortest Processing Time (SPT) rule. The proposed heuristics are compared through randomly generated data. The computational analysis has shown that the heuristics using the information on the bounds of job processing times on both machines perform much better than those using the information on one of the two machines. It has also shown that one of the proposed heuristics performs as the best for different distributions with an overall average percentage error of less than one.     

The two-machine flowshop no-wait scheduling problem with a single server to minimize the total completion time

This work studies the scheduling problem where a set of jobs are available for processing in a no-wait and separate setup two-machine flow shop system with a single server. The no-wait constraint requires that the operations of a job have to be processed continuously without waiting between two machines. The setup time is incurred and attended by a single sever which can perform one setup at a time. The performance measure considered is the total completion time. The problem is strongly NP-hard. Optimal solutions for several restricted cases and some properties for general case are proposed. Both the heuristic and the branch and bound algorithms are established to tackle the problem. Computational experiments indicate that the heuristic and the branch and bound algorithm are superior to the existing ones in term of solution quality and number of branching nodes, respectively.     

Two-machine flowshop scheduling with truncated learning to minimize the total completion time

Scheduling with learning effects has received a lot of research attention lately. However, the flowshop setting is relatively unexplored. On the other hand, the actual processing time of a job under an uncontrolled learning effect will drop to zero precipitously as the number of jobs increases. This is rather absurd in reality. Motivated by these observations, we consider a two-machine flowshop scheduling problem in which the actual processing time of a job in a schedule is a function of the job’s position in the schedule and a control parameter of the learning function. The objective is to minimize the total completion time. We develop a branch-and-bound and three simulated annealing algorithms to solve the problem. Computational results show that the proposed algorithms are efficient in producing near-optimal solutions.     

The 2-stage assembly flowshop scheduling problem with total completion time: Efficient constructive heuristic and metaheuristic

In this paper, we address the 2-stage assembly scheduling problem where there are m machines in the first stage to manufacture the components of a product and one assembly station (machine) in the second stage. The objective considered is the minimisation of the total completion time. Since the NP-hard nature of this problem is well-established, most previous research has focused on finding approximate solutions in reasonable computation time. In our paper, we first review and derive a number of problem properties and, based on these ideas, we develop a constructive heuristic that outperforms the existing constructive heuristics for the problem, providing solutions almost in real-time. Finally, for the cases where extremely high-quality solutions are required, a variable local search algorithm is proposed. The computational experience carried out shows that the algorithm outperforms the best existing metaheuristic for the problem. As a summary, the heuristics presented in the paper substantially modify the state-of-the-art of the approximate methods for the 2-stage assembly scheduling problem with total completion time objective.     

Two-agent two-machine flowshop scheduling with learning effects to minimize the total completion time

We study a two-agent scheduling problem in a two-machine permutation flowshop with learning effects. The objective is to minimize the total completion time of the jobs from one agent, given that the maximum tardiness of the jobs from the other agent cannot exceed a bound. We provide a branch-and-bound algorithm for the problem. In addition, we present several genetic algorithms to obtain near-optimal solutions. Computational results indicate that the algorithms perform well in either solving the problem or efficiently generating near-optimal solutions.     

Approximation algorithms for multi-agent scheduling to minimize total weighted completion time

We consider a multi-agent scheduling problem on a single machine in which each agent is responsible for his own set of jobs and wishes to minimize the total weighted completion time of his own set of jobs. It is known that the unweighted problem with two agents is NP-hard in the ordinary sense. For this case, we can reduce our problem to a Multi-Objective Shortest-Path (MOSP) problem and this reduction leads to several results including Fully Polynomial Time Approximation Schemes (FPTAS). We also provide an efficient approximation algorithm with a reasonably good worst-case ratio.     

Genetic algorithm for minimizing the total weighted completion time scheduling problem with learning and release times

This paper considers a single-machine problem with the sum-of-processing time based learning effect and release times. The objective is to minimize the total weighted completion times. First, a branch-and-bound algorithm incorporating with several dominance properties and two lower bounds are developed for the optimal solution. Then a genetic heuristic-based algorithm is proposed for a near-optimal solution. Finally, a computational experiment is conducted to evaluate the performances of the proposed algorithms. The results show that the branch-and-bound algorithm can solve instances up to 15 jobs, and the average error percentage of the genetic heuristic algorithm is less than 0.105%.     

Minimizing the total weighted completion time in the relocation problem

This paper studies the minimization of total weighted completion time in the relocation problem on a single machine. The relocation problem, formulated from an area redevelopment project, can be treated as a resource-constrained scheduling problem. In this paper, we show four special cases to be NP-hard in the strong sense. Problem equivalence between the unit-weighted case and the UET (unit-execution-time) case is established. For two further restricted special cases, we present a polynomial time approximation algorithm and show its performance ratio to be 2.