A novel methodology for optimal single mobile robot scheduling using whale optimization algorithm

One of the fundamental requirements for creating an intelligent manufacturing environment is to develop a reliable, efficient and optimally scheduled material transport system. Besides traditional material transport solutions based on conveyor belts, industrial trucks, or automated guided vehicles, nowadays intelligent mobile robots are becoming widely used to satisfy this requirement. In this paper, the authors analyze a single mobile robot scheduling problem in order to find an optimal way to transport raw materials, goods, and parts within an intelligent manufacturing system. The proposed methodology is based on biologically inspired Whale Optimization Algorithm (WOA) and is aimed to find the optimal solution of the nondeterministic polynomial-hard (NP-hard) scheduling problem. The authors propose a novel mathematical model for the problem and give a mathematical formulation for minimization of seven fitness functions (makespan, robot finishing time, transport time, balanced level of robot utilization, robot waiting time, job waiting time, as well as total robot and job waiting time). This newly developed methodology is extensively experimentally tested on 26 benchmark problems through three experimental studies and compared to five meta-heuristic algorithms including genetic algorithm (GA), simulated annealing (SA), generic and chaotic Particle Swarm Optimization algorithm (PSO and cPSO), and hybrid GA–SA algorithm. Furthermore, the data are analyzed by using the Friedman statistical test to prove that results are statistically significant. Finally, generated scheduling plans are tested by Khepera II mobile robot within a laboratory model of the manufacturing environment. The experimental results show that the proposed methodology provides very competitive results compared to the state-of-art optimization algorithms.     

带时限的多出救点应急物资调度模型及算法

主要研究时间限制下的多出救点应急资源调度优化问题。针对传统优化算法搜索速度慢、易陷入局部最优解的缺点,提出一种新的基于高斯函数的混沌粒子群优化算法,该算法利用高斯函数的分布曲线特性和混沌的遍历性来增强粒子群优化算法的寻优能力。将该算法应用时间限制下的多出救点应急资源调度优化,建立了满足应急时间限制下系统总费用最小的数学模型,介绍了该算法的详细实现过程。算例通过和遗传算法和标准粒子群算法进行比较,证明了其搜索速度和寻优能力的优越性。     

A bi-objective genetic algorithm for intelligent rehabilitation scheduling considering therapy precedence constraints

The rehabilitation inpatients in hospitals often complain about the service quality due to the long waiting time between the therapeutic processes. To enhance service quality, this study aims to propose an intelligent solution to reduce the waiting time through solving the rehabilitation scheduling problem. In particular, a bi-objective genetic algorithm is developed for rehabilitation scheduling via minimizing the total waiting time and the makespan. The conjunctive therapy concept is employed to preserve the partial precedence constraints between the therapies and thus the present rehabilitation scheduling problem can be formulated as an open shop scheduling problem, in which a special decoding algorithm is designed. We conducted an empirical study based on real data collected in a general hospital for validation. The proposed approach considered both the hospital operational efficiency and the patient centralized service needs. The results have shown that the waiting time of each inpatient can be reduced significantly and thus demonstrated the practical viability of the proposed bi-objective heuristic genetic algorithm.     

基于离散人工蜂群算法的云任务调度优化

针对现今云计算任务调度只考虑单目标和云计算应用对虚拟资源的服务的质量要求高等问题,综合考虑了用户最短等待时间、资源负载均衡和经济原则,提出一种离散人工蜂群(ABC)算法的云任务调度优化策略。首先,从理论上建立了云任务调度的多目标数学模型;然后,结合偏好满意度策略并引入局部搜索算子和改变侦察蜂搜索方式,提出多目标离散型人工蜂群(MDABC)算法的优化策略。通过不同的云任务调度仿真实验,显示了改进离散人工蜂群算法相对于基础离散人工蜂群算法、遗传算法以及经典贪心算法,能够得到较高的综合满意度,表明了改进离散人工蜂群算法能够更好地改善虚拟资源中云任务调度系统的性能,具有一定的普适性。     

基于滚动变时间窗的重组批处理机调度研究

针对具有等待时间限制和工件动态到达的重组批处理机调度问题,以拖延时间和最小为目标,提出基于滚动变时间窗的三层混合调度算法。该调度算法是应用滚动时域策略,将重组批处理机调度问题分解为许多变时间窗的子问题;每个子问题调度分三层执行：即产生触发并传递参数、重组批及排序、派工并更新参数。通过实时调度仿真平台和CPLEX平台进行实例验证,结果表明基于滚动变时间窗的三层混合调度算法能够在较短计算时间内获得满意优化解。     

冷链物流越库调度的拉格朗日松弛算法

为了提高冷链物流的运输效率,解决越库在冷链物流中的应用问题,提出了基于拉格朗日松弛算法的冷链物流的越库调度方法.首先进行了问题域的描述并做出了具体假设,基于问题域以最小化卡车等待时间和越库内部运输成本为目标,建立越库调度的整数规划数学模型.然后,提出了针对越库调度模型的拉格朗日松弛算法,松弛复杂约束后根据决策变量将松弛问题分解为若干子问题,采用次梯度算法求解松弛模型.最后,对各种不同规模的越库模型进行仿真实验,并与传统的贪婪算法进行对比,结果表明,所提出的调度算法适用于问题的求解,并可以在较短时间内获得良好的近优解.     

改进的差分进化算法求解炼钢-连铸动态调度问题

为了求解炼钢-连铸动态调度问题,提出了一种将拉格朗日插值算法与差分进化算法相融合得到的改进的差分进化算法。改进后的差分进化算法通过自适应调整进化参数,动态的调整差分进化的方向,并结合拉格朗日插值来优化差分进化算法的局部搜索能力,引入权重系数对全局搜索和局部搜索加以平衡。针对国内某大型钢厂的实际生产数据建立实验模型,以最小化总完工时间、最小化总断浇时间、最小化炉次间总等待时间和最小化总偏差量时间为目标,将改进的差分进化算法应用于求解炼钢-连铸转炉出现故障的动态扰动事件调度问题,实验结果表明,改进的差分进化算法应用在炼钢-连铸动态调度问题上,有效的缩短了炉次加工总完工时间、炉次间总等待时间和总断浇时间,在合理范围内,有效控制了新生产的调度计划与原始调度计划的时间偏差量,避免了因扰动事件的发生而引起连铸机断浇。     

A two-stage heuristic approach for nurse scheduling problem: A case study in an emergency department

Nurse scheduling is a critical issue in the management of emergency department. Under the intense work environment, it is imperative to make quality nurse schedules in a most cost and time effective way. To this end, a spreadsheet-based two-stage heuristic approach is proposed for the nurse scheduling problem (NSP) in a local emergency department. First, an initial schedule satisfying all hard constraints is generated by the simple shift assignment heuristic. Second, the sequential local search algorithm is employed to improve the initial schedules by taking soft constraints (nurse preferences) into account. The proposed approach is benchmarked with the existing approach and 0–1 programming. The contribution of this paper is twofold. First, it is one of a few studies in nurse scheduling literature using heuristic approach to generate nurse schedules based on Excel spreadsheet. Therefore, users with little knowledge on linear programming and computer sciences can operate and change the scheduling algorithms easily. Second, while most studies on nurse scheduling are situated in hospitals, this paper attempts to bridge the research gap by investigating the NSP in the emergency department where the scheduling rules are much more restrictive due to the intense and dynamic work environment. Overall, our approach generates satisfactory schedules with higher level of user-friendliness, efficiency, and flexibility of rescheduling as compared to both the existing approach and 0–1 programming.     

Design of a genetic algorithm for bi-objective unrelated parallel machines scheduling with sequence-dependent setup times and precedence constraints

This paper presents a novel, two-level mixed-integer programming model of scheduling N jobs on M parallel machines that minimizes bi-objectives, namely the number of tardy jobs and the total completion time of all the jobs. The proposed model considers unrelated parallel machines. The jobs have non-identical due dates and ready times, and there are some precedence relations between them. Furthermore, sequence-dependent setup times, which are included in the proposed model, may be different for each machine depending on their characteristics. Obtaining an optimal solution for this type of complex, large-sized problem in reasonable computational time using traditional approaches or optimization tools is extremely difficult. This paper proposes an efficient genetic algorithm (GA) to solve the bi-objective parallel machine scheduling problem. The performance of the presented model and the proposed GA is verified by a number of numerical experiments. The related results show the effectiveness of the proposed model and GA for small and large-sized problems.     

干扰约束下考虑分组作业面的岸桥AGV联合调度

为解决自动化码头海侧多阶段设备作业的协调问题,加快集装箱在码头内部的周转过程。考虑干扰约束下分组作业面的的岸桥自动导引小车（AGV）联合调度问题。以岸桥、AGV完工时间和AGV等待时间加权总和最小为目标,考虑岸桥实际操作中的干扰约束与AGV堵塞等待等情况,建立岸桥与AGV联合调度优化模型。提出岸桥动态调度与AGV分组作业面调度模式,设计不同规模的算例,并采用遗传算法（GA）进行求解,将计算结果与传统调度模式进行对比。结果表明,该算法能有效提高岸桥与AGV作业效率,降低AGV的等待时间与堵塞次数,为码头实际作业提供依据。     

异构系统中一种基于可用性的抢占式任务调度算法*

针对大多数现有的异构系统调度算法没有考虑由多类任务特别是抢占式任务所引起的可用性需求的不足,在现有基于可用性的非抢占式任务调度算法的基础上,通过计算任务的平均等待时间来确定优先级等级,对异构系统中多类抢占式任务的可用性约束的调度问题进行了探索,提出了一种基于可用性的抢占式优先调度算法P-SSAC。该算法在不增加硬件代价的前提条件下通过调度增加了系统的可用性,缩短了任务的平均等待时间,同时该算法可对抢占式的任务进行有效调度。仿真实验结果表明,该算法有效实现了异构系统可用性和任务等待时间之间的折中。     

A hybrid meta-heuristic algorithm for optimization of crew scheduling

Crew scheduling problem is the problem of assigning crew members to the flights so that total cost is minimized while regulatory and legal restrictions are satisfied. The crew scheduling is an NP-hard constrained combinatorial optimization problem and hence, it cannot be exactly solved in a reasonable computational time. This paper presents a particle swarm optimization (PSO) algorithm synchronized with a local search heuristic for solving the crew scheduling problem. Recent studies use genetic algorithm (GA) or ant colony optimization (ACO) to solve large scale crew scheduling problems. Furthermore, two other hybrid algorithms based on GA and ACO algorithms have been developed to solve the problem. Computational results show the effectiveness and superiority of the proposed hybrid PSO algorithm over other algorithms.     

多约束条件下生产排程智能优化技术

针对当前企业智能化生产中,多条工艺路线共享工序以及工单在生产过程中具有多个约束条件(如工期、优先级、产量等)的问题,提出了一种以“等待时间最短”为主的生产排程智能优化算法。综合考虑工单优先级、工期长短和紧急任务插单等因素,通过一种递归算法来计算工单等待时间,以最小化工单完成时间、最大化资源利用率为优化目标,建立了多约束条件下紧急工单处理的快速响应机制。在服装加工企业中的实际应用表明,相比手工排程及其他传统算法,文中提出的优化排程算法不仅缩短了生产周期,力求各工序的负荷率最大化,使企业的生产效率提高了20%及以上,同时还改善了排程系统的稳定性。     

Integrated production and delivery with single machine and multiple vehicles

This paper considers a class of multi-objective production–distribution scheduling problem with a single machine and multiple vehicles. The objective is to minimize the vehicle delivery cost and the total customer waiting time. It is assumed that the manufacturer’s production department has a single machine to process orders. The distribution department has multiple vehicles to deliver multiple orders to multiple customers after the orders have been processed. Since each delivery involves multiple customers, it involves a vehicle routing problem. Most previous research work attempts at tackling this problem focus on single-objective optimization system. This paper builds a multi-objective mathematical model for the problem. Through deep analysis, this paper proposes that for each non-dominated solution in the Pareto solution set, the orders in the same delivery batch are processed contiguously and their processing order is immaterial. Thus we can view the orders in the same delivery batch as a block. The blocks should be processed in ascending order of the values of their average workload. All the analysis results are embedded into a non-dominated genetic algorithm with the elite strategy (PD-NSGA-II). The performance of the algorithm is tested through random data. It is shown that the proposed algorithm can offer high-quality solutions in reasonable time.     

基于TSP方法求解等待时间受限的置换流水车间调度

等待时间受限的置换流水车间调度问题要求工件在连续两个机器间的等待时间满足上限值约束.对此,分析了工件序列中相邻工件的加工持续时间及其上下界关系,并且提出一种启发式方法.首先,建立旅行商间题（TSP）以生成初始调度;然后,采用扩展插入方法优化调度解.为了衡量算法性能,给出问题下界的计算方法和相关评价指标,并通过数据实验验证了该启发式和下界计算方法的可行性和有效性.     

Flexible job shop scheduling with parallel machines using Genetic Algorithm and Grouping Genetic Algorithm

Based on Genetic Algorithm (GA) and Grouping Genetic Algorithm (GGA), this research develops a scheduling algorithm for job shop scheduling problem with parallel machines and reentrant process. This algorithm consists of two major modules: machine selection module (MSM) and operation scheduling module (OSM). MSM helps an operation to select one of the parallel machines to process it. OSM is then used to arrange the sequences of all operations assigned to each machine. A real weapon production factory is used as a case study to evaluate the performance of the proposed algorithm. Due to the high penalty of late delivery in military orders and high cost of equipment investment, total tardiness, total machine idle time and makespan are important performance measures used in this study. Based on the design of experiments, the parameters setting for GA and GGA are identified. Simulation results demonstrate that MSM and OSM respectively using GGA and GA outperform current methods used in practice.     

A new encoding scheme-based hybrid algorithm for minimising two-machine flow-shop group scheduling problem

This article investigates the two-machine flow-shop group scheduling problem (GSP) with sequence-dependent setup and removal times, and job transportation times between machines. The objective is to minimise the total completion time. As known, this problem is an NP-hard problem and generalises the typical two-machine GSPs. In this article, a new encoding scheme based on permutation representation is proposed to transform a random job permutation to a feasible permutation for GSPs. The proposed encoding scheme simultaneously determines both the sequence of jobs in each group and the sequence of groups. By reasonably combining particle swarm optimisation (PSO) and genetic algorithm (GA), we develop a fast and easily implemented hybrid algorithm (HA) for solving the considered problems. The effectiveness and efficiency of the proposed HA are demonstrated and compared with those of standard PSO and GA by numerical results of various tested instances with group numbers up to 20. In addition, three different lower bounds are developed to evaluate the solution quality of the HA. Limited numerical results indicate that the proposed HA is a viable and effective approach for the studied two-machine flow-shop group scheduling problem.     

No-wait two stage hybrid flow shop scheduling with genetic and adaptive imperialist competitive algorithms

This article studies a no-wait two-stage flexible flow shop scheduling problem with setup times aiming to minimize the total completion time. The problem is solved using an adaptive imperialist competitive algorithm (AICA) and genetic algorithm (GA). To test the performance of the proposed AICA and GA, the algorithms are compared with ant colony optimisation, known as an effective algorithm in the literature. The performance of the algorithms are evaluated by solving both small and large-scale problems. Their performance is evaluated in terms of relative percentage deviation. Finally the results of the study are discussed and conclusions and potential areas for further study are highlighted.     

Evolutionary algorithms for scheduling m-machine flow shop with lot streaming

This paper addresses the problem of making sequencing and scheduling decisions for n jobs–m-machines flow shops under lot sizing environment. Lot streaming (Lot sizing) is the process of creating sub lots to move the completed portion of a production sub lots to down stream machines. There is a scope for efficient algorithms for scheduling problems in m-machine flow shop with lot streaming. In recent years, much attention is given to heuristics and search techniques. Evolutionary algorithms that belong to search heuristics find more applications in recent research. Genetic algorithm (GA) and hybrid genetic algorithm (HEA) also known as hybrid evolutionary algorithm fall under evolutionary heuristics. On this concern this paper proposes two evolutionary algorithms namely, GA and HEA to evolve best sequence for makespan/total flow time criterion for m-machine flow shop involved with lot streaming and set-up time. The following two algorithms are used to evaluate the performance of the proposed GA and HEA: (i) Baker's algorithm (BA), an optimal solution procedure for two-machine flow shop problem with lot streaming and makespan objective criterion and (ii) simulated annealing algorithm (SA) for m-machine flow shop problem with lot streaming and makespan and total flow time criteria.     

考虑患者分类的应急手术调度研究

针对公众突发事件背景下应急手术调度效率及救治率低下等问题,将应急手术调度问题看作三级混合流水车间调度问题,在考虑患者三级分类的同时,综合考虑患者的恶化效应与手术团队的学习效应因素,构建以平均完成手术时间、患者恶化成本和手术室总能耗为优化目标的多目标应急手术调度模型。针对布谷鸟算法易陷入局部寻优的缺点,设计了一种被发现概率自适应的布谷鸟算法对应急手术的调度模型进行求解。最后通过仿真实验验证了模型和算法的有效性。