关键链法解决资源约束下的项目流程问题

在资源受限条件下项目资源配置方面,尽管国内外许多研究人员已经研究产生了不少成熟的方法和理论,但大都是在活动分配的资源数量和活动持续时间固定的情况下,优化所有项目活动的进度安排以实现项目整体工期的优化。文章基于关键链思想,将资源作为决策变量,给出了具体的模型和算法。     

关键链法解决资源约束下的项目流程问题

在资源受限条件下项目资源配置方面,尽管国内外许多研究人员已经研究产生了不少成熟的方法和理论,但大都是在活动分配的资源数量和活动持续时间固定的情况下,优化所有项目活动的进度安排以实现项目整体工期的优化.文章基于关键链思想,将资源作为决策变量,给出了具体的模型和算法.     

基于关键链的项目进度管理研究

1997年,以色列物理学家Goldratt出版了《关键链》一书,将约束理论(TOC)应用于项目管理,提出了关键链的基本思路和方法,提出用"关键链"取代传统的"关键路径",实现了项目管理理念与方法的重大突破。基于此,首先简要介绍约束理论和关键链技术的基本原理,然后利用启发式算法进行实例分析,最后提出了应用关键链技术的对策和建议。     

关键链技术在RCPSP问题中的应用研究

本文采用遗传算法，提出了一种关键链的识别方法，能够得到一近优的关键链。在项目缓冲的设置方面，既考虑了关键链自身的因素，又考虑了非关键链对其的影响。通过对资源受限项目调度问题（RCPSP）的标准问题库PSPLIB中典型案例的求解，较为详尽地描述了方法的具体应用过程。最后，采用对比研究仿真验证的方法证实了上述方法的有效性。     

基于遗传算法的大规模定制供应链调度优化研究

大规模定制(MC)模式下的供应链调度优化过程,是典型的随机需求与资源约束的动态问题。为合理解决这一问题,在前期研究成果基础上,提出了包括供应商选择及企业合作时序安排的优化调度模型,并提出了针对这种模型的求解思路,设计了基于遗传算法的求解过程;通过多组数据实验及结果比较分析,对模型算法的有效性、稳定性进行了验证。     

基于Petri网关键链技术研究

关键链方法秉承约束理论的思维流程,在制订项目计划时兼顾作业间的工艺逻辑约束和资源约束关系来确定关键链,通过缓冲来应对不确定因素。但现有的关键链理论大多都是确定型网络中研究,Petri网具有类似流程图等的可视描述及通过标识的流动模拟系统的动态行为功能,本文介绍了在Petri网下的项目关键链的判断方法,为了让关键链方法能更好地应对复杂多变的现实环境,它对于完善关键链理论有很重要的理论意义。     

基于关键链的物流项目进度管理研究

关键链技术是以色列科学家Goldratt的约束理论TOC在项目管理上的运用结果,有效克服了CPM在项目进度管理上存在的缺陷。文章以"物流设备"这一普遍性的资源约束为例,应用关键链技术进行项目任务的优化,实现对物流项目进度的有效控制。     

多模式资源约束的项目调度问题优化遗传算法的研究

资源约束的项目调度问题属于应用比较广泛的一类问题。文章研究的课题是基于多模式的资源约束项目调度问题,它属于NP—Hard问题,并文章对多模式资源约束项目调度问题进行了理论研究,并在此基础上设计实现了求解该类问题的遗传算法。实验表明,此方法具有较好的优化效果。     

浅谈关键链技术在电厂大修进度管理中的应用

关键链技术是项目进度管理中的约束理论在实际应用上的延伸,其在项目进度管理中的重点是管理项目缓冲中的瓶颈,把有限资源作为影响工程进度的首要因素进行处理.本文以项目进度关键链中的缓冲区管理为研究对象,针对电厂大修进度管理模式提出了将网络计划技术与关键链理论相结合,设计出基于关键链的缓冲机制,大大改善电厂检修进度的管理模式.     

基于动态约束的炼钢连铸重调度算法设计

针对炼钢连铸过程中出现的新炉次插入的重调度问题,考虑实际生产中的工艺约束,以最小化开工时间差异度、加工机器差异度的加权和为目标函数建立动态调度模型,采用回溯算法与启发式规则结合的算法。用Matlab7.8.0软件对选取的算例进行仿真,结果表明,此算法能保证重调度结果的实时性和有效性。     

资源约束项目中关键集和关键云新概念及其识别算法

现代项目十分复杂,项目进度计划不仅要考虑技术约束,而且要考虑资源约束。项目进度管理者需要识别制约进度的关键因素。现有关键工作概念及其识别方法虽然适用无资源约束项目,但并不完全适用资源约束项目,尤其不适用可重复使用资源量超过一个单位的项目。为了克服已有方法和概念的缺陷,本文详细介绍了R ivera和Duran于2003年提出的关键集和关键云新概念以及关键集和关键云识别算法,并且举例进行了说明。     

A dynamic programming approach to work force scheduling with time-dependent performance measures

An implicit enumeration algorithm is defined to obtain solutions to the commercial bank check processing encoder scheduling problem. The specific application is of particular interest because a significant factor in determining optimality is the float costs associated with checks which are unprocessed and unavailable for presentation at check clearing deadlines, thereby making the timing of the activity of crucial importance. A one day time horizon is employed to reflect those situations where banks have the scheduling flexibility afforded by part-time and/or temporary help in additon to a complement of full-time operators. Comparisons are made with other suggested approaches to daily encoder scheduling. Results indicate that dynamic programming can be an attractive methodology to attack this complex problem.     

A formal set of algorithms for project scheduling with critical path scheduling/material requirements planning

A hybrid model combining the critical path method (CPM) with material requirements planning (MRP) has been suggested (Aquilano) as a more robust method for scheduling projects and resources. The primary advantage of this technique is that resource acquisition lead times as well as inventory records are integrated into the process of computing the project schedule. This paper presents a set of formal CPM/MRP algorithms that may be used to compute the early and late start schedules as well as the critical sequence. A number of modifications have been incorporated into the CPM/MRP technique to improve the viability of CPM/MRP as a tool for application to actual project scheduling problems. A simple example project is used to demonstrate the CPM/MRP model.The CPM/MRP technique is designed to overcome a basic shortcoming of previously suggested project scheduling methodologies. CPM was initially designed to schedule projects subject to technological constraints only. Later, additional techniques were introduced to consider constraints upon various aspects of resource availability (Davis). None of the suggested techniques attempted to integrate resource acquisition lead time with the generation of requirements for resources. Obviously such a technique would require the integration of inventory records into the scheduling technique.The combination of CPM and MRP provides a possible vehicle for overcoming this drawback in CPM. Both CPM and MRP are linear models that generate schedules based upon precedence relationships. An integrated approach is useful since activities could be scheduled subject to information about the inventory position. An activity may be scheduled as soon as all resources are on hand. It is only delayed by those resources which must be acquired and activities which proceed it in the project network.CPM/MRP also shows promise as an aid to constrained resource scheduling since computations regarding resource availability are an integrated part of the technique. The effect of resource allocation decisions is immediately evident in the MRP-type time phased records.Results of the tests run on short projects of up to 300 activities and resources have shown that the program does work satisfactorily. Execution time for a 300 item network tested was approximately ten seconds on a CYBER 175.     

项目管理中资源配置的新思路

本文介绍了目前项目管理中的资源配置现状,指出了资源约束下的进度安排工作中存在的问题和资源平衡中存在的问题,分析了问题的原因。最后针对每一种存在的问题,提出了解决的新思路。     

Production scheduling with capacity-constrained transportation activities

This article presents a model for scheduling activities that are required to manufacture a product batch in a multistage process. The activities include setups, operations, and load movements between operations. In this model, setups may or may not require a unit from the preceding operation; each operation must be performed continuously on the batch once it has started, and capacity constraints apply to transportation activities. Within this context, two productivity-related objectives are sought. The primary objective is to minimize the total production time for the batch; the secondary is to minimize the number of load movements.Considering the capacity constraints, a maximum number of units per load is specified for each “vehicle” and one vehicle is dedicated to each transportation activity. The simplicity of the vehicle restriction facilitates the examination of scheduling interactions among activities, and the results of the research into this model may serve as a foundation for treating more general representations of capacity constraints.The model is used to investigate the scheduling implications of capacity-constrained load movements. It brings into focus interactions between these movements and the other activities in the process. After each operation, units must be grouped and moved in the fewest loads that permit the succeeding operation to begin as soon as possible, while observing setup and continuity requirements for this operation. Further, the departure times of loads depend on the availability of units and the vehicle. The formation of loads that must conform with the vehicle's capacity limit affects the times at which the loads are ready for movement, while the scheduling of previous movements from the operation affects the times at which the vehicle is available.A procedure is developed for scheduling activities that have this complex set of interactions. Computational requirements on test problems indicate that practical-sized applications can be handled with this procedure. These applications would be designed to assist in making production planning decisions by experimenting with factors such as vehicle capacity limits and sequencing of operations to determine their effect on production time requirements and numbers of load movements.The article develops a branch-and-bound routine to solve subproblems of scheduling transportation activities. The efficiency of this routine that results from exploiting the specific structure of the subproblems is critical for the success of the overall procedure. While the subproblems can be solved as zero-one mixed-integer programs, this approach is too computationally burdensome for all but the smallest of problems.     

易腐农产品的动态车辆调度问题研究

文章依据易腐农产品固有的自然属性、储存时间的有限性、运输装备的特殊性,以车辆固定成本、运输成本、能耗成本、货损成本以及客户惩罚成本构成的综合成本最低为目标函数。在满足车辆载重量约束、客户时间窗约束等限制条件下,针对客户需求的不断变化,在冷链物流配送的基础上建立动态车辆调度优化模型。利用基本动态规划算法对模型进行求解,验证了模型的有效性。     

供应链排序问题模式研究

供应链协同是供应链管理中的重要问题,供应链上不同阶段的决策者应当如何安排产品的生产、配送顺序,近年来有研究将经典生产排序理论引入供应链管理中,针对上述协同问题提出供应链排序研究模型,但还没有形成统一的框架和定义,本文将介绍这一领域的研究现状和发展前景.     

Constrained resource project scheduling subject to material constraints

Constrained resource project scheduling techniques schedule project activities subject to finite constraints on the availability of non-storable resources such as labor and equipment without consideration of constraints resulting from material requirements. Projects are frequently delayed and resources are wasted when project activities are delayed due to material shortages. A heuristic procedure is presented here for scheduling large projects subject to the availability of all necessary resources, including materials, manufactured components, facilities, equipment and labor as well as the acquisition lead times required by these resources. Results are listed for tests involving both benchmark and actual problems.     

Multiproject scheduling: Analysis of scheduling strategies under unequal delay penalties

The multiproject scheduling problem is investigated under the assumption that delays corresponding to different projects carry different penalties. Five penalty functions are introduced that simulate typical business behavior. These are: 1) assigning the highest penalty to the project requiring the greatest amount of resources; 2) assigning the highest priority to the longest project; 3) assigning the highest priority to the project requiring the least amount of resources; 4) assigning the highest priority to the shortest project; and 5) random assignment. Justification for each case is provided.Two powerful project summary measures were used to generate the test problems. The first measure, average resource load factor (ARLF), identifies whether the location of the peak requirement of all (i.e., combined) resources is in the first or second half of the project's critical path. If each resource is expressed in terms of dollars, then ARLF identifies the location of the peak cash requirement. Since in practice the choice of the scheduling strategy is influenced by the location of the peak cash requirement, performance of the scheduling strategies is analyzed with respect to values of this measure. The second measure, average utilization factor (AUF), calculates the ratio of resource requirements to availabilities. It is shown that problems tested must have different AUF values in order to be classified different for purposes of experimental design. Thus a factorial model of the form, y = Strategy + Penalty + ARLF + AUF + ? was used to generate 385 problems, each requiring 2 to 4 resources, containing 3 to 5 projects and 34 to 63 activities.The computer program used in the study is based on a parallel method of scheduling in which priorities of the activities are determined when the activity is considered for scheduling. Ten scheduling strategies are tested. Some important ones are: 1) to schedule the shortest activity first; 2) to schedule the activity with minimum slack first; 3) to schedule the activity with maximum work content first (i.e., from the project with highest work content); 4) to schedule the shortest activity from the shortest project first; and 5) to schedule the activity with maximum penalty first. Shortest activity first and minimum slack first are popular strategies introduced by other researchers.Using number of times ranked first as our criterion, scheduling the activity with maximum penalty first provides the best results followed by the strategy of scheduling the activity with maximum work content. But when these results are analyzed with respect to existence of a very expensive project (i.e., dominance) in the problem, performance of the maximum penalty strategy improves. When the overall results are analyzed with respect to values of ARLF, a different picture emerges. Then the strategy of scheduling the activity with the highest penalty first provides the best results if the peak requirement is early. When the peak requirement is toward the middle of a project's unconstrained critical path, scheduling the activity with the highest work content provides the best results. When the peak requirement is late in a project's life, scheduling the shortest activity from the shortest project is the best strategy to adopt. These findings were tested for statistical significance by using nonparametric testing procedures and were found to be significant.