基于开工柔韧性的关键链项目缓冲分配方法

Project Buffer Allocation Method Based on Activity Flexibility

缓冲应该进行集中式还是分散式管理是项目缓冲管理的一个核心问题,经典缓冲管理方法没有对此进行研究。基于此,本文在考虑开工柔韧性的情况下,研究并比较分析了两种项目缓冲的分配模式。通过对两种缓冲管理模型的研究,结合MATLAB仿真结果发现,缓冲集中式管理模式在考虑开工柔韧性的情况下,主要通过活动资源提前就位来抓住项目活动可能出现的提前完工机会,即通过可能的成本增加来换取可能的工期降低。仿真结果显示,在这种模式下,项目工期提前了8.67%,而总成本只上升了2.02%(主要是因为增加了资源库存成本和计划变动成本),由此可见,集中式缓冲管理模式可以有效降低工期。而缓冲分散式管理模式则是现有缓冲管理方法的延伸,在考虑开工柔韧性的情况下,将项目计划做出不同程度延缓,相较于缓冲集中式管理没有了库存成本的增加,实验结果表明,当活动完工率落在概率分布函数的50%~60%之间时可得到项目的最佳缓冲分散程度。

Whether project buffer should be centralized or decentralized regarding project characteristic isa core issue of project buffer management.Classic buffer management researchtries to get more optimized results by increasing the monitoring frequency or monitoring difficulty of the project,while ignores research on whether the project buffer should be centralized at the end of the project or distributed at the end of each activity.The existing buffer monitoring methods mainly focus on the centralized buffer management,that is,the buffer is centralized in the tail and then monitored.In addition,the activity flexibility reflects the ability of a project activity to start in time after the completion of its pre activity.Previous studies usually use percentage to describe this ability.However,this description is often difficult to be quantified.For example,for a 10 day activity,its flexibility to start is 50%.In the actual project planning and monitoring process,this flexibility to start expressed in probability is not easy to be operated.The proposed method therefore studies and compares these two buffer allocation models considering the activity flexibility,and discusses the conditions that need to be met for 100%starting flexibility.The simulation results demonstrate that the centralized buffer management can better grasp the possible early completion opportunities of the project activities by making the resources in place ahead of time.It indicates that the project duration is reduced by 8.67%,while the total cost is only increased by 2.02%,implying that the centralized model can effectively reduce the project duration.However,the decentralized buffer management model is an extension of existing buffer management research.For this model,the inventory cost does not increase compared with the centralized model,considering the flexibility of the project.The experimental results show that the project can obtains the optimal buffer dispersion degree of the project when the activity completion rate falls between 50%and 60%of the probability distribution function.For the first time,this paper combines resource planning with the flexibility of project activities,redefines the concept of flexibility of project activities and makes a quantitative study on it.