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1、原文：The role of system dynamics in project managementJohn Bowers，Alexandre Rodrigues.International Journal of Project Management，1996，14(4)：213-220IntroductionWhereas the traditional project management tools provide useful support, their underlying models often seem to bear little relation to actual

2、projects. The traditional approaches tend to assume that if each element of the project can be understood then the whole project may be controlled. However, experience suggests that the interrelationships between the projects components are more complex than is suggested by the traditional work brea

3、kdown structure of project network. An alternative view of the project is offered by system dynamics which concentrates on the whole project. The approach emphasises the interrelationships that may be responsible for unexpected overrun and overspend. System dynamics has been applied in a number of p

4、rojects in diverse industries, providing a basis for a comparison with the traditional approaches. It offers valuable strategic lessons for project management and should be seen as complementary to the detailed operational support supplied by the traditional techniques. This paper contrasts the char

5、acteristics of the two approaches and provides an overview of various areas of application of system dynamics in project management. It highlights the distinctive contribution that system dynamics can make to project management, while emphasising that the more traditional techniques still have a vit

6、al role. Copyright 1996 Elsevier Science Ltd and IPMA.A new approach to modelling and understanding projects is emerging, based on system dynamics. System dynamics assumes a holistic view of the organisation focusing on the behavioural trends of projects and their relation with managerial strategies

7、. The approach contrasts with traditional methods, which rely on detailed models of the components of a project with the main object of providing tactical advice about the resourcing and scheduling of activities. There has been a tendency to produce ever more sophisticated network-based tools, in th

8、e belief that by incorporating more detail a more accurate model will be developed and a greater understanding will be the inevitable result. However, it has also been suggested t2 that concentrating on the detail ignores many of the major, but not readily quantified, influences that cause project f

9、ailure, and that a new approach is needed taking a more systemic view. System dynamics provides the opportunity of such an alternative view, considering these major influences on a project and dispensing with much of the detail to ensure that the key behaviour of the project is not obscured. Typical

10、ly, system dynamic studies offer general conclusions about Author for correspondence. project behaviour but it is not always obvious how such advice might be incorporated into a daily project plan. The traditional approaches have many failings and it appears that system dynamics may offer a useful a

11、lternative, but is it of practical value to the project manager? This paper examines the applications of system dynamics to project management and its potential roles in comparison with the more traditional techniques of project analysis.Characteristics of the traditional approachesNumerous techniqu

12、es have been developed to help manage project schedules and costs. These techniques are founded on the premise that whereas a project may be unique, many of its constituent elements have been experienced before. The project work is therefore decomposed into elements, for example activities, which ca

13、n be individually related to previous experience. It is then possible to produce reasonable estimates of the duration, cost and resource requirements for each element. The logic of the project, such as represented in a network, supplies the basis for reconstructing the project from its elements and

14、calculating the duration, cost and resource requirements of the whole project from those of its elements. One of the concerns about such an approach is that, whereas the estimates for the individual elements may be very accurate, the reconstruction of the project may ignore important intra-project f

15、orces: the whole may be much greater than the sum of the parts.The traditional analyses of projects have been described as linear or as static and closed TM, suggesting an assumption of a strictly ordered project that progresses in well defined, predictable stages to completion. This includes an ass

16、umption that all the information is available at the start of the project, allowing the design of an optimal plan and the only concern of management is to keep the project on the specified track. However, in practice, management needs to be dynamic, responding to new information and adapting the pla

17、n rather than keeping rigidly to the original. When implemented properly, the traditional methods are used in a more responsive manner, deployed within the dynamic environment of the classical control feedback loop: the original plan is used to set targets which are then compared to progress and whe

18、re there is significant deviation, action is taken including revisions of the project plan. Whereas individual tools might be very linear in nature, the overall framework of traditional project control exhibits the classic characteristics of a dynamic system.The system dynamics approach System dynam

19、ics was introduced by Forrester 4 as a method for modelling and analysing the behaviour of complex social systems, particularly in an industrial context. It has been used to examine various social, economic and environmental systems 5, where a holistic view is important and feedback loops are critic

20、al to understanding the interrelationships. The approach has attracted particular attention in recent years since computer software has become readily available to help communicate the key dynamics of systems to the managers responsible. Having identified the key feedback loops and various disruptiv

21、e factors, quantitative estimate of the different effects are elicited, either from data describing past projects or in discussions with various project participants. A computer-based system dynamics simulation model may then be built, using software such as PowerSim (ModellData AS, Bergen, Norway)

22、or iThink (High Performance Systems Inc., Hanover, Hampshire, USA). The graphics of such models allow the effects of the feedback dynamics to be observed, leading to a greater understanding of the system and encouraging experiments to explore new management options.The application of system dynamics

23、 to project management has been motivated by various factors: a concern to consider the whole project rather than a sum of individual elements (the holistic approach), the need to examine major non-linear aspects typically described by balancing or reinforcing feedback loops, a need for a flexible p

24、roject model which offers a laboratory for experiments with managements options,and the failure of traditional analytic tools to solve all project management problems and the desire to experiment with something new.Applications in project managementThe system dynamics model of a project aims to capt

25、ure all the major feedback processes responsible for the system behaviour. The project management process is put into a wider context which includes many soft factors often external to the project work, with a strong focus on human factors which often appear to dominate the feedback structures. The

26、developments of system dynamics in project management are summarised in Table 1, which includes a representative sample of studies drawn from a more exhaustive review 6. The first description of the use of system dynamics in understanding projects appeared in 1964, but it was not until the 1980s tha

27、t the first project-specific applications began to be reported. Since 1990 there have been many more reported examples of the use of system dynamics in project management.Typically the application areas are those where budgets are high and the risks greater, such as aerospace, software developments

28、and recently the Channel Tunnel. The first models 78 were developed to examine the dynamics of research and development projects. The concepts of perceived progress and real progress were introduced, addressing explicitly the fact that managerial decisions are based on perceptions of the projects st

29、ate which may be quite different to the reality. Richardson and Pugh 9 dev- eloped the model of the R&D projects, and various studies investigated the new concepts of rework, undiscovered rework, perceived progress, real progress, perceived productivity and real productivity. The program management

30、modelling system, developed by Pugh-Roberts Associ- ates, incorporates many of these features and has been used to support the management of several large projects. Other studies have examined specialised application areas, such as those of Abdel-Hamid H6 in the management of software development pr

31、ojects.Comparing system dynamics and traditional approachesBoth the system dynamics and the traditional approaches examine the same basic issues in project management but from very different perspectives; a summary is provided by Table 1.Table 1 Comparison of the characteristics of the traditional a

32、nd system dynamics approachesAspectTraditional approachSystem dynamics approachFocusProject work and the problemFeedback processes and the situationLevel of detailConsiderable detail in some areas but ignores othersLittle detail but attempts to capture the whole projectFactors considered explicitlyT

33、he readily quantified and those related to project workThe subjective and those related to feedback processesKey factorThe logic of work and its resource requirementsHuman resources behaviourProject work modelA set of interrelated but distinct packagesA continuous flowNature of estimatePredictions a

34、ssuming success, reflecting a desired outcomeA simulation of reality, including human and system frailties, indicating likely outcomeIncorporating system dynamics and the traditional approachesA system dynamics analysis offers a distinctly different view of a project with the main output being a bet

35、ter understanding of the important underlying influences. As such, system dynamics appears to be complementary to the traditional techniques rather than a complete alternative. Various routes might be adopted to incorporating the two approaches: a more sophisticated network model including the feedb

36、ack processes and detailed mechanisms for modelling activity durations and costs to reflect the underlying influences; a more detailed system dynamics model distinguishing the major stages of a project as distinct activities and employing different types of project work; assimilating the main lesson

37、s from system dynamics studies in a set of rules for use in estimating activity durations, costs and uncertaintiesConclusions The traditional techniques are based on a detailed breakdown of the project into work packages and activities; this permits the construction of equally detailed schedules and

38、 budgets for the control of the project and provides the basis for operational decisions such as resource allocation and time-cost trade-offs. System dynamics offers a project model which appears to reflect the real experiences of projects which seldom follow the simple linear route suggested by the

39、 logic of the project network. System dynamics suggests that it is not the detail that determines the outcome of the project but the powerful underlying influences and the insidious feedback loops that can, if not managed properly, result in unexpected overrun and overspend. Whereas there are exampl

40、es of system dynamics being used in projects in a range of industries, it is still a relatively rare technique and tends to be employed within separate studies when a special concern arises in a project. The two ap- proaches provide valuable complementary information: the traditional techniques supp

41、ly the detailed output necessary for project control, whereas system dynamics offers useful general strategic lessons which should be considered when planning the project and producing the estimates for the traditional analyses. There should be benefits in formally incorporating the two models but i

42、t is vital that the clarity and fresh vision introduced by system dynamics is preserved.译文：出处：约翰鲍尔斯，亚历山大罗德里格斯系统动力学在工程管理中的作用J国际期刊项目管理，1996.14(4)：213-220 简介虽然传统的项目管理工具提供了有用的支持，但是他们的基本模型似乎往往没有关系到实际的项目。传统的方法往往假定，如果该项目中的每个元素可以被理解，那么整个项目就可以控制。然而，经验表明，项目元素之间的相互关系比传统的项目网络的工作分解结构更为复杂。该项目的另一个观点是运用系统动力学立足于整个项目

43、，这种方法强调了相互关系或许能够解释意外超时和超支。系统动力学已被应用于不同行业的项目中，提供了一个比较传统方法的依据。系统动力学为项目管理提供了宝贵的战略经验，应被视为是对传统技术所提供的详细操作支持的补充。本文对比了这两种方法的特征，并阐述了系统动力学应用于不同领域的项目管理。它突出表明，系统动力学对项目管理的独特贡献，同时，也强调了传统技术仍然占有十分重要的地位。一种基于系统动力学为工具来建模和解析项目的新方法正在兴起。系统动力学假设从整体视角出发，重点关注项目的行为趋势以及其各元素之间相互关系的管理策略。该方法与传统方法对比，它依赖于一个项目的组成部分的详细模型与与提供的主要目的的对比

44、有关活动的资源和调度的战术建议。目前已经有通过引入更详细、更准确的模型来产生更加复杂的、基于网络的工具，相信这种趋势将不断发展，这将有助于更为深入地了解项目。然而，也有人提出将重点集中在细节的话将会忽略主要的部分，而且不容易定量，这将会导致项目的失败，这种新方法需要采取更为系统的观点。系统动力学提供了机会这种替代视角，考虑在一个项目中的主要影响因素以及细节的分配问题，以确保该项目的关键行为没有被遮蔽。通常情况下，系统动力学研究提供关于项目行为的一般性的结论，但是这种建议并不总能被并入一个日常项目计划中。综上看来，传统的方法有许多缺点，而系统动力学可以作为了一种有用的选择，但是它对于项目经理来说

45、是否有实用价值呢？本文探讨了系统动力学在项目管理中的应用，以及它与传统项目分析技术对比所具有的潜在价值和作用。传统方法的特点目前，很多技术方法已经发展到可以帮助管理项目的进度和成本，而这些技术建立的前提是：这个项目是唯一的，它的许多组成元素是有经验的。因此，该项目的工作被分解成各个元素，例如与之前有关的活动可以单独进行，那么有可能会对各个元素产生的持续时间、成本和资源等需求进行合理的估计。项目逻辑，诸如在网络中所表示的逻辑，是为重组项目和计算整个项目的持续时间、成本和资源等需求提供基础。其中，对这种方法的一个关注点是：对于各个元素的估计可能是非常精确的，然而该项目的重组可能会忽略项目内部的重要

46、力量：项目整体和可能比部分的总和大得多。传统的项目分析方法被描述为直链或者“静态和封闭”，这表明项目是建立于进展在明确定义的、可预测的阶段到完成的假设基础上。这假设包括所有的信息在项目开始阶段都可获得，并设计出最佳的计划方案，那么管理上唯一需要关注的便是让该项目保持在预定的轨道上运行。然而，在实践中，管理是动态的，需要响应新信息并进行方案调整，而不是一味地保持项目按原定轨道运行。当落实得当时，传统方式是反应更为灵敏的方法，在经典的控制反馈回路的动态环境中进行部署：原计划用于设定目标，并与取得的成果与产生的偏差进行比较，采取包括修订项目计划的行动。而单独的工具在本质上可能是线性的，传统项目控制的

47、总体框架表现出动态系统的经典特征。系统动力学方法系统动力学是由福瑞斯特教授创建的,用以建模和分析复杂社会系统的行为,特别是应用在工业环境中。系统动力学已被应用于研究各种社会系统、经济系统和环境系统中，全局观是十分重要的，同时，反馈回路对于理解相互之间的关系也是至关重要的。近年来，由于计算机软件已经发展成为可随时随地帮助管理者传递系统关键动态信息，系统动力学方法已经引起了特别的重视。在确定了关键的反馈回路和各种破坏性因素的情况下，无论是从过去的记录项目的数据或是参与各项目讨论的资料，其产生的不同影响均可以被定量化估计出来。然后，可以使用像PowerSim、iThink等计算机软件建立系统动力学仿

48、真模型。我们可以通过这些模型来观察反馈动力学的影响，这样一方面能方便我们进一步了解整个系统，另一方面能激励我们尝试探索新的管理选项。系统动力学项目管理中的应用受到多种因素的影响：从全局考虑整个项目（整体法），而不是简单的认为项目是拆分的各个元素的总和；通过平衡或增强反馈回路来检查项目中主要非线性方面内容；需要建立一个灵活的项目模型，以此提供给管理者进行仿真模拟；传统的分析工具不能解决所有的项目管理问题，因而对新工具方法探索的欲望愈加强烈。 系统动力学在项目管理中的应用建立项目系统动力学模型的主要目的是为获取用以解释所有系统行为的主要反馈过程。项目管理是置于大背景环境下的管理活动，与很多因素相互

49、关联，其中包括许多常与项目工作外有关的软因素，对具有主导反馈结构的人为因素尤为关注。首次描述系统动力学在项目理解中的作用是在1964年，但直到20世纪80年代，系统动力学在项目中的具体应用才被报道出来，1990年以后，越来越多的系统动力学应用于项目管理的例子才被报道出来。系统动力学典型的应用领域是那些预算高、风险较大的领域，如航空航天、软件开发以及目前英吉利海峡隧道的开发等项目。第一个模型是为检验研究和开发项目的动态过程而建立的。理论进展和实际进展的概念明确表示，管理决策是基于对项目状态的认知，而该状态有可能与现实是完全不同的。理查森和普格开发了研发项目模型，并组织各种针对返工、未发现返工、感知进展、实际进展及认知生产力和实际生产力的新概念进行调查研究。在由普格-罗伯茨协会负责开发的“项目管理模拟系统”中已纳入许多这类功能，并且该系统已被用于支持一些大型项目管理活动中。有关的其他研究探讨了专门的应用领域，