《系統(tǒng)工程第二章》ppt課件

1、Chapter 2 Methodological Frameworks and Systems Engineering Processes (方法論框架和系統(tǒng)工程過程方法論框架和系統(tǒng)工程過程) There are a number of frameworks框架、體系 that we might use to characterize 描畫 systems engineering efforts. We will describe some of them in this chapter. Without a sound and well-understood product line, or

2、 process, for the acquisition or production of large systems, it is very likely that there will be a number of flaws 缺陷 in the resulting system itself. Thus, the definition, development, and deployment 部署 of an appropriate 恰當(dāng)?shù)?process, or set of processes, for systems production is very important. 2

3、.1 INTRODUCTION In this chapter we first discuss the nature of systems acquisition 收買, production 消費(fèi), procurement 采購, or manufacturing 制造業(yè). We will generally 通常 use the word acquisition to describe each of these efforts. As systems engineers, we are primarily concerned with the functional and physic

4、al architectures that lead to implementation architectures and the resulting detailed design of systems of all types. Design and development is very important, even though the acquisition or production process also depends upon success in the definition and deployment 部署 phases of the life cycle. De

5、sign and development is a creative process through which system products, presumed to be responsive to client needs and requirements, are conceptualized or specified, manufactured or otherwise produced, and fielded or implemented in such a way that they can be maintained over time. 2.1 INTRODUCTION

6、There are four primary ingredients in our definition of design and development, and they apply to software design as well as to the design of hardware and physical systems.Development results from specifications 規(guī)格 or architecture for a product or system.Development is a creative process.Development

7、 activity includes design effort, which is conceptual in nature.A successful design and development must be broadly responsive to client needs and requirements.2.1 INTRODUCTION Good systems engineering practice 實(shí)際 requires that the systems engineer be responsive to each of these four ingredients for

8、 quality design and development efforts. The final ingredient requires a set of needs and requirements of the client for the desired product, process, or system. This information requirement serves as the input to the systems engineering process that leads to design. Systems engineering is creative,

9、 and it is a process that is conceptual and pragmatic 概念和務(wù)虛 in nature. The initial result of this creative, conceptual, and pragmatic process is information concerning the specifications or architecture for the product or service that will ultimately be manufactured, implemented, installed, or broug

10、ht to fruition享用 in some other way. A later result is the system itself and plans for its evolution over time.2.1 INTRODUCTION In the detailed efforts that follow, we first discuss systems engineering methodology and systems engineering life cycles as necessary elements in the systems engineering pr

11、ocess. This leads to a number of conceptual frameworks for systems engineering processes. 2.1 INTRODUCTION In this chapter, we will discuss the systems acquisition, or production, process in terms of a number of steps and phases that may comprise this process. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTE

12、MS ACQUISITION OR PRODUCTION In this section we present and explain the complete systems engineering process with emphasis on frameworks for systems methodology and design. The framework consists of three dimensions 方面 :A logic dimension 邏輯層面 that consists of three fundamental stepsA time dimension

13、that consists of three basic life cycle phasesA perspectives dimension 觀念層面 that consists of three stages or life cycles2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION We envision 想象 a three-performance level hierarchy 三層次構(gòu)造性能 for systems engineering phased efforts, such as shown

14、 in Figure 2.2. This three-level structured hierarchy comprises a systems engineering life cycle and is one of the ingredients of systems engineering methodology. It involves:System definitionSystem developmentSystem deployment2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION We il

15、lustrate forward flow of information, and feedback 反響 from one phase to the other. Usually, this is needed as a situation in which information only flows in one direction from one phase to a subsequent phase will not allow for iterative improvement. 迭代改良 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQ

16、UISITION OR PRODUCTION It is generally also very desirable to allow for learning as the life-cycle process is iteratively repeated 反復(fù)迭代. Figure 2.3 illustrates three different information flow patterns. Generally, the one with learning and feedback is to be preferred. We will, however, discuss some

17、extensions of the basic waterfall life-cycle model, illustrated on the left side of Figure 2.3. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION As we shall soon discuss, this three-phase life cycle may be expanded into a life cycle comprised 包含 of a larger number of phases. Gener

18、ally the number of phases is in the vicinity 周圍地域 of seven, although it may contain quite a few more than seven phases 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Regardless of 不論、雖然 the way in which the systems engineering life-cycle process is characterized, and regardless

19、of the type of product or system or service that is being designed, all characterizations of the phases of the systems engineering life cycles will necessarily involve:Formulation of the Problem 問題的規(guī)劃 in which the needs and objectives of a client group are identified, and potentially acceptable desi

20、gn alternatives, or options, are identified or generated.Analysis of the Alternatives 變量的分析 in which the impacts of the identified design options are identified and evaluated.Interpretation 解釋、闡明 and Selection in which the options, or alternative courses of action, are compared by means of an evalua

21、tion of the impacts of the alternatives and how these are valued by the client group. The needs and objectives of the client group are necessarily used as a basis for evaluation. The most acceptable alternative is selected for implementation or further study in a subsequent phase of systems engineer

22、ing.2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Our model of the steps of the logic structure of the systems process, shown in Figure 2.4, is based upon this conceptualization. As we shall also indicate in much more detail later, these three steps can be disaggregated 分解 into

23、 a number of others. Each of these steps of systems engineering is accomplished for each of the life cycle phases.2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION As we have noted, there are generally three different systems engineering life cycles. These relate to the three diffe

24、rent stages of effort that are needed to result in a competitive product or service in the marketplace: Research, development, test, and evaluation (RDT&E)System acquisition or productionSystems planning and marketing 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Thus we ma

25、y imagine a three-dimensional model of systems engineering that is comprised of steps associated with each phase of a life cycle, the phases in the life cycle, and the life cycles that comprise the coarse structure 大體框架 or stages of systems engineering. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQU

26、ISITION OR PRODUCTION Figure 2.5 illustrates this across three distinct but interrelated life cycles, for the three steps and three phases that we have described here. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION nThe systems planning and marketing life cycle is intended to yi

27、eld answers to the question; What is in demand? nThe research, development, test, and evaluation life cycle is intended to yield answers to the question; What is (technologically) possible (within reasonable economic and other considerations)? nThe acquisition life cycle is intended to yield answers

28、 to the question; What can be developed? n It is only in the region where there is overlap 重疊, actually in an n-dimensional space, that responsible actions should be implemented to bring about programs for all three life cycles. This suggests that the needs of one life cycle should not be considered

29、 independently of the other two. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Figure 2.6 attempts to represent this conceptually for two-dimensional representations of the possibility space for each life cycle. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTIO

30、N Each of the logical steps of systems engineering is accomplished for each of the life-cycle phases. There are generally three different systems engineering lifecycles or stages for a complete systems engineering effort, as we have indicated. Thus we may imagine a three-dimensional model of systems

31、 engineering that is comprised of steps associated with each phase of a life cycle, the phases in the life cycle, and the life cycles or stages of a complete systems engineering effort. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Figure 2.7 illustrates this framework of steps

32、 步驟, phases 方面, and stages 階段 as a three-dimensional cube. This is one three-dimensional framework, in the form of a morphological 形狀學(xué) box, for systems engineering.2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION A methodology 方法學(xué) is an open set of procedures for problem solving.

33、Consequently 因此、所以, a methodology involves a set of methods, a set of activities, and a set of relations between the methods and the activities. To use a methodology we must have an appropriate set of methods. Generally, these include a variety of qualitative 定性的 and quantitative approaches from a n

34、umber of disciplines that enable formulation構(gòu)思、規(guī)劃, analysis, and interpretation of the phased efforts that are associated with the definition, development, and deployment of both an appropriate process and the product that results from use of this process. Associated with a methodology is a structur

35、ed framework into which particular methods are associated for resolution of a specific issue.2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Let us now develop the structured framework of steps, phases, and stages in systems engineering in more detail.(1) Logical Steps of Systems

36、 Engineering As we have noted, all characterizations of systems engineering will necessarily involve three logical steps 1-4:Formulation of the systems engineering problem under considerationAnalysis to determine the impacts of the alternativesInterpretation of these impacts in accordance with the v

37、alue system of the decision maker(s), and selection of an appropriate plan of action to continue the effort. These three steps, or an expansion thereto to more explicitly indicate the actual activities associated with each phase, are conducted at each and every phase of the systems engineering life

38、cycle.(1) Logical Steps of Systems Engineering We can expand 擴(kuò)展 the three fundamental steps of systems engineering in many ways. However, probably the most useful expansion is the seven steps identified by Hall 5. Our construal(解釋) of these seven steps of systems engineering and their relation to th

39、e three basic steps of formulation, analysis, and interpretation follows.(1) Logical Steps of Systems Engineering FormulationProblem Definition. 問題的定義問題的定義 This step involves isolating 分別分別, quantifying 量化量化, and clarifying 論述論述 the need that creates the problem and describing the set of environment

40、al factors that constrains alterables 約束變量約束變量 for the system to be developed. It involves identifying a set of needs, alterables, and constraints associated with the issue formulation.Value System Design. 價(jià)值系統(tǒng)設(shè)計(jì)價(jià)值系統(tǒng)設(shè)計(jì) This step involves selection of the set of objectives or goals that guides the se

41、arch for alternatives. Value system design enables determination of the multidimensional attributes or decision criteria for selecting the most appropriate system. It involves the identification and validation 確認(rèn)確認(rèn) of a set of objectives and objectives measures.System Synthesis. 系統(tǒng)綜合系統(tǒng)綜合 This step i

42、nvolves searching for, or hypothesizing 假定、猜測(cè)假定、猜測(cè), a set of alternative courses of action or options. Each alternative must be described in sufficient detail to permit analysis of the impacts of implementation and subsequent evaluation and interpretation with respect to the objectives. As part of t

43、his step, we identify a number of potential alternatives and associated alternatives measures.(1) Logical Steps of Systems Engineering AnalysisSystem Analysis and Modeling 系統(tǒng)分析與建模系統(tǒng)分析與建模. As a part of this step, we determine specific impacts 確定確定詳細(xì)的影響要素詳細(xì)的影響要素 or consequences of the alternatives 變量結(jié)

44、果變量結(jié)果 that were specified as relevant to the issue under consideration by the value system. These impacts may relate to such important concerns as product quality, market, reliability, cost, and effectiveness or benefits. There are a variety of simulation and modeling methods, and a great variety of

45、 operations research approaches that are of potential value here.Refinement of the Alternatives 細(xì)化變量細(xì)化變量. As part of this step, we attempt to adjust, and hopefully optimize, the system variables in order to best meet system objectives and satisfy system constraints.(1) Logical Steps of Systems Engin

46、eering Interpretation Decision Making 制定戰(zhàn)略制定戰(zhàn)略. This step involves evaluating the impacts or consequences of the alternatives and, thereby, interpreting the alternatives in terms of the extent to which they achieve objectives. The alternatives are identified in system synthesis and subsequently mode

47、led and refined in the analysis steps of effort, in accordance with satisfaction of objectives associated with the value system. This enables interpretation of these evaluations such that all alternatives can be compared relative to human values. One or more alternatives, or courses of action, can t

48、hen be selected for advancing to the next step.Planning for Action. This step involves communicating the results of the effort to this point and looking ahead to the next phase of the systems engineering life cycle under consideration. This includes such pragmatic efforts as scheduling subsequent ef

49、forts, allocating resources to accomplish them, and setting up system management controls. If we are conducting a single phase effort, this step would be the final one. More generally, it leads to a new phase of effort in continuation of a systems engineering life cycle.(1) Logical Steps of Systems

50、Engineering figure 2.8 indicates the waterfall nature of these seven steps of systems engineering and their relation to the three fundamental logical steps. The seven steps of systems engineering are generally carried out in an iterative fashion for each phase of the systems engineering life cycle.

51、(1) Logical Steps of Systems Engineering Because the efforts and purposes of the various phases of the life cycle are quite different, the specific tools and methods that are appropriate to accomplish each of the seven steps can be expected to be quite different from one systems engineering process

52、phase to another. It is quite possible to go back to refine and improve the results of any earlier step as a consequence of the results of any later step. We do not show these iterative feedback loops in Figure 2.8. (2) Life-Cycle Phases of Systems Engineering As we have often indicated a typical sy

53、stems engineering life cycle has three basic phasesdefinition, development, and deployment. For large systems, these three phases need expansion into a number of more finely defined phases. This enables the various phases to be better understood, communicated, and controlled in order to support trus

54、tworthy systems engineering efforts. Before describing specific life-cycle methodologies later in this chapter, we present and explain a general and very useful seven-phase life-cycle expansion and its relation to the basic three-phase systems engineering life cycle that we presented in Figures 2.2

55、and 2.3. Figure 2.9 illustrates the seven-phase life cycle, actually representing acquisition or production, that we now consider.(2) Life-Cycle Phases of Systems Engineering The seven phases in this life cycle may be described as follows:(2) Life-Cycle Phases of Systems Engineering System Definitio

56、n 1. Requirement and Specifications. The first part of system engineering effort results in the identification of user requirements and the translation of these into technological specification for a product, process, or system. The goal of this phase is the identification of client and stakeholder

57、needs, activities, and objectives for the functionally operational system. This means that information is a necessary ingredient and results in the mandate to obtain, from the client for a systems engineering effort, a set of needs and requirements for the product, process, or system that is to resu

58、lt from the effort. This information requirement serves as the input to the rest of the systems engineering process. This phase results in the identification and description of preliminary conceptual design considerations for the next phase. It is necessary to translate operational deployment needs

59、into requirements specifications so that these needs may be addressed by the system design and development efforts. Thus, information requirements specifications are affected by, as well as affect, each of the other design and development phases of the systems engineering life cycle.(2) Life-Cycle P

60、hases of Systems Engineering 2.Preliminary Conceptual Design and System Architecting. The primary goal of this phase is to develop several concepts that might work that are responsive to the specifications identified in the previous phase of the life cycle. A preliminary conceptual design, one that is