1、Systems Engineering Review系統工程Chapter 1 Introduction to Systems Engineering 1.1Attributes Characterizing Systems (1)Four Basic Attributes of the System (1) Assemblage(集合). A system consists of a number of distinguishable units (elements, components, factors, subsystems, etc.), which may be physical

2、or conceptual, natural or artificial. For Example, Consider a university as a system for producing educated graduates. Some of the parts of the university system are structural or static components, such as university buildings. As the system is operating, these structural components usually do not

3、change much. Operating components are dynamic and perform processing such as the professors in a university who teach students. Flow components are often material, energy, or information; but in this example, students are the parts that flow or matriculate through the university system(2) Relationsh

4、ip. Several units assembled together are merely a group or a set. For such a group to be admissible as a system, a relationship or an interaction must exist among the units. The systems point of view also recognizes that a problem and its solution have many elements or components, and there are many

5、 different relations among them. For example, grades are one mechanism機制 for interaction between professors and students. Grades serve a purpose, intended or not.1.1.1Four Basic Attributes of the System1.1.1Four Basic Attributes of the System(3) Goal-seeking. An actual system as a whole performs a c

6、ertain function or aims at single or multiple objectives. Wherever these objectives are attained at their maximum/minimum levels, system optimization is said to have been performed. An objective that is measurable by any means is called a goal/target. For example ：A manufacturing system effectively

7、converts resources of production into produced goods (products), attaining an objective that creates high utilities by adding values to the raw materials, resulting in superior quality, cost and delivery.1.1.1Four Basic Attributes of the System(4) Adaptability to environment. A specific, factual sys

8、tem behaves so as to adapt to the change in its surroundings, or external environment. For example，A business system is a self-organizing system, in that it generates a diversified variety of activities, resulting in economies of scope. 1.2 Systems Defined Four Definitions of Systems On the basis of

9、 the foregoing considerations, the four essential definitions of systems can now be given as follows (Hitomi, 1975).1.2 Systems Defined (1) Abstract (or basic) definition. On the basis of the first two attributes above, a system is a collection of recognizable units having relationships among the un

10、its. Under this definition, general system theory has been developed, wherein things are deliberated theoretically, logically, and speculatively. 1.2 Systems Defined(2) Structural (or static) definition. On the basis of all four attributes, a system is a collection of recognizable units having relat

11、ionships among the units, aiming at specified single or multiple objectives subject to its external environment. 1.2 Systems Definedn(3) Transformational (or functional) definition. From the last attribute, the effects of the environment upon the system are inputs (including unforeseen disturbances)

12、, and, conversely, the effects in which the system influences the environment are outputs. From this consideration a system receives inputs from its environment, transforms them to outputs, and releases the outputs to the environment, whilst seeking to maximize the productivity of the transformation

13、. 1.2 Systems Defined(4) Procedural (or dynamic) definition. The process of transformation in the input-output system consists of a number of related stages, at each of which a specified operation is carried out. By performing a complete set of operations according to the precedence relationship on

14、the stages, a function or task is accomplished. Thus, a system is a procedure-a series of chronological, logical steps by which all repetitive tasks are performed. 1.2 DEFINITIONS OF SYSTEMS ENGINEERING TABLE 1.1 Definitions of Systems EngineeringStructure Systems engineering is management technolog

15、y to assist clients through the formulation, analysis, and interpretation of the impacts of proposed policies, controls, or complete systems upon the need perspectives, institutional perspectives, and value perspectives of stakeholders to issues under consideration.1.2 DEFINITIONS OF SYSTEMS ENGINEE

16、RING The structural definition of systems engineering tells us that we are concerned with a framework for problem resolution that, from a formal perspective at least, consists of three fundamental steps:Issue formulationIssue analysisIssue interpretation These are each conducted at each of the life-

17、cycle phases that have been chosen in order to implement the basic phased efforts of definition, development, and deployment. 1.3 DEFINITIONS OF SYSTEMS ENGINEERINGTABLE 1.1 Definitions of Systems EngineeringFunctionSystems engineering is an appropriate combination of the methods and tools of system

18、s engineering, made possible through use of a suitable methodology and systems management procedures, in a useful process-oriented setting that is appropriate for the resolution of real-world problems, often of large scale and scope.1.2 DEFINITIONS OF SYSTEMS ENGINEERING The functional definition of

19、 systems engineering says that we will be concerned with an appropriate combination of methods and tools. We will denote the result of the effort to obtain this combination as a systems methodology. Systems engineering methodology is concerned with the life cycle or process used for system evolution

20、. The functional definition of systems engineering also says that we will accomplish this in a useful and appropriate setting. This useful setting is provided by an appropriate systems management process. 1.3 DEFINITIONS OF SYSTEMS ENGINEERINGnPurpose The purpose of systems engineering is informatio

21、n and knowledge organization that will assist clients who desire to define, develop, and deploy total systems to achieve a high standard of overall quality, integrity, and integration as related to performance, trustworthiness, reliability, availability, and maintainability of the resulting system.1

22、.2 DEFINITIONS OF SYSTEMS ENGINEERING We will use the term systems management to refer to the cognitive and organizational tasks necessary to produce a useful process, methodology, or product line for system evolution and to manage the process-related activities that result in a trustworthy system.

23、More specifically, the result of systems management is an appropriate combination of the methods and tools of systems engineering, including their use in a methodological setting, with appropriate leadership in managing system process and product development, to ultimately field a system that can be

24、 used by clients to satisfy the needs that led to its development. 1.4 SYSTEMS ENGINEERING KNOWLEDGE Figure 1.8 illustrates that systems engineering knowledge is comprised of the following:Knowledge principles, which generally represent formal problem solving approaches to knowledge, generally emplo

25、yed in new situations and/or unstructured environments。 Knowledge principles include a host of scientific theories. In a sense, these represent the why associated with the functioning of systems. 1.4 SYSTEMS ENGINEERING KNOWLEDGE For example, one knowledge principle is that associated with Newtons l

26、aw. It suggests that force is equal to mass times acceleration and that because acceleration is the derivative of velocity and velocity is the derivative of position, we have now. What we have here is a simple model of one-dimensional motion. We could continue to extrapolate on this model of motion,

27、 based on Newtons law of mechanics, until we actually come up with a differential equation, 1.4 SYSTEMS ENGINEERING KNOWLEDGE doubtlessly a very complicated one, that could be used to predict the motion of an automobile when subjected to various forcing functions due to different time histories of a

28、ccelerator pedal movement and braking controls. Then we could use this differential equation to project the time that would be required to stop a fancy sports car traveling at 60 miles per hour under a certain type of braking action. We would be using knowledge principles to predict the braking effe

29、ctiveness of this particular car.1.4 SYSTEMS ENGINEERING KNOWLEDGE nKnowledge practices, which represent the accumulated wisdom and experiences that have led to the development of standard operating policies for well-structured problems。n Alternately, we could develop a set of knowledge practices th

30、at are based on actual experimental observations of different drivers breaking different cars. 1.4 SYSTEMS ENGINEERING KNOWLEDGE Then we could publish such a table. The table might be adopted as a standard, and any particular car that could not stop in the distance specified by the standard might we

31、ll be subjected to an appropriate repair effort. While the table might have its basis in the physical differential equations for an automobile, there would not necessarily be any reference to these knowledge principles in obtaining the table. The knowledge principles associated with vehicle motion d

32、ynamics would be very useful, however, in the design of various subsystems for the automobile.1.4 SYSTEMS ENGINEERING KNOWLEDGE nKnowledge perspectives, which represent the view that is held relative to future directions and realities in the technological area under consideration。n Knowledge perspec

33、tives are needed when we attempt to project various futures for the automobile. n For example, we might envision a significant increase in gasoline prices due to an oil embargo. Or we might envision renewed concern for environmental preservation. Each of these 1.4 SYSTEMS ENGINEERING KNOWLEDGE could

34、 lead to significant interest in smaller size engines, engines that would result in greater fuel use efficiency at the expense of lower power. This could increase the incentives for electric battery-powered automobiles. For these to be cost-effective, there would have to be a technological revolutio

35、n in battery storage capacities. There would have to be other changes, such as in societal willingness to accept low-power-capacity automobiles. 1.4 SYSTEMS ENGINEERING KNOWLEDGE Chapter 2 Methodological Frameworks and Systems Engineering Processes 2.1 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITI

36、ON 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:A logic dimension that consists of three fundamental stepsA time dimension that consists of thre

37、e basic life cycle phasesA perspectives dimension that consists of three stages or life cycles2.1 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION This three-level structured hierarchy comprises a systems engineering life cycle and is one of the ingredients of systems engineering meth

38、odology. It involvesSystem definitionSystem developmentSystem deployment2.1 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 mu

39、ch more detail later, these three steps can be disaggregated into 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

40、 systems engineering life cycles. These relate to the three different 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 METHODOLO

41、GICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Thus we may 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 sy

42、stems engineering. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION 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

43、 nThe systems planning and marketing life cycle is intended to yield 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 consider

44、ations)? nThe acquisition life cycle is intended to yield answers 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 s

45、uggests that the needs of one life cycle should not be considered independently of the other two. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Each of the logical steps of systems engineering is accomplished for each of the life-cycle phases. There are generally three differen

46、t 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 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

47、 stages of a complete systems engineering effort. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Figure 2.7 illustrates this framework of steps, phases, and stages as a three-dimensional cube. This is one three-dimensional framework, in the form of a morphological box, for syste

48、ms engineering.2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION A methodology 方法學 is an open set of procedures for problem solving. 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 u

49、se 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 number of disciplines that enable formulation構思、規劃, analysis, and interpretation of the phased efforts that are associated with the definition, develo

50、pment, and deployment of both an appropriate process and the product that results from use of this process. 2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION Associated with a methodology is a structured framework into which particular methods are associated for resolution of a spe

51、cific issue. Let us now develop the structured framework of steps, phases, and stages in systems engineering in more detail.(1) Logical Steps of Systems Engineering As we have noted, all characterizations of systems engineering will necessarily involve three logical steps 1-4:Formulation of the syst

52、ems engineering problem under considerationAnalysis to determine the impacts of the alternativesInterpretation of these impacts in accordance with the value system of the decision maker(s), and selection of an appropriate plan of action to continue the effort. These three steps, or an expansion ther

53、eto to more explicitly indicate the actual activities associated with each phase, are conducted at each and every phase of the systems engineering life cycle.(1) Logical Steps of Systems Engineering We can expand 擴展 the three fundamental steps of systems engineering in many ways. However, probably t

54、he 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 the three basic steps of formulation, analysis, and interpretation follows.(1) Logical Steps of Systems Engineering Formulation1. Problem Definition.

55、This step involves isolating, quantifying, and clarifying the need that creates the problem and describing the set of environmental factors that constrains alterables for the system to be developed.It involves identifying a set of needs, alterables, and constraints associated with the issue formulat

56、ion.2. Value System Design. This step involves selection of the set of objectives or goals that guides the search for alternatives. Value system design enables determination of the multidimensional attributes or decision criteria for selecting the most appropriate system. It involves the identificat

57、ion and validation of a set of objectives and objectives measures.(1) Logical Steps of Systems Engineering Formulation 3. System Synthesis. This step involves searching for, or hypothesizing, a set of alternative courses of action or options. Each alternative must be described in sufficient detail t

58、o permit analysis of the impacts of implementation and subsequent evaluation and interpretation with respect to the objectives. As part of this step, we identify a number of potential alternatives and associated alternatives measures.(1) Logical Steps of Systems Engineering Analysis4. System Analysi

59、s and Modeling. As a part of this step, we determine specific impacts or consequences of the alternatives 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 effec

60、tiveness or benefits. There are a variety of simulation and modeling methods, and a great variety of operations research approaches that are of potential value here.5. Refinement of the Alternatives. As part of this step, we attempt to adjust, and hopefully optimize, the system variables in order to bes