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1、Systems Engineering Review,系统工程,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 or conc
2、eptual,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 change much.Op
3、erating 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)Relationship.Several units ass
4、embled 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 different relations amon
5、g them.For example,grades are one mechanism（机制）for interaction between professors and students.Grades serve a purpose,intended or not.,1.1.1Four Basic Attributes of the System,1.1.1Four Basic Attributes of the System,(3)Goal-seeking.An actual system as a whole performs a certain function or aims at
6、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 converts resources of production
7、 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 system behaves so as to adapt to the cha
8、nge 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 the foregoing considerations,the four es
9、sential 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 units.Under this definition,general system theory
10、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 relationships among the units,aiming at specified single or mu
11、ltiple objectives subject to its external environment.,1.2 Systems Defined,(3)Transformational(or functional)definition.From the last attribute,the effects of the environment upon the system are inputs(including unforeseen disturbances),and,conversely,the effects in which the system influences the e
12、nvironment 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.,1.2 Systems Defined,(4)Procedural(or dynamic)definition.The process o
13、f 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 the stages,a function or task is accomplished.Thus,a system is a procedure-a
14、 series of chronological,logical steps by which all repetitive tasks are performed.,1.2 DEFINITIONS OF SYSTEMS ENGINEERING,TABLE 1.1 Definitions of Systems EngineeringStructureSystems engineering is management technology to assist clients through the formulation,analysis,and interpretation of the im
15、pacts 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 ENGINEERING,The structural definition of systems engineering tells us that we are concerned w
16、ith 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-cycle phases that have been chosen in order to implement the basic phased efforts of def
17、inition,development,and deployment.,1.3 DEFINITIONS OF SYSTEMS ENGINEERING,TABLE 1.1 Definitions of Systems EngineeringFunctionSystems engineering is an appropriate combination of the methods and tools of systems engineering,made possible through use of a suitable methodology and systems management
18、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 systems engineering says that we will be concerned with an appropriate combination of meth
19、ods 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.The functional definition of systems engineering also says that we will accomplish this in a
20、 useful and appropriate setting.This useful setting is provided by an appropriate systems management process.,1.3 DEFINITIONS OF SYSTEMS ENGINEERING,PurposeThe purpose of systems engineering is information and knowledge organization that will assist clients who desire to define,develop,and deploy to
21、tal 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.,1.2 DEFINITIONS OF SYSTEMS ENGINEERING,We will use the term systems management to refer to the cognitive
22、 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.More specifically,the result of systems management is an appropriate combination of the methods and tools
23、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 used by clients to satisfy the needs that led to its development.,1.4 SYSTEMS ENGINEERING KNOWLEDGE,Figure 1.
24、8 illustrates that systems engineering knowledge is comprised of the following:Knowledge principles,which generally represent formal problem solving approaches to knowledge,generally employed in new situations and/or unstructured environments。Knowledge principles include a host of scientific theorie
25、s.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 law.It suggests that force is equal to mass times acceleration and that because acceleration is the derivative of vel
26、ocity 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,based on Newtons law of mechanics,until we actually come up with a differential equation,1.4 SYSTEMS ENGINEERING KNOWLED
27、GE,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 accelerator pedal movement and braking controls.Then we could use this differential equation to project the time that would b
28、e 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 effectiveness of this particular car.,1.4 SYSTEMS ENGINEERING KNOWLEDGE,Knowledge practices,which represent the accumulated wisdom
29、 and experiences that have led to the development of standard operating policies for well-structured problems。Alternately,we could develop a set of knowledge practices that are based on actual experimental observations of different drivers breaking different cars.,1.4 SYSTEMS ENGINEERING KNOWLEDGE,T
30、hen 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 well be subjected to an appropriate repair effort.While the table might have its basis in the physical differential equations for an a
31、utomobile,there would not necessarily be any reference to these knowledge principles in obtaining the table.The knowledge principles associated with vehicle motion dynamics would be very useful,however,in the design of various subsystems for the automobile.,1.4 SYSTEMS ENGINEERING KNOWLEDGE,Knowledg
32、e perspectives,which represent the view that is held relative to future directions and realities in the technological area under consideration。Knowledge perspectives are needed when we attempt to project various futures for the automobile.For example,we might envision a significant increase in gasol
33、ine prices due to an oil embargo.Or we might envision renewed concern for environmental preservation.Each of these,1.4 SYSTEMS ENGINEERING KNOWLEDGE,could lead to significant interest in smaller size engines,engines that would result in greater fuel use efficiency at the expense of lower power.This
34、could increase the incentives for electric battery-powered automobiles.For these to be cost-effective,there would have to be a technological revolution in battery storage capacities.There would have to be other changes,such as in societal willingness to accept low-power-capacity automobiles.,1.4 SYS
35、TEMS ENGINEERING KNOWLEDGE,Chapter 2 Methodological Frameworks and Systems Engineering Processes,2.1 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,In this section we present and explain the complete systems engineering process with emphasis on frameworks for systems methodology and
36、 design.The framework consists of three dimensions:A logic dimension that consists of three fundamental stepsA time dimension that consists of three basic life cycle phasesA perspectives dimension that consists of three stages or life cycles,2.1 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR P
37、RODUCTION,This three-level structured hierarchy comprises a systems engineering life cycle and is one of the ingredients of systems engineering methodology.It involvesSystem definitionSystem developmentSystem deployment,2.1 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,Our model of
38、 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 into a number of others.Each of these steps of systems engineering is accomplished for each of
39、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 different stages of effort that are needed to result in a competitive product or service in the ma
40、rketplace: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 may imagine a three-dimensional model of systems engineering that is comprised of steps associated with
41、each phase of a life cycle,the phases in the life cycle,and the life cycles that comprise the coarse structure（大体框架）or stages of systems engineering.,2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,Figure 2.5 illustrates this across three distinct but interrelated life cycles,for
42、 the three steps and three phases that we have described here.,2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,The systems planning and marketing life cycle is intended to yield answers to the question;What is in demand?The research,development,test,and evaluation life cycle is i
43、ntended to yield answers to the question;What is(technologically)possible(within reasonable economic and other considerations)?The acquisition life cycle is intended to yield answers to the question;What can be developed?It is only in the region where there is overlap（重叠）,actually in an n-dimensiona
44、l 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 independently of the other two.,2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,Each of the logical ste
45、ps 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 engineering that is compris
46、ed 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,phases,and stages as a three-
47、dimensional cube.This is one three-dimensional framework,in the form of a morphological box,for systems engineering.,2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,A methodology（方法学）is an open set of procedures for problem solving.Consequently（因此、所以）,a methodology involves a set
48、 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 number of disciplines that enable formulation（构思、规划）,a
49、nalysis,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.,2.2 METHODOLOGICAL FRAMEWORKS FOR SYSTEMS ACQUISITION OR PRODUCTION,Associated with a methodology
50、is a structured framework into which particular methods are associated for resolution of a specific 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 sy
