系统工程第一章

Systems Engineering系统工程鄢萍 教授 /博导12007 SYSTEMS ENGINEERINGnCourse Name: Systems EngineeringnCourse Hours and Credits: 30 Hs, 2ScrsnTextbook: n Introduction to System Engineering Andre P. Sage George Mason Universityn Introduction to Operation Research, Seventh Edition, Prof. Hiller, Stanford Universityn 系统工程教程： 喻湘存，熊曙初，清华大学出版社n 系统工程 ，第三版，汪应洛，机械工业出版社Date 22007 SYSTEMS ENGINEERINGDate 32007 SYSTEMS ENGINEERINGDate 42007 SYSTEMS ENGINEERINGnTesting:nNormal Testing, but the answer should be written in English.Date 52007 SYSTEMS ENGINEERINGChapter 1 Introduction to Systems Engineering 62007 SYSTEMS ENGINEERINGIntroduction to Systems Engineering1.1 THE SYSTEMS POINT OF VIEW1.2 DEFINITIONS OF SYSTEMS ENGINEERING 1.3 HISTORY OF TECHNOLOGICAL DEVELOPMENT 1.4 SYSTEMS ENGINEERING KNOWLEDGE 1.5 The APPLICATION OF SYSTEMS ENGINEERING Date 72007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWBecause systems engineering is often described as a “new way of thinking,“ we need to describe what we mean by the systems point of view. This will lead us to see that it is not really new. The systems perspective takes a “big picture“ or holistic, or gestalt, view of large-scale problems and their proposed technological solutions. Date 82007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWThis means that systems engineers not only examine the specifics(细节 ) of the problem under consideration but also investigate relevant factors in the surrounding environment. They realize that problems are embedded in a situation or environment that can have significant impacts on the problem and its proposed alternative solutions. This is not to say that systems engineers do not get very detailed or specific far from it. There is also much effort devoted to in scoping, high-fidelity modeling, and specification of system requirements and architecture. Date 92007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWThe systems viewpoint stresses（讲述了） that there usually is not a single correct answer or solution to a large-scale problem or design issue. Instead, there are many different alternatives （可选方案） that can be developed and implemented depending on the objectives （目标） the system is to serve and the values of the people and organizations with a stake in the solution. Lets add more detail to what we mean by the systems point of view. Date 102007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWFirst, a system is defined as a group of components that work together for a specified purpose. This is a very simple but correct definition. Purposeful action is a basic characteristic of a system. A number of functions must be implemented in order to achieve these purposes. This means that systems have functions. They are designed to do specific tasks. Date 112007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWSystems are often classified（分类） by their ultimate purpose: service-oriented systems, product-oriented systems, or process-oriented systems. nAn airport can be viewed as an example of a service system. The planes, pilots, mechanics, ticket agents, runways, and concourses are all components that work together to provide transport service to passengers and freight. nAn automobile assembly plant is an example of a product-oriented system. The raw materials, people, and machines all work together to produce a finished car. nA refinery that changes crude oil into gasoline is an example of a process-oriented system. Date 122007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWWe note here that the systems considered by systems engineers may be service systems, or they may be product systems. The systems may be systems designed for use by an individual or by groups of individuals. These systems may be private sector systems, or they may be government or public sector systems.Date 132007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWFor Example, An overhead projector（高射投影仪） may be viewed as a “system.“ So may the combination of an overhead projector, a screen on which it projects, and a set of overheads. The instructor using the overhead may also be included in the notion of “system.“ From another perspective, the combination of the overhead, screen, overheads, instructor, and students may be regarded as a “system.“Thus, when we use a term such as “engineer a system,“ we must be very careful to define the nature of the “system“ that we wish to engineer and what is included in. and exempted from, the notion of system. We must also be very concerned with the interfaces to the system that we are engineering.Date 142007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWThe systems point of view also recognizes that a problem and its solution have many elements or components, and there are many different relations among them.The important aspects of a problem are often a function of how the components interact. Simple aggregation of individual aspects of a problem is intuitively appealing but often wrong. The whole is often not simply the sum of its parts. Often, much more is involved. This does not suggest at all that scientific analysis, in which an issue is disaggregated into a number of component issues and understanding sought of the individual issues, is in any way improper. Date 152007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWThe following steps are essential in finding solutions to large and complicated problems:nDesegregation or decomposition（分解） of a large issue into smaller, more easily understandable partsnAnalysis of the resulting large number of individual issuesnAggregation of the results to attempt to find a solution to the major issueThis is the essence of the formal scientific method. Date 162007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWHowever, interpretation must follow analysis, and meaningful issue formulation must precede it. Also, these formal efforts need to be conducted across a variety of life-cycle phases. The systems approach attempts to incorporate all of these. Date 172007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWSystem components are often of very different types; and it is helpful, from a systems perspective, to distinguish among them. 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. 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. Date 182007 SYSTEMS ENGINEERING1.1 THE SYSTEMS POINT OF VIEWAgain, how the components interact is an important aspect of any system, its problems or design issues, and their alternative solutions.For example, grades are one mechanism（机制） for interaction between professors and students. Grades serve a purpose, intended or not. it is important to understand what purpose, intended and unintended, they serve.Date 192007 SYSTEMS ENGINEERING1.1.1Attributes Characterizing SystemsFour Basic Attributes of the SystemFrom among many characteristics, four basic attributes which play basic roles to characterize the system are described in the following (Hitomi, 1971):(1) Assemblage（集合、装配） . A system consists of a plural number of distinguishable units (elements, components, factors, subsystems（子系统） , etc.), which may be physical or conceptual, natural or artificial.Date 202007 SYSTEMS ENGINEERING(2) Relationship. 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.1.1.1Four Basic Attributes of the SystemDate 212007 SYSTEMS ENGINEERINGEXAMPLE 1.1nLogical relationship is determined essentially by definitions and assumptions, such as the relation of production, inventory, and sales in a period: Final inventory（最后清单） = initial inventory + production quantity（生产数量） - sales quantity. EXAMPLE 1.2nInstitutional relationship（体制关系） is specified（规定，指定） by social institution, laws, and regulations, such as：tax amount （税额） = profit (or income) tax rate. 1.1.1Four Basic Attributes of the SystemDate 222007 SYSTEMS ENGINEERING1.1.1Four Basic Attributes of the System(3) Goal-seeking. An actual system as a whole performs a certain 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. For this purpose it is necessary to be able to measure, objectively or subjectively, the degree of attainment of the objectives. An objective that is measurable by any means is called a goal/target. Date 232007 SYSTEMS ENGINEERINGEXAMPLE 1.3 A manufacturing system effectively 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. Date 242007 SYSTEMS ENGINEERINGEXAMPLE 1.4nA business management system coordinates functional divisions-production, sales personnel and finance, which constitutes the system-and allocates limited resources available to those divisions. This system aims at organizational objectives such as profit maximization, reasonable rate of return on capital, increase in market share, stable growth, public services (philanthropy), etc. Date 252007 SYSTEMS ENGINEERING1.1.1Four Basic Attributes of the System(4) Adaptability to environment. A specific, factual system behaves so as to adapt to the change in its surroundings, or external environment. This external environment influences and is influenced by the system, in that matter and/or energy and/or information are received from and given to each other. A system that is capable of controlling itself in such a way as to be always optimal even under changes in the external environment, is called an adaptive (or cybernetic) system. Date 262007 SYSTEMS ENGINEERINGIf this system possesses dynamic adaptability, app