系统工程复习

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 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 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) 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. The 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.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 System1.1.1Four Basic Attributes of the System(3) Goalseeking. 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. An objective that is measurable by any means is called a goal/target. For example ： 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.1.1.1Four 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. For example， A business system is a selforganizing system, in that it generates a diversified variety of activities, resulting in economies of scope. 1.2 Systems DefinedFour Definitions of Systems On the basis of 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 units. 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 relationships 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), 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. 1.2 Systems Defined(4) Procedural (or dynamic) definition. The process of transformation in the inputoutput 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 procedurea series of chronological, logical steps by which all repetitive tasks are performed. 1.2 DEFINITIONS OF SYSTEMS ENGINEERINGTABLE 1.1 Definitions of Systems Engineeringn Structure Systems engineering is management technology 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 ENGINEERINGThe 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:n Issue formulationn Issue analysisn Issue interpretationThese are each conducted at each of the lifecycle 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 Engineeringn Function Systems engineering is an appropriate combination of the methods and tools of systems engineering, made possible through use of a suitable methodology and systems management procedures, in a useful processoriented setting that is appropriate for the resolution of realworld problems, often of large scale and scope.1.2 DEFINITIONS OF SYSTEMS ENGINEERINGThe functional definition of 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. 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 ENGINEERINGn Purpose The purpose of systems engineering is information 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.1.2 DEFINITIONS OF SYSTEMS ENGINEERINGWe 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 processrelated activities that result in a trustworthy system. 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 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:n 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 theories. In a sense, these represent the why associated with the functioning of systems. 1.4 SYSTEMS ENGINEERING KNOWLEDGEFor 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 velocity and velocity is the derivative of position, we have now. What we have here is a simple model of onedimensional 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 KNOWLEDGEdoubtlessly 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 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 effectiveness of this particular car.1.4 SYSTEMS ENGINEERING KNOWLEDGE n Knowledge practices, which represent the accumulated wisdom and experiences that have led to the development of standard operating policies for wellstructured 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 KNOWLEDGEThen 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 automobile, 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 n Knowledge 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 gasoline prices due to an oil embargo. Or we might envision renewed concern for environmental preservation. Each of these 1.4 SYSTEMS ENGINEERING KNOWLEDGEcould 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 batterypowered automobiles. For these to be costeffective, 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 lowpowercapacity automobiles. 1.4 SYSTEMS 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 design. The framework consists of three dimensions:n A logic dimension that consists of three fundamental stepsn A time dimension that consists of t