专业英语电气工程P2U5教学课件.ppt
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1、自动化专业英语教程,教学课件,July 28,2007,P2U5A Introduction to Modern Control Theory 第二部分第五单元课文A 现代控制理论简介,A 现代控制理论简介 1.课文内容简介:主要介绍现代控制理论中现代控制理论产生的背景与原因,与传统控制理论之间的差别及其优点,状态的概念等内容。2.温习现代控制理论中绪论的内容。3.生词与短语constraint n.强迫,约束multiply v.加倍,倍增stimulus n.刺激,鼓励optimal control 最优控制dominate v.支配,使服从package n.包very large sc
2、ale integrated circuits(VLSI)超大规模集成电路,P2U5A Introduction to Modern Control Theory 第二部分第五单元课文A 现代控制理论简介,numerical adj.数字的matrix n.矩阵 pl.matriceslinear vector space 线性矢量空间ad hoc 尤其,特定地alleviate v.减轻,缓和arbitrary adj.任意的formulation n.公式化(表达)implementation n.实现,履行attain v.达到,实现constitute v.构造,组织insofar a
3、s 到这样的程度,在范围内continuum n.连续gross national product 国民生产总值trade deficit 贸易赤字scalar adj.数量的,标量的;n.数量,标量,P2U5A Introduction to Modern Control Theory 第二部分第五单元课文A 现代控制理论简介,n-dimensional adj.n维的circumstance n.状况,环境4.难句翻译1 The transition from simple approximate models,which are easy to work with,to more rea
4、listic models produces two effects.从易于处理的简单近似模型到实际一些的模型的转换存在两方面问题。2 It provides an ideal formulation for computer implementation and is responsible for much of the progress in optimization theory.它(现代控制理论)为计算机实现提供了理想的公式化方法,并对最优化理论的发展起了重要作用。,P2U5A Introduction to Modern Control Theory 第二部分第五单元课文A 现代控
5、制理论简介,3 As far as the state at t1 is concerned,it makes no difference how the initial state was attained.就t1时刻的状态而言,它与初始状态是怎样实现的无关。as far asbe concerned:就而言;make no difference:无论都没有区别(没关系)4 Thus the state at t0 constitutes a complete history of the system behavior prior to t0,insofar as that history
6、 affects future behavior.因此,t0时刻的状态构成了t0以前系统活动状态的历史,这个历史状态在一定范围内影响(系统)未来的行为。,A Introduction to Modern Control Theory,Classical control theory is based on inputoutput relationships,principally the transfer function.When differential equations are encountered,they are linearized and subjected to whate
7、ver constraints are necessary to establish useful input-output relationshipModem control theory,on the other hand,is based on direct use of the differential equations themselves.Although its technique are powerful and relatively simple,classical control theory does have limitations and shortcomings
8、that multiply as plants and control systems become more complex-thus the advent of modern control theory.,Several factors provided the stimulus for the development of modem control theory.(1)The necessity of dealing with more realistic models of systems(2)The shift in emphasis towards optimal contro
9、l and optimal system design(3)The continuing developments in digital computer technology(4)The shortcomings of previous approaches,(5)A recognition of the applicability of well-known methods in other fields of knowledge.,The transition from simple approximate models,which are easy to work with,to mo
10、re realistic models produces two effects.First,a larger number of variables must be included in the modelSecond,a more realistic model is more likely to contain nonlinearities and time-varying parameters.Previously ignored aspects of the system,such as interactions with and feedback through the envi
11、ronment,are more likely to be included,With an advancing technological society,there is a trend towards more ambitious goalsThis also means dealing with complex systems with a larger number of interacting componentsThe need for greater accuracy and efficiency has changed the emphasis on control syst
12、em performanceThe classical specifications in terms of percent overshoot,settling time,bandwidth,etc,have in many cases given way to optimal criteria such as minimum energy,minimum cost,and minimum time operationOptimization of these criteria makes it even more difficult to avoid dealing with unplea
13、sant nonlinearitiesOptimal control theory often dictates that nonlinear time-varying control laws be used,even if the basic system is linear and time-invariant,The continuing advances in computer technology have had important effects on the controls field.The fast processing ability and large memory
14、 capacity of digital computers make it possible to solve practical problems with complex high-order differential equationsClassical control theory was dominated by graphical methods because at the time that was the only way to solve certain problemsNow every control designer has easy access to power
15、ful computer packages for systems analysis and designAlthough a computer can be used to carry out the classical transform-inverse transform methods,it is usually more efficient to be find(calculate)the numerical solutions of a differential equation directly,Modem control theory is well suited to the
16、 above trends because its time domain techniques and its mathematical language(matrices,linear vector spaces,etc.)are ideal when dealing with a computer.Computers are a major reason for the existence of state variable methods,With the development of very large scale integrated circuits(VLSI),the cos
17、t,size,and reliability of microcomputers have made it possible to use them routinely in many systemsComputers are now so commonly used as just another component in the control system,Most classical control techniques were developed for linear constant coefficient system with one input and one output
18、(perhaps a few inputs and outputs).The language of classical techniques is the Laplace or z-transform and transfer functionsWhen nonlinearities and time variations are present,the very basis for these classical techniques is removed.Some successful techniques such as phase-plane methods,describing f
19、unctions,and other ad hoc methods,have been developed to alleviate this shortcoming.However,the greatest success has been limited to low-order systems.The state variable approach of modern control theory provides a uniform and powerful method of representing systems of arbitrary order,linear or nonl
20、inear,with time-varying or constant coefficientsIt provides an ideal formulation for computer implementation and is responsible for much of the progress in optimization theory.,The Concept of State,The concept of state occupies a central position in modern control theoryHowever,it appears in many ot
21、her technical and nontechnical contexts as well.In thermodynamics the equations of state are prominently used.Binary sequential networks are normally analyzed in terms of their states.In everyday 1ife,monthly financial statements are commonplace.The Presidents State of the Union message is another f
22、amiliar example,In all of these examples the concept of state is essentially the same.It is a complete summary of the status of the system at a particular point in timeKnowledge of the state at some initial time t0,plus knowledge of the system inputs after t0,allows the determination of the state at
23、 a later time tl.As far as the state at tl is concerned,it makes no difference how the initial state was attained.Thus the state at t0 constitutes a complete history of the system behavior prior to t0,insofar as that history affects future behavior.Knowledge of the present state allows a sharp separ
24、ation between the past and the future.,At any fixed time the state of a system can be described by the values of a set of variables xi,called state variables.One of the state variables of a thermodynamic system is temperature and its value can range over the continuum of real numbers RIn a binary ne
25、twork state variables can take on only two discrete values,0 or 1Note that the state of your checking account at the end of the month can be represented by a single number,the balanceThe state of the Union can be represented by such things as gross national product,percent unemployment,the balance o
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