現(xiàn)代控制理論簡述畢業(yè)論文外文翻譯.doc

1、.Introduction to Modern Control TheoryWhen differential equations are encountered, they are linearized and subjected to whatever constraints are necessary to establish useful input-output relationships. A recognition of the applicability of well-known methods in other fields of knowledge. Optimal co

2、ntrol theory often dictates that nonlinear time varying control law be used, even if the basic system is linear and time-invariant. When nonlinearities and time variation are present, the very basis for classical techniques is removed. Some successful techniques such as phase-plane, describing funct

3、ion, and ad hoc methods, have been developed to alleviate this shortcoming .With an advancing technological society, there is a trend towards more ambitious goals. This also means dealing with complex system with a larger number of interesting components. The need for greater accuracy and efficiency

4、 has changed the emphasis on control system performance. The 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 operation. Optimization of these criteria makes

5、 it even more difficult to avoid dealing with unpleasant nonlinearities. Optimal control theory often dictates that nonlinear time varying control law be used, even if the basic system is linear and time-invariantThe concept of state occupies a central position in modern control theory. However, it

6、appear in many other technical and non-technical context as well. In thermodynamics the equations of state are prominently used. Binary sequential networks are normally analyzed in term of their state. In everyday life, monthly financial statements are commonplace. The President state of the Union m

7、eesage is another familiar 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 time. Knowledge of the state at some initial time t0 plus knowledge of the system inputs after t0, allows the determ

8、ination of the state at a later time t1. As far as the state at t1 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 presen

9、t state allows a sharp separation 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 arrange over the continuum o

10、f real number. In a binary network state variable can take on only two discrete values, 0 or 1. Note that the state of your cheking account at the end of the month can be represented by single number, the balance. The state of the Union can be represented by such things as gross national product, pe

11、rcent unemployment, the balance of trade deficit, ect. For the systems considered in this article the state variables may take on any scalar value, real or complex. That is . Although some systems require an infinite number of state variables, only system which can be described by a finite number n

12、of state variables will be considered here. Then the state can be represented by an n component state vector It belongs to an n- dimensional vector space defined over the field C.For Continuous-time system, the state is defined for all time in some interval, for example, a continually varying temper

13、ature or voltage. Discrete-time system have their state defined only at discrete times, as with the monthly financial statement or the annual State of the Union message. Continuous-time and discrete-time systems can be discussed simultaneously by defining the times of interest as T. For continuous-t

14、ime system T consists of the set of times . In either case the initial time could be and the final time could be in some circumstance The state vector x(t) is defined only for those . At any given t, it is simply an ordered set of n numbers. However, the character of a system could change with time,

15、 causing the number of required state variables (and not just the values) to change. If the dimension of the state space varies with time, the notation could be used. It is assumed here that is the same n-dimensional state space at all. 現(xiàn)代控制理論簡述當(dāng)使用微分方程時，要對其進(jìn)行線性化并受限于一定的約束條件才能建立有用的輸入-輸出關(guān)系。認(rèn)識到其他領(lǐng)域的一些有名

16、的方法的適用性。即使系統(tǒng)是線性定常的，最優(yōu)控制理論通常給出非線性時變控制律。當(dāng)系統(tǒng)存在非線性和時變特性時，經(jīng)典方法賴以存在的基礎(chǔ)就不存在了。一些成功的方法，如相平面法、描述函數(shù)法以及一些特定的方法可以改進(jìn)經(jīng)典控制理論。隨著社會技術(shù)的進(jìn)步，人們總是選擇更高的目標(biāo)。這就意味著要處理復(fù)雜的具有更多相互作用的部件的系統(tǒng)。由于需要更高的精度和效率控制系統(tǒng)的性能指標(biāo)已經(jīng)發(fā)生變化。經(jīng)典的指標(biāo)如超調(diào)量、調(diào)節(jié)時間、帶寬等已經(jīng)讓位于最優(yōu)化指標(biāo)如最小能量、最小成本已經(jīng)最小時間等。即使系統(tǒng)是線性定常的，最優(yōu)控制理論通常給出非線性時變控制律。狀態(tài)的概念在現(xiàn)代控制理論中占據(jù)中心位置。然而其也出現(xiàn)在其他技術(shù)和非技術(shù)領(lǐng)域。在

17、熱力學(xué)中狀態(tài)方程的概念被突出地使用。二進(jìn)制序列網(wǎng)絡(luò)通常使用狀態(tài)的術(shù)語進(jìn)行分析。在日常生活中每月的也使用財政（財務(wù)）狀況。美國總統(tǒng)的國情咨文也是一個熟悉的例子。在上述所有的例子中，“狀態(tài)”的概念是基本相同的。“狀態(tài)”完全就是系統(tǒng)在某個特殊時刻的“狀況”的一個總結(jié)。狀態(tài)在某個時刻t0的值再加上t0時刻的輸入的知識可以確定以后時刻t1的狀態(tài)。就t1時刻的狀態(tài)而言，它與初始狀態(tài)是如何實現(xiàn)的無關(guān)。因此，t0時刻的狀態(tài)就構(gòu)成了t0以前行為的歷史，這個歷史狀態(tài)在一定程度上影響系統(tǒng)未來的行為。當(dāng)前狀態(tài)就將過去與未來作了一個截然的劃分。在任何一個固定的時刻，系統(tǒng)的狀態(tài)可以用變量集合的值xi來描述，稱為狀態(tài)變量。熱力學(xué)系統(tǒng)的一個狀態(tài)變量是溫度，其值是在一個實數(shù)連續(xù)區(qū)間R變化。對于一個二進(jìn)制網(wǎng)絡(luò)狀態(tài)變量可以僅僅有兩個離散的值，0和1。你在月底帳目的平衡的狀態(tài)可以用一個數(shù)來表示。國情咨文中的狀態(tài)可以用國民生產(chǎn)總值、失業(yè)率、貿(mào)易赤字等來表示。對于本文所考慮的系統(tǒng)，狀態(tài)變量可以用任何一個標(biāo)量值（實數(shù)或復(fù)數(shù)）來表示。即。雖然有的系統(tǒng)需要用無窮多個狀態(tài)變量來表示，但是在這里我們僅僅考慮有限個數(shù)目狀態(tài)變量的系統(tǒng)。因此，狀態(tài)可以表示為n個分量的狀態(tài)向量。狀態(tài)向量屬于某個域C上的狀態(tài)空間。對于連續(xù)時間系統(tǒng)，狀態(tài)可以定義某個區(qū)間上