自控控制专业外语一常考的句子和段落.docx

1、自控控制专业外语一常考的句子和段落11 Introduction In the first part of this chapter，after a general introduction The concepts of open-loop and closedloop control are discussed in the context of a water level control system . 本章第一部分，大体的介绍之后在液位控制系统的内容中介绍的开环控制和闭环控制的概念This example is then used to introduce fundamental c

2、onsiderations in control system analysis and design这个例子随后被用作介绍控制系统分析和设计的基本思想 In the second part of the chapter，Laplace transforms are discussed and used to define the transfer function of a systemThis is a linearized model of the dynamic behavior of the system that will serve as the basis for system

3、analysis and design in most of this bookBlock diagram reduction is used to obtain the transfer function of a system consisting of interconnected subsystems.This completes the framework necessary for Chapter in which transfer functions are derived for a variety of physical(sub)systems.本章第二部分，介绍了拉氏变换和

4、用拉氏变换来定义系统的传递函数，这事一个线性化的系统动态特性模型，该模型将在本书的大部分地方作为系统分析和设计的基础，方框图化简是用来获得由相互关联的子系统组成的系统的传函的。这就完成了第二章所需的框架，在第二章中导出了各种物理（子）系统的传递函数。 12 Examples and Classifications of control systems控制系统和分类 Control systems exist in a virtually infinite variety，both in type of application and level of sophistication . 实际上，

5、控制系统无论是在应用种类还是复杂程度上都存在许许多多的形式。The heating system and the water heater in a house,are systems in which only the sign of the difference between desired and actual temperatures is used for controlIf the temperature drops below a set value，a constant heat source is switched on，to be switched off again w

6、hen the temperature rises above a set maximumVariations of such relay or onoff control systems，sometimes quite sophisticated，are very common in practice because of their relatively low cost室内的加热系统和热水箱都仅仅是利用期望温度和实际温度间的偏差信号控制的系统。如果温度降到设定值以下，一个恒定的热源将开启，当温度上升到设定的最高值以上时，关闭恒定热源。有时继电器系统或开关控制系统的变换在实际中非常常见，因

7、为它们相对低廉的价格 In the nature of such control systemsthe controlled variable will oscillate continuously between maximum and minimum limitsFor many applications this control is not sufficiently smooth or accurateIn the power steering of a car，the controlled variable or system output is the angle of the f

8、ront wheelsIt must follow the system input,the angle of the steering wheel，asclosely as possible but at a much higher power level在控制系统的特性中，被控变量将会在上限和下限之间持续振荡。对于一些应用，这个控制系统不够顺畅和精确，在车辆的动力转向中，被控变量或系统输出是方向的角度，它必须尽可能地跟踪系统输入-方向盘角度，但是功率水平更高。(1) Process control OF regulator systems：the controlled variable，o

9、r output，must be held as close as possible to a usually constant desired value, or input, despite any disturbances.过程控制和调节系统：尽管存在干扰，被控变量或叫输出必须尽可能保持在一个希望的常值也就是输入上。This last example brings to mind the distinction between continuous and discrete systemsThe latter are inherent in the use of digital comp

10、uters for control最后的例子使人想起连续系统和离散系统的差别，后者是属于控制数字计算机的使用。 The classification into linear and nonlinear control systems should also be mentioned at this pointAnalysis and design are in general much simplerfor the former,to which most of this book is devotedYet most systems become nonlinear if the varia

11、bles move over wide enough rangesThe importance in practice of linear techniques relies on linearization based on the as sumption that the variables stay close enough to a given operating point基于这一点应该提到线性控制系统和非线性控制系统的分类，前者的分析和设计一般是比较简单的，本书的大部分也致力于此，然而如果变量变化超过足够大的范围，许多系统会变成非线性的。依赖于线性化的线性技术的实际应用的重要性是基

12、于变量与一个给足的工作点保持足够接近的假设。14 Conlrol System Analysis and Design控制系统分析和设计 Control system analysis and desigm can be summarized in terms of the following two questions：控制系统分析和设计可根据如下两个问题来总结 (1)Analysis：What is the performance of a given system in response to changes of inputs or disturbances?分析，给定系统对输入或者干

13、扰变化的响应的性能是什么 (2)Design：If the performance is unsatisfactoryhow can it be improved without changing the process，actuator，and power amplifier blocks?设计，如果性能不满意，怎样在不改变过程，执行器和功率放大器的方框的情况下来改善它 It is particularly important to note the constraints imposed on the designer. The blocks indicated generally rep

14、resent relatively，of over，expensive equipment,and must be considered as a fixed part of the system.The power of design techniques that will permit large changes in performance to be achieved by changing only the controller should be appreciated注意施加给设计者的约束是尤其重要的，标出的块一般表示相对或非常贵重的设备，并且必须被认为是系统的固定部分，只通过

15、改变控制器而取得的性能改变的设计技术的作用应该得到重视 The term performance is used to summarize several aspects of the behaviorAssume that in Fig11 a sudden change of input is applied，to a new constant valueA certain period of time will be required for transientresponse terms to decay and for the output to level off at the n

16、ew valueOne key feature of this transient period is that it should be sufficiently shortAnother is that the transient response should not be excessively oscillatory or severely overshoot the final level性能这个术语被用作总结几个方面的行为，对于一个新的定值，假设图1.1中提供一个突然改变的输入，某个时段将需要用于衰减的暂态响应和稳定在一个新值上的输出，该暂态过程的一个关键点是它应该足够短，另一个

17、是暂态响应不应过度地振荡或严重超调最终水平。 The steady-state response，after the transients have decayed，is an equally important aspect of the performanceAny steadystate errors betweenr and c must be satisfactorily smallTo a disturbance input,the output should ideally not respond at all，and in any case the steadystate va

18、lue ofthis output should be acceptably small暂态已经衰减之后，稳态响应是性能的一个同样重要的方面，r与c之间的稳态误差必须足够的小，对于一个干扰输入，输出应该理想的一点也不响应，并且在任何情况下，输出的稳态值应该小到可以接受。 The performance of a design is also measured by its success in reducing the dynamic and steadystate effects of parameter variations in the plant onthe output一个设计的性能

19、也可以通过它成功地减小动态和稳态的对对象输出参数变化的作用来衡量。 Disturbances and parameter variations were given as motivations for feedback controlHowever，the transient response and steady-state error characteristics can also be improved by the use of feedbackand the motivations for feedback can be listed as follows： 干扰和参数变化被认为

20、是使用反馈控制的原因，然而通过使用反馈暂态响应与稳态误差同样能被改善，并且使用反馈的原因列出如下 (1)Reducing the effects of parameter variations减少参数变化的影响 (2)Reducing the effects of disturbance inputs减少干扰输入的影响 (3)Improving transient response characteristics改善暂态响应特性 (4)Reducing steadystate errors减少稳态误差 In fact，improvements in the first two items ar

21、e usually achieved in the course of design procedures aimed at the last two事实上，在以后两条为目标的设计过程中通常实现了前两条的改善。 0n the other handthese faster changes of output intuitively suggest increasing danger of severe overshoot and oscillations of the output following asudden change of the inputWe can show the larg

22、e effect on the response to a step change of r which can easily result if the gain is increased from a rather low to a rather high valueIn fact，with a further increase of gain the oscillations may grow instead of decayThe system is then unstable另一方面，随着输入的突然改变，这些输出的快速改变直接表明增加了输出的严重超调和振荡的危险，我们可以看出如果增益

23、从一个很小的值增加到很大，那么一个很容易实现的r的阶跃改变都会对响应有很大作用，事实上，随着增益的大大增加，振荡可能会增加而不是衰减，系统随之会很不稳定。 Stability is always the primary concern in feedback control designBut to be useful a system must also possess adequate relative stability；that is，the overshoot of a step response must be acceptably small，and this response

24、must not be unduly oscillatory during the transient period在反馈控制设计中，稳定性总是首先要考虑的，但是想成为一个有用的系统必须拥有足够的相对稳定性，也就是说，阶跃响应的超调必须足够的小，并且这个响应应该在暂态过程中一定不能超过过渡的振荡。 Relative stability considerations usually impose an upper limit on gain，and hence on accuracy and speed of response Much of control system design call

25、 be summarized as being concerned with achieving a satisfactory compromise behveen these featuresIf this is not possible with only a gain K，controller complexity is increased相对稳定性的考虑，通常使增益有一个上限，从而使精确度和响应速度也有上限，大多数的控制系统设计可以总结为考虑在这些特点中获得一个满足的折中，如果仅有一个增益K，不可能实现，控制器的复杂程度就增加了。 The remainder of this chapt

26、er provides a basis for the tools needed to move beyond this intuitive discussion and to answer the questions it raises.本章的剩余部分为超出直觉的讨论所需的工具提供一个基础并且回等它所提出的问题。 1.7 The assumption of zero initial conditions is very common in system analysis and designIt is natural for linearized equations，in which the

27、 vailables are rariations about operating point valuesFurthermorefor linear systems the nature of the transient response is independent of the initial conditions：that is，whether or not the response is oscillatory，and if it is，whether the oscillations decay sufficiently fastThis is the type of inform

28、ation usually of most interest to the designerAt the same time，it is well to point out that the assumption of zero initial conditions in the definition ofG(s) is not a constraintFor linear systems the principle of superposition applies,which means that the total response is the sum of those to the i

29、nput and to the initial conditions applied separatelyThus the initial conditions can be set to zero in determining the response to input r(t)，and r(t)set to zero when calculating the response to initial conditions19 Conclusion In this chapter a general introduction has been given first，including phy

30、sical discussion of some fundamental features of control system behaviorA level control example led to a common block diagram configuration本章首先做了一个概述，包括控制系统特性的一些基本特点的物理讨论，用一个液位控制的例子导出了一个常见的方框图结构。 Laplace transforms led to the transfer function description of dynamic behaviorand block diagram reducti

31、on to the description of an interconnected system of blocks用拉氏变换推导出了描述动态特性的传函，用方框图化简的方法导出了模块的互联系统的描述。 The application of transfer functions and transforms to calculation of the response c(t)to an input r(t)and initial conditions has been demonstrated for cases where the roots of the denominator of t

32、he transform C(s) are real and distinct在拉氏变换分母的根C(s)是互异实根的情况下，证明了可以应用传函和拉氏变换去计算对输入r(t)和初始条件的响应c（t） This provides a framework and motivation for study of the next chapter,and a basis for detailed discussion of transient response in Chapter 3It also allows for an introductory examination of some of the effects of feedback in the problems below这就为研究下一章的学习提供了一个框架和动机，也为第三章中详细讨论暂态响应提供了基础，同时也为以下将要介绍的反馈的作用提供了引导检测21 IntroductionSuch systemin which all system equations and the block diagram are derived directly,are discussed in Chapter 4