自控控制专业外语一，常考的句子和段落

1．1 Introduction

In the first part of this chapter，after a general introduction． The concepts of open-loop and closed—loop 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 considerations 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 system．This is a linearized model of the dynamic behavior of the system that will serve as the basis for system analysis and design in most of this book．Block 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。

1．2 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，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 control．If the temperature drops below a set value，a constant heat source is switched on，to be switched off again when the temperature rises above a set maximum．Variations of such relay or on—off 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，因为它们相对低廉的价格

In the nature of such control systems．the controlled variable will oscillate continuously between maximum

and minimum limits．For many applications this control is not sufficiently smooth or accurate．In the power steering of a car，the controlled variable or system output is the angle of the front wheels．It must follow the system input,the angle of the steering wheel，as closely 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，or 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 systems．The latter are inherent in the use of digital computers 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 point．Analysis and design are in general much simpler

for the former,to which most of this book is devoted．Yet most systems become nonlinear if the variables move over wide enough ranges．The 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于变量与一个给足的工作点保持足够接近的假设。

1．4 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扰变化的响应的性能是什么 (2)Design

：

If

the

performance

is

unsatisfactory．how 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 represent 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 behavior．Assume that in Fig．1．1 a sudden change of input is applied，to a new constant value．A certain period of time will be required for transient response terms to decay and for the output to level off at the new value．One key feature of this transient period is that it should be sufficiently short．Another

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 performance．Any steady—state errors between r and c must be satisfactorily small．To a disturbance input,the output should ideally not respond at all，and in any case the steady—state value of

this 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 steady—state effects of parameter variations in the plant on the output．一个设计的性能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 control．However，the transient

response

and

steady-state

error

characteristics can also be improved by the use of feedback．and the motivations for feedback can be listed as follows： 干扰和参数变化被认为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 steady—state errors．减少稳态误差 In fact，improvements in the first two items are 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 hand．these faster changes of output intuitively suggest increasing danger of severe overshoot and oscillations of the output following a

sudden change of the input．We can show the large 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 value．In fact，with a further increase of gain the oscillations may grow instead of decay．The 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 design．But 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 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 be summarized as being concerned with achieving a satisfactory compromise behveen these features．If 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 chapter 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 design．It is natural for linearized equations，in which the vailables are rariations

about

operating

point

values．Furthermore．for 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 fast．This is the type of information usually of most interest to the designer．At the same time，it is well to point out that the assumption of zero initial conditions in the definition of G(s) is not a constraint．For linear systems the principle of superposition applies,which means that the total response is the sum of those to the input and to the initial conditions applied separately．Thus 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 conditions． 1．9 Conclusion

In this chapter a general introduction has been given first，including physical discussion of some fundamental features of control system behavior． A 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 behavior．and block diagram reduction 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 the 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 3．It 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

2．1 Introduction

Such system．in which all system equations and the block diagram are derived directly,are discussed in Chapter 4．Frequently，the precise nature of the feedback may be evident only from this block diagram．

It is useful to note that a model should not be expected to be evident“by inspection．”Rathel,it usually will emerge gradually from equations written for parts of the systern．

2．8 Conclusion

In this chapter transfer functions were derived for a variety of physical subsystem blocks．If feedback systems consist of 8 connection of such blocks,overall transfer functions can now be obtained by block diagram reduction．But often such a separation into blocks and the precise nature of the feedback may become evident only when all equations for the system have been written．

3．1 Introduction

In this chapter the transient behavior of systems described by given transfer functions is considered，whether these describe a single block or have been obtained by block diagram reduction．The purpose is to establish correlations and to specify requirements that ensure satisfactory performance． The use of feedback to satisfy such requirements will be considered later．在这一章中考虑由给定传函描述系

统的暂态特性，是那些描述单个方框或由方框图化简得到的方框，目的是建立联系和说明确保满意的性能的要求，随后将考虑使用满足这些要求的反馈。

The correlations between transfer functions and response characteristics are developed in terms of the positions of the system poles and zeros in the s—plane．These are powerful concepts which will also be used in the design of feedback to improve unsatisfactory behavior．根据S平面中系统极点和系统零点的位置来推导传函和响应特点间的关系，这些是有用的，将被用于反馈的设计中来，改善令人不满意的性能的概念。

Inverse transformation of C(s)=G(s)R(s)was used in Section l．7 to find the response c(t)to an input，r(t)，for the case where the roots of the denominator of C(s)are real and distinct．The cases of repeated roots and complex conjugate pairs will now also be considered,and the s—plane will provide the basis for a graphical alternative to the analytical method of calculating the residues．This alternative enhances insight and is ofen preferred for more complicated transforms．为得到关于输入r(t)的响应c(t)

在1.7节中用到了C（s）=G(s)R(s)的逆变换（对于c(s)的分母，根是互异实根的情况）现在也将考虑重根和复共轭的情况，S平面将提供对于分析计算留数方法的图形替代品的基础。

Stability稳定性

If—1／T is positive，the pole lies in the right half of the s一plane．The transient e一t/T then grows instead of decays as t increases．The system is unstable and useless．Hence the most important role for design：如果-1/T是正的，极点就位于S平面的右半部分，随t的增加，暂态e一t/T随后会发散，而不是衰减，系统是不稳定的，没有用的，因此，设计的最重要的规则

For system stabihty，be system pole(s)must lie in the left half of the s-place．为了系统稳定性，系统极点一定位于S平面的左半部分

Speed of response响应速度

To speed up the response of the system(i．e．，to reduce its time constant T)，be pole一1／T must be moved left．为了加速系统响应（例如减少它的时间常数T），极点-1/T必须向左移动

How such movement is to be achieved is a problem of design，considered later．Example 2．8．1 and comparison

of Examples 3．2．1 and 3．3．2 suggest，however，the use of feedback around the simple lag plant，together with an adjustable gain．如何移动，成为了一个设计问题，随后考虑它，例2.8.1和例3.3.2和例3.2.1的比较表明，对于纯惯性环节应用反馈并且施加一个适合的增益

3.6 Nature of the Transient Response and Dominating Poles暂态响应的主导极点的特性

Whatever the order of the transfer function，it may be stated form the preceding sections and(3．19)that，since each real pole causes a decaying exponential transient and each complex pair a decaying oscillation：由于每个实极点造成指数衰减暂态，每个复对造成的减幅振荡，无论传函的阶次是几，它可能都会保持前面部分（3.19中的形式）

The total transient response is a superposition of exponential decays and decaying oscillations．

Repeated roots do not change this in an essential way．If all parameters are known,the response can be calculated．but its nature can also be judged without this by inspection of the pole positions．During design the parameters are not known and the aim is to

use feedback which locates the poles in regions corresponding to satisfactory dynamics，that is，not too close to the imaginary axis and at a small enough angle to the negative real axis．

The dominating—poles concept is very important in this connection and simplifies design greatly．The response of many systems is dominated by one pair of complex poles relatively close to the imaginary axis，Design can therefore concentrate on locating this dominating pair satisfactorily.The fact that many systems behave approximately as second—order systems is also the reason the performance criteria for second —order systems discussed in Section 3．5 apply to higher-order systems as well．

Absolute and Relative Stability相对稳定性和绝对稳定性

The foregoing relative stability conditions on the locations of the dominating poles are much more stringent than those of absolute stability．Absolute stability requires only that all roots of the system characteristic equation(i．e．，the poles of its transfer function)lie in the left·half s一plane．It is known

that if any of the coefficients are zero or if not all coefficients have the same sign,there will be roots on or to the right of the imaginary axis．If all coefficients are present and have the same sign，which can be taken to be positive without loss of generality，the Routh·Hurwitz criterion discussed in the next section provides a quick method for determining absolute，but not relative,stability from the coefficients．without calculating the roots．先前在配置主导极点中讲的相对稳定性条件比绝对稳定性的条件严格，绝对稳定性只要求所有特征方程的根位于左半S平面，我们已经知道如果任何一个系数为0或者不是所有系数的符号都相同，那么将出现在虚轴上或在虚轴的右边，假如所有的系数都存在并且同号（不失一般性可以看成均为正），则下一节讨论的Routh-Hurwitz判据提供了一个无需计算根而由系数决定绝对稳定（不是相对稳定）的快速方法。

3．9 Condusion

In this chapter the dynamic response characteristics corresponding to given transfer functions have been studied．The features of the response have been interpreted in terms of the locations of system poles and zeros in the s—plane．这

一章研究了对应给定传函的动态响应特性，根据S平面上系统极点和零点的位置说明了响应的特点。

Note，however．that except in the examples little attention has been given to feedback,and how it may be used to modity performance．Also，transient response calculations and stability determination，except by the Routh-Hurwitz criterion，of feedback systems with higher—order characteristic polynomials still requires discussion of techniques for finding their roots，the system poles．This is considered in Chapter 6，after study of the modeling,the performance，and the dynamic compensation of feedback systems．然而，注意在这个例子中除了关注反馈较少外，怎样用它来改进性能，而且，除了通过劳斯判据，具有高阶特性多项式的反馈系统的暂态响应计算和稳定性判据，仍需求根和系统的极点的技术讨论，在研究了反馈系统的建模，性能和动态补偿以后，第六章中会考虑这个

4．1 Introduction引言

The first part of this chapter is concerned with the modeling of feedback system and the second with the motivations for the use of feedback and its effect on

performance．The effect of changes of gain in the feedback loop on performance and its limitations,are considered and will motivate the discussion of dynamic system compensation in Chapter 5．本章第一部分与反馈系统建模有关，第二部分与使用反馈的动机和反馈系统对性能的影响有关，会考虑在反馈回路中增益的改变对性能的影响和它的限制，还将考虑第五章讨论动态系统补偿的动机

As suggested earlier，the block diagram structure of a system may be more or less immediately evident from the system schematic diagram or the nature and even the existence of feedback may be rather difficult to see by inspection．In the latter case in particular,the derivation of a“good’’block diagram,which clearly identifies the feedback，is an important aid in system analysis and design．Both types are considered through examples，beginning with the first．正如前面表明的，系统的方框图结构可能或多或少立刻变得明显，或系统的性质甚至是反馈的存在可能是困难的通过直接检查，尤其在后一种情况下，导出一个好的能清晰表明反馈的方框图，在系统分析和设计中是一个重要的辅助，通过例子来考虑两种类型，从第一个开始

4．4 Effect of Feedback on Parameter Sensitivity and

Disturbance Response反馈对参数灵敏度和干扰响应的影响

The motivations for the use of feedback were listed in Section 1．4：1.4节列出了使用反馈的原因

(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提高暂态响应 (4)Reducing steady—state errors减少稳态误差 The first two are the prime reasons why feedback is needed．and are discussed first．需要反馈的主要原因是前两个，并且首先讨论它们

Sensitivity to Parameter Variations参数变化的灵敏度 Consider the standard feedback loop in Fig．4．4．G is the transfer function of the plant or process to be controlled，Gc is that of a controller which may be just a gain or dynamic as discussed in Chapter 5，and H may represent the feedback sensor．The plant model G is usually an approximation to the actual dynamic behavior，and even then the parameter values in the model are often not precisely known and may also vary

widely with operating conditions．An aircraft at low level responds differendy to control surface deflections than at high level．A power plant model linearized about the 30％ of full power operating point has different parameter values than that linearized about the 75％point．For very wide parameter variations，adaptive control schemes，which adjust the controller parameters，may be neeessary．but a prime advantage of feedback is that it can provide a strong reduction of the sensitivity without such change of Gc考虑图4.4中的标准反馈回路G是被控制的对象或过程的传函，Gc是在5章中讨论的可能存在增益或动态的控制器，1.1可能表示反馈传感器，对象模型G通常是一个对于实际的动态行为的近似，甚至模型的参数值通常不能准确的知道，并且也会随着操作条件宽泛的变化。飞行器在低空中对控制表面变形的反应不同于在高空中，一个线性化到大约满功率操作点30%的功率对象模型有不同于线性化到操作点75%的功率对象模型的参数值，对于大范围的参数变化，调节控制器参数自适应的控制计划，可能是必要的，但是反馈的一个主要优点是它能提供一个大的灵敏度并且不需要改变Gc． 4．5 Steady-State Errors in Feedback Systems反馈系统的稳态误差

High loop gains were shown to be advantageous to reduce sensitivity of performance to both parameter variations and disturbance input．They will now prove equally desirable from the point of view of the reduction of steady-state errors in feedback systems．Intuitive reasoning in Section l．4 and several examples already suggested this，and it will now be verified by consideration of the unity,feedback system in Fig．4．6．E=R／(1+G)，and the steady—state error e。can be found directly，without the need for inverse Transformation,by the final value theorem高回路增益被展示出有益于减少对于参数变化和干扰输入两者的性能灵敏度，它们将同样的证明在反馈系统中以减少稳态误差角度来说的期望，1.4节的直观原因和几个例子已经表明了这一点，并且将通过例4.6的单位反馈系统的考虑来证明它。 4．7 Conclusion

In this chapter the modeling of systems with feedback in block diagram form was considered first．The examples include those where the structure of the system and the nature of the feedback are clear from the schematic diagram ,as well as cases where even the existence of feedback may not be obvious．In particular in the latter

case，a good block diagram is an important aid in system analysis and design．本章首先考虑的是方框图有反馈的系统建模，这个例子还包括了那些期中从示意图中可以明显看出系统结构和反馈特性的，也包括反馈的存在性不是明显的情况，尤其在后一种情况中，在系统分析和设计中一个好的方框图是重要的辅助

The motivations for the use of feedback were examined next，and it was found that considerations of relative stability usually limit the gain increase desirable to increase the speed of response and to reduce sensitivity to plant parameter variations，response to disturbances，and errors．接下来研究了使用反馈的动因，并且发现对相对稳定性方面的考虑通常限制了增加增益来提高响应速度，减少对对象参数变化的灵敏度，对干扰的响应速及误差这方面的考虑

Examples were given that motivate the use of dynamic compensation,introduced in Chapter 5，to overcome this limitation．The emphasis in Chapter 5 will be on the use of proportional plus integral plus derivative control(PID)．This form is extremely common in practice，and its basic control actions are fundamental to dynamic compensation generally．第五

章介绍的例子是关于使用动态补偿的原因，它克服了这个限制，比例积分微分控制的是使用将是第五章的重点，在实际中这个形式是很常见的，并且它的基本控制功能通常使动态补偿的基础

The physical realization of such controllers will also provide additional examples of the derivation of block diagrams for systems with feedback．In this context the operational amplifier mentioned in Chapter 2，and some of its applications in controller realization and system simulation，will be discussed as well．一些控制器的物理实现也将提供更多的带反馈的系统方框图推导的例子，在这种情况下，第2章中提到的运算放大器以及它在控制器实现和系统仿真方面的一些应用，也将被讨论

The concept of a root locus was introduced in the examples of Section4．6．The limimtion to second—order systems，for which the loots of the charactefisfic equation can easily be calculated，suggests the need for

more

advanced

techniques

in

practical

applicafiom．The root locus technique in Chapter 6 and the frequency response methods in Chapters 7 and 8 will fullill this need．However．dynamic compensation is

considered first because to enhanee insight，it is important to introduce this subject in simple mathematical framework．在4.6节的例子中介绍了根轨迹的概念，对于那些特征方程的根能够容易的计算出来的二阶系统的限制表明在实际应用中需要更先进的技术，第6章的根轨迹法和第7，8章的频率响应法将满足这个需要，但是，为了增强视野，首先考虑动态补偿，在简单的数学结构中，引入这个问题是重要的

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