测控技术与仪器专业英语 张凤登UNIT-14.System Analysis

1、UNIT 14 System Analysis,14.1 Text Time-Domain Analysis 时域分析,New Words sinusoidal sainsidl a. 正弦的 abscissa bsis n. 横坐标 ramp rmp n. 斜坡 parabolic ,prblik a. 抛物线形的 infer inf: v. 推断理，论，知，推导（出）,Notes fall into 自然地分作 From this standpoint the system time-domain analysis is well justified. 从这个观点来看，对系统进行时域分析是很合理的 This is important, as the time-domain analysis of systems higher than second order become rather involved. 这一点是重要的，因为高于二阶的系统的时域分析相当复杂。,Exercises 1. Answer the following questions. The response is

2、 a term generally used to describe the output of a system for a given input. There are two categories of responses. They are the time-domain response and the frequency-domain response. The step response of a system is broken down into two parts: the transient and steady-state portions. In the ramp response of the second-order system, its steady-state portion increases with time in ramplike fashion, while the difference between the input and the output remains constant. Since we are dealing with

3、linear systems, any combination of the standard inputs must result in a combination of corresponding responses at the output of the system. We can obtain the order from the differential equations that represent the system. Depending on the location of their poles in the s plane, these systems can often be approximated by a first-order or second-order system. The system speed is inferred from the transient component. This classification indicates the number of integrations contained in the forwar

4、d-path transfer function of the system and is very useful in predicting the system steady-state error for a given input. The values of poles can be adjusted by changing the system parameter values.,Exercises (continue) 2. Replace the underlined parts in the following sentences with words or phrases from the text that best keep the original meanings. The step response of a system is divided into two major portions. (broken down) We learned that the time response of a control system is usually dif

5、ficult to determine analytically, especially for complicated systems. (complex) It is of considerable practical importance to be able to forecast whether a given system is stable or not. (predict) In most actual systems, we are faced with the necessity of experimentally deducing some important physical parameters such as heat transfer coefficient (传热系数), chemical reaction rate, damping factor (阻尼系数), and so on. (practical) In practice, the performance of control system is measured more realistic

6、ally by its time-domain features. (characteristics) The performance of most control systems is extracted from the time response due to certain test signals. (is inferred from),14.2 Reading and Translation Nyquists Stability Criterion 奈奎斯特稳定性判据,New Words vitally vaitlli ad. 极其，极为 vivid vivid a. 生动的，形象的 logarithmic ,lrimik a. 对数的 margin m:din n. 裕量,斜体部分参考译文: Furthermore, the form of the Nyquist locus gave an immediate and vivid indication of how an unstable, or poorly damped, systems feedback perf

7、ormance could be improved by modifying its open-loop gain versus frequency behavior in an appropriate way. 进一步讲，奈奎斯特根轨迹图对于一种不稳定的或低阻尼的系统给出了直接和形象的说明，以适当的方式改变开环增益与频率的特性，可以改善系统的反馈性能。 It was a natural inference from the developments presented in his paper that the closeness of approach of the Nyquist locus to the critical point in the complex plane gave a measure of closed-loop damping. Thus, it soon became clear that the key to making an unstable feedback system stable lay in an appropriate modifica

8、tion of the amplitude and phase characteristics of the open-loop gain function for the feedback loop involved. 奈奎斯特轨迹趋于复平面上临界点的程度给出了闭环阻尼的量度, 这是他文章中发表的新论点的自然推论。因此, 它很快变得清晰，使不稳定反馈系统稳定的关键在于适当调整包含在闭环中开环增益函数的幅频和相频特性。 He introduced logarithmic units of amplitude gain and logarithmic scales of frequency, and hence the logarithmic gain and liner phase versus logarithmic frequency diagrams. 他引入了幅度增益的对数单位和频率的对数坐标，因此得到对数增益、线性相位相对于对数频率的图。,14.3 Further Reading Analysis of Control System in State Space 控制系统的状

9、态空间分析,New Words resort riz:t v. 求助 scalar skeil n. a. 标量（的），纯量（的） diagonal dainl a. 对角的 canonical knnikl a. 标准的；规范的 denominator dinmineit n. 分母 polynomial ,plinumil a. 多项式的 eigenvalue ain,vlju: n. 特征值,Notes state-space approach 状态空间法 state variable 状态变量 multiple-input-multiple-output 多输入多输出 transfer-function 传递函数 controllable, observable, diagonal, or Jordan canonical form. 可控、可观测、对角或约当标准型 distinct roots 非重根 characteristic equation 特征方程,14.4 General Knowledge 英文通知和便笺 通知(announcement)和便笺（short note）这两种文体的共同特征是简短且标题单一。它们的写作要求是表达准确、条理清晰、醒目易读等。,1. 通知 通知一般公布即将发生或已经发生之事，如召开学术报告会，举办晚会，宣布举行各种比赛，放映电影或录像等。通知的格式可参照书信或备忘录，一般情况下，至少应包含以下几部分内容： 时间； 地点； 活动； 其它信息。这里所说的其它信息是指前三部分之外的细节，如学术报告会的演讲者介绍，活动组织者等。 【例1】 Lecture on Fieldbus By Prof. Peter Goehner RM 317 of Center Building Saturday, 24th September 1:30-3:00 All welcome!,英文通知和便笺（续）,2. 便笺 便笺（便条）是一种简短信函，大多是临时性的询问、留言、通知、要求等，往往只有一两句话。它的形式比一般书信简单，多使

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