测控技术与仪器专业英语 张凤登UNIT-15.Control Approaches

UNIT 15 Control Approaches,15.1 Text PID Controller PID控制,New Words derivative di'rivtiv a. n. 微分，导数；微分的，导数的 acronym 'ækrunim n. 首字母缩写（词） leave li:v v. 离开；省去，不考虑（out） guarantee ,ærn'ti: v. 保证，确保，许诺 accumulation ,kju:mju'lein n. 积累过程，积累 plant pl:nt n. （被控）对象，设备 differentiator ,dif'renieit n. 微分器 saturate 'sætreit v. 使饱和 bandwidth 'bændwid n. 带宽，频带宽度 piecewise 'pis,wais a. 分段的 rationale ,ræ'n:li n. 理由，基本原理 oscillatory 'siltri a. 振动的，摆动的 factor 'fækt n. v. 因子，因素；提出公因子（out）,New Words (continue) dynamics dai'næmiks n. 动态（特性），（动）力学 delay di'lei n. 延迟，滞后 harmonic h:'mnik a. n. 谐波的；谐波频，音 disturbance di'st:bns n. 扰动,Notes One way to look at this term is that the farther away from the desired point we are, the harder we try. 看待这一项的一种方法就是我们离要达到的目标越远，就应更加努力尝试。 As can be seen by this analogy, when we are close to the target, the control essentially does nothing. Thus, if the system drifts a bit from the target, the control does almost nothing to bring it back. 正如我们通过该类比所能见到的，当我们离目标很近的时候，控制器本质上不工作。因此，如果系统稍微偏离目标，则控制器几乎无法使其恢复到原位。 In addition, if the error undergoes a sharp transition, for example, when a step input is applied, the derivative skyrockets, requiring an unreasonably large control effort. 另外，如果误差信号经历突变，比如输入了一个阶跃信号，则导致微分项会产生突变，需要控制器产生不合理的大的控制作用。 This eliminates spikes in the term Kd·ded(t)/dt, without substantially affecting the overall control performance. 这么做消除了Kd·ded(t)/dt项中的峰值，不会对整个控制器的性能带来实质的影响。,Exercises 1. Answer the following questions. The acronym PID stands for proportional-integral-derivative control. There are 6 variations of PID control equation. They are P, I, D, PI, PD, and PID. if the system drifts a bit from the target, the P control does almost nothing to bring it back. The I term tends to slow the system reactions down. In order to speed up the system response, we add the derivative term. This is because true differentiation is a “wide-band” process, i.e., the gain of this term increases linearly with frequency. Generally, the control signal will saturate all amplifiers etc. It is common for the closed-loop system to track a constant reference input. In this case, the input is called a setpoint. Because it is not particularly good to differentiate step changes in the error signal, changing the configuration will give basically the same behavior, without having to do such things. This eliminates spikes in the term Kd·ded(t)/dt, without substantially affecting the overall control performance. The derivative term is usually beneficial. No, it isnt.,Exercises (continue) 2. Choose the best answer for each of the following sentences. C. accumulation A. the integral time D. derivative C. add the derivative term B. disadvantage C. setpoint C. the highly coupled multi-input, multi-output system B. using,15.2 Reading and Translation Expert Systems 专家系统,New Words fascinate 'fæsineit v. 使着迷，强烈吸引住 viable 'vaibl a. 可行的；有生命力的 clash klæ v. 抵触，冲突 statute 'stætju:t n. 法律，法规 abide 'baid v. 遵循，遵守 blind blaind a. 盲目的,斜体部分参考译文: An expert system uses a compilation of the knowledge of one or more expert persons and through a computer program, performs the decision making as if the expert people were actually performing the tasks. 专家系统通过计算机程序对一个或多个专家的知识进行编辑，然后像专家在场时那样做出决定。 Since programming is the usual way expert systems are created, most of todays expert systems are computer based. Programming languages have been developed to allow easier programming of expert systems. The most accommodating languages provide a syntax and structure which readily adapt to the heuristic rules of decision making. 由于编程是建立专家系统的常用方法，当今大多数专家系统采用计算机。为使专家系统编程更容易，人们已经开发出来一些编程语言。大多数适用的语言所提供的语法和结构，适合于决策制定的启发式规则。 The more an expert system can handle a scenario which would be cumbersome and difficult for a person to handle, the more critical that system is to enable the task to be performed better. 一个专家系统掌握的情况越多，对于系统完成好给定的任务越关键，这些情况对于个人来讲可能太繁杂，且难以掌握。,15.3 Further Reading Optimal Control 最优控制,New Words constraint kn'streint n. 约束，约束条件 index 'indeks n. 指标 deterministic di,t:mi'nistik a. 确定的 lumped lmp a. 集中的 admissible d'misbl a. 可采纳的，允许的 trajectory 'trædiktri n. 轨迹，弹道 suboptimal sb'ptiml a. 次优的,Notes mathematically that is. 数学上是如此的。 dynamic programming 动态规划 calculus of variations 变分法,15.4 General Knowledge 英文产品说明书 产品说明书是厂商为销售其产品而附的一种宣传小册子，用来告诫客户如何正确使用所购物品，以免因使用不当或保管不妥而造成不良后果。一份成功有效的说明书，不仅可以激起人们的购买欲望，而且可以起到良好的宣传广告作用。 产品说明书主要介绍某产品的各种情况，诸如其组成材料、性能、存贮方式、注意事项、主要用途等。如机械仪表说明书（Directions for Mechanical Products & Instruments)、电视机说明书（Directions for TV Set）、药品说明书（Directions for Medicine Administration）。,1. 产品说明书的结构 产品的性能、用途不同，其英语说明书的结构（structure of instruction）也会存在差异。一般地，产品说明书由标题（包括副标题）和正文两大部分组成。有的说明书在最后还附注厂商的名称。 说明书标题（headline）。一般来说，说明书的标题不是很重要。因为对一位客户来说，买了何种产品，即使是说明书无标题，他也会认真地阅读正文。这就是为什么某些英文说明书没有标题的原因。当然，这不等于说说明书的标题不重要。因为从宣传效果上看，说明书标题的作用仍很重要，它在说明中起着引导的作用。 说明书标题从不同角度宣传说明书内容，一般分成两种： 直接性标题(direct headline): 直接指出是对哪种产品的说明或是哪种产品的使用手册。