机电工程专业英语 朱晓玲 Lesson 16新.pptVIP

Lesson 16 Automatic Control System Section I Words and Phrases Section II Text and Translation Section III Exercises and Answers Section I Words and Phases variable [5vZEriEbl]n.[数]变数, 可变物, 变量adj.可变的, 不定的, 易变的, [数]变量的 manipulate [mE5nipjuleit] vt.(熟练地)操作, 使用(机器等), 操纵(人或市价、市场) vt.(熟练地)操作,巧妙地处理 transmitter [trAnz5mitE]n.转送者,传导物, 发报机, 话筒, 发射机 tank [tANk]n.(盛液体, 气体的大容器)桶、箱、罐、槽, 池塘, 坦克, 战车, 柜, 储水池 Section I Words and Phases deviation [7di:vi5eiFEn]n.背离,偏离 feedback [5fi:dbAk]n.[无]回授, 反馈, 反应 external signal[自]外部信号 disturbance [dis5tE:bEns]n.骚动,扰动, 骚乱 stability [stE5biliti]n.稳定性 consequently [5kRnsIkwEntlI]adv.从而, 因此 oscillation [7Csi5leiFEn]n.摆动, 振动 Section II Text An automatic control system1 is a preset closed-loop control2 system. An automatic control system has two process variables ass-ociated with it: ?a controlled variable and a manipulated variable. A? controlled variable3?is the process variable that is maintained at a specified value or within a specified range. In the previous example （the water tank level control system）, the storage tank level is the controlled variable. A manipulated variable4 is the process variable that is acted on by the control system to maintain the controlled vari-able at the specified value or within the specified range. For the pre-vious example, the flow rate of the water supplied to the tank is the manipulated variable. Functions of Automatic Control In any automatic control system, the four basic functions that occur are: Measurement ，Comparison， Computation, Correction. In the water tank level control system in the example above, the lev-el transmitter measures the level within the tank. The level transmitt-er sends a signal representing the tank level to the level control dev-ice, where it is compared to a desired tank level. The level control device then computes how far to open the supply valve to correct Section II Text any difference between actual and