机电技术专业英语 教学课件 作者 徐起贺 张庆良pata b lesson Twenty two.pptVIP

* 机电技术专业英语 Lesson Twenty-two Text Automatic control systems are divided into two classes, open and closed. In the open system, the output of the process has no effect upon the input to the process. In the closed system, the energy input to the system is some function of the output itself. This effect is commonly termed feedback hence the system is a feedback control system, a closed system does not exist, if the closed ring is broken anywhere. Open systems are generally unsuitable for most process control systems, because the output of the system is not a function of itself. The closed system is used in every completely automatic control application. Automatic Control Systems Lesson Twenty-two It is the result of the working people’s boundless creative power that we have automatic controls today1. Automatic controllers have performed great functions in industry. They have made it possible to produce a more uniform quality of product. Because they are on the job 100 percent of the time, whereas a human operator finds it necessary to take rest and finds it difficult to remain alert on repetitious jobs. Therefore, with the development of industry we have replaced human operators with automatic devices in many industrial processes. The workers and technicians of our country have designed and made various automatic devices, which have made it possible to increase production, to reduce production costs and to secure the safety of operating workers2. Furthermore, with the wide-spread application of automatic controllers, more and more workers are free from routine operations and they can concentrate on production in breadth and depth. Lesson Twenty-two New Words and Expressions Lesson Twenty-two Lesson Twenty-two Notes 1. It’s the result of the working people’s boundless creative power that we have automatic controls today. 今天的自动控制是劳动人民无限创造力的体现。 这是主从复合句，that 引导的是主语从句。 2. The workers and technicians of our country have designed and ma