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1、UNIT 9 Manipulative Devices,9.1 Text Final Control Elements 终端控制单元,New Words solenoid sulnid n. 电磁线圈，螺线管，电磁阀 pneumatic nju:mtik a. 气动的 hydraulic haidr:lik a. 液动的，液压的 tub tb n. 桶 rinse rins v. 漂洗，漂净 blower blu n. 鼓风机，吹风机 cereal siril a. n. 谷物的；谷物 pellet pelit n. 颗粒，粉末 throttling rtli n. 节流调节 detrimen
2、tal ,detrimentl a. 不利的，有害的 globe lub n. v. 球形，球体；使成球形 pinch pint n. 收缩，夹紧 butterfly btflai a. n. 蝶形的；蝴蝶 flange flnd n. v. 法兰，凸缘；（在上）安装法兰凸缘 thread red v. n. 拧螺丝，上螺母；线（状物），螺纹,Notes be prone to 倾向于,Exercises 1. Answer the following questions. A interface between a controller and the process it controls
3、. Various types of switching elements， actuators， control valves， heaters， and electric motors are essential components. The switching action may be accomplished mechanically by an actuator， electromechanically by a solenoid， electronically by a solid-state device. Stepper motors and servomotors pro
4、vide the “muscle” for robotic arms. Process requirements， correct valve sizing， suitable flow characteristics of the valve， fail-safe mode， proper choice of valve body type， and correct installation should be considered. They are globe (including three-way and angle)， gate， diaphragm， and pinch. Hyd
5、raulic actuators are used where slow， precise positioning is required， or where heavy loads must be moved. Hydraulic actuators operate at higher pressure than pneumatic actuators， so they can provide larger forces from a given-size cylinder or motor. Pneumatic actuators are used where lighter loads
6、are encountered， where an air supply is available， and where fast response is required. Pneumatic actuators are less expensive than hydraulic actuators， and they are capable of much faster movement. The speed of a hydraulic actuator is limited by the maximum flow rate provided by the hydraulic pump.
7、,Exercises (continue) 2. According to the text, fill in the blanks with suitable words or phrases given below in the correct form. turn electromechanically electronically heat severe hydraulic electromechanically (2) electronically (3) turn (4) heating (5) severest (6) hydraulic,9.2 Reading and Tran
8、slation Speed Control 电机速度控制,New Words SCR abbr. 可控硅整流器（silicon controlled rectifier） inverter inv:t n. 反向器；换流器 furnace f:nis n. 炉,Notes universal series motors 通用系列电机 residual magnetism 剩磁 back EMF 反向电动势,斜体部分参考译文: In a dc circuit, such as an inverter, pulse width modulation may be accomplished by u
9、sing a constant repetition rate and a variable time delay between the turn-on and the turn-off pulses, which allows an adjustment of the on-time in each cycle. 在直流电路中，采用转换开关，脉冲调宽等线路，它们由不变重复率，可变延迟时间的开关脉冲控制，从而实现每个周期中开启时间的调节。 Often the degree of simplicity of the control circuits is dependent on motor
10、characteristics, and improper motor selection can cause poor circuit operation. 控制电路的简单程度常取决于电机的特性，电机选择不适当将引起电路工作失灵。 A single motor may be used with the variable requirements in different installations being compensated by means of the control. Where the maximum speed of the motor is set by the cont
11、rol, the need for designing overvoltage capability into the motor is eliminated, thus allowing some savings in the motor design. 用这种控制方法，只要采用一台电机，就可实现不同设备不同要求条件下的补偿控制。这样，电机的最大速度由控制方法建立，电机过电压能力设计不再需要，从而给电机设计带来便利。,斜体部分参考译文(续): One of the drawbacks of motor speed control by variation of the average pow
12、er input is that as the input power is reduced to reduce the speed, the available torque is also reduced. 采用改变输入平均功率的方法控制电机速度的缺点之一是，当降低输入功率减速时，输入的转矩也随之下降。 The way to get this information from brush-type motors is by looking at the back EMF generated by the motor during the time that the controlling
13、SCR is off. 电刷式电机得到这种信息的方法是观察控制可控硅关闭时由电机产生的反向电动势。,9.3 Further Reading Mode of Thermal System Control 热系统控制模式,New Words mold muld v. n. 铸模 setpoint set,point n. 设定点；设定值 spike spaik n. 峰值，尖峰脉冲 suppression spren n. 抑制，熄灭 deviation ,di:viein n. 偏差，背离，偏离,组成段落的句子分三种： （1）主旨句（topic sentence） 点出段落的主旨（what is
14、 about）。 （2）推展句（development sentence） 说明或支持主旨。 （3）结尾句（concluding sentence） 结论（conclusion）。 如图9-6所示，每个段落只能有一个主旨（central idea），表达主旨的句子称为主旨句，说明或支持这个主旨句的其余句子称为推展句，最后做结论的句子称为结尾句。,9.4 General Knowledge 段落的组成 文章（composition）的构成要素之一是段落（paragraph），而段落是由句子（sentence）组成的。,【例9-1】（主旨句）Forward-biasing of a P-N jun
15、ction takes places when the polarity of the source voltage is positive to the P material and negative to the N material. （推展句1）This condition causes a current flow. （推展句2）The depletion zone of the device is reduced and majority current carriers are driven toward the junction. （结尾句）One junction of a transistor must be forward biased when it operates.,段落的组成（续）,课后作业 P.83，Exercise 3,
