机械工程专业英语第二版必考翻译(完整版)(3)

and process impediment. They also control attached motor starters, pilot lights, values and many other devices. Both functions respond to a custom, user-created program.(What is a PLC?) （P62）

PLC，本质上是监控附加装置的外部传感活动，他们接受数据，这些数据提供广泛的活动，如机器性能、能量输出和加工障碍。它们也控制相连的马达启动器、导航灯、阀门和许多其他装置。所有的功能都对应一个惯例，实用程序。

14. They (PLCs) are designed for real-time use, and often must withstand harsh environments on the shop floor. The programmable logic controller circuitry monitors the status of multiple sensor input, which control output actuators, which may be things like motor starters, solenoid, lights and displays, or valves. (What is a PLC?) （P62）

PLC 被设计为实时应用，常常必须经受车间恶劣环境。PLC的电路检测很多传感器输入的状态，控制输出执行机构，如马达启动器、螺线管、灯、显示屏和阀门。

15. Most PLCs are programmed in a special language called Ladder dder logic is essentially a Boolean logic-solving program with a graphical user interface designed to look like an elementary wiring diagram, familiar to all industrial electricians. (What is a PLC?) （P62） 大多数的PLC都是用梯形逻辑这种特殊语言进行编程的。梯形逻辑本质是一个具有图形用户界面的布尔逻辑处理程序，，设计成一个所有的工业电气师都熟悉的基本电气线图。

16. PID can be described as a set of rules with which precise regulation of a closed-loop control system is obtained. Closed loop control means a method in which a real-time measurement of the process being controlled is constantly fed back to the controlling device to ensure that the value which is desired is, in fact, being realized. (What is PID Control) （P63）

PID可以用一组规则描述，通过这组规则可获得闭环控制系统的精密调控。闭环控制是一种方法，用这种方法可将被控过程的实时检测持续地反馈给控制设备以确保期望值被实现。

17. The most important of these (PIDs), Proportional Control, determines the magnitude of the difference between the SETPOINT and the PROCESS VARIABLE (known as ERROR), and then applies appropriate proportional changes to the CONTROL VARIABLE to eliminate ERROR. (What is PID Control) （P63）

PID中最重要的是比例控制，它决定了设定值和过程变量间的差值，然后对控制变量使用合适的比例变量以消除误差。

18. Shafting is the machine element that supports a roller and wheel so that they can perform their basic functions of rotation. Shafting, made from round metal bars of various lengths and machined to dimension the surface, is used in a great variety of shapes and applications. Because shafts carry loads and transmit power, they are subject to the stresses and strains of operating machine parts. Standardized procedures have been evolved for determining the material characteristics and size requirements for safe and economical construction and operation. (Shafting) （P67）

轴是能支撑滚子和轮子以完成最基本的旋转运动的机械元件。轴，由各类长度的圆形金属棒料制成，被加工成各类的表面尺寸，以各种形状用于各种用途。轴因为承载和传动必经受在工作的机器零件的应力和应变。已演化出的标准流程确定安全经济结构操作所需的材料特性和尺寸要求。

19. The normal form of shafting is a solid bar. Solid shafting is obtainable commercially in round bar stock up to 15 cm in diameter;it is produced by hot-rolling and cold-drawing or by machine-finishing with diameters in increments of 6 mm or less.For larger sizes,special rolling procedures are required,and for extremely large shafts,billets are forged to the proper shape. Particularly in solid shafting, the shaft is stepped to allow greater strength in the middle portion with minimum diameter on the ends at the bearings. The steps allow shoulders for positioning the various parts pressed onto the shaft during the rotor assembly. (Shafting) （P67）

特别是实心轴，阶梯轴允许中部有更大的强度，端部轴承处直径最小。阶梯允许轴肩在转子装置期间，通过靠在轴上来定位各类零件。

20. Differing widely in viscosity, specific gravity, vapor pressure, boiling point, and other properties, lubricants also offer a wide range of selection for the increasingly varied needs of