英语翻译It is interesting to observe the progress that has been made in the past 15 years in the programmable controller area.The pioneer products of the late 1960s must have been confusing and frightening to a great number of people.For example,

英语翻译It is interesting to observe the progress that has been made in the past 15 years in the programmable controller area.The pioneer products of the late 1960s must have been confusing and frightening to a great number of people.For example,
英语翻译
It is interesting to observe the progress that has been made in the past 15 years in the programmable controller area.The pioneer products of the late 1960s must have been confusing and frightening to a great number of people.For example,what happened to the hardwired and electromechanical devices that maintenance personnel were used to repairing with hand tools?They were replaced with ‘computers’ disguised as electronics designed to replace relays.Even the programming tools were designed to appear as relay equivalent presentations.We have the opportunity now to examine the promise,in retrospect,that the programmable controller brought to manufacturing.
All programmable controllers consist of the basic functional blocks shown in Fig.10.1.We’ll examine each block to understand the relationship to the control system.First we look at the center,as it is the heart ( or at least the brain ) of the system.It consists of a microprocessor,logic memory for the storage of the actual control logic,storage or variable memory for use with data that will ordinarily change as a function power for the processor and memory.Next comes the I/O block.This function takes the control level signals for the CPU and converts them to voltage and current levels suitable for connection with factory grade sensors and actuators.The I/O type can range from digital (discrete or on / off),analog (continuously variable),or a variety of special purpose ‘smart’ I/O which are dedicated to a certain application task.The programmer is shown here,but it is normally used only to initially configure and program a system and is not required for the system to operate.It is also used in troubleshooting a system,and can prove to be a valuable tool in pinpointing the exact cause of a problem.The field devices shown here represent the various sensors and actuators connected to the I/O.These are the arms,legs,eyes,and ears of the system,including push buttons,limit switches,proximity switches,photosensors,thermocouples,RTDS,position sensing devices,and bar code reader as input; and pilot lights,display devices,motor starters,DC and AC drives,solenoids,and printers as outputs.
No single attempt could cover its rapidly changing scope,but three basic characteristics can be examined to give classify an industrial control device as a programmable controller.
(1) Its basic internal operation is to solve logic from the beginning of memory to some specified point,such as end of memory or end of program.Once the end is reached,the operation begins again at the beginning of memory.This scanning process continues from the time power is supplied to the time it it removed.

英语翻译It is interesting to observe the progress that has been made in the past 15 years in the programmable controller area.The pioneer products of the late 1960s must have been confusing and frightening to a great number of people.For example,
观察可编程控制器在最近15年取得的进步,是件很有趣的事情.在20世纪60年代末早期的产品或许,会使很多人感到惊恐或迷惑不解,例如,维修人员习惯了手动工具,那么对于电子仪器的部件和机电设备将会发生什么呢?改装过的计算机代替这些设备,正如电子器件代替继电器,甚至设计出了工具来作为继电器的替代品.我们现在有机会来审视一下前景,回顾过去,可编程控制器带给制造业带来什么呢?
可编程控制器都包含了基本的功能模块,如图10.1所示.为了理解控制系统间的关系,我们将检查一下每个模块.首先,我们看一下中心,它是系统的心脏.中心包括微处理器、存储当前控制逻辑的逻辑存储器、存储常变量数据的变量存储器,中心部分具有控制程序执行和微处理器与存储器提供电力的功能.接着是I/O模块,它的功能是为CPU提供控制水平信号,并把它们转化为适合连接工厂级别的传感器和调节器的标准电压和电流.I/O类型可以是数字信号、模拟信号或是应用于某一特定应用的“智能”I/O.程序员通常仅需编写程序,而不需要考虑程序在系统中的运行.它可以用来发现并修理系统故障的确切原因方面是个很有用的设备.在这里提到的设备代表了与I/O连接的各种传感器和调节器,它们是系统的手臂、腿、眼睛和耳朵,其中包括按钮、行程开关、光敏元件、热电偶、位置传感器,作为输入的读卡机、标灯、显示设备、发动机、DC和AC驱动器、螺线管和作为输出的打印机.
没有任何单一的检测可概括的迅速变化,但对其三个基本特征进行检查,可以归类为一个可编程控制器的工业控制装置.
(1)它的基本的内部运作,是从一开始就一些具体问题,来解决内存逻辑的,如程序存储器末端.一旦达到目的,操作在存储的开端重新开始,该扫描过程持续时间是从删除它到间接通电源.