外文翻译---可编程控制器的介绍及未来发展(编辑修改稿)

外文翻译---可编程控制器的介绍及未来发展(编辑修改稿)内容摘要：

sk has not been tackled in a scientific way. Furthermore, building a bridge between design theory and the latest epistemological outes of formal representations in puter sciences and operations research, such as discrete event system modeling, can advance future development in engineering design. Application in Logical Hardware Design From a logical perspective, PLC software design is similar to the hardware design of integrated circuits. Modern VLSI designs are extremely plex with several million parts and a product development time of 3 years [Whitney, 1996]. The design process is normally separated into a ponent design and a system design 5 stage. At ponent design stage, single functions are designed and verified. At system design stage, ponents are aggregated and the whole system behavior and functionality is tested through simulation. In general, a plete verification is impossible. Hence, a systematic approach as exemplified for the PLC program design may impact the logical hardware design. PLC PLC（ programmable logical controller） face ever more plex challenge these days. Where once they quietly relays and gave an occasional report to a corporate mainframe, they are now grounded into cells, give new jobs and new languages, and are forced to pete against a growing array of control products. For this year’s annual PLC technology update, we queried PLC makers on these topics and more. Programming languages Higher level PLC programming languages have been around for some time, but lately their popularity has been mushrooming. As Raymond Lavelle, vice president and general manager, Siemens Energy and Automation. Inc, Programmable Controls Division, points out :”As programmable controls are being used for more and more sophisticated operations, languages other than ladder logic bee more practical, efficient, and powerful. For example, it39。 s very difficult to write a trigonometric function using ladder logic. ”Languages gaining acceptance include Boolean, control system flowcharting, and such function chart languages as Graphtec and its variations. And these’s increasing interest in languages like C and BASIC. PLC in process control Thus far, PLC have not been used extensively for continuous process control. Will this continue? ”The feeling that I’ve gotten,” says Ken Jeante, manager, product planning, Series One and Series Six products, at GE Frame North America, is that PLC will be used in the process industry but not necessarily for process control.” Several vendorsobviously betting that the opposite will happenhave introduced PLC optimized for process applications. Rich Ryan, mercial marketing, AllenBradley Programmable Controls Div, cites PLC increasing use in such 6 industries as food, chemicals, and petroleum. Ryan feel there are two types of applications in which they’re appropriate.” ,he says, is where the size of the process control system that39。 s being automated doesn’t justify DCS[distributed control systems].With the starting price tags of those products being relatively high, a programmable controller makes sense for small, low loop count applications. The seconds where you have to integrate the loop closely with the sequential logic. Batch controller sere prime examples, where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logic outweighs some of the disadvantages of not having a distributed control system.” Bill Barkovtz, president of Triconex, predicts that all future controllers that e out in the process control system business will embrace a lot more PLC technology and a lot more PLC functionality than they ever did before.” Communications and MAP Communications are vital to an individual automation cell and to the automated factory as a whole. We39。 ve heard a lot about MAP in the last few years, and a lot of panies have jumped on the band wagon. Many, however were disappointed when a fullydefined and pleted MAP specification didn’t appear immediately. Says Larry Kumara .Right now , MAP is still a moving target for the manufactu。