电气工程及其自动化专业外文文献英文文献外文翻译plc方面

电气工程及其自动化专业外文文献英文文献外文翻译plc方面内容摘要：

socket n. 插座 B:PLC[1] PLCs (programmable logical controller) face ever more plex challenges these days . Where once they quietly replaced relays and gave an occasional report to a corporate mainframe, they are now grouped into cells, given new job and new languages, and are forced to pete against a growing array of control products. For this year39。 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 mushrooming. As Raymond Leveille, vice president amp。 general manager, Siemens Energy amp。 Automation .inc。 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 Graphcet and its variation .And there39。 s increasing interest in languages like C and BASIC. PLCs in process control Thus far, PLCs have not been used extensively for continuous process control .Will this continue? The feeling that I39。 ve gotten, says Ken Jannotta, manger, product planning, series One and Series Six product ,at GE Fanuc North America ,39。 is that PLCs will be used in the process industry but not necessarily for process control. Several vendors obviously betting that the opposite will happen have introduced PLCs optimized for process application .Rich Ryan, manger, mercial marketing, Allenbradley Programmable Controls Div., cites PLCs39。 s increasing use such industries as food ,chemicals ,and petroleum. Ryan feels there are two types of applications in which they39。 re appropriate. one, he says, is where the size of the process control system that39。 s being automated doesn39。 t justify DCS[distributed control system].With the starting price tags of chose products being relatively high, a programmable controller makes sense for small, low loop count application .The second is where you have to integrate the loop closely with the sequential logical .Batch controllers are prime example ,where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logical outweighs some of the disadvantages of not having a distributed control system. Bill Barkovitz, president of Triconex, predicts that all future controllers that e out in the process control system business will embrace a lot of 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 be 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 bandwagon.[2]Many, however, were disappointed when a fullydefined and pleted MAP specification didn39。 t appear immediately .Says Larry Komarek: Right now, MAP is still a moving target for the manufacturers, a specification that is not final .Presently, for example. people are introducing products to meet the . products will be obsolete when the new standard for is introduced. Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example, has an ongoing MAPpatibility program。 [3]but Frank Newburn, vice president of Omron39。 s Industrial Division ,reports that because of the lack of a firm definition ,Omron39。 s PLCs don39。 t yet talk to MAP. Since it39。 s unlikely that an individual PLC would talk to broad MAP anyway, makers are concentrating on proprietary works. According to Sal Provanzano, users fear that if they do get on board and vendors withdraw from MAP, they39。 ll be the ones left holding a munications structure that39。 s not supporte。