【正文】 nefited PLC networking have migrated to the I/O level. Many PLC manufacturers are supporting the most accepted fieldbus networks, allowing PLC I/O to be distributed over large physical distances, or located where it was previously considered nearly impossible. This has opened the door for personal puters to interface with standard PLC I/O subsystems by using interface cards, typically supplied by the PLC manufacturer or a third party developer. Now these challenging locations can be monitored with today a PC. Where industrialgrade control engines are not required, the user can take advantage of more advanced software packages and hardware flexibility at a lower cost. * The ability to use universal programming software for multiple targets/platforms. In the past it was expected that an intelligent controller would be plex to program. That is no longer the case. Users are no longer just trained programmers, such as design engineers or systems integrators, but endusers who expect easiertouse software in more familiar formats. The Windowsbased look and feel that users are familiar with on their personal puters have bee the most accepted graphical user interface. What began as simple relay logic emulation for programming PLCs has evolved into languages that use higher level function blocks that are much more intuitive to configure. PLC manufacturers are also beginning to integrate the programming of diverse functions that allow you to learn only one package in configuring logic, HMI, motion control and other specialized capabilities. Possibly the ultimate wish of the enduser would be for a software package that could seamlessly program many manufacturers PLCs and subsystems. After all, Microsoft Windows operating system and applications work similarly whether installed on a Dell, HP or IBM puter, which makes it easier for the user. Overall, PLC users are satisfied with the products currently available, while keeping their eye on new trends and implementing them where the benefits are obvious. Typically, new installations take advantage of advancing technologies, helping them bee more accepted in the industrial world. PLC的過(guò)去、現(xiàn)在與未來(lái)眾所周知，科技世界里只有一個(gè)永恒真理，那就是變化。s PLCs have to be data pilers and information gateways. They have to interface with bar code scanners and printers, as well as temperature and analog sensors. They need multiple protocol support to be able to connect with other devices in the process. And furthermore, they need all these capabilities while remaining costeffective and simple to program. Another primary development that has literally revolutionized the way PLCs are programmed, municate with each other and interface with PCs for HMI, SCADA or DCS applications, came from the puting world. Use of Ethernet munications on the plant floor has doubled in the past five years. While serial munications remain popular and reliable, Ethernet is fast being the munications media of choice with advantages that simply can39。s only one constant in the technology world, and that39。二、畢業(yè)設(shè)計(jì)（論文）的任務(wù)熟悉題目要求，查閱相關(guān)科技文獻(xiàn)，寫出開(kāi)題報(bào)告；方案設(shè)計(jì)（包括方案論證與確定、技術(shù)經(jīng)濟(jì)分析等內(nèi)容）；硬件系統(tǒng)設(shè)計(jì)；軟件系統(tǒng)設(shè)計(jì)；撰寫設(shè)計(jì)說(shuō)明書(shū)，繪制圖紙；翻譯一篇與自己所學(xué)專業(yè)或設(shè)計(jì)有關(guān)的英文資料；三、畢業(yè)設(shè)計(jì)（論文）的主要內(nèi)容、功能及技術(shù)指標(biāo)：系統(tǒng)要求用戶能夠直觀地了解現(xiàn)場(chǎng)設(shè)備地工作狀況及水位的變化；要求用戶能夠遠(yuǎn)程控制變頻器的啟動(dòng)和停止；用戶可以自行設(shè)置水位的高、低，以及控制變頻器的啟、停；變頻器及其他設(shè)備的故障信息能夠及時(shí)反映在遠(yuǎn)程單片機(jī)上；具有水位過(guò)高、過(guò)低報(bào)警和提示用戶功能。電信學(xué)院畢業(yè)設(shè)計(jì)任務(wù)書(shū)題目 基于PLC的污水池液位控制系統(tǒng)設(shè)計(jì) 學(xué)生姓名 班級(jí) 學(xué)號(hào) 題目類型 工程設(shè)計(jì) 指導(dǎo)教師 魏祥林 系主任 一、畢業(yè)設(shè)計(jì)（論文）的技術(shù)背景和設(shè)計(jì)依據(jù)： 與傳統(tǒng)的人工調(diào)節(jié)液位控制系統(tǒng)相比，變頻液位自動(dòng)控制系統(tǒng)具有節(jié)能效果顯著、人工勞動(dòng)強(qiáng)度低，系統(tǒng)工作可靠、自動(dòng)化程度高等優(yōu)點(diǎn)。為了實(shí)現(xiàn)污水池液位的恒定控制，本設(shè)計(jì)要求S7200 PLC作為控制器，完成對(duì)現(xiàn)場(chǎng)數(shù)據(jù)的采集、變頻器的控制、PID控制算法的實(shí)現(xiàn)。專業(yè)英文文獻(xiàn)翻譯； PLCs Past, Present and FutureEveryone knows there39。s change. This is especially evident in the evolution of Programmable Logic Controllers (PLC) and their varied applications. From their introduction more than 30 years ago, PLCs have bee the cornerstone of hundreds of thousands of control systems in a wide range of industries. At heart, the PLC is an industrialized puter programmed with highly specialized languages, and it continues to benefit from technological advances in the puter and information technology worlds. The most prominent of which is miniaturization and munications.The Shrinking PLCWhen the PLC was first introduced, its size was a major improvement relative to the hundreds of hardwired relays and timers it replaced. A typical unit housing a CPU and I/O was roughly the size of a 19 television set. Through the 1980s and early 1990s, modular PLCs continued to shrink in footprint while increasing in capabilities and performance (see Diagram 1 for typical modular PLC configuration). In recent years, smaller PLCs have been introduced in the nano and micro classes that offer features previously found only in larger PLCs. This has made specifying a larger PLC just for additional features or performance, and not increased I/O count, unnecessary, as even those in the nano class are capable of Ethernet munication, motion control, onboard PID with autotune, remote connectivity and more. PLCs are also now wellequipped to replace standalone process controllers in many applications, due to their ability to perform functions of motion control, data acquisition, RTU (remote telemetry unit) and even some integrated HMI (human machine interface) functions. Previously, these functions often required their own purposebuilt controllers and software, plus a separate PLC for the discrete control and interlocking.The Great CommunicatorPossibly the most significant change in recent years lies in the munications arena. In the 1970s Modicon introduction of Modbus munications protocol allowed PLCs to municate over standard cabling. This translates to an ability to place PLCs in closer proximi