【正文】 電信學院畢業(yè)設計任務書題目 基于PLC的污水池液位控制系統(tǒng)設計 學生姓名 班級 學號 題目類型 工程設計 指導教師 魏祥林 系主任 一、畢業(yè)設計（論文）的技術背景和設計依據(jù)： 與傳統(tǒng)的人工調(diào)節(jié)液位控制系統(tǒng)相比，變頻液位自動控制系統(tǒng)具有節(jié)能效果顯著、人工勞動強度低，系統(tǒng)工作可靠、自動化程度高等優(yōu)點。為了實現(xiàn)污水池液位的恒定控制，本設計要求S7200 PLC作為控制器，完成對現(xiàn)場數(shù)據(jù)的采集、變頻器的控制、PID控制算法的實現(xiàn)。二、畢業(yè)設計（論文）的任務熟悉題目要求，查閱相關科技文獻，寫出開題報告；方案設計（包括方案論證與確定、技術經(jīng)濟分析等內(nèi)容）；硬件系統(tǒng)設計；軟件系統(tǒng)設計；撰寫設計說明書，繪制圖紙；翻譯一篇與自己所學專業(yè)或設計有關的英文資料；三、畢業(yè)設計（論文）的主要內(nèi)容、功能及技術指標：系統(tǒng)要求用戶能夠直觀地了解現(xiàn)場設備地工作狀況及水位的變化；要求用戶能夠遠程控制變頻器的啟動和停止；用戶可以自行設置水位的高、低，以及控制變頻器的啟、停；變頻器及其他設備的故障信息能夠及時反映在遠程單片機上；具有水位過高、過低報警和提示用戶功能。專業(yè)英文文獻翻譯； PLCs Past, Present and FutureEveryone knows there39。s only one constant in the technology world, and that39。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 proximity to real world devices and municate back to other system controls in a main panel. In the past 30 years we have seen literally hundreds of proprietary and standard protocols developed, each with their own unique 39。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。t be ignored, such as: * Network speed. * Ease of use when it es to the setup and wiring. * Availability of offtheshelf networking ponents. * Builtin munications setups.Integrated Motion ControlAnother responsibility the PLC has been tasked with is motion control. From simple openloop to multiaxis applications, the trend has been to integrate this feature into PLC hardware and software. There are many applications that require accurate control at a fast pace, but not exact precision at blazing speeds. These are applications where the standalone PLC works well. Many nano and micro PLCs are available with highspeed counting capabilities and highfrequency pulse outputs built into the controller, making them a viable solution for openloop control. The one caveat is that the controller does not know the position of the output device during the control sequence. On the other hand, its main advantage is cost. Even simple motion control had previously required an expensive option module, and at times was restricted to more sophisticated control platforms in order to meet system requirements. More sophisticated motion applications require higherprecision positioning hardware and software, and many PLCs offer highspeed option modules that interface with servo drives. Most drives today can accept traditional mands from host (PLC or PC) controls, or provide their own internal motion control. The trend here is to integrate the motion control configuration into the logic controller programming software package.Programming LanguagesA facet of the PLC that reflects both the past and the future is programming language. The IEC 611313 standard deals with programming languages and defines two graphical and two textual PLC programming language standards: * Ladder logic (graphical). * Function block diagram (graphical). * Structured text (textual).Instruction list (textual). This standard also defines graphical and textual sequential function chart