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电信学院毕业设计任务书
题目 基于PLC的污水池液位控制系统设计 学生姓名 班级 学号 题目类型 工程设计 指导教师 魏祥林 系主任 一、毕业设计（论文）的技术背景和设计依据：
与传统的人工调节液位控制系统相比，变频液位自动控制系统具有节能效果显著、人工劳动强度低，系统工作可靠、自动化程度高等优点。
为了实现污水池液位的恒定控制，本设计要求S7-200 PLC作为控制器，完成对现场数据的采集、变频器的控制、PID控制算法的实现。
二、毕业设计（论文）的任务
1、熟悉题目要求，查阅相关科技文献，写出开题报告； 2、方案设计（包括方案论证与确定、技术经济分析等内容）； 3、硬件系统设计； 4、软件系统设计；
6、撰写设计说明书，绘制图纸；
6、翻译一篇与自己所学专业或设计有关的英文资料；
三、毕业设计（论文）的主要内容、功能及技术指标：
1、系统要求用户能够直观地了解现场设备地工作状况及水位的变化； 2、要求用户能够远程控制变频器的启动和停止；
3、用户可以自行设置水位的高、低，以及控制变频器的启、停； 4、变频器及其他设备的故障信息能够及时反映在远程单片机上； 5、具有水位过高、过低报警和提示用户功能。 6、专业英文文献翻译；
PLCs --Past, Present and Future
Everyone knows there's only one constant in the technology world, and that'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 a wide range of industries.
At industrialized computer programmed with the computer and information technology worlds. The most prominent of which is miniaturization and communications. The Shrinking PLC
When the PLC was first introduced, its size was a major improvement - relative to the 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 introduced in the nano and micro classes that offer features previously found only in larger PLCs. This those in the nano class are capable of Ethernet communication, motion control, on-board PID with autotune, remote connectivity and more.
PLCs are also now well-equipped to replace stand-alone 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 ( machine interface) functions. Previously, these functions often required their own purpose-built controllers and software, plus a separate PLC for the discrete control and interlocking.
The Great Communicator
Possibly the most significant change in recent years lies in the communications arena. In the 1970s Modicon introduction of Modbus communications protocol allowed PLCs to communicate over standard cabling. This translates to an ability to place PLCs in closer proximity to real world devices and communicate back to other system controls in a main panel.
In the past 30 years we literally unique advantages.Today's PLCs gateways. They the process. And furthermore, they need all these capabilities while remaining cost-effective and simple to program.
Another primary development that the plant floor the past five years. While serial communications remain popular and reliable, Ethernet is fast becoming the communications media of choice with advantages that simply can't be ignored, such as: * Network speed. * Ease of use when it comes to the setup and wiring. * Availability
of off-the-shelf networking components. * Built-in communications setups.
Integrated Motion Control
Another responsibility the PLC tasked with is motion control. From simple open-loop to multi-axis applications, the trend to integrate this feature into PLC at blazing speeds. These are applications where the stand-alone PLC works well. Many nano and micro PLCs are available with for open-loop control.
The one caveat is that the controller does not know the position of the output device during the control sequence. On the other advantage is cost. Even simple motion control expensive option module, and at times was restricted to more sophisticated control platforms in order to meet system requirements.
More sophisticated motion applications require positioning modules that interface with servo drives. Most drives today can accept traditional commands from internal motion control. The trend control configuration into the logic controller programming software package.
Programming Languages
A facet of the PLC that reflects both the past and the future is programming language. The IEC standard deals with programming languages and defines two graphical and two textual PLC programming