河南职业技术学院

毕业设计（论文）

题 目 PLC的锅炉温度控制系统

系（分院） 电气工程系 学生姓名 孔永婷 学 号 11112036 专业名称 电气自动化 指导教师 徐瑞丽

2013年11月8日

目 录

1.1课题背景 ····································································· 4 图 3-4 系统硬件连线图 ····················································· 14 3.4 PLC控制器的设计 ···················································· 14 控制器的设计是整个控制系统设计中最重要的一步。首先要根据受控对象的数学模型和它的各特性以及设计要求，确定控制器的结构以及和受控对象的连接方式。最后根据所要求的性能指标确定控制器的参数值。 ···················································································· 14 3.4.1 控制系统数学模型的建立 ·········································· 14 在本控制系统中，TT1(出口温度传感器)将检测到的出口水温度信号转化为电流信号送入EM235模块的A路，TT2(炉膛温度传感器)将检测到的出口水温度信号转化为电流信号送入EM235模块的B路。两路模拟信号经过EM235转化为数字信号送入PLC，PLC再通过PID模块进行PID调节控制。具体流程在第四章程序编写的时候具体论述。由PLC的串级控制系统框图如图 3-5： ·································································· 15 如图3-5 串级控制系统框图 ··············································· 15 3.4.2 PID控制及参数整定 ··············································· 15

4.3.3 控制程序及分析 ··········································· 20 因为由AIW0和AIW2输入的是6400--32000的数字量，所以要转换为实际的温度要进行运算，运算公式为： ··················· 20

T?(D?6400)?100 公式（4-1） ······························ 20

32000?6400其中，T为实际温度，D为AIWO和AIW2输入的数字量。 20 PLC的内存地址分配见 表4-1 ·································· 20 控制程序如图4-14—图4-所示 ： ···························· 21 主程序： ···························································· 21 图4-14 控制程序1 ··············································· 21 主调节器程序： ···················································· 21 副调节器程序： ···················································· 23

·············································································· 23

第五章 组态画面的设计 ······································ 24 本章详细的讲解一个组态系统的建立和设计。 ············· 24 5.1 组态变量的建立及设备连接 ···························· 24 5.1.1 新建项目 ···················································· 24 双击组态王的快捷方式，出现组态王的工程管理器窗口，双击新建按扭，按照弹出的建立向导，填写工程名称。然后打开刚建立的工程。进入组态画面的设计 ········································ 24

1.新建画面 ························································· 24 进入工程管理器后，在画面右方双击“先建”，新建画面，并设置画面属性，图5-2所示： ········································ 25

图5-2 画面新建 ··················································· 25 要实现组态王对S7-200的在线监控，就先必须建立两者之间的联系，那就需要建立两者间的数据变量。基本类型的变量可以分为“内存变量”和I/O变量两类。内存变量是组态王内部的变量，不跟被监控的设备进行交换。而I/O变量是两者之间互相交换数据的桥梁，S7-200和组态王的数据交换是双向的 ····················· 25

5.2 创建组态画面 ·············································· 25 5.2.1 新建主画面 ················································· 25 如图 5-9所示，高温报警用来显示当温度高于95°C的时候，等会变红闪烁，加热炉上的指示灯用来指示加热炉的加热状态。 ·············································································· 25

图5-9 控制系统主画面 ········································ 26 5.2.2 新建PID参数设定窗口 ·································· 26 图5-10 PID参数设定窗口 ····································· 26 如图5-10所示，PID参数设定窗口，用来设定主控制器和副控制器的PID参数值，可与PID参数的整定。 ······················ 26

5.2.3新建实时曲线 ·············································· 26 实时趋势曲线可在工具箱中双击后在画面直接获得。实时趋势曲线随时间变化自动卷动，可快速反应变量的新变化。如图5-12所示:··········································································· 26

图5-12 实时曲线窗口 ·········································· 27 5.2.4 新建报警窗口 ·············································· 27 图5-15 实时报警窗口 ·········································· 28 图 6-1 监控主画面 ··············································· 29 图 6-2 温度实时曲线 ············································ 29 控制器起到了调节作用，最后温度稳定在了设定温度上，但是调节时间太长，大约10min左右，所以，我们需要增大Kc。点击主控控制画面的参数设定窗口，可以显示PID参数设定界面。参数设置如图 6-4所示： ······················································ 30

6.3 查看数据报表 ················································ 30

点击主画面的数据报表窗口，出现报表窗口，点击报表查询，可以查看报表记录的数据。如图 6-7所示： ························································································· 30

图 6-7 报表查询 ·················································· 31 记录的数据如图 6-8所示： ···································· 31 为了测试系统的的稳定性，我们把温度设定为80°C，所得到的控制曲线如图6-9所示： ··········································· 31

图6-9 60-80时的控制曲线 ··································· 31 如图所示，当设定温度改变时，系统是比较稳定的。 ···· 32 当实际温度超过85°C 时，会出现报警画面，如图6-10所示： ·············································································· 32

系统报警在工业生产中有着重要的作用。 ··················· 32

结束语 ······························································· 32 本文成功的运用了西门子S7-200PLC和组态王设计了一个人机监控的温度控制系统。系统采用串级PID控制，利用粗调和细调，得到了一个反应比较迅速，控制精度比较高的温度控制系统。32

组态王操作方便，有利于我们比较直观的观看控制曲线和温度的变化。其中的报表、历史曲线和报警显示都是在当今工业控制中常用的。 ·································································· 32

当然，本控制系统还有很多不足的地方。例如，系统的自适应能力不强，因为是利用散热来降温的，所以与外界温度环境密接相关，在不同的温度环境下控制精度和控制能力是不同的 ······· 32

摘 要

从上世纪80年代至90年代中期，PLC得到了快速的发展，在这时期，PLC在处理模拟量能力、数字运算能力、人机接口能力和网络能力得到大幅度提高，PLC逐渐进入过程控制领域，在某些应用上取代了在过程控制领域处于统治地位的DCS系统。PLC具有通用性强、使用方便、适应面广、可靠性高、抗干扰能力强、编程简单等特点。PLC在工业自动化控制特别是顺序控制中的地位，在可预见的将来，是无法取代的。

本文介绍了以锅炉为被控对象，以锅炉出口水温为主被控参数，以炉膛内水温为副被控参数，以加热炉电阻丝电压为控制参数，以PLC为控制器，构成锅炉温度串级控制系统；采用PID算法，运用PLC梯形图编程语言进行编程，实现锅炉温度的自动控制。

电热锅炉的应用领域相当广泛，在相当多的领域里，电热锅炉的性能优劣决定了产品的质量好坏。目前电热锅炉的控制系统大都采用以微处理器为核心的计算机控制技术，既提高设备的自动化程度又提高设备的控制精度。

本文分别就电热锅炉的控制系统工作原理，温度变送器的选型、PLC配置、组态软件程序设计等几方面进行阐述。通过改造电热锅炉的控制系统具有响应快、稳定性好、可靠性高,控制精度好等特点，对工业控制有现实意义。

关键词：电热锅炉的控制系统 温度控制 串级控制 PLC PID

1.1课题背景

电热锅炉的应用领域相当广泛，电热锅炉的性能优劣决定了产品的质量好坏。目