基于PLC的中央空调温度器控制系统毕业设计论文

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摘 要

本温度控制器设计采用变频器、PLC、温度传感器等器件的有机结合，构成温差闭环自动控制系统，自动调节水泵的输出流量达到节能目的。该系统采用西门子的S7—200PLC作为主控制单元，利用传统 PID 控制算法，通过西门子 MM440 变频器控制水泵运转速度，保证系统根据实际负荷的情况调整流量，实现恒温控制，从而最大程度的解决能源浪费问题。

本设计通过采用基于 USS 协议的RS-485总线通讯的网络，通过西门子 TD200文本显示器实现人机界面的设计，使用 MCGS 工控组态软件，对系统进行理论分析。通过分析该设计，验证了该设计的可靠性，可以解决中央空调温度控制器的能源浪费问题。

关键词：中央空调温度控制器，PLC，PID，变频器

ABSTRACT

This design is developed based on the combination of frequency converter, PLC, temperature sensor. It makes up a temperature difference closed-loop automatic control system and automatically adjust the output flow of pump to achieve energy saving. The system adopts the Siemens S7-200 PLC as the main control unit, using the traditional PID to control algorithm, using Siemens MM440 inverter to control of pump speed, to guarantee system adjust load flow according to actual situation. All of these will bring out constant temperature control, so as to solve the problem of energy waste to a great extent.

This design use RS - 485 bus communication networks which is based on USS protocol and using the Siemens TD200 to realize the -computer interface design, and using the software made from MCGS, to carries on the theoretical analysis to the system. Verified the reliability of the design, the design can solve the problem of central air conditioning energy waste through the analysis of the design.

KEY WORDS: The central air conditioning, PLC, PID, frequency converter

目 录

摘 要.............................................................................................................................. I ABSTRACT .................................................................................................................. II 第1章 绪论.................................................................................................................. 1

1.1 中央空调温度控制器的发展.......................................................................... 1

1.1.1 中央空调温度控制器现在状况............................................................ 1 1.1.2 中央空调温度控制发展趋势................................................................ 1 1.2 本设计的意义.................................................................................................. 1

1.2.1 设计的主要内容.................................................................................... 1 1.2.2 设计的意义............................................................................................ 2

第2章 中央空调温度控制器系统介绍...................................................................... 3

2.1 中央空调温度控制器结构.............................................................................. 3

2.1.1 中央空调温度控制器概述.................................................................... 3 2.1.2 中央空调温度控制器结构.................................................................... 3 2.2 中央空调温度控制器系统工作原理.............................................................. 4

2.2.1 制冷原理................................................................................................ 4 2.2.2 工作原理................................................................................................ 4 2.2.3 中央空调温度控制器的控制原理........................................................ 4 2.3 中央空调温度控制器的评价.......................................................................... 5 2.4 本章小结.......................................................................................................... 5 第3章 中央空调温度控制器控制系统的硬件设计.................................................. 6

3.1 变频器.............................................................................................................. 6

3.1.1 变频器的介绍........................................................................................ 6 3.1.2 变频调速的原理.................................................................................... 6 3.1.3 变频器的选择........................................................................................ 9 3.1.4 使用注意的问题.................................................................................. 10 3.2 电机的软启动原理及应用............................................................................ 11

3.2.1 软启动的介绍...................................................................................... 11 3.2.2 软启动工作原理.................................................................................. 11 3.2.3 软启动的优点...................................................................................... 11 3.2.4 软启动与变频器的对比...................................................................... 12 3.3 PLC选型 ........................................................................................................ 12

3.3.1 PLC的工作原理 .................................................................................. 12

3.3.2 西门子S7—200介绍 ......................................................................... 13 3.4 温度传感器.................................................................................................... 14 3.5 温度变送器.................................................................................................... 15 3.6 人机界面选型方案........................................................................................ 15 3.7 总体硬件设计................................................................................................ 16 3.8 本章小结........................................................................................................ 18 第4章 软件设计........................................................................................................ 20

4.1 PID控制 ......................................................................................................... 20

4.1.1 PID控制简介 ....................................................................................... 20 4.1.2 PID参数整定 ....................................................................................... 20 4.1.3 对中央空调温度控制器的PID控制 ................................................. 21 4.2 应用软件STEP7 ........................................................................................... 21 4.3 plc编程 ........................................................................................................ 22

4.3.1 程序流程图.......................................................................................... 22 4.3.2 中央空调温度控制器控制系统的IO分配表 ................................... 24 4.3.3 程序中使用的存储器及其功能.......................................................... 25 4.3.4 中央空调温度控制器温度控制系统程序.......................................... 25 4.4 设备通讯........................................................................................................ 26

4.4.1 RS-485介绍 ......................................................................................... 26 4.4.2 USS协议软件与S7—200间的通讯 .................................................. 26 4.5 MCGS组态软件 ............................................................................................ 27

4.5.1 MCGS组态软件简介 .......................................................................... 27 4.5.1 MCGS组态画面 .................................................................................. 27 4.6 本章小结........................................................................................................ 29 第5章 结 论.............................................................................................................. 30 致 谢............................................................................................................................ 31 参考文献...................................................................................................................... 32 附 录............................................................................................................................ 33