## 恒压供水系统PLC程序设计+梯形图

Title      Water Supply System PLC programming
Abstract
The system design is based on Siemens S7-200 series PLC control frequency of water supply systems, this paper introduces the control system of the system structure and working principle.This article shows how to design a water supply system using PLC. The system is composed by three pumps forming a circulatory converting model. By analyzing the collected data, a converter is employed to conduct speed-controlled conversion and soft start toward the three-phased pump. “First launch, first stop” principle is applied to control the operation of frequency conversion. Technical information about water pressure through the pressure sensors is transmitted to PLC. Then, in comparison with initiative values, PID makes calculations to change the voltage, the frequency of transformers, the rotating speed of the pump and the level of water supply, stabilizing the pressure to achieve better control of constant-pressure water supply.
Keywords  PLC  constant-pressure water supply  frequency conversion

1 绪论    1
1.1 课题的提出    1
1.2 本课题的背景及其意义    1
1.3恒压供水的现况    2
1.4 PLC概述    2
1.4.1可编程控制器的定义    2
1.4.2  PLC发展和应用    2
1.4.3 西门子S7-200PLC简介    3
1.5 本课题的主要研究内容    3
2 系统的理论分析及控制方案确定    4
2.1变频恒压供水系统的理论分析    4
2.1.1 变频器调速原理    4
2.1.2 变频恒压供水系统的节能原理    5
2.2 确定恒压供水系统控制方案    6
2.2.1 控制方案分析    6
2.2.2恒压供水系统结构组成及原理图    7
2.2.3 系统运行流程    8
2.2.4 分析切换条件    9
3 恒压系统硬件设计    9
3.1 系统主要设备的选型    9
3.1.1 PLC及扩展模块    10
3.1.2 变频器的选型    10
3.2 系统主电路分析及设计    10
3.3系统控制电路分析及其设计    12
3.4 PLC的I/O端口分配及外围接线图    13
4系统的软件设计    16
4.1 系统软件设计分析    16
4.2 PLC程序设计    17
4.2.1控制系统主程序设计    18
4.2.2 控制系统子程序设计    21
4.3 PID控制器参数整定    24
4.3.1 PID控制算法    24

4.3.2 变频恒压供水系统的近似数学模型    26
4.3.3 PID参数整定    26

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