摘要

速冻库生产车间温度和湿度对生鲜食品的保鲜保质有很大的影响，对于速冻库车间的温湿度环境检测和调节控制，这就需要通过空调的功能来实现。以往的速冻库车间，通过人工开启和关闭空调设备和除湿机设备，不能实现恒温和恒湿控制，达不到理想的控制效果。本设计采用S7-1200可编程控制器，使用MM440变频器，对除湿机、冷水机组等进行变频调节控制。使用接触器对冷水泵、冷却塔、冷风机设备进行启停控制。系统采集冷冻车间的温度和湿度值，通过PID调节，实现温度和湿度的自动调节控制，采用手动和自动两种方式来设计。

按照PLC系统开发设计步骤，分为控制方案总体设计、硬件选型和图纸设计、软件流程和梯形图设计，通过系统调试对梯形图进行仿真运行。系统设计思路为PID控制，应用编程软件的强大编译功能，完成了功能的分部设计，系统可靠性高，稳定性好，具有很好的可行性，满足了速冻库制冷控制系统的自动化控制需求。

关键词：制冷控制系统，PLC设计，硬件搭建，系统调试

Abstract

The temperature and humidity of the production workshop of the freezing factory have a great impact on the preservation and quality of fresh food. For the temperature and humidity environment detection and adjustment control of the workshop of the freezing factory, it needs to be realized through the function of air conditioning. In the past, the refrigeration plant workshop could not achieve constant temperature and humidity control by manually turning on and off the air conditioning equipment and dehumidifier equipment, and could not achieve the desired control effect. This design uses s7-1200 programmable controller and MM440 frequency converter to control the frequency conversion of dehumidifier and chiller. The contactor is used to control the start and stop of cold water pump, cooling tower and cooling fan equipment. The system collects the temperature and humidity values of the refrigeration workshop, and realizes the automatic adjustment and control of temperature and humidity through PID adjustment. It is designed in manual and automatic ways.

According to the development and design steps of PLC system, it is divided into the overall design of control scheme, hardware selection and drawing design, software flow and ladder diagram design. The ladder diagram is simulated through system debugging. The design idea of the system is PID control. The powerful compiling function of the application programming software has completed the partial design of the function. The system has high reliability, good stability and good feasibility, which meets the automation control requirements of the air conditioning control system in the refrigeration workshop.

Key words: Refrigeration workshop air conditioning, PLC design, hardware construction, system debugging