基于PLC的食品杀菌通信和温度控制系统设计.doc

基于PLC的食品杀菌通信和温度控制系统设计 摘要 关键词：食品杀菌；温度控制；PLC通信；PID调节 Based on PLC food sterilization communication and temperature control system design Abstract It is well known that temperature is a very important parameter in industrial production and scientific experiments. Many physical and chemical properties are related with temperature. Many production processes work in some certain temperature range, so temperature needs to be measured and controlled effectively. Aiming at the problem that it is difficult to control temperature in food sterilization process, PID controller in PLC software was adopted to overcome it in the paper. In the industrial production, closed-loop control is usually used to control temperature, pressure, flow and other continuously variable analog quantities. In order to make the system stable and accurate, not only analog quantities need to be sampled and measured, but also the sample result need to be computed with PID algorithm, then according to the results of operations, analog can be controlled effectively. The PLC of Siemens S7-200 as a main control device was adopted in the paper, to implement the control precisely in food sterilization control system, and implement the function of communication between PLC. It is convenient to deal with the control of analog with PID loop instruction of S7-200PLC. The whole design process of PID controller in food sterilization temperature control system was introduced. The programming instructions of PID function in PLC were used to realize temperature control of food sterilization to meet the control needs of system. Key words：ood sterilization; temperature control; PLC communication; PID adjustment 目录 摘要 I Abstract II 1 绪论 1 1.1 课题背景和意义 1 1.2 课题发展现状和趋势 1 1.3 课题研究内容和论文简介 2 2 PLC和STEP7介绍 4 2.1 可编程序控制器的基础 4 2.1.1 可编程序控制器的产生和应用 4 2.1.2 可编程序控制器的组成和原理 4 2.1.3 可编程序控制器的分类和特点 7 2.2 STEP7介绍 7 2.2.1 STEP7概述 7 2.2.2 硬件接口与项目结构 8 2.2.3 模块简介 9 3 食品杀菌控制系统硬件设计 11 3.1 PLC控制系统设计的基本原则和步骤 11 3.1.1 PLC控制系统设计的基本原则 11 3.1.2 PLC