The Research And Application Of The Distributed Temperature And Humidity Computer Control System

The controlling of temperature and humidity is a necessary part of public engineering in tobacco industry, chemical fiber industry, textile mills and modern buildings. In tobacco industry, the quality of tobacco largely depends on the performance of a set of air-conditions, for the surrounding temperature and humidity condition always puts a directly effect on the quality of tobacco produced. This project is set forth for the renovation of industrial air-conditioning in XiChang cigarette factory. The main task involves: developing a temperature and humidity automatic control system based on computer control theory, resolving the problem of dropping dews, center-watching and distributive-control of air-condition systems. The completion of the following tasks is indispensable to this project:1. Automatic control model of temperature and humidity. A temperature and humidity control model is developed, which is suitable for computer control. With the fuzzy theory and the dew point confined, the system can automatically adjust the surrounding temperature and humidity in the workshop to the set-point, no matter what the outside condition is, such as the change of temperature in winter or summer, in day or night, and the asymmetry of the machine and the pyrotoxin. The system will adjust the surrounding temperature (within the range of+ 1C of ideal degree) and humidity (within ?4%) quite accurately.2. Single distributed control system. The control box of workshop is designed. The CPU226 of S7-200 PLC is selected as the computer on the spot. The software package of Step7-MicroWIN is used for programming. The TD200 is chosen as the Human Machine Interface (HMI), by which users can set control parameters and monitor the state of control valves and the temperature and humidity condition in workshop. The knobs in the control box are used for debugging, examining and repairing the system.3. Realization of center-monitor by PC and PLCs networks. The communication processor CP5611 is used as the data link between PC and PLCs in PC application, which is based on the software package Visual Basic and SQL server and developed for monitoring the temperature and humidity condition in workshops.4. Integrated into enterprise information network. The center-control computer functions as web server. A set of web pages is programmed for the realization of sharing information in enterprise and for long-distance monitoring of temperature and humidity condition in workshops.