The Degign And Application Of DCS Based Cleanroom Facilities Monitoring And Controlling System

cleanroom technology became an important technology and was hold in high regard.For semiconductor IC manufacturing branch, one of the most important function of cleanroom is to provide supply air with proper temperature, humidity and pressure which contact the production surface (silicon wafer), so that can provide good environment for production. Cleanroom environment control is performed under the co-ordination of air handling system, exhaust system, fan filter unit and power distribution system. So how to design an advanced and high performance cleanroom facility monitoring & control system will be a core question for discussion during the cleanroom design and construction phase.This thesis is based on one facility monitoring & control system project for wafer foundry plant. Based on the specific requirement of the project, the controlled object and control effect of cleanroom facility monitoring and controlling system is analyzed first, and the characters of cotrolled object is discussed in further, the control strategy for facility monitoring & control system is discussed in further, also a control system proposal based on SIEMENS PCS7 distributed control system is carried out.Regarding the control strategy, the discusstion is focused on cleanroom make-up air unit, cleanroom temperature and humidity control is the key point for research. By analyzing the air handling process on psychrometric chart, a method for opening the coupling between temperature and humidity is applied and PID cascade control strategy is given out and applied to temperature and humidity control. In order to achieve accurate room pressure value control, adopt invariable exhaust fan flow and control the speed of makeup air fan, so that the room pressure can be kept in invariablenes. Concerning the requirements of accuracy and energy saving, the VFD of makeup air unit is controlled via sensible instrument devices like differential pressure meter and air flow meter, so that the air flow of makeup air unit is well regulated.Aim at the disadvantage of general PID control during the commissioning and operation, this thesis research and design a mixed Fuzzy-PI controller for high precision cleanroom humidity control. Through theory analysis and simulation, discuss the reliablility of Fuzzy control applied in cleanroom control system.Further more, introduce how to make DCS software configuration under PCS7 system. Including: Use Structure Programing Language (SCL) to design project typical library; Use Continous Functional Chart (CFC) to make configuration; Use HMI configuration toolset to design operator station graphic. In view of the character of cleanroom facility monitoring and controlling system, develop PCS7 function block such as valve control, motor control etc。The facility monitoring & control system in this project is running in good status after plant start-up, the quality and performance of control system reached the design specification.