The Modeling And Study Of Control System For Variable Central Air-Conditioning

Along with living standards improving,more and more intelligent buildings come to truth. Air-conditioning as an important part of intelligent building abstracts people's more attentions. This thesis chiefly analyzes the characters of air-condition system,and set the model of central air-condition system.The writer analyzed the fuzzy control system,and applied the control system to the system of central air-condition temperature and humidity successfully.A satisfying result was achieved.In the paper,it is chiefly introduce the basic knowledge and principle of thermodynamic. The h-d chart is very important to the application of air-condition system,the author also introduce the h-d chart in chapter two.In order to study the system performance at the design stage,it is necessary to obtain approximate mathematical models for system components.In this thesis,the dynamic model for room is deriving by energy-conversation equations.The model of whole control system is created after achieving every component's model.The whole system include supply/retune fan,humidifier,heating coiling and cooling coiling,etc..There are stronger coupling between the air temperature and air humidity.Writer decoupled these two values by pressure,and then obtained the temperature responding model and pressure responding model.The system concludes the heat release and wet release that we can get the totally quantity of heat generated interior.In the paper the VAV system is a return air system,we can get the relations between outside air,exhaust air and return air through calculating the pressure differential between the dampers. The humidifier is designed based on Lewis relation and project approximate calculation.The general function of heat exchanger is to transfer heat from one fluid to another.The basic component of a heat exchanger can be viewed as a tube with one fluid flowing by on the outside.The simulation curve show that it is difficult to set PID parameters and avoid overtook.The fuzzy control has the character of well dynamic and robust.We can solve the time-delay problem by fuzzy controller. It is approved by simulation experiments that the fuzzy controller is an ideal method.It not only has little overshoot and quick response velocity,but also can overcome the disturbances including the changing of environment temperature or humidity.It has practical guiding effect and application value in theory research and engineering practice.Then it must have broad developing prospects.