Air Temperature Control Of Air Conditioning System

With the progress of science,technology,and quality of life,air conditioning system has been widely used.Although it has brought great convenience for people,the energy problem can not be underestimated at the present stage of energy shortage.Air handling unit is an important part of energy consumption in air conditioning system.Therefore,the research on controlling of air handling system is of great practical significance.In this thesis,the air conditioning system of constant volume central air conditioning system is taken as the research object,and the problem of controlling temperature of outlet air of the surface cooler is studied.Based on summarizing a large number of domestic and foreign literatures and analyzing the present situation of modeling and controlling problems of the air handling system,a nonlinear model with two state variables and two input for dynamic heat transfer of surface cooler is established.For considering the influence of inlet temperature and rate of flow of chilled water on the air temperature of outlet of cooler at the same time,it has improved and covered the traditional single input and single output model.Based on the analysis of the model in the thesis,two kinds of controller design strategy are proposed to solve the problem of nonlinear and uncertain model parameters.One is the fuzzy controller to adjust the air temperature of the cooling device.The method does not require the accuracy of the mathematical model.The other is the robust controller.The mathematical model is linearized and the uncertain state space model is generated,and the air temperature regulation problem is transformed into a robust tracking problem.The robust controller is designed,which can overcome the influence of system uncertainty,and ensure the system has good robustness in the presence of parameter perturbation.In the MATLAB environment,the two control systems are simulated.It is proved that the fuzzy controller is robust,and has wide range,and the robust controller can overcome the influence caused by the uncertainty of the model.Furthermore,a fuzzy and robust switching control strategy is proposed,which combines the fuzzy controller and the robust controller,and by which the fuzzy controller is used in large error situation while the robust controller is used in tiny error situation.The switching control strategy makes the system have better control effect.