Numerical Simulation Of A Fractional Order PI~λD~μ Decoupling Controller For Temperature And Relative Humidity In An Air-Conditioning Room And Its Performance Analysis

The technologies of air-conditioning and automatic control play an important role in maintaining a good heat moisture environment and meeting the related comfort degree demand for people in the rooms.Because of the complicated and dynamic characters of indoor temperature and relative humidity plant with large inertia,large time-delay and couple,etc,some classical control technologies and their applications,such as an integral order PID control system for indoor temperature and relative humidity,its control effect is not ideal.Thus,how to design the reasonable new types of controllers for indoor temperature and relative humidity is always one of research hot issues in the field of the control theory and technology associated with air-conditioning parameters in order to respond quickly,overcome the disturbance from indoor heat and moisture and meet the air-conditioning technological requirement of keeping indoor temperature and relative humidity stable.On the basis of theories of fractional order calculus,decoupling control and PID control technology,aiming at the characters of indoor temperature and relative humidity plant with large inertia,large time-delay,time-varying and couple,etc,this paper proposes a decoupling control algorithm for the control channels of indoor temperature and relative humidity,a scheme of designing the fractional order PID controllers for indoor temperature and relative humidity and its controller parameter’s tuning method.In addition,Matlab software is considered as a numerical analysis tool to dynamically simulate this fractional order PID controller for indoor temperature and relative humidity and its control effect.The change regularity of indoor temperature and relative humidity that can characterize this control system’s performance.The main research results in this paper are as follows.1.Based on the mechanism and modeling method,the input and output characteristics of indoor temperature and relative humidity plant,air handling unit,measurement units for indoor temperature and relative humidity,actuators and controllers are analysized and then the corresponding transfer functions for the indoor temperature and relative humidity plant,the measuring channels of indoor temperature and relative humidity,the control channels of cold and warm water flow and the control channel of steam humidification flow are set up,respectively.2.By means of the parameter’s tuning method for an integral order PID controller,the discussion for the effect of variety for λ and μ on the control results is done theoretically.Moreover,the suitable values of λ and μ are attained by the step response outputs of the controlled plants via the numerical simulation.3.For the strong coupling effect existing in the control channels between indoor temperature and relative humidity,the corresponding decoupling algorithm is designed by the method of feed-forward compensation,which can make the whole control system for indoor temperature and relative humidity divide into two control subsystem.So the tuning tasks for Kp,KI,Kd,λ,μ are executed for the fractional order PID controllers for indoor temperature and relative humidity,respectively.4.Since the performance of PIλDμ controllers mainly depends on the values of their five control parameters,according to the control objective of air-conditioning technological errors for indoor temperature and relative humidity,an iterative and incremental change algorithm of tuning control parameters is also presented so as to obtain the optimal values of five control parameters(Kp*,KI*,Kd*,λ*,μ*)for indoor temperature and relative humidity PIλDμ controllers,respectively.Using Simulink interface of Matlab software,the configure and numerical simulations for the proposed PIλDμ decoupling controllers are executed under refrigeration and heating modes of air-conditioning.The results show that this PIλDμ decoupling control system for indoor temperature and relative humidity is feasible in theory and the corresponding control indexes meet the air-conditioning technological requirements.5.For the same controlled plant with indoor temperature and relative humidity under refrigeration and heating modes of air-conditioning,the relevant numerical simulations for the different methods of PIλDμ decoupling,PID decoupling and PID are executed,respectively.The proposed PIλDμ decoupling controllers and ites control system are superior in the performance indexes including overshoot,ratio of attenuation,control accuracy,regulation time,etc.in terms of numerical simulation results and their comparison.