Numerical Simulation Of A Cascade Control System Of Indoor Temperature PI~?D~? And Indoor Supply Air Volume PI~? For A Variable Air Volume Box

At present,with the improvement of people's living standard,the utilization of air conditioning systems has spread among thousands of households.As one of the most critical components of variable air volume air conditioning system,variable air volume box(VAV-Box)installed in an air conditioning room is usually controlled by the modes of integer order PID or PID-PI cascade,which results in the problem of longer regulation time and larger steady state error and overshoot for indoor temperature belonged to one of the key parameters of an air conditioning room,and hence it is difficult to meet the requirements of air conditioning technology and to achieve the desired control effects.In view of these problems,this paper presents the ideas of designing a cascade control policy of fractional order PID controller for indoor temperature(IT-FOPIDC)and fractional order PI controller for indoor supply air volume(ISAV-FOPIC)and modified seeker optimization algorithm(MSOA)for tuning parameters of these two controllers for the basic pressure type independent VAV-Box.In addition,Smith compensator is adopted to improve the stability of this fractional order PID cascade control system.So the desired control effects and the air conditioning indoor comfortable degree can be achieved,respectively.Firstly,the transfer functions of all components of this fractional order PID cascade control system are set up,respectively.Secondly,by varying the inertial weight w of standard seeker optimization algorithm(SSOA),an MSOA is reconstructed to continously tune the optimal values of eight parameters of these two controllers.According to the varation of outdoor temperature,a fresh air temperature compensator outputs the set value of indoor temperature in order to implement the servo regulation of indoor temperature.Finally,this fractional order PID cascade control system is configured and the corresponding numerical simulation is carried out by MATLAB\Simulink tool,respectively.The results show that the proposed fractional order PID cascade control system whose controllers'paramaters are tuned by MSOA is feasible in theory,and the corresponding control indexes can meet the relevant requirements of the air conditioning technical processes.The corresponding main research contents in this paper are given as follows:1.Based on the basic theory of fractional order PID control,an improved Oustaloup filtering algorithm is adopted to design the fractional order PID controller,and the modules of PI~?D~?and PI~?controllers are constructed and their functions are packaged by using Simulink module.The performnace of PI~?D~?controller is prior to that of PID one through the verication of examples in the existing literature.2.On the basis of analysizing the operation technology for the basic pressure type independent VAV-Box and the related automatic control technology,the fractional order PID cascade control policy is determined by considering IT-FOPIDC and ISAV-FOPIC as primary controller and secondary controller,respectively.The controlled plant of indoor temperature,measuring transmitters of fresh air,indoor temperature and indoor supply air volume,PI~?D~?primary controller for indoor temperature,PI~?secondary controller for indoor supply air volume and actuator for indoor supply air volume are modeled,respectively.And the calculations of the cooling and heating load and the supply air volume in the air-conditioning areas and the type selection for the main equipments are carried out.3.By varying the inertial weight w of standard seeker optimization algorithm(SSOA)with nonlinear and exponential function,an MSOA is reconstructed to tune the parameters the above IT-FOPIDC and ISAV-FOPIC.The convergence and diversity of this MSOA is verified by the classical function example;Furthermore,a modified integral-time-absolute error(MIATE)is selected as fitness function J for this MSOA.By means of the numerical simulation of the unit closed-loop negative feedback PID control system and the experimental varification of the PID control system for water tank's level,this MSOA with fitness function J is feasible to tune the PID controller's parameters.4.By Simulink tool,the simulation model of the proposed fractional order PID cascade control system whose controllers'paramaters are tuned by MSOA is set up under the operating conditions of air-conditioning in winter and summer,and the corresponding numerical simulation is carried out.It is seen that the control effects are better and the optimal values of eight parameters of IT-FOPIDC and ISAV-FOPIC are obtained.5.For the same controlled plant with VAV-Box for indoor temperature,the simulations of the four other control methods,i.e.,PID single loop,PI~?D~?single loop,indoor temperature PID-indoor supply air volume PI cascade and indoor temperature PI~?D~?-indoor supply air volume PI cascade are implemented,respectively.By analysizing the related results,the proposed fractional order PID cascade control system whose controllers'paramaters are tuned by MSOA is superior to other control systems.