Numerical Simulation Of PI~?D~?-PI Cascade Controller Parameters Tuning Based On IPSA-DE Algorithm For Variable Air Volume Terminal

The variable air volume air conditioning system?VAVACS?,in comparison with the constant air volume air conditioning system?CAVACS?,has been widely used because of its characteristics such as saving electricity consumption of air handling units,flexible arrangement,and convenient management,etc.The running effect of a variable air volume terminal?VAV-TMN?that is an important composition of the corresponding VAVACS directly affects the indoor temperature precision required by air conditioning technique,and the corresponding automatic control methods play a decisive role in the running effect of the VAV-TMN.At present,the methods of integer order PID single closed loop and PID-P cascade control are usually adopted for the VAV-TMN in an air-conditioning room,which brings about the problems of larger control error and overshoot of indoor temperature and the longer adjustment time,etc.Aiming at the above problems,on the basis of theory of fractional order calculus,PID control technology,and variable air volume air conditioning technique,this paper presents a design method of a cascade controller of indoor temperature fractional order PID?IT-FOPID?and sending air volume integer order PI?SAV-PI?for the VAV-TMN in an air-conditioning room.Meanwhile,an improved parameter self-adaptive differential evolution?IPSA-DE?algorithm is proposed for the tuning problem of seven parameters of this cascade controller of IT-FOPID and SAV-PI and the corresponding cascade control system of indoor temperature and sending air volume for the VAV-TMN in an air-conditioning room is set up.The main research results in this paper are as follows.1.Based on the work mechanism of the VAV-TMN and the corresponding automatic components,the input and output characteristics of indoor temperature plant,measurement units for indoor temperature and sending air volume,sending air volume actuator?SAVA?,indoor temperature fractional order PID controller?IT-FOPIDC?,and sending air volume PI controller?SAV-PIC?are analysized,respectively,and then the corresponding transfer functions are modeled.2.By self-adjusting variable factor F and interleaving factor CR in the standard differential evolution algorithm,the IPSA-DE?Improved Parameter Self-adaptive Differential Evolution,IPSA-DE?algorithm is proposed in this paper.The results in examples indicate that this IPSA-DE algorithm can effectively overcome the premature convergence problem in the traditional differential evolution algorithm and obtain the global optimal values of the corresponding parameters.3.On the basis of the proposed IPSA-DE algorithm,the parameter tuning method of integer order PID controller,and the desired objective function J,an iterative parameter tuning method is designed for the main controller?IT-FOPIDC?and the secondary one?SAV-PIC?and the reasonable scopes of seven parameters K_P,M*,K_I,M*,K_D,M*,?*,?*,K_P,A*and K_I,A*are determined.4.Under refrigerating and heating modes of air-conditioning,the optimal values of seven parameters are set into IT-FOPIDC and SAV-PIC,respectively.Accordingly,the configure and numerical simulations for the corresponding cascade control system of indoor PI^?D^?plus sending air volume PI for VAV-TMN in an air-conditioning room are executed via simulink interface of Matlab software.The results show that this cascade control system of indoor temperature PI^?D^?plus sending air volume PI is feasible in theory and the corresponding indexes of indoor temperature and sending air volume meet the air-conditioning technological requirements.Moreover,this cascade control system with the added Smith forecast compensator has an obvious advantage to overcome the time-delay of the temperature control channel.5.For the same air-conditioning room equipped with VAV-TMN under refrigeration and heating modes of air-conditioning,the relevant numerical simulations for the different control methods of indoor temperature PI^?D^?single closed loop,indoor temperature PID single closed loop,and indoor temperature PID plus sending air volume PI cascade closed loop are executed,respectively.By means of numerical simulation results and their comparison,both the proposed cascade controller of indoor temperature PI^?D^?plus sending air volume PI and the corresponding control system are superior in the performance indexes including the control precision of indoor temperature,overshoot,steady state error,regulation time,and sending air volume,etc.