| The air conditioning systems adopting fan coil units(FCUs)have been widely used in the buildings including offices,hotels and apartments because of the characteristics of their compact size,easy installation,convenient operation and decentralized control,etc.As the terminal device of semi-central air conditioning system,the operation effect of FCU directly affects whether the important indoor air parameter-indoor temperature meet the air-conditioning technological accuracy.Furthermore,the automatic control modes for FCU play a decisive role in its operation effect.However,the present automatic control modes for FCU,for example,a single-loop method of indoor temperature integer order PID control varies the opening of cold and hot water actuator to control the indoor cooling or heating load on the basis of indoor temperature error in order to achieve the requirements of steady indoor temperature.This control mode may lead to the problem of larger indoor temperature steady-state error,overshoot,and long adjustment time,etc.because of the dynamic characteristic such as large inertia and time-delay.According to the above problems,combining with the relevant requirements of air-conditioning process and fractional order PID control technology,this paper presents a research idea of designing indoor temperature fractional order PID controller(denoted as IT-FOPIDC)and sending air volume PI controller(denoted as SAV-PIC).For tuning parameters of these two controllers,an improved ant colony algorithm(IACA)is also proposed to obtain the optimal values of seven parameters.Based on the numerical simulation of indoor temperature PI~?D~?and supply air volume PI compound control system,the results of steady indoor temperature.and better comfortable degree are achieved by means of controlling the valve opening of chilled and hot water actuator and the indoor cooling or heating supply air volume synchronously.The main contents of this paper are as follows:1.On the basis of basic theory of fractional order PID control,an improved Oustaloup algorithm is adopted to design the fractional filter.In addition,the PI~?D~?controller and objective function ITAE are packaged by using Matlab/Simulink module.2.Through the related mechanism analysis of air-conditioning and automatic control technology,an indoor temperature plant and cooling and heating coil unit,an indoor temperature measuring transmitter,chilled and hot water flow regulating valve,fan and its frequency converter,the indoor temperature PI~?D~?controller,and supply air volume PI controller are modeled,respectively.An IACA that is suitable for tuning the parameters of these two controllers is presented in terms of varying evaporation factor?with an exponential function.The related results from verification on classical functions and level control experiment of a water tank show that this IACA is feasible.3.Under the operating conditions of air-conditioning in winter and summer,the optimal values of seven parameters of IT-FOPIDC and SAV-PIC are obtained by IACA.This compound control system is configurated by Matlab/Simulink tool and then the corresponding numerical simulation is performed.The results show that this compound control method with indoor temperature and supply air volume can make the FCU system meet the control requirements of air-conditioning technological indexes.4.For the same indoor temperature plant of air-conditioning room and air-conditioning control indexes,the numerical simulations of indoor temperature PI~?D~?single-loop control mode and compound control mode of indoor temperature PID and supply air volume PI are also carried out.Through analysis of the above numerical simulation results,it can be seen that the control performance of this compound control system of indoor temperature PI~?D~?and supply air volume PI such as shorter adjusting time and less overshoot is obviously prior to that of the other two control methods. |
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