A modeling of an environmental chamber

This paper describes a modeling procedure for an environmental chamber as a typical example of an air conditioning system taking a multivariable autoregressive (AR) model into account by using the experimental data of a real plant. In this air conditioning system, the output variables are the room temperature and room humidity; the input variables affecting these outputs are considered to be the opening of the cooling water valve, the currents of the heating and humidifying heaters, the temperature of the supply cooling water, the outdoor temperature, and the outdoor humidity. To determine the input/output relation, the cross-correlation functions among these variables are examined. The principal component analysis is carried out to obtain the simplest model possible and to determine adequate output variables. The selection of input variables is achieved by considering the relative power contribution to output variables. A simple three-input/two-output model can be easily obtained. To verify whether the input/output relation obtained by this modeling procedure indicates adequate physical characteristics of the real air conditioning system, the step response and the simulation of the model are calculated. Agreement between the calculated values for output variables and the experimental responses is generally good. This shows the practical utility of themore » modeling procedure on which the design of more sophisticated control is based.« less