Gray-box state-space model and parameter identification of desiccant wheels

A Desiccant Air Unit (DAU) may provide complete control of temperature and humidity in air-conditioned spaces. The key element of the DAU is the desiccant wheel. Its control needs models adapted to the analysis and synthesis of control algorithms. Such models can be obtained by a gray-box approach in which the structure of a state-space model and some of its parameters are derived from first principles and physical laws, while the rest of the parameters are experimentally identified. Identification procedure is simpler and more robust for linear models. In order to develop a non-linear model for the desiccant wheel, parameters of linear local models were first identified. Since the values of the parameters identified for the local models are almost the same, the nonlinear model does not bring more information than a simple and unique model that can be usefully used for control purposes.