A dynamic nonlinear model of a thermostatic valve

An experimental setup of a water based central heating system has been used to measure the thermo dynamical behavior of a thermostatic valve in order to identify an adequate mathematical model. The identification of the thermostatic valve is based on nonlinear Grey-Box modelling. Grey-Box modelling is characterized by the fact that, in the modelling procedure, partial known information from physics about a system is combined with information from data. The parameters of the model are estimated by a Maximum Likelihood Method. In the paper an overview of this modelling procedure is given. The estimated model of the applied thermostatic valve is a first order differential equation with a static non-linear output description. The presented results constitute a part of a research project, where the primary goal is to establish a collection of dynamic models for the components of water based central heating systems in single family houses.