Nonlinear robust temperature-humidity control in livestock buildings

The physical environment of farm animals inside livestock buildings is primarily characterised by hygro-thermal parameters and air quality. These parameters are influenced by the interaction with the outdoor situation on one hand, and the livestock, the ventilation system and the building on the other hand. Livestock housing must ultimately provide environmental conditions favorable to the preservation of animal health and welfare and, consequently, to the efficiency of animal production. To reach the best environmental conditions inside a building, it is necessary to apply advanced control systems and effective control techniques. In this paper, such a new control technique is presented. In particular, the use of robust nonlinear feedback control in conjunction with feedforward action, in order to assure arbitrarily small deviations in the desired temperature and humidity values in an animal building, is described. This method results in a controller whose characteristics depend on knowledge of the bounds of the uncertain elements in the system description. The method is illustrated by simulation studies for a contemporary pig house during summer and winter operation.