Implementation of FemLab in S-Functions

FemLab has standard facilities to export models to SimuLink. Normally, the standard export works well if the solvers, available in SimuLink, can handle the problem. However, if a model in FemLab needs special solvers, for example airflow or other non-linear problems, the standard export to SimuLink is often not suitable, because the standard solvers of SimuLink cannot handle such a problem efficiently. This can cause long simulation duration times and even leads to no solution at all. The paper presents a possible solution to this problem by implementing FemLab code in the discrete section of a SimuLink S-Function. The S-Function solves each time step the non-linear problem using the FemLab solver. After each time step the solution is exported. Furthermore, different boundary values can be applied at will. The implementation of FemLab code in a S-Function is demonstrated by a case study, where the airflow temperature at the inlet of an office is controlled by an on/off controller in SimuLink. The results show: (1) the dynamic interaction of the airflow in the room and the controller and (2) details of how a S-Function can be programmed using FemLab. It is concluded that FemLab models can also be exported to SimuLink by writing an appropriate S-Function. The advantage of this approach is that the special solvers of FemLab can be used in the SimuLink environment. This can lead to significant improvement of the simulation duration time.