Selection of Variables in Initialization of Modelica Models

In Scicos, a graphical user interface (GUI) has been developed for the initialization of Modelica models. The GUI allows the user to fix/relax variables and parameters of the model as well as change their initial/guess values. The output of the initialization GUI is a pure algebraic system of equations which is solved by a numerical solver. Once the algebraic equations solved, the initial values of the variables are used for the simulation of the Modelica model. When the number of variables of the model is relatively small, the user can identify the variables that can be fixed and can provide the guess values of the variables. But, this task is not straightforward as the number of variables increases. In this paper, we present the way the incidence matrix associated with the equations of the system can be exploited to help the user to select variables to be fixed and to set guess values of the variables during the initialization phase.