A graphical environment for nonlinear system modelling and analysis

The paper describes a software environment that has been developed to allow the computer algebra software Mathematica to be applied to the analysis of a class of block-oriented nonlinear dynamic systems. Nonlinear system models are constructed using the graphical facilities of the simulation software SIMULINK and linked to Mathematica by MATLAB and MathLink programs under the control of a graphical user interface. Procedures developed in Mathematica are used to obtain the multidimensional transfer functions that relate the system output to the system input. These are then used to determine the time responses and the harmonic responses of the system. The method is illustrated for a feedback control system with a saturation characteristic in the forward path.