A CAD tool for limit cycle prediction in nonlinear systems

The analysis of nonlinear control systems can be greatly improved by the use of computer software. In this paper, an interactive, user-friendly, graphically oriented toolbox based on Matlab is presented. Nonlinear systems whose nonlinearity is given by a relay are considered, and stability of free and forced oscillations is analyzed using the methods by Hamel, Tsypkin and Paquet. Nonlinear control systems with polynomial nonlinearity are also treated and analyzed using Hopf's theorem in the frequency domain. The structure of the code is described and some illustrative examples are presented to validate the software capabilities.