A frequency-domain approach to bifurcations in control systems with saturation

Bifurcation analysis of nonlinear control systems supplies a global perspec tive of the system behaviour modes. In this paper, it is shown that this an alysis can be implemented with very elementary and classical tools, such as frequency-dom ain graphical methods. The methodology proposed is illustrat ed analysing the effects of a saturation non-linearity on a system designed with a linear control law. The full morphology of qualitative behaviours a nd of polar plots for two-dimensional systems is displayed, pointing out ho w bifurcations give rise to the boundaries between regions with different q ualitative behaviour modes. Also a case of a three-dimensional system is an alysed.