In this paper, we propose a new approach to the robust stability and instability analysis for uncertain nonlinear systems. In our previous work, several criteria for the stability, instability, and robustness are given under the assumptions that the location of the equilibrium is not shifted by the uncertainty. However, the assumption does not hold for realistic systems in general. Therefore, we explicitly consider the uncertainty-dependent equilibrium and propose new robustness analysis methods for the stability and instability of uncertain nonlinear systems. Finally, illustrative examples for stability and instability analysis of an uncertain genetic network model are presented.
