On the computation of Lyapunov functions for interconnected systems

This paper addresses the computation of additively separable Lyapunov functions for interconnected systems. The presented results can be applied to reduce the complexity of the computations associated with stability analysis of large scale systems. We provide a necessary and sufficient condition for the existence of an additively separable Lyapunov function; subsequently, sparsity conditions are given for finding additively separable polynomial Lyapunov functions for both local and global stability of polynomial systems.