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Amir Ali Ahmadi(a_a_aprinceton.edu) Abstract: We show that existence of a global polynomial Lyapunov function for a homogeneous polynomial vector field or a planar polynomial vector field (under a mild condition) implies existence of a polynomial Lyapunov function that is a sum of squares (sos) and that the negative of its derivative is also a sum of squares. This result is extended to show that such sosbased certificates of stability are guaranteed to exist for all stable switched linear systems. For this class of systems, we further show that if the derivative inequality of the Lyapunov function has an sos certificate, then the Lyapunov function itself is automatically a sum of squares. These converse results establish cases where semidefinite programming is guaranteed to succeed in finding proofs of Lyapunov inequalities. Finally, we demonstrate some merits of replacing the sos requirement on a polynomial Lyapunov function with an sos requirement on its top homogeneous component. In particular, we show that this is a weaker algebraic requirement in addition to being cheaper to impose computationally. Keywords: Stability of nonlinear systems, Lyapunov functions, sum of squares, semidefinite programming Category 1: Applications  Science and Engineering (Control Applications ) Category 2: Linear, Cone and Semidefinite Programming (Semidefinite Programming ) Category 3: Nonlinear Optimization (Systems governed by Differential Equations Optimization ) Citation: IEEE TRANSACTIONS ON AUTOMATIC CONTROL, VOL. 62, NO. 10, OCTOBER 2017 (some additional details are included in this online version) Download: [PDF] Entry Submitted: 12/29/2017 Modify/Update this entry  
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