We demonstrate the existence of Lur'e-Postnikov type Lyapunov functions for a reasonably general form of the multivariable Popov criterion. In particular, the multipliers need not be positive semi-definite. We discuss the application to the special cases where the feedback element is either diagonal, unstructured or linear. © 2009 Elsevier Ltd. All rights reserved.
- Lyapunov functions
- Multivariable feedback systems
- Popov criterion
- Stability tests