Some new results on the stability of direct-form digital filters with finite wordlength nonlinearities

Abstract

This paper proposes a new criterion for the input/output-to-state stability (IOSS) of interfered direct-form digital filters with finite wordlength nonlinearities based on an augmented Lyapunov function. Without external interferences, the output-to-state stability (OSS) and asymptotic stability of direct-form digital filters are guaranteed under the proposed criterion. An improved criterion is also proposed for the IOSS and OSS of interfered direct-form digital filters, with the introduction of four slack matrices. A new state-norm estimator for direct-form digital filters is constructed based on an exponential-decay IOSS criterion. The criteria presented in this paper are expressed by linear matrix inequalities (LMIs). Two numerical examples demonstrate the effectiveness of the proposed results. (C) 2014 Elsevier B.V. All rights reserved.