Periodic systems with drift. I. Modeling and identification

This paper proposes a harmonic-like decomposition to represent periodic systems with drift in either the period itself or the inter-period behavior, or both. The system is decomposed into two factors: a memoryless system-meant to represent the instantaneous period-and a slowly time varying system-meant to represent any drift in the inter-period behavior. The factorization is appropriate for real-time applications since it allows for on-line period updating. A general structure for real-time identification based on the proposed decomposition is also discussed