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New IQC for quasi‐concave nonlinearities
Author(s) -
Megretski Alexandre
Publication year - 2001
Publication title -
international journal of robust and nonlinear control
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.361
H-Index - 106
eISSN - 1099-1239
pISSN - 1049-8923
DOI - 10.1002/rnc.622
Subject(s) - control theory (sociology) , mathematics , integrator , nonlinear system , passivity , saturation (graph theory) , limiter , computer science , bandwidth (computing) , engineering , control (management) , physics , computer network , telecommunications , quantum mechanics , combinatorics , artificial intelligence , electrical engineering
A new set of integral quadratic constraints (IQC) is derived for a class of ‘rate limiters’, modelled as a series connections of saturation‐like memoryless nonlinearities followed by integrators. The result, when used within the standard IQC framework (in particular, with finite gain/passivity‐based argiments, Lyapunov theory, structured singular values, etc.), is expected to be widely useful in nonlinear system analysis. For example, it enables ‘discrimination’ between ‘saturation‐like’ and ‘deadzone‐like’ nonlinearities and can be used to prove stability of systems with saturation in cases when replacing the saturation block by another memoryless nonlinearity with equivalent slope restrictions makes the whole system unstable. In particular, it is shown that the L 2 gain of a unity feedback system with a rate limiter in the forward loop cannot exceed \sqrt{2} . In addition, a new, more flexible version of the general IQC analysis framework is presented, which relaxes the homotopy and boundedness conditions, and is more aligned with the language of the emerging IQC software. Copyright © 2001 John Wiley & Sons, Ltd.