2009 JAN 6 - (VerticalNews.com) -- According to recent research published in the journal IEEE Transactions on Automatic Control, "This paper is concerned with the problem of robust H-infinity filtering for linear continuous-time systems with polytopic parameter uncertainties and time-varying delay in the state."

  "We utilize the polynomially parameter-dependent idea to solve the robust H-infinity filtering problem, with new linear matrix inequality conditions obtained for the existence of admissible filters. These conditions are developed based on homogeneous polynomially parameter-dependent matrices of arbitrary degree," wrote H.J. Gao and colleagues ...read more

  2009 JAN 6 - (VerticalNews.com) -- According to recent research from Hong Kong, People's Republic of China, "There has been renewed interest in the use of polynomial and homogeneous polynomial Lyapunov functions for addressing stability and performance issues in systems and control theory."

  "However, no condition is yet available to establish the convexity of these functions and the convexity of their sublevel sets, properties that can be useful in many applications," wrote G. Chesi and colleagues, University of Hong Kong ...read more

  2008 NOV 3 - (VerticalNews.com) -- "This paper describes a new approach to the synthesis of fixed-structure and fixed-order controllers. Such controllers are required in many practical applications," investigators in the United States report.

  "A broad class of fixed-structure controller synthesis problems can be reduced to the determination of a real controller parameter vector (or simply, a controller) K = (k(1), k(2), ..., k(iota)), so that a given set of real or complex polynomials of the form P (s, K) := P-o (s) + k(1)P(1) (s) + ... + k(iota)P(iota) (s) is Hurwitz. The stability of the closed-loop system requires a real characteristic polynomial to be Hurwitz, while several performance criteria can be satisfied by ensuring that a family of complex polynomials is Hurwitz. A novel feature of this paper is the exploitation of the interlacing property (IP) of Hurwitz polynomials to construct arbitrarily tight approximations of the set of,stabilizing controllers. This is done by systematically constructing sets of linear inequalities in K. The union of the feasible sets of linear inequalities provides an approximation of the set of all controllers K, which render P(s, K) Hurwitz. As the number of sets of linear inequalities increases and approaches infinity, we show that the union of the feasible sets approaches the set of all stabilizing controllers of the desired structure. The main tools that are used in the construction of the sets of linear inequalities are the Hermite-Biehler theorem, Descartes' rule of signs, and its generalization," wrote W.A. Malik and colleagues, Texas A&M University ...read more