Identification of non-stationary continuous systems using modulating functions
Abstract The identification of non-stationary multi-input multi-output continuous systems by the use of trigonometric modulating functions is considered. The time variable matrices to be identified are developed in polynomial form, and the fact that the product of a modulating function with these series also gives a modulating function is discussed. The proposed method avoids the necessity of knowledge and estimation of the initial conditions and signal derivatives.
In this paper, we study the oscillations of a kind of second-order nonlinear delay differential equations with variable sign oscillation factors. Three sufficient conditions about the equation are obtained, which generalize the present oscillation results of second-order nonlinear differential equations and delay differential equations with invariable sign coefficients.