Abstract
In this paper the existence and uniqueness theorems are derived for the equation describing a feedback system consisting of a nonlinear element f and a linear element g which involves the unit step function and the delta functional with its derivatives. The conditions of the theorems are easily verified in the frequency domain using the locus which is defined by the Fourier transform of the linear element. The essential part of the method in the theorems is to transform the distributional equation to an ordinary nonlinear Volterra type integral equation and apply the known theorems of the integral equations to the equation obtained by the transformation.
