High-gain fractional-order controller for output tracking and disturbance attenuation in a class of Lur'e systems

Abstract

This paper addresses the problem of output tracking and attenuation of unknown disturbances acting on a class of nonlinear systems that consists of a forward path containing a linear, time-invariant element and a feedback path with a sector-bounded nonlinearity. Under the hypothesis that the frequency response of the linear block belongs to a half-plane, passing through the origin of the complex plane and forming an angle in [0,p/2] with the positive imaginary axis, a high-gain fractional-order controller is proposed to guarantee absolute stability of the nonlinear system. Numerical simulations demonstrate the properties of the method in a variety of conditions.