Rejection of Unknown Sinusoidal Disturbances in Non-minimum-phase Nonlinear Systems

This paper deals with disturbance rejection with stability based on the estimated state and disturbances. The unknown disturbances are combination of sinusoidal disturbances with unknown frequencies, unknown phases and amplitudes. The only information of the unknown disturbances is the number of distinctive frequencies inside. The class of nonlinear systems considered in this paper consists of nonlinear systems in the output feedback form and the systems are nonminimum phase, ie, with unstable zero dynamics. Based on the adaptively estimated disturbances, a new control design is proposed for stabilization and disturbance rejection of the nonlinear system in output feedback form which has a nonminimum phase zero.Copyright c ©2005 IFAC