Global output tracking and rejection of multi biased sinusoidal disturbances with unknown frequencies for nonlinear systems

Global output tracking and rejection of multi biased sinusoidal disturbances with unknown frequencies for nonlinear systems is considered. Disturbance observers (DOBs) in the form of a high pass filter are proposed to estimate multiple biased sinusoidal disturbances with unknown frequencies. The nonlinear control method is designed to compensate the estimation errors of the disturbances and guarantee the global output tracking. The matching conditions is no significant in the proposed method. The proposed method imposes no restriction on the number of disturbances, and no restriction such as biased sinusoidal signals. Therefore, the complete rejection of multi sinusoidal disturbance with stabilization can be achieved by the proposed method.