Robust tracking control design to nonlinear plants with perturbation using operator-based observers

In this paper, a robust tracking control design for nonlinear plants with perturbation is considered by using operator-based observers and robust right coprime factorisation approach. In real situations, there exist unknown uncertainties consisting of modeling errors and external disturbances. The robust right coprime factorization approach is convenient in researching input-output stability problems of nonlinear system with uncertainties. Based on the above considerations, an operator-based robust nonlinear perfect tracking control by using robust right coprime factorization is presented. That is, first, considering the fact that the uncertain plant is unknown generates difficulties in designing realizable operator controllers to obtain the desired tracking performance, an operator-based feedback control scheme is proposed, and an operator disturbance observer and an operator state observer based on nominal plant properties are designed to compensate the effect of uncertain plant. Second, a realizable operator-perfect tracking controller is design to improve the control performance and to realize the perfect tracking. Based on the proposed design scheme, the designed system is robustly stable. Also, output tracking performance can be realized. Finally, the effectiveness of the proposed design scheme is demonstrated by a simulation example.