An error feedback model based adaptive controller for nonlinear systems

In this paper, a method of designing an adaptive controller is proposed to solve some problems in model reference adaptive control (MRAC) for nonlinear plants. The MRAC was originally designed for the unknown plant which should be linear and completely disturbance free. Practically, since real plants have nonlinearities, such as disturbances and unmodelled dynamics, the performance of the controller is worsened. This paper describes an error feedback model which is a reference model with the output error feedback, for improving robustness and stability to nonlinear characteristics. The proposed model can be used for MRAC using the measurable output of the plant and the states of the proposed model. Experiments on an SR (switched reluctance) motor have been done in order to illustrate the validity of the proposed controller.