A framework for disturbance attenuation on SISO stable/unstable systems

This paper presents a generalization of the internal model control (IMC) approach to feedforward control action generation. As it is well known, one of the distinctive features of the IMC formulation is the possibility to distinguish between the nominal and uncertain situation. However the consideration of the presence of uncertainty for the feedforward part of the controller is not as simple as it is for the feedback one. In this sense, what is proposed in this communication provides a more sistematic way of addressing a robust feedforward design. In addition, being one of the major drawbacks of the internal model control is to have to deal with stable systems, the generalization presented here allows for unstable plants as well as unstable disturbance models.