Design and Analysis of the Modified IMC Filter for Disturbance Rejection

Design of the classical control system is usually focused on the stability and quality of the control processes or disturbances rejection. Such a controller then rarely satisfies both requirements. Presented modification of the control system then makes possible to satisfy both of them. Two methods are used: elimination and internal feedback. Based on the analysis of the first of these methods, we point out the limits of this approach. We also show the method for a recalculation by the second possibility of the disturbance rejection. Generalization of such obtained results leads to the general structure and parameters of the controller with suitable behavior both for control and disturbances. One of its advantages is the possibility to control also the unstable processes with an integrator and deadtime. It is also possible to use it e.g. for tracking or rejecting various input signals, namely the positioning step. This is a general structure, including also the well-known controllers as Smith predictor and its modifications, Internal Model Control etc.