ANALYSIS AND DESIGN OF 2 TYPES OF DIGITAL REPETITIVE CONTROL-SYSTEMS

Two types of linear digital repetitive control systems are designed and analyzed to reduce the error spectrum, including not only harmonic but also non-harmonic components. First, a novel gain adjusting algorithm is suggested for conventional and modified repetitive control systems with modelling uncertainties, in which the gain of the repetitive controller is adjusted to reduce the infinite norm of error in the frequency domain. For this, the relative error transfer function is newly defined as the ratio of the error spectrum for the system with a repetitive controller to the error spectrum for the system without a repetitive controller. Secondly, as an alternative to a repetitive control system with the gain adjusting, a repetitive control system with higher-order repetitive function is analyzed and designed, where the weightings of the higher-order repetitive function are determined in such a way that the infinite norm of the relative error transfer function is minimized. To shaw the validity of the proposed methods, computer simulation results are illustrated for a typical disk-drive head-positioning servo system.