State Feedback Repetitive Control Design: Robustness and Load Disturbance Conditions

Abstract

A Repetitive Control (RC) in state feedback structure that includes past error feedforward and current error feedback schemes is discussed for linear time-invariant systems. The design is reported in previous works where it relates the RC design to a dual controller know as the Iterative Learning Control (ILC) for periodic reference/disturbances accommodation. The revised design basically focuses on finding the overall transfer function around an isolated delay model (representing periodic disturbances) with the use of the small gain theorem as a condition to assure system stability and reference tracking. The design suffers of not to include uncertainty issues and load disturbances effect. This paper reintroduces the design of the RC controller within the state feedback in the presence of both past error and current error structures. The robustness conditions are investigated and set to enhance system performance in the presence of modelling mismatch as well as setting sufficient conditions for load disturbance limitations are the novel contribution of this paper. Simulation results obtained show the advantage of the robust conditions obtained in improving system performance in case of dynamic perturbation.