Design of Discrete Time Repetitive Controllers with Applications to Mechanical Systems

Abstract

In many mechanical systems such as robots, machine tools or disk drives the control task is repetitive. In such a case, the reference and disturbance inputs to the system are periodic. This paper considers the design of robust discrete-time repetitive controllers that allow the plant to track the periodic reference input while rejecting the periodic disturbance input. The cancellation of the periodic disturbance implies that a periodic signal generator, or disturbance model, must exist. Two forms of discrete-time repetitive controllers will be examined; those that place the disturbance model inside the feedback loop and those that place it outside the feedback loop. Implementation results demonstrate that a repetitive controller can be used in a plug in fashion to augment an existing controller.