Handling Non-Periodic Disturbances In Repetitive Control Systems With Applications To Robot Manipulators

Abstract

Abstract Repetitive control is used in programmable mechanisrns to iteratively improve the tracking of periodic control signals. While a repetitive controller can effectively compensate for periodic disturbances, its ability to learn can cause non-periodic disturbances to degrade performance for many cycles while the controller “forgets” about the disturbance. For example, aone-time jolt to a disk drive can cause a repetitive controller to actually introduce a disturbance by attempting to reject the jolt in later cycles. This paper discusses two methods for reducing the effects of such onetime disturbances. The fast is an “adaptive error saturation” element that is used in conjunction with a new frequency-based repetitive controller design to suppress one-time disturbances with little effect on the learning rate. The second method reduces the disturbance sensitivity of the feedback loop with a “disturbance observer” that can be added to an existing linear feedback controller to directly identify and rejec...