Adaptive Rejection of Periodic Disturbances Acting on Linear Systems with Unknown Dynamics

TL;DR

This paper introduces a direct adaptive control method that effectively rejects unknown periodic disturbances and tracks trajectories in uncertain linear systems without requiring a plant model, demonstrated on a hard disk drive system.

Contribution

A novel direct adaptive control algorithm for unknown periodic disturbances that does not need plant models or batch measurements, applicable to various plant types.

Findings

Successfully rejected periodic disturbances in experiments.

Achieved accurate trajectory tracking in a hard disk drive system.

Applicable to both minimum and non-minimum phase plants.

Abstract

This paper proposes a novel direct adaptive control method for rejecting unknown deterministic disturbances and tracking unknown trajectories in systems with uncertain dynamics when the disturbances or trajectories are the summation of multiple sinusoids with known frequencies, such as periodic profiles or disturbances. The proposed algorithm does not require a model of the plant dynamics and does not use batches of measurements in the adaptation process. Moreover, it is applicable to both minimum and non-minimum phase plants. The algorithm is a "direct" adaptive method, in the sense that the identification of system parameters and the control design are performed simultaneously. In order to verify the effectiveness of the proposed method, an add-on controller is designed and implemented in the servo system of a hard disk drive to track unknown nano-scale periodic trajectories.