Quasi-periodic Disturbance Observer for Wideband Harmonic Suppression

• Main Author: Muramatsu, Hisayoshi
• Format: Journal Article
• Language: English
• Published: 01.06.2024
• Subjects: Computer Science - Systems and Control
• DOI: 10.48550/arxiv.2406.00362

Periodic disturbances composed of harmonics usually appear during periodic operation, impairing performance in mechanical and electrical systems. To improve the performance, control for periodic-disturbance suppression has been studied, such as repetitive control and periodic-disturbance observer. For robustness against perturbations in each cycle, slight changes over cycles, slight variations in the period, and/or aperiodic disturbances, although wideband harmonic suppression is expected, the conventional methods have trade-offs among the wideband harmonic suppression, non-amplification of aperiodic disturbances, and deviation of harmonic suppression frequencies. This article proposes a quasi-periodic disturbance observer to estimate and compensate for a quasi-periodic disturbance. The quasi-periodic disturbance is defined to consist of harmonics and surrounding signals, based on which the quasi-periodic disturbance observer is designed using a periodic-pass filter of a first-order periodic/aperiodic separation filter, time delay integrated with a zero-phase low-pass filter, and an inverse plant model with a first-order low-pass filter. For the implementation of the proposed observer, its Q-filter is discretized by the exact mapping of the s-plane to the z-plane, and the inverse plant model is discretized by the backward Euler method. The experiments validated the frequency response and position-control precision of the quasi-periodic disturbance observer in comparison with conventional methods.