An Enhanced Periodic-Disturbance Observer for Improving Aperiodic-Disturbance Suppression Performance

Abstract

Repetitive operations are widely conducted by automatic machines in the industry, and the periodic disturbances induced by such operations are a concern as they hinder the proper functioning of these machines. A periodic-disturbance observer (PDOB) has been studied previously to compensate for the periodic disturbances. This observer is a twodegree-of-freedom controller based on the observer structure estimating a periodic disturbance. However, the PDOB does not take aperiodic disturbances into account because it focuses only on periodic disturbances. This paper proposes an enhanced PDOB to enable the PDOB also to compensate for aperiodic disturbances. The enhanced PDOB is constructed by combining the PDOB and disturbance observer. Experiments were conducted using a multi-axis manipulator to compare the PDOB with the enhanced PDOB. The experimental results demonstrate the validity of the proposed method.

A design of disturbance observer in frequency domain for robust control of time delay system

“…There are some applications that have applied DOB to the time delay system 22–24 . In Reference 22 and later relevant studies, communication disturbance observer (CDOB) were introduced to compensate the time delay on the network and this method has been used in bilateral teleoperation system.…”

“…In many applications, first order low‐pass filter has been commonly used as a Q‐filter for simplicity in design 22,23,29 . But later studies began to focus on high order DOB for the better disturbance suppression performance.…”

“…[16][17][18][19][20][21] There are some applications that have applied DOB to the time delay system. [22][23][24] In Reference 22 and later relevant studies, communication disturbance observer (CDOB) were introduced to compensate the time delay on the network and this method has been used in bilateral teleoperation system. Although CDOB is regarded as another powerful time delay compensation method besides smith predictor, it does not aim at the suppression of the external disturbance but the compensation of time delay itself.…”

“…In many applications, first order low-pass filter has been commonly used as a Q-filter for simplicity in design. 22,23,29 But later studies began to focus on high order DOB for the better disturbance suppression performance. This resulted in development of the H ∞ norm minimization based DOB design methods because all the performances and stability of the system is evaluated by H ∞ norm.…”

Design of disturbance observers based on their implementability in industrial control systems

“…Several solutions have been presented for DOB under periodic disturbances. Some authors use the combination of a DOB for estimating low frequency components of the disturbances and other solutions for periodic components, like an infinite order DOB [94], a periodic DOB suitable for aperiodic disturbances [96], or an adaptive notch filter based in the implementation of a time delay [95]. On [69], a phase-lead compensator is used to ensure phased estimation.…”