Design of an Infinite-Order Disturbance Observer Enhancing Disturbance Suppression Performance

Abstract

This paper presents the design of an infinite-order disturbance observer (IFDOB) to suppress disturbances including a periodic disturbance. An IFDOB includes the dynamics of a periodic disturbance to suppress it. However, a conventional IFDOB finds it difficult to suppress disturbances in the low-frequency domain. In contrast, a disturbance observer (DOB) can suppress disturbances in the low-frequency domain, however, it has difficulty suppressing a periodic disturbance. Therefore, this paper proposes a designed IFDOB that can suppress both a periodic disturbance and low-frequency disturbances. The proposed method is constructed by designing parameter γ of an IFDOB considering sensitivity and complementary sensitivity functions. Simulations were conducted, and the validity of the proposed method in a practical system was confirmed by experiments using a multi-axis manipulator.

Cascade multi-resonant disturbance observer design. Application to a distillation column

“…We have tested the system under low frequency disturbances, being a unitary ramp (shown in the top plots) and a unitary sinusoidal signal of frequency ω 1 = 1.2566 rad/s (shown in the lower plots). First, we show in the left the response of the system when a pure feed-forward strategy is applied (pure FF, see (39)). We show the ability of the proposal to mitigate sinusoidal signals, and the ability to attenuate the effect of ramplike disturbances.…”

“…4. Implement a control scheme including the observer either as a pure feed forward control (see (39)), or together with a standard feedback controller (see (41)). In this last case, the effect on the closed-loop robustness must be considered as quantified in (46) for the design of both the controller and the observer.…”

“…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 [29], like an infinite order DOB [39], a periodic DOB suitable for aperiodic disturbances [40], or an adaptive notch filter based in the implementation of a time delay [19]. On [21], a phase-lead compensator is used to ensure phased estimation.…”

Control of a Hovering Quadrotor UAV Subject to Periodic Disturbances

“…Infinite order disturbance observer (IFDOB) has been proposed for high frequency periodic disturbance rejection in [17], but it is difficult to suppress the low frequency disturbances with this structure. In response to IFDOB, Enhanced Infinite order disturbance observer (EIFDOB) has been presented recently to remove the disturbances in low as well as in the high frequency region [18].…”

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.…”