Robust State‐and‐Disturbance Observer Design for Linear Non‐minimum‐phase Systems

Abstract

When there are external disturbances acting on the system, the conventional Luenberger observer design for state estimation usually results in a biased state estimate. This paper presents a robust state and disturbance observer design that gives both accurate state and disturbance estimates in the face of large disturbances. The proposed robust observer is structurally different from the conventional one in the sense that a disturbance estimation term is included in the observer equation. With this disturbance estimation term, the robust observer design problem is skillfully transformed into a disturbance rejection control problem. We then can utilize the standard H ∞ control design tools to optimize the robust observer between the disturbance rejection ability and noise immune ability. An important advantage of the proposed robust observer is that it applies to both minimum-phase systems and non-minimum phase systems.

Fractional‐order sliding mode load following control via disturbance observer for modular high‐temperature gas‐cooled reactor system with disturbances

“…Similar to the previous analysis, it can be deduced from inequality (34) that the sliding variable s 𝜌 can converge to zero within a finite time. Moreover, the reactivity error e 𝜌 can globally exponentially converge to zero by means of Lyapunov finite-time stability theory and fractional-order terminal sliding mode control theory [37,38].…”

“…In fact, model uncertainties and external disturbances that bring adverse effects on control system performance are generally unavoidable and unknown in real-life systems. In the last four decades, a number of powerful disturbance/uncertainty estimation techniques have been exploited in industrial systems [34,35], for example, DO, sliding mode observer, Kalman filter, extended state observer, and uncertainty and disturbance estimator.…”

Disturbance Observer Design for Nonlinear Systems Represented by Input–Output Models

“…It should be noted that the conventional frequencydomain DOBs given in [14] require the linear systems being considered to have minimum-phase properties. The DOB design method has been extended recently to non-minimumphase systems [16]. However, it should also be noted that the systems considered in [14], [16] are required to be linear or, alternatively, their nonlinear parts must be lumped together as a part of the disturbance variable.…”