Delta-Operator-Based Extended Disturbance Observer and Its Applications

In this paper, a delta-operator-based discrete-time disturbance observer (DO) is proposed for a class of uncertain systems. The proposed observer not only estimates disturbances but also their derivatives, enabling improvement in the accuracy of the estimation of disturbances. The scheme seamlessly unifies the design of continuous-time and discrete-time DOs. The proposed observer is combined with a discrete-time sliding-mode controller with application to mismatched systems. The stability of the overall system is proved. The efficacy of the scheme is illustrated by the simulation of numerical examples and by implementation on a 2-degree-of-freedom serial flexible joint manipulator setup in a laboratory.