On the usefulness of higher-order disturbance observers in real control scenarios based on perturbation estimation and mitigation

In this paper, a technique of increasing the effectiveness of estimating the overall system uncertainty with a class of high-gain disturbance observers is discussed. In theory, by introducing a particular set of additional, fictitious states to the system model, the considered observers can more effectively estimate wider variety of disturbances than in their classical forms. This work describes the verification of such theoretical statement also in practice. Both advantages and disadvantages of the proposed framework are pointed out in the paper using an Extended State Observer (ESO), that serves as an working example. An evaluation of the considered technique is carried out through a combination of numerical simulations and laboratory experiments.