Uncertainty and disturbance estimator-based controllers design under finite control bandwidth constraint

In this paper, tracking versus disturbance rejection tradeoff is revealed and quantitatively investigated for systems utilizing uncertainty and disturbance estimator (UDE)-based controllers. The tradeoff appears to be due to finite control bandwidth, characterizing any real-world application. Based on the exposed findings, guidelines for designing UDE controllers are provided, and respective operational limits are indicated. It is shown that two operation points exist on performance envelope, characterized by similar disturbance rejection, while yielding different tracking performance. Moreover, it is demonstrated that typical proportional-integrative controllers, designed using zero-pole cancellation, are a particular case of UDE controllers. As an example, the proposed method is applied to average current control of a bidirectional noninverting multimode buck-boost converter. Simulations and experimental results are provided to validate the research outcomes.