Output feedback-based sliding mode control for disturbed motion control systems via a higher-order ESO approach

Abstract

This study presents an output feedback-based sliding mode control approach for motion control systems withmismatched/matched disturbances. The key idea of this study is to reconstruct the unmeasured auxiliary states anddisturbances synchronously online by constructing a higher-order extended state observer (HOESO). It is shown that theresulting sliding mode controller based on HOESO can drive the system output to an ultimately bounded region, which can beregulated arbitrarily small by assigning a sufficiently large scaling gain. Different from the existing extended state observermethods, the newly proposed HOESO treats the known dynamics satisfying the Lipschitz condition and the unknown higherorder disturbances separately. As such, it provides a feasible way for higher-precision states/disturbance estimation. Thanks tothe utilisation of HOESO, the upper bound of disturbances is not necessarily required as a priori and the switching gain isadaptively chosen based on the estimation error such that the chattering effects can be significantly reduced. Experiments forspeed regulation of a brushless DC motor are conducted to verify the effectiveness of the proposed method.