Adaptive robust control of AC motors with fractional-order disturbance observer

Parametric uncertainties and uncertain nonlinearities always exist in mechatronics servo system and degrade their tracking accuracy. In this paper, adaptive robust control with fraction-order disturbance observer is synthesized for high accuracy motion control of a AC motor. The global stability was proved via Lyapunov Theorem. The proposed controller accounts for not only the parameter deviation (e.g., unknown inertia load), but also the uncertain nonlinearities (coming from modeling errors and external disturbances). In the resulting controller, parameter adaptation was used to reduce the parameter uncertainties, the fractional-order disturbance observer was used to estimate the modeling errors and external disturbances. To attenuate the uncompensated disturbances and errors, the robust controller was designed. The comparative simulation results show that the proposed controller guarantees a prescribed tracking performance.