Continuous fixed-time super-twisting sliding mode disturbance observer based on fixed-time backstepping control for induction motor drives

To address the performance degradation of classical indirect field-oriented control of the induction motor caused by external disturbances, such as load torque variations and parameter uncertainties, this article proposes a continuous fixed-time backstepping control strategy based on a fixed-time disturbance observer using the super-twisting algorithm (FxTBC + FxTDO). The objective is to enhance the dynamic response and robustness of the induction motor drive system. First, a mathematical model of the induction motor incorporating total disturbance terms, including both external disturbances and parameter uncertainties, is established in the state-space framework. Next, a fixed-time disturbance observer (FxTDO) is designed to estimate these lumped disturbances. The estimated terms are then incorporated into the control law to compensate for their effects. Subsequently, a fixed-time backstepping controller (FxTBC) is developed. The fixed-time stability of the closed-loop system is rigorously established using Lyapunov theory. Finally, the effectiveness of the proposed approach is validated through MATLAB/Simulink simulations and compared with a super-twisting finite-time control scheme (FTC + FTDO). The results demonstrate that the proposed FxTBC–FxTDO strategy achieves a 20% reduction in settling time compared to the FTC–FTDO method, while providing superior disturbance rejection performance. Moreover, the chattering phenomenon is reduced by approximately 24% using the proposed approach.