Research on High-Performance Speed Regulation of Switched Reluctance Motor Based on Improved Nonsingular Fast Terminal Sliding Mode Control and an Adaptive Bandwidth Modified Super-Twisting Observer

In response to the severe chattering, slow dynamic response, and limited disturbance rejection capability of switched reluctance motor (SRM) drive systems under conventional control methods, this paper develops an improved nonsingular fast terminal sliding mode controller (INFTSMC). An integral sliding surface is first designed to eliminate the steady-state tracking error. An adaptive exponent and an improved double-power reaching law are then introduced to enhance the convergence performance. In addition, a smooth hyperbolic tangent approximation and a boundary layer design are employed instead of the conventional signum function to suppress chattering while maintaining a rapid response. Theoretical analysis demonstrates that the sliding variable is globally asymptotically stable and enters any prescribed neighborhood of the origin within a fixed time independent of the initial condition, thereby establishing practical fixed-time convergence rather than exact finite-time stability. Furthermore, an error-dependent bandwidth scheduling mechanism is incorporated into the modified super-twisting observer, resulting in an adaptive bandwidth modified super-twisting observer (AB-MSTO) for load torque estimation and compensation. The proposed bandwidth scheduling mechanism improves the balance between transient estimation speed and steady-state noise sensitivity. Finally, a MATLAB/Simulink simulation platform is constructed to evaluate the proposed control strategy. The simulation results demonstrate that the proposed INFTSMC combined with the AB-MSTO improves the dynamic speed regulation performance and disturbance rejection capability of the SRM drive system under different operating conditions.