Fixed-time convergent logarithmic sliding-mode control with DOB for PMSM

This paper presents a Fixed-Time Convergent Logarithmic Sliding-Mode Controller (FC-LnSMC) to suppress chattering in permanent magnet synchronous motor (PMSM) speed loop. By embedding a terminal attractor, an Adaptive Sliding-Mode Reaching Law (ASMRL) with self-tuning gains is created; it retains the finite-time convergence of NFTSMC yet yields a smooth control signal. A Disturbance Observer (DOB) further estimates and compensates for unknown load torques, giving the scheme strong robustness. Matlab/Simulink results show that FC-LnSMC outperforms standard SMC by eliminating chatter more effectively and rejecting disturbances more vigorously.