Improved sliding mode disturbance observer-based model-free finite-time terminal sliding mode control for IPMSM speed ripple minimization

The model-free sliding mode control with sliding mode disturbance observer (SMDO) for interior permanent magnet synchronous motor (IPMSM) is affected by feedback delays caused by mismatch of motor parameters. The observer is lagged behind the change of external disturbances, the speed tracking accuracy and transient control performance for IPMSM drives are reduced. In order to solve the issues, an improved higher-order sliding mode disturbance observer-based model-free finite-time terminal sliding mode control (HOSMDO-MFFTTSMC) strategy is proposed in this paper. First, a finite-time terminal sliding mode surface (FTTSMS) is designed, and a rotation speed-loop-based MFFTTSMC strategy is designed by combining the ultra-local model. The system control state is converged in finite time and the accurate tracking of observation error is realized. In addition, the non-singular fast terminal sliding mode is introduced into the observer, the higher-order SMDO is designed. The unknown part of disturbances is observed and compensated in real time, the fast-tracking response capability and anti-disturbance capability for IPMSM are improved, and the stator current harmonics are effectively suppressed. Finally, the proposed HOSMDO-MFFTTSMC strategy is experimentally demonstrated with a 6.6kW motor. The correctness and effectiveness of the HOSMDO-MFFTTSMC strategy are verified by simulation and experimental results.