Improved Supertwisting Nonsingular Fast Terminal Sliding Mode Observer-Based Deadbeat Fault-Tolerant Predictive Control for IPMSM Demagnetization Fault

In this article, a deadbeat fault-tolerant predictive control (DFTPC) strategy based on the improved supertwisting nonsingular fast terminal sliding mode observer (IST-NFTSMO) is proposed. First, the IST-NFTSMO is designed by combining the improved supertwisting algorithm with the nonsingular fast terminal sliding mode (NFTSM) to observe the flux linkage and the current prediction value quickly and accurately. Based on the observed values, the DFTPC algorithm is designed to effectively compensate torque loss caused by demagnetization of permanent magnet, thus achieving fault-tolerant control. The improved supertwisting control law accelerates the convergence speed of the system and suppresses the system chattering. Second, a NFTSM controller based on improved extended supertwisting sliding mode disturbance observer (IEST-SMDO) is designed. The controller is combined with the DFPTC to further enhances the robustness and response speed of the system. Disturbances caused by demagnetization, load changes, and the action of the DFTPC algorithm in the system can be observed faster by IEST-SMDO. The observed disturbances are feedforward compensated to the speed loop controller and the immunity of the system is boosted. Finally, the experimental results show the proposed method has stronger fault tolerance and robustness than the conventional method when the IPMSM suffers from demagnetization fault.