A Model-Free Predictive Direct Speed Control Method for Surface-Mounted Permanent Magnet Synchronous Motors Based on an Ultra-Local Model

Traditional cascade control structures for surface-mounted permanent magnet synchronous motors (SPMSMs) suffer from strong coupling between the speed and current loops and high sensitivity to parameter variations. To address these issues, this paper proposes a model-free predictive direct speed control (MFPDSC) method based on an ultra-local model. The core innovation lies in constructing a direct speed ultra-local model that mathematically merges the q-axis current dynamics with the motion equation via integration, directly relating the rotor speed to the q-axis voltage. This eliminates the dependence on cascade structures and consolidates the disturbances of both loops into a single lumped perturbation for estimation. Compared with existing model-free predictive direct speed control schemes, the proposed method requires fewer control parameters. The d-axis adopts model-free predictive current control (MFPCC), and disturbances are compensated in real time by a data-driven observer and a reduced-order extended state observer (RESO). The d-axis current control and direct speed control act simultaneously to generate the voltage vector. Finally, experiments on a physical platform demonstrate that the proposed method offers advantages in speed tracking, load disturbance rejection, and robustness against parameter variations, thereby verifying the effectiveness of the proposed control strategy.