Adaptive backstepping position control with state constraint based on predefined time nonlinear disturbance observer for PMSM servo control systems

To address the slow dynamic response, cumbersome control structure, and difficult parameter tuning issues caused by nested loop structures in traditional cascaded permanent magnet synchronous motor servo control systems (PMSMSCS), this paper designs a position tracking composite controller based on adaptive backstepping control (ABC). In the integration of position and speed loops, a barrier Lyapunov function (BLF) is incorporated into the ABC framework to constrain system states, which ensures rotor operation within a reasonable range and realizes the prescribed performance of the servo system. Meanwhile, in the integration of position, speed and current loops, the composite controller adopts a leakage adaptive law with strong robustness, combined with prescribed performance indicators, effectively suppressing system parameter drift. Furthermore, a robust predefined time nonlinear disturbance observer (PTNDO) is developed to estimate the mismatched unknown external disturbances existing in PMSMSCS. On the basis of the global uniform ultimate boundedness theory and predefined time convergence theory, the comprehensive stability of the proposed composite controller is systematically analyzed. Finally, the experiment verified that the proposed composite controller enables PMSMSCS to possess excellent steady-state performance, anti-disturbance ability, and parameter uncertainty robustness.