Precise Position Control Based on Resonant Controller and Second-Order Sliding Mode Observer for PMSM-Driven Feed Servo System

Precise position control and smooth feed speed are important research areas for permanent magnet synchronous motor (PMSM) driven computerized numerical control (CNC) servo feed systems, but it suffers from aperiodic disturbances caused by unmodeled dynamics, system parameter perturbations, variable cutting force and periodic disturbances caused by the current sampling error, aperiodic disturbances, and periodic disturbances that reduce the positional accuracy of the CNC feed servo. To address the problem, a control scheme is proposed for the position controller to suppress the disturbances. In the control scheme, the second-order sliding mode disturbance observer (SSMDO) is proposed to estimate and compensate for the aperiodic disturbances, and the resonant controller (RC) with phase adjustable is designed to suppress the periodic disturbances. The stability and antidisturbance capability of the studied scheme are analyzed systematically, and the flow of controller design and parameter tuning is presented considering the overall system. The proposed RC combined with SSMDO (RC-SSMDO) scheme can effectively alleviate the position tracking error and feed steady-state speed ripple, which is suitable for the actual working conditions of the CNC feed servo system. Experiment results confirm the validity of the proposed scheme.