A Novel Low-Speed Direct-Drive PMSM Control Strategy based on a Two-DOF Structure

Low-speed control of direct-drive permanent magnet synchronous motor (DD-PMSM) is a troublesome problem, partly since the motor is more sensitive to disturbance under low/ultra-low speed situations. To attenuate the low-frequency disturbances of the mechanical system and realize smooth low-speed control, this paper presents a control strategy using a two-degree-of-freedom (2-DOF) structure. The proposed method directly shapes the two closed-loop transfer functions of reference tracking and disturbance rejection with a 2-DOF scheme, which improves the disturbance attenuation while guarantees satisfactory tracking performance simultaneously. In addition, the system stability and robustness are also analyzed. The effectiveness of the proposed method and the advantages compared to other common-used control strategies are verified through simulations and experimental tests.