Torque Ripple Minimization of Low-Speed Gimbal Servo System Using Parameter-Optimized ESO

Torque ripple of permanent magnet synchronous motor (PMSM) and load disturbances are the main influencing factors that restrict the application of PMSM in low-speed tracking systems. To improve the speed tracking precision of the gimbal servo system in control moment gyro (CMG) with multisource disturbances, this article proposes a composite control method based on parameter-optimized extended state observers (ESOs) with sliding mode control in the speed loop and PI control with a feed-forward compensation in the current loop. Three ESOs are employed to estimate the disturbances on the
$d$
-axis current, the
$q$
-axis current, and the load torque so that the controller can have the corresponding parts to compensate for the disturbances. In particular, aiming at the contradiction between the estimation quality of the observer and the sensitivity to the measurement noise, an appropriate cost function is designed to take a compromise between the lumped disturbances and measurement noise and optimize the parameters of the ESOs. Finally, simulation and experimental results on the gimbal servo system of magnetically suspended control moment gyroscope (MSCMG) show the effectiveness of the proposed methods.