Speed Fluctuation Suppression Method for Gimbal Servo System With Harmonic Drive Based on Coarse-to-Fine Compensation

The harmonic drive (HD) can increase the output torque of the single gimbal magnetically suspended control moment gyroscope (SGMSCMG), but the nonlinear transmission torque introduced by HD can lead to load-side speed fluctuation of the gimbal servo system. In order to suppress the fluctuation in angular speed caused by the nonlinear transmission characteristics of HD, a composite control strategy that integrates coarse-to-fine compensation is proposed. The nonlinear torque of the HD is reconstructed by the adaptive feedforward cancellation (AFC) method, and the torque feedforward compensation table is first established for coarse compensation. Then, the integral sliding mode control based on extended state observer (ESO-ISMC) is designed to further suppress the residual multisource disturbances and improve the control precision of the gimbal speed. The proposed method is verified by simulation and experiment based on SGMSCMG. The results show that the proposed method can effectively suppress speed fluctuation and enhance the robustness of the gimbal servo system.