On Modeling And Disturbance Rejection For Gimbal Servo System Of Single Gimbal Control Moment Gyroscope

The single gimbal control moment gyroscope(SGCMG)is widely used in spacecraft attitude control system for it has simple mechanical structure,large output torque,fast response speed and long service life.SGCMG is mainly composed of a gimbal servo system,a highspeed rotor and a supporting platform.The output torque of SGCMG is determined by the output speed of the gimbal servo system.However,in the actual operation,the SGCMG gimbal servo system suffers from multi-source disturbance and unmodeled dynamics.It is difficult to achieve the desired speed control effect.Therefore,it has meaningful and good application prospects to adopt advanced control strategies and reasonable controllers to compensate or suppress the effects of multi-source disturbances and unmodeled dynamics on SGCMG gimbal servo system.In this paper,the research object is direct drive SGCMG gimbal servo system based on permanent magnet synchronous motor(PMSM).The main results and contributions are as follows:(1)Aiming at the problem of flexible mounting dynamic in SGCMG gimbal servo system,a dynamic compensator and a loop compensator are designed respectively.The simulation and experimental results show that the two controllers have a certain compensation effect on the speed attenuation oscillation caused by flexible mounting dynamic.The dynamic compensator has stronger robustness and the loop compensator has higher compensation accuracy.(2)Aiming at the problem of external harmonic disturbance in SGCMG gimbal servo system,a feedforward compensation control strategy based on disturbance observation is adopted.The harmonic disturbance observer(HDOB)and the harmonic disturbance observer based on notch filter(NFHDOB)are designed respectively.Simulation and experimental results show that HDOB has higher disturbance estimation accuracy and stronger robustness than NFHDOB and general DOB.Moreover,the feedforward compensation method based on HDOB has better compensation effect and stronger robustness.(3)In view of the existence of both flexible support dynamics and external disturbance in SGCMG gimbal servo system,two composite control methods are proposed respectively.One is based on loop compensator and disturbance observer.The other is based on continuous sliding mode controller and disturbance observer.The controller based on loop compensator can compensate the influence of multi-source disturbance when the system parameters are accurate.The composite controller based on sliding mode control has better anti-disturbance and robustness.