Flywheel Micro-vibration Mechanism And Suppression Integrated Study For High Resolution Optical Satellite

In recent years,earth observation technology has been developed rapidly.The targets of the spacecraft system have been greatly improved.The resolution of camera-images that taken by space-optical-satellite increasing from tens of meters to sub-meter level.Meanwhile,the payload is becoming more sensitive to the micro-vibration lead-in by the active part of the satellite on orbit.Flywheel as a commonly used attitude control actuator for modern high stability and high-precision spacecraft,due to rotor dynamic and static imbalance,bearing defects and other factors,the flywheel will generate complex harmonic disturbances when it spinning under the normal working.This makes the micro-vibration of the flywheel become one of the critical technologies for the development of high-resolution-optical-satellite.In this thesis,the disturbance mechanism of the flywheel,the influence of the flywheel disturbance on the high resolution optical satellite and the suppression of the micro vibration of the flywheel are deeply and systematically studied from the flywheel micro vibration source to the optical payload based on theoretical analysis,numerical simulation and ground test.Flywheel disturbance is divided into main-disturbances and structural disturbances according to the structural characteristics of flywheels.The main-disturbances of flywheels are analyzed from four aspects,including rotor imbalance,bearing disturbance,rotor rubbing and installation loosening,and disturbance models are established respectively.The structural disturbance characteristics of the flywheel are discussed from two aspects of the bearing and its supporting part and the dynamic characteristics of the rotor sternum of flywheel.A model of flywheel rotor,bearing and installation foundation is established by sub structure analysis method.The response characteristics of the structural modal changing caused by small boundary conditions to the elastic system of the flywheel component are studied.The influence of flywheel disturbance on modern TDICCD camera and satellite platform is expounded,which mainly includes two aspects: directly causing image shift and directly causing the jitter of satellite platform.The influence of platform micro vibration on image motion of optical load is discussed from three aspects: the principle of TDICCD camera,the classification of image motion and the mechanism of image motion change caused by micro vibration.According to the Newtonian/Eulerian equation,the coupling model of flywheel imbalance and satellite platform is established.The flywheel imbalance parameter is introduced into the coupling model.The parameters of the system are defined,and the translational equation,rotation equation and rotor moment equation are derived.Numerical simulation is carried out for the model,and the results are discussed in depth.Based on the Kistler Table,a micro disturbance force / torque measurement system is designed,which mainly includes air pressure control,air spring isolation system,marble platform,control and data acquisition cabinet.The test system is used to test the disturbance of the flywheel on ground,and the spectrum characteristics of the measured disturbance data are analyzed.The dynamic response model of the whole satellite is set up,and the frequency response of the whole star is analyzed by unit sinusoidal excitation.The measured disturbance data of the flywheel and the whole unit frequency response results are integrated and analyzed via MATLAB and the influence of flywheel disturbance on the payload of optical satellites is analyzed.Based on the mechanism of vibration and noise reduction of viscoelastic material,a viscoelastic damping material sandwich plate flywheel supporting structure is designed,and the parameters of viscoelastic damping layer are optimized.An integrated flywheel disturbance isolator is designed by using the excellent properties of metal rubber,and the arrangement of the neutron isolation unit for the integrated isolator is discussed.The common aluminum alloy flywheel support,sandwich plate support structure and the integrated flywheel vibration isolator is tested respectively.Results show that the flywheel support and the integrated flywheel disturbance isolator have excellent micro vibration suppression performance.A test method for the micro vibration of the satellite based on target imaging on ground is proposed.The quasi-zero stiffness is designed for the ground test suspension system.A system level micro vibration imaging test is carried out in the ultra-clean laboratory with the system.After that,the amount of image shift caused by micro vibration is acquired after processing the imaging data,which provides a reference for further study.