Research On The Microvibration Isolation Method And Technology For Flywheel Of Satellite

Flywheel is a common actuator of attitude control system for earth observationsatellites and space telescopes. When the flywheel operates, it generates lots ofhigh-frequency, low-amplitude force and torque disturbances, induces microvibration ofthe satellite, influences pointing accuracy and stability of the payload, which lead to thedegradation of the imaging quality. In order to mitigate disturbances of the flywheel onthe satellite, a flywheel vibration isolation system is proposed, analyzed andexperimentally verified in this thesis through research efforts on the microvibrationisolation approach and technology of the flywheel. The main research work is asfollows:A flywheel vibration isolation platform with the configuration of multi-foldedbeams is proposed. The equivalent stiffness of the platform is acquired; a six degree offreedom analytical dynamic model of the flywheel vibration isolation system isestablished; the natural frequencies of the system are analyzed. The analysis resultsshow that the spinning speed, the altitude of the mass center, the inertial property andthe internal flexibility of the flywheel will influence the natural frequencycharacteristics of the vibration isolation system.The finite element model of the proposed flywheel vib ration isolation system isbuilt up; modal analysis, frequency response analysis and vibration isolationperformance analysis of the system are conducted. The analysis results show that themost significant error of the natural frequencies respectively calculated by the analyticaldynamic model and the finite element model of the system is only3.92%, whichvalidates the analytical dynamic model. The vibration isolation system can effectivelyisolate disturbance outputs when the flywheel spins at high speed and the systemexhibits broader vibration isolation range and more excellent high-frequencyperformance after the optimization, with the vibration isolation rate of the forcedisturbance increased by10.51dB when the flywheel spins at the speed of6000rpm.An active control method of the flywheel vibration isolation system is proposedbased on piezoelectric material. The finite element model and state space equations ofthe vibration isolation system with piezoelectric beams are established. Disturbanceoutputs of the system and vibration responses of the flywheel before and after activecontrol are simulated and analyzed. Results show that the introduction of active controlincreases damping of the system, decreases vibration of the flywheel and disturbanceoutputs of the system at two critical speeds; the effectiveness of active control isinfluenced by the position and number of piezoelectric sensors and actuators. Theperformance of the active vibration control improves with more piezoelectric beams.Experiments on the effectiveness of the vibration isolation system are carried out. According to the design method proposed in this thesis, a flywheel vibration isolationplatform is manufactured and tested by the Kistler Table microvibration experimentsystem. The experiment results show that the critical speed of the flywheel is in linewith the theoretical analysis; the designed vibration isolation system can effectivelyisolate high-frequency disturbances produced by the flywheel, which verify the validityof the theoretical model and the vibration isolation method established in this thesis.