Research On Micro-vibration Isolation Methods For Single Gimbal Control Moment Gyro Of Spacecraft

With the rapid development of high accuracy spacecraft, requirements to mechanical environment in space become more and more rigorous. However, micro-vibrations generated from single gimbal control moment gyro(SGCMG), the typical actuator of attitude control system, would degrade the pointing accuracy and stability of spacecraft. In order to mitigate this disturbance to space missions, micro-vibrations isolation technology is studied in this dissertation. A newly designed passive isolator is proposed, analysed and then verified by experiment. The main research work are summarized as follows:A low-stiffness passive vibration isolation method is specifically put forward based on the analysis of micro-vibration characteristics of SGCMG. A new passive isolator with elastic-viscoelastic composited configuration is designed, which consist of elastic supporting units and viscoelastic damping units.Dynamic properties of viscoelastic material in frequency domain is mearsured in isothermal condition. Standard rheological model and fractional derivative model are adopted to describe the frequency-dependent characters of viscoelastic material, then their parameters are identified with experiment data. Fitting results shows that fractional derivative model has higher fitting precision than standard rheological model and the most accurate one is the fractional derivative model with five parameters.Parametric finite element model of the porposed SGCMG isolation system is developed. Dynamic characteristics and vibration isolation performance of isolation system are analyzed. Simulation results indicate that disturbances with frequency above 50 Hz can be isolated in all six degrees of freedom; response value in resonance region are greatly suppressed due to the damping effect provided by viscoelastic material.Structural sensitivity analysis of SGCMG vibration isolator is conducted to evaluate influence of structure parameters on natural frequencies. Subsequently, structural optimization of vibration isolator is accomplished. Comparisons show that frequency range of isolation is expanded by 13.46 Hz at least after optimization. Besides, in the working condition of SGCMG, transmissibility values in six degrees of freedom are all smaller than-25 dB, with improvement of 16.88% or even better.Measuring system for micro-vibration is established. The performance of vibration isolator with working rotating speed is acquired through on-groud experiment. Recording data prove that the micro-vibration disturbance from SGCMG can be effectively isolated by the proposed vibration iaolator in all degrees of freedom. The correctness of method and device for micro-vibration isolation are verified.