Studies On Dynamic Characters And Vibration Control Of Weak Coupling Satellite Antenna Structure

Recent years, due to the high development of communications, space science, ground observation and reconnaissance technology, large space antennas with high capability on satellites is used more and more widely. Since the development of antennae on five generation satellites have been researched by America, the caliber of antenna goes from 9m to 150m. Due to the impulse on antenna induced by sun wind, astro-fragments and engine, it is indispensable to research dynamic characters and vibration control in order to improve the precision and lifetime of antenna structure.Satellite structure is typical weak coupling cyclic periodic structure. The dynamic characters of the structure are very complicated, and vibration control of the structure becomes a quite difficult problem along with the caliber increasing. The vibration control of disordered weak coupling antenna is one of the most difficult problems. Many research results show that the dynamic characters of weak coupling periodic structures are affected obviously by small disorder and remarkable vibration mode localization can be produced. Vibration mode localization has been proved exiting in a 5.75m antenna by a vibration experiment conducted by America researchers, and probability of the localization appearing and awful affects have been confirmed becoming more seriously with bigger antenna.The disadvantageous influences on weak coupling satellite antenna by vibration mode localization are mainly presented as follows:1) Precision and lifetime of satellite antennas can be influenced greatly by this mode localization.2) The vibration control system may be invalid by structural disorder.3) The measurements of sensors may be wrong with disorder exiting.4) The response of some substructure may be striking and the whole system will be damaged ultimately.So the effects of disorder must be considered when carrying on the dynamic analysis of such structures. It is significant to research the effects of disorder for guaranteeing the normal working of antenna, developing space communications and observation and so on.In the paper, with considering the effects of small disorder adequately, the dynamic characteristics, vibration control problem of weak coupling satellite antenna structure are studied as follows:The dynamical model of weak coupling satellite antenna is established by applying theoretical method and finite element method, respectively. The dynamic characters of weak coupling periodic structures are analyzed. Results show that small disorder can induce remarkable vibration modes localization. The Lyapunov exponents are researched in detail for the purpose of finding the mechanism of vibration mode localization phenomenon and the reason of the spread differences between perfect structure and disordered structure vibrates.Based on the theoretical model of weak coupling satellite antenna, effects on dynamic characters due to the disorder of parameters are investigated through lots of calculations. Local factors of disordered and perfect structure are computed under diversified situations of disorder, and the influence law and change trend of dynamic characters of antenna structures in satellites produced by stiffness and mass of antenna ribs, stiffness of antenna membranes and angles between adjacent ribs, are obtained ultimately.Considering the effects of disorder, the vibration control is investigated based on the finite element model of piezoelectric smart weak coupling periodic satellite antenna. The effects on vibration control of cyclic periodic structure by disorder are learned. The results show week coupling structure is influenced by disorder obviously, whereas strong coupling structure is affected slightly. The vibration control system is designed applying diversiform control method, respectively. The advantages and disadvantages of those methods are presented, respectively.With the intention of investigating the position optimization of sensors and actuators for satellite antenna structure, an improved particle swarm optimization (PSO) method is presented. The general energy of antenna system is regarded as the optimal target in the method. A numerical example is simulated by diversiform optimization method to optimize the positions of sensors and actuators, respectively. The results show the improved PSO method has merits of quick convergence and perfect accuracy, and the efficiency of controller is improved distinctly via position optimizing.