Study On Modeling And Attitude Control Of Flexible Spacecraft Considering The Effects Of Gravity

With the increasing development of aerospace science and technology, high-precision control of the spacecraft is needed to complete a variety of sophisticated space missions. However modern spacecraft is usually equipped with flexible attachments, there is coupling between its central rigid body and flexible attachments in the process of the fast attitude maneuver of the flexible spacecraft, which leads to vibration of flexible appendages, then the attitude control accuracy will be affected and the whole system performance will be reduced. Therefore, attitude control and vibration suppression of flexible spacecraft have attracted wide attention, and many scholars at home and abroad have studied this subject. Previous controller design methods are complex and have big overshoot, and gravity can’t be eliminated completely in ground microgravity simulation experiments, meanwhile the flexible solar panel vibration characteristics can be affected by gravity potential and its direction.So in this paper, the influence of gravity on the flexible spacecraft control is fully considered, to establish the dynamical model of the flexible spacecraft, and the relative simple algorithms are proposed to control the attitude and suppress the vibration of flexible spacecraft. The specific contents are as follows:Firstly, considering that the gravity item of the flexible spacecraft will change from ground testing phase under gravity environment to space application phase under microgravity environment, a uniaxial rotating flexible spacecraft is chosen as the control object, and based on the basic mechanics theorem, the Newton-Euler method is adopted to establish the dynamical model of the flexible spacecraft which considers the gravity influence, the vibration characteristics and the attitude control accuracy are simulated on ground testing phase and in space application phase, respectively.Secondly, considering attitude control and vibration suppress of flexible spacecraft in different gravity environments, an active disturbance rejection controller is designed, by taking full advantage of its independence on the object’s precise mathematical model, the extended state observer is designed to estimate the disturbances. Meanwhile the positive position feedback is designed to realize the fast attenuation of vibration. The simulation results show that the controller is effective.Last, due to there are too many parameters in active disturbance rejection controller, an adaptive backstepping sliding mode control method is proposed to solve the problem. The controller is designed based on the backstepping theory to control the flexible spacecraft under the influence of model and disturbances uncertainties, and the adaptive control law is proposed to estimate the upper bound of the uncertainties in real time. Finally, the attitude control and vibration suppression of flexible spacecraft in different gravity environments is realized.