Flexible Spacecraft And Stability Control Algorithm Research

Modern satellite usually comprises central rigid body and light flexible appendages. Due to the existence of rigid-flex coupling, satellite's attitude motion will excite flexible appendages' vibration and flexible appendages' vibration will affect satellite's attitude in turn. To improve the performance of attitude control system, it is urgent to solve the vibration problem of flexible appendages. Moreover, flexible satellite attitude control system is a multi-input multi-output, strongly coupled and nonlinear system with uncertainties. In order to complete the mission of satellite in orbit, the attitude control system must have good performance, which requires that the attitude control algorithm can overcome the impact of model parametric uncertainties and external disturbances. Attitude maneuver and stabilization control of flexible satellite is studied in this dissertation, and the main contents are as follows.To suppress the flexible appendages' vibration during attitude maneuver, input shaping technology is adopted for the flexible satellite attitude control system. For the uncertainties of the flexible appendages' vibration frequencies, the performance of input shapers is discussed. Simulation results show that the proposed EI(Extra-Insensitive) input shaper is strongly robust without increasing the pulse time.To solve the problem of large angle attitude maneuver subject to inertia parametric uncertainties and external disturbances, an active disturbance rejection attitude controller for flexible satellite is proposed. An extended state observer is designed to estimate the effect of inertia parametric uncertainties, external disturbances and flexible appendages' vibration, and then it is compensated on time. A nonlinear state error feedback law is designed to eliminate the tracking error. To suppress the flexible appendages' vibration during large angle maneuver, a method of arranging the transient dynamics based on El input shaper is presented, which can reduce the flexible appendages' vibration and suppress the residual vibration. Simulation results show the proposed controller can overcome parameter perturbation as well as external persistent disturbances, and has strong robustness. Further, an active disturbance rejection attitude control scheme for the flexible satellite is proposed without the angular velocity signal feedback. Simulation results show the proposed controller can realize satellite attitude control with high performance when subject to parametric uncertainties and external persistent disturbances.For highly nonlinear characteristics of the satellite attitude control system, considering inertia parameter perturbation and bounded disturbances, a backstepping controller which is adaptive to inertia parameter is proposed. Further, given the unknown supremum of disturbances, a backstepping control scheme based on RBF neural network is designed. It can compensate the model uncertainties and achieve high-performance control. Numerical simulation results demonstrate the feasibility and effectiveness of the proposed two controllers.