Variable Structure Maneuvering Control With Time-Varying Sliding Surface And Active Vibration Damping Of Flexible Satellite

With the rapid development of satellite technology and the ever-increasing demand of space programs, the active vibration control of satellite flexible structures has become a crucial technique in the design of satellite attitude control system. In this thesis, the attitude control problem and the active vibration suppression control of flexible satellite with piezoelectric intelligent sensors/actuators are thoroughly investigated, which are based on the National Natural Science Foundation of China—Study on active vibration control of flexible spacecraft (60674101) and the Research fund for the Doctoral Program of Higher Education of China—Active vibration control of spacecraft with large flexible multi-bodies structure (20050213010). The main contents are listed as follows.To begin with, the nonlinear kinematical equation and dynamic equation expressed with low-order modals are given, which will lay a solid foundation for the analysis and design of the satellite attitude control system.Due to the model uncertainties and the external disturbances exerted on the satellite model, a variable structure control method is applied based on the nonlinear low-order dynamic model. Lyapunov technique is then utilized to analyze the existence and stability of the sliding mode selected. At the same time, to suppress the vibration of flexible structure, a Strain Rate Feedback (SRF) compensator is designed to increase the damping of flexible structure, and therefore the vibration can be rapidly attenuated. In addition, the pulse-width-pulse-frequency (PWPF) modulation method is applied to the thruster control, which enables the thrusters produce the required series of control pulses. And last, simulation analysis is performed for the proposed methods, and the results demonstrate that the combination of variable structure controller and the active vibration control compensator can suppress the vibration of flexible modals effectively, and at the same time, increase satellite pointing accuracy.What's more, a time-varying sliding mode variable structure controller using only available output information is investigated based on the nonlinear low-order dynamic model. Then, another variable structure controller is presented by combining linear sliding mode and nonlinear sliding mode. The switch mechanism between the linear and nonlinear sliding mode is also discussed to implement the rapid attitude maneuver of flexible satellite. Finally, the proposed method is also applied to the attitude maneuver control of three-axis stabilized flexible satellite. Simulation results show the effective attenuation of the vibration of flexible appendages, and the simplicity, reliability, and robustness of the proposed approach.