Design Of Attitude Controller Without Angular Velocity Measurement Of Flexible Spacecraft

With the rapid development of space science and technology,more and more spacecraft are equipped with large-scale flexible appendages to meet the increasingly complex mission requirements.During the on-orbit operation of the flexible spacecraft,due to the failure of the angular velocity measurement unit,the disturbance from the external environment and the fault of the actuator,it is necessary to consider the problem of unmeasurable angular velocity information,unmeasurable flexible modal variables,external interference and actuator failure in the design of the attitude controller.The attitude control problems of flexible spacecraft are considered in this thesis.It mainly contains the following aspects.The attitude control problem of flexible spacecraft is considered in two cases that modal variables are measurable and modal variables are not measurable.Based on the passive method,two attitude controllers without angular velocity measurement are designed to ensure the asymptotic stability of the closed-loop system.One is the partial state feedback controller with measurable modal variables and the other is the observerbased attitude controller under the condition that modal variables can not be measured.The effectiveness of two kinds of attitude controllers is verified by numerical examples,respectively.In order to stabilize the attitude of flexible spacecraft with external disturbance,based on the passive method and internal model principle,two kinds of internal model controllers without angular velocity feedback are proposed to eliminate the effect of external interference.Moreover,the closed-loop system is ultimately uniformly bounded.A disturbance internal model controller with partial state feedback is established when the modal variables are available.In addition,an observer-based internal model controller is developed when modal variables are not available.A numerical example shows that two types of attitude controllers can attenuate the external disturbance,effectively.For the partial effectiveness loss and additive fault of actuators of flexible spacecraft,by introducing a first-order differentiation filter,a nonlinear proportional integral controller with only attitude measurement is designed.Meanwhile,by combining a faulttolerant control method independent of angular velocity amplitude measurement,the faulttolerant attitude controller is constructed to eliminate the influence of actuator faults such that the fault-tolerant attitude stable control of flexible spacecraft is realized.The simulation results show that the fault tolerant controller can deal with the actuator fault of the system,effectively and then illustrate the effectiveness of the fault-tolerant attitude controller.