Active Vibration Suppression And Attitude Control Of Flexible Spacecraft

In recent years,with the continuous development and implementation of complex space missions such as deep space exploration and space debris removal,spacecraft structures have developed in the direction of large-scale and complex.Because the weight of these large spacecrafts is limited by the carrying capacity of the vehicles and the cost control,they are often equipped with lightweight flexible attachments.For such flexible spacecraft,due to space interference and the coupling effect of flexible vibration and central rigid body,its normal operation has become a challenge.The necessary condition for the spacecraft to successfully complete its mission is that its attitude control must meet the relevant requirements.Therefore,this paper mainly studies the vibration suppression and attitude control of flexible spacecraft,mainly including the following:First,some definitions,lemmas,and basic knowledge commonly used in the following research are given.Then,the definitions of several coordinate systems needed to establish the attitude dynamic equations of the flexible spacecraft are briefly given.Finally,the dynamic model of flexible attachment vibration,the attitude dynamics and kinematics model of flexible spacecraft are given.Aiming at the problem of vibration suppression,considering the vibration control of the flexible structure,an active vibration controller based on independent modal space is designed.First,considering that the modal velocity is difficult to obtain in practice,the Luenberger state observer is designed to observe it.Further,the coupling effect between the flexible attachment and the central rigid body and the external interference received are regarded as total interference and the vibration controller is designed based on the prescribed performance method.Numerical simulations show that the designed active vibration controller can effectively suppress the vibration of flexible accessories under different types of interference,and has the advantages of strong robustness and fast vibration attenuation.For the attitude control problem,the sum of the coupling effect of flexible vibration and external interference are approximated by using neural network.Then,the finite time attitude controller of the flexible spacecraft is designed using a prescribed performance method and a finite time performance function.The two sets of simulations of attitude tracking and attitude stability control show that the designed controller can meet the expected dynamic process and achieve the characteristics of steady-state accuracy in a limited time.Although the attitude of the flexible spacecraft can be well satisfied by the controller designed above,it is found in the simulation that the vibration of the flexible attachment is still relatively large and exists for a long time.In order to solve this problem,a compound control strategy of attitude control and vibration suppression is designed.In order to reduce the difficulty of practical application,it is considered to use only piezoelectric actuators and not piezoelectric sensors,so a modal observer is designed to observe the modal information,based on the observed modal infromation,the vibration suppression controller is designed,combined with the attitude controller,the compound control strategy get,and the stability of the entire closed-loop system is analysed by Lyapunov stability theory.Comparing the simulation results with that without vibration suppression,it can be found that the designed composite controller can not only achieve the requirements for attitude control,but also ensure the rapid attenuation of the vibration of the flexible attachment.