Dynamic Characteristics Of A Kind Of Slender Truss Spacecraft

With the development of space industry and the increasing demand for space,large-scale and lightweight has become the main direction of development of modern spacecraft.Because of its advantages of lightweight,extensible and high stability,large space truss structures have been widely used in aerospace field.In this paper,the flexible spacecraft with large truss antenna structure is taken as the research object.In order to realize the accurate dynamic modeling of flexible spacecraft,this paper puts forward the equivalent modeling method based on the energy equivalencel principle,on this basis,the mechanical properties of the truss antenna structure are analyzed.Finally,the rigid flexible coupling dynamic model of flexible spacecraft is established.The main contents in this dissertation are listed as following.According to the periodic structure characteristics of slender truss antenna,an equivalent beam model modeling method based on the principle of energy reciprocity is proposed.The equivalent stiffness parameters and the mass parameters and the corresponding coupling parameters of the equivalent beam model are deduced by the equivalence of the strain energy and kinetic energy of the truss period unit and the equal length beam section,and then the equivalent anisotropic model of slender beam space truss antenna structure is established.By comparing the dynamic characteristics of the equivalent beam model with the original truss antenna structure,the validity of the equivalent method and the reliability of the equivalent beam model are verified.Then,the factors affecting the natural frequencies of truss structures are analyzed,and the effective measures to improve the natural frequencies of slender truss structures are obtained.Finally,the dynamic responses of truss structures under several typical excitations are analyzed on the basis of equivalent beam model.A flexible spacecraft with a slender truss antenna attachment is simplified as a central rigid body with flexible beam model,and the rigid-flexible coupling dynamic equation of single axis rotation is established by using the Hamilton principle.On the basis of linearized coupled dynamic equations,the analytical expressions of the rigid-flexible coupling modes are derived.To facilitate the analysis of the dynamic response of the coupled system,the discrete form of the dynamic equations of the coupled system is obtained by means of modal discretization and finite element discretization respectively.The natural frequencies of the system obtained by the finite element discrete model and the rigid-flexible coupling modal analysis method are compared and analyzed.The convergence of the finite element method is analyzed,and the accuracy of the rigid flexible coupling modal analysis method is verified.The influence of the inertial characteristics of flexible spacecraft on its inherent characteristics is discussed,and the variation law of the natural frequencies of each order with the inertial characteristics is obtained.Finally,the dynamic response of flexible spacecraft under step control torque is studied.