Research On Dynamic Modeling And Related Issues Of Flexible Spacecraft

With the development of aerospace industry,more and more missions are undertaken by various spacecraft,which makes the configuration of spacecraft more and more complex and large-scale.Many spacecraft are equipped with multiple large flexible accessories,which are light in weight,low in stiffness and small in damping.There is a coupling effect between the elastic vibration and the system motion.Because the inertial action caused by the flexible deformation of the flexible accessory structure may lead to the motion instability of the flexible spacecraft,therefore,the research on the rigid flexible coupling of the flexible spacecraft system is the focus of the dynamic research of the flexible spacecraft.The influence coefficient of flexible coupling in dynamic modeling of flexible spacecraft is an important mechanical concept in dynamic modeling,which reflects the elastic vibration effect of spacecraft attitude and orbit motion and flexible accessories.The equivalent relationship between the influence coefficients of the flexible coupling,i.e.the inertial completeness criterion,is an important basis for the reduction of the order and the mode truncation of the dynamic model of the flexible spacecraft.In this paper,the dynamic modeling of a spacecraft with flexible appendages is studied.Firstly,the attitude motion of spacecraft is described by hybrid coordinate method,and the system kinematics equation is established.The system vibration is expanded by using constrained mode method and unconstrained mode method,and the system dynamics equation is established by combining Newton Euler method and Lagrange equation.Then,based on the research results of Hughes,the inertial completeness criterion of constrained modes is deduced,and its effectiveness is verified by simulation analysis.Through the Laplace transformation of the dynamic equations of the two modes of the system,the relationship between them is discussed.Combined with the inertial completeness criterion of the constrained mode,the inertial completeness criterion of the unconstrained mode is derived in detail.Taking the two models of the central rigid body with solar sails on both sides and the single side as examples,the unconstrained mode simulation calculation and analysis are focused on The influence of the change of the inertia ratio between the flexible attachment and the central rigid body on the effectiveness of the inertial completeness criterion of unconstrained mode is discussed.Finally,through the concept of system inertia,the relationship between the natural frequency of unconstrained mode and the parameters of constrained mode is deduced,and the formula of solving the basic frequency of unconstrained mode by using the parameters of constrained mode is improved.Taking the two models of the central rigid body with two side solar sails and one side solar sails as examples,the simulation calculation and analysis are carried out,and the flexible accessories and the inertia of the central rigid body are discussed The influence of the change of the ratio on the applicability and validity of the basic frequency formula of the unconstrained modes of the system.