Mechanical-thermal Property Analysis And Modal Parameter Identification Of Space Deployable Structure

Under the cyclic mechanical-thermal condition,the hopping phenomenon of the pointing accuracy for space deployable structure with clearance joints has emerged,and it seriously affects the pointing accuracy of the structure.In addition,the difference between the modal parameters of the control model and the real modal parameters seriously affects the accuracy of the in-orbit control for the structure.Then,in order to implement the high pointing accuracy and the high-accurate control of the structure,the mechanical-thermal property and modal identification of the structure are investigated in this paper.The specific contents and results are as follows:1.The intrinsic mechanism of the multiple static-equilibrium state phenomenon for the structure is revealed according to the theory of statics.First,the influence of the clearance joint on the degree of freedom of the deployable structure with clearance joints is analyzed.Second,the geometric constraint equations and the static equilibrium equations are listed,and the constraint conditions of contact force and friction are given.Third,the static equilibrium positions of the structure under given loads are obtained by combining the constraint equations and the constraint conditions.Finally,the numerical results indicate that the phenomenon is caused by joint clearance and friction.The larger the static friction coefficient is,the more equilibrium positions the structure has and the more serious the phenomenon is.2.The intrinsic mechanism of the mechanical-thermal hopping phenomenon for the structure is revealed according to the theory of dynamics.First,the momentum exchange approach,Lankarani-Nikravesh contact model and Ambrosio friction model are used to model the joint clearance.Second,Lagrangian method is used to obtain the dynamic equations of the deployable structure with clearance joints and the solution process of the equations is given.Third,the dynamic performance of the structure is investigated under the cyclic mechanical-thermal condition.Finally,the numerical results indicate that the phenomenon is caused by joint clearance and friction.The larger the joint clearance size and the sliding friction coefficient are,the more serious the phenomenon is.3.An improved covariance-driven stochastic subspace identification method is proposed.First,the identification processes of data-driven and covariance-driven stochastic subspace method are compared.Second,the singular value decomposition of Toeplitz matrix in the covariance-driven stochastic subspace method is investigated.It is found that one of the submatrices obtained from Toeplitz matrix has no effect on the modal identification results,thus the dimension of Toeplitz matrix is reduced by reducing the dimension of the submatrix.Third,the finite element model of space deployable mast is used to verify the effectiveness of the improved method.Finally,The numerical results indicate that the improved method dramatically improves the computing efficiency and still keeps accuracy.