Research On Cable-strut Tension Antenna Mechanism Based On Quadriprism Deployable Unit

With the rapid development of China's aerospace industry,large deployable antennas are an effective way to meet the needs of space power generation capability,precision strike capability,space reconnaissance capability,earth observation resolution,satellite communication distance and data capacity.However,the existing deployable antennas cannot meet the development needs in size,performance and weight.The main reason is that the volume of rocket fairing is limited,which requires the space folding mechanism to have the advantages of high accuracy,light weight,small volume of folding and so on.Throughout the most widely used large deployable structures in China,there are mainly three types of mechanisms: truss,inflatable and integral tension.The mass of truss mechanism increases with the increase of antenna aperture in square or cubic relation,which does not meet the requirement of lightweight.Although the inflatable antenna structure has advantages in weight and volume,it still has shortcomings in space environment adaptability,surface accuracy and structural stability.The whole tensioned structure is deficient in expansibility,unfolding drive and structural stiffness.Therefore,it is necessary to make breakthroughs in configuration design,dynamics analysis and structural optimization.In this thesis,a cable-strut tensile hoop deployable antenna structure is proposed,and its practical feasibility is analyzed empirically.In this thesis,the conceptual configurations of linear foldable deployable quadrilateral prism elements are synthesized systematically based on graph theory according to the three-step method of "statically indeterminate truss atlasdeployable element bicolor topological graph and determination of kinematic pairs".According to Maxwell's theorem,the relationship between the number of edges and the number of vertices of statically indeterminate geometrical bodies is given,and the automatic generation flow of statically indeterminate truss atlas of deployable elements is established.Based on the idea of embryo gram interpolation method,the algorithm of generating the deployable element atlas of linear folded quadrilateral prism is established.The local complete graph at each vertex of deployable unit is simplified into a mechanism tree,and then the connection relations of each vertex are combined to establish a two-color topological graph of deployable unit and configure the unit motion pairs.Finally,the configurations of 32 statically indeterminate quadrilateral deployable elements and 3 six-foldable-rod-type statically indeterminate quadrilateral deployable elements are obtained.On the basis of conceptual configuration of the unit,the number of spherical joints,universal joints,rotating pairs and moving pairs contained in the overconstrained units is calculated.Based on the Screw theory and virtual work principle,the posture relationship between each kinematic pair screw and overconstrained screw under the condition of force overconstraint and force couple overconstraint is solved,and the kinematic pair assignment table which can be satisfied under 13 kinds of overconstrained conditions is obtained,thus the kinematic pair assignment flow of deployable units with overconstraint is established.Based on this process,10 new 6-foldable-bar linear foldable quadrilateral prism elements are obtained,and the correctness of the proposed kinematic pair configuration method is verified by making 3D printing model and carrying out expansion and closing experiments.Based on the topological characteristics of spatial cable-strut tensioned stable structures,six topological characteristic conditions are proposed to be satisfied for the arrangement of struts and flexible cables in spatial stable structures.Combined with the previously selected truss element configuration,according to the symmetry of structure and the principle of balance of joint forces,aiming at the fact that flexible cables are not easy to be wound and the element stiffness ratio is the highest,a series of new cable-strut tension element configurations are proposed and the optimal configurations are optimized,which realizes the lightweight design of deployable mechanism elements.Based on the response surface method,the proxy mathematical models between the configuration parameters,structure parameters and the fundamental frequency of the antenna mechanism are established.Finally,the optimization process of antenna mechanism synthesis is established,and the antenna configuration with optimal stiffness and mass synthesis characteristics is obtained.In order to solve the contradiction between the extremely high degree of freedom of the dynamic model modeled by the traditional finite element method and the lower order of the model required for the design and implementation of the structural vibration controller,considering the in-plane and out-of-plane deformation of the antenna element mechanism,the cable-strut tensioned antenna element mechanism is equivalent to a spatial anisotropic beam model based on the principle of energy equivalence.According to the geometrical topology characteristics of the antenna,the equivalent spatial anisotropic beam element model is combined to form the dynamic equivalent model of the antenna.Finally,the correctness and rationality of the dynamic equivalent model and structure configuration proposed in this thesis are verified by unit test and 2m caliber prototype development and dynamic characteristic test,which provides a useful reference for the design of large caliber satellite antennas in aerospace engineering.