Structure Design Theory And Thermal Control Study For Space Deployable Truss Structure

The large deployable structure is widely used in spacecraft because of its high ratio of compaction. Structure design and thermal control study are two basic tasks for a deployable structure when used in orbit. The task of structure design for a deployable structure is to satisfy the deployable requirement, and the task of passive thermal control study is to make thermal design based on the thermal characters of the deployable structure. Based on the former researchers' work, stage-design method is introduced for the structure design, and thermal transmitting equation and thermal elastic mechanics are adopted for thermal control study. Thermal static mechanics theory and non-coupling dynamical theory are all used to analyze a deployable truss antenna model with paraboloid surface by thermal finite element method. Structure design, temperature field, thermal distortion and thermally induced vibration about the deployable antenna are all discussed.1. In order to ensure the deployable efficiency of structure and simplify the design process of deployable structure, different parameter targets to be fulfilled, the analysis model and relevant theory are introduced in three phases of the design process for deployable structure. In the three designing stage, (1) the primary assignment of concept design phase is selecting appropriate deployable/retractable scheme according to design requirement. The primary parameter targets to fulfill of this phase are the deployable mobility possibility (DMP) and the retractable mobility possibility (RMP), and then by using the generalized inverse theory, a topological model is analyzed to structural shape control; (2) the primary assignment of model design phase is to ascertain the detailed size of bars and joints by deployment mechanism and to make a practical model. The primary parameter target to fulfill of this phase is the harmony among bars and joints (HBJ) and the structure has good structural mechanics characters. The multi-body dynamic theory is used to analyze the movement of the structure model; (3) the primary assignment of optimization phase is optimizing modified model. The primary parameter targets to fulfill of this phase are various practical targets, and then the optimization analysis is developed by using optimization theory with the restriction function of various practical targets. At last, Adjustment mechanism of the imaging lens's focal length of a space telescope, deployable mast, and deployable truss paraboloid antenna are analyzed by combining three phases design process.2. The element shadow areas of deployable structure are analyzed and a finite element program for space deployable structure temperature field is compiled. The whole thermal characteristic of space truss deployable antenna is analyzed by using thermal static mechanics theory and thermal finite element method. According to the thermal material's infection to the character of the deployable truss antenna, the basic passive thermal design rules of the deployable truss antenna are introduced: (1) because the temperature distribution is rather non-uniformly, the extremum temperature region index is proposed. According to the working temperature of each parts of antenna, and paying attention to the degradation of thermal control coating, the designing extremum temperature region is decided; (2) according to the relationship between the value α/ε ofthermal control coating and extremum temperature region of the antenna, a basic thermal control coating is chosen; (3) the material characteristic of back truss has little influence to the extremum temperature of reflecting surface, so the material of back truss with low coefficient of thermal expanding is selected independently in initial stage.3. In order to judge the accuracy of the iterative solution for the finite element equation (non-linear differential equation) about the transient temperature field, and combined with the characters of the space deployable structure, two additional convergence criterions are proposed. By using the non-coupling dynamical theory to analyze the thermally induced vibration of the deployable truss antenna, transient loads caused by transient temperature are introduced and are applied to the structure by multi-nodes transient loads form. Analysis results show that: (1) the rotating angle of the node caused by thermally induced vibration is obvious than the translational displacement, and is similar to the low order free vibration of the structure; (2) the thermally induced vibration can be adjustment by changing the restriction of the structure without changing the physical character of the structure.