Design And Experimental Research On Truss Structure For Modular Space Deployable Antenna

Space deployable structures are the essential aerospace equipment to space exploration activities. Space deployable antenna is one of the most active research fields of space deployable structure, which has the huge development potential. Space deployable antenna is a new type of space structure, which is produced with the rapid development of aerospace science and technology in recent years. From then on, many countries and institutions have paid more attention to this research field. Taking truss structure of modular space deployable antenna as the research object, configuration synthesis and optimization of basic frame for space deployable antenna, spatial geometry modeling of truss structure, dynamic characteristics analysis, structural optimization and deployment precision test have been studied in this paper.Configuration creative design of deployable antenna is the most basic problem of related theoretical research. Truss structure is usually composed of several modules or basic frames. To design novel deployable antenna, taking six typical basic frames as the research foundation, four kinds of topological graph models of basic frame are obtained based on graph theory. The topological symmetry of members and kinematic pairs are analyzed. The synthesis method of basic frame for deployable antenna is proposed. According to the design requirements of basic frame for modular structure, comprehensive evaluation models are built, then an optimal configuration is obtained.To ensure the surface precision and improve working efficiency, spatial geometry model of truss structure is presented. To solve the problem of the difference between the shape of the paraboloid working surface and the spherical truss structure, a fitting method of working surface is proposed. Then the truss structure is classified into two types: the same size module and different size module, spatial geometry models of truss structure are presented based on the homogeneous coordinate transformation method. The influencing factors on connection deviation of the same size module are analyzed, and the adjusting method of that is proposed. Geometry model of different size module is verified.Modular deployable antenna has two characteristics: large aperture, weak stiffness, so in the course of attitude adjustment and on-orbit operation of antenna, many dynamic problems may be produced such as coupling interference between antenna and satellite, and impact vibration under space debris. The finite element model is built by using ANSYS software. The modal analysis of truss structure was carried out, and the natural frequencies and corresponding vibration modes of structure are obtained. The harmonic response analysis is carried out by full method. At last, the influence of structure parameters such as center beam, chord, diagonal beam, vertical beam and crossing cable on natural frequency of structure is studied, and the method to improve the first natural frequency is proposed.Mass and deployment stiffness are two important parameters for deployable antenna. Taking the mass and the first order natural frequency as the objective functions, the structural parameters of truss structure are optimized. At first, according to the basic idea of BP neural network, prediction model is constructed, and generalization capacity of neural network is tested by means of testing samples. Then, sub-goals multiplication and division is adopted to unify the multi-objective optimization to a single-objective function. The optimization analysis is performed by genetic algorithm, and the design parameters of truss structure are obtained. On this basis, the driving mechanism and module structure are designed.A set of truss structure prototype of modular deployable antenna and zero gravity simulation mechanism are manufactured successfully. Deployment precision test and dynamic test of truss structure are carried out. Spatial coordinates of key point are obtained by photogrammetry. Surface precision, repeated deployment precision and errors of key point are analyzed, then experimental results and theoretical analysis are compared with each other. Using the way of single input multiple output, modal experment of truss structure is carried out in free state. Comparing with the experimental results, the results show that the finite element model is right.