Topology Structure Synthesis and Analysis of Spatial Pyramid Deployable Truss Structures for Satellite SAR Antenna

Many attentions for structural synthesis are paid to planar linkages and parallel mechanisms, while design novel pyramid deployable truss structure（PDTS） of satellite SAR mainly depends on experience of designer. To design novel configuration of PDTS, a two-step topology structure synthesis and analysis approach is proposed. Firstly, a conceptual configuration of PDTS is synthesized. Weighted graph and weighted adjacency matrix are established to realize topological description for PDTS. Graph properties are then summarized to distinguish differentia between PDTS and other type structures. According to graph properties, a procedure for synthesis conceptual configuration of PDTS is presented. Secondly, join relationship of components in a PDTS is analyzed. Kinematic chain and corresponding incidence/adjacency matrix are employed to analyze join relationship of PDTS. Properties and simplified rules of kinematic chain are extracted to construct kinematic chain. A procedure for construction kinematic chain of PDTS is then established. Finally, with this two-step approach all 11 rectangular pyramid deployable structures whose folded state is planar are discovered and their kinematic chains are constructed. Based on synthesis results, a novel deployable support structure for satellite SAR is designed. The proposed research can be applied to obtain some novel PDTSs, which is of great importance to design some novel deployable support structures for satellite SAR antenna.

Nonlinear Dynamics Analysis of Joint Dominated Space Deployable Truss Structures

Joints are necessary components in the larger space deployable truss structures which have significant effect on the dynamics behavior of these deployable joint-dominated structures. Four kinds of joints' nonlinear force-displacement relationship are analyzed based on describing function method. The dynamic responses of one-DOF jointed system under different exciting force levels are investigated to understand the influence of joint nonlinearity on dynamic responses. The influences of joint characterizing parameters on joint nonlinearities are analyzed. Dynamic responses of the modular beam-like deployable joint-dominated truss structure are tested under different sinusoidal exciting force levels. The experimental results show obvious nonlinear behaviors contributed by joints that dynamic response shifts to lower resonance frequency and higher amplitude with the increase of exciting force. The nonlinearity of the joints in the tested structure is compared with the theoretical results and identified to meet with the hysteresis nonlinearity.

A Method for the Configuration Design of a Space Truss Deployable Mechanism and Its Application

A method based on the metamorphic principle is proposed for the analysis of the configuration design of a space truss deployable mechanism. The configuration change and correspondent topological graphs and adjacency matrixes at different work-stage of the mechanism, which is helpful to completely understand the composition and change rules of the metamorphic mechanism, are analyzed to indicate the metamorphic relationship in one working cycle. Furthermore, the static distance matrix, dynamic distance matrix and stiffness matrix of the mechanism are derived to assess the ability of the designed configuration to reveal some of the topological characteristics like compactness, dynamic sensitivity and stiffness. Using this proposed method in a space truss deployable mechanism helps the designer to evaluate its performance at the conceptual stage of design and make a rapid, reasonable selection for configuration design, which provides means for processing its type of analysis by computer.

Design and analysis of a truss deployable antenna mechanism based on a 3UU-3URU unit

Space deployable structures with large calibers, high accuracy, and large folding ratios are indispensable equipment in the aerospace field. Given that the single-DOF 3 RR-3 RRR deployable unit cannot be fully folded, this study proposes a 3 UU-3 URU deployable unit with two kinds of DOF: folding movement and orientation adjustment. First, based on the G-K formula, the DOF of the 3 UU-3 URU unit is analyzed. Then, the 3 UU-3 URU unit is used to construct a deployable truss antenna with a curved surface, and the DOF of the whole deployable antenna containing multiple 3 UU-3 URU units is calculated. The structural design of a deployable antenna with two loops is carried out with specific parameters and geometric relations. Next, a DOF simulation of a basic combination unit composed of three 3 UU-3 URU units is performed. Finally, a prototype of the basic combination unit is manufactured, and the DOF of the mechanism is experimentally verified.

Design and analysis of truss deployable antenna mechanism based on a novel symmetric hexagonal profile division method

As the deployment,supporting,and stability mechanisms of satellite antennas,space-deployable mechanisms play a key role in the field of aerospace.In order to design truss deployable antenna supporting mechanisms with large folding rate,high accuracy,easy deployment and strong stability,aiming at the geometric division of the parabolic reflector,a novel method based on symmetric hexagonal division and its corresponding modular truss deployable antenna mechanism is proposed,and the original method based on asymmetric triangular division and its corresponding mechanisms are presented for comparative analysis.Then,the screw theory is employed to analyze the mobility of different mechanisms.Furthermore,the improved three-dimensional mesh method is used to divide the reflector surface of a large parabolic antenna designed by the two different methods,and the profile accuracy and the type of links are taken as the evaluation indexes to quantitatively analyze the division results.Finally,a three-dimensional model of the modular deployable mechanism based on the symmetric hexagonal design is developed,and the deployable mechanisms with different configurations based on the two design methods are compared and analyzed from the mechanical perspective.The research results provide a good theoretical reference for the design of deployable truss antenna mechanisms and their application in the aerospace field.