Design Method For Configuration And Cable Drive Of A Class Of Deployable Mechanisms

The deployable mechanism,as an indispensable part of all kinds of spacecrafts,has always been a research focus among scholars all over the world.With the rapid development of various space exploration missions in China in the new era,the demand for new types of space deployable mechanism continues to emerge.Existing relevant studies still have some limitations in the aspect of topological representation,type synthesis method and the widely used cable-drive.In this case,further researches on the basic theory and engineering technology of space deployable mechanism are urgently required.Taking one class of deployable mechanisms as the research object and,in-depth research was carried out in this study from the aspect of mechanism configuration and cable drive,which focused on some key issues such as topology structure representation,configuration synthesis method,the analysis of cable drive performance,and the deisgn of a novel hinged boom and the deployable skeleton.The main research contents are as follows.Given the difficulties in describing the complex kinematic chains(i.e.,multiple joints)in deployable mechanisms,a modified topological graph with "face"—PF graph(Planar Face Graph)is proposed in this study.Besides,relevant definitions and geometric representation methods of PF graphs are introduced,and some concepts and properties are also described.Moreover,a new method to eliminate multiple joints is also proposed based on PF graph and tree graph,which is convenient for the generalization of kinematic chains.In addition,the necessary and sufficient conditions for isomorphism of graphs are studied,and two important properties of permutation similarity are proposed.Furthermore,two isomorphism identification methods(modified eigenvalue eigenvector method and maximum path method)are proposed,and a new isomorphism identification algorithm is obtained by combing these two methods,which ensures both reliability and efficiency.In order to improve the comprehensive efficiency of type synthesis and unify the configuration synthesis method of planar single-multiple joint kinematic chain,the singleopen-chains adding method is modified based on the proposed PF graph.Firstly,the structural formula is modified,thereby improving the allocation method of the multiple joint factor and the length of the single open chain in the traditional single open chain superposition method.Then,a modified method for generating the connection matrix in the single open chain superposition method is proposed,and finally a new method of type synthesis that is applicable to single-multiple joint kinematic chain is obtained.Taking the innovative design of the SAR antenna in the space deployable mechanism as an example,this paper illustrates the general steps of mechanism synthesis through improving the superposition of single open chain,which builds a theoretical foundation for the innovative design of the space deployable mechanism with multiple joints.This paper focuses on cable drive that is widely used in the deployable mechanism.The types and preloading methods of cable transmission are summarized,and according to the different types of cable drive and preloading modes,the distribution of tension and the relationship between the initial expected force and the pretension after no-load operation are obtained based on analysis of preload of cable transmission.Considering the uneven distribution of preload,a variety of new stiffness models are proposed,and the corresponding stiffness formulas are deduced,which are more accurate than the previous stiffness model that uses.preload as uniform tension.Based on the cable drive model in the synchronous joint of the new SAR antenna,the relationship between each design parameter and the cable drive stiffness is analyzed,which provides a theoretical basis for cable drive design.In addition,the stiffness test is carried out to verify the reliability of this study.To deal with uncontrollable trajectory,a new type of hinged boom that can be unfolded synchronously is proposed.Firstly,the cable drive is equivalent to a four-bar mechanism.Based on the single-open-chains adding method,the structure of the cable drive mechanism is synthesized,and various configurations of cable drive are obtained.Then the final configuration of hinged boom was obtained by optimizing the configuration and multi-mode motion design of the configuration based on the metamorphic principle.The tension distribution and stiffness formula of the cable drive are obtained.The dynamics of the mechanism is analysed by Adams,and the validity of the simulation and the reliability of the mechanism are verified by zero-gravity deployment test.To obtain a large membrane deployable mechanism,the type of the framework is synthesized by adopting the virtual chain method—a kind of type synthesis method of parallel mechanisms.Through optimizing configuration,the design of hinged boom based on cable drive is inherited,and the membrane deployable skeleton is designed in detail.Moreover,the modal analysis of deployable skeleton is carried out to meet the requirements of launch and working conditions.In addition,the flexible dynamics of the deployable mechanism is analysed and the deployment time and dynamic characteristics are obtained,and a prototype was developed and verified by a deployable test.To sum up,this paper has carried out in-depth research on a class of spatial deployable mechanisms from the aspects of topology structure description,type synthesis method,cable drive performance analysis,a novel hinge boom and a large membrane deployable mechanism,etc.,which provides feasible methods and ideas for the design of space deployable mechanisms.