Research On Spatial Modular Mechanism Based On 2-DOF Deployable Unit

As a new kind of mechanism,the deployable mechanism was born with the continuous development of space technology and modern mechanism in the past half century,and it has been widely used in aerospace,civil construction,medical devices and other fields.In order to design a new spatial truss deployment mechanism with high folding rate,2-DOF modular deployable unit is proposed,and configuration synthesis of 2-DOF unit,kinematics analysis and topological characteristics analysis of deployable mechanism are accomplished in this thesis.The theoretical basis and calculation method are provided for design and analysis of spatial truss deployable mechanism in this thesis,and the details are as follows:(1)Configuration analysis and synthesis of 2-DOF unitAccording to the analysis results of degree of freedom,geometric compatibility condition and folding conditions of 2-DOF deployable unit,the correctness of the configuration principle is verified.Then,the configuration synthesis of 2-DOF unit is carried out,and four modular configurations are proposed and verified by UG kinematics simulation,which includes onedimensional linear deployment,horizontal-longitudinal deployment,radial deployment and circular deployment.Two motion modes are analyzed,which are simultaneous movement and sequential movement,and innovative design of mechanism is realized.Finally,the combination conditions of two 2-DOF units are studied,and trajectory equations of combined mechanism are derived,so that the deployment trajectory can be arbitrary by this method.(2)Kinematics analysis and driving strategy selection of mechanismsOne-dimensional linear deployable mechanism with a single 2-DOF unit is selected as the research object,which is simplified to a planar mechanism describing its kinematic characteristics.Based on the closed-loop vector method,the kinematic model of the object is established,and the trajectory equation of each node is derived.Then,the motion of the object under constant speed driving strategy is studied,and the conclusion is drawn: singularity occurs in initial closing state,but the motion is not interfered by it;the motion can be realized correctly by constant speed driving strategy,but the initial movement of object is instable.Finally,according to analysis results of angular velocity curves and angular acceleration curves under trapezoidal driving strategy,polynomial driving strategy and cycloid driving strategy,a combined driving strategy is proposed,and the motion of the object is improved effectively.(3)Analysis of topological characteristics of mechanismsFirstly,three kinds of matrix describing topological characteristics of the spatial truss deployable mechanism are established by graph theory,and the topological transformation of the research object is studied by its row-column operations.The transfer of internal topological characteristics of mechanism is revealed by the method of metamorphic principle.Secondly,evolution equations describing the above operations are derived,and the computer solution of topological analysis is realized.Finally,the space compactness,dynamic sensitivity and stiffness of the object are analyzed,and the inherent properties of truss mechanism are revealed.(4)Application of 2-DOF deployable unitDue to the lack of fixed garage and the risk of open-air parking at present,a portable deployable tent for vehicles is designed and the design method of supporting truss mechanism for vehicle tent is proposed.Then,the dimensions of each link in the truss mechanism are solved based on a certain vehicle.At last,a method of self-locking of hinge at specified angle is proposed.