Research On Theory And Construction Method Of Deployable Mechanism Based On Loop Connection Of Quadrilateral Units

Deployable mechanisms are widely used in the fields of aerospace,military,construction,industry and in daily life,etc.,and realize the functions of launching,concealing,deforming,multi-mode operation,and artistic effects by folding,stretching,and zooming.With the development of the aerospace fields,the increase in military demand and the diversification of daily life demand,it is necessary to construct deployable mechanisms with different shapes,different functions,and different characteristics.Aiming at the connection requirements of the diverse units of the spatial deployable mechanisms,this paper mainly discusses the construction method of the loopconnected deployable mechanism based on two kinds of quadrilateral units.This paper studies and develops new construction theories and methods of deployable mechanism.Firstly,based on two types of double generalized angulated elements,planar centercoincident deployable mechanisms,spatial single loop-connected and spatial multiple loop-connected center-coincident deployable mechanisms are constructed,respectively.Secondly,based on the anti-quadrilateral units and anti-parallelogram units,the loopconnected mechanisms are constructed: Bricard-like mechanisms and the 8R-like mechanism,and the loop-connected mechanisms are used as sub-units to construct the polyhedron deployable mechanisms.The main research works are as follows:(1)According to the double generalized angulated elements satisfying the constraint condition with the same deployable center,the construction method of planar loop connection based on DGAEs I and DGAEs II,that is,the planar center-coincident deployable mechanism is proposed.The constraints of two DGAEs I connection and two DGAEs II connection with the same deployable center in the plane are analyzed,respectively.The constraints of sequence connection based on n DGAEs I and n DGAEs II with the same deployable center are analyzed,respectively.Loop-connected composed of n DGAEs I and n DGAEs II satisfy the constraints condition of the same deployable center are given,and then planar center-coincident deployable mechanisms based on n DGAEs I and n DGAEs II are constructed,respectively,through the kinematics analysis of single angulated elements,the deployable ratio of the planar center-coincident deployable mechanism is obtained.According to the constraints of DGAEs I and DGAEs II,the construction method of planar center-coincident deployable mechanisms based on cyclic polygon and circumscribed polygon are given by using the same deployable center and the same distance between deployable center to the intermediate hinge points.(2)It is proposed to construct the spatial center-coincident deployable mechanisms based on deployable axes with DGAEs I and DGAEs II,respectively.The constraints of spatial loop-connected based on DGAEs I and DGAEs II are analyzed,and spatial loop connections based on n DGAEs I and n DGAEs II,that is,the spatial spatial single loopconnected center-coincident deployable mechanisms are constructed,respectively.The spatial loop-connected are used as the construction subunit,and the connection constraints between the construction subunits are analyzed.According to the different constraints of DGAEs I and DGAEs II,the construction method of spatial centercoincident deployable mechanisms based on the multi-DGAEs I and multi-loops,and the construction method of spatial center-coincident deployable mechanisms based on the multi-DGAEs II and multi-loops are given,respectively.For the loop-connected based on DGAEs II,linear algebra method is given according to the relationship between the angles of the axes.Using this method,the relationships between all the loops and axes of spatial center-coincident deployable mechanisms based on DGAEs II are obtained,and the the patial center-coincident deployable mechanisms are constructed.(3)A construction method of Bricard-like mechanism based on anti-quadrilateral units is proposed by using one anti-quadrilateral unit to replace the two links and one revolute joint of Bricard mechanism.According to the plane-symmetric Bricard mechanism,the plane-symmetric Bricard-like mechanism based on an anti-quadrilateral unit and two identical anti-parallelogram units is constructed.According to the trihedral(generalized)Bricard mechanism,a trihedral(generalized)Bricard-like mechanism based on three different anti-parallelogram units is constructed.According to the planesymmetric Bricard-like mechanism and the trihedral(generalized)Bricard-like mechanism,a special loop-connected mechanism is proposed,a plane-symmetric-trihedral Bricard-like mechanism is constructed by using three identical antiparallelogram units.The Denavit-Hartenberg(D-H)parameters and closure equations are used to analyze the degrees of freedom of three types of Bricard-like mechanisms and the kinematic paths of the output variables,and the corresponding configurations of the kinematic paths are given,respectively.Finally,a triangular prism deployable mechanism,a regular tetrahedyon deployable mechanism,a regular octahedron deployable mechanism,and a regular icosahedron deployable mechanism were constructed by using the plane-symmetric-trihedral Bricard-like mechanisms as subunits.(4)A construction method of multi-modes 8R-like mechanism is proposed.A connection method of a multi-mode mechanism composed of four identical anti-parallelogram units and four revolute joints is given,as well as the D-H parameters and equivalent configuration of the mechanism: a patial 8R mechanism with variable links length.The degrees of freedom,the kinematic paths of the output variables,and their corresponding motion sub-modes of the two types spatial modes are analyzed according to the screw theory and closure equations.The bifurcation positions of Mode I and Mode II are analyzed,as well as the degrees of freedom during the bifurcation.Three planar modes are given based on singular positions of two generalized spatial modes: planar Mode III,IV,and V are given,respectively.The motion sub-modes of the three modes are given,and the relationship among different modes are proposed.The obtained multimode mechanism is used as a construction subunit to construct quadrangular prism deployable mechanism and hexahedral deployable mechanism.In summary,this paper systematically analyzes two kinds of quadrilateral units,and uses the quadrilateral units as the construction units to construct the loop-connected deployable mechanism.A new method of constructing deployable mechanism is proposed,the center-coincident deployable mechanisms have one deployable center,and the spatial center-coincident deployable mechanisms based on the deployable axis expands the construction method based on polyhedron.The loop-connected deployable mechanism based on the anti-quadrilateral unit and the anti-parallelogram unit has developed the construction methods of the spatial single-loop deployable mechanism.The deployable mechanism can also have broad application prospects in large-scale aerospace structures,military/medical tents,non-cooperative target capture institutions,etc.,and has important practical significance for broadening the application research in aerospace,military,medical and other key fields.