Research On Design And Singularity Elimination Method Of Large-scale Surface-deployable Mechanism

Due to some design defects or technical failures,some surface-deployable mechanisms can not achieve fully deployed status in engineering applications,which leads to the failure of preset tasks and brings huge economic losses.In order to improve the reliability and overall stiffness of the surface-deployable mechanism,a type of large-scale surface deployable truss mechanism is proposed.The configuration design,mobility analysis,deployment kinematics and dynamics analysis,and singularity elimination of the networking mechanism are studied in detail.According to the design requirement of large-scale surface,based on the principle of central projection,the theoretical model of deployable mechanism under fully deployed status is abtained.And it is proved that the unit profiles of the networking mechanism are all asymmetrical triangular prismoids.Aiming at the profile characteristics of the unit,the configuration design is carried out.Based on the planar symmetrical double 4R mechanism,supplemented by the spatial 7R mechanism and planar symmetrical double 5R mechanism,the triangular prismoid mechanism is constructed and the corresponding property of single mobility is verified with screw theory.In order to analyze its kinematics characteristics,the kinematics model of the deployable mechanism is establised by D-H parameter method and the expressions of position,velocity and acceleration of any particle in the mechanism are derived.Based on the kinematics analysis,the unfolding dynamic model of this mechanism mentioned in this thesis is further established.The expression between the driving torque and the relevant motion parameters is derived by using Lagrange method.Due to the potential motion singularity problem of truss-type mechanism mentioned in this thesis,aiming at the elimination methods of motion singularity,on the one hand,the elastic joints are designed to replace the rigid component with singularity,and the property of single mobility of the mechanism are verified by motion simulation and mobility analysis.On the other hand,two kinds of potential singular components removal schemes are proposed based on the large-scale networking mechanism.The motion simulation verifies that it does not affect the characristics of single mobility of the while mechanism.In order to further verify the deployable function of the original unit configuration and both the singularity elimination and the deployable performance improvement of triangular prism mechanism introducing elastic joints,the prototype of triangular prismoid unit is manufactured and assembled,and the test system is constructed for conducting the corresponding experiments.In summary,the large-scale surface truss-type deployable mechanism proposed in this thesis provides a new design idea for the single mobility deployable networking mechanism of the same type extended by the units.And the singularity elimination schemes proposed in this thesis also provide a certain reference value to the improvement of folding stability and reliability of mechanisms with multiple closed-loops and redundant constraints.