| The space deployable and foldable mechanism that can be unfolded from the folded and closed state to the intended working state is of great research value.In the international astronautical community,there is an urgent need to design a new type of space deployable and foldable mechanism.This paper,based on the principle of bionics,designs a new spiral space deployable and foldable mechanism by observing the rolling up and stretching movements of the elephant trunk and abstracting the shape of the elephant trunk after rolling up.The theoretical analysis and application research of this mechanism are also conducted.Firstly,a design of a spiral space deployable and foldable mechanism is proposed by extracting the functional characteristics of the extension and rolling up of the trunk.The main structure of the trunk frame is extracted.Based on the Assur rod group method,the connection between the modules is designed.The basic module is modified and the motion transfer is taken into account to obtain the final folding unit.The configuration conditions required to complete the function of the mechanism are analyzed and discussed.The degrees of freedom of the mechanism are analyzed.This is followed by a detailed design of the intermodule connections,limit blocks and spring pins,and the design and 3D modelling of the whole mechanism.Next,the kinematic model of the mechanism is developed and the deployable space analysis method is given.The geometric analysis of the folding unit is carried out,based on which the local coordinate system is established for the analysis of forward position,velocity and acceleration,and the inverse position of the module clamping angle and slider travel is analyzed.Then the global coordinate system is established,and the positive position is analyzed based on the D-H method.The velocity and acceleration are analyzed based on the velocity Jacobi matrix.The motion simulation of the mechanism is analyzed to verify the accuracy of the established mathematical model.The outer contour of the deployable space of the mechanism is obtained based on the global search boundary,and then the area of the deployable space is calculated based on the cubic spline interpolation and Monte Carlo method to determine the space occupied by the folding motion process.Again,the dimensional synthesis study is performed to obtain an interference-free deployable and foldable mechanism with a higher stowage rate.The intrinsic law of each parameter’s influence on the shape of the spiral is investigated.Based on the kinematic analysis,the design variables are optimized.The maximum unfolding length is used to establish the objective function.The spiral range,as well as the distance between the inner and outer rings of the spiral is restricted.Other constraints are determined from the previous geometric analysis and the spiral shape analysis.The optimized model is solved based on a genetic algorithm.The results are analyzed and the optimal solution is plotted and analyzed to determine the parameters of the mechanism and to calculate the stowage rate.Then,the mechanism deployable position accuracy reliability analysis is performed.The differential method is used to establish the functional relationship between the rod length error,input parameter error,and motion pair clearance error,thereby the reliability model is given.A specific example is used to analyze the deployable accuracy of the mechanism and calculate the reliability of the deployable position accuracy in different cases,which provides an important theoretical basis for the implementation of its practical application.Finally,the spiral mechanism is used as a skeleton for application research,a sun wing,a deployable antenna,a folding bridge,a folding awning and a threefinger gripper are designed.And the auxiliary driving device of the mechanism is designed,showing that the space deployable and foldable mechanism can be applied to a variety of fields,reflecting its value and significance of use. |
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