The Stiffness Identification And Experimental Study Of Space Deployable Structure With Spherical Hinge

In recent years,with the development of space missions such as on-orbit servicing and deep space exploration,large deployable trusses have been widely applied due to the characteristics of high precision and high folding rate,such as the supporting structure of large diameter satellite antennas,the unfolding supporting arm of the flexible solar panel and so on.The stiffness of deployable structure plays a critical role in maintaining stable structural configuration after unfolding.The stiffness of the spherical hinge has an important influence on dynamics characteristics of deployable structures.In this paper,the stiffness characteristics of one type of deployable truss with spherical hinge has been studied.The main research work has carried out in the following aspects.Firstly,one type of deployable truss with spherical hinge has been designed,and its components and movement principium have been introduced.In order to ignore the influence of cables and locking devices,and reduce the difficulty of the analysis problem,the bilateral corner nodes in the deployable structure were processed by mirroring,obtaining the simplified structure model under the locking state.The following research were based on the simplified structure model.Through carrying out the finite element modeling and contact pair definition for this locked truss unit,by means of appropriate working conditions choosing to get the axial stiffness of the locked truss unit,compared with the theoretical axial stiffness deduced from the equivalent beam modeling method based on the energy equivalent principle and the Winkler elastic foundation method,verifying the accuracy of the finite element contact analysis method for the study of the overall stiffness of the deployable structure.Secondly,through the study of the overall stiffness characteristics of the deployable unit,it is found that the spherical hinge connection has an obvious weakening effect on the stiffness of the deployable unit.Therefore,the stiffness of the spherical hinge has been identified.Firstly,establishing the elaborate FEM of a locked truss unit and calculating the initial stiffness values by carrying out the contact analysis,then substituting the initial value to the parameterized model with CBUSH elements linearizing the connection of the spherical hinges.Afterwards,carrying out the model tests for locked deployable structures,and using these modal parameters to identify the stiffness of the spherical hinge.Finally,utilizing the identified stiffness for the finite element modeling of deployable structure,and verifying the identified results by using multi-layer's modal parameters.On the identified results,the method is extended to the multi-frame deployable structure.The stiffness of spherical hinge is identified based on the finite element model updating method based on absolute sensitivity analysis and relative sensitivity analysis respectively.The results show that for multi-frame deployable structure,the model updating based on relative sensitivity is more applicable,and the identified results are more accurate and reasonable.Finally,the study of model updating considering spherical hinge uncertainty is carried out,based on the identified results of stiffness of spherical hinge of multi-frame deployable structure.By using the interval model to describe the uncertainty of spherical hinge,according to the experimental samples obtained by the full factor design method,constructing the complete second-order polynomial response surface model evaluated by the complex correlation coefficient R² and modified complex correlation coefficient R²_adj as the substitute model of deployable structure to carry out the model updating considering the spherical hinge uncertainty.The interval parameters of spherical hinges are effectively identified by optimizing the design samples and the range of parameters.The identified results are verificated by comparing with the experimental samples.The research shows that the model updating method of interval parameter structure based on multi-stage response surface model is applicable to large structures such as multi-frame deployable truss and so on,which can effectively identify and quantify the uncertainty of structural parameters.