Dynamic Characteristic Analysis And Nonlinear Restoring Force Identification Of Hinged Truss Structure

With the development of space missions such as manned spaceflight,lunar exploration and so on,aerospace science and technology has been changing with each passing day and aerospace structure tends to be large-scale,flexible and high-precision.Large deployable structures have been widely applied in aerospace field with the characteristics of high deployment accuracy,light weight and high strength.The limitation of transportation technology requires a large folding ratio of deployable structures,which results in a large number of hinges in the structures.Hinged truss structures are the earliest and most widely used one-dimensional space deployable structures.In this paper,the dynamic characteristics of one type of hinged truss structure has been studied.The main research work has carried out in the following aspects.Firstly,the influence of test conditions on modal parameters of truss structure is analyzed through modal testing.The components of the truss structure and its basic parameters are briefly introduced.The experimental modal analysis of the structure was carried out using the hammer method,and the low-order modal parameters and modal shapes of the structure were obtained.Changing the free-free boundary conditions,the influence of the suspension conditions and the position of the response point on the modal testing results is analyzed,which provides a reference for the ground modal testing of large-scale flexible structures.The additional stiffness will be introduced by suspension system.A method based on Sherman-MorrisonWoodbury(SMW)formula is proposed for eliminating the additional stiffness of suspension effects.The method is verified by numerical simulation and modal testing.Secondly,the axial and torsional stiffness of the structure are obtained by static test of the truss structure,then compared with the simulation results.Based on the simulation results,the equivalent dynamic beam model of the truss structure is developed.According to the characteristics of the truss structure,the truss tensile clamp was designed.The tensile test was carried out by tensile tester.The tensile stiffness of the structure was obtained by data fitting.The truss structure is simplified and the quarter structure is used for compression test.The compression stiffness of the truss structure is obtained.A torsion clamp was designed for the single frame structure of the truss.The torsion test was carried out by using a torsion tester.The torsional stiffness of the single frame structure was obtained.The above three stiffness obtained from static tests are compared with the simulation results.Based on the simulation results,the 2D equivalent Euler-Bernoulli beam model of the truss structure is established and compared with the natural frequency obtained from simulation and experimental.Finally,the dynamics test of the truss structure is carried out.Using the obtained system response signal in the time domain,the restoring force surface is established and the system parameters are identified.A dynamic test scheme is designed for the truss structure,and the acceleration,displacement and excitation signals in the time domain of the structure are obtained,speed signal is obtained by differentiating the displacement signal.The system stiffness with the external excitation level is analyzed by the displacement-recovery force relationship.With the increase of excitation frequency,the stiffness of the system shows obvious non-linear characteristics.The nonlinear restoring force surface of the system is obtained by processing the experimental data.The stiffness and damping of the system is obtained by the cross-section method,which provides a reference for studying the nonlinear characteristics of the hinged structure.