Analysis On Nonlinear Structral Dynamic Characteristics Of Planar Articulated Trusses For Spacecraft

Possessing with large shrinkage ratio,low mass and rigid stiffness,articulated trusses play an important role in aerospace missions.With the development of aerospace technology and diversification of pace missions,there is an increasing demand for work accuracy and stability of spacecraft structure,which closely related to the dynamic characteristics of the spacecraft.Therefore,precise and effective prediction of its dynamic behavior become necessary.Working in a latched state after deployment,natural frequency,mode shape and dynamic response of the articulated truss change significantly with the contribution of joint nonlinearity when a disturbance imposed,which make a fail task.Thus,nonlinear characteristics of revolute joint and its influence on dynamic characteristics of articulated truss will be investigated in this paper.Investigation of joint stiffness and damp characteristic,including vibration response of single-degree-of-freedom(SDOF)system,was placed in the first place.On the basis of Hertz contact model,the geometric constraint coordination was introduced to establish joint static stiffness mode.Based on the three-state mode of joint component motion,modeling of joint dynamic stiffness mode is performed,followed by a verification of joint static model and investigation of joint damp characteristic through FEM simulation.Subsequently,the describing function method(DFM)is applied to typical nonlinear forcedisplacement relationships and amplitude-frequency characteristics of SDOF system with joint was obtained successfully.Secondly,following study of joint nonlinearity,influence of joint nonlinearity on the dynamic characteristics of jointed beam was studied.Formulation of joint mechanics was contrived and expression of joint nonlinear force was derived.Dynamic govern equation of jointed beam was deduced utilizing Lagrangian theory and impact of joint stiffness and damp on the inherent characteristic of jointed beam was studied.Subsequently,with the employment of DOF,effect of joint nonlinearity on the amplitude-frequency characteristic of jointed beam was performed and an experiment data validation followed.Once again,dynamic characteristics of articulated truss was investigated considering join nonlinearity.Equivalent dynamic matrix of truss bay,contributing to investigate trusses characteristics,was prompted to realize the dimensionality reduction of the high dimensional system.In consideration of joint nonlinear characteristics,an interfacial force of bay is modeled and added smoothly into the truss equivalent dynamic equation.Acquaintance of articulated truss transient response characteristic was performed by FEM simulation,which replace joint material property of nonlinear stiffness with nonlinear joint force coefficient.Finally,with the foundation of research on dynamical characteristic of articulated truss considering joint nonlinearity.Synthetical nonlinear ingredient of the joint clearance and friction nonlinear factors,are integrated with nonlinear stiffness to establish multifactor joint mechanics model.The nonlinear force expansion coefficient of the joint was deduced by employing DFM and influence of nonlinear factors on the amplitudefrequency characteristics of the truss structure was discussed.