Study On Vibration Characteristic For Space Truss Structure Of Spacecraft

High speed rotation of the spacecraft institutions will produce the disturbance,which leads to high frequency vibration in the spacecraft structure, as part of thespacecraft of truss structures will be affected, and then will influence the workcapability and pointing precision of the sensitive equipments which connect withtruss structure. The conventional vibration analysis methods exist shortcomings anddeficiencies in mid-and-high-frequency analysis.Therefore, in order to analyze thedynamic characteristics of the vibration from middle to high frequency ranges,vibration of spatial truss structures, in this paper, is studied as wave motion. Atravelling wave dynamics model is established, and based on this model the analysisof power flow is proposed to analyze energy distribution and loss, which willprovide the theoretical basis for controlling vibrations of spacecraft.Firstly, travelling wave model for plane truss structure is established which isbased on the wave equation of the plane beam(Euler-Bernoulli beam). And then,the wave motion expressions are obtained by considering boundary conditions offorce equilibrium, displace continuity and boundary conditions at the edge. Basedon the model, the simulation of dynamic characteristic of the three units and theeight units plane truss structures are made by using the traveling wave method, andthe simulation results are compared with FEM results, and which shows thetraveling wave results are more accurate than the finite element results.Secondly, based on the travelling wave model for plane truss structure andwave equation of the spatial beam, travelling wave model is made for spacetriangular truss structure which is simplified by the NASA experiments space truss,according to this can get the traveling wave solutions of the structure at any pointand frequency. Travelling wave equations of space truss for engineer application aregiven, and the numerical simulation is made to analyze vibration characteristic ofthe space truss under external excitation, and the simulation results shows that thetraveling wave method is suitable for vibration analysis in the whole frequencydomain.Finally, the analysis of power flow in two-and-three-dimensional trusses aremade by using the traveling wave method, and the net power flow at the membercross-sections are get from the wave mode amplitudes using the power matrix, andthe junction power at the junctions is obtained by forming a junction power matrixwhich accounts for each incident and outgoing wave in each member connected tothe junction. And then, expressions for axial, torsional and flexural stiffnesses andassociated power flow are giver, respectively. In addition, the analysis of the influence of the damping to the net and the junction energy loss shows thatimproving the structure damping can increase energy loss.From the analysis and simulation results above, it is found that travelling wavemethod is accurate and effective for space structures, and which is more accuratethan FEM from middle to high frequency ranges. The results with travelling wavemethod can show the propagation characteristics of disturbance for space structuresin the whole frequency ranges. And the analysis of power flow based on travelingwave model can review energy loss. The research results in this paper provide thetheoretical basis for controlling vibrations of spacecraft.