【作者】 田艳；

【导师】 杨斌久；

【作者基本信息】 哈尔滨工业大学 ， 机械工程， 2012， 硕士

【摘要】 航天器工作时，内部高速旋转的机构会产生扰动，这种扰动在航天器中传播将引起航天器结构的中高频振动，作为航天器一部分的桁架结构也会受影响并产生振动，进而会影响与桁架相连的仪器设备的正常工作。在进行振动特性分析时，传统的分析方法在中高频分析存在缺点和不足。本论文以航天器空间桁架结构为研究对象，基于行波方法建立桁架结构的力学模型，分析空间桁架结构的中高频振动，并在已得桁架结构行波模型基础上进行功率流分析，研究桁架结构内能量传播、能量损耗，为桁架结构中高振动控制提供理论基础。首先，以平面梁（欧拉-伯努利梁）的波动方程为基础，考虑桁架结构每个结点的力平衡条件及变形协调条件，建立平面桁架结构的行波动力学模型。分别对平面三单元桁架和平面八单元桁架结构进行数值仿真，将得到的行波解与同种状况下得到的有限元解进行对比分析,结果表明在中高频段行波解比有限元解更精确。其次，以NASA太空试验桁架简化的一字型三角形桁架结构为工程背景，选择空间两跨桁架结构作为研究对象，以空间梁的波动方程为基础建立行波力学模型，据此得到结构任意点任意频率下的行波解。对空间桁架结构进行数值仿真，得到空间桁架结构在外激励下的振动特性，进一步证明行波法更能准确地得到全频域内振动响应最后，以桁架结构行波力学模型为基础，对桁架结构进行功率流分析，在功率流分析中引入波动思想，用波模式表示单元功率流和结点功率流。进一步给出轴向运动、弯曲运动和扭转运动对应的单元功率矩阵。同时分析了阻尼对单元和结点能量损耗影响，结果表明提高结构阻尼可以增大能量损耗。由以上研究和仿真结果可得，行波方法能准确有效地计算空间桁架结构的振动响应，并且在中高频段行波解比有限元解更准确，行波分析法能够在全频域内分析桁架结构的振动特性。对桁架结构行波模型进行功率流分析，研究桁架结构内能量损耗情况。本论文桁架结构行波方法研究为航天器振动控制提供理论基础。更多还原

【Abstract】 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.更多还原